Add Yuzu's file system implementation, will make it compilable later

core/README.md

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+# Assets folder
+
+### !! The file system implementation is copied from Yuzu as the filesystem is believed to be the same betweeen both consoles
+
+dir: /core/
+
+This is where all of the main universal code for emulating the Switch/Switch2 goes.
+

core/fs/bis_factory.cpp

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+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <fmt/format.h>
+#include "common/fs/path_util.h"
+#include "core/file_sys/bis_factory.h"
+#include "core/file_sys/registered_cache.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+
+constexpr u64 NAND_USER_SIZE = 0x680000000;  // 26624 MiB
+constexpr u64 NAND_SYSTEM_SIZE = 0xA0000000; // 2560 MiB
+constexpr u64 NAND_TOTAL_SIZE = 0x747C00000; // 29820 MiB
+
+BISFactory::BISFactory(VirtualDir nand_root_, VirtualDir load_root_, VirtualDir dump_root_)
+    : nand_root(std::move(nand_root_)), load_root(std::move(load_root_)),
+      dump_root(std::move(dump_root_)),
+      sysnand_cache(std::make_unique<RegisteredCache>(
+          GetOrCreateDirectoryRelative(nand_root, "/system/Contents/registered"))),
+      usrnand_cache(std::make_unique<RegisteredCache>(
+          GetOrCreateDirectoryRelative(nand_root, "/user/Contents/registered"))),
+      sysnand_placeholder(std::make_unique<PlaceholderCache>(
+          GetOrCreateDirectoryRelative(nand_root, "/system/Contents/placehld"))),
+      usrnand_placeholder(std::make_unique<PlaceholderCache>(
+          GetOrCreateDirectoryRelative(nand_root, "/user/Contents/placehld"))) {}
+
+BISFactory::~BISFactory() = default;
+
+VirtualDir BISFactory::GetSystemNANDContentDirectory() const {
+    return GetOrCreateDirectoryRelative(nand_root, "/system/Contents");
+}
+
+VirtualDir BISFactory::GetUserNANDContentDirectory() const {
+    return GetOrCreateDirectoryRelative(nand_root, "/user/Contents");
+}
+
+RegisteredCache* BISFactory::GetSystemNANDContents() const {
+    return sysnand_cache.get();
+}
+
+RegisteredCache* BISFactory::GetUserNANDContents() const {
+    return usrnand_cache.get();
+}
+
+PlaceholderCache* BISFactory::GetSystemNANDPlaceholder() const {
+    return sysnand_placeholder.get();
+}
+
+PlaceholderCache* BISFactory::GetUserNANDPlaceholder() const {
+    return usrnand_placeholder.get();
+}
+
+VirtualDir BISFactory::GetModificationLoadRoot(u64 title_id) const {
+    // LayeredFS doesn't work on updates and title id-less homebrew
+    if (title_id == 0 || (title_id & 0xFFF) == 0x800)
+        return nullptr;
+    return GetOrCreateDirectoryRelative(load_root, fmt::format("/{:016X}", title_id));
+}
+
+VirtualDir BISFactory::GetModificationDumpRoot(u64 title_id) const {
+    if (title_id == 0)
+        return nullptr;
+    return GetOrCreateDirectoryRelative(dump_root, fmt::format("/{:016X}", title_id));
+}
+
+VirtualDir BISFactory::OpenPartition(BisPartitionId id) const {
+    switch (id) {
+    case BisPartitionId::CalibrationFile:
+        return GetOrCreateDirectoryRelative(nand_root, "/prodinfof");
+    case BisPartitionId::SafeMode:
+        return GetOrCreateDirectoryRelative(nand_root, "/safe");
+    case BisPartitionId::System:
+        return GetOrCreateDirectoryRelative(nand_root, "/system");
+    case BisPartitionId::User:
+        return GetOrCreateDirectoryRelative(nand_root, "/user");
+    default:
+        return nullptr;
+    }
+}
+
+VirtualFile BISFactory::OpenPartitionStorage(BisPartitionId id,
+                                             VirtualFilesystem file_system) const {
+    auto& keys = Core::Crypto::KeyManager::Instance();
+    Core::Crypto::PartitionDataManager pdm{file_system->OpenDirectory(
+        Common::FS::GetYuzuPathString(Common::FS::YuzuPath::NANDDir), OpenMode::Read)};
+    keys.PopulateFromPartitionData(pdm);
+
+    switch (id) {
+    case BisPartitionId::CalibrationBinary:
+        return pdm.GetDecryptedProdInfo();
+    case BisPartitionId::BootConfigAndPackage2Part1:
+    case BisPartitionId::BootConfigAndPackage2Part2:
+    case BisPartitionId::BootConfigAndPackage2Part3:
+    case BisPartitionId::BootConfigAndPackage2Part4:
+    case BisPartitionId::BootConfigAndPackage2Part5:
+    case BisPartitionId::BootConfigAndPackage2Part6: {
+        const auto new_id = static_cast<u8>(id) -
+                            static_cast<u8>(BisPartitionId::BootConfigAndPackage2Part1) +
+                            static_cast<u8>(Core::Crypto::Package2Type::NormalMain);
+        return pdm.GetPackage2Raw(static_cast<Core::Crypto::Package2Type>(new_id));
+    }
+    default:
+        return nullptr;
+    }
+}
+
+VirtualDir BISFactory::GetImageDirectory() const {
+    return GetOrCreateDirectoryRelative(nand_root, "/user/Album");
+}
+
+u64 BISFactory::GetSystemNANDFreeSpace() const {
+    const auto sys_dir = GetOrCreateDirectoryRelative(nand_root, "/system");
+    if (sys_dir == nullptr) {
+        return GetSystemNANDTotalSpace();
+    }
+
+    return GetSystemNANDTotalSpace() - sys_dir->GetSize();
+}
+
+u64 BISFactory::GetSystemNANDTotalSpace() const {
+    return NAND_SYSTEM_SIZE;
+}
+
+u64 BISFactory::GetUserNANDFreeSpace() const {
+    // For some reason games such as BioShock 1 checks whether this is exactly 0x680000000 bytes.
+    // Set the free space to be 1 MiB less than the total as a workaround to this issue.
+    return GetUserNANDTotalSpace() - 0x100000;
+}
+
+u64 BISFactory::GetUserNANDTotalSpace() const {
+    return NAND_USER_SIZE;
+}
+
+u64 BISFactory::GetFullNANDTotalSpace() const {
+    return NAND_TOTAL_SIZE;
+}
+
+VirtualDir BISFactory::GetBCATDirectory(u64 title_id) const {
+    return GetOrCreateDirectoryRelative(nand_root,
+                                        fmt::format("/system/save/bcat/{:016X}", title_id));
+}
+
+} // namespace FileSys

core/fs/bis_factory.h

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+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <memory>
+
+#include "common/common_types.h"
+#include "core/file_sys/vfs/vfs_types.h"
+
+namespace FileSys {
+
+enum class BisPartitionId : u32 {
+    UserDataRoot = 20,
+    CalibrationBinary = 27,
+    CalibrationFile = 28,
+    BootConfigAndPackage2Part1 = 21,
+    BootConfigAndPackage2Part2 = 22,
+    BootConfigAndPackage2Part3 = 23,
+    BootConfigAndPackage2Part4 = 24,
+    BootConfigAndPackage2Part5 = 25,
+    BootConfigAndPackage2Part6 = 26,
+    SafeMode = 29,
+    System = 31,
+    SystemProperEncryption = 32,
+    SystemProperPartition = 33,
+    User = 30,
+};
+
+class RegisteredCache;
+class PlaceholderCache;
+
+/// File system interface to the Built-In Storage
+/// This is currently missing accessors to BIS partitions, but seemed like a good place for the NAND
+/// registered caches.
+class BISFactory {
+public:
+    explicit BISFactory(VirtualDir nand_root, VirtualDir load_root, VirtualDir dump_root);
+    ~BISFactory();
+
+    VirtualDir GetSystemNANDContentDirectory() const;
+    VirtualDir GetUserNANDContentDirectory() const;
+
+    RegisteredCache* GetSystemNANDContents() const;
+    RegisteredCache* GetUserNANDContents() const;
+
+    PlaceholderCache* GetSystemNANDPlaceholder() const;
+    PlaceholderCache* GetUserNANDPlaceholder() const;
+
+    VirtualDir GetModificationLoadRoot(u64 title_id) const;
+    VirtualDir GetModificationDumpRoot(u64 title_id) const;
+
+    VirtualDir OpenPartition(BisPartitionId id) const;
+    VirtualFile OpenPartitionStorage(BisPartitionId id, VirtualFilesystem file_system) const;
+
+    VirtualDir GetImageDirectory() const;
+
+    u64 GetSystemNANDFreeSpace() const;
+    u64 GetSystemNANDTotalSpace() const;
+    u64 GetUserNANDFreeSpace() const;
+    u64 GetUserNANDTotalSpace() const;
+    u64 GetFullNANDTotalSpace() const;
+
+    VirtualDir GetBCATDirectory(u64 title_id) const;
+
+private:
+    VirtualDir nand_root;
+    VirtualDir load_root;
+    VirtualDir dump_root;
+
+    std::unique_ptr<RegisteredCache> sysnand_cache;
+    std::unique_ptr<RegisteredCache> usrnand_cache;
+
+    std::unique_ptr<PlaceholderCache> sysnand_placeholder;
+    std::unique_ptr<PlaceholderCache> usrnand_placeholder;
+};
+
+} // namespace FileSys

core/fs/card_image.cpp

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+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <array>
+#include <string>
+
+#include <fmt/ostream.h>
+
+#include "common/logging/log.h"
+#include "core/crypto/key_manager.h"
+#include "core/file_sys/card_image.h"
+#include "core/file_sys/content_archive.h"
+#include "core/file_sys/nca_metadata.h"
+#include "core/file_sys/partition_filesystem.h"
+#include "core/file_sys/submission_package.h"
+#include "core/file_sys/vfs/vfs_offset.h"
+#include "core/file_sys/vfs/vfs_vector.h"
+#include "core/loader/loader.h"
+
+namespace FileSys {
+
+constexpr u64 GAMECARD_CERTIFICATE_OFFSET = 0x7000;
+constexpr std::array partition_names{
+    "update",
+    "normal",
+    "secure",
+    "logo",
+};
+
+XCI::XCI(VirtualFile file_, u64 program_id, size_t program_index)
+    : file(std::move(file_)), program_nca_status{Loader::ResultStatus::ErrorXCIMissingProgramNCA},
+      partitions(partition_names.size()),
+      partitions_raw(partition_names.size()), keys{Core::Crypto::KeyManager::Instance()} {
+    const auto header_status = TryReadHeader();
+    if (header_status != Loader::ResultStatus::Success) {
+        status = header_status;
+        return;
+    }
+
+    PartitionFilesystem main_hfs(std::make_shared<OffsetVfsFile>(
+        file, file->GetSize() - header.hfs_offset, header.hfs_offset));
+
+    update_normal_partition_end = main_hfs.GetFileOffsets()["secure"];
+
+    if (main_hfs.GetStatus() != Loader::ResultStatus::Success) {
+        status = main_hfs.GetStatus();
+        return;
+    }
+
+    for (XCIPartition partition :
+         {XCIPartition::Update, XCIPartition::Normal, XCIPartition::Secure, XCIPartition::Logo}) {
+        const auto partition_idx = static_cast<std::size_t>(partition);
+        auto raw = main_hfs.GetFile(partition_names[partition_idx]);
+
+        partitions_raw[static_cast<std::size_t>(partition)] = std::move(raw);
+    }
+
+    secure_partition = std::make_shared<NSP>(
+        main_hfs.GetFile(partition_names[static_cast<std::size_t>(XCIPartition::Secure)]),
+        program_id, program_index);
+
+    ncas = secure_partition->GetNCAsCollapsed();
+    program =
+        secure_partition->GetNCA(secure_partition->GetProgramTitleID(), ContentRecordType::Program);
+    program_nca_status = secure_partition->GetProgramStatus();
+    if (program_nca_status == Loader::ResultStatus::ErrorNSPMissingProgramNCA) {
+        program_nca_status = Loader::ResultStatus::ErrorXCIMissingProgramNCA;
+    }
+
+    auto result = AddNCAFromPartition(XCIPartition::Normal);
+    if (result != Loader::ResultStatus::Success) {
+        status = result;
+        return;
+    }
+
+    if (GetFormatVersion() >= 0x2) {
+        result = AddNCAFromPartition(XCIPartition::Logo);
+        if (result != Loader::ResultStatus::Success) {
+            status = result;
+            return;
+        }
+    }
+
+    status = Loader::ResultStatus::Success;
+}
+
+XCI::~XCI() = default;
+
+Loader::ResultStatus XCI::GetStatus() const {
+    return status;
+}
+
+Loader::ResultStatus XCI::GetProgramNCAStatus() const {
+    return program_nca_status;
+}
+
+VirtualDir XCI::GetPartition(XCIPartition partition) {
+    const auto id = static_cast<std::size_t>(partition);
+    if (partitions[id] == nullptr && partitions_raw[id] != nullptr) {
+        partitions[id] = std::make_shared<PartitionFilesystem>(partitions_raw[id]);
+    }
+
+    return partitions[static_cast<std::size_t>(partition)];
+}
+
+std::vector<VirtualDir> XCI::GetPartitions() {
+    std::vector<VirtualDir> out;
+    for (const auto& id :
+         {XCIPartition::Update, XCIPartition::Normal, XCIPartition::Secure, XCIPartition::Logo}) {
+        const auto part = GetPartition(id);
+        if (part != nullptr) {
+            out.push_back(part);
+        }
+    }
+    return out;
+}
+
+std::shared_ptr<NSP> XCI::GetSecurePartitionNSP() const {
+    return secure_partition;
+}
+
+VirtualDir XCI::GetSecurePartition() {
+    return GetPartition(XCIPartition::Secure);
+}
+
+VirtualDir XCI::GetNormalPartition() {
+    return GetPartition(XCIPartition::Normal);
+}
+
+VirtualDir XCI::GetUpdatePartition() {
+    return GetPartition(XCIPartition::Update);
+}
+
+VirtualDir XCI::GetLogoPartition() {
+    return GetPartition(XCIPartition::Logo);
+}
+
+VirtualFile XCI::GetPartitionRaw(XCIPartition partition) const {
+    return partitions_raw[static_cast<std::size_t>(partition)];
+}
+
+VirtualFile XCI::GetSecurePartitionRaw() const {
+    return GetPartitionRaw(XCIPartition::Secure);
+}
+
+VirtualFile XCI::GetStoragePartition0() const {
+    return std::make_shared<OffsetVfsFile>(file, update_normal_partition_end, 0, "partition0");
+}
+
+VirtualFile XCI::GetStoragePartition1() const {
+    return std::make_shared<OffsetVfsFile>(file, file->GetSize() - update_normal_partition_end,
+                                           update_normal_partition_end, "partition1");
+}
+
+VirtualFile XCI::GetNormalPartitionRaw() const {
+    return GetPartitionRaw(XCIPartition::Normal);
+}
+
+VirtualFile XCI::GetUpdatePartitionRaw() const {
+    return GetPartitionRaw(XCIPartition::Update);
+}
+
+VirtualFile XCI::GetLogoPartitionRaw() const {
+    return GetPartitionRaw(XCIPartition::Logo);
+}
+
+u64 XCI::GetProgramTitleID() const {
+    return secure_partition->GetProgramTitleID();
+}
+
+std::vector<u64> XCI::GetProgramTitleIDs() const {
+    return secure_partition->GetProgramTitleIDs();
+}
+
+u32 XCI::GetSystemUpdateVersion() {
+    const auto update = GetPartition(XCIPartition::Update);
+    if (update == nullptr) {
+        return 0;
+    }
+
+    for (const auto& update_file : update->GetFiles()) {
+        NCA nca{update_file};
+
+        if (nca.GetStatus() != Loader::ResultStatus::Success || nca.GetSubdirectories().empty()) {
+            continue;
+        }
+
+        if (nca.GetType() == NCAContentType::Meta && nca.GetTitleId() == 0x0100000000000816) {
+            const auto dir = nca.GetSubdirectories()[0];
+            const auto cnmt = dir->GetFile("SystemUpdate_0100000000000816.cnmt");
+            if (cnmt == nullptr) {
+                continue;
+            }
+
+            CNMT cnmt_data{cnmt};
+
+            const auto metas = cnmt_data.GetMetaRecords();
+            if (metas.empty()) {
+                continue;
+            }
+
+            return metas[0].title_version;
+        }
+    }
+
+    return 0;
+}
+
+u64 XCI::GetSystemUpdateTitleID() const {
+    return 0x0100000000000816;
+}
+
+bool XCI::HasProgramNCA() const {
+    return program != nullptr;
+}
+
+VirtualFile XCI::GetProgramNCAFile() const {
+    if (!HasProgramNCA()) {
+        return nullptr;
+    }
+
+    return program->GetBaseFile();
+}
+
+const std::vector<std::shared_ptr<NCA>>& XCI::GetNCAs() const {
+    return ncas;
+}
+
+std::shared_ptr<NCA> XCI::GetNCAByType(NCAContentType type) const {
+    const auto program_id = secure_partition->GetProgramTitleID();
+    const auto iter =
+        std::find_if(ncas.begin(), ncas.end(), [type, program_id](const std::shared_ptr<NCA>& nca) {
+            return nca->GetType() == type && nca->GetTitleId() == program_id;
+        });
+    return iter == ncas.end() ? nullptr : *iter;
+}
+
+VirtualFile XCI::GetNCAFileByType(NCAContentType type) const {
+    auto nca = GetNCAByType(type);
+    if (nca != nullptr) {
+        return nca->GetBaseFile();
+    }
+    return nullptr;
+}
+
+std::vector<VirtualFile> XCI::GetFiles() const {
+    return {};
+}
+
+std::vector<VirtualDir> XCI::GetSubdirectories() const {
+    return {};
+}
+
+std::string XCI::GetName() const {
+    return file->GetName();
+}
+
+VirtualDir XCI::GetParentDirectory() const {
+    return file->GetContainingDirectory();
+}
+
+VirtualDir XCI::ConcatenatedPseudoDirectory() {
+    const auto out = std::make_shared<VectorVfsDirectory>();
+    for (const auto& part_id : {XCIPartition::Normal, XCIPartition::Logo, XCIPartition::Secure}) {
+        const auto& part = GetPartition(part_id);
+        if (part == nullptr)
+            continue;
+
+        for (const auto& part_file : part->GetFiles())
+            out->AddFile(part_file);
+    }
+
+    return out;
+}
+
+std::array<u8, 0x200> XCI::GetCertificate() const {
+    std::array<u8, 0x200> out;
+    file->Read(out.data(), out.size(), GAMECARD_CERTIFICATE_OFFSET);
+    return out;
+}
+
+Loader::ResultStatus XCI::AddNCAFromPartition(XCIPartition part) {
+    const auto partition_index = static_cast<std::size_t>(part);
+    const auto partition = GetPartition(part);
+
+    if (partition == nullptr) {
+        return Loader::ResultStatus::ErrorXCIMissingPartition;
+    }
+
+    for (const VirtualFile& partition_file : partition->GetFiles()) {
+        if (partition_file->GetExtension() != "nca") {
+            continue;
+        }
+
+        auto nca = std::make_shared<NCA>(partition_file);
+        if (nca->IsUpdate()) {
+            continue;
+        }
+        if (nca->GetType() == NCAContentType::Program) {
+            program_nca_status = nca->GetStatus();
+        }
+        if (nca->GetStatus() == Loader::ResultStatus::Success) {
+            ncas.push_back(std::move(nca));
+        } else {
+            const u16 error_id = static_cast<u16>(nca->GetStatus());
+            LOG_CRITICAL(Loader, "Could not load NCA {}/{}, failed with error code {:04X} ({})",
+                         partition_names[partition_index], nca->GetName(), error_id,
+                         nca->GetStatus());
+        }
+    }
+
+    return Loader::ResultStatus::Success;
+}
+
+Loader::ResultStatus XCI::TryReadHeader() {
+    constexpr size_t CardInitialDataRegionSize = 0x1000;
+
+    // Define the function we'll use to determine if we read a valid header.
+    const auto ReadCardHeader = [&]() {
+        // Ensure we can read the entire header. If we can't, we can't read the card image.
+        if (file->ReadObject(&header) != sizeof(GamecardHeader)) {
+            return Loader::ResultStatus::ErrorBadXCIHeader;
+        }
+
+        // Ensure the header magic matches. If it doesn't, this isn't a card image header.
+        if (header.magic != Common::MakeMagic('H', 'E', 'A', 'D')) {
+            return Loader::ResultStatus::ErrorBadXCIHeader;
+        }
+
+        // We read a card image header.
+        return Loader::ResultStatus::Success;
+    };
+
+    // Try to read the header directly.
+    if (ReadCardHeader() == Loader::ResultStatus::Success) {
+        return Loader::ResultStatus::Success;
+    }
+
+    // Get the size of the file.
+    const size_t card_image_size = file->GetSize();
+
+    // If we are large enough to have a key area, offset past the key area and retry.
+    if (card_image_size >= CardInitialDataRegionSize) {
+        file = std::make_shared<OffsetVfsFile>(file, card_image_size - CardInitialDataRegionSize,
+                                               CardInitialDataRegionSize);
+        return ReadCardHeader();
+    }
+
+    // We had no header and aren't large enough to have a key area, so this can't be parsed.
+    return Loader::ResultStatus::ErrorBadXCIHeader;
+}
+
+u8 XCI::GetFormatVersion() {
+    return GetLogoPartition() == nullptr ? 0x1 : 0x2;
+}
+} // namespace FileSys

core/fs/card_image.h

@@ -0,0 +1,149 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+#include <memory>
+#include <vector>
+#include "common/common_types.h"
+#include "common/swap.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace Core::Crypto {
+class KeyManager;
+}
+
+namespace Loader {
+enum class ResultStatus : u16;
+}
+
+namespace FileSys {
+
+class NCA;
+enum class NCAContentType : u8;
+class NSP;
+
+enum class GamecardSize : u8 {
+    S_1GB = 0xFA,
+    S_2GB = 0xF8,
+    S_4GB = 0xF0,
+    S_8GB = 0xE0,
+    S_16GB = 0xE1,
+    S_32GB = 0xE2,
+};
+
+struct GamecardInfo {
+    u64_le firmware_version;
+    u32_le access_control_flags;
+    u32_le read_wait_time1;
+    u32_le read_wait_time2;
+    u32_le write_wait_time1;
+    u32_le write_wait_time2;
+    u32_le firmware_mode;
+    u32_le cup_version;
+    std::array<u8, 4> reserved1;
+    u64_le update_partition_hash;
+    u64_le cup_id;
+    std::array<u8, 0x38> reserved2;
+};
+static_assert(sizeof(GamecardInfo) == 0x70, "GamecardInfo has incorrect size.");
+
+struct GamecardHeader {
+    std::array<u8, 0x100> signature;
+    u32_le magic;
+    u32_le secure_area_start;
+    u32_le backup_area_start;
+    u8 kek_index;
+    GamecardSize size;
+    u8 header_version;
+    u8 flags;
+    u64_le package_id;
+    u64_le valid_data_end;
+    u128 info_iv;
+    u64_le hfs_offset;
+    u64_le hfs_size;
+    std::array<u8, 0x20> hfs_header_hash;
+    std::array<u8, 0x20> initial_data_hash;
+    u32_le secure_mode_flag;
+    u32_le title_key_flag;
+    u32_le key_flag;
+    u32_le normal_area_end;
+    GamecardInfo info;
+};
+static_assert(sizeof(GamecardHeader) == 0x200, "GamecardHeader has incorrect size.");
+
+enum class XCIPartition : u8 { Update, Normal, Secure, Logo };
+
+class XCI : public ReadOnlyVfsDirectory {
+public:
+    explicit XCI(VirtualFile file, u64 program_id = 0, size_t program_index = 0);
+    ~XCI() override;
+
+    Loader::ResultStatus GetStatus() const;
+    Loader::ResultStatus GetProgramNCAStatus() const;
+
+    u8 GetFormatVersion();
+
+    VirtualDir GetPartition(XCIPartition partition);
+    std::vector<VirtualDir> GetPartitions();
+
+    std::shared_ptr<NSP> GetSecurePartitionNSP() const;
+    VirtualDir GetSecurePartition();
+    VirtualDir GetNormalPartition();
+    VirtualDir GetUpdatePartition();
+    VirtualDir GetLogoPartition();
+
+    VirtualFile GetPartitionRaw(XCIPartition partition) const;
+    VirtualFile GetSecurePartitionRaw() const;
+    VirtualFile GetStoragePartition0() const;
+    VirtualFile GetStoragePartition1() const;
+    VirtualFile GetNormalPartitionRaw() const;
+    VirtualFile GetUpdatePartitionRaw() const;
+    VirtualFile GetLogoPartitionRaw() const;
+
+    u64 GetProgramTitleID() const;
+    std::vector<u64> GetProgramTitleIDs() const;
+    u32 GetSystemUpdateVersion();
+    u64 GetSystemUpdateTitleID() const;
+
+    bool HasProgramNCA() const;
+    VirtualFile GetProgramNCAFile() const;
+    const std::vector<std::shared_ptr<NCA>>& GetNCAs() const;
+    std::shared_ptr<NCA> GetNCAByType(NCAContentType type) const;
+    VirtualFile GetNCAFileByType(NCAContentType type) const;
+
+    std::vector<VirtualFile> GetFiles() const override;
+
+    std::vector<VirtualDir> GetSubdirectories() const override;
+
+    std::string GetName() const override;
+
+    VirtualDir GetParentDirectory() const override;
+
+    // Creates a directory that contains all the NCAs in the gamecard
+    VirtualDir ConcatenatedPseudoDirectory();
+
+    std::array<u8, 0x200> GetCertificate() const;
+
+private:
+    Loader::ResultStatus AddNCAFromPartition(XCIPartition part);
+    Loader::ResultStatus TryReadHeader();
+
+    VirtualFile file;
+    GamecardHeader header{};
+
+    Loader::ResultStatus status;
+    Loader::ResultStatus program_nca_status;
+
+    std::vector<VirtualDir> partitions;
+    std::vector<VirtualFile> partitions_raw;
+    std::shared_ptr<NSP> secure_partition;
+    std::shared_ptr<NCA> program;
+    std::vector<std::shared_ptr<NCA>> ncas;
+
+    u64 update_normal_partition_end;
+
+    Core::Crypto::KeyManager& keys;
+};
+} // namespace FileSys

core/fs/common_funcs.h

@@ -0,0 +1,55 @@
+// SPDX-FileCopyrightText: Copyright 2020 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_types.h"
+
+namespace FileSys {
+
+constexpr u64 AOC_TITLE_ID_MASK = 0x7FF;
+constexpr u64 AOC_TITLE_ID_OFFSET = 0x1000;
+constexpr u64 BASE_TITLE_ID_MASK = 0xFFFFFFFFFFFFE000;
+
+/**
+ * Gets the base title ID from a given title ID.
+ *
+ * @param title_id The title ID.
+ * @returns The base title ID.
+ */
+[[nodiscard]] constexpr u64 GetBaseTitleID(u64 title_id) {
+    return title_id & BASE_TITLE_ID_MASK;
+}
+
+/**
+ * Gets the base title ID with a program index offset from a given title ID.
+ *
+ * @param title_id The title ID.
+ * @param program_index The program index.
+ * @returns The base title ID with a program index offset.
+ */
+[[nodiscard]] constexpr u64 GetBaseTitleIDWithProgramIndex(u64 title_id, u64 program_index) {
+    return GetBaseTitleID(title_id) + program_index;
+}
+
+/**
+ * Gets the AOC (Add-On Content) base title ID from a given title ID.
+ *
+ * @param title_id The title ID.
+ * @returns The AOC base title ID.
+ */
+[[nodiscard]] constexpr u64 GetAOCBaseTitleID(u64 title_id) {
+    return GetBaseTitleID(title_id) + AOC_TITLE_ID_OFFSET;
+}
+
+/**
+ * Gets the AOC (Add-On Content) ID from a given AOC title ID.
+ *
+ * @param aoc_title_id The AOC title ID.
+ * @returns The AOC ID.
+ */
+[[nodiscard]] constexpr u64 GetAOCID(u64 aoc_title_id) {
+    return aoc_title_id & AOC_TITLE_ID_MASK;
+}
+
+} // namespace FileSys

core/fs/content_archive.cpp

@@ -0,0 +1,199 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <algorithm>
+#include <cstring>
+#include <optional>
+#include <utility>
+
+#include "common/logging/log.h"
+#include "common/polyfill_ranges.h"
+#include "core/crypto/aes_util.h"
+#include "core/crypto/ctr_encryption_layer.h"
+#include "core/crypto/key_manager.h"
+#include "core/file_sys/content_archive.h"
+#include "core/file_sys/partition_filesystem.h"
+#include "core/file_sys/vfs/vfs_offset.h"
+#include "core/loader/loader.h"
+
+#include "core/file_sys/fssystem/fssystem_compression_configuration.h"
+#include "core/file_sys/fssystem/fssystem_crypto_configuration.h"
+#include "core/file_sys/fssystem/fssystem_nca_file_system_driver.h"
+
+namespace FileSys {
+
+static u8 MasterKeyIdForKeyGeneration(u8 key_generation) {
+    return std::max<u8>(key_generation, 1) - 1;
+}
+
+NCA::NCA(VirtualFile file_, const NCA* base_nca)
+    : file(std::move(file_)), keys{Core::Crypto::KeyManager::Instance()} {
+    if (file == nullptr) {
+        status = Loader::ResultStatus::ErrorNullFile;
+        return;
+    }
+
+    reader = std::make_shared<NcaReader>();
+    if (Result rc =
+            reader->Initialize(file, GetCryptoConfiguration(), GetNcaCompressionConfiguration());
+        R_FAILED(rc)) {
+        if (rc != ResultInvalidNcaSignature) {
+            LOG_ERROR(Loader, "File reader errored out during header read: {:#x}",
+                      rc.GetInnerValue());
+        }
+        status = Loader::ResultStatus::ErrorBadNCAHeader;
+        return;
+    }
+
+    // Ensure we have the proper key area keys to continue.
+    const u8 master_key_id = MasterKeyIdForKeyGeneration(reader->GetKeyGeneration());
+    if (!keys.HasKey(Core::Crypto::S128KeyType::KeyArea, master_key_id, reader->GetKeyIndex())) {
+        status = Loader::ResultStatus::ErrorMissingKeyAreaKey;
+        return;
+    }
+
+    RightsId rights_id{};
+    reader->GetRightsId(rights_id.data(), rights_id.size());
+    if (rights_id != RightsId{}) {
+        // External decryption key required; provide it here.
+        u128 rights_id_u128;
+        std::memcpy(rights_id_u128.data(), rights_id.data(), sizeof(rights_id));
+
+        auto titlekey =
+            keys.GetKey(Core::Crypto::S128KeyType::Titlekey, rights_id_u128[1], rights_id_u128[0]);
+        if (titlekey == Core::Crypto::Key128{}) {
+            status = Loader::ResultStatus::ErrorMissingTitlekey;
+            return;
+        }
+
+        if (!keys.HasKey(Core::Crypto::S128KeyType::Titlekek, master_key_id)) {
+            status = Loader::ResultStatus::ErrorMissingTitlekek;
+            return;
+        }
+
+        auto titlekek = keys.GetKey(Core::Crypto::S128KeyType::Titlekek, master_key_id);
+        Core::Crypto::AESCipher<Core::Crypto::Key128> cipher(titlekek, Core::Crypto::Mode::ECB);
+        cipher.Transcode(titlekey.data(), titlekey.size(), titlekey.data(),
+                         Core::Crypto::Op::Decrypt);
+
+        reader->SetExternalDecryptionKey(titlekey.data(), titlekey.size());
+    }
+
+    const s32 fs_count = reader->GetFsCount();
+    NcaFileSystemDriver fs(base_nca ? base_nca->reader : nullptr, reader);
+    std::vector<VirtualFile> filesystems(fs_count);
+    for (s32 i = 0; i < fs_count; i++) {
+        NcaFsHeaderReader header_reader;
+        const Result rc = fs.OpenStorage(&filesystems[i], &header_reader, i);
+        if (R_FAILED(rc)) {
+            LOG_ERROR(Loader, "File reader errored out during read of section {}: {:#x}", i,
+                      rc.GetInnerValue());
+            status = Loader::ResultStatus::ErrorBadNCAHeader;
+            return;
+        }
+
+        if (header_reader.GetFsType() == NcaFsHeader::FsType::RomFs) {
+            files.push_back(filesystems[i]);
+            romfs = files.back();
+        }
+
+        if (header_reader.GetFsType() == NcaFsHeader::FsType::PartitionFs) {
+            auto npfs = std::make_shared<PartitionFilesystem>(filesystems[i]);
+            if (npfs->GetStatus() == Loader::ResultStatus::Success) {
+                dirs.push_back(npfs);
+                if (IsDirectoryExeFS(npfs)) {
+                    exefs = dirs.back();
+                } else if (IsDirectoryLogoPartition(npfs)) {
+                    logo = dirs.back();
+                } else {
+                    continue;
+                }
+            }
+        }
+
+        if (header_reader.GetEncryptionType() == NcaFsHeader::EncryptionType::AesCtrEx) {
+            is_update = true;
+        }
+    }
+
+    if (is_update && base_nca == nullptr) {
+        status = Loader::ResultStatus::ErrorMissingBKTRBaseRomFS;
+    } else {
+        status = Loader::ResultStatus::Success;
+    }
+}
+
+NCA::~NCA() = default;
+
+Loader::ResultStatus NCA::GetStatus() const {
+    return status;
+}
+
+std::vector<VirtualFile> NCA::GetFiles() const {
+    if (status != Loader::ResultStatus::Success) {
+        return {};
+    }
+    return files;
+}
+
+std::vector<VirtualDir> NCA::GetSubdirectories() const {
+    if (status != Loader::ResultStatus::Success) {
+        return {};
+    }
+    return dirs;
+}
+
+std::string NCA::GetName() const {
+    return file->GetName();
+}
+
+VirtualDir NCA::GetParentDirectory() const {
+    return file->GetContainingDirectory();
+}
+
+NCAContentType NCA::GetType() const {
+    return static_cast<NCAContentType>(reader->GetContentType());
+}
+
+u64 NCA::GetTitleId() const {
+    if (is_update) {
+        return reader->GetProgramId() | 0x800;
+    }
+    return reader->GetProgramId();
+}
+
+RightsId NCA::GetRightsId() const {
+    RightsId result;
+    reader->GetRightsId(result.data(), result.size());
+    return result;
+}
+
+u32 NCA::GetSDKVersion() const {
+    return reader->GetSdkAddonVersion();
+}
+
+u8 NCA::GetKeyGeneration() const {
+    return reader->GetKeyGeneration();
+}
+
+bool NCA::IsUpdate() const {
+    return is_update;
+}
+
+VirtualFile NCA::GetRomFS() const {
+    return romfs;
+}
+
+VirtualDir NCA::GetExeFS() const {
+    return exefs;
+}
+
+VirtualFile NCA::GetBaseFile() const {
+    return file;
+}
+
+VirtualDir NCA::GetLogoPartition() const {
+    return logo;
+}
+
+} // namespace FileSys

core/fs/content_archive.h

@@ -0,0 +1,108 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+#include <memory>
+#include <optional>
+#include <string>
+#include <vector>
+
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+#include "common/swap.h"
+#include "core/crypto/key_manager.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace Loader {
+enum class ResultStatus : u16;
+}
+
+namespace FileSys {
+
+class NcaReader;
+
+/// Describes the type of content within an NCA archive.
+enum class NCAContentType : u8 {
+    /// Executable-related data
+    Program = 0,
+
+    /// Metadata.
+    Meta = 1,
+
+    /// Access control data.
+    Control = 2,
+
+    /// Information related to the game manual
+    /// e.g. Legal information, etc.
+    Manual = 3,
+
+    /// System data.
+    Data = 4,
+
+    /// Data that can be accessed by applications.
+    PublicData = 5,
+};
+
+using RightsId = std::array<u8, 0x10>;
+
+inline bool IsDirectoryExeFS(const VirtualDir& pfs) {
+    // According to switchbrew, an exefs must only contain these two files:
+    return pfs->GetFile("main") != nullptr && pfs->GetFile("main.npdm") != nullptr;
+}
+
+inline bool IsDirectoryLogoPartition(const VirtualDir& pfs) {
+    // NintendoLogo is the static image in the top left corner while StartupMovie is the animation
+    // in the bottom right corner.
+    return pfs->GetFile("NintendoLogo.png") != nullptr &&
+           pfs->GetFile("StartupMovie.gif") != nullptr;
+}
+
+// An implementation of VfsDirectory that represents a Nintendo Content Archive (NCA) container.
+// After construction, use GetStatus to determine if the file is valid and ready to be used.
+class NCA : public ReadOnlyVfsDirectory {
+public:
+    explicit NCA(VirtualFile file, const NCA* base_nca = nullptr);
+    ~NCA() override;
+
+    Loader::ResultStatus GetStatus() const;
+
+    std::vector<VirtualFile> GetFiles() const override;
+    std::vector<VirtualDir> GetSubdirectories() const override;
+    std::string GetName() const override;
+    VirtualDir GetParentDirectory() const override;
+
+    NCAContentType GetType() const;
+    u64 GetTitleId() const;
+    RightsId GetRightsId() const;
+    u32 GetSDKVersion() const;
+    u8 GetKeyGeneration() const;
+    bool IsUpdate() const;
+
+    VirtualFile GetRomFS() const;
+    VirtualDir GetExeFS() const;
+
+    VirtualFile GetBaseFile() const;
+
+    VirtualDir GetLogoPartition() const;
+
+private:
+    std::vector<VirtualDir> dirs;
+    std::vector<VirtualFile> files;
+
+    VirtualFile romfs = nullptr;
+    VirtualDir exefs = nullptr;
+    VirtualDir logo = nullptr;
+    VirtualFile file;
+
+    Loader::ResultStatus status{};
+
+    bool encrypted = false;
+    bool is_update = false;
+
+    Core::Crypto::KeyManager& keys;
+    std::shared_ptr<NcaReader> reader;
+};
+
+} // namespace FileSys

core/fs/control_metadata.cpp

@@ -0,0 +1,142 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/settings.h"
+#include "common/string_util.h"
+#include "common/swap.h"
+#include "core/file_sys/control_metadata.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+
+const std::array<const char*, 16> LANGUAGE_NAMES{{
+    "AmericanEnglish",
+    "BritishEnglish",
+    "Japanese",
+    "French",
+    "German",
+    "LatinAmericanSpanish",
+    "Spanish",
+    "Italian",
+    "Dutch",
+    "CanadianFrench",
+    "Portuguese",
+    "Russian",
+    "Korean",
+    "TraditionalChinese",
+    "SimplifiedChinese",
+    "BrazilianPortuguese",
+}};
+
+std::string LanguageEntry::GetApplicationName() const {
+    return Common::StringFromFixedZeroTerminatedBuffer(application_name.data(),
+                                                       application_name.size());
+}
+
+std::string LanguageEntry::GetDeveloperName() const {
+    return Common::StringFromFixedZeroTerminatedBuffer(developer_name.data(),
+                                                       developer_name.size());
+}
+
+constexpr std::array<Language, 18> language_to_codes = {{
+    Language::Japanese,
+    Language::AmericanEnglish,
+    Language::French,
+    Language::German,
+    Language::Italian,
+    Language::Spanish,
+    Language::SimplifiedChinese,
+    Language::Korean,
+    Language::Dutch,
+    Language::Portuguese,
+    Language::Russian,
+    Language::TraditionalChinese,
+    Language::BritishEnglish,
+    Language::CanadianFrench,
+    Language::LatinAmericanSpanish,
+    Language::SimplifiedChinese,
+    Language::TraditionalChinese,
+    Language::BrazilianPortuguese,
+}};
+
+NACP::NACP() = default;
+
+NACP::NACP(VirtualFile file) {
+    file->ReadObject(&raw);
+}
+
+NACP::~NACP() = default;
+
+const LanguageEntry& NACP::GetLanguageEntry() const {
+    Language language =
+        language_to_codes[static_cast<s32>(Settings::values.language_index.GetValue())];
+
+    {
+        const auto& language_entry = raw.language_entries.at(static_cast<u8>(language));
+        if (!language_entry.GetApplicationName().empty())
+            return language_entry;
+    }
+
+    for (const auto& language_entry : raw.language_entries) {
+        if (!language_entry.GetApplicationName().empty())
+            return language_entry;
+    }
+
+    return raw.language_entries.at(static_cast<u8>(Language::AmericanEnglish));
+}
+
+std::string NACP::GetApplicationName() const {
+    return GetLanguageEntry().GetApplicationName();
+}
+
+std::string NACP::GetDeveloperName() const {
+    return GetLanguageEntry().GetDeveloperName();
+}
+
+u64 NACP::GetTitleId() const {
+    return raw.save_data_owner_id;
+}
+
+u64 NACP::GetDLCBaseTitleId() const {
+    return raw.dlc_base_title_id;
+}
+
+std::string NACP::GetVersionString() const {
+    return Common::StringFromFixedZeroTerminatedBuffer(raw.version_string.data(),
+                                                       raw.version_string.size());
+}
+
+u64 NACP::GetDefaultNormalSaveSize() const {
+    return raw.user_account_save_data_size;
+}
+
+u64 NACP::GetDefaultJournalSaveSize() const {
+    return raw.user_account_save_data_journal_size;
+}
+
+bool NACP::GetUserAccountSwitchLock() const {
+    return raw.user_account_switch_lock != 0;
+}
+
+u32 NACP::GetSupportedLanguages() const {
+    return raw.supported_languages;
+}
+
+u64 NACP::GetDeviceSaveDataSize() const {
+    return raw.device_save_data_size;
+}
+
+u32 NACP::GetParentalControlFlag() const {
+    return raw.parental_control;
+}
+
+const std::array<u8, 0x20>& NACP::GetRatingAge() const {
+    return raw.rating_age;
+}
+
+std::vector<u8> NACP::GetRawBytes() const {
+    std::vector<u8> out(sizeof(RawNACP));
+    std::memcpy(out.data(), &raw, sizeof(RawNACP));
+    return out;
+}
+} // namespace FileSys

core/fs/control_metadata.h

@@ -0,0 +1,123 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+#include <string>
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+#include "common/swap.h"
+#include "core/file_sys/vfs/vfs_types.h"
+
+namespace FileSys {
+
+// A localized entry containing strings within the NACP.
+// One for each language of type Language.
+struct LanguageEntry {
+    std::array<char, 0x200> application_name;
+    std::array<char, 0x100> developer_name;
+
+    std::string GetApplicationName() const;
+    std::string GetDeveloperName() const;
+};
+static_assert(sizeof(LanguageEntry) == 0x300, "LanguageEntry has incorrect size.");
+
+// The raw file format of a NACP file.
+struct RawNACP {
+    std::array<LanguageEntry, 16> language_entries;
+    std::array<u8, 0x25> isbn;
+    u8 startup_user_account;
+    u8 user_account_switch_lock;
+    u8 addon_content_registration_type;
+    u32_le application_attribute;
+    u32_le supported_languages;
+    u32_le parental_control;
+    bool screenshot_enabled;
+    u8 video_capture_mode;
+    bool data_loss_confirmation;
+    INSERT_PADDING_BYTES(1);
+    u64_le presence_group_id;
+    std::array<u8, 0x20> rating_age;
+    std::array<char, 0x10> version_string;
+    u64_le dlc_base_title_id;
+    u64_le save_data_owner_id;
+    u64_le user_account_save_data_size;
+    u64_le user_account_save_data_journal_size;
+    u64_le device_save_data_size;
+    u64_le device_save_data_journal_size;
+    u64_le bcat_delivery_cache_storage_size;
+    char application_error_code_category[8];
+    std::array<u64_le, 0x8> local_communication;
+    u8 logo_type;
+    u8 logo_handling;
+    bool runtime_add_on_content_install;
+    INSERT_PADDING_BYTES(5);
+    u64_le seed_for_pseudo_device_id;
+    std::array<u8, 0x41> bcat_passphrase;
+    INSERT_PADDING_BYTES(7);
+    u64_le user_account_save_data_max_size;
+    u64_le user_account_save_data_max_journal_size;
+    u64_le device_save_data_max_size;
+    u64_le device_save_data_max_journal_size;
+    u64_le temporary_storage_size;
+    u64_le cache_storage_size;
+    u64_le cache_storage_journal_size;
+    u64_le cache_storage_data_and_journal_max_size;
+    u16_le cache_storage_max_index;
+    INSERT_PADDING_BYTES(0xE76);
+};
+static_assert(sizeof(RawNACP) == 0x4000, "RawNACP has incorrect size.");
+
+// A language on the NX. These are for names and icons.
+enum class Language : u8 {
+    AmericanEnglish = 0,
+    BritishEnglish = 1,
+    Japanese = 2,
+    French = 3,
+    German = 4,
+    LatinAmericanSpanish = 5,
+    Spanish = 6,
+    Italian = 7,
+    Dutch = 8,
+    CanadianFrench = 9,
+    Portuguese = 10,
+    Russian = 11,
+    Korean = 12,
+    TraditionalChinese = 13,
+    SimplifiedChinese = 14,
+    BrazilianPortuguese = 15,
+
+    Default = 255,
+};
+
+extern const std::array<const char*, 16> LANGUAGE_NAMES;
+
+// A class representing the format used by NX metadata files, typically named Control.nacp.
+// These store application name, dev name, title id, and other miscellaneous data.
+class NACP {
+public:
+    explicit NACP();
+    explicit NACP(VirtualFile file);
+    ~NACP();
+
+    const LanguageEntry& GetLanguageEntry() const;
+    std::string GetApplicationName() const;
+    std::string GetDeveloperName() const;
+    u64 GetTitleId() const;
+    u64 GetDLCBaseTitleId() const;
+    std::string GetVersionString() const;
+    u64 GetDefaultNormalSaveSize() const;
+    u64 GetDefaultJournalSaveSize() const;
+    u32 GetSupportedLanguages() const;
+    std::vector<u8> GetRawBytes() const;
+    bool GetUserAccountSwitchLock() const;
+    u64 GetDeviceSaveDataSize() const;
+    u32 GetParentalControlFlag() const;
+    const std::array<u8, 0x20>& GetRatingAge() const;
+
+private:
+    RawNACP raw{};
+};
+
+} // namespace FileSys

core/fs/errors.h

@@ -0,0 +1,97 @@
+// SPDX-FileCopyrightText: 2016 Citra Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/hle/result.h"
+
+namespace FileSys {
+
+constexpr Result ResultPathNotFound{ErrorModule::FS, 1};
+constexpr Result ResultPathAlreadyExists{ErrorModule::FS, 2};
+constexpr Result ResultUnsupportedSdkVersion{ErrorModule::FS, 50};
+constexpr Result ResultPartitionNotFound{ErrorModule::FS, 1001};
+constexpr Result ResultTargetNotFound{ErrorModule::FS, 1002};
+constexpr Result ResultPortSdCardNoDevice{ErrorModule::FS, 2001};
+constexpr Result ResultNotImplemented{ErrorModule::FS, 3001};
+constexpr Result ResultUnsupportedVersion{ErrorModule::FS, 3002};
+constexpr Result ResultOutOfRange{ErrorModule::FS, 3005};
+constexpr Result ResultAllocationMemoryFailedInFileSystemBuddyHeapA{ErrorModule::FS, 3294};
+constexpr Result ResultAllocationMemoryFailedInNcaFileSystemDriverI{ErrorModule::FS, 3341};
+constexpr Result ResultAllocationMemoryFailedInNcaReaderA{ErrorModule::FS, 3363};
+constexpr Result ResultAllocationMemoryFailedInAesCtrCounterExtendedStorageA{ErrorModule::FS, 3399};
+constexpr Result ResultAllocationMemoryFailedInIntegrityRomFsStorageA{ErrorModule::FS, 3412};
+constexpr Result ResultAllocationMemoryFailedMakeUnique{ErrorModule::FS, 3422};
+constexpr Result ResultAllocationMemoryFailedAllocateShared{ErrorModule::FS, 3423};
+constexpr Result ResultInvalidAesCtrCounterExtendedEntryOffset{ErrorModule::FS, 4012};
+constexpr Result ResultIndirectStorageCorrupted{ErrorModule::FS, 4021};
+constexpr Result ResultInvalidIndirectEntryOffset{ErrorModule::FS, 4022};
+constexpr Result ResultInvalidIndirectEntryStorageIndex{ErrorModule::FS, 4023};
+constexpr Result ResultInvalidIndirectStorageSize{ErrorModule::FS, 4024};
+constexpr Result ResultInvalidBucketTreeSignature{ErrorModule::FS, 4032};
+constexpr Result ResultInvalidBucketTreeEntryCount{ErrorModule::FS, 4033};
+constexpr Result ResultInvalidBucketTreeNodeEntryCount{ErrorModule::FS, 4034};
+constexpr Result ResultInvalidBucketTreeNodeOffset{ErrorModule::FS, 4035};
+constexpr Result ResultInvalidBucketTreeEntryOffset{ErrorModule::FS, 4036};
+constexpr Result ResultInvalidBucketTreeEntrySetOffset{ErrorModule::FS, 4037};
+constexpr Result ResultInvalidBucketTreeNodeIndex{ErrorModule::FS, 4038};
+constexpr Result ResultInvalidBucketTreeVirtualOffset{ErrorModule::FS, 4039};
+constexpr Result ResultRomNcaInvalidPatchMetaDataHashType{ErrorModule::FS, 4084};
+constexpr Result ResultRomNcaInvalidIntegrityLayerInfoOffset{ErrorModule::FS, 4085};
+constexpr Result ResultRomNcaInvalidPatchMetaDataHashDataSize{ErrorModule::FS, 4086};
+constexpr Result ResultRomNcaInvalidPatchMetaDataHashDataOffset{ErrorModule::FS, 4087};
+constexpr Result ResultRomNcaInvalidPatchMetaDataHashDataHash{ErrorModule::FS, 4088};
+constexpr Result ResultRomNcaInvalidSparseMetaDataHashType{ErrorModule::FS, 4089};
+constexpr Result ResultRomNcaInvalidSparseMetaDataHashDataSize{ErrorModule::FS, 4090};
+constexpr Result ResultRomNcaInvalidSparseMetaDataHashDataOffset{ErrorModule::FS, 4091};
+constexpr Result ResultRomNcaInvalidSparseMetaDataHashDataHash{ErrorModule::FS, 4091};
+constexpr Result ResultNcaBaseStorageOutOfRangeB{ErrorModule::FS, 4509};
+constexpr Result ResultNcaBaseStorageOutOfRangeC{ErrorModule::FS, 4510};
+constexpr Result ResultNcaBaseStorageOutOfRangeD{ErrorModule::FS, 4511};
+constexpr Result ResultInvalidNcaSignature{ErrorModule::FS, 4517};
+constexpr Result ResultNcaFsHeaderHashVerificationFailed{ErrorModule::FS, 4520};
+constexpr Result ResultInvalidNcaKeyIndex{ErrorModule::FS, 4521};
+constexpr Result ResultInvalidNcaFsHeaderHashType{ErrorModule::FS, 4522};
+constexpr Result ResultInvalidNcaFsHeaderEncryptionType{ErrorModule::FS, 4523};
+constexpr Result ResultInvalidNcaPatchInfoIndirectSize{ErrorModule::FS, 4524};
+constexpr Result ResultInvalidNcaPatchInfoAesCtrExSize{ErrorModule::FS, 4525};
+constexpr Result ResultInvalidNcaPatchInfoAesCtrExOffset{ErrorModule::FS, 4526};
+constexpr Result ResultInvalidNcaHeader{ErrorModule::FS, 4528};
+constexpr Result ResultInvalidNcaFsHeader{ErrorModule::FS, 4529};
+constexpr Result ResultNcaBaseStorageOutOfRangeE{ErrorModule::FS, 4530};
+constexpr Result ResultInvalidHierarchicalSha256BlockSize{ErrorModule::FS, 4532};
+constexpr Result ResultInvalidHierarchicalSha256LayerCount{ErrorModule::FS, 4533};
+constexpr Result ResultHierarchicalSha256BaseStorageTooLarge{ErrorModule::FS, 4534};
+constexpr Result ResultHierarchicalSha256HashVerificationFailed{ErrorModule::FS, 4535};
+constexpr Result ResultInvalidNcaHierarchicalIntegrityVerificationLayerCount{ErrorModule::FS, 4541};
+constexpr Result ResultInvalidNcaIndirectStorageOutOfRange{ErrorModule::FS, 4542};
+constexpr Result ResultInvalidNcaHeader1SignatureKeyGeneration{ErrorModule::FS, 4543};
+constexpr Result ResultInvalidCompressedStorageSize{ErrorModule::FS, 4547};
+constexpr Result ResultInvalidNcaMetaDataHashDataSize{ErrorModule::FS, 4548};
+constexpr Result ResultInvalidNcaMetaDataHashDataHash{ErrorModule::FS, 4549};
+constexpr Result ResultUnexpectedInCompressedStorageA{ErrorModule::FS, 5324};
+constexpr Result ResultUnexpectedInCompressedStorageB{ErrorModule::FS, 5325};
+constexpr Result ResultUnexpectedInCompressedStorageC{ErrorModule::FS, 5326};
+constexpr Result ResultUnexpectedInCompressedStorageD{ErrorModule::FS, 5327};
+constexpr Result ResultUnexpectedInPathA{ErrorModule::FS, 5328};
+constexpr Result ResultInvalidArgument{ErrorModule::FS, 6001};
+constexpr Result ResultInvalidPath{ErrorModule::FS, 6002};
+constexpr Result ResultTooLongPath{ErrorModule::FS, 6003};
+constexpr Result ResultInvalidCharacter{ErrorModule::FS, 6004};
+constexpr Result ResultInvalidPathFormat{ErrorModule::FS, 6005};
+constexpr Result ResultDirectoryUnobtainable{ErrorModule::FS, 6006};
+constexpr Result ResultNotNormalized{ErrorModule::FS, 6007};
+constexpr Result ResultInvalidOffset{ErrorModule::FS, 6061};
+constexpr Result ResultInvalidSize{ErrorModule::FS, 6062};
+constexpr Result ResultNullptrArgument{ErrorModule::FS, 6063};
+constexpr Result ResultInvalidOpenMode{ErrorModule::FS, 6072};
+constexpr Result ResultFileExtensionWithoutOpenModeAllowAppend{ErrorModule::FS, 6201};
+constexpr Result ResultReadNotPermitted{ErrorModule::FS, 6202};
+constexpr Result ResultWriteNotPermitted{ErrorModule::FS, 6203};
+constexpr Result ResultUnsupportedSetSizeForIndirectStorage{ErrorModule::FS, 6325};
+constexpr Result ResultUnsupportedWriteForCompressedStorage{ErrorModule::FS, 6387};
+constexpr Result ResultUnsupportedOperateRangeForCompressedStorage{ErrorModule::FS, 6388};
+constexpr Result ResultPermissionDenied{ErrorModule::FS, 6400};
+constexpr Result ResultBufferAllocationFailed{ErrorModule::FS, 6705};
+
+} // namespace FileSys

core/fs/fs_directory.h

@@ -0,0 +1,37 @@
+// SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <string_view>
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+
+namespace FileSys {
+
+constexpr inline size_t EntryNameLengthMax = 0x300;
+
+struct DirectoryEntry {
+    DirectoryEntry(std::string_view view, s8 entry_type, u64 entry_size)
+        : type{entry_type}, file_size{static_cast<s64>(entry_size)} {
+        const std::size_t copy_size = view.copy(name, std::size(name) - 1);
+        name[copy_size] = '\0';
+    }
+
+    char name[EntryNameLengthMax + 1];
+    INSERT_PADDING_BYTES(3);
+    s8 type;
+    INSERT_PADDING_BYTES(3);
+    s64 file_size;
+};
+
+static_assert(sizeof(DirectoryEntry) == 0x310,
+              "Directory Entry struct isn't exactly 0x310 bytes long!");
+static_assert(offsetof(DirectoryEntry, type) == 0x304, "Wrong offset for type in Entry.");
+static_assert(offsetof(DirectoryEntry, file_size) == 0x308, "Wrong offset for file_size in Entry.");
+
+struct DirectoryHandle {
+    void* handle;
+};
+
+} // namespace FileSys

core/fs/fs_file.h

@@ -0,0 +1,65 @@
+// SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_types.h"
+
+namespace FileSys {
+
+struct ReadOption {
+    u32 value;
+
+    static const ReadOption None;
+};
+
+enum ReadOptionFlag : u32 {
+    ReadOptionFlag_None = (0 << 0),
+};
+
+inline constexpr const ReadOption ReadOption::None = {ReadOptionFlag_None};
+
+inline constexpr bool operator==(const ReadOption& lhs, const ReadOption& rhs) {
+    return lhs.value == rhs.value;
+}
+
+inline constexpr bool operator!=(const ReadOption& lhs, const ReadOption& rhs) {
+    return !(lhs == rhs);
+}
+
+static_assert(sizeof(ReadOption) == sizeof(u32));
+
+enum WriteOptionFlag : u32 {
+    WriteOptionFlag_None = (0 << 0),
+    WriteOptionFlag_Flush = (1 << 0),
+};
+
+struct WriteOption {
+    u32 value;
+
+    constexpr inline bool HasFlushFlag() const {
+        return value & WriteOptionFlag_Flush;
+    }
+
+    static const WriteOption None;
+    static const WriteOption Flush;
+};
+
+inline constexpr const WriteOption WriteOption::None = {WriteOptionFlag_None};
+inline constexpr const WriteOption WriteOption::Flush = {WriteOptionFlag_Flush};
+
+inline constexpr bool operator==(const WriteOption& lhs, const WriteOption& rhs) {
+    return lhs.value == rhs.value;
+}
+
+inline constexpr bool operator!=(const WriteOption& lhs, const WriteOption& rhs) {
+    return !(lhs == rhs);
+}
+
+static_assert(sizeof(WriteOption) == sizeof(u32));
+
+struct FileHandle {
+    void* handle;
+};
+
+} // namespace FileSys

core/fs/fs_filesystem.h

@@ -0,0 +1,66 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+
+namespace FileSys {
+
+enum class OpenMode : u32 {
+    Read = (1 << 0),
+    Write = (1 << 1),
+    AllowAppend = (1 << 2),
+
+    ReadWrite = (Read | Write),
+    All = (ReadWrite | AllowAppend),
+};
+DECLARE_ENUM_FLAG_OPERATORS(OpenMode)
+
+enum class OpenDirectoryMode : u64 {
+    Directory = (1 << 0),
+    File = (1 << 1),
+
+    All = (Directory | File),
+
+    NotRequireFileSize = (1ULL << 31),
+};
+DECLARE_ENUM_FLAG_OPERATORS(OpenDirectoryMode)
+
+enum class DirectoryEntryType : u8 {
+    Directory = 0,
+    File = 1,
+};
+
+enum class CreateOption : u8 {
+    None = (0 << 0),
+    BigFile = (1 << 0),
+};
+
+struct FileSystemAttribute {
+    u8 dir_entry_name_length_max_defined;
+    u8 file_entry_name_length_max_defined;
+    u8 dir_path_name_length_max_defined;
+    u8 file_path_name_length_max_defined;
+    INSERT_PADDING_BYTES_NOINIT(0x5);
+    u8 utf16_dir_entry_name_length_max_defined;
+    u8 utf16_file_entry_name_length_max_defined;
+    u8 utf16_dir_path_name_length_max_defined;
+    u8 utf16_file_path_name_length_max_defined;
+    INSERT_PADDING_BYTES_NOINIT(0x18);
+    s32 dir_entry_name_length_max;
+    s32 file_entry_name_length_max;
+    s32 dir_path_name_length_max;
+    s32 file_path_name_length_max;
+    INSERT_PADDING_WORDS_NOINIT(0x5);
+    s32 utf16_dir_entry_name_length_max;
+    s32 utf16_file_entry_name_length_max;
+    s32 utf16_dir_path_name_length_max;
+    s32 utf16_file_path_name_length_max;
+    INSERT_PADDING_WORDS_NOINIT(0x18);
+    INSERT_PADDING_WORDS_NOINIT(0x1);
+};
+static_assert(sizeof(FileSystemAttribute) == 0xC0, "FileSystemAttribute has incorrect size");
+
+} // namespace FileSys

core/fs/fs_memory_management.h

@@ -0,0 +1,40 @@
+// SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <mutex>
+#include "common/alignment.h"
+
+namespace FileSys {
+
+constexpr size_t RequiredAlignment = alignof(u64);
+
+inline void* AllocateUnsafe(size_t size) {
+    // Allocate
+    void* const ptr = ::operator new(size, std::align_val_t{RequiredAlignment});
+
+    // Check alignment
+    ASSERT(Common::IsAligned(reinterpret_cast<uintptr_t>(ptr), RequiredAlignment));
+
+    // Return allocated pointer
+    return ptr;
+}
+
+inline void DeallocateUnsafe(void* ptr, size_t size) {
+    // Deallocate the pointer
+    ::operator delete(ptr, std::align_val_t{RequiredAlignment});
+}
+
+inline void* Allocate(size_t size) {
+    return AllocateUnsafe(size);
+}
+
+inline void Deallocate(void* ptr, size_t size) {
+    // If the pointer is non-null, deallocate it
+    if (ptr != nullptr) {
+        DeallocateUnsafe(ptr, size);
+    }
+}
+
+} // namespace FileSys

core/fs/fs_operate_range.h

@@ -0,0 +1,22 @@
+// SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_types.h"
+
+namespace FileSys {
+
+enum class OperationId : s64 {
+    FillZero = 0,
+    DestroySignature = 1,
+    Invalidate = 2,
+    QueryRange = 3,
+    QueryUnpreparedRange = 4,
+    QueryLazyLoadCompletionRate = 5,
+    SetLazyLoadPriority = 6,
+
+    ReadLazyLoadFileForciblyForDebug = 10001,
+};
+
+} // namespace FileSys

core/fs/fs_path.h

@@ -0,0 +1,566 @@
+// SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/alignment.h"
+#include "common/common_funcs.h"
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fs_memory_management.h"
+#include "core/file_sys/fs_path_utility.h"
+#include "core/file_sys/fs_string_util.h"
+#include "core/hle/result.h"
+
+namespace FileSys {
+class DirectoryPathParser;
+
+class Path {
+    YUZU_NON_COPYABLE(Path);
+    YUZU_NON_MOVEABLE(Path);
+
+private:
+    static constexpr const char* EmptyPath = "";
+    static constexpr size_t WriteBufferAlignmentLength = 8;
+
+private:
+    friend class DirectoryPathParser;
+
+public:
+    class WriteBuffer {
+        YUZU_NON_COPYABLE(WriteBuffer);
+
+    private:
+        char* m_buffer;
+        size_t m_length_and_is_normalized;
+
+    public:
+        constexpr WriteBuffer() : m_buffer(nullptr), m_length_and_is_normalized(0) {}
+
+        constexpr ~WriteBuffer() {
+            if (m_buffer != nullptr) {
+                Deallocate(m_buffer, this->GetLength());
+                this->ResetBuffer();
+            }
+        }
+
+        constexpr WriteBuffer(WriteBuffer&& rhs)
+            : m_buffer(rhs.m_buffer), m_length_and_is_normalized(rhs.m_length_and_is_normalized) {
+            rhs.ResetBuffer();
+        }
+
+        constexpr WriteBuffer& operator=(WriteBuffer&& rhs) {
+            if (m_buffer != nullptr) {
+                Deallocate(m_buffer, this->GetLength());
+            }
+
+            m_buffer = rhs.m_buffer;
+            m_length_and_is_normalized = rhs.m_length_and_is_normalized;
+
+            rhs.ResetBuffer();
+
+            return *this;
+        }
+
+        constexpr void ResetBuffer() {
+            m_buffer = nullptr;
+            this->SetLength(0);
+        }
+
+        constexpr char* Get() const {
+            return m_buffer;
+        }
+
+        constexpr size_t GetLength() const {
+            return m_length_and_is_normalized >> 1;
+        }
+
+        constexpr bool IsNormalized() const {
+            return static_cast<bool>(m_length_and_is_normalized & 1);
+        }
+
+        constexpr void SetNormalized() {
+            m_length_and_is_normalized |= static_cast<size_t>(1);
+        }
+
+        constexpr void SetNotNormalized() {
+            m_length_and_is_normalized &= ~static_cast<size_t>(1);
+        }
+
+    private:
+        constexpr WriteBuffer(char* buffer, size_t length)
+            : m_buffer(buffer), m_length_and_is_normalized(0) {
+            this->SetLength(length);
+        }
+
+    public:
+        static WriteBuffer Make(size_t length) {
+            if (void* alloc = Allocate(length); alloc != nullptr) {
+                return WriteBuffer(static_cast<char*>(alloc), length);
+            } else {
+                return WriteBuffer();
+            }
+        }
+
+    private:
+        constexpr void SetLength(size_t size) {
+            m_length_and_is_normalized = (m_length_and_is_normalized & 1) | (size << 1);
+        }
+    };
+
+private:
+    const char* m_str;
+    WriteBuffer m_write_buffer;
+
+public:
+    constexpr Path() : m_str(EmptyPath), m_write_buffer() {}
+
+    constexpr Path(const char* s) : m_str(s), m_write_buffer() {
+        m_write_buffer.SetNormalized();
+    }
+
+    constexpr ~Path() = default;
+
+    constexpr Result SetShallowBuffer(const char* buffer) {
+        // Check pre-conditions
+        ASSERT(m_write_buffer.GetLength() == 0);
+
+        // Check the buffer is valid
+        R_UNLESS(buffer != nullptr, ResultNullptrArgument);
+
+        // Set buffer
+        this->SetReadOnlyBuffer(buffer);
+
+        // Note that we're normalized
+        this->SetNormalized();
+
+        R_SUCCEED();
+    }
+
+    constexpr const char* GetString() const {
+        // Check pre-conditions
+        ASSERT(this->IsNormalized());
+
+        return m_str;
+    }
+
+    constexpr size_t GetLength() const {
+        if (std::is_constant_evaluated()) {
+            return Strlen(this->GetString());
+        } else {
+            return std::strlen(this->GetString());
+        }
+    }
+
+    constexpr bool IsEmpty() const {
+        return *m_str == '\x00';
+    }
+
+    constexpr bool IsMatchHead(const char* p, size_t len) const {
+        return Strncmp(this->GetString(), p, len) == 0;
+    }
+
+    Result Initialize(const Path& rhs) {
+        // Check the other path is normalized
+        const bool normalized = rhs.IsNormalized();
+        R_UNLESS(normalized, ResultNotNormalized);
+
+        // Allocate buffer for our path
+        const auto len = rhs.GetLength();
+        R_TRY(this->Preallocate(len + 1));
+
+        // Copy the path
+        const size_t copied = Strlcpy<char>(m_write_buffer.Get(), rhs.GetString(), len + 1);
+        R_UNLESS(copied == len, ResultUnexpectedInPathA);
+
+        // Set normalized
+        this->SetNormalized();
+        R_SUCCEED();
+    }
+
+    Result Initialize(const char* path, size_t len) {
+        // Check the path is valid
+        R_UNLESS(path != nullptr, ResultNullptrArgument);
+
+        // Initialize
+        R_TRY(this->InitializeImpl(path, len));
+
+        // Set not normalized
+        this->SetNotNormalized();
+
+        R_SUCCEED();
+    }
+
+    Result Initialize(const char* path) {
+        // Check the path is valid
+        R_UNLESS(path != nullptr, ResultNullptrArgument);
+
+        R_RETURN(this->Initialize(path, std::strlen(path)));
+    }
+
+    Result InitializeWithReplaceBackslash(const char* path) {
+        // Check the path is valid
+        R_UNLESS(path != nullptr, ResultNullptrArgument);
+
+        // Initialize
+        R_TRY(this->InitializeImpl(path, std::strlen(path)));
+
+        // Replace slashes as desired
+        if (const auto write_buffer_length = m_write_buffer.GetLength(); write_buffer_length > 1) {
+            Replace(m_write_buffer.Get(), write_buffer_length - 1, '\\', '/');
+        }
+
+        // Set not normalized
+        this->SetNotNormalized();
+
+        R_SUCCEED();
+    }
+
+    Result InitializeWithReplaceForwardSlashes(const char* path) {
+        // Check the path is valid
+        R_UNLESS(path != nullptr, ResultNullptrArgument);
+
+        // Initialize
+        R_TRY(this->InitializeImpl(path, std::strlen(path)));
+
+        // Replace slashes as desired
+        if (m_write_buffer.GetLength() > 1) {
+            if (auto* p = m_write_buffer.Get(); p[0] == '/' && p[1] == '/') {
+                p[0] = '\\';
+                p[1] = '\\';
+            }
+        }
+
+        // Set not normalized
+        this->SetNotNormalized();
+
+        R_SUCCEED();
+    }
+
+    Result InitializeWithNormalization(const char* path, size_t size) {
+        // Check the path is valid
+        R_UNLESS(path != nullptr, ResultNullptrArgument);
+
+        // Initialize
+        R_TRY(this->InitializeImpl(path, size));
+
+        // Set not normalized
+        this->SetNotNormalized();
+
+        // Perform normalization
+        PathFlags path_flags;
+        if (IsPathRelative(m_str)) {
+            path_flags.AllowRelativePath();
+        } else if (IsWindowsPath(m_str, true)) {
+            path_flags.AllowWindowsPath();
+        } else {
+            /* NOTE: In this case, Nintendo checks is normalized, then sets is normalized, then
+             * returns success. */
+            /* This seems like a bug. */
+            size_t dummy;
+            bool normalized;
+            R_TRY(PathFormatter::IsNormalized(std::addressof(normalized), std::addressof(dummy),
+                                              m_str));
+
+            this->SetNormalized();
+            R_SUCCEED();
+        }
+
+        // Normalize
+        R_TRY(this->Normalize(path_flags));
+
+        this->SetNormalized();
+        R_SUCCEED();
+    }
+
+    Result InitializeWithNormalization(const char* path) {
+        // Check the path is valid
+        R_UNLESS(path != nullptr, ResultNullptrArgument);
+
+        R_RETURN(this->InitializeWithNormalization(path, std::strlen(path)));
+    }
+
+    Result InitializeAsEmpty() {
+        // Clear our buffer
+        this->ClearBuffer();
+
+        // Set normalized
+        this->SetNormalized();
+
+        R_SUCCEED();
+    }
+
+    Result AppendChild(const char* child) {
+        // Check the path is valid
+        R_UNLESS(child != nullptr, ResultNullptrArgument);
+
+        // Basic checks. If we have a path and the child is empty, we have nothing to do
+        const char* c = child;
+        if (m_str[0]) {
+            // Skip an early separator
+            if (*c == '/') {
+                ++c;
+            }
+
+            R_SUCCEED_IF(*c == '\x00');
+        }
+
+        // If we don't have a string, we can just initialize
+        auto cur_len = std::strlen(m_str);
+        if (cur_len == 0) {
+            R_RETURN(this->Initialize(child));
+        }
+
+        // Remove a trailing separator
+        if (m_str[cur_len - 1] == '/' || m_str[cur_len - 1] == '\\') {
+            --cur_len;
+        }
+
+        // Get the child path's length
+        auto child_len = std::strlen(c);
+
+        // Reset our write buffer
+        WriteBuffer old_write_buffer;
+        if (m_write_buffer.Get() != nullptr) {
+            old_write_buffer = std::move(m_write_buffer);
+            this->ClearBuffer();
+        }
+
+        // Pre-allocate the new buffer
+        R_TRY(this->Preallocate(cur_len + 1 + child_len + 1));
+
+        // Get our write buffer
+        auto* dst = m_write_buffer.Get();
+        if (old_write_buffer.Get() != nullptr && cur_len > 0) {
+            Strlcpy<char>(dst, old_write_buffer.Get(), cur_len + 1);
+        }
+
+        // Add separator
+        dst[cur_len] = '/';
+
+        // Copy the child path
+        const size_t copied = Strlcpy<char>(dst + cur_len + 1, c, child_len + 1);
+        R_UNLESS(copied == child_len, ResultUnexpectedInPathA);
+
+        R_SUCCEED();
+    }
+
+    Result AppendChild(const Path& rhs) {
+        R_RETURN(this->AppendChild(rhs.GetString()));
+    }
+
+    Result Combine(const Path& parent, const Path& child) {
+        // Get the lengths
+        const auto p_len = parent.GetLength();
+        const auto c_len = child.GetLength();
+
+        // Allocate our buffer
+        R_TRY(this->Preallocate(p_len + c_len + 1));
+
+        // Initialize as parent
+        R_TRY(this->Initialize(parent));
+
+        // If we're empty, we can just initialize as child
+        if (this->IsEmpty()) {
+            R_TRY(this->Initialize(child));
+        } else {
+            // Otherwise, we should append the child
+            R_TRY(this->AppendChild(child));
+        }
+
+        R_SUCCEED();
+    }
+
+    Result RemoveChild() {
+        // If we don't have a write-buffer, ensure that we have one
+        if (m_write_buffer.Get() == nullptr) {
+            if (const auto len = std::strlen(m_str); len > 0) {
+                R_TRY(this->Preallocate(len));
+                Strlcpy<char>(m_write_buffer.Get(), m_str, len + 1);
+            }
+        }
+
+        // Check that it's possible for us to remove a child
+        auto* p = m_write_buffer.Get();
+        s32 len = static_cast<s32>(std::strlen(p));
+        R_UNLESS(len != 1 || (p[0] != '/' && p[0] != '.'), ResultNotImplemented);
+
+        // Handle a trailing separator
+        if (len > 0 && (p[len - 1] == '\\' || p[len - 1] == '/')) {
+            --len;
+        }
+
+        // Remove the child path segment
+        while ((--len) >= 0 && p[len]) {
+            if (p[len] == '/' || p[len] == '\\') {
+                if (len > 0) {
+                    p[len] = 0;
+                } else {
+                    p[1] = 0;
+                    len = 1;
+                }
+                break;
+            }
+        }
+
+        // Check that length remains > 0
+        R_UNLESS(len > 0, ResultNotImplemented);
+
+        R_SUCCEED();
+    }
+
+    Result Normalize(const PathFlags& flags) {
+        // If we're already normalized, nothing to do
+        R_SUCCEED_IF(this->IsNormalized());
+
+        // Check if we're normalized
+        bool normalized;
+        size_t dummy;
+        R_TRY(PathFormatter::IsNormalized(std::addressof(normalized), std::addressof(dummy), m_str,
+                                          flags));
+
+        // If we're not normalized, normalize
+        if (!normalized) {
+            // Determine necessary buffer length
+            auto len = m_write_buffer.GetLength();
+            if (flags.IsRelativePathAllowed() && IsPathRelative(m_str)) {
+                len += 2;
+            }
+            if (flags.IsWindowsPathAllowed() && IsWindowsPath(m_str, true)) {
+                len += 1;
+            }
+
+            // Allocate a new buffer
+            const size_t size = Common::AlignUp(len, WriteBufferAlignmentLength);
+            auto buf = WriteBuffer::Make(size);
+            R_UNLESS(buf.Get() != nullptr, ResultAllocationMemoryFailedMakeUnique);
+
+            // Normalize into it
+            R_TRY(PathFormatter::Normalize(buf.Get(), size, m_write_buffer.Get(),
+                                           m_write_buffer.GetLength(), flags));
+
+            // Set the normalized buffer as our buffer
+            this->SetModifiableBuffer(std::move(buf));
+        }
+
+        // Set normalized
+        this->SetNormalized();
+        R_SUCCEED();
+    }
+
+private:
+    void ClearBuffer() {
+        m_write_buffer.ResetBuffer();
+        m_str = EmptyPath;
+    }
+
+    void SetModifiableBuffer(WriteBuffer&& buffer) {
+        // Check pre-conditions
+        ASSERT(buffer.Get() != nullptr);
+        ASSERT(buffer.GetLength() > 0);
+        ASSERT(Common::IsAligned(buffer.GetLength(), WriteBufferAlignmentLength));
+
+        // Get whether we're normalized
+        if (m_write_buffer.IsNormalized()) {
+            buffer.SetNormalized();
+        } else {
+            buffer.SetNotNormalized();
+        }
+
+        // Set write buffer
+        m_write_buffer = std::move(buffer);
+        m_str = m_write_buffer.Get();
+    }
+
+    constexpr void SetReadOnlyBuffer(const char* buffer) {
+        m_str = buffer;
+        m_write_buffer.ResetBuffer();
+    }
+
+    Result Preallocate(size_t length) {
+        // Allocate additional space, if needed
+        if (length > m_write_buffer.GetLength()) {
+            // Allocate buffer
+            const size_t size = Common::AlignUp(length, WriteBufferAlignmentLength);
+            auto buf = WriteBuffer::Make(size);
+            R_UNLESS(buf.Get() != nullptr, ResultAllocationMemoryFailedMakeUnique);
+
+            // Set write buffer
+            this->SetModifiableBuffer(std::move(buf));
+        }
+
+        R_SUCCEED();
+    }
+
+    Result InitializeImpl(const char* path, size_t size) {
+        if (size > 0 && path[0]) {
+            // Pre allocate a buffer for the path
+            R_TRY(this->Preallocate(size + 1));
+
+            // Copy the path
+            const size_t copied = Strlcpy<char>(m_write_buffer.Get(), path, size + 1);
+            R_UNLESS(copied >= size, ResultUnexpectedInPathA);
+        } else {
+            // We can just clear the buffer
+            this->ClearBuffer();
+        }
+
+        R_SUCCEED();
+    }
+
+    constexpr char* GetWriteBuffer() {
+        ASSERT(m_write_buffer.Get() != nullptr);
+        return m_write_buffer.Get();
+    }
+
+    constexpr size_t GetWriteBufferLength() const {
+        return m_write_buffer.GetLength();
+    }
+
+    constexpr bool IsNormalized() const {
+        return m_write_buffer.IsNormalized();
+    }
+
+    constexpr void SetNormalized() {
+        m_write_buffer.SetNormalized();
+    }
+
+    constexpr void SetNotNormalized() {
+        m_write_buffer.SetNotNormalized();
+    }
+
+public:
+    bool operator==(const FileSys::Path& rhs) const {
+        return std::strcmp(this->GetString(), rhs.GetString()) == 0;
+    }
+    bool operator!=(const FileSys::Path& rhs) const {
+        return !(*this == rhs);
+    }
+    bool operator==(const char* p) const {
+        return std::strcmp(this->GetString(), p) == 0;
+    }
+    bool operator!=(const char* p) const {
+        return !(*this == p);
+    }
+};
+
+inline Result SetUpFixedPath(FileSys::Path* out, const char* s) {
+    // Verify the path is normalized
+    bool normalized;
+    size_t dummy;
+    R_TRY(PathNormalizer::IsNormalized(std::addressof(normalized), std::addressof(dummy), s));
+
+    R_UNLESS(normalized, ResultInvalidPathFormat);
+
+    // Set the fixed path
+    R_RETURN(out->SetShallowBuffer(s));
+}
+
+constexpr inline bool IsWindowsDriveRootPath(const FileSys::Path& path) {
+    const char* const str = path.GetString();
+    return IsWindowsDrive(str) &&
+           (str[2] == StringTraits::DirectorySeparator ||
+            str[2] == StringTraits::AlternateDirectorySeparator) &&
+           str[3] == StringTraits::NullTerminator;
+}
+
+} // namespace FileSys

core/fs/fs_save_data_types.h

@@ -0,0 +1,188 @@
+// SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+#include <fmt/format.h>
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+
+namespace FileSys {
+
+using SaveDataId = u64;
+using SystemSaveDataId = u64;
+using SystemBcatSaveDataId = SystemSaveDataId;
+using ProgramId = u64;
+
+enum class SaveDataSpaceId : u8 {
+    System = 0,
+    User = 1,
+    SdSystem = 2,
+    Temporary = 3,
+    SdUser = 4,
+
+    ProperSystem = 100,
+    SafeMode = 101,
+};
+
+enum class SaveDataType : u8 {
+    System = 0,
+    Account = 1,
+    Bcat = 2,
+    Device = 3,
+    Temporary = 4,
+    Cache = 5,
+    SystemBcat = 6,
+};
+
+enum class SaveDataRank : u8 {
+    Primary = 0,
+    Secondary = 1,
+};
+
+struct SaveDataSize {
+    u64 normal;
+    u64 journal;
+};
+static_assert(sizeof(SaveDataSize) == 0x10, "SaveDataSize has invalid size.");
+
+using UserId = u128;
+static_assert(std::is_trivially_copyable_v<UserId>, "Data type must be trivially copyable.");
+static_assert(sizeof(UserId) == 0x10, "UserId has invalid size.");
+
+constexpr inline SystemSaveDataId InvalidSystemSaveDataId = 0;
+constexpr inline UserId InvalidUserId = {};
+
+enum class SaveDataFlags : u32 {
+    None = (0 << 0),
+    KeepAfterResettingSystemSaveData = (1 << 0),
+    KeepAfterRefurbishment = (1 << 1),
+    KeepAfterResettingSystemSaveDataWithoutUserSaveData = (1 << 2),
+    NeedsSecureDelete = (1 << 3),
+};
+
+enum class SaveDataMetaType : u8 {
+    None = 0,
+    Thumbnail = 1,
+    ExtensionContext = 2,
+};
+
+struct SaveDataMetaInfo {
+    u32 size;
+    SaveDataMetaType type;
+    INSERT_PADDING_BYTES(0xB);
+};
+static_assert(std::is_trivially_copyable_v<SaveDataMetaInfo>,
+              "Data type must be trivially copyable.");
+static_assert(sizeof(SaveDataMetaInfo) == 0x10, "SaveDataMetaInfo has invalid size.");
+
+struct SaveDataCreationInfo {
+    s64 size;
+    s64 journal_size;
+    s64 block_size;
+    u64 owner_id;
+    u32 flags;
+    SaveDataSpaceId space_id;
+    bool pseudo;
+    INSERT_PADDING_BYTES(0x1A);
+};
+static_assert(std::is_trivially_copyable_v<SaveDataCreationInfo>,
+              "Data type must be trivially copyable.");
+static_assert(sizeof(SaveDataCreationInfo) == 0x40, "SaveDataCreationInfo has invalid size.");
+
+struct SaveDataAttribute {
+    ProgramId program_id;
+    UserId user_id;
+    SystemSaveDataId system_save_data_id;
+    SaveDataType type;
+    SaveDataRank rank;
+    u16 index;
+    INSERT_PADDING_BYTES(0x1C);
+
+    static constexpr SaveDataAttribute Make(ProgramId program_id, SaveDataType type, UserId user_id,
+                                            SystemSaveDataId system_save_data_id, u16 index,
+                                            SaveDataRank rank) {
+        return {
+            .program_id = program_id,
+            .user_id = user_id,
+            .system_save_data_id = system_save_data_id,
+            .type = type,
+            .rank = rank,
+            .index = index,
+        };
+    }
+
+    static constexpr SaveDataAttribute Make(ProgramId program_id, SaveDataType type, UserId user_id,
+                                            SystemSaveDataId system_save_data_id, u16 index) {
+        return Make(program_id, type, user_id, system_save_data_id, index, SaveDataRank::Primary);
+    }
+
+    static constexpr SaveDataAttribute Make(ProgramId program_id, SaveDataType type, UserId user_id,
+                                            SystemSaveDataId system_save_data_id) {
+        return Make(program_id, type, user_id, system_save_data_id, 0, SaveDataRank::Primary);
+    }
+
+    std::string DebugInfo() const {
+        return fmt::format(
+            "[title_id={:016X}, user_id={:016X}{:016X}, save_id={:016X}, type={:02X}, "
+            "rank={}, index={}]",
+            program_id, user_id[1], user_id[0], system_save_data_id, static_cast<u8>(type),
+            static_cast<u8>(rank), index);
+    }
+};
+static_assert(sizeof(SaveDataAttribute) == 0x40);
+static_assert(std::is_trivially_destructible<SaveDataAttribute>::value);
+
+constexpr inline bool operator<(const SaveDataAttribute& lhs, const SaveDataAttribute& rhs) {
+    return std::tie(lhs.program_id, lhs.user_id, lhs.system_save_data_id, lhs.index, lhs.rank) <
+           std::tie(rhs.program_id, rhs.user_id, rhs.system_save_data_id, rhs.index, rhs.rank);
+}
+
+constexpr inline bool operator==(const SaveDataAttribute& lhs, const SaveDataAttribute& rhs) {
+    return std::tie(lhs.program_id, lhs.user_id, lhs.system_save_data_id, lhs.type, lhs.rank,
+                    lhs.index) == std::tie(rhs.program_id, rhs.user_id, rhs.system_save_data_id,
+                                           rhs.type, rhs.rank, rhs.index);
+}
+
+constexpr inline bool operator!=(const SaveDataAttribute& lhs, const SaveDataAttribute& rhs) {
+    return !(lhs == rhs);
+}
+
+struct SaveDataExtraData {
+    SaveDataAttribute attr;
+    u64 owner_id;
+    s64 timestamp;
+    u32 flags;
+    INSERT_PADDING_BYTES(4);
+    s64 available_size;
+    s64 journal_size;
+    s64 commit_id;
+    INSERT_PADDING_BYTES(0x190);
+};
+static_assert(sizeof(SaveDataExtraData) == 0x200, "SaveDataExtraData has invalid size.");
+static_assert(std::is_trivially_copyable_v<SaveDataExtraData>,
+              "Data type must be trivially copyable.");
+
+struct SaveDataFilter {
+    bool use_program_id;
+    bool use_save_data_type;
+    bool use_user_id;
+    bool use_save_data_id;
+    bool use_index;
+    SaveDataRank rank;
+    SaveDataAttribute attribute;
+};
+static_assert(sizeof(SaveDataFilter) == 0x48, "SaveDataFilter has invalid size.");
+static_assert(std::is_trivially_copyable_v<SaveDataFilter>,
+              "Data type must be trivially copyable.");
+
+struct HashSalt {
+    static constexpr size_t Size = 32;
+
+    std::array<u8, Size> value;
+};
+static_assert(std::is_trivially_copyable_v<HashSalt>, "Data type must be trivially copyable.");
+static_assert(sizeof(HashSalt) == HashSalt::Size);
+
+} // namespace FileSys

core/fs/fs_string_util.h

@@ -0,0 +1,241 @@
+// SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/assert.h"
+
+namespace FileSys {
+
+template <typename T>
+constexpr int Strlen(const T* str) {
+    ASSERT(str != nullptr);
+
+    int length = 0;
+    while (*str++) {
+        ++length;
+    }
+
+    return length;
+}
+
+template <typename T>
+constexpr int Strnlen(const T* str, std::size_t count) {
+    return Strnlen(str, static_cast<int>(count));
+}
+
+template <typename T>
+constexpr int Strnlen(const T* str, int count) {
+    ASSERT(str != nullptr);
+    ASSERT(count >= 0);
+
+    int length = 0;
+    while (count-- && *str++) {
+        ++length;
+    }
+
+    return length;
+}
+
+template <typename T>
+constexpr int Strncmp(const T* lhs, const T* rhs, std::size_t count) {
+    return Strncmp(lhs, rhs, static_cast<int>(count));
+}
+
+template <typename T>
+constexpr int Strncmp(const T* lhs, const T* rhs, int count) {
+    ASSERT(lhs != nullptr);
+    ASSERT(rhs != nullptr);
+    ASSERT(count >= 0);
+
+    if (count == 0) {
+        return 0;
+    }
+
+    T l, r;
+    do {
+        l = *(lhs++);
+        r = *(rhs++);
+    } while (l && (l == r) && (--count));
+
+    return l - r;
+}
+
+template <typename T>
+static constexpr int Strlcpy(T* dst, const T* src, std::size_t count) {
+    return Strlcpy<T>(dst, src, static_cast<int>(count));
+}
+
+template <typename T>
+static constexpr int Strlcpy(T* dst, const T* src, int count) {
+    ASSERT(dst != nullptr);
+    ASSERT(src != nullptr);
+
+    const T* cur = src;
+    if (count > 0) {
+        while ((--count) && *cur) {
+            *(dst++) = *(cur++);
+        }
+        *dst = 0;
+    }
+
+    while (*cur) {
+        cur++;
+    }
+
+    return static_cast<int>(cur - src);
+}
+
+enum CharacterEncodingResult {
+    CharacterEncodingResult_Success = 0,
+    CharacterEncodingResult_InsufficientLength = 1,
+    CharacterEncodingResult_InvalidFormat = 2,
+};
+
+namespace impl {
+
+class CharacterEncodingHelper {
+public:
+    static constexpr int8_t Utf8NBytesInnerTable[0x100 + 1] = {
+        -1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1,  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1,  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1,  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1,  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+        2,  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3,
+        3,  3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 7, 8,
+    };
+
+    static constexpr char GetUtf8NBytes(size_t i) {
+        return static_cast<char>(Utf8NBytesInnerTable[1 + i]);
+    }
+};
+
+} // namespace impl
+
+constexpr inline CharacterEncodingResult ConvertCharacterUtf8ToUtf32(u32* dst, const char* src) {
+    // Check pre-conditions
+    ASSERT(dst != nullptr);
+    ASSERT(src != nullptr);
+
+    // Perform the conversion
+    const auto* p = src;
+    switch (impl::CharacterEncodingHelper::GetUtf8NBytes(static_cast<unsigned char>(p[0]))) {
+    case 1:
+        *dst = static_cast<u32>(p[0]);
+        return CharacterEncodingResult_Success;
+    case 2:
+        if ((static_cast<u32>(p[0]) & 0x1E) != 0) {
+            if (impl::CharacterEncodingHelper::GetUtf8NBytes(static_cast<unsigned char>(p[1])) ==
+                0) {
+                *dst = (static_cast<u32>(p[0] & 0x1F) << 6) | (static_cast<u32>(p[1] & 0x3F) << 0);
+                return CharacterEncodingResult_Success;
+            }
+        }
+        break;
+    case 3:
+        if (impl::CharacterEncodingHelper::GetUtf8NBytes(static_cast<unsigned char>(p[1])) == 0 &&
+            impl::CharacterEncodingHelper::GetUtf8NBytes(static_cast<unsigned char>(p[2])) == 0) {
+            const u32 c = (static_cast<u32>(p[0] & 0xF) << 12) |
+                          (static_cast<u32>(p[1] & 0x3F) << 6) |
+                          (static_cast<u32>(p[2] & 0x3F) << 0);
+            if ((c & 0xF800) != 0 && (c & 0xF800) != 0xD800) {
+                *dst = c;
+                return CharacterEncodingResult_Success;
+            }
+        }
+        return CharacterEncodingResult_InvalidFormat;
+    case 4:
+        if (impl::CharacterEncodingHelper::GetUtf8NBytes(static_cast<unsigned char>(p[1])) == 0 &&
+            impl::CharacterEncodingHelper::GetUtf8NBytes(static_cast<unsigned char>(p[2])) == 0 &&
+            impl::CharacterEncodingHelper::GetUtf8NBytes(static_cast<unsigned char>(p[3])) == 0) {
+            const u32 c =
+                (static_cast<u32>(p[0] & 0x7) << 18) | (static_cast<u32>(p[1] & 0x3F) << 12) |
+                (static_cast<u32>(p[2] & 0x3F) << 6) | (static_cast<u32>(p[3] & 0x3F) << 0);
+            if (c >= 0x10000 && c < 0x110000) {
+                *dst = c;
+                return CharacterEncodingResult_Success;
+            }
+        }
+        return CharacterEncodingResult_InvalidFormat;
+    default:
+        break;
+    }
+
+    // We failed to convert
+    return CharacterEncodingResult_InvalidFormat;
+}
+
+constexpr inline CharacterEncodingResult PickOutCharacterFromUtf8String(char* dst,
+                                                                        const char** str) {
+    // Check pre-conditions
+    ASSERT(dst != nullptr);
+    ASSERT(str != nullptr);
+    ASSERT(*str != nullptr);
+
+    // Clear the output
+    dst[0] = 0;
+    dst[1] = 0;
+    dst[2] = 0;
+    dst[3] = 0;
+
+    // Perform the conversion
+    const auto* p = *str;
+    u32 c = static_cast<u32>(*p);
+    switch (impl::CharacterEncodingHelper::GetUtf8NBytes(c)) {
+    case 1:
+        dst[0] = (*str)[0];
+        ++(*str);
+        break;
+    case 2:
+        if ((p[0] & 0x1E) != 0) {
+            if (impl::CharacterEncodingHelper::GetUtf8NBytes(static_cast<unsigned char>(p[1])) ==
+                0) {
+                c = (static_cast<u32>(p[0] & 0x1F) << 6) | (static_cast<u32>(p[1] & 0x3F) << 0);
+                dst[0] = (*str)[0];
+                dst[1] = (*str)[1];
+                (*str) += 2;
+                break;
+            }
+        }
+        return CharacterEncodingResult_InvalidFormat;
+    case 3:
+        if (impl::CharacterEncodingHelper::GetUtf8NBytes(static_cast<unsigned char>(p[1])) == 0 &&
+            impl::CharacterEncodingHelper::GetUtf8NBytes(static_cast<unsigned char>(p[2])) == 0) {
+            c = (static_cast<u32>(p[0] & 0xF) << 12) | (static_cast<u32>(p[1] & 0x3F) << 6) |
+                (static_cast<u32>(p[2] & 0x3F) << 0);
+            if ((c & 0xF800) != 0 && (c & 0xF800) != 0xD800) {
+                dst[0] = (*str)[0];
+                dst[1] = (*str)[1];
+                dst[2] = (*str)[2];
+                (*str) += 3;
+                break;
+            }
+        }
+        return CharacterEncodingResult_InvalidFormat;
+    case 4:
+        if (impl::CharacterEncodingHelper::GetUtf8NBytes(static_cast<unsigned char>(p[1])) == 0 &&
+            impl::CharacterEncodingHelper::GetUtf8NBytes(static_cast<unsigned char>(p[2])) == 0 &&
+            impl::CharacterEncodingHelper::GetUtf8NBytes(static_cast<unsigned char>(p[3])) == 0) {
+            c = (static_cast<u32>(p[0] & 0x7) << 18) | (static_cast<u32>(p[1] & 0x3F) << 12) |
+                (static_cast<u32>(p[2] & 0x3F) << 6) | (static_cast<u32>(p[3] & 0x3F) << 0);
+            if (c >= 0x10000 && c < 0x110000) {
+                dst[0] = (*str)[0];
+                dst[1] = (*str)[1];
+                dst[2] = (*str)[2];
+                dst[3] = (*str)[3];
+                (*str) += 4;
+                break;
+            }
+        }
+        return CharacterEncodingResult_InvalidFormat;
+    default:
+        return CharacterEncodingResult_InvalidFormat;
+    }
+
+    return CharacterEncodingResult_Success;
+}
+
+} // namespace FileSys

core/fs/fsa/fs_i_directory.h

@@ -0,0 +1,91 @@
+// SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_types.h"
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fs_directory.h"
+#include "core/file_sys/fs_file.h"
+#include "core/file_sys/fs_filesystem.h"
+#include "core/file_sys/savedata_factory.h"
+#include "core/file_sys/vfs/vfs.h"
+#include "core/hle/result.h"
+
+namespace FileSys::Fsa {
+
+class IDirectory {
+public:
+    explicit IDirectory(VirtualDir backend_, OpenDirectoryMode mode)
+        : backend(std::move(backend_)) {
+        // TODO(DarkLordZach): Verify that this is the correct behavior.
+        // Build entry index now to save time later.
+        if (True(mode & OpenDirectoryMode::Directory)) {
+            BuildEntryIndex(backend->GetSubdirectories(), DirectoryEntryType::Directory);
+        }
+        if (True(mode & OpenDirectoryMode::File)) {
+            BuildEntryIndex(backend->GetFiles(), DirectoryEntryType::File);
+        }
+    }
+    virtual ~IDirectory() {}
+
+    Result Read(s64* out_count, DirectoryEntry* out_entries, s64 max_entries) {
+        R_UNLESS(out_count != nullptr, ResultNullptrArgument);
+        if (max_entries == 0) {
+            *out_count = 0;
+            R_SUCCEED();
+        }
+        R_UNLESS(out_entries != nullptr, ResultNullptrArgument);
+        R_UNLESS(max_entries > 0, ResultInvalidArgument);
+        R_RETURN(this->DoRead(out_count, out_entries, max_entries));
+    }
+
+    Result GetEntryCount(s64* out) {
+        R_UNLESS(out != nullptr, ResultNullptrArgument);
+        R_RETURN(this->DoGetEntryCount(out));
+    }
+
+private:
+    Result DoRead(s64* out_count, DirectoryEntry* out_entries, s64 max_entries) {
+        const u64 actual_entries =
+            std::min(static_cast<u64>(max_entries), entries.size() - next_entry_index);
+        const auto* begin = reinterpret_cast<u8*>(entries.data() + next_entry_index);
+        const auto* end = reinterpret_cast<u8*>(entries.data() + next_entry_index + actual_entries);
+        const auto range_size = static_cast<std::size_t>(std::distance(begin, end));
+
+        next_entry_index += actual_entries;
+        *out_count = actual_entries;
+
+        std::memcpy(out_entries, begin, range_size);
+
+        R_SUCCEED();
+    }
+
+    Result DoGetEntryCount(s64* out) {
+        *out = entries.size() - next_entry_index;
+        R_SUCCEED();
+    }
+
+    // TODO: Remove this when VFS is gone
+    template <typename T>
+    void BuildEntryIndex(const std::vector<T>& new_data, DirectoryEntryType type) {
+        entries.reserve(entries.size() + new_data.size());
+
+        for (const auto& new_entry : new_data) {
+            auto name = new_entry->GetName();
+
+            if (type == DirectoryEntryType::File && name == GetSaveDataSizeFileName()) {
+                continue;
+            }
+
+            entries.emplace_back(name, static_cast<s8>(type),
+                                 type == DirectoryEntryType::Directory ? 0 : new_entry->GetSize());
+        }
+    }
+
+    VirtualDir backend;
+    std::vector<DirectoryEntry> entries;
+    u64 next_entry_index = 0;
+};
+
+} // namespace FileSys::Fsa

core/fs/fsa/fs_i_file.h

@@ -0,0 +1,167 @@
+// SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/overflow.h"
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fs_file.h"
+#include "core/file_sys/fs_filesystem.h"
+#include "core/file_sys/fs_operate_range.h"
+#include "core/file_sys/vfs/vfs.h"
+#include "core/file_sys/vfs/vfs_types.h"
+#include "core/hle/result.h"
+
+namespace FileSys::Fsa {
+
+class IFile {
+public:
+    explicit IFile(VirtualFile backend_) : backend(std::move(backend_)) {}
+    virtual ~IFile() {}
+
+    Result Read(size_t* out, s64 offset, void* buffer, size_t size, const ReadOption& option) {
+        // Check that we have an output pointer
+        R_UNLESS(out != nullptr, ResultNullptrArgument);
+
+        // If we have nothing to read, just succeed
+        if (size == 0) {
+            *out = 0;
+            R_SUCCEED();
+        }
+
+        // Check that the read is valid
+        R_UNLESS(buffer != nullptr, ResultNullptrArgument);
+        R_UNLESS(offset >= 0, ResultOutOfRange);
+        R_UNLESS(Common::CanAddWithoutOverflow<s64>(offset, size), ResultOutOfRange);
+
+        // Do the read
+        R_RETURN(this->DoRead(out, offset, buffer, size, option));
+    }
+
+    Result Read(size_t* out, s64 offset, void* buffer, size_t size) {
+        R_RETURN(this->Read(out, offset, buffer, size, ReadOption::None));
+    }
+
+    Result GetSize(s64* out) {
+        R_UNLESS(out != nullptr, ResultNullptrArgument);
+        R_RETURN(this->DoGetSize(out));
+    }
+
+    Result Flush() {
+        R_RETURN(this->DoFlush());
+    }
+
+    Result Write(s64 offset, const void* buffer, size_t size, const WriteOption& option) {
+        // Handle the zero-size case
+        if (size == 0) {
+            if (option.HasFlushFlag()) {
+                R_TRY(this->Flush());
+            }
+            R_SUCCEED();
+        }
+
+        // Check the write is valid
+        R_UNLESS(buffer != nullptr, ResultNullptrArgument);
+        R_UNLESS(offset >= 0, ResultOutOfRange);
+        R_UNLESS(Common::CanAddWithoutOverflow<s64>(offset, size), ResultOutOfRange);
+
+        R_RETURN(this->DoWrite(offset, buffer, size, option));
+    }
+
+    Result SetSize(s64 size) {
+        R_UNLESS(size >= 0, ResultOutOfRange);
+        R_RETURN(this->DoSetSize(size));
+    }
+
+    Result OperateRange(void* dst, size_t dst_size, OperationId op_id, s64 offset, s64 size,
+                        const void* src, size_t src_size) {
+        R_RETURN(this->DoOperateRange(dst, dst_size, op_id, offset, size, src, src_size));
+    }
+
+    Result OperateRange(OperationId op_id, s64 offset, s64 size) {
+        R_RETURN(this->DoOperateRange(nullptr, 0, op_id, offset, size, nullptr, 0));
+    }
+
+protected:
+    Result DryRead(size_t* out, s64 offset, size_t size, const ReadOption& option,
+                   OpenMode open_mode) {
+        // Check that we can read
+        R_UNLESS(static_cast<u32>(open_mode & OpenMode::Read) != 0, ResultReadNotPermitted);
+
+        // Get the file size, and validate our offset
+        s64 file_size = 0;
+        R_TRY(this->DoGetSize(std::addressof(file_size)));
+        R_UNLESS(offset <= file_size, ResultOutOfRange);
+
+        *out = static_cast<size_t>(std::min(file_size - offset, static_cast<s64>(size)));
+        R_SUCCEED();
+    }
+
+    Result DrySetSize(s64 size, OpenMode open_mode) {
+        // Check that we can write
+        R_UNLESS(static_cast<u32>(open_mode & OpenMode::Write) != 0, ResultWriteNotPermitted);
+        R_SUCCEED();
+    }
+
+    Result DryWrite(bool* out_append, s64 offset, size_t size, const WriteOption& option,
+                    OpenMode open_mode) {
+        // Check that we can write
+        R_UNLESS(static_cast<u32>(open_mode & OpenMode::Write) != 0, ResultWriteNotPermitted);
+
+        // Get the file size
+        s64 file_size = 0;
+        R_TRY(this->DoGetSize(&file_size));
+
+        // Determine if we need to append
+        *out_append = false;
+        if (file_size < offset + static_cast<s64>(size)) {
+            R_UNLESS(static_cast<u32>(open_mode & OpenMode::AllowAppend) != 0,
+                     ResultFileExtensionWithoutOpenModeAllowAppend);
+            *out_append = true;
+        }
+
+        R_SUCCEED();
+    }
+
+private:
+    Result DoRead(size_t* out, s64 offset, void* buffer, size_t size, const ReadOption& option) {
+        const auto read_size = backend->Read(static_cast<u8*>(buffer), size, offset);
+        *out = read_size;
+
+        R_SUCCEED();
+    }
+
+    Result DoGetSize(s64* out) {
+        *out = backend->GetSize();
+        R_SUCCEED();
+    }
+
+    Result DoFlush() {
+        // Exists for SDK compatibiltity -- No need to flush file.
+        R_SUCCEED();
+    }
+
+    Result DoWrite(s64 offset, const void* buffer, size_t size, const WriteOption& option) {
+        const std::size_t written = backend->Write(static_cast<const u8*>(buffer), size, offset);
+
+        ASSERT_MSG(written == size,
+                   "Could not write all bytes to file (requested={:016X}, actual={:016X}).", size,
+                   written);
+
+        R_SUCCEED();
+    }
+
+    Result DoSetSize(s64 size) {
+        backend->Resize(size);
+        R_SUCCEED();
+    }
+
+    Result DoOperateRange(void* dst, size_t dst_size, OperationId op_id, s64 offset, s64 size,
+                          const void* src, size_t src_size) {
+        R_THROW(ResultNotImplemented);
+    }
+
+    VirtualFile backend;
+};
+
+} // namespace FileSys::Fsa

core/fs/fsa/fs_i_filesystem.h

@@ -0,0 +1,206 @@
+// SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fs_filesystem.h"
+#include "core/file_sys/fs_path.h"
+#include "core/file_sys/vfs/vfs_types.h"
+#include "core/hle/result.h"
+#include "core/hle/service/filesystem/filesystem.h"
+
+namespace FileSys::Fsa {
+
+class IFile;
+class IDirectory;
+
+enum class QueryId : u32 {
+    SetConcatenationFileAttribute = 0,
+    UpdateMac = 1,
+    IsSignedSystemPartitionOnSdCardValid = 2,
+    QueryUnpreparedFileInformation = 3,
+};
+
+class IFileSystem {
+public:
+    explicit IFileSystem(VirtualDir backend_) : backend{std::move(backend_)} {}
+    virtual ~IFileSystem() {}
+
+    Result CreateFile(const Path& path, s64 size, CreateOption option) {
+        R_UNLESS(size >= 0, ResultOutOfRange);
+        R_RETURN(this->DoCreateFile(path, size, static_cast<int>(option)));
+    }
+
+    Result CreateFile(const Path& path, s64 size) {
+        R_RETURN(this->CreateFile(path, size, CreateOption::None));
+    }
+
+    Result DeleteFile(const Path& path) {
+        R_RETURN(this->DoDeleteFile(path));
+    }
+
+    Result CreateDirectory(const Path& path) {
+        R_RETURN(this->DoCreateDirectory(path));
+    }
+
+    Result DeleteDirectory(const Path& path) {
+        R_RETURN(this->DoDeleteDirectory(path));
+    }
+
+    Result DeleteDirectoryRecursively(const Path& path) {
+        R_RETURN(this->DoDeleteDirectoryRecursively(path));
+    }
+
+    Result RenameFile(const Path& old_path, const Path& new_path) {
+        R_RETURN(this->DoRenameFile(old_path, new_path));
+    }
+
+    Result RenameDirectory(const Path& old_path, const Path& new_path) {
+        R_RETURN(this->DoRenameDirectory(old_path, new_path));
+    }
+
+    Result GetEntryType(DirectoryEntryType* out, const Path& path) {
+        R_RETURN(this->DoGetEntryType(out, path));
+    }
+
+    Result OpenFile(VirtualFile* out_file, const Path& path, OpenMode mode) {
+        R_UNLESS(out_file != nullptr, ResultNullptrArgument);
+        R_UNLESS(static_cast<u32>(mode & OpenMode::ReadWrite) != 0, ResultInvalidOpenMode);
+        R_UNLESS(static_cast<u32>(mode & ~OpenMode::All) == 0, ResultInvalidOpenMode);
+        R_RETURN(this->DoOpenFile(out_file, path, mode));
+    }
+
+    Result OpenDirectory(VirtualDir* out_dir, const Path& path, OpenDirectoryMode mode) {
+        R_UNLESS(out_dir != nullptr, ResultNullptrArgument);
+        R_UNLESS(static_cast<u64>(mode & OpenDirectoryMode::All) != 0, ResultInvalidOpenMode);
+        R_UNLESS(static_cast<u64>(
+                     mode & ~(OpenDirectoryMode::All | OpenDirectoryMode::NotRequireFileSize)) == 0,
+                 ResultInvalidOpenMode);
+        R_RETURN(this->DoOpenDirectory(out_dir, path, mode));
+    }
+
+    Result Commit() {
+        R_RETURN(this->DoCommit());
+    }
+
+    Result GetFreeSpaceSize(s64* out, const Path& path) {
+        R_UNLESS(out != nullptr, ResultNullptrArgument);
+        R_RETURN(this->DoGetFreeSpaceSize(out, path));
+    }
+
+    Result GetTotalSpaceSize(s64* out, const Path& path) {
+        R_UNLESS(out != nullptr, ResultNullptrArgument);
+        R_RETURN(this->DoGetTotalSpaceSize(out, path));
+    }
+
+    Result CleanDirectoryRecursively(const Path& path) {
+        R_RETURN(this->DoCleanDirectoryRecursively(path));
+    }
+
+    Result GetFileTimeStampRaw(FileTimeStampRaw* out, const Path& path) {
+        R_UNLESS(out != nullptr, ResultNullptrArgument);
+        R_RETURN(this->DoGetFileTimeStampRaw(out, path));
+    }
+
+    Result QueryEntry(char* dst, size_t dst_size, const char* src, size_t src_size, QueryId query,
+                      const Path& path) {
+        R_RETURN(this->DoQueryEntry(dst, dst_size, src, src_size, query, path));
+    }
+
+    // These aren't accessible as commands
+    Result CommitProvisionally(s64 counter) {
+        R_RETURN(this->DoCommitProvisionally(counter));
+    }
+
+    Result Rollback() {
+        R_RETURN(this->DoRollback());
+    }
+
+    Result Flush() {
+        R_RETURN(this->DoFlush());
+    }
+
+private:
+    Result DoCreateFile(const Path& path, s64 size, int flags) {
+        R_RETURN(backend.CreateFile(path.GetString(), size));
+    }
+
+    Result DoDeleteFile(const Path& path) {
+        R_RETURN(backend.DeleteFile(path.GetString()));
+    }
+
+    Result DoCreateDirectory(const Path& path) {
+        R_RETURN(backend.CreateDirectory(path.GetString()));
+    }
+
+    Result DoDeleteDirectory(const Path& path) {
+        R_RETURN(backend.DeleteDirectory(path.GetString()));
+    }
+
+    Result DoDeleteDirectoryRecursively(const Path& path) {
+        R_RETURN(backend.DeleteDirectoryRecursively(path.GetString()));
+    }
+
+    Result DoRenameFile(const Path& old_path, const Path& new_path) {
+        R_RETURN(backend.RenameFile(old_path.GetString(), new_path.GetString()));
+    }
+
+    Result DoRenameDirectory(const Path& old_path, const Path& new_path) {
+        R_RETURN(backend.RenameDirectory(old_path.GetString(), new_path.GetString()));
+    }
+
+    Result DoGetEntryType(DirectoryEntryType* out, const Path& path) {
+        R_RETURN(backend.GetEntryType(out, path.GetString()));
+    }
+
+    Result DoOpenFile(VirtualFile* out_file, const Path& path, OpenMode mode) {
+        R_RETURN(backend.OpenFile(out_file, path.GetString(), mode));
+    }
+
+    Result DoOpenDirectory(VirtualDir* out_directory, const Path& path, OpenDirectoryMode mode) {
+        R_RETURN(backend.OpenDirectory(out_directory, path.GetString()));
+    }
+
+    Result DoCommit() {
+        R_THROW(ResultNotImplemented);
+    }
+
+    Result DoGetFreeSpaceSize(s64* out, const Path& path) {
+        R_THROW(ResultNotImplemented);
+    }
+
+    Result DoGetTotalSpaceSize(s64* out, const Path& path) {
+        R_THROW(ResultNotImplemented);
+    }
+
+    Result DoCleanDirectoryRecursively(const Path& path) {
+        R_RETURN(backend.CleanDirectoryRecursively(path.GetString()));
+    }
+
+    Result DoGetFileTimeStampRaw(FileTimeStampRaw* out, const Path& path) {
+        R_RETURN(backend.GetFileTimeStampRaw(out, path.GetString()));
+    }
+
+    Result DoQueryEntry(char* dst, size_t dst_size, const char* src, size_t src_size, QueryId query,
+                        const Path& path) {
+        R_THROW(ResultNotImplemented);
+    }
+
+    // These aren't accessible as commands
+    Result DoCommitProvisionally(s64 counter) {
+        R_THROW(ResultNotImplemented);
+    }
+
+    Result DoRollback() {
+        R_THROW(ResultNotImplemented);
+    }
+
+    Result DoFlush() {
+        R_THROW(ResultNotImplemented);
+    }
+
+    Service::FileSystem::VfsDirectoryServiceWrapper backend;
+};
+
+} // namespace FileSys::Fsa

core/fs/fsmitm_romfsbuild.cpp

@@ -0,0 +1,354 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <cstring>
+#include <span>
+#include <string_view>
+#include "common/alignment.h"
+#include "common/assert.h"
+#include "core/file_sys/fsmitm_romfsbuild.h"
+#include "core/file_sys/ips_layer.h"
+#include "core/file_sys/vfs/vfs.h"
+#include "core/file_sys/vfs/vfs_vector.h"
+
+namespace FileSys {
+
+constexpr u64 FS_MAX_PATH = 0x301;
+
+constexpr u32 ROMFS_ENTRY_EMPTY = 0xFFFFFFFF;
+constexpr u32 ROMFS_FILEPARTITION_OFS = 0x200;
+
+// Types for building a RomFS.
+struct RomFSHeader {
+    u64 header_size;
+    u64 dir_hash_table_ofs;
+    u64 dir_hash_table_size;
+    u64 dir_table_ofs;
+    u64 dir_table_size;
+    u64 file_hash_table_ofs;
+    u64 file_hash_table_size;
+    u64 file_table_ofs;
+    u64 file_table_size;
+    u64 file_partition_ofs;
+};
+static_assert(sizeof(RomFSHeader) == 0x50, "RomFSHeader has incorrect size.");
+
+struct RomFSDirectoryEntry {
+    u32 parent;
+    u32 sibling;
+    u32 child;
+    u32 file;
+    u32 hash;
+    u32 name_size;
+};
+static_assert(sizeof(RomFSDirectoryEntry) == 0x18, "RomFSDirectoryEntry has incorrect size.");
+
+struct RomFSFileEntry {
+    u32 parent;
+    u32 sibling;
+    u64 offset;
+    u64 size;
+    u32 hash;
+    u32 name_size;
+};
+static_assert(sizeof(RomFSFileEntry) == 0x20, "RomFSFileEntry has incorrect size.");
+
+struct RomFSBuildFileContext;
+
+struct RomFSBuildDirectoryContext {
+    std::string path;
+    u32 cur_path_ofs = 0;
+    u32 path_len = 0;
+    u32 entry_offset = 0;
+    std::shared_ptr<RomFSBuildDirectoryContext> parent;
+    std::shared_ptr<RomFSBuildDirectoryContext> child;
+    std::shared_ptr<RomFSBuildDirectoryContext> sibling;
+    std::shared_ptr<RomFSBuildFileContext> file;
+};
+
+struct RomFSBuildFileContext {
+    std::string path;
+    u32 cur_path_ofs = 0;
+    u32 path_len = 0;
+    u32 entry_offset = 0;
+    u64 offset = 0;
+    u64 size = 0;
+    std::shared_ptr<RomFSBuildDirectoryContext> parent;
+    std::shared_ptr<RomFSBuildFileContext> sibling;
+    VirtualFile source;
+};
+
+static u32 romfs_calc_path_hash(u32 parent, std::string_view path, u32 start,
+                                std::size_t path_len) {
+    u32 hash = parent ^ 123456789;
+    for (u32 i = 0; i < path_len; i++) {
+        hash = (hash >> 5) | (hash << 27);
+        hash ^= path[start + i];
+    }
+
+    return hash;
+}
+
+static u64 romfs_get_hash_table_count(u64 num_entries) {
+    if (num_entries < 3) {
+        return 3;
+    }
+
+    if (num_entries < 19) {
+        return num_entries | 1;
+    }
+
+    u64 count = num_entries;
+    while (count % 2 == 0 || count % 3 == 0 || count % 5 == 0 || count % 7 == 0 ||
+           count % 11 == 0 || count % 13 == 0 || count % 17 == 0) {
+        count++;
+    }
+    return count;
+}
+
+void RomFSBuildContext::VisitDirectory(VirtualDir romfs_dir, VirtualDir ext_dir,
+                                       std::shared_ptr<RomFSBuildDirectoryContext> parent) {
+    for (auto& child_romfs_file : romfs_dir->GetFiles()) {
+        const auto name = child_romfs_file->GetName();
+        const auto child = std::make_shared<RomFSBuildFileContext>();
+        // Set child's path.
+        child->cur_path_ofs = parent->path_len + 1;
+        child->path_len = child->cur_path_ofs + static_cast<u32>(name.size());
+        child->path = parent->path + "/" + name;
+
+        if (ext_dir != nullptr && ext_dir->GetFile(name + ".stub") != nullptr) {
+            continue;
+        }
+
+        // Sanity check on path_len
+        ASSERT(child->path_len < FS_MAX_PATH);
+
+        child->source = std::move(child_romfs_file);
+
+        if (ext_dir != nullptr) {
+            if (const auto ips = ext_dir->GetFile(name + ".ips")) {
+                if (auto patched = PatchIPS(child->source, ips)) {
+                    child->source = std::move(patched);
+                }
+            }
+        }
+
+        child->size = child->source->GetSize();
+
+        AddFile(parent, std::move(child));
+    }
+
+    for (auto& child_romfs_dir : romfs_dir->GetSubdirectories()) {
+        const auto name = child_romfs_dir->GetName();
+        const auto child = std::make_shared<RomFSBuildDirectoryContext>();
+        // Set child's path.
+        child->cur_path_ofs = parent->path_len + 1;
+        child->path_len = child->cur_path_ofs + static_cast<u32>(name.size());
+        child->path = parent->path + "/" + name;
+
+        if (ext_dir != nullptr && ext_dir->GetFile(name + ".stub") != nullptr) {
+            continue;
+        }
+
+        // Sanity check on path_len
+        ASSERT(child->path_len < FS_MAX_PATH);
+
+        if (!AddDirectory(parent, child)) {
+            continue;
+        }
+
+        auto child_ext_dir = ext_dir != nullptr ? ext_dir->GetSubdirectory(name) : nullptr;
+        this->VisitDirectory(child_romfs_dir, child_ext_dir, child);
+    }
+}
+
+bool RomFSBuildContext::AddDirectory(std::shared_ptr<RomFSBuildDirectoryContext> parent_dir_ctx,
+                                     std::shared_ptr<RomFSBuildDirectoryContext> dir_ctx) {
+    // Add a new directory.
+    num_dirs++;
+    dir_table_size +=
+        sizeof(RomFSDirectoryEntry) + Common::AlignUp(dir_ctx->path_len - dir_ctx->cur_path_ofs, 4);
+    dir_ctx->parent = std::move(parent_dir_ctx);
+    directories.emplace_back(std::move(dir_ctx));
+
+    return true;
+}
+
+bool RomFSBuildContext::AddFile(std::shared_ptr<RomFSBuildDirectoryContext> parent_dir_ctx,
+                                std::shared_ptr<RomFSBuildFileContext> file_ctx) {
+    // Add a new file.
+    num_files++;
+    file_table_size +=
+        sizeof(RomFSFileEntry) + Common::AlignUp(file_ctx->path_len - file_ctx->cur_path_ofs, 4);
+    file_ctx->parent = std::move(parent_dir_ctx);
+    files.emplace_back(std::move(file_ctx));
+
+    return true;
+}
+
+RomFSBuildContext::RomFSBuildContext(VirtualDir base_, VirtualDir ext_)
+    : base(std::move(base_)), ext(std::move(ext_)) {
+    root = std::make_shared<RomFSBuildDirectoryContext>();
+    root->path = "\0";
+    directories.emplace_back(root);
+    num_dirs = 1;
+    dir_table_size = 0x18;
+
+    VisitDirectory(base, ext, root);
+}
+
+RomFSBuildContext::~RomFSBuildContext() = default;
+
+std::vector<std::pair<u64, VirtualFile>> RomFSBuildContext::Build() {
+    const u64 dir_hash_table_entry_count = romfs_get_hash_table_count(num_dirs);
+    const u64 file_hash_table_entry_count = romfs_get_hash_table_count(num_files);
+    dir_hash_table_size = 4 * dir_hash_table_entry_count;
+    file_hash_table_size = 4 * file_hash_table_entry_count;
+
+    // Assign metadata pointers.
+    RomFSHeader header{};
+
+    std::vector<u8> metadata(file_hash_table_size + file_table_size + dir_hash_table_size +
+                             dir_table_size);
+    u32* const dir_hash_table_pointer = reinterpret_cast<u32*>(metadata.data());
+    u8* const dir_table_pointer = metadata.data() + dir_hash_table_size;
+    u32* const file_hash_table_pointer =
+        reinterpret_cast<u32*>(metadata.data() + dir_hash_table_size + dir_table_size);
+    u8* const file_table_pointer =
+        metadata.data() + dir_hash_table_size + dir_table_size + file_hash_table_size;
+
+    std::span<u32> dir_hash_table(dir_hash_table_pointer, dir_hash_table_entry_count);
+    std::span<u32> file_hash_table(file_hash_table_pointer, file_hash_table_entry_count);
+    std::span<u8> dir_table(dir_table_pointer, dir_table_size);
+    std::span<u8> file_table(file_table_pointer, file_table_size);
+
+    // Initialize hash tables.
+    std::memset(dir_hash_table.data(), 0xFF, dir_hash_table.size_bytes());
+    std::memset(file_hash_table.data(), 0xFF, file_hash_table.size_bytes());
+
+    // Sort tables by name.
+    std::sort(files.begin(), files.end(),
+              [](const auto& a, const auto& b) { return a->path < b->path; });
+    std::sort(directories.begin(), directories.end(),
+              [](const auto& a, const auto& b) { return a->path < b->path; });
+
+    // Determine file offsets.
+    u32 entry_offset = 0;
+    std::shared_ptr<RomFSBuildFileContext> prev_file = nullptr;
+    for (const auto& cur_file : files) {
+        file_partition_size = Common::AlignUp(file_partition_size, 16);
+        cur_file->offset = file_partition_size;
+        file_partition_size += cur_file->size;
+        cur_file->entry_offset = entry_offset;
+        entry_offset +=
+            static_cast<u32>(sizeof(RomFSFileEntry) +
+                             Common::AlignUp(cur_file->path_len - cur_file->cur_path_ofs, 4));
+        prev_file = cur_file;
+    }
+    // Assign deferred parent/sibling ownership.
+    for (auto it = files.rbegin(); it != files.rend(); ++it) {
+        auto& cur_file = *it;
+        cur_file->sibling = cur_file->parent->file;
+        cur_file->parent->file = cur_file;
+    }
+
+    // Determine directory offsets.
+    entry_offset = 0;
+    for (const auto& cur_dir : directories) {
+        cur_dir->entry_offset = entry_offset;
+        entry_offset +=
+            static_cast<u32>(sizeof(RomFSDirectoryEntry) +
+                             Common::AlignUp(cur_dir->path_len - cur_dir->cur_path_ofs, 4));
+    }
+    // Assign deferred parent/sibling ownership.
+    for (auto it = directories.rbegin(); (*it) != root; ++it) {
+        auto& cur_dir = *it;
+        cur_dir->sibling = cur_dir->parent->child;
+        cur_dir->parent->child = cur_dir;
+    }
+
+    // Create output map.
+    std::vector<std::pair<u64, VirtualFile>> out;
+    out.reserve(num_files + 2);
+
+    // Set header fields.
+    header.header_size = sizeof(RomFSHeader);
+    header.file_hash_table_size = file_hash_table_size;
+    header.file_table_size = file_table_size;
+    header.dir_hash_table_size = dir_hash_table_size;
+    header.dir_table_size = dir_table_size;
+    header.file_partition_ofs = ROMFS_FILEPARTITION_OFS;
+    header.dir_hash_table_ofs = Common::AlignUp(header.file_partition_ofs + file_partition_size, 4);
+    header.dir_table_ofs = header.dir_hash_table_ofs + header.dir_hash_table_size;
+    header.file_hash_table_ofs = header.dir_table_ofs + header.dir_table_size;
+    header.file_table_ofs = header.file_hash_table_ofs + header.file_hash_table_size;
+
+    std::vector<u8> header_data(sizeof(RomFSHeader));
+    std::memcpy(header_data.data(), &header, header_data.size());
+    out.emplace_back(0, std::make_shared<VectorVfsFile>(std::move(header_data)));
+
+    // Populate file tables.
+    for (const auto& cur_file : files) {
+        RomFSFileEntry cur_entry{};
+
+        cur_entry.parent = cur_file->parent->entry_offset;
+        cur_entry.sibling =
+            cur_file->sibling == nullptr ? ROMFS_ENTRY_EMPTY : cur_file->sibling->entry_offset;
+        cur_entry.offset = cur_file->offset;
+        cur_entry.size = cur_file->size;
+
+        const auto name_size = cur_file->path_len - cur_file->cur_path_ofs;
+        const auto hash = romfs_calc_path_hash(cur_file->parent->entry_offset, cur_file->path,
+                                               cur_file->cur_path_ofs, name_size);
+        cur_entry.hash = file_hash_table[hash % file_hash_table_entry_count];
+        file_hash_table[hash % file_hash_table_entry_count] = cur_file->entry_offset;
+
+        cur_entry.name_size = name_size;
+
+        out.emplace_back(cur_file->offset + ROMFS_FILEPARTITION_OFS, std::move(cur_file->source));
+        std::memcpy(file_table.data() + cur_file->entry_offset, &cur_entry, sizeof(RomFSFileEntry));
+        std::memset(file_table.data() + cur_file->entry_offset + sizeof(RomFSFileEntry), 0,
+                    Common::AlignUp(cur_entry.name_size, 4));
+        std::memcpy(file_table.data() + cur_file->entry_offset + sizeof(RomFSFileEntry),
+                    cur_file->path.data() + cur_file->cur_path_ofs, name_size);
+    }
+
+    // Populate dir tables.
+    for (const auto& cur_dir : directories) {
+        RomFSDirectoryEntry cur_entry{};
+
+        cur_entry.parent = cur_dir == root ? 0 : cur_dir->parent->entry_offset;
+        cur_entry.sibling =
+            cur_dir->sibling == nullptr ? ROMFS_ENTRY_EMPTY : cur_dir->sibling->entry_offset;
+        cur_entry.child =
+            cur_dir->child == nullptr ? ROMFS_ENTRY_EMPTY : cur_dir->child->entry_offset;
+        cur_entry.file = cur_dir->file == nullptr ? ROMFS_ENTRY_EMPTY : cur_dir->file->entry_offset;
+
+        const auto name_size = cur_dir->path_len - cur_dir->cur_path_ofs;
+        const auto hash = romfs_calc_path_hash(cur_dir == root ? 0 : cur_dir->parent->entry_offset,
+                                               cur_dir->path, cur_dir->cur_path_ofs, name_size);
+        cur_entry.hash = dir_hash_table[hash % dir_hash_table_entry_count];
+        dir_hash_table[hash % dir_hash_table_entry_count] = cur_dir->entry_offset;
+
+        cur_entry.name_size = name_size;
+
+        std::memcpy(dir_table.data() + cur_dir->entry_offset, &cur_entry,
+                    sizeof(RomFSDirectoryEntry));
+        std::memset(dir_table.data() + cur_dir->entry_offset + sizeof(RomFSDirectoryEntry), 0,
+                    Common::AlignUp(cur_entry.name_size, 4));
+        std::memcpy(dir_table.data() + cur_dir->entry_offset + sizeof(RomFSDirectoryEntry),
+                    cur_dir->path.data() + cur_dir->cur_path_ofs, name_size);
+    }
+
+    // Write metadata.
+    out.emplace_back(header.dir_hash_table_ofs,
+                     std::make_shared<VectorVfsFile>(std::move(metadata)));
+
+    // Sort the output.
+    std::sort(out.begin(), out.end(),
+              [](const auto& a, const auto& b) { return a.first < b.first; });
+
+    return out;
+}
+
+} // namespace FileSys

core/fs/fsmitm_romfsbuild.h

@@ -0,0 +1,50 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <map>
+#include <memory>
+#include <string>
+#include "common/common_types.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+
+struct RomFSBuildDirectoryContext;
+struct RomFSBuildFileContext;
+struct RomFSDirectoryEntry;
+struct RomFSFileEntry;
+
+class RomFSBuildContext {
+public:
+    explicit RomFSBuildContext(VirtualDir base, VirtualDir ext = nullptr);
+    ~RomFSBuildContext();
+
+    // This finalizes the context.
+    std::vector<std::pair<u64, VirtualFile>> Build();
+
+private:
+    VirtualDir base;
+    VirtualDir ext;
+    std::shared_ptr<RomFSBuildDirectoryContext> root;
+    std::vector<std::shared_ptr<RomFSBuildDirectoryContext>> directories;
+    std::vector<std::shared_ptr<RomFSBuildFileContext>> files;
+    u64 num_dirs = 0;
+    u64 num_files = 0;
+    u64 dir_table_size = 0;
+    u64 file_table_size = 0;
+    u64 dir_hash_table_size = 0;
+    u64 file_hash_table_size = 0;
+    u64 file_partition_size = 0;
+
+    void VisitDirectory(VirtualDir filesys, VirtualDir ext_dir,
+                        std::shared_ptr<RomFSBuildDirectoryContext> parent);
+
+    bool AddDirectory(std::shared_ptr<RomFSBuildDirectoryContext> parent_dir_ctx,
+                      std::shared_ptr<RomFSBuildDirectoryContext> dir_ctx);
+    bool AddFile(std::shared_ptr<RomFSBuildDirectoryContext> parent_dir_ctx,
+                 std::shared_ptr<RomFSBuildFileContext> file_ctx);
+};
+
+} // namespace FileSys

core/fs/fssrv/fssrv_sf_path.h

@@ -0,0 +1,36 @@
+// SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fs_directory.h"
+
+namespace FileSys::Sf {
+
+struct Path {
+    char str[EntryNameLengthMax + 1];
+
+    static constexpr Path Encode(const char* p) {
+        Path path = {};
+        for (size_t i = 0; i < sizeof(path) - 1; i++) {
+            path.str[i] = p[i];
+            if (p[i] == '\x00') {
+                break;
+            }
+        }
+        return path;
+    }
+
+    static constexpr size_t GetPathLength(const Path& path) {
+        size_t len = 0;
+        for (size_t i = 0; i < sizeof(path) - 1 && path.str[i] != '\x00'; i++) {
+            len++;
+        }
+        return len;
+    }
+};
+static_assert(std::is_trivially_copyable_v<Path>, "Path must be trivially copyable.");
+
+using FspPath = Path;
+
+} // namespace FileSys::Sf

core/fs/fssystem/fs_i_storage.h

@@ -0,0 +1,58 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/overflow.h"
+#include "core/file_sys/errors.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+
+class IStorage : public VfsFile {
+public:
+    virtual std::string GetName() const override {
+        return {};
+    }
+
+    virtual VirtualDir GetContainingDirectory() const override {
+        return {};
+    }
+
+    virtual bool IsWritable() const override {
+        return true;
+    }
+
+    virtual bool IsReadable() const override {
+        return true;
+    }
+
+    virtual bool Resize(size_t size) override {
+        return false;
+    }
+
+    virtual bool Rename(std::string_view name) override {
+        return false;
+    }
+
+    static inline Result CheckAccessRange(s64 offset, s64 size, s64 total_size) {
+        R_UNLESS(offset >= 0, ResultInvalidOffset);
+        R_UNLESS(size >= 0, ResultInvalidSize);
+        R_UNLESS(Common::WrappingAdd(offset, size) >= offset, ResultOutOfRange);
+        R_UNLESS(offset + size <= total_size, ResultOutOfRange);
+        R_SUCCEED();
+    }
+};
+
+class IReadOnlyStorage : public IStorage {
+public:
+    virtual bool IsWritable() const override {
+        return false;
+    }
+
+    virtual size_t Write(const u8* buffer, size_t size, size_t offset) override {
+        return 0;
+    }
+};
+
+} // namespace FileSys

core/fs/fssystem/fs_types.h

@@ -0,0 +1,46 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_funcs.h"
+
+namespace FileSys {
+
+struct Int64 {
+    u32 low;
+    u32 high;
+
+    constexpr void Set(s64 v) {
+        this->low = static_cast<u32>((v & static_cast<u64>(0x00000000FFFFFFFFULL)) >> 0);
+        this->high = static_cast<u32>((v & static_cast<u64>(0xFFFFFFFF00000000ULL)) >> 32);
+    }
+
+    constexpr s64 Get() const {
+        return (static_cast<s64>(this->high) << 32) | (static_cast<s64>(this->low));
+    }
+
+    constexpr Int64& operator=(s64 v) {
+        this->Set(v);
+        return *this;
+    }
+
+    constexpr operator s64() const {
+        return this->Get();
+    }
+};
+
+struct HashSalt {
+    static constexpr size_t Size = 32;
+
+    std::array<u8, Size> value;
+};
+static_assert(std::is_trivial_v<HashSalt>);
+static_assert(sizeof(HashSalt) == HashSalt::Size);
+
+constexpr inline size_t IntegrityMinLayerCount = 2;
+constexpr inline size_t IntegrityMaxLayerCount = 7;
+constexpr inline size_t IntegrityLayerCountSave = 5;
+constexpr inline size_t IntegrityLayerCountSaveDataMeta = 4;
+
+} // namespace FileSys

core/fs/fssystem/fssystem_aes_ctr_counter_extended_storage.cpp

@@ -0,0 +1,251 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/fssystem/fssystem_aes_ctr_counter_extended_storage.h"
+#include "core/file_sys/fssystem/fssystem_aes_ctr_storage.h"
+#include "core/file_sys/fssystem/fssystem_nca_header.h"
+#include "core/file_sys/vfs/vfs_offset.h"
+
+namespace FileSys {
+
+namespace {
+
+class SoftwareDecryptor final : public AesCtrCounterExtendedStorage::IDecryptor {
+public:
+    virtual void Decrypt(
+        u8* buf, size_t buf_size, const std::array<u8, AesCtrCounterExtendedStorage::KeySize>& key,
+        const std::array<u8, AesCtrCounterExtendedStorage::IvSize>& iv) override final;
+};
+
+} // namespace
+
+Result AesCtrCounterExtendedStorage::CreateSoftwareDecryptor(std::unique_ptr<IDecryptor>* out) {
+    std::unique_ptr<IDecryptor> decryptor = std::make_unique<SoftwareDecryptor>();
+    R_UNLESS(decryptor != nullptr, ResultAllocationMemoryFailedInAesCtrCounterExtendedStorageA);
+    *out = std::move(decryptor);
+    R_SUCCEED();
+}
+
+Result AesCtrCounterExtendedStorage::Initialize(const void* key, size_t key_size, u32 secure_value,
+                                                VirtualFile data_storage,
+                                                VirtualFile table_storage) {
+    // Read and verify the bucket tree header.
+    BucketTree::Header header;
+    table_storage->ReadObject(std::addressof(header), 0);
+    R_TRY(header.Verify());
+
+    // Determine extents.
+    const auto node_storage_size = QueryNodeStorageSize(header.entry_count);
+    const auto entry_storage_size = QueryEntryStorageSize(header.entry_count);
+    const auto node_storage_offset = QueryHeaderStorageSize();
+    const auto entry_storage_offset = node_storage_offset + node_storage_size;
+
+    // Create a software decryptor.
+    std::unique_ptr<IDecryptor> sw_decryptor;
+    R_TRY(CreateSoftwareDecryptor(std::addressof(sw_decryptor)));
+
+    // Initialize.
+    R_RETURN(this->Initialize(
+        key, key_size, secure_value, 0, data_storage,
+        std::make_shared<OffsetVfsFile>(table_storage, node_storage_size, node_storage_offset),
+        std::make_shared<OffsetVfsFile>(table_storage, entry_storage_size, entry_storage_offset),
+        header.entry_count, std::move(sw_decryptor)));
+}
+
+Result AesCtrCounterExtendedStorage::Initialize(const void* key, size_t key_size, u32 secure_value,
+                                                s64 counter_offset, VirtualFile data_storage,
+                                                VirtualFile node_storage, VirtualFile entry_storage,
+                                                s32 entry_count,
+                                                std::unique_ptr<IDecryptor>&& decryptor) {
+    // Validate preconditions.
+    ASSERT(key != nullptr);
+    ASSERT(key_size == KeySize);
+    ASSERT(counter_offset >= 0);
+    ASSERT(decryptor != nullptr);
+
+    // Initialize the bucket tree table.
+    if (entry_count > 0) {
+        R_TRY(
+            m_table.Initialize(node_storage, entry_storage, NodeSize, sizeof(Entry), entry_count));
+    } else {
+        m_table.Initialize(NodeSize, 0);
+    }
+
+    // Set members.
+    m_data_storage = data_storage;
+    std::memcpy(m_key.data(), key, key_size);
+    m_secure_value = secure_value;
+    m_counter_offset = counter_offset;
+    m_decryptor = std::move(decryptor);
+
+    R_SUCCEED();
+}
+
+void AesCtrCounterExtendedStorage::Finalize() {
+    if (this->IsInitialized()) {
+        m_table.Finalize();
+        m_data_storage = VirtualFile();
+    }
+}
+
+Result AesCtrCounterExtendedStorage::GetEntryList(Entry* out_entries, s32* out_entry_count,
+                                                  s32 entry_count, s64 offset, s64 size) {
+    // Validate pre-conditions.
+    ASSERT(offset >= 0);
+    ASSERT(size >= 0);
+    ASSERT(this->IsInitialized());
+
+    // Clear the out count.
+    R_UNLESS(out_entry_count != nullptr, ResultNullptrArgument);
+    *out_entry_count = 0;
+
+    // Succeed if there's no range.
+    R_SUCCEED_IF(size == 0);
+
+    // If we have an output array, we need it to be non-null.
+    R_UNLESS(out_entries != nullptr || entry_count == 0, ResultNullptrArgument);
+
+    // Check that our range is valid.
+    BucketTree::Offsets table_offsets;
+    R_TRY(m_table.GetOffsets(std::addressof(table_offsets)));
+
+    R_UNLESS(table_offsets.IsInclude(offset, size), ResultOutOfRange);
+
+    // Find the offset in our tree.
+    BucketTree::Visitor visitor;
+    R_TRY(m_table.Find(std::addressof(visitor), offset));
+    {
+        const auto entry_offset = visitor.Get<Entry>()->GetOffset();
+        R_UNLESS(0 <= entry_offset && table_offsets.IsInclude(entry_offset),
+                 ResultInvalidAesCtrCounterExtendedEntryOffset);
+    }
+
+    // Prepare to loop over entries.
+    const auto end_offset = offset + static_cast<s64>(size);
+    s32 count = 0;
+
+    auto cur_entry = *visitor.Get<Entry>();
+    while (cur_entry.GetOffset() < end_offset) {
+        // Try to write the entry to the out list.
+        if (entry_count != 0) {
+            if (count >= entry_count) {
+                break;
+            }
+            std::memcpy(out_entries + count, std::addressof(cur_entry), sizeof(Entry));
+        }
+
+        count++;
+
+        // Advance.
+        if (visitor.CanMoveNext()) {
+            R_TRY(visitor.MoveNext());
+            cur_entry = *visitor.Get<Entry>();
+        } else {
+            break;
+        }
+    }
+
+    // Write the output count.
+    *out_entry_count = count;
+    R_SUCCEED();
+}
+
+size_t AesCtrCounterExtendedStorage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Validate preconditions.
+    ASSERT(this->IsInitialized());
+
+    // Allow zero size.
+    if (size == 0) {
+        return size;
+    }
+
+    // Validate arguments.
+    ASSERT(buffer != nullptr);
+    ASSERT(Common::IsAligned(offset, BlockSize));
+    ASSERT(Common::IsAligned(size, BlockSize));
+
+    BucketTree::Offsets table_offsets;
+    ASSERT(R_SUCCEEDED(m_table.GetOffsets(std::addressof(table_offsets))));
+
+    ASSERT(table_offsets.IsInclude(offset, size));
+
+    // Read the data.
+    m_data_storage->Read(buffer, size, offset);
+
+    // Find the offset in our tree.
+    BucketTree::Visitor visitor;
+    ASSERT(R_SUCCEEDED(m_table.Find(std::addressof(visitor), offset)));
+    {
+        const auto entry_offset = visitor.Get<Entry>()->GetOffset();
+        ASSERT(Common::IsAligned(entry_offset, BlockSize));
+        ASSERT(0 <= entry_offset && table_offsets.IsInclude(entry_offset));
+    }
+
+    // Prepare to read in chunks.
+    u8* cur_data = static_cast<u8*>(buffer);
+    auto cur_offset = offset;
+    const auto end_offset = offset + static_cast<s64>(size);
+
+    while (cur_offset < end_offset) {
+        // Get the current entry.
+        const auto cur_entry = *visitor.Get<Entry>();
+
+        // Get and validate the entry's offset.
+        const auto cur_entry_offset = cur_entry.GetOffset();
+        ASSERT(static_cast<size_t>(cur_entry_offset) <= cur_offset);
+
+        // Get and validate the next entry offset.
+        s64 next_entry_offset;
+        if (visitor.CanMoveNext()) {
+            ASSERT(R_SUCCEEDED(visitor.MoveNext()));
+            next_entry_offset = visitor.Get<Entry>()->GetOffset();
+            ASSERT(table_offsets.IsInclude(next_entry_offset));
+        } else {
+            next_entry_offset = table_offsets.end_offset;
+        }
+        ASSERT(Common::IsAligned(next_entry_offset, BlockSize));
+        ASSERT(cur_offset < static_cast<size_t>(next_entry_offset));
+
+        // Get the offset of the entry in the data we read.
+        const auto data_offset = cur_offset - cur_entry_offset;
+        const auto data_size = (next_entry_offset - cur_entry_offset) - data_offset;
+        ASSERT(data_size > 0);
+
+        // Determine how much is left.
+        const auto remaining_size = end_offset - cur_offset;
+        const auto cur_size = static_cast<size_t>(std::min(remaining_size, data_size));
+        ASSERT(cur_size <= size);
+
+        // If necessary, perform decryption.
+        if (cur_entry.encryption_value == Entry::Encryption::Encrypted) {
+            // Make the CTR for the data we're decrypting.
+            const auto counter_offset = m_counter_offset + cur_entry_offset + data_offset;
+            NcaAesCtrUpperIv upper_iv = {
+                .part = {.generation = static_cast<u32>(cur_entry.generation),
+                         .secure_value = m_secure_value}};
+
+            std::array<u8, IvSize> iv;
+            AesCtrStorage::MakeIv(iv.data(), IvSize, upper_iv.value, counter_offset);
+
+            // Decrypt.
+            m_decryptor->Decrypt(cur_data, cur_size, m_key, iv);
+        }
+
+        // Advance.
+        cur_data += cur_size;
+        cur_offset += cur_size;
+    }
+
+    return size;
+}
+
+void SoftwareDecryptor::Decrypt(u8* buf, size_t buf_size,
+                                const std::array<u8, AesCtrCounterExtendedStorage::KeySize>& key,
+                                const std::array<u8, AesCtrCounterExtendedStorage::IvSize>& iv) {
+    Core::Crypto::AESCipher<Core::Crypto::Key128, AesCtrCounterExtendedStorage::KeySize> cipher(
+        key, Core::Crypto::Mode::CTR);
+    cipher.SetIV(iv);
+    cipher.Transcode(buf, buf_size, buf, Core::Crypto::Op::Decrypt);
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_aes_ctr_counter_extended_storage.h

@@ -0,0 +1,114 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <optional>
+
+#include "common/literals.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree.h"
+
+namespace FileSys {
+
+using namespace Common::Literals;
+
+class AesCtrCounterExtendedStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(AesCtrCounterExtendedStorage);
+    YUZU_NON_MOVEABLE(AesCtrCounterExtendedStorage);
+
+public:
+    static constexpr size_t BlockSize = 0x10;
+    static constexpr size_t KeySize = 0x10;
+    static constexpr size_t IvSize = 0x10;
+    static constexpr size_t NodeSize = 16_KiB;
+
+    class IDecryptor {
+    public:
+        virtual ~IDecryptor() {}
+        virtual void Decrypt(u8* buf, size_t buf_size, const std::array<u8, KeySize>& key,
+                             const std::array<u8, IvSize>& iv) = 0;
+    };
+
+    struct Entry {
+        enum class Encryption : u8 {
+            Encrypted = 0,
+            NotEncrypted = 1,
+        };
+
+        std::array<u8, sizeof(s64)> offset;
+        Encryption encryption_value;
+        std::array<u8, 3> reserved;
+        s32 generation;
+
+        void SetOffset(s64 value) {
+            std::memcpy(this->offset.data(), std::addressof(value), sizeof(s64));
+        }
+
+        s64 GetOffset() const {
+            s64 value;
+            std::memcpy(std::addressof(value), this->offset.data(), sizeof(s64));
+            return value;
+        }
+    };
+    static_assert(sizeof(Entry) == 0x10);
+    static_assert(alignof(Entry) == 4);
+    static_assert(std::is_trivial_v<Entry>);
+
+public:
+    static constexpr s64 QueryHeaderStorageSize() {
+        return BucketTree::QueryHeaderStorageSize();
+    }
+
+    static constexpr s64 QueryNodeStorageSize(s32 entry_count) {
+        return BucketTree::QueryNodeStorageSize(NodeSize, sizeof(Entry), entry_count);
+    }
+
+    static constexpr s64 QueryEntryStorageSize(s32 entry_count) {
+        return BucketTree::QueryEntryStorageSize(NodeSize, sizeof(Entry), entry_count);
+    }
+
+    static Result CreateSoftwareDecryptor(std::unique_ptr<IDecryptor>* out);
+
+public:
+    AesCtrCounterExtendedStorage()
+        : m_table(), m_data_storage(), m_secure_value(), m_counter_offset(), m_decryptor() {}
+    virtual ~AesCtrCounterExtendedStorage() {
+        this->Finalize();
+    }
+
+    Result Initialize(const void* key, size_t key_size, u32 secure_value, s64 counter_offset,
+                      VirtualFile data_storage, VirtualFile node_storage, VirtualFile entry_storage,
+                      s32 entry_count, std::unique_ptr<IDecryptor>&& decryptor);
+    void Finalize();
+
+    bool IsInitialized() const {
+        return m_table.IsInitialized();
+    }
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+
+    virtual size_t GetSize() const override {
+        BucketTree::Offsets offsets;
+        ASSERT(R_SUCCEEDED(m_table.GetOffsets(std::addressof(offsets))));
+
+        return offsets.end_offset;
+    }
+
+    Result GetEntryList(Entry* out_entries, s32* out_entry_count, s32 entry_count, s64 offset,
+                        s64 size);
+
+private:
+    Result Initialize(const void* key, size_t key_size, u32 secure_value, VirtualFile data_storage,
+                      VirtualFile table_storage);
+
+private:
+    mutable BucketTree m_table;
+    VirtualFile m_data_storage;
+    std::array<u8, KeySize> m_key;
+    u32 m_secure_value;
+    s64 m_counter_offset;
+    std::unique_ptr<IDecryptor> m_decryptor;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_aes_ctr_storage.cpp

@@ -0,0 +1,129 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/alignment.h"
+#include "common/swap.h"
+#include "core/file_sys/fssystem/fssystem_aes_ctr_storage.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+#include "core/file_sys/fssystem/fssystem_utility.h"
+
+namespace FileSys {
+
+void AesCtrStorage::MakeIv(void* dst, size_t dst_size, u64 upper, s64 offset) {
+    ASSERT(dst != nullptr);
+    ASSERT(dst_size == IvSize);
+    ASSERT(offset >= 0);
+
+    const uintptr_t out_addr = reinterpret_cast<uintptr_t>(dst);
+
+    *reinterpret_cast<u64_be*>(out_addr + 0) = upper;
+    *reinterpret_cast<s64_be*>(out_addr + sizeof(u64)) = static_cast<s64>(offset / BlockSize);
+}
+
+AesCtrStorage::AesCtrStorage(VirtualFile base, const void* key, size_t key_size, const void* iv,
+                             size_t iv_size)
+    : m_base_storage(std::move(base)) {
+    ASSERT(m_base_storage != nullptr);
+    ASSERT(key != nullptr);
+    ASSERT(iv != nullptr);
+    ASSERT(key_size == KeySize);
+    ASSERT(iv_size == IvSize);
+
+    std::memcpy(m_key.data(), key, KeySize);
+    std::memcpy(m_iv.data(), iv, IvSize);
+
+    m_cipher.emplace(m_key, Core::Crypto::Mode::CTR);
+}
+
+size_t AesCtrStorage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Allow zero-size reads.
+    if (size == 0) {
+        return size;
+    }
+
+    // Ensure buffer is valid.
+    ASSERT(buffer != nullptr);
+
+    // We can only read at block aligned offsets.
+    ASSERT(Common::IsAligned(offset, BlockSize));
+    ASSERT(Common::IsAligned(size, BlockSize));
+
+    // Read the data.
+    m_base_storage->Read(buffer, size, offset);
+
+    // Setup the counter.
+    std::array<u8, IvSize> ctr;
+    std::memcpy(ctr.data(), m_iv.data(), IvSize);
+    AddCounter(ctr.data(), IvSize, offset / BlockSize);
+
+    // Decrypt.
+    m_cipher->SetIV(ctr);
+    m_cipher->Transcode(buffer, size, buffer, Core::Crypto::Op::Decrypt);
+
+    return size;
+}
+
+size_t AesCtrStorage::Write(const u8* buffer, size_t size, size_t offset) {
+    // Allow zero-size writes.
+    if (size == 0) {
+        return size;
+    }
+
+    // Ensure buffer is valid.
+    ASSERT(buffer != nullptr);
+
+    // We can only write at block aligned offsets.
+    ASSERT(Common::IsAligned(offset, BlockSize));
+    ASSERT(Common::IsAligned(size, BlockSize));
+
+    // Get a pooled buffer.
+    PooledBuffer pooled_buffer;
+    const bool use_work_buffer = true;
+    if (use_work_buffer) {
+        pooled_buffer.Allocate(size, BlockSize);
+    }
+
+    // Setup the counter.
+    std::array<u8, IvSize> ctr;
+    std::memcpy(ctr.data(), m_iv.data(), IvSize);
+    AddCounter(ctr.data(), IvSize, offset / BlockSize);
+
+    // Loop until all data is written.
+    size_t remaining = size;
+    s64 cur_offset = 0;
+    while (remaining > 0) {
+        // Determine data we're writing and where.
+        const size_t write_size =
+            use_work_buffer ? std::min(pooled_buffer.GetSize(), remaining) : remaining;
+
+        void* write_buf;
+        if (use_work_buffer) {
+            write_buf = pooled_buffer.GetBuffer();
+        } else {
+            write_buf = const_cast<u8*>(buffer);
+        }
+
+        // Encrypt the data.
+        m_cipher->SetIV(ctr);
+        m_cipher->Transcode(buffer, write_size, reinterpret_cast<u8*>(write_buf),
+                            Core::Crypto::Op::Encrypt);
+
+        // Write the encrypted data.
+        m_base_storage->Write(reinterpret_cast<u8*>(write_buf), write_size, offset + cur_offset);
+
+        // Advance.
+        cur_offset += write_size;
+        remaining -= write_size;
+        if (remaining > 0) {
+            AddCounter(ctr.data(), IvSize, write_size / BlockSize);
+        }
+    }
+
+    return size;
+}
+
+size_t AesCtrStorage::GetSize() const {
+    return m_base_storage->GetSize();
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_aes_ctr_storage.h

@@ -0,0 +1,43 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <optional>
+
+#include "core/crypto/aes_util.h"
+#include "core/crypto/key_manager.h"
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+
+class AesCtrStorage : public IStorage {
+    YUZU_NON_COPYABLE(AesCtrStorage);
+    YUZU_NON_MOVEABLE(AesCtrStorage);
+
+public:
+    static constexpr size_t BlockSize = 0x10;
+    static constexpr size_t KeySize = 0x10;
+    static constexpr size_t IvSize = 0x10;
+
+public:
+    static void MakeIv(void* dst, size_t dst_size, u64 upper, s64 offset);
+
+public:
+    AesCtrStorage(VirtualFile base, const void* key, size_t key_size, const void* iv,
+                  size_t iv_size);
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+    virtual size_t Write(const u8* buffer, size_t size, size_t offset) override;
+    virtual size_t GetSize() const override;
+
+private:
+    VirtualFile m_base_storage;
+    std::array<u8, KeySize> m_key;
+    std::array<u8, IvSize> m_iv;
+    mutable std::optional<Core::Crypto::AESCipher<Core::Crypto::Key128>> m_cipher;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_aes_xts_storage.cpp

@@ -0,0 +1,112 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/alignment.h"
+#include "common/swap.h"
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fssystem_aes_xts_storage.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+#include "core/file_sys/fssystem/fssystem_utility.h"
+
+namespace FileSys {
+
+void AesXtsStorage::MakeAesXtsIv(void* dst, size_t dst_size, s64 offset, size_t block_size) {
+    ASSERT(dst != nullptr);
+    ASSERT(dst_size == IvSize);
+    ASSERT(offset >= 0);
+
+    const uintptr_t out_addr = reinterpret_cast<uintptr_t>(dst);
+
+    *reinterpret_cast<s64_be*>(out_addr + sizeof(s64)) = offset / block_size;
+}
+
+AesXtsStorage::AesXtsStorage(VirtualFile base, const void* key1, const void* key2, size_t key_size,
+                             const void* iv, size_t iv_size, size_t block_size)
+    : m_base_storage(std::move(base)), m_block_size(block_size), m_mutex() {
+    ASSERT(m_base_storage != nullptr);
+    ASSERT(key1 != nullptr);
+    ASSERT(key2 != nullptr);
+    ASSERT(iv != nullptr);
+    ASSERT(key_size == KeySize);
+    ASSERT(iv_size == IvSize);
+    ASSERT(Common::IsAligned(m_block_size, AesBlockSize));
+
+    std::memcpy(m_key.data() + 0, key1, KeySize / 2);
+    std::memcpy(m_key.data() + 0x10, key2, KeySize / 2);
+    std::memcpy(m_iv.data(), iv, IvSize);
+
+    m_cipher.emplace(m_key, Core::Crypto::Mode::XTS);
+}
+
+size_t AesXtsStorage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Allow zero-size reads.
+    if (size == 0) {
+        return size;
+    }
+
+    // Ensure buffer is valid.
+    ASSERT(buffer != nullptr);
+
+    // We can only read at block aligned offsets.
+    ASSERT(Common::IsAligned(offset, AesBlockSize));
+    ASSERT(Common::IsAligned(size, AesBlockSize));
+
+    // Read the data.
+    m_base_storage->Read(buffer, size, offset);
+
+    // Setup the counter.
+    std::array<u8, IvSize> ctr;
+    std::memcpy(ctr.data(), m_iv.data(), IvSize);
+    AddCounter(ctr.data(), IvSize, offset / m_block_size);
+
+    // Handle any unaligned data before the start.
+    size_t processed_size = 0;
+    if ((offset % m_block_size) != 0) {
+        // Determine the size of the pre-data read.
+        const size_t skip_size =
+            static_cast<size_t>(offset - Common::AlignDown(offset, m_block_size));
+        const size_t data_size = std::min(size, m_block_size - skip_size);
+
+        // Decrypt into a pooled buffer.
+        {
+            PooledBuffer tmp_buf(m_block_size, m_block_size);
+            ASSERT(tmp_buf.GetSize() >= m_block_size);
+
+            std::memset(tmp_buf.GetBuffer(), 0, skip_size);
+            std::memcpy(tmp_buf.GetBuffer() + skip_size, buffer, data_size);
+
+            m_cipher->SetIV(ctr);
+            m_cipher->Transcode(tmp_buf.GetBuffer(), m_block_size, tmp_buf.GetBuffer(),
+                                Core::Crypto::Op::Decrypt);
+
+            std::memcpy(buffer, tmp_buf.GetBuffer() + skip_size, data_size);
+        }
+
+        AddCounter(ctr.data(), IvSize, 1);
+        processed_size += data_size;
+        ASSERT(processed_size == std::min(size, m_block_size - skip_size));
+    }
+
+    // Decrypt aligned chunks.
+    char* cur = reinterpret_cast<char*>(buffer) + processed_size;
+    size_t remaining = size - processed_size;
+    while (remaining > 0) {
+        const size_t cur_size = std::min(m_block_size, remaining);
+
+        m_cipher->SetIV(ctr);
+        m_cipher->Transcode(cur, cur_size, cur, Core::Crypto::Op::Decrypt);
+
+        remaining -= cur_size;
+        cur += cur_size;
+
+        AddCounter(ctr.data(), IvSize, 1);
+    }
+
+    return size;
+}
+
+size_t AesXtsStorage::GetSize() const {
+    return m_base_storage->GetSize();
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_aes_xts_storage.h

@@ -0,0 +1,43 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <mutex>
+#include <optional>
+
+#include "core/crypto/aes_util.h"
+#include "core/crypto/key_manager.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+
+namespace FileSys {
+
+class AesXtsStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(AesXtsStorage);
+    YUZU_NON_MOVEABLE(AesXtsStorage);
+
+public:
+    static constexpr size_t AesBlockSize = 0x10;
+    static constexpr size_t KeySize = 0x20;
+    static constexpr size_t IvSize = 0x10;
+
+public:
+    static void MakeAesXtsIv(void* dst, size_t dst_size, s64 offset, size_t block_size);
+
+public:
+    AesXtsStorage(VirtualFile base, const void* key1, const void* key2, size_t key_size,
+                  const void* iv, size_t iv_size, size_t block_size);
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+    virtual size_t GetSize() const override;
+
+private:
+    VirtualFile m_base_storage;
+    std::array<u8, KeySize> m_key;
+    std::array<u8, IvSize> m_iv;
+    const size_t m_block_size;
+    std::mutex m_mutex;
+    mutable std::optional<Core::Crypto::AESCipher<Core::Crypto::Key256>> m_cipher;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_alignment_matching_storage.h

@@ -0,0 +1,146 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/alignment.h"
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/fssystem/fssystem_alignment_matching_storage_impl.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+
+namespace FileSys {
+
+template <size_t DataAlign_, size_t BufferAlign_>
+class AlignmentMatchingStorage : public IStorage {
+    YUZU_NON_COPYABLE(AlignmentMatchingStorage);
+    YUZU_NON_MOVEABLE(AlignmentMatchingStorage);
+
+public:
+    static constexpr size_t DataAlign = DataAlign_;
+    static constexpr size_t BufferAlign = BufferAlign_;
+
+    static constexpr size_t DataAlignMax = 0x200;
+    static_assert(DataAlign <= DataAlignMax);
+    static_assert(Common::IsPowerOfTwo(DataAlign));
+    static_assert(Common::IsPowerOfTwo(BufferAlign));
+
+private:
+    VirtualFile m_base_storage;
+    s64 m_base_storage_size;
+
+public:
+    explicit AlignmentMatchingStorage(VirtualFile bs) : m_base_storage(std::move(bs)) {}
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+        // Allocate a work buffer on stack.
+        alignas(DataAlignMax) std::array<char, DataAlign> work_buf;
+
+        // Succeed if zero size.
+        if (size == 0) {
+            return size;
+        }
+
+        // Validate arguments.
+        ASSERT(buffer != nullptr);
+
+        s64 bs_size = this->GetSize();
+        ASSERT(R_SUCCEEDED(IStorage::CheckAccessRange(offset, size, bs_size)));
+
+        return AlignmentMatchingStorageImpl::Read(m_base_storage, work_buf.data(), work_buf.size(),
+                                                  DataAlign, BufferAlign, offset, buffer, size);
+    }
+
+    virtual size_t Write(const u8* buffer, size_t size, size_t offset) override {
+        // Allocate a work buffer on stack.
+        alignas(DataAlignMax) std::array<char, DataAlign> work_buf;
+
+        // Succeed if zero size.
+        if (size == 0) {
+            return size;
+        }
+
+        // Validate arguments.
+        ASSERT(buffer != nullptr);
+
+        s64 bs_size = this->GetSize();
+        ASSERT(R_SUCCEEDED(IStorage::CheckAccessRange(offset, size, bs_size)));
+
+        return AlignmentMatchingStorageImpl::Write(m_base_storage, work_buf.data(), work_buf.size(),
+                                                   DataAlign, BufferAlign, offset, buffer, size);
+    }
+
+    virtual size_t GetSize() const override {
+        return m_base_storage->GetSize();
+    }
+};
+
+template <size_t BufferAlign_>
+class AlignmentMatchingStoragePooledBuffer : public IStorage {
+    YUZU_NON_COPYABLE(AlignmentMatchingStoragePooledBuffer);
+    YUZU_NON_MOVEABLE(AlignmentMatchingStoragePooledBuffer);
+
+public:
+    static constexpr size_t BufferAlign = BufferAlign_;
+
+    static_assert(Common::IsPowerOfTwo(BufferAlign));
+
+private:
+    VirtualFile m_base_storage;
+    s64 m_base_storage_size;
+    size_t m_data_align;
+
+public:
+    explicit AlignmentMatchingStoragePooledBuffer(VirtualFile bs, size_t da)
+        : m_base_storage(std::move(bs)), m_data_align(da) {
+        ASSERT(Common::IsPowerOfTwo(da));
+    }
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+        // Succeed if zero size.
+        if (size == 0) {
+            return size;
+        }
+
+        // Validate arguments.
+        ASSERT(buffer != nullptr);
+
+        s64 bs_size = this->GetSize();
+        ASSERT(R_SUCCEEDED(IStorage::CheckAccessRange(offset, size, bs_size)));
+
+        // Allocate a pooled buffer.
+        PooledBuffer pooled_buffer;
+        pooled_buffer.AllocateParticularlyLarge(m_data_align, m_data_align);
+
+        return AlignmentMatchingStorageImpl::Read(m_base_storage, pooled_buffer.GetBuffer(),
+                                                  pooled_buffer.GetSize(), m_data_align,
+                                                  BufferAlign, offset, buffer, size);
+    }
+
+    virtual size_t Write(const u8* buffer, size_t size, size_t offset) override {
+        // Succeed if zero size.
+        if (size == 0) {
+            return size;
+        }
+
+        // Validate arguments.
+        ASSERT(buffer != nullptr);
+
+        s64 bs_size = this->GetSize();
+        ASSERT(R_SUCCEEDED(IStorage::CheckAccessRange(offset, size, bs_size)));
+
+        // Allocate a pooled buffer.
+        PooledBuffer pooled_buffer;
+        pooled_buffer.AllocateParticularlyLarge(m_data_align, m_data_align);
+
+        return AlignmentMatchingStorageImpl::Write(m_base_storage, pooled_buffer.GetBuffer(),
+                                                   pooled_buffer.GetSize(), m_data_align,
+                                                   BufferAlign, offset, buffer, size);
+    }
+
+    virtual size_t GetSize() const override {
+        return m_base_storage->GetSize();
+    }
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_alignment_matching_storage_impl.cpp

@@ -0,0 +1,204 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/alignment.h"
+#include "core/file_sys/fssystem/fssystem_alignment_matching_storage_impl.h"
+
+namespace FileSys {
+
+namespace {
+
+template <typename T>
+constexpr size_t GetRoundDownDifference(T x, size_t align) {
+    return static_cast<size_t>(x - Common::AlignDown(x, align));
+}
+
+template <typename T>
+constexpr size_t GetRoundUpDifference(T x, size_t align) {
+    return static_cast<size_t>(Common::AlignUp(x, align) - x);
+}
+
+template <typename T>
+size_t GetRoundUpDifference(T* x, size_t align) {
+    return GetRoundUpDifference(reinterpret_cast<uintptr_t>(x), align);
+}
+
+} // namespace
+
+size_t AlignmentMatchingStorageImpl::Read(VirtualFile base_storage, char* work_buf,
+                                          size_t work_buf_size, size_t data_alignment,
+                                          size_t buffer_alignment, s64 offset, u8* buffer,
+                                          size_t size) {
+    // Check preconditions.
+    ASSERT(work_buf_size >= data_alignment);
+
+    // Succeed if zero size.
+    if (size == 0) {
+        return size;
+    }
+
+    // Validate arguments.
+    ASSERT(buffer != nullptr);
+
+    // Determine extents.
+    u8* aligned_core_buffer;
+    s64 core_offset;
+    size_t core_size;
+    size_t buffer_gap;
+    size_t offset_gap;
+    s64 covered_offset;
+
+    const size_t offset_round_up_difference = GetRoundUpDifference(offset, data_alignment);
+    if (Common::IsAligned(reinterpret_cast<uintptr_t>(buffer) + offset_round_up_difference,
+                          buffer_alignment)) {
+        aligned_core_buffer = buffer + offset_round_up_difference;
+
+        core_offset = Common::AlignUp(offset, data_alignment);
+        core_size = (size < offset_round_up_difference)
+                        ? 0
+                        : Common::AlignDown(size - offset_round_up_difference, data_alignment);
+        buffer_gap = 0;
+        offset_gap = 0;
+
+        covered_offset = core_size > 0 ? core_offset : offset;
+    } else {
+        const size_t buffer_round_up_difference = GetRoundUpDifference(buffer, buffer_alignment);
+
+        aligned_core_buffer = buffer + buffer_round_up_difference;
+
+        core_offset = Common::AlignDown(offset, data_alignment);
+        core_size = (size < buffer_round_up_difference)
+                        ? 0
+                        : Common::AlignDown(size - buffer_round_up_difference, data_alignment);
+        buffer_gap = buffer_round_up_difference;
+        offset_gap = GetRoundDownDifference(offset, data_alignment);
+
+        covered_offset = offset;
+    }
+
+    // Read the core portion.
+    if (core_size > 0) {
+        base_storage->Read(aligned_core_buffer, core_size, core_offset);
+
+        if (offset_gap != 0 || buffer_gap != 0) {
+            std::memmove(aligned_core_buffer - buffer_gap, aligned_core_buffer + offset_gap,
+                         core_size - offset_gap);
+            core_size -= offset_gap;
+        }
+    }
+
+    // Handle the head portion.
+    if (offset < covered_offset) {
+        const s64 head_offset = Common::AlignDown(offset, data_alignment);
+        const size_t head_size = static_cast<size_t>(covered_offset - offset);
+
+        ASSERT(GetRoundDownDifference(offset, data_alignment) + head_size <= work_buf_size);
+
+        base_storage->Read(reinterpret_cast<u8*>(work_buf), data_alignment, head_offset);
+        std::memcpy(buffer, work_buf + GetRoundDownDifference(offset, data_alignment), head_size);
+    }
+
+    // Handle the tail portion.
+    s64 tail_offset = covered_offset + core_size;
+    size_t remaining_tail_size = static_cast<size_t>((offset + size) - tail_offset);
+    while (remaining_tail_size > 0) {
+        const auto aligned_tail_offset = Common::AlignDown(tail_offset, data_alignment);
+        const auto cur_size =
+            std::min(static_cast<size_t>(aligned_tail_offset + data_alignment - tail_offset),
+                     remaining_tail_size);
+        base_storage->Read(reinterpret_cast<u8*>(work_buf), data_alignment, aligned_tail_offset);
+
+        ASSERT((tail_offset - offset) + cur_size <= size);
+        ASSERT((tail_offset - aligned_tail_offset) + cur_size <= data_alignment);
+        std::memcpy(reinterpret_cast<char*>(buffer) + (tail_offset - offset),
+                    work_buf + (tail_offset - aligned_tail_offset), cur_size);
+
+        remaining_tail_size -= cur_size;
+        tail_offset += cur_size;
+    }
+
+    return size;
+}
+
+size_t AlignmentMatchingStorageImpl::Write(VirtualFile base_storage, char* work_buf,
+                                           size_t work_buf_size, size_t data_alignment,
+                                           size_t buffer_alignment, s64 offset, const u8* buffer,
+                                           size_t size) {
+    // Check preconditions.
+    ASSERT(work_buf_size >= data_alignment);
+
+    // Succeed if zero size.
+    if (size == 0) {
+        return size;
+    }
+
+    // Validate arguments.
+    ASSERT(buffer != nullptr);
+
+    // Determine extents.
+    const u8* aligned_core_buffer;
+    s64 core_offset;
+    size_t core_size;
+    s64 covered_offset;
+
+    const size_t offset_round_up_difference = GetRoundUpDifference(offset, data_alignment);
+    if (Common::IsAligned(reinterpret_cast<uintptr_t>(buffer) + offset_round_up_difference,
+                          buffer_alignment)) {
+        aligned_core_buffer = buffer + offset_round_up_difference;
+
+        core_offset = Common::AlignUp(offset, data_alignment);
+        core_size = (size < offset_round_up_difference)
+                        ? 0
+                        : Common::AlignDown(size - offset_round_up_difference, data_alignment);
+
+        covered_offset = core_size > 0 ? core_offset : offset;
+    } else {
+        aligned_core_buffer = nullptr;
+
+        core_offset = Common::AlignDown(offset, data_alignment);
+        core_size = 0;
+
+        covered_offset = offset;
+    }
+
+    // Write the core portion.
+    if (core_size > 0) {
+        base_storage->Write(aligned_core_buffer, core_size, core_offset);
+    }
+
+    // Handle the head portion.
+    if (offset < covered_offset) {
+        const s64 head_offset = Common::AlignDown(offset, data_alignment);
+        const size_t head_size = static_cast<size_t>(covered_offset - offset);
+
+        ASSERT((offset - head_offset) + head_size <= data_alignment);
+
+        base_storage->Read(reinterpret_cast<u8*>(work_buf), data_alignment, head_offset);
+        std::memcpy(work_buf + (offset - head_offset), buffer, head_size);
+        base_storage->Write(reinterpret_cast<u8*>(work_buf), data_alignment, head_offset);
+    }
+
+    // Handle the tail portion.
+    s64 tail_offset = covered_offset + core_size;
+    size_t remaining_tail_size = static_cast<size_t>((offset + size) - tail_offset);
+    while (remaining_tail_size > 0) {
+        ASSERT(static_cast<size_t>(tail_offset - offset) < size);
+
+        const auto aligned_tail_offset = Common::AlignDown(tail_offset, data_alignment);
+        const auto cur_size =
+            std::min(static_cast<size_t>(aligned_tail_offset + data_alignment - tail_offset),
+                     remaining_tail_size);
+
+        base_storage->Read(reinterpret_cast<u8*>(work_buf), data_alignment, aligned_tail_offset);
+        std::memcpy(work_buf + GetRoundDownDifference(tail_offset, data_alignment),
+                    buffer + (tail_offset - offset), cur_size);
+        base_storage->Write(reinterpret_cast<u8*>(work_buf), data_alignment, aligned_tail_offset);
+
+        remaining_tail_size -= cur_size;
+        tail_offset += cur_size;
+    }
+
+    return size;
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_alignment_matching_storage_impl.h

@@ -0,0 +1,21 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+
+namespace FileSys {
+
+class AlignmentMatchingStorageImpl {
+public:
+    static size_t Read(VirtualFile base_storage, char* work_buf, size_t work_buf_size,
+                       size_t data_alignment, size_t buffer_alignment, s64 offset, u8* buffer,
+                       size_t size);
+    static size_t Write(VirtualFile base_storage, char* work_buf, size_t work_buf_size,
+                        size_t data_alignment, size_t buffer_alignment, s64 offset,
+                        const u8* buffer, size_t size);
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_bucket_tree.cpp

@@ -0,0 +1,598 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree_utils.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+
+namespace FileSys {
+
+namespace {
+
+using Node = impl::BucketTreeNode<const s64*>;
+static_assert(sizeof(Node) == sizeof(BucketTree::NodeHeader));
+static_assert(std::is_trivial_v<Node>);
+
+constexpr inline s32 NodeHeaderSize = sizeof(BucketTree::NodeHeader);
+
+class StorageNode {
+private:
+    class Offset {
+    public:
+        using difference_type = s64;
+
+    private:
+        s64 m_offset;
+        s32 m_stride;
+
+    public:
+        constexpr Offset(s64 offset, s32 stride) : m_offset(offset), m_stride(stride) {}
+
+        constexpr Offset& operator++() {
+            m_offset += m_stride;
+            return *this;
+        }
+        constexpr Offset operator++(int) {
+            Offset ret(*this);
+            m_offset += m_stride;
+            return ret;
+        }
+
+        constexpr Offset& operator--() {
+            m_offset -= m_stride;
+            return *this;
+        }
+        constexpr Offset operator--(int) {
+            Offset ret(*this);
+            m_offset -= m_stride;
+            return ret;
+        }
+
+        constexpr difference_type operator-(const Offset& rhs) const {
+            return (m_offset - rhs.m_offset) / m_stride;
+        }
+
+        constexpr Offset operator+(difference_type ofs) const {
+            return Offset(m_offset + ofs * m_stride, m_stride);
+        }
+        constexpr Offset operator-(difference_type ofs) const {
+            return Offset(m_offset - ofs * m_stride, m_stride);
+        }
+
+        constexpr Offset& operator+=(difference_type ofs) {
+            m_offset += ofs * m_stride;
+            return *this;
+        }
+        constexpr Offset& operator-=(difference_type ofs) {
+            m_offset -= ofs * m_stride;
+            return *this;
+        }
+
+        constexpr bool operator==(const Offset& rhs) const {
+            return m_offset == rhs.m_offset;
+        }
+        constexpr bool operator!=(const Offset& rhs) const {
+            return m_offset != rhs.m_offset;
+        }
+
+        constexpr s64 Get() const {
+            return m_offset;
+        }
+    };
+
+private:
+    const Offset m_start;
+    const s32 m_count;
+    s32 m_index;
+
+public:
+    StorageNode(size_t size, s32 count)
+        : m_start(NodeHeaderSize, static_cast<s32>(size)), m_count(count), m_index(-1) {}
+    StorageNode(s64 ofs, size_t size, s32 count)
+        : m_start(NodeHeaderSize + ofs, static_cast<s32>(size)), m_count(count), m_index(-1) {}
+
+    s32 GetIndex() const {
+        return m_index;
+    }
+
+    void Find(const char* buffer, s64 virtual_address) {
+        s32 end = m_count;
+        auto pos = m_start;
+
+        while (end > 0) {
+            auto half = end / 2;
+            auto mid = pos + half;
+
+            s64 offset = 0;
+            std::memcpy(std::addressof(offset), buffer + mid.Get(), sizeof(s64));
+
+            if (offset <= virtual_address) {
+                pos = mid + 1;
+                end -= half + 1;
+            } else {
+                end = half;
+            }
+        }
+
+        m_index = static_cast<s32>(pos - m_start) - 1;
+    }
+
+    Result Find(VirtualFile storage, s64 virtual_address) {
+        s32 end = m_count;
+        auto pos = m_start;
+
+        while (end > 0) {
+            auto half = end / 2;
+            auto mid = pos + half;
+
+            s64 offset = 0;
+            storage->ReadObject(std::addressof(offset), mid.Get());
+
+            if (offset <= virtual_address) {
+                pos = mid + 1;
+                end -= half + 1;
+            } else {
+                end = half;
+            }
+        }
+
+        m_index = static_cast<s32>(pos - m_start) - 1;
+        R_SUCCEED();
+    }
+};
+
+} // namespace
+
+void BucketTree::Header::Format(s32 entry_count_) {
+    ASSERT(entry_count_ >= 0);
+
+    this->magic = Magic;
+    this->version = Version;
+    this->entry_count = entry_count_;
+    this->reserved = 0;
+}
+
+Result BucketTree::Header::Verify() const {
+    R_UNLESS(this->magic == Magic, ResultInvalidBucketTreeSignature);
+    R_UNLESS(this->entry_count >= 0, ResultInvalidBucketTreeEntryCount);
+    R_UNLESS(this->version <= Version, ResultUnsupportedVersion);
+    R_SUCCEED();
+}
+
+Result BucketTree::NodeHeader::Verify(s32 node_index, size_t node_size, size_t entry_size) const {
+    R_UNLESS(this->index == node_index, ResultInvalidBucketTreeNodeIndex);
+    R_UNLESS(entry_size != 0 && node_size >= entry_size + NodeHeaderSize, ResultInvalidSize);
+
+    const size_t max_entry_count = (node_size - NodeHeaderSize) / entry_size;
+    R_UNLESS(this->count > 0 && static_cast<size_t>(this->count) <= max_entry_count,
+             ResultInvalidBucketTreeNodeEntryCount);
+    R_UNLESS(this->offset >= 0, ResultInvalidBucketTreeNodeOffset);
+
+    R_SUCCEED();
+}
+
+Result BucketTree::Initialize(VirtualFile node_storage, VirtualFile entry_storage, size_t node_size,
+                              size_t entry_size, s32 entry_count) {
+    // Validate preconditions.
+    ASSERT(entry_size >= sizeof(s64));
+    ASSERT(node_size >= entry_size + sizeof(NodeHeader));
+    ASSERT(NodeSizeMin <= node_size && node_size <= NodeSizeMax);
+    ASSERT(Common::IsPowerOfTwo(node_size));
+    ASSERT(!this->IsInitialized());
+
+    // Ensure valid entry count.
+    R_UNLESS(entry_count > 0, ResultInvalidArgument);
+
+    // Allocate node.
+    R_UNLESS(m_node_l1.Allocate(node_size), ResultBufferAllocationFailed);
+    ON_RESULT_FAILURE {
+        m_node_l1.Free(node_size);
+    };
+
+    // Read node.
+    node_storage->Read(reinterpret_cast<u8*>(m_node_l1.Get()), node_size);
+
+    // Verify node.
+    R_TRY(m_node_l1->Verify(0, node_size, sizeof(s64)));
+
+    // Validate offsets.
+    const auto offset_count = GetOffsetCount(node_size);
+    const auto entry_set_count = GetEntrySetCount(node_size, entry_size, entry_count);
+    const auto* const node = m_node_l1.Get<Node>();
+
+    s64 start_offset;
+    if (offset_count < entry_set_count && node->GetCount() < offset_count) {
+        start_offset = *node->GetEnd();
+    } else {
+        start_offset = *node->GetBegin();
+    }
+    const auto end_offset = node->GetEndOffset();
+
+    R_UNLESS(0 <= start_offset && start_offset <= node->GetBeginOffset(),
+             ResultInvalidBucketTreeEntryOffset);
+    R_UNLESS(start_offset < end_offset, ResultInvalidBucketTreeEntryOffset);
+
+    // Set member variables.
+    m_node_storage = node_storage;
+    m_entry_storage = entry_storage;
+    m_node_size = node_size;
+    m_entry_size = entry_size;
+    m_entry_count = entry_count;
+    m_offset_count = offset_count;
+    m_entry_set_count = entry_set_count;
+
+    m_offset_cache.offsets.start_offset = start_offset;
+    m_offset_cache.offsets.end_offset = end_offset;
+    m_offset_cache.is_initialized = true;
+
+    // We succeeded.
+    R_SUCCEED();
+}
+
+void BucketTree::Initialize(size_t node_size, s64 end_offset) {
+    ASSERT(NodeSizeMin <= node_size && node_size <= NodeSizeMax);
+    ASSERT(Common::IsPowerOfTwo(node_size));
+    ASSERT(end_offset > 0);
+    ASSERT(!this->IsInitialized());
+
+    m_node_size = node_size;
+
+    m_offset_cache.offsets.start_offset = 0;
+    m_offset_cache.offsets.end_offset = end_offset;
+    m_offset_cache.is_initialized = true;
+}
+
+void BucketTree::Finalize() {
+    if (this->IsInitialized()) {
+        m_node_storage = VirtualFile();
+        m_entry_storage = VirtualFile();
+        m_node_l1.Free(m_node_size);
+        m_node_size = 0;
+        m_entry_size = 0;
+        m_entry_count = 0;
+        m_offset_count = 0;
+        m_entry_set_count = 0;
+
+        m_offset_cache.offsets.start_offset = 0;
+        m_offset_cache.offsets.end_offset = 0;
+        m_offset_cache.is_initialized = false;
+    }
+}
+
+Result BucketTree::Find(Visitor* visitor, s64 virtual_address) {
+    ASSERT(visitor != nullptr);
+    ASSERT(this->IsInitialized());
+
+    R_UNLESS(virtual_address >= 0, ResultInvalidOffset);
+    R_UNLESS(!this->IsEmpty(), ResultOutOfRange);
+
+    BucketTree::Offsets offsets;
+    R_TRY(this->GetOffsets(std::addressof(offsets)));
+
+    R_TRY(visitor->Initialize(this, offsets));
+
+    R_RETURN(visitor->Find(virtual_address));
+}
+
+Result BucketTree::InvalidateCache() {
+    // Reset our offsets.
+    m_offset_cache.is_initialized = false;
+
+    R_SUCCEED();
+}
+
+Result BucketTree::EnsureOffsetCache() {
+    // If we already have an offset cache, we're good.
+    R_SUCCEED_IF(m_offset_cache.is_initialized);
+
+    // Acquire exclusive right to edit the offset cache.
+    std::scoped_lock lk(m_offset_cache.mutex);
+
+    // Check again, to be sure.
+    R_SUCCEED_IF(m_offset_cache.is_initialized);
+
+    // Read/verify L1.
+    m_node_storage->Read(reinterpret_cast<u8*>(m_node_l1.Get()), m_node_size);
+    R_TRY(m_node_l1->Verify(0, m_node_size, sizeof(s64)));
+
+    // Get the node.
+    auto* const node = m_node_l1.Get<Node>();
+
+    s64 start_offset;
+    if (m_offset_count < m_entry_set_count && node->GetCount() < m_offset_count) {
+        start_offset = *node->GetEnd();
+    } else {
+        start_offset = *node->GetBegin();
+    }
+    const auto end_offset = node->GetEndOffset();
+
+    R_UNLESS(0 <= start_offset && start_offset <= node->GetBeginOffset(),
+             ResultInvalidBucketTreeEntryOffset);
+    R_UNLESS(start_offset < end_offset, ResultInvalidBucketTreeEntryOffset);
+
+    m_offset_cache.offsets.start_offset = start_offset;
+    m_offset_cache.offsets.end_offset = end_offset;
+    m_offset_cache.is_initialized = true;
+
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::Initialize(const BucketTree* tree, const BucketTree::Offsets& offsets) {
+    ASSERT(tree != nullptr);
+    ASSERT(m_tree == nullptr || m_tree == tree);
+
+    if (m_entry == nullptr) {
+        m_entry = ::operator new(tree->m_entry_size);
+        R_UNLESS(m_entry != nullptr, ResultBufferAllocationFailed);
+
+        m_tree = tree;
+        m_offsets = offsets;
+    }
+
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::MoveNext() {
+    R_UNLESS(this->IsValid(), ResultOutOfRange);
+
+    // Invalidate our index, and read the header for the next index.
+    auto entry_index = m_entry_index + 1;
+    if (entry_index == m_entry_set.info.count) {
+        const auto entry_set_index = m_entry_set.info.index + 1;
+        R_UNLESS(entry_set_index < m_entry_set_count, ResultOutOfRange);
+
+        m_entry_index = -1;
+
+        const auto end = m_entry_set.info.end;
+
+        const auto entry_set_size = m_tree->m_node_size;
+        const auto entry_set_offset = entry_set_index * static_cast<s64>(entry_set_size);
+
+        m_tree->m_entry_storage->ReadObject(std::addressof(m_entry_set), entry_set_offset);
+        R_TRY(m_entry_set.header.Verify(entry_set_index, entry_set_size, m_tree->m_entry_size));
+
+        R_UNLESS(m_entry_set.info.start == end && m_entry_set.info.start < m_entry_set.info.end,
+                 ResultInvalidBucketTreeEntrySetOffset);
+
+        entry_index = 0;
+    } else {
+        m_entry_index = -1;
+    }
+
+    // Read the new entry.
+    const auto entry_size = m_tree->m_entry_size;
+    const auto entry_offset = impl::GetBucketTreeEntryOffset(
+        m_entry_set.info.index, m_tree->m_node_size, entry_size, entry_index);
+    m_tree->m_entry_storage->Read(reinterpret_cast<u8*>(m_entry), entry_size, entry_offset);
+
+    // Note that we changed index.
+    m_entry_index = entry_index;
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::MovePrevious() {
+    R_UNLESS(this->IsValid(), ResultOutOfRange);
+
+    // Invalidate our index, and read the header for the previous index.
+    auto entry_index = m_entry_index;
+    if (entry_index == 0) {
+        R_UNLESS(m_entry_set.info.index > 0, ResultOutOfRange);
+
+        m_entry_index = -1;
+
+        const auto start = m_entry_set.info.start;
+
+        const auto entry_set_size = m_tree->m_node_size;
+        const auto entry_set_index = m_entry_set.info.index - 1;
+        const auto entry_set_offset = entry_set_index * static_cast<s64>(entry_set_size);
+
+        m_tree->m_entry_storage->ReadObject(std::addressof(m_entry_set), entry_set_offset);
+        R_TRY(m_entry_set.header.Verify(entry_set_index, entry_set_size, m_tree->m_entry_size));
+
+        R_UNLESS(m_entry_set.info.end == start && m_entry_set.info.start < m_entry_set.info.end,
+                 ResultInvalidBucketTreeEntrySetOffset);
+
+        entry_index = m_entry_set.info.count;
+    } else {
+        m_entry_index = -1;
+    }
+
+    --entry_index;
+
+    // Read the new entry.
+    const auto entry_size = m_tree->m_entry_size;
+    const auto entry_offset = impl::GetBucketTreeEntryOffset(
+        m_entry_set.info.index, m_tree->m_node_size, entry_size, entry_index);
+    m_tree->m_entry_storage->Read(reinterpret_cast<u8*>(m_entry), entry_size, entry_offset);
+
+    // Note that we changed index.
+    m_entry_index = entry_index;
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::Find(s64 virtual_address) {
+    ASSERT(m_tree != nullptr);
+
+    // Get the node.
+    const auto* const node = m_tree->m_node_l1.Get<Node>();
+    R_UNLESS(virtual_address < node->GetEndOffset(), ResultOutOfRange);
+
+    // Get the entry set index.
+    s32 entry_set_index = -1;
+    if (m_tree->IsExistOffsetL2OnL1() && virtual_address < node->GetBeginOffset()) {
+        const auto start = node->GetEnd();
+        const auto end = node->GetBegin() + m_tree->m_offset_count;
+
+        auto pos = std::upper_bound(start, end, virtual_address);
+        R_UNLESS(start < pos, ResultOutOfRange);
+        --pos;
+
+        entry_set_index = static_cast<s32>(pos - start);
+    } else {
+        const auto start = node->GetBegin();
+        const auto end = node->GetEnd();
+
+        auto pos = std::upper_bound(start, end, virtual_address);
+        R_UNLESS(start < pos, ResultOutOfRange);
+        --pos;
+
+        if (m_tree->IsExistL2()) {
+            const auto node_index = static_cast<s32>(pos - start);
+            R_UNLESS(0 <= node_index && node_index < m_tree->m_offset_count,
+                     ResultInvalidBucketTreeNodeOffset);
+
+            R_TRY(this->FindEntrySet(std::addressof(entry_set_index), virtual_address, node_index));
+        } else {
+            entry_set_index = static_cast<s32>(pos - start);
+        }
+    }
+
+    // Validate the entry set index.
+    R_UNLESS(0 <= entry_set_index && entry_set_index < m_tree->m_entry_set_count,
+             ResultInvalidBucketTreeNodeOffset);
+
+    // Find the entry.
+    R_TRY(this->FindEntry(virtual_address, entry_set_index));
+
+    // Set count.
+    m_entry_set_count = m_tree->m_entry_set_count;
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::FindEntrySet(s32* out_index, s64 virtual_address, s32 node_index) {
+    const auto node_size = m_tree->m_node_size;
+
+    PooledBuffer pool(node_size, 1);
+    if (node_size <= pool.GetSize()) {
+        R_RETURN(
+            this->FindEntrySetWithBuffer(out_index, virtual_address, node_index, pool.GetBuffer()));
+    } else {
+        pool.Deallocate();
+        R_RETURN(this->FindEntrySetWithoutBuffer(out_index, virtual_address, node_index));
+    }
+}
+
+Result BucketTree::Visitor::FindEntrySetWithBuffer(s32* out_index, s64 virtual_address,
+                                                   s32 node_index, char* buffer) {
+    // Calculate node extents.
+    const auto node_size = m_tree->m_node_size;
+    const auto node_offset = (node_index + 1) * static_cast<s64>(node_size);
+    VirtualFile storage = m_tree->m_node_storage;
+
+    // Read the node.
+    storage->Read(reinterpret_cast<u8*>(buffer), node_size, node_offset);
+
+    // Validate the header.
+    NodeHeader header;
+    std::memcpy(std::addressof(header), buffer, NodeHeaderSize);
+    R_TRY(header.Verify(node_index, node_size, sizeof(s64)));
+
+    // Create the node, and find.
+    StorageNode node(sizeof(s64), header.count);
+    node.Find(buffer, virtual_address);
+    R_UNLESS(node.GetIndex() >= 0, ResultInvalidBucketTreeVirtualOffset);
+
+    // Return the index.
+    *out_index = static_cast<s32>(m_tree->GetEntrySetIndex(header.index, node.GetIndex()));
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::FindEntrySetWithoutBuffer(s32* out_index, s64 virtual_address,
+                                                      s32 node_index) {
+    // Calculate node extents.
+    const auto node_size = m_tree->m_node_size;
+    const auto node_offset = (node_index + 1) * static_cast<s64>(node_size);
+    VirtualFile storage = m_tree->m_node_storage;
+
+    // Read and validate the header.
+    NodeHeader header;
+    storage->ReadObject(std::addressof(header), node_offset);
+    R_TRY(header.Verify(node_index, node_size, sizeof(s64)));
+
+    // Create the node, and find.
+    StorageNode node(node_offset, sizeof(s64), header.count);
+    R_TRY(node.Find(storage, virtual_address));
+    R_UNLESS(node.GetIndex() >= 0, ResultOutOfRange);
+
+    // Return the index.
+    *out_index = static_cast<s32>(m_tree->GetEntrySetIndex(header.index, node.GetIndex()));
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::FindEntry(s64 virtual_address, s32 entry_set_index) {
+    const auto entry_set_size = m_tree->m_node_size;
+
+    PooledBuffer pool(entry_set_size, 1);
+    if (entry_set_size <= pool.GetSize()) {
+        R_RETURN(this->FindEntryWithBuffer(virtual_address, entry_set_index, pool.GetBuffer()));
+    } else {
+        pool.Deallocate();
+        R_RETURN(this->FindEntryWithoutBuffer(virtual_address, entry_set_index));
+    }
+}
+
+Result BucketTree::Visitor::FindEntryWithBuffer(s64 virtual_address, s32 entry_set_index,
+                                                char* buffer) {
+    // Calculate entry set extents.
+    const auto entry_size = m_tree->m_entry_size;
+    const auto entry_set_size = m_tree->m_node_size;
+    const auto entry_set_offset = entry_set_index * static_cast<s64>(entry_set_size);
+    VirtualFile storage = m_tree->m_entry_storage;
+
+    // Read the entry set.
+    storage->Read(reinterpret_cast<u8*>(buffer), entry_set_size, entry_set_offset);
+
+    // Validate the entry_set.
+    EntrySetHeader entry_set;
+    std::memcpy(std::addressof(entry_set), buffer, sizeof(EntrySetHeader));
+    R_TRY(entry_set.header.Verify(entry_set_index, entry_set_size, entry_size));
+
+    // Create the node, and find.
+    StorageNode node(entry_size, entry_set.info.count);
+    node.Find(buffer, virtual_address);
+    R_UNLESS(node.GetIndex() >= 0, ResultOutOfRange);
+
+    // Copy the data into entry.
+    const auto entry_index = node.GetIndex();
+    const auto entry_offset = impl::GetBucketTreeEntryOffset(0, entry_size, entry_index);
+    std::memcpy(m_entry, buffer + entry_offset, entry_size);
+
+    // Set our entry set/index.
+    m_entry_set = entry_set;
+    m_entry_index = entry_index;
+
+    R_SUCCEED();
+}
+
+Result BucketTree::Visitor::FindEntryWithoutBuffer(s64 virtual_address, s32 entry_set_index) {
+    // Calculate entry set extents.
+    const auto entry_size = m_tree->m_entry_size;
+    const auto entry_set_size = m_tree->m_node_size;
+    const auto entry_set_offset = entry_set_index * static_cast<s64>(entry_set_size);
+    VirtualFile storage = m_tree->m_entry_storage;
+
+    // Read and validate the entry_set.
+    EntrySetHeader entry_set;
+    storage->ReadObject(std::addressof(entry_set), entry_set_offset);
+    R_TRY(entry_set.header.Verify(entry_set_index, entry_set_size, entry_size));
+
+    // Create the node, and find.
+    StorageNode node(entry_set_offset, entry_size, entry_set.info.count);
+    R_TRY(node.Find(storage, virtual_address));
+    R_UNLESS(node.GetIndex() >= 0, ResultOutOfRange);
+
+    // Copy the data into entry.
+    const auto entry_index = node.GetIndex();
+    const auto entry_offset =
+        impl::GetBucketTreeEntryOffset(entry_set_offset, entry_size, entry_index);
+    storage->Read(reinterpret_cast<u8*>(m_entry), entry_size, entry_offset);
+
+    // Set our entry set/index.
+    m_entry_set = entry_set;
+    m_entry_index = entry_index;
+
+    R_SUCCEED();
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_bucket_tree.h

@@ -0,0 +1,416 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <mutex>
+
+#include "common/alignment.h"
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+#include "common/literals.h"
+
+#include "core/file_sys/vfs/vfs.h"
+#include "core/hle/result.h"
+
+namespace FileSys {
+
+using namespace Common::Literals;
+
+class BucketTree {
+    YUZU_NON_COPYABLE(BucketTree);
+    YUZU_NON_MOVEABLE(BucketTree);
+
+public:
+    static constexpr u32 Magic = Common::MakeMagic('B', 'K', 'T', 'R');
+    static constexpr u32 Version = 1;
+
+    static constexpr size_t NodeSizeMin = 1_KiB;
+    static constexpr size_t NodeSizeMax = 512_KiB;
+
+public:
+    class Visitor;
+
+    struct Header {
+        u32 magic;
+        u32 version;
+        s32 entry_count;
+        s32 reserved;
+
+        void Format(s32 entry_count);
+        Result Verify() const;
+    };
+    static_assert(std::is_trivial_v<Header>);
+    static_assert(sizeof(Header) == 0x10);
+
+    struct NodeHeader {
+        s32 index;
+        s32 count;
+        s64 offset;
+
+        Result Verify(s32 node_index, size_t node_size, size_t entry_size) const;
+    };
+    static_assert(std::is_trivial_v<NodeHeader>);
+    static_assert(sizeof(NodeHeader) == 0x10);
+
+    struct Offsets {
+        s64 start_offset;
+        s64 end_offset;
+
+        constexpr bool IsInclude(s64 offset) const {
+            return this->start_offset <= offset && offset < this->end_offset;
+        }
+
+        constexpr bool IsInclude(s64 offset, s64 size) const {
+            return size > 0 && this->start_offset <= offset && size <= (this->end_offset - offset);
+        }
+    };
+    static_assert(std::is_trivial_v<Offsets>);
+    static_assert(sizeof(Offsets) == 0x10);
+
+    struct OffsetCache {
+        Offsets offsets;
+        std::mutex mutex;
+        bool is_initialized;
+
+        OffsetCache() : offsets{-1, -1}, mutex(), is_initialized(false) {}
+    };
+
+    class ContinuousReadingInfo {
+    public:
+        constexpr ContinuousReadingInfo() : m_read_size(), m_skip_count(), m_done() {}
+
+        constexpr void Reset() {
+            m_read_size = 0;
+            m_skip_count = 0;
+            m_done = false;
+        }
+
+        constexpr void SetSkipCount(s32 count) {
+            ASSERT(count >= 0);
+            m_skip_count = count;
+        }
+        constexpr s32 GetSkipCount() const {
+            return m_skip_count;
+        }
+        constexpr bool CheckNeedScan() {
+            return (--m_skip_count) <= 0;
+        }
+
+        constexpr void Done() {
+            m_read_size = 0;
+            m_done = true;
+        }
+        constexpr bool IsDone() const {
+            return m_done;
+        }
+
+        constexpr void SetReadSize(size_t size) {
+            m_read_size = size;
+        }
+        constexpr size_t GetReadSize() const {
+            return m_read_size;
+        }
+        constexpr bool CanDo() const {
+            return m_read_size > 0;
+        }
+
+    private:
+        size_t m_read_size;
+        s32 m_skip_count;
+        bool m_done;
+    };
+
+private:
+    class NodeBuffer {
+        YUZU_NON_COPYABLE(NodeBuffer);
+
+    public:
+        NodeBuffer() : m_header() {}
+
+        ~NodeBuffer() {
+            ASSERT(m_header == nullptr);
+        }
+
+        NodeBuffer(NodeBuffer&& rhs) : m_header(rhs.m_header) {
+            rhs.m_header = nullptr;
+        }
+
+        NodeBuffer& operator=(NodeBuffer&& rhs) {
+            if (this != std::addressof(rhs)) {
+                ASSERT(m_header == nullptr);
+
+                m_header = rhs.m_header;
+
+                rhs.m_header = nullptr;
+            }
+            return *this;
+        }
+
+        bool Allocate(size_t node_size) {
+            ASSERT(m_header == nullptr);
+
+            m_header = ::operator new(node_size, std::align_val_t{sizeof(s64)});
+
+            // ASSERT(Common::IsAligned(m_header, sizeof(s64)));
+
+            return m_header != nullptr;
+        }
+
+        void Free(size_t node_size) {
+            if (m_header) {
+                ::operator delete(m_header, std::align_val_t{sizeof(s64)});
+                m_header = nullptr;
+            }
+        }
+
+        void FillZero(size_t node_size) const {
+            if (m_header) {
+                std::memset(m_header, 0, node_size);
+            }
+        }
+
+        NodeHeader* Get() const {
+            return reinterpret_cast<NodeHeader*>(m_header);
+        }
+
+        NodeHeader* operator->() const {
+            return this->Get();
+        }
+
+        template <typename T>
+        T* Get() const {
+            static_assert(std::is_trivial_v<T>);
+            static_assert(sizeof(T) == sizeof(NodeHeader));
+            return reinterpret_cast<T*>(m_header);
+        }
+
+    private:
+        void* m_header;
+    };
+
+private:
+    static constexpr s32 GetEntryCount(size_t node_size, size_t entry_size) {
+        return static_cast<s32>((node_size - sizeof(NodeHeader)) / entry_size);
+    }
+
+    static constexpr s32 GetOffsetCount(size_t node_size) {
+        return static_cast<s32>((node_size - sizeof(NodeHeader)) / sizeof(s64));
+    }
+
+    static constexpr s32 GetEntrySetCount(size_t node_size, size_t entry_size, s32 entry_count) {
+        const s32 entry_count_per_node = GetEntryCount(node_size, entry_size);
+        return Common::DivideUp(entry_count, entry_count_per_node);
+    }
+
+    static constexpr s32 GetNodeL2Count(size_t node_size, size_t entry_size, s32 entry_count) {
+        const s32 offset_count_per_node = GetOffsetCount(node_size);
+        const s32 entry_set_count = GetEntrySetCount(node_size, entry_size, entry_count);
+
+        if (entry_set_count <= offset_count_per_node) {
+            return 0;
+        }
+
+        const s32 node_l2_count = Common::DivideUp(entry_set_count, offset_count_per_node);
+        ASSERT(node_l2_count <= offset_count_per_node);
+
+        return Common::DivideUp(entry_set_count - (offset_count_per_node - (node_l2_count - 1)),
+                                offset_count_per_node);
+    }
+
+public:
+    BucketTree()
+        : m_node_storage(), m_entry_storage(), m_node_l1(), m_node_size(), m_entry_size(),
+          m_entry_count(), m_offset_count(), m_entry_set_count(), m_offset_cache() {}
+    ~BucketTree() {
+        this->Finalize();
+    }
+
+    Result Initialize(VirtualFile node_storage, VirtualFile entry_storage, size_t node_size,
+                      size_t entry_size, s32 entry_count);
+    void Initialize(size_t node_size, s64 end_offset);
+    void Finalize();
+
+    bool IsInitialized() const {
+        return m_node_size > 0;
+    }
+    bool IsEmpty() const {
+        return m_entry_size == 0;
+    }
+
+    Result Find(Visitor* visitor, s64 virtual_address);
+    Result InvalidateCache();
+
+    s32 GetEntryCount() const {
+        return m_entry_count;
+    }
+
+    Result GetOffsets(Offsets* out) {
+        // Ensure we have an offset cache.
+        R_TRY(this->EnsureOffsetCache());
+
+        // Set the output.
+        *out = m_offset_cache.offsets;
+        R_SUCCEED();
+    }
+
+public:
+    static constexpr s64 QueryHeaderStorageSize() {
+        return sizeof(Header);
+    }
+
+    static constexpr s64 QueryNodeStorageSize(size_t node_size, size_t entry_size,
+                                              s32 entry_count) {
+        ASSERT(entry_size >= sizeof(s64));
+        ASSERT(node_size >= entry_size + sizeof(NodeHeader));
+        ASSERT(NodeSizeMin <= node_size && node_size <= NodeSizeMax);
+        ASSERT(Common::IsPowerOfTwo(node_size));
+        ASSERT(entry_count >= 0);
+
+        if (entry_count <= 0) {
+            return 0;
+        }
+        return (1 + GetNodeL2Count(node_size, entry_size, entry_count)) *
+               static_cast<s64>(node_size);
+    }
+
+    static constexpr s64 QueryEntryStorageSize(size_t node_size, size_t entry_size,
+                                               s32 entry_count) {
+        ASSERT(entry_size >= sizeof(s64));
+        ASSERT(node_size >= entry_size + sizeof(NodeHeader));
+        ASSERT(NodeSizeMin <= node_size && node_size <= NodeSizeMax);
+        ASSERT(Common::IsPowerOfTwo(node_size));
+        ASSERT(entry_count >= 0);
+
+        if (entry_count <= 0) {
+            return 0;
+        }
+        return GetEntrySetCount(node_size, entry_size, entry_count) * static_cast<s64>(node_size);
+    }
+
+private:
+    template <typename EntryType>
+    struct ContinuousReadingParam {
+        s64 offset;
+        size_t size;
+        NodeHeader entry_set;
+        s32 entry_index;
+        Offsets offsets;
+        EntryType entry;
+    };
+
+private:
+    template <typename EntryType>
+    Result ScanContinuousReading(ContinuousReadingInfo* out_info,
+                                 const ContinuousReadingParam<EntryType>& param) const;
+
+    bool IsExistL2() const {
+        return m_offset_count < m_entry_set_count;
+    }
+    bool IsExistOffsetL2OnL1() const {
+        return this->IsExistL2() && m_node_l1->count < m_offset_count;
+    }
+
+    s64 GetEntrySetIndex(s32 node_index, s32 offset_index) const {
+        return (m_offset_count - m_node_l1->count) + (m_offset_count * node_index) + offset_index;
+    }
+
+    Result EnsureOffsetCache();
+
+private:
+    mutable VirtualFile m_node_storage;
+    mutable VirtualFile m_entry_storage;
+    NodeBuffer m_node_l1;
+    size_t m_node_size;
+    size_t m_entry_size;
+    s32 m_entry_count;
+    s32 m_offset_count;
+    s32 m_entry_set_count;
+    OffsetCache m_offset_cache;
+};
+
+class BucketTree::Visitor {
+    YUZU_NON_COPYABLE(Visitor);
+    YUZU_NON_MOVEABLE(Visitor);
+
+public:
+    constexpr Visitor()
+        : m_tree(), m_entry(), m_entry_index(-1), m_entry_set_count(), m_entry_set{} {}
+    ~Visitor() {
+        if (m_entry != nullptr) {
+            ::operator delete(m_entry, m_tree->m_entry_size);
+            m_tree = nullptr;
+            m_entry = nullptr;
+        }
+    }
+
+    bool IsValid() const {
+        return m_entry_index >= 0;
+    }
+    bool CanMoveNext() const {
+        return this->IsValid() && (m_entry_index + 1 < m_entry_set.info.count ||
+                                   m_entry_set.info.index + 1 < m_entry_set_count);
+    }
+    bool CanMovePrevious() const {
+        return this->IsValid() && (m_entry_index > 0 || m_entry_set.info.index > 0);
+    }
+
+    Result MoveNext();
+    Result MovePrevious();
+
+    template <typename EntryType>
+    Result ScanContinuousReading(ContinuousReadingInfo* out_info, s64 offset, size_t size) const;
+
+    const void* Get() const {
+        ASSERT(this->IsValid());
+        return m_entry;
+    }
+
+    template <typename T>
+    const T* Get() const {
+        ASSERT(this->IsValid());
+        return reinterpret_cast<const T*>(m_entry);
+    }
+
+    const BucketTree* GetTree() const {
+        return m_tree;
+    }
+
+private:
+    Result Initialize(const BucketTree* tree, const BucketTree::Offsets& offsets);
+
+    Result Find(s64 virtual_address);
+
+    Result FindEntrySet(s32* out_index, s64 virtual_address, s32 node_index);
+    Result FindEntrySetWithBuffer(s32* out_index, s64 virtual_address, s32 node_index,
+                                  char* buffer);
+    Result FindEntrySetWithoutBuffer(s32* out_index, s64 virtual_address, s32 node_index);
+
+    Result FindEntry(s64 virtual_address, s32 entry_set_index);
+    Result FindEntryWithBuffer(s64 virtual_address, s32 entry_set_index, char* buffer);
+    Result FindEntryWithoutBuffer(s64 virtual_address, s32 entry_set_index);
+
+private:
+    friend class BucketTree;
+
+    union EntrySetHeader {
+        NodeHeader header;
+        struct Info {
+            s32 index;
+            s32 count;
+            s64 end;
+            s64 start;
+        } info;
+        static_assert(std::is_trivial_v<Info>);
+    };
+    static_assert(std::is_trivial_v<EntrySetHeader>);
+
+    const BucketTree* m_tree;
+    BucketTree::Offsets m_offsets;
+    void* m_entry;
+    s32 m_entry_index;
+    s32 m_entry_set_count;
+    EntrySetHeader m_entry_set;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_bucket_tree_template_impl.h

@@ -0,0 +1,170 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree_utils.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+
+namespace FileSys {
+
+template <typename EntryType>
+Result BucketTree::ScanContinuousReading(ContinuousReadingInfo* out_info,
+                                         const ContinuousReadingParam<EntryType>& param) const {
+    static_assert(std::is_trivial_v<ContinuousReadingParam<EntryType>>);
+
+    // Validate our preconditions.
+    ASSERT(this->IsInitialized());
+    ASSERT(out_info != nullptr);
+    ASSERT(m_entry_size == sizeof(EntryType));
+
+    // Reset the output.
+    out_info->Reset();
+
+    // If there's nothing to read, we're done.
+    R_SUCCEED_IF(param.size == 0);
+
+    // If we're reading a fragment, we're done.
+    R_SUCCEED_IF(param.entry.IsFragment());
+
+    // Validate the first entry.
+    auto entry = param.entry;
+    auto cur_offset = param.offset;
+    R_UNLESS(entry.GetVirtualOffset() <= cur_offset, ResultOutOfRange);
+
+    // Create a pooled buffer for our scan.
+    PooledBuffer pool(m_node_size, 1);
+    char* buffer = nullptr;
+
+    s64 entry_storage_size = m_entry_storage->GetSize();
+
+    // Read the node.
+    if (m_node_size <= pool.GetSize()) {
+        buffer = pool.GetBuffer();
+        const auto ofs = param.entry_set.index * static_cast<s64>(m_node_size);
+        R_UNLESS(m_node_size + ofs <= static_cast<size_t>(entry_storage_size),
+                 ResultInvalidBucketTreeNodeEntryCount);
+
+        m_entry_storage->Read(reinterpret_cast<u8*>(buffer), m_node_size, ofs);
+    }
+
+    // Calculate extents.
+    const auto end_offset = cur_offset + static_cast<s64>(param.size);
+    s64 phys_offset = entry.GetPhysicalOffset();
+
+    // Start merge tracking.
+    s64 merge_size = 0;
+    s64 readable_size = 0;
+    bool merged = false;
+
+    // Iterate.
+    auto entry_index = param.entry_index;
+    for (const auto entry_count = param.entry_set.count; entry_index < entry_count; ++entry_index) {
+        // If we're past the end, we're done.
+        if (end_offset <= cur_offset) {
+            break;
+        }
+
+        // Validate the entry offset.
+        const auto entry_offset = entry.GetVirtualOffset();
+        R_UNLESS(entry_offset <= cur_offset, ResultInvalidIndirectEntryOffset);
+
+        // Get the next entry.
+        EntryType next_entry = {};
+        s64 next_entry_offset;
+
+        if (entry_index + 1 < entry_count) {
+            if (buffer != nullptr) {
+                const auto ofs = impl::GetBucketTreeEntryOffset(0, m_entry_size, entry_index + 1);
+                std::memcpy(std::addressof(next_entry), buffer + ofs, m_entry_size);
+            } else {
+                const auto ofs = impl::GetBucketTreeEntryOffset(param.entry_set.index, m_node_size,
+                                                                m_entry_size, entry_index + 1);
+                m_entry_storage->ReadObject(std::addressof(next_entry), ofs);
+            }
+
+            next_entry_offset = next_entry.GetVirtualOffset();
+            R_UNLESS(param.offsets.IsInclude(next_entry_offset), ResultInvalidIndirectEntryOffset);
+        } else {
+            next_entry_offset = param.entry_set.offset;
+        }
+
+        // Validate the next entry offset.
+        R_UNLESS(cur_offset < next_entry_offset, ResultInvalidIndirectEntryOffset);
+
+        // Determine the much data there is.
+        const auto data_size = next_entry_offset - cur_offset;
+        ASSERT(data_size > 0);
+
+        // Determine how much data we should read.
+        const auto remaining_size = end_offset - cur_offset;
+        const size_t read_size = static_cast<size_t>(std::min(data_size, remaining_size));
+        ASSERT(read_size <= param.size);
+
+        // Update our merge tracking.
+        if (entry.IsFragment()) {
+            // If we can't merge, stop looping.
+            if (EntryType::FragmentSizeMax <= read_size || remaining_size <= data_size) {
+                break;
+            }
+
+            // Otherwise, add the current size to the merge size.
+            merge_size += read_size;
+        } else {
+            //  If we can't merge, stop looping.
+            if (phys_offset != entry.GetPhysicalOffset()) {
+                break;
+            }
+
+            // Add the size to the readable amount.
+            readable_size += merge_size + read_size;
+            ASSERT(readable_size <= static_cast<s64>(param.size));
+
+            // Update whether we've merged.
+            merged |= merge_size > 0;
+            merge_size = 0;
+        }
+
+        // Advance.
+        cur_offset += read_size;
+        ASSERT(cur_offset <= end_offset);
+
+        phys_offset += next_entry_offset - entry_offset;
+        entry = next_entry;
+    }
+
+    // If we merged, set our readable size.
+    if (merged) {
+        out_info->SetReadSize(static_cast<size_t>(readable_size));
+    }
+    out_info->SetSkipCount(entry_index - param.entry_index);
+
+    R_SUCCEED();
+}
+
+template <typename EntryType>
+Result BucketTree::Visitor::ScanContinuousReading(ContinuousReadingInfo* out_info, s64 offset,
+                                                  size_t size) const {
+    static_assert(std::is_trivial_v<EntryType>);
+    ASSERT(this->IsValid());
+
+    // Create our parameters.
+    ContinuousReadingParam<EntryType> param = {
+        .offset = offset,
+        .size = size,
+        .entry_set = m_entry_set.header,
+        .entry_index = m_entry_index,
+        .offsets{},
+        .entry{},
+    };
+    std::memcpy(std::addressof(param.offsets), std::addressof(m_offsets),
+                sizeof(BucketTree::Offsets));
+    std::memcpy(std::addressof(param.entry), m_entry, sizeof(EntryType));
+
+    // Scan.
+    R_RETURN(m_tree->ScanContinuousReading<EntryType>(out_info, param));
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_bucket_tree_utils.h

@@ -0,0 +1,110 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fssystem_bucket_tree.h"
+
+namespace FileSys::impl {
+
+class SafeValue {
+public:
+    static s64 GetInt64(const void* ptr) {
+        s64 value;
+        std::memcpy(std::addressof(value), ptr, sizeof(s64));
+        return value;
+    }
+
+    static s64 GetInt64(const s64* ptr) {
+        return GetInt64(static_cast<const void*>(ptr));
+    }
+
+    static s64 GetInt64(const s64& v) {
+        return GetInt64(std::addressof(v));
+    }
+
+    static void SetInt64(void* dst, const void* src) {
+        std::memcpy(dst, src, sizeof(s64));
+    }
+
+    static void SetInt64(void* dst, const s64* src) {
+        return SetInt64(dst, static_cast<const void*>(src));
+    }
+
+    static void SetInt64(void* dst, const s64& v) {
+        return SetInt64(dst, std::addressof(v));
+    }
+};
+
+template <typename IteratorType>
+struct BucketTreeNode {
+    using Header = BucketTree::NodeHeader;
+
+    Header header;
+
+    s32 GetCount() const {
+        return this->header.count;
+    }
+
+    void* GetArray() {
+        return std::addressof(this->header) + 1;
+    }
+    template <typename T>
+    T* GetArray() {
+        return reinterpret_cast<T*>(this->GetArray());
+    }
+    const void* GetArray() const {
+        return std::addressof(this->header) + 1;
+    }
+    template <typename T>
+    const T* GetArray() const {
+        return reinterpret_cast<const T*>(this->GetArray());
+    }
+
+    s64 GetBeginOffset() const {
+        return *this->GetArray<s64>();
+    }
+    s64 GetEndOffset() const {
+        return this->header.offset;
+    }
+
+    IteratorType GetBegin() {
+        return IteratorType(this->GetArray<s64>());
+    }
+    IteratorType GetEnd() {
+        return IteratorType(this->GetArray<s64>()) + this->header.count;
+    }
+    IteratorType GetBegin() const {
+        return IteratorType(this->GetArray<s64>());
+    }
+    IteratorType GetEnd() const {
+        return IteratorType(this->GetArray<s64>()) + this->header.count;
+    }
+
+    IteratorType GetBegin(size_t entry_size) {
+        return IteratorType(this->GetArray(), entry_size);
+    }
+    IteratorType GetEnd(size_t entry_size) {
+        return IteratorType(this->GetArray(), entry_size) + this->header.count;
+    }
+    IteratorType GetBegin(size_t entry_size) const {
+        return IteratorType(this->GetArray(), entry_size);
+    }
+    IteratorType GetEnd(size_t entry_size) const {
+        return IteratorType(this->GetArray(), entry_size) + this->header.count;
+    }
+};
+
+constexpr inline s64 GetBucketTreeEntryOffset(s64 entry_set_offset, size_t entry_size,
+                                              s32 entry_index) {
+    return entry_set_offset + sizeof(BucketTree::NodeHeader) +
+           entry_index * static_cast<s64>(entry_size);
+}
+
+constexpr inline s64 GetBucketTreeEntryOffset(s32 entry_set_index, size_t node_size,
+                                              size_t entry_size, s32 entry_index) {
+    return GetBucketTreeEntryOffset(entry_set_index * static_cast<s64>(node_size), entry_size,
+                                    entry_index);
+}
+
+} // namespace FileSys::impl

core/fs/fssystem/fssystem_compressed_storage.h

@@ -0,0 +1,963 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/literals.h"
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree.h"
+#include "core/file_sys/fssystem/fssystem_compression_common.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+
+using namespace Common::Literals;
+
+class CompressedStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(CompressedStorage);
+    YUZU_NON_MOVEABLE(CompressedStorage);
+
+public:
+    static constexpr size_t NodeSize = 16_KiB;
+
+    struct Entry {
+        s64 virt_offset;
+        s64 phys_offset;
+        CompressionType compression_type;
+        s32 phys_size;
+
+        s64 GetPhysicalSize() const {
+            return this->phys_size;
+        }
+    };
+    static_assert(std::is_trivial_v<Entry>);
+    static_assert(sizeof(Entry) == 0x18);
+
+public:
+    static constexpr s64 QueryNodeStorageSize(s32 entry_count) {
+        return BucketTree::QueryNodeStorageSize(NodeSize, sizeof(Entry), entry_count);
+    }
+
+    static constexpr s64 QueryEntryStorageSize(s32 entry_count) {
+        return BucketTree::QueryEntryStorageSize(NodeSize, sizeof(Entry), entry_count);
+    }
+
+private:
+    class CompressedStorageCore {
+        YUZU_NON_COPYABLE(CompressedStorageCore);
+        YUZU_NON_MOVEABLE(CompressedStorageCore);
+
+    public:
+        CompressedStorageCore() : m_table(), m_data_storage() {}
+
+        ~CompressedStorageCore() {
+            this->Finalize();
+        }
+
+    public:
+        Result Initialize(VirtualFile data_storage, VirtualFile node_storage,
+                          VirtualFile entry_storage, s32 bktr_entry_count, size_t block_size_max,
+                          size_t continuous_reading_size_max,
+                          GetDecompressorFunction get_decompressor) {
+            // Check pre-conditions.
+            ASSERT(0 < block_size_max);
+            ASSERT(block_size_max <= continuous_reading_size_max);
+            ASSERT(get_decompressor != nullptr);
+
+            // Initialize our entry table.
+            R_TRY(m_table.Initialize(node_storage, entry_storage, NodeSize, sizeof(Entry),
+                                     bktr_entry_count));
+
+            // Set our other fields.
+            m_block_size_max = block_size_max;
+            m_continuous_reading_size_max = continuous_reading_size_max;
+            m_data_storage = data_storage;
+            m_get_decompressor_function = get_decompressor;
+
+            R_SUCCEED();
+        }
+
+        void Finalize() {
+            if (this->IsInitialized()) {
+                m_table.Finalize();
+                m_data_storage = VirtualFile();
+            }
+        }
+
+        VirtualFile GetDataStorage() {
+            return m_data_storage;
+        }
+
+        Result GetDataStorageSize(s64* out) {
+            // Check pre-conditions.
+            ASSERT(out != nullptr);
+
+            // Get size.
+            *out = m_data_storage->GetSize();
+
+            R_SUCCEED();
+        }
+
+        BucketTree& GetEntryTable() {
+            return m_table;
+        }
+
+        Result GetEntryList(Entry* out_entries, s32* out_read_count, s32 max_entry_count,
+                            s64 offset, s64 size) {
+            // Check pre-conditions.
+            ASSERT(offset >= 0);
+            ASSERT(size >= 0);
+            ASSERT(this->IsInitialized());
+
+            // Check that we can output the count.
+            R_UNLESS(out_read_count != nullptr, ResultNullptrArgument);
+
+            // Check that we have anything to read at all.
+            R_SUCCEED_IF(size == 0);
+
+            // Check that either we have a buffer, or this is to determine how many we need.
+            if (max_entry_count != 0) {
+                R_UNLESS(out_entries != nullptr, ResultNullptrArgument);
+            }
+
+            // Get the table offsets.
+            BucketTree::Offsets table_offsets;
+            R_TRY(m_table.GetOffsets(std::addressof(table_offsets)));
+
+            // Validate arguments.
+            R_UNLESS(table_offsets.IsInclude(offset, size), ResultOutOfRange);
+
+            // Find the offset in our tree.
+            BucketTree::Visitor visitor;
+            R_TRY(m_table.Find(std::addressof(visitor), offset));
+            {
+                const auto entry_offset = visitor.Get<Entry>()->virt_offset;
+                R_UNLESS(0 <= entry_offset && table_offsets.IsInclude(entry_offset),
+                         ResultUnexpectedInCompressedStorageA);
+            }
+
+            // Get the entries.
+            const auto end_offset = offset + size;
+            s32 read_count = 0;
+            while (visitor.Get<Entry>()->virt_offset < end_offset) {
+                // If we should be setting the output, do so.
+                if (max_entry_count != 0) {
+                    // Ensure we only read as many entries as we can.
+                    if (read_count >= max_entry_count) {
+                        break;
+                    }
+
+                    // Set the current output entry.
+                    out_entries[read_count] = *visitor.Get<Entry>();
+                }
+
+                // Increase the read count.
+                ++read_count;
+
+                // If we're at the end, we're done.
+                if (!visitor.CanMoveNext()) {
+                    break;
+                }
+
+                // Move to the next entry.
+                R_TRY(visitor.MoveNext());
+            }
+
+            // Set the output read count.
+            *out_read_count = read_count;
+            R_SUCCEED();
+        }
+
+        Result GetSize(s64* out) {
+            // Check pre-conditions.
+            ASSERT(out != nullptr);
+
+            // Get our table offsets.
+            BucketTree::Offsets offsets;
+            R_TRY(m_table.GetOffsets(std::addressof(offsets)));
+
+            // Set the output.
+            *out = offsets.end_offset;
+            R_SUCCEED();
+        }
+
+        Result OperatePerEntry(s64 offset, s64 size, auto f) {
+            // Check pre-conditions.
+            ASSERT(offset >= 0);
+            ASSERT(size >= 0);
+            ASSERT(this->IsInitialized());
+
+            // Succeed if there's nothing to operate on.
+            R_SUCCEED_IF(size == 0);
+
+            // Get the table offsets.
+            BucketTree::Offsets table_offsets;
+            R_TRY(m_table.GetOffsets(std::addressof(table_offsets)));
+
+            // Validate arguments.
+            R_UNLESS(table_offsets.IsInclude(offset, size), ResultOutOfRange);
+
+            // Find the offset in our tree.
+            BucketTree::Visitor visitor;
+            R_TRY(m_table.Find(std::addressof(visitor), offset));
+            {
+                const auto entry_offset = visitor.Get<Entry>()->virt_offset;
+                R_UNLESS(0 <= entry_offset && table_offsets.IsInclude(entry_offset),
+                         ResultUnexpectedInCompressedStorageA);
+            }
+
+            // Prepare to operate in chunks.
+            auto cur_offset = offset;
+            const auto end_offset = offset + static_cast<s64>(size);
+
+            while (cur_offset < end_offset) {
+                // Get the current entry.
+                const auto cur_entry = *visitor.Get<Entry>();
+
+                // Get and validate the entry's offset.
+                const auto cur_entry_offset = cur_entry.virt_offset;
+                R_UNLESS(cur_entry_offset <= cur_offset, ResultUnexpectedInCompressedStorageA);
+
+                // Get and validate the next entry offset.
+                s64 next_entry_offset;
+                if (visitor.CanMoveNext()) {
+                    R_TRY(visitor.MoveNext());
+                    next_entry_offset = visitor.Get<Entry>()->virt_offset;
+                    R_UNLESS(table_offsets.IsInclude(next_entry_offset),
+                             ResultUnexpectedInCompressedStorageA);
+                } else {
+                    next_entry_offset = table_offsets.end_offset;
+                }
+                R_UNLESS(cur_offset < next_entry_offset, ResultUnexpectedInCompressedStorageA);
+
+                // Get the offset of the entry in the data we read.
+                const auto data_offset = cur_offset - cur_entry_offset;
+                const auto data_size = (next_entry_offset - cur_entry_offset);
+                ASSERT(data_size > 0);
+
+                // Determine how much is left.
+                const auto remaining_size = end_offset - cur_offset;
+                const auto cur_size = std::min<s64>(remaining_size, data_size - data_offset);
+                ASSERT(cur_size <= size);
+
+                // Get the data storage size.
+                s64 storage_size = m_data_storage->GetSize();
+
+                // Check that our read remains naively physically in bounds.
+                R_UNLESS(0 <= cur_entry.phys_offset && cur_entry.phys_offset <= storage_size,
+                         ResultUnexpectedInCompressedStorageC);
+
+                // If we have any compression, verify that we remain physically in bounds.
+                if (cur_entry.compression_type != CompressionType::None) {
+                    R_UNLESS(cur_entry.phys_offset + cur_entry.GetPhysicalSize() <= storage_size,
+                             ResultUnexpectedInCompressedStorageC);
+                }
+
+                // Check that block alignment requirements are met.
+                if (CompressionTypeUtility::IsBlockAlignmentRequired(cur_entry.compression_type)) {
+                    R_UNLESS(Common::IsAligned(cur_entry.phys_offset, CompressionBlockAlignment),
+                             ResultUnexpectedInCompressedStorageA);
+                }
+
+                // Invoke the operator.
+                bool is_continuous = true;
+                R_TRY(
+                    f(std::addressof(is_continuous), cur_entry, data_size, data_offset, cur_size));
+
+                // If not continuous, we're done.
+                if (!is_continuous) {
+                    break;
+                }
+
+                // Advance.
+                cur_offset += cur_size;
+            }
+
+            R_SUCCEED();
+        }
+
+    public:
+        using ReadImplFunction = std::function<Result(void*, size_t)>;
+        using ReadFunction = std::function<Result(size_t, const ReadImplFunction&)>;
+
+    public:
+        Result Read(s64 offset, s64 size, const ReadFunction& read_func) {
+            // Check pre-conditions.
+            ASSERT(offset >= 0);
+            ASSERT(this->IsInitialized());
+
+            // Succeed immediately, if we have nothing to read.
+            R_SUCCEED_IF(size == 0);
+
+            // Declare read lambda.
+            constexpr int EntriesCountMax = 0x80;
+            struct Entries {
+                CompressionType compression_type;
+                u32 gap_from_prev;
+                u32 physical_size;
+                u32 virtual_size;
+            };
+            std::array<Entries, EntriesCountMax> entries;
+            s32 entry_count = 0;
+            Entry prev_entry = {
+                .virt_offset = -1,
+                .phys_offset{},
+                .compression_type{},
+                .phys_size{},
+            };
+            bool will_allocate_pooled_buffer = false;
+            s64 required_access_physical_offset = 0;
+            s64 required_access_physical_size = 0;
+
+            auto PerformRequiredRead = [&]() -> Result {
+                // If there are no entries, we have nothing to do.
+                R_SUCCEED_IF(entry_count == 0);
+
+                // Get the remaining size in a convenient form.
+                const size_t total_required_size =
+                    static_cast<size_t>(required_access_physical_size);
+
+                // Perform the read based on whether we need to allocate a buffer.
+                if (will_allocate_pooled_buffer) {
+                    // Allocate a pooled buffer.
+                    PooledBuffer pooled_buffer;
+                    if (pooled_buffer.GetAllocatableSizeMax() >= total_required_size) {
+                        pooled_buffer.Allocate(total_required_size, m_block_size_max);
+                    } else {
+                        pooled_buffer.AllocateParticularlyLarge(
+                            std::min<size_t>(
+                                total_required_size,
+                                PooledBuffer::GetAllocatableParticularlyLargeSizeMax()),
+                            m_block_size_max);
+                    }
+
+                    // Read each of the entries.
+                    for (s32 entry_idx = 0; entry_idx < entry_count; ++entry_idx) {
+                        // Determine the current read size.
+                        bool will_use_pooled_buffer = false;
+                        const size_t cur_read_size = [&]() -> size_t {
+                            if (const size_t target_entry_size =
+                                    static_cast<size_t>(entries[entry_idx].physical_size) +
+                                    static_cast<size_t>(entries[entry_idx].gap_from_prev);
+                                target_entry_size <= pooled_buffer.GetSize()) {
+                                // We'll be using the pooled buffer.
+                                will_use_pooled_buffer = true;
+
+                                // Determine how much we can read.
+                                const size_t max_size = std::min<size_t>(
+                                    required_access_physical_size, pooled_buffer.GetSize());
+
+                                size_t read_size = 0;
+                                for (auto n = entry_idx; n < entry_count; ++n) {
+                                    const size_t cur_entry_size =
+                                        static_cast<size_t>(entries[n].physical_size) +
+                                        static_cast<size_t>(entries[n].gap_from_prev);
+                                    if (read_size + cur_entry_size > max_size) {
+                                        break;
+                                    }
+
+                                    read_size += cur_entry_size;
+                                }
+
+                                return read_size;
+                            } else {
+                                // If we don't fit, we must be uncompressed.
+                                ASSERT(entries[entry_idx].compression_type ==
+                                       CompressionType::None);
+
+                                // We can perform the whole of an uncompressed read directly.
+                                return entries[entry_idx].virtual_size;
+                            }
+                        }();
+
+                        // Perform the read based on whether or not we'll use the pooled buffer.
+                        if (will_use_pooled_buffer) {
+                            // Read the compressed data into the pooled buffer.
+                            auto* const buffer = pooled_buffer.GetBuffer();
+                            m_data_storage->Read(reinterpret_cast<u8*>(buffer), cur_read_size,
+                                                 required_access_physical_offset);
+
+                            // Decompress the data.
+                            size_t buffer_offset;
+                            for (buffer_offset = 0;
+                                 entry_idx < entry_count &&
+                                 ((static_cast<size_t>(entries[entry_idx].physical_size) +
+                                   static_cast<size_t>(entries[entry_idx].gap_from_prev)) == 0 ||
+                                  buffer_offset < cur_read_size);
+                                 buffer_offset += entries[entry_idx++].physical_size) {
+                                // Advance by the relevant gap.
+                                buffer_offset += entries[entry_idx].gap_from_prev;
+
+                                const auto compression_type = entries[entry_idx].compression_type;
+                                switch (compression_type) {
+                                case CompressionType::None: {
+                                    // Check that we can remain within bounds.
+                                    ASSERT(buffer_offset + entries[entry_idx].virtual_size <=
+                                           cur_read_size);
+
+                                    // Perform no decompression.
+                                    R_TRY(read_func(
+                                        entries[entry_idx].virtual_size,
+                                        [&](void* dst, size_t dst_size) -> Result {
+                                            // Check that the size is valid.
+                                            ASSERT(dst_size == entries[entry_idx].virtual_size);
+
+                                            // We have no compression, so just copy the data
+                                            // out.
+                                            std::memcpy(dst, buffer + buffer_offset,
+                                                        entries[entry_idx].virtual_size);
+                                            R_SUCCEED();
+                                        }));
+
+                                    break;
+                                }
+                                case CompressionType::Zeros: {
+                                    // Check that we can remain within bounds.
+                                    ASSERT(buffer_offset <= cur_read_size);
+
+                                    // Zero the memory.
+                                    R_TRY(read_func(
+                                        entries[entry_idx].virtual_size,
+                                        [&](void* dst, size_t dst_size) -> Result {
+                                            // Check that the size is valid.
+                                            ASSERT(dst_size == entries[entry_idx].virtual_size);
+
+                                            // The data is zeroes, so zero the buffer.
+                                            std::memset(dst, 0, entries[entry_idx].virtual_size);
+                                            R_SUCCEED();
+                                        }));
+
+                                    break;
+                                }
+                                default: {
+                                    // Check that we can remain within bounds.
+                                    ASSERT(buffer_offset + entries[entry_idx].physical_size <=
+                                           cur_read_size);
+
+                                    // Get the decompressor.
+                                    const auto decompressor =
+                                        this->GetDecompressor(compression_type);
+                                    R_UNLESS(decompressor != nullptr,
+                                             ResultUnexpectedInCompressedStorageB);
+
+                                    // Decompress the data.
+                                    R_TRY(read_func(entries[entry_idx].virtual_size,
+                                                    [&](void* dst, size_t dst_size) -> Result {
+                                                        // Check that the size is valid.
+                                                        ASSERT(dst_size ==
+                                                               entries[entry_idx].virtual_size);
+
+                                                        // Perform the decompression.
+                                                        R_RETURN(decompressor(
+                                                            dst, entries[entry_idx].virtual_size,
+                                                            buffer + buffer_offset,
+                                                            entries[entry_idx].physical_size));
+                                                    }));
+
+                                    break;
+                                }
+                                }
+                            }
+
+                            // Check that we processed the correct amount of data.
+                            ASSERT(buffer_offset == cur_read_size);
+                        } else {
+                            // Account for the gap from the previous entry.
+                            required_access_physical_offset += entries[entry_idx].gap_from_prev;
+                            required_access_physical_size -= entries[entry_idx].gap_from_prev;
+
+                            // We don't need the buffer (as the data is uncompressed), so just
+                            // execute the read.
+                            R_TRY(
+                                read_func(cur_read_size, [&](void* dst, size_t dst_size) -> Result {
+                                    // Check that the size is valid.
+                                    ASSERT(dst_size == cur_read_size);
+
+                                    // Perform the read.
+                                    m_data_storage->Read(reinterpret_cast<u8*>(dst), cur_read_size,
+                                                         required_access_physical_offset);
+
+                                    R_SUCCEED();
+                                }));
+                        }
+
+                        // Advance on.
+                        required_access_physical_offset += cur_read_size;
+                        required_access_physical_size -= cur_read_size;
+                    }
+
+                    // Verify that we have nothing remaining to read.
+                    ASSERT(required_access_physical_size == 0);
+
+                    R_SUCCEED();
+                } else {
+                    // We don't need a buffer, so just execute the read.
+                    R_TRY(read_func(total_required_size, [&](void* dst, size_t dst_size) -> Result {
+                        // Check that the size is valid.
+                        ASSERT(dst_size == total_required_size);
+
+                        // Perform the read.
+                        m_data_storage->Read(reinterpret_cast<u8*>(dst), total_required_size,
+                                             required_access_physical_offset);
+
+                        R_SUCCEED();
+                    }));
+                }
+
+                R_SUCCEED();
+            };
+
+            R_TRY(this->OperatePerEntry(
+                offset, size,
+                [&](bool* out_continuous, const Entry& entry, s64 virtual_data_size,
+                    s64 data_offset, s64 read_size) -> Result {
+                    // Determine the physical extents.
+                    s64 physical_offset, physical_size;
+                    if (CompressionTypeUtility::IsRandomAccessible(entry.compression_type)) {
+                        physical_offset = entry.phys_offset + data_offset;
+                        physical_size = read_size;
+                    } else {
+                        physical_offset = entry.phys_offset;
+                        physical_size = entry.GetPhysicalSize();
+                    }
+
+                    // If we have a pending data storage operation, perform it if we have to.
+                    const s64 required_access_physical_end =
+                        required_access_physical_offset + required_access_physical_size;
+                    if (required_access_physical_size > 0) {
+                        const bool required_by_gap =
+                            !(required_access_physical_end <= physical_offset &&
+                              physical_offset <= Common::AlignUp(required_access_physical_end,
+                                                                 CompressionBlockAlignment));
+                        const bool required_by_continuous_size =
+                            ((physical_size + physical_offset) - required_access_physical_end) +
+                                required_access_physical_size >
+                            static_cast<s64>(m_continuous_reading_size_max);
+                        const bool required_by_entry_count = entry_count == EntriesCountMax;
+                        if (required_by_gap || required_by_continuous_size ||
+                            required_by_entry_count) {
+                            // Check that our planned access is sane.
+                            ASSERT(!will_allocate_pooled_buffer ||
+                                   required_access_physical_size <=
+                                       static_cast<s64>(m_continuous_reading_size_max));
+
+                            // Perform the required read.
+                            const Result rc = PerformRequiredRead();
+                            if (R_FAILED(rc)) {
+                                R_THROW(rc);
+                            }
+
+                            // Reset our requirements.
+                            prev_entry.virt_offset = -1;
+                            required_access_physical_size = 0;
+                            entry_count = 0;
+                            will_allocate_pooled_buffer = false;
+                        }
+                    }
+
+                    // Sanity check that we're within bounds on entries.
+                    ASSERT(entry_count < EntriesCountMax);
+
+                    // Determine if a buffer allocation is needed.
+                    if (entry.compression_type != CompressionType::None ||
+                        (prev_entry.virt_offset >= 0 &&
+                         entry.virt_offset - prev_entry.virt_offset !=
+                             entry.phys_offset - prev_entry.phys_offset)) {
+                        will_allocate_pooled_buffer = true;
+                    }
+
+                    // If we need to access the data storage, update our required access parameters.
+                    if (CompressionTypeUtility::IsDataStorageAccessRequired(
+                            entry.compression_type)) {
+                        // If the data is compressed, ensure the access is sane.
+                        if (entry.compression_type != CompressionType::None) {
+                            R_UNLESS(data_offset == 0, ResultInvalidOffset);
+                            R_UNLESS(virtual_data_size == read_size, ResultInvalidSize);
+                            R_UNLESS(entry.GetPhysicalSize() <= static_cast<s64>(m_block_size_max),
+                                     ResultUnexpectedInCompressedStorageD);
+                        }
+
+                        // Update the required access parameters.
+                        s64 gap_from_prev;
+                        if (required_access_physical_size > 0) {
+                            gap_from_prev = physical_offset - required_access_physical_end;
+                        } else {
+                            gap_from_prev = 0;
+                            required_access_physical_offset = physical_offset;
+                        }
+                        required_access_physical_size += physical_size + gap_from_prev;
+
+                        // Create an entry to access the data storage.
+                        entries[entry_count++] = {
+                            .compression_type = entry.compression_type,
+                            .gap_from_prev = static_cast<u32>(gap_from_prev),
+                            .physical_size = static_cast<u32>(physical_size),
+                            .virtual_size = static_cast<u32>(read_size),
+                        };
+                    } else {
+                        // Verify that we're allowed to be operating on the non-data-storage-access
+                        // type.
+                        R_UNLESS(entry.compression_type == CompressionType::Zeros,
+                                 ResultUnexpectedInCompressedStorageB);
+
+                        // If we have entries, create a fake entry for the zero region.
+                        if (entry_count != 0) {
+                            // We need to have a physical size.
+                            R_UNLESS(entry.GetPhysicalSize() != 0,
+                                     ResultUnexpectedInCompressedStorageD);
+
+                            // Create a fake entry.
+                            entries[entry_count++] = {
+                                .compression_type = CompressionType::Zeros,
+                                .gap_from_prev = 0,
+                                .physical_size = 0,
+                                .virtual_size = static_cast<u32>(read_size),
+                            };
+                        } else {
+                            // We have no entries, so we can just perform the read.
+                            const Result rc =
+                                read_func(static_cast<size_t>(read_size),
+                                          [&](void* dst, size_t dst_size) -> Result {
+                                              // Check the space we should zero is correct.
+                                              ASSERT(dst_size == static_cast<size_t>(read_size));
+
+                                              // Zero the memory.
+                                              std::memset(dst, 0, read_size);
+                                              R_SUCCEED();
+                                          });
+                            if (R_FAILED(rc)) {
+                                R_THROW(rc);
+                            }
+                        }
+                    }
+
+                    // Set the previous entry.
+                    prev_entry = entry;
+
+                    // We're continuous.
+                    *out_continuous = true;
+                    R_SUCCEED();
+                }));
+
+            // If we still have a pending access, perform it.
+            if (required_access_physical_size != 0) {
+                R_TRY(PerformRequiredRead());
+            }
+
+            R_SUCCEED();
+        }
+
+    private:
+        DecompressorFunction GetDecompressor(CompressionType type) const {
+            // Check that we can get a decompressor for the type.
+            if (CompressionTypeUtility::IsUnknownType(type)) {
+                return nullptr;
+            }
+
+            // Get the decompressor.
+            return m_get_decompressor_function(type);
+        }
+
+        bool IsInitialized() const {
+            return m_table.IsInitialized();
+        }
+
+    private:
+        size_t m_block_size_max;
+        size_t m_continuous_reading_size_max;
+        BucketTree m_table;
+        VirtualFile m_data_storage;
+        GetDecompressorFunction m_get_decompressor_function;
+    };
+
+    class CacheManager {
+        YUZU_NON_COPYABLE(CacheManager);
+        YUZU_NON_MOVEABLE(CacheManager);
+
+    private:
+        struct AccessRange {
+            s64 virtual_offset;
+            s64 virtual_size;
+            u32 physical_size;
+            bool is_block_alignment_required;
+
+            s64 GetEndVirtualOffset() const {
+                return this->virtual_offset + this->virtual_size;
+            }
+        };
+        static_assert(std::is_trivial_v<AccessRange>);
+
+    public:
+        CacheManager() = default;
+
+    public:
+        Result Initialize(s64 storage_size, size_t cache_size_0, size_t cache_size_1,
+                          size_t max_cache_entries) {
+            // Set our fields.
+            m_storage_size = storage_size;
+
+            R_SUCCEED();
+        }
+
+        Result Read(CompressedStorageCore& core, s64 offset, void* buffer, size_t size) {
+            // If we have nothing to read, succeed.
+            R_SUCCEED_IF(size == 0);
+
+            // Check that we have a buffer to read into.
+            R_UNLESS(buffer != nullptr, ResultNullptrArgument);
+
+            // Check that the read is in bounds.
+            R_UNLESS(offset <= m_storage_size, ResultInvalidOffset);
+
+            // Determine how much we can read.
+            const size_t read_size = std::min<size_t>(size, m_storage_size - offset);
+
+            // Create head/tail ranges.
+            AccessRange head_range = {};
+            AccessRange tail_range = {};
+            bool is_tail_set = false;
+
+            // Operate to determine the head range.
+            R_TRY(core.OperatePerEntry(
+                offset, 1,
+                [&](bool* out_continuous, const Entry& entry, s64 virtual_data_size,
+                    s64 data_offset, s64 data_read_size) -> Result {
+                    // Set the head range.
+                    head_range = {
+                        .virtual_offset = entry.virt_offset,
+                        .virtual_size = virtual_data_size,
+                        .physical_size = static_cast<u32>(entry.phys_size),
+                        .is_block_alignment_required =
+                            CompressionTypeUtility::IsBlockAlignmentRequired(
+                                entry.compression_type),
+                    };
+
+                    // If required, set the tail range.
+                    if (static_cast<s64>(offset + read_size) <=
+                        entry.virt_offset + virtual_data_size) {
+                        tail_range = {
+                            .virtual_offset = entry.virt_offset,
+                            .virtual_size = virtual_data_size,
+                            .physical_size = static_cast<u32>(entry.phys_size),
+                            .is_block_alignment_required =
+                                CompressionTypeUtility::IsBlockAlignmentRequired(
+                                    entry.compression_type),
+                        };
+                        is_tail_set = true;
+                    }
+
+                    // We only want to determine the head range, so we're not continuous.
+                    *out_continuous = false;
+                    R_SUCCEED();
+                }));
+
+            // If necessary, determine the tail range.
+            if (!is_tail_set) {
+                R_TRY(core.OperatePerEntry(
+                    offset + read_size - 1, 1,
+                    [&](bool* out_continuous, const Entry& entry, s64 virtual_data_size,
+                        s64 data_offset, s64 data_read_size) -> Result {
+                        // Set the tail range.
+                        tail_range = {
+                            .virtual_offset = entry.virt_offset,
+                            .virtual_size = virtual_data_size,
+                            .physical_size = static_cast<u32>(entry.phys_size),
+                            .is_block_alignment_required =
+                                CompressionTypeUtility::IsBlockAlignmentRequired(
+                                    entry.compression_type),
+                        };
+
+                        // We only want to determine the tail range, so we're not continuous.
+                        *out_continuous = false;
+                        R_SUCCEED();
+                    }));
+            }
+
+            // Begin performing the accesses.
+            s64 cur_offset = offset;
+            size_t cur_size = read_size;
+            char* cur_dst = static_cast<char*>(buffer);
+
+            // Determine our alignment.
+            const bool head_unaligned = head_range.is_block_alignment_required &&
+                                        (cur_offset != head_range.virtual_offset ||
+                                         static_cast<s64>(cur_size) < head_range.virtual_size);
+            const bool tail_unaligned = [&]() -> bool {
+                if (tail_range.is_block_alignment_required) {
+                    if (static_cast<s64>(cur_size + cur_offset) ==
+                        tail_range.GetEndVirtualOffset()) {
+                        return false;
+                    } else if (!head_unaligned) {
+                        return true;
+                    } else {
+                        return head_range.GetEndVirtualOffset() <
+                               static_cast<s64>(cur_size + cur_offset);
+                    }
+                } else {
+                    return false;
+                }
+            }();
+
+            // Determine start/end offsets.
+            const s64 start_offset =
+                head_range.is_block_alignment_required ? head_range.virtual_offset : cur_offset;
+            const s64 end_offset = tail_range.is_block_alignment_required
+                                       ? tail_range.GetEndVirtualOffset()
+                                       : cur_offset + cur_size;
+
+            // Perform the read.
+            bool is_burst_reading = false;
+            R_TRY(core.Read(
+                start_offset, end_offset - start_offset,
+                [&](size_t size_buffer_required,
+                    const CompressedStorageCore::ReadImplFunction& read_impl) -> Result {
+                    // Determine whether we're burst reading.
+                    const AccessRange* unaligned_range = nullptr;
+                    if (!is_burst_reading) {
+                        // Check whether we're using head, tail, or none as unaligned.
+                        if (head_unaligned && head_range.virtual_offset <= cur_offset &&
+                            cur_offset < head_range.GetEndVirtualOffset()) {
+                            unaligned_range = std::addressof(head_range);
+                        } else if (tail_unaligned && tail_range.virtual_offset <= cur_offset &&
+                                   cur_offset < tail_range.GetEndVirtualOffset()) {
+                            unaligned_range = std::addressof(tail_range);
+                        } else {
+                            is_burst_reading = true;
+                        }
+                    }
+                    ASSERT((is_burst_reading ^ (unaligned_range != nullptr)));
+
+                    // Perform reading by burst, or not.
+                    if (is_burst_reading) {
+                        // Check that the access is valid for burst reading.
+                        ASSERT(size_buffer_required <= cur_size);
+
+                        // Perform the read.
+                        Result rc = read_impl(cur_dst, size_buffer_required);
+                        if (R_FAILED(rc)) {
+                            R_THROW(rc);
+                        }
+
+                        // Advance.
+                        cur_dst += size_buffer_required;
+                        cur_offset += size_buffer_required;
+                        cur_size -= size_buffer_required;
+
+                        // Determine whether we're going to continue burst reading.
+                        const s64 offset_aligned =
+                            tail_unaligned ? tail_range.virtual_offset : end_offset;
+                        ASSERT(cur_offset <= offset_aligned);
+
+                        if (offset_aligned <= cur_offset) {
+                            is_burst_reading = false;
+                        }
+                    } else {
+                        // We're not burst reading, so we have some unaligned range.
+                        ASSERT(unaligned_range != nullptr);
+
+                        // Check that the size is correct.
+                        ASSERT(size_buffer_required ==
+                               static_cast<size_t>(unaligned_range->virtual_size));
+
+                        // Get a pooled buffer for our read.
+                        PooledBuffer pooled_buffer;
+                        pooled_buffer.Allocate(size_buffer_required, size_buffer_required);
+
+                        // Perform read.
+                        Result rc = read_impl(pooled_buffer.GetBuffer(), size_buffer_required);
+                        if (R_FAILED(rc)) {
+                            R_THROW(rc);
+                        }
+
+                        // Copy the data we read to the destination.
+                        const size_t skip_size = cur_offset - unaligned_range->virtual_offset;
+                        const size_t copy_size = std::min<size_t>(
+                            cur_size, unaligned_range->GetEndVirtualOffset() - cur_offset);
+
+                        std::memcpy(cur_dst, pooled_buffer.GetBuffer() + skip_size, copy_size);
+
+                        // Advance.
+                        cur_dst += copy_size;
+                        cur_offset += copy_size;
+                        cur_size -= copy_size;
+                    }
+
+                    R_SUCCEED();
+                }));
+
+            R_SUCCEED();
+        }
+
+    private:
+        s64 m_storage_size = 0;
+    };
+
+public:
+    CompressedStorage() = default;
+    virtual ~CompressedStorage() {
+        this->Finalize();
+    }
+
+    Result Initialize(VirtualFile data_storage, VirtualFile node_storage, VirtualFile entry_storage,
+                      s32 bktr_entry_count, size_t block_size_max,
+                      size_t continuous_reading_size_max, GetDecompressorFunction get_decompressor,
+                      size_t cache_size_0, size_t cache_size_1, s32 max_cache_entries) {
+        // Initialize our core.
+        R_TRY(m_core.Initialize(data_storage, node_storage, entry_storage, bktr_entry_count,
+                                block_size_max, continuous_reading_size_max, get_decompressor));
+
+        // Get our core size.
+        s64 core_size = 0;
+        R_TRY(m_core.GetSize(std::addressof(core_size)));
+
+        // Initialize our cache manager.
+        R_TRY(m_cache_manager.Initialize(core_size, cache_size_0, cache_size_1, max_cache_entries));
+
+        R_SUCCEED();
+    }
+
+    void Finalize() {
+        m_core.Finalize();
+    }
+
+    VirtualFile GetDataStorage() {
+        return m_core.GetDataStorage();
+    }
+
+    Result GetDataStorageSize(s64* out) {
+        R_RETURN(m_core.GetDataStorageSize(out));
+    }
+
+    Result GetEntryList(Entry* out_entries, s32* out_read_count, s32 max_entry_count, s64 offset,
+                        s64 size) {
+        R_RETURN(m_core.GetEntryList(out_entries, out_read_count, max_entry_count, offset, size));
+    }
+
+    BucketTree& GetEntryTable() {
+        return m_core.GetEntryTable();
+    }
+
+public:
+    virtual size_t GetSize() const override {
+        s64 ret{};
+        m_core.GetSize(&ret);
+        return ret;
+    }
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+        if (R_SUCCEEDED(m_cache_manager.Read(m_core, offset, buffer, size))) {
+            return size;
+        } else {
+            return 0;
+        }
+    }
+
+private:
+    mutable CompressedStorageCore m_core;
+    mutable CacheManager m_cache_manager;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_compression_common.h

@@ -0,0 +1,43 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/hle/result.h"
+
+namespace FileSys {
+
+enum class CompressionType : u8 {
+    None = 0,
+    Zeros = 1,
+    Two = 2,
+    Lz4 = 3,
+    Unknown = 4,
+};
+
+using DecompressorFunction = Result (*)(void*, size_t, const void*, size_t);
+using GetDecompressorFunction = DecompressorFunction (*)(CompressionType);
+
+constexpr s64 CompressionBlockAlignment = 0x10;
+
+namespace CompressionTypeUtility {
+
+constexpr bool IsBlockAlignmentRequired(CompressionType type) {
+    return type != CompressionType::None && type != CompressionType::Zeros;
+}
+
+constexpr bool IsDataStorageAccessRequired(CompressionType type) {
+    return type != CompressionType::Zeros;
+}
+
+constexpr bool IsRandomAccessible(CompressionType type) {
+    return type == CompressionType::None;
+}
+
+constexpr bool IsUnknownType(CompressionType type) {
+    return type >= CompressionType::Unknown;
+}
+
+} // namespace CompressionTypeUtility
+
+} // namespace FileSys

core/fs/fssystem/fssystem_compression_configuration.cpp

@@ -0,0 +1,36 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/lz4_compression.h"
+#include "core/file_sys/fssystem/fssystem_compression_configuration.h"
+
+namespace FileSys {
+
+namespace {
+
+Result DecompressLz4(void* dst, size_t dst_size, const void* src, size_t src_size) {
+    auto result = Common::Compression::DecompressDataLZ4(dst, dst_size, src, src_size);
+    R_UNLESS(static_cast<size_t>(result) == dst_size, ResultUnexpectedInCompressedStorageC);
+    R_SUCCEED();
+}
+
+constexpr DecompressorFunction GetNcaDecompressorFunction(CompressionType type) {
+    switch (type) {
+    case CompressionType::Lz4:
+        return DecompressLz4;
+    default:
+        return nullptr;
+    }
+}
+
+} // namespace
+
+const NcaCompressionConfiguration& GetNcaCompressionConfiguration() {
+    static const NcaCompressionConfiguration configuration = {
+        .get_decompressor = GetNcaDecompressorFunction,
+    };
+
+    return configuration;
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_compression_configuration.h

@@ -0,0 +1,12 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fssystem_nca_file_system_driver.h"
+
+namespace FileSys {
+
+const NcaCompressionConfiguration& GetNcaCompressionConfiguration();
+
+}

core/fs/fssystem/fssystem_crypto_configuration.cpp

@@ -0,0 +1,65 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/crypto/aes_util.h"
+#include "core/crypto/key_manager.h"
+#include "core/file_sys/fssystem/fssystem_crypto_configuration.h"
+
+namespace FileSys {
+
+namespace {
+
+void GenerateKey(void* dst_key, size_t dst_key_size, const void* src_key, size_t src_key_size,
+                 s32 key_type) {
+    if (key_type == static_cast<s32>(KeyType::ZeroKey)) {
+        std::memset(dst_key, 0, dst_key_size);
+        return;
+    }
+
+    if (key_type == static_cast<s32>(KeyType::InvalidKey) ||
+        key_type < static_cast<s32>(KeyType::ZeroKey) ||
+        key_type >= static_cast<s32>(KeyType::NcaExternalKey)) {
+        std::memset(dst_key, 0xFF, dst_key_size);
+        return;
+    }
+
+    const auto& instance = Core::Crypto::KeyManager::Instance();
+
+    if (key_type == static_cast<s32>(KeyType::NcaHeaderKey1) ||
+        key_type == static_cast<s32>(KeyType::NcaHeaderKey2)) {
+        const s32 key_index = static_cast<s32>(KeyType::NcaHeaderKey2) == key_type;
+        const auto key = instance.GetKey(Core::Crypto::S256KeyType::Header);
+        std::memcpy(dst_key, key.data() + key_index * 0x10, std::min(dst_key_size, key.size() / 2));
+        return;
+    }
+
+    const s32 key_generation =
+        std::max(key_type / NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexCount, 1) - 1;
+    const s32 key_index = key_type % NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexCount;
+
+    Core::Crypto::AESCipher<Core::Crypto::Key128> cipher(
+        instance.GetKey(Core::Crypto::S128KeyType::KeyArea, key_generation, key_index),
+        Core::Crypto::Mode::ECB);
+    cipher.Transcode(reinterpret_cast<const u8*>(src_key), src_key_size,
+                     reinterpret_cast<u8*>(dst_key), Core::Crypto::Op::Decrypt);
+}
+
+} // namespace
+
+const NcaCryptoConfiguration& GetCryptoConfiguration() {
+    static const NcaCryptoConfiguration configuration = {
+        .header_1_sign_key_moduli{},
+        .header_1_sign_key_public_exponent{},
+        .key_area_encryption_key_source{},
+        .header_encryption_key_source{},
+        .header_encrypted_encryption_keys{},
+        .generate_key = GenerateKey,
+        .verify_sign1{},
+        .is_plaintext_header_available{},
+        .is_available_sw_key{},
+    };
+
+    return configuration;
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_crypto_configuration.h

@@ -0,0 +1,12 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fssystem_nca_file_system_driver.h"
+
+namespace FileSys {
+
+const NcaCryptoConfiguration& GetCryptoConfiguration();
+
+}

core/fs/fssystem/fssystem_hierarchical_integrity_verification_storage.cpp

@@ -0,0 +1,127 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/fssystem/fssystem_hierarchical_integrity_verification_storage.h"
+#include "core/file_sys/vfs/vfs_offset.h"
+
+namespace FileSys {
+
+HierarchicalIntegrityVerificationStorage::HierarchicalIntegrityVerificationStorage()
+    : m_data_size(-1) {
+    for (size_t i = 0; i < MaxLayers - 1; i++) {
+        m_verify_storages[i] = std::make_shared<IntegrityVerificationStorage>();
+    }
+}
+
+Result HierarchicalIntegrityVerificationStorage::Initialize(
+    const HierarchicalIntegrityVerificationInformation& info,
+    HierarchicalStorageInformation storage, int max_data_cache_entries, int max_hash_cache_entries,
+    s8 buffer_level) {
+    // Validate preconditions.
+    ASSERT(IntegrityMinLayerCount <= info.max_layers && info.max_layers <= IntegrityMaxLayerCount);
+
+    // Set member variables.
+    m_max_layers = info.max_layers;
+
+    // Initialize the top level verification storage.
+    m_verify_storages[0]->Initialize(storage[HierarchicalStorageInformation::MasterStorage],
+                                     storage[HierarchicalStorageInformation::Layer1Storage],
+                                     static_cast<s64>(1) << info.info[0].block_order, HashSize,
+                                     false);
+
+    // Ensure we don't leak state if further initialization goes wrong.
+    ON_RESULT_FAILURE {
+        m_verify_storages[0]->Finalize();
+        m_data_size = -1;
+    };
+
+    // Initialize the top level buffer storage.
+    m_buffer_storages[0] = m_verify_storages[0];
+    R_UNLESS(m_buffer_storages[0] != nullptr, ResultAllocationMemoryFailedAllocateShared);
+
+    // Prepare to initialize the level storages.
+    s32 level = 0;
+
+    // Ensure we don't leak state if further initialization goes wrong.
+    ON_RESULT_FAILURE_2 {
+        m_verify_storages[level + 1]->Finalize();
+        for (; level > 0; --level) {
+            m_buffer_storages[level].reset();
+            m_verify_storages[level]->Finalize();
+        }
+    };
+
+    // Initialize the level storages.
+    for (; level < m_max_layers - 3; ++level) {
+        // Initialize the verification storage.
+        auto buffer_storage =
+            std::make_shared<OffsetVfsFile>(m_buffer_storages[level], info.info[level].size, 0);
+        m_verify_storages[level + 1]->Initialize(
+            std::move(buffer_storage), storage[level + 2],
+            static_cast<s64>(1) << info.info[level + 1].block_order,
+            static_cast<s64>(1) << info.info[level].block_order, false);
+
+        // Initialize the buffer storage.
+        m_buffer_storages[level + 1] = m_verify_storages[level + 1];
+        R_UNLESS(m_buffer_storages[level + 1] != nullptr,
+                 ResultAllocationMemoryFailedAllocateShared);
+    }
+
+    // Initialize the final level storage.
+    {
+        // Initialize the verification storage.
+        auto buffer_storage =
+            std::make_shared<OffsetVfsFile>(m_buffer_storages[level], info.info[level].size, 0);
+        m_verify_storages[level + 1]->Initialize(
+            std::move(buffer_storage), storage[level + 2],
+            static_cast<s64>(1) << info.info[level + 1].block_order,
+            static_cast<s64>(1) << info.info[level].block_order, true);
+
+        // Initialize the buffer storage.
+        m_buffer_storages[level + 1] = m_verify_storages[level + 1];
+        R_UNLESS(m_buffer_storages[level + 1] != nullptr,
+                 ResultAllocationMemoryFailedAllocateShared);
+    }
+
+    // Set the data size.
+    m_data_size = info.info[level + 1].size;
+
+    // We succeeded.
+    R_SUCCEED();
+}
+
+void HierarchicalIntegrityVerificationStorage::Finalize() {
+    if (m_data_size >= 0) {
+        m_data_size = 0;
+
+        for (s32 level = m_max_layers - 2; level >= 0; --level) {
+            m_buffer_storages[level].reset();
+            m_verify_storages[level]->Finalize();
+        }
+
+        m_data_size = -1;
+    }
+}
+
+size_t HierarchicalIntegrityVerificationStorage::Read(u8* buffer, size_t size,
+                                                      size_t offset) const {
+    // Validate preconditions.
+    ASSERT(m_data_size >= 0);
+
+    // Succeed if zero-size.
+    if (size == 0) {
+        return size;
+    }
+
+    // Validate arguments.
+    ASSERT(buffer != nullptr);
+
+    // Read the data.
+    return m_buffer_storages[m_max_layers - 2]->Read(buffer, size, offset);
+}
+
+size_t HierarchicalIntegrityVerificationStorage::GetSize() const {
+    return m_data_size;
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_hierarchical_integrity_verification_storage.h

@@ -0,0 +1,164 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/alignment.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/fssystem/fs_types.h"
+#include "core/file_sys/fssystem/fssystem_alignment_matching_storage.h"
+#include "core/file_sys/fssystem/fssystem_integrity_verification_storage.h"
+#include "core/file_sys/vfs/vfs_offset.h"
+
+namespace FileSys {
+
+struct HierarchicalIntegrityVerificationLevelInformation {
+    Int64 offset;
+    Int64 size;
+    s32 block_order;
+    std::array<u8, 4> reserved;
+};
+static_assert(std::is_trivial_v<HierarchicalIntegrityVerificationLevelInformation>);
+static_assert(sizeof(HierarchicalIntegrityVerificationLevelInformation) == 0x18);
+static_assert(alignof(HierarchicalIntegrityVerificationLevelInformation) == 0x4);
+
+struct HierarchicalIntegrityVerificationInformation {
+    u32 max_layers;
+    std::array<HierarchicalIntegrityVerificationLevelInformation, IntegrityMaxLayerCount - 1> info;
+    HashSalt seed;
+
+    s64 GetLayeredHashSize() const {
+        return this->info[this->max_layers - 2].offset;
+    }
+
+    s64 GetDataOffset() const {
+        return this->info[this->max_layers - 2].offset;
+    }
+
+    s64 GetDataSize() const {
+        return this->info[this->max_layers - 2].size;
+    }
+};
+static_assert(std::is_trivial_v<HierarchicalIntegrityVerificationInformation>);
+
+struct HierarchicalIntegrityVerificationMetaInformation {
+    u32 magic;
+    u32 version;
+    u32 master_hash_size;
+    HierarchicalIntegrityVerificationInformation level_hash_info;
+};
+static_assert(std::is_trivial_v<HierarchicalIntegrityVerificationMetaInformation>);
+
+struct HierarchicalIntegrityVerificationSizeSet {
+    s64 control_size;
+    s64 master_hash_size;
+    std::array<s64, IntegrityMaxLayerCount - 2> layered_hash_sizes;
+};
+static_assert(std::is_trivial_v<HierarchicalIntegrityVerificationSizeSet>);
+
+class HierarchicalIntegrityVerificationStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(HierarchicalIntegrityVerificationStorage);
+    YUZU_NON_MOVEABLE(HierarchicalIntegrityVerificationStorage);
+
+public:
+    using GenerateRandomFunction = void (*)(void* dst, size_t size);
+
+    class HierarchicalStorageInformation {
+    public:
+        enum {
+            MasterStorage = 0,
+            Layer1Storage = 1,
+            Layer2Storage = 2,
+            Layer3Storage = 3,
+            Layer4Storage = 4,
+            Layer5Storage = 5,
+            DataStorage = 6,
+        };
+
+    private:
+        std::array<VirtualFile, DataStorage + 1> m_storages;
+
+    public:
+        void SetMasterHashStorage(VirtualFile s) {
+            m_storages[MasterStorage] = s;
+        }
+        void SetLayer1HashStorage(VirtualFile s) {
+            m_storages[Layer1Storage] = s;
+        }
+        void SetLayer2HashStorage(VirtualFile s) {
+            m_storages[Layer2Storage] = s;
+        }
+        void SetLayer3HashStorage(VirtualFile s) {
+            m_storages[Layer3Storage] = s;
+        }
+        void SetLayer4HashStorage(VirtualFile s) {
+            m_storages[Layer4Storage] = s;
+        }
+        void SetLayer5HashStorage(VirtualFile s) {
+            m_storages[Layer5Storage] = s;
+        }
+        void SetDataStorage(VirtualFile s) {
+            m_storages[DataStorage] = s;
+        }
+
+        VirtualFile& operator[](s32 index) {
+            ASSERT(MasterStorage <= index && index <= DataStorage);
+            return m_storages[index];
+        }
+    };
+
+public:
+    HierarchicalIntegrityVerificationStorage();
+    virtual ~HierarchicalIntegrityVerificationStorage() override {
+        this->Finalize();
+    }
+
+    Result Initialize(const HierarchicalIntegrityVerificationInformation& info,
+                      HierarchicalStorageInformation storage, int max_data_cache_entries,
+                      int max_hash_cache_entries, s8 buffer_level);
+    void Finalize();
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+    virtual size_t GetSize() const override;
+
+    bool IsInitialized() const {
+        return m_data_size >= 0;
+    }
+
+    s64 GetL1HashVerificationBlockSize() const {
+        return m_verify_storages[m_max_layers - 2]->GetBlockSize();
+    }
+
+    VirtualFile GetL1HashStorage() {
+        return std::make_shared<OffsetVfsFile>(
+            m_buffer_storages[m_max_layers - 3],
+            Common::DivideUp(m_data_size, this->GetL1HashVerificationBlockSize()), 0);
+    }
+
+public:
+    static constexpr s8 GetDefaultDataCacheBufferLevel(u32 max_layers) {
+        return static_cast<s8>(16 + max_layers - 2);
+    }
+
+protected:
+    static constexpr s64 HashSize = 256 / 8;
+    static constexpr size_t MaxLayers = IntegrityMaxLayerCount;
+
+private:
+    static GenerateRandomFunction s_generate_random;
+
+    static void SetGenerateRandomFunction(GenerateRandomFunction func) {
+        s_generate_random = func;
+    }
+
+private:
+    friend struct HierarchicalIntegrityVerificationMetaInformation;
+
+private:
+    std::array<std::shared_ptr<IntegrityVerificationStorage>, MaxLayers - 1> m_verify_storages;
+    std::array<VirtualFile, MaxLayers - 1> m_buffer_storages;
+    s64 m_data_size;
+    s32 m_max_layers;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_hierarchical_sha256_storage.cpp

@@ -0,0 +1,82 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/alignment.h"
+#include "common/scope_exit.h"
+#include "core/file_sys/fssystem/fssystem_hierarchical_sha256_storage.h"
+
+namespace FileSys {
+
+namespace {
+
+s32 Log2(s32 value) {
+    ASSERT(value > 0);
+    ASSERT(Common::IsPowerOfTwo(value));
+
+    s32 log = 0;
+    while ((value >>= 1) > 0) {
+        ++log;
+    }
+    return log;
+}
+
+} // namespace
+
+Result HierarchicalSha256Storage::Initialize(VirtualFile* base_storages, s32 layer_count,
+                                             size_t htbs, void* hash_buf, size_t hash_buf_size) {
+    // Validate preconditions.
+    ASSERT(layer_count == LayerCount);
+    ASSERT(Common::IsPowerOfTwo(htbs));
+    ASSERT(hash_buf != nullptr);
+
+    // Set size tracking members.
+    m_hash_target_block_size = static_cast<s32>(htbs);
+    m_log_size_ratio = Log2(m_hash_target_block_size / HashSize);
+
+    // Get the base storage size.
+    m_base_storage_size = base_storages[2]->GetSize();
+    {
+        auto size_guard = SCOPE_GUARD {
+            m_base_storage_size = 0;
+        };
+        R_UNLESS(m_base_storage_size <= static_cast<s64>(HashSize)
+                                            << m_log_size_ratio << m_log_size_ratio,
+                 ResultHierarchicalSha256BaseStorageTooLarge);
+        size_guard.Cancel();
+    }
+
+    // Set hash buffer tracking members.
+    m_base_storage = base_storages[2];
+    m_hash_buffer = static_cast<char*>(hash_buf);
+    m_hash_buffer_size = hash_buf_size;
+
+    // Read the master hash.
+    std::array<u8, HashSize> master_hash{};
+    base_storages[0]->ReadObject(std::addressof(master_hash));
+
+    // Read and validate the data being hashed.
+    s64 hash_storage_size = base_storages[1]->GetSize();
+    ASSERT(Common::IsAligned(hash_storage_size, HashSize));
+    ASSERT(hash_storage_size <= m_hash_target_block_size);
+    ASSERT(hash_storage_size <= static_cast<s64>(m_hash_buffer_size));
+
+    base_storages[1]->Read(reinterpret_cast<u8*>(m_hash_buffer),
+                           static_cast<size_t>(hash_storage_size), 0);
+
+    R_SUCCEED();
+}
+
+size_t HierarchicalSha256Storage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Succeed if zero-size.
+    if (size == 0) {
+        return size;
+    }
+
+    // Validate that we have a buffer to read into.
+    ASSERT(buffer != nullptr);
+
+    // Read the data.
+    return m_base_storage->Read(buffer, size, offset);
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_hierarchical_sha256_storage.h

@@ -0,0 +1,44 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <mutex>
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+
+class HierarchicalSha256Storage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(HierarchicalSha256Storage);
+    YUZU_NON_MOVEABLE(HierarchicalSha256Storage);
+
+public:
+    static constexpr s32 LayerCount = 3;
+    static constexpr size_t HashSize = 256 / 8;
+
+public:
+    HierarchicalSha256Storage() : m_mutex() {}
+
+    Result Initialize(VirtualFile* base_storages, s32 layer_count, size_t htbs, void* hash_buf,
+                      size_t hash_buf_size);
+
+    virtual size_t GetSize() const override {
+        return m_base_storage->GetSize();
+    }
+
+    virtual size_t Read(u8* buffer, size_t length, size_t offset) const override;
+
+private:
+    VirtualFile m_base_storage;
+    s64 m_base_storage_size;
+    char* m_hash_buffer;
+    size_t m_hash_buffer_size;
+    s32 m_hash_target_block_size;
+    s32 m_log_size_ratio;
+    std::mutex m_mutex;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_indirect_storage.cpp

@@ -0,0 +1,119 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fssystem_indirect_storage.h"
+
+namespace FileSys {
+
+Result IndirectStorage::Initialize(VirtualFile table_storage) {
+    // Read and verify the bucket tree header.
+    BucketTree::Header header;
+    table_storage->ReadObject(std::addressof(header));
+    R_TRY(header.Verify());
+
+    // Determine extents.
+    const auto node_storage_size = QueryNodeStorageSize(header.entry_count);
+    const auto entry_storage_size = QueryEntryStorageSize(header.entry_count);
+    const auto node_storage_offset = QueryHeaderStorageSize();
+    const auto entry_storage_offset = node_storage_offset + node_storage_size;
+
+    // Initialize.
+    R_RETURN(this->Initialize(
+        std::make_shared<OffsetVfsFile>(table_storage, node_storage_size, node_storage_offset),
+        std::make_shared<OffsetVfsFile>(table_storage, entry_storage_size, entry_storage_offset),
+        header.entry_count));
+}
+
+void IndirectStorage::Finalize() {
+    if (this->IsInitialized()) {
+        m_table.Finalize();
+        for (auto i = 0; i < StorageCount; i++) {
+            m_data_storage[i] = VirtualFile();
+        }
+    }
+}
+
+Result IndirectStorage::GetEntryList(Entry* out_entries, s32* out_entry_count, s32 entry_count,
+                                     s64 offset, s64 size) {
+    // Validate pre-conditions.
+    ASSERT(offset >= 0);
+    ASSERT(size >= 0);
+    ASSERT(this->IsInitialized());
+
+    // Clear the out count.
+    R_UNLESS(out_entry_count != nullptr, ResultNullptrArgument);
+    *out_entry_count = 0;
+
+    // Succeed if there's no range.
+    R_SUCCEED_IF(size == 0);
+
+    // If we have an output array, we need it to be non-null.
+    R_UNLESS(out_entries != nullptr || entry_count == 0, ResultNullptrArgument);
+
+    // Check that our range is valid.
+    BucketTree::Offsets table_offsets;
+    R_TRY(m_table.GetOffsets(std::addressof(table_offsets)));
+
+    R_UNLESS(table_offsets.IsInclude(offset, size), ResultOutOfRange);
+
+    // Find the offset in our tree.
+    BucketTree::Visitor visitor;
+    R_TRY(m_table.Find(std::addressof(visitor), offset));
+    {
+        const auto entry_offset = visitor.Get<Entry>()->GetVirtualOffset();
+        R_UNLESS(0 <= entry_offset && table_offsets.IsInclude(entry_offset),
+                 ResultInvalidIndirectEntryOffset);
+    }
+
+    // Prepare to loop over entries.
+    const auto end_offset = offset + static_cast<s64>(size);
+    s32 count = 0;
+
+    auto cur_entry = *visitor.Get<Entry>();
+    while (cur_entry.GetVirtualOffset() < end_offset) {
+        // Try to write the entry to the out list.
+        if (entry_count != 0) {
+            if (count >= entry_count) {
+                break;
+            }
+            std::memcpy(out_entries + count, std::addressof(cur_entry), sizeof(Entry));
+        }
+
+        count++;
+
+        // Advance.
+        if (visitor.CanMoveNext()) {
+            R_TRY(visitor.MoveNext());
+            cur_entry = *visitor.Get<Entry>();
+        } else {
+            break;
+        }
+    }
+
+    // Write the output count.
+    *out_entry_count = count;
+    R_SUCCEED();
+}
+
+size_t IndirectStorage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Validate pre-conditions.
+    ASSERT(this->IsInitialized());
+    ASSERT(buffer != nullptr);
+
+    // Succeed if there's nothing to read.
+    if (size == 0) {
+        return 0;
+    }
+
+    const_cast<IndirectStorage*>(this)->OperatePerEntry<true, true>(
+        offset, size,
+        [=](VirtualFile storage, s64 data_offset, s64 cur_offset, s64 cur_size) -> Result {
+            storage->Read(reinterpret_cast<u8*>(buffer) + (cur_offset - offset),
+                          static_cast<size_t>(cur_size), data_offset);
+            R_SUCCEED();
+        });
+
+    return size;
+}
+} // namespace FileSys

core/fs/fssystem/fssystem_indirect_storage.h

@@ -0,0 +1,294 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree.h"
+#include "core/file_sys/fssystem/fssystem_bucket_tree_template_impl.h"
+#include "core/file_sys/vfs/vfs.h"
+#include "core/file_sys/vfs/vfs_offset.h"
+
+namespace FileSys {
+
+class IndirectStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(IndirectStorage);
+    YUZU_NON_MOVEABLE(IndirectStorage);
+
+public:
+    static constexpr s32 StorageCount = 2;
+    static constexpr size_t NodeSize = 16_KiB;
+
+    struct Entry {
+        std::array<u8, sizeof(s64)> virt_offset;
+        std::array<u8, sizeof(s64)> phys_offset;
+        s32 storage_index;
+
+        void SetVirtualOffset(const s64& ofs) {
+            std::memcpy(this->virt_offset.data(), std::addressof(ofs), sizeof(s64));
+        }
+
+        s64 GetVirtualOffset() const {
+            s64 offset;
+            std::memcpy(std::addressof(offset), this->virt_offset.data(), sizeof(s64));
+            return offset;
+        }
+
+        void SetPhysicalOffset(const s64& ofs) {
+            std::memcpy(this->phys_offset.data(), std::addressof(ofs), sizeof(s64));
+        }
+
+        s64 GetPhysicalOffset() const {
+            s64 offset;
+            std::memcpy(std::addressof(offset), this->phys_offset.data(), sizeof(s64));
+            return offset;
+        }
+    };
+    static_assert(std::is_trivial_v<Entry>);
+    static_assert(sizeof(Entry) == 0x14);
+
+    struct EntryData {
+        s64 virt_offset;
+        s64 phys_offset;
+        s32 storage_index;
+
+        void Set(const Entry& entry) {
+            this->virt_offset = entry.GetVirtualOffset();
+            this->phys_offset = entry.GetPhysicalOffset();
+            this->storage_index = entry.storage_index;
+        }
+    };
+    static_assert(std::is_trivial_v<EntryData>);
+
+public:
+    IndirectStorage() : m_table(), m_data_storage() {}
+    virtual ~IndirectStorage() {
+        this->Finalize();
+    }
+
+    Result Initialize(VirtualFile table_storage);
+    void Finalize();
+
+    bool IsInitialized() const {
+        return m_table.IsInitialized();
+    }
+
+    Result Initialize(VirtualFile node_storage, VirtualFile entry_storage, s32 entry_count) {
+        R_RETURN(
+            m_table.Initialize(node_storage, entry_storage, NodeSize, sizeof(Entry), entry_count));
+    }
+
+    void SetStorage(s32 idx, VirtualFile storage) {
+        ASSERT(0 <= idx && idx < StorageCount);
+        m_data_storage[idx] = storage;
+    }
+
+    template <typename T>
+    void SetStorage(s32 idx, T storage, s64 offset, s64 size) {
+        ASSERT(0 <= idx && idx < StorageCount);
+        m_data_storage[idx] = std::make_shared<OffsetVfsFile>(storage, size, offset);
+    }
+
+    Result GetEntryList(Entry* out_entries, s32* out_entry_count, s32 entry_count, s64 offset,
+                        s64 size);
+
+    virtual size_t GetSize() const override {
+        BucketTree::Offsets offsets{};
+        m_table.GetOffsets(std::addressof(offsets));
+
+        return offsets.end_offset;
+    }
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+
+public:
+    static constexpr s64 QueryHeaderStorageSize() {
+        return BucketTree::QueryHeaderStorageSize();
+    }
+
+    static constexpr s64 QueryNodeStorageSize(s32 entry_count) {
+        return BucketTree::QueryNodeStorageSize(NodeSize, sizeof(Entry), entry_count);
+    }
+
+    static constexpr s64 QueryEntryStorageSize(s32 entry_count) {
+        return BucketTree::QueryEntryStorageSize(NodeSize, sizeof(Entry), entry_count);
+    }
+
+protected:
+    BucketTree& GetEntryTable() {
+        return m_table;
+    }
+
+    VirtualFile& GetDataStorage(s32 index) {
+        ASSERT(0 <= index && index < StorageCount);
+        return m_data_storage[index];
+    }
+
+    template <bool ContinuousCheck, bool RangeCheck, typename F>
+    Result OperatePerEntry(s64 offset, s64 size, F func);
+
+private:
+    struct ContinuousReadingEntry {
+        static constexpr size_t FragmentSizeMax = 4_KiB;
+
+        IndirectStorage::Entry entry;
+
+        s64 GetVirtualOffset() const {
+            return this->entry.GetVirtualOffset();
+        }
+
+        s64 GetPhysicalOffset() const {
+            return this->entry.GetPhysicalOffset();
+        }
+
+        bool IsFragment() const {
+            return this->entry.storage_index != 0;
+        }
+    };
+    static_assert(std::is_trivial_v<ContinuousReadingEntry>);
+
+private:
+    mutable BucketTree m_table;
+    std::array<VirtualFile, StorageCount> m_data_storage;
+};
+
+template <bool ContinuousCheck, bool RangeCheck, typename F>
+Result IndirectStorage::OperatePerEntry(s64 offset, s64 size, F func) {
+    // Validate preconditions.
+    ASSERT(offset >= 0);
+    ASSERT(size >= 0);
+    ASSERT(this->IsInitialized());
+
+    // Succeed if there's nothing to operate on.
+    R_SUCCEED_IF(size == 0);
+
+    // Get the table offsets.
+    BucketTree::Offsets table_offsets;
+    R_TRY(m_table.GetOffsets(std::addressof(table_offsets)));
+
+    // Validate arguments.
+    R_UNLESS(table_offsets.IsInclude(offset, size), ResultOutOfRange);
+
+    // Find the offset in our tree.
+    BucketTree::Visitor visitor;
+    R_TRY(m_table.Find(std::addressof(visitor), offset));
+    {
+        const auto entry_offset = visitor.Get<Entry>()->GetVirtualOffset();
+        R_UNLESS(0 <= entry_offset && table_offsets.IsInclude(entry_offset),
+                 ResultInvalidIndirectEntryOffset);
+    }
+
+    // Prepare to operate in chunks.
+    auto cur_offset = offset;
+    const auto end_offset = offset + static_cast<s64>(size);
+    BucketTree::ContinuousReadingInfo cr_info;
+
+    while (cur_offset < end_offset) {
+        // Get the current entry.
+        const auto cur_entry = *visitor.Get<Entry>();
+
+        // Get and validate the entry's offset.
+        const auto cur_entry_offset = cur_entry.GetVirtualOffset();
+        R_UNLESS(cur_entry_offset <= cur_offset, ResultInvalidIndirectEntryOffset);
+
+        // Validate the storage index.
+        R_UNLESS(0 <= cur_entry.storage_index && cur_entry.storage_index < StorageCount,
+                 ResultInvalidIndirectEntryStorageIndex);
+
+        // If we need to check the continuous info, do so.
+        if constexpr (ContinuousCheck) {
+            // Scan, if we need to.
+            if (cr_info.CheckNeedScan()) {
+                R_TRY(visitor.ScanContinuousReading<ContinuousReadingEntry>(
+                    std::addressof(cr_info), cur_offset,
+                    static_cast<size_t>(end_offset - cur_offset)));
+            }
+
+            // Process a base storage entry.
+            if (cr_info.CanDo()) {
+                // Ensure that we can process.
+                R_UNLESS(cur_entry.storage_index == 0, ResultInvalidIndirectEntryStorageIndex);
+
+                // Ensure that we remain within range.
+                const auto data_offset = cur_offset - cur_entry_offset;
+                const auto cur_entry_phys_offset = cur_entry.GetPhysicalOffset();
+                const auto cur_size = static_cast<s64>(cr_info.GetReadSize());
+
+                // If we should, verify the range.
+                if constexpr (RangeCheck) {
+                    // Get the current data storage's size.
+                    s64 cur_data_storage_size = m_data_storage[0]->GetSize();
+
+                    R_UNLESS(0 <= cur_entry_phys_offset &&
+                                 cur_entry_phys_offset <= cur_data_storage_size,
+                             ResultInvalidIndirectEntryOffset);
+                    R_UNLESS(cur_entry_phys_offset + data_offset + cur_size <=
+                                 cur_data_storage_size,
+                             ResultInvalidIndirectStorageSize);
+                }
+
+                // Operate.
+                R_TRY(func(m_data_storage[0], cur_entry_phys_offset + data_offset, cur_offset,
+                           cur_size));
+
+                // Mark as done.
+                cr_info.Done();
+            }
+        }
+
+        // Get and validate the next entry offset.
+        s64 next_entry_offset;
+        if (visitor.CanMoveNext()) {
+            R_TRY(visitor.MoveNext());
+            next_entry_offset = visitor.Get<Entry>()->GetVirtualOffset();
+            R_UNLESS(table_offsets.IsInclude(next_entry_offset), ResultInvalidIndirectEntryOffset);
+        } else {
+            next_entry_offset = table_offsets.end_offset;
+        }
+        R_UNLESS(cur_offset < next_entry_offset, ResultInvalidIndirectEntryOffset);
+
+        // Get the offset of the entry in the data we read.
+        const auto data_offset = cur_offset - cur_entry_offset;
+        const auto data_size = (next_entry_offset - cur_entry_offset);
+        ASSERT(data_size > 0);
+
+        // Determine how much is left.
+        const auto remaining_size = end_offset - cur_offset;
+        const auto cur_size = std::min<s64>(remaining_size, data_size - data_offset);
+        ASSERT(cur_size <= size);
+
+        // Operate, if we need to.
+        bool needs_operate;
+        if constexpr (!ContinuousCheck) {
+            needs_operate = true;
+        } else {
+            needs_operate = !cr_info.IsDone() || cur_entry.storage_index != 0;
+        }
+
+        if (needs_operate) {
+            const auto cur_entry_phys_offset = cur_entry.GetPhysicalOffset();
+
+            if constexpr (RangeCheck) {
+                // Get the current data storage's size.
+                s64 cur_data_storage_size = m_data_storage[cur_entry.storage_index]->GetSize();
+
+                // Ensure that we remain within range.
+                R_UNLESS(0 <= cur_entry_phys_offset &&
+                             cur_entry_phys_offset <= cur_data_storage_size,
+                         ResultIndirectStorageCorrupted);
+                R_UNLESS(cur_entry_phys_offset + data_offset + cur_size <= cur_data_storage_size,
+                         ResultIndirectStorageCorrupted);
+            }
+
+            R_TRY(func(m_data_storage[cur_entry.storage_index], cur_entry_phys_offset + data_offset,
+                       cur_offset, cur_size));
+        }
+
+        cur_offset += cur_size;
+    }
+
+    R_SUCCEED();
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_integrity_romfs_storage.cpp

@@ -0,0 +1,30 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/fssystem/fssystem_integrity_romfs_storage.h"
+
+namespace FileSys {
+
+Result IntegrityRomFsStorage::Initialize(
+    HierarchicalIntegrityVerificationInformation level_hash_info, Hash master_hash,
+    HierarchicalIntegrityVerificationStorage::HierarchicalStorageInformation storage_info,
+    int max_data_cache_entries, int max_hash_cache_entries, s8 buffer_level) {
+    // Set master hash.
+    m_master_hash = master_hash;
+    m_master_hash_storage = std::make_shared<ArrayVfsFile<sizeof(Hash)>>(m_master_hash.value);
+    R_UNLESS(m_master_hash_storage != nullptr,
+             ResultAllocationMemoryFailedInIntegrityRomFsStorageA);
+
+    // Set the master hash storage.
+    storage_info[0] = m_master_hash_storage;
+
+    // Initialize our integrity storage.
+    R_RETURN(m_integrity_storage.Initialize(level_hash_info, storage_info, max_data_cache_entries,
+                                            max_hash_cache_entries, buffer_level));
+}
+
+void IntegrityRomFsStorage::Finalize() {
+    m_integrity_storage.Finalize();
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_integrity_romfs_storage.h

@@ -0,0 +1,42 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fssystem_hierarchical_integrity_verification_storage.h"
+#include "core/file_sys/fssystem/fssystem_nca_header.h"
+#include "core/file_sys/vfs/vfs_vector.h"
+
+namespace FileSys {
+
+constexpr inline size_t IntegrityLayerCountRomFs = 7;
+constexpr inline size_t IntegrityHashLayerBlockSize = 16_KiB;
+
+class IntegrityRomFsStorage : public IReadOnlyStorage {
+public:
+    IntegrityRomFsStorage() {}
+    virtual ~IntegrityRomFsStorage() override {
+        this->Finalize();
+    }
+
+    Result Initialize(
+        HierarchicalIntegrityVerificationInformation level_hash_info, Hash master_hash,
+        HierarchicalIntegrityVerificationStorage::HierarchicalStorageInformation storage_info,
+        int max_data_cache_entries, int max_hash_cache_entries, s8 buffer_level);
+    void Finalize();
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+        return m_integrity_storage.Read(buffer, size, offset);
+    }
+
+    virtual size_t GetSize() const override {
+        return m_integrity_storage.GetSize();
+    }
+
+private:
+    HierarchicalIntegrityVerificationStorage m_integrity_storage;
+    Hash m_master_hash;
+    std::shared_ptr<ArrayVfsFile<sizeof(Hash)>> m_master_hash_storage;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_integrity_verification_storage.cpp

@@ -0,0 +1,91 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/alignment.h"
+#include "core/file_sys/fssystem/fssystem_integrity_verification_storage.h"
+
+namespace FileSys {
+
+constexpr inline u32 ILog2(u32 val) {
+    ASSERT(val > 0);
+    return static_cast<u32>((sizeof(u32) * 8) - 1 - std::countl_zero<u32>(val));
+}
+
+void IntegrityVerificationStorage::Initialize(VirtualFile hs, VirtualFile ds, s64 verif_block_size,
+                                              s64 upper_layer_verif_block_size, bool is_real_data) {
+    // Validate preconditions.
+    ASSERT(verif_block_size >= HashSize);
+
+    // Set storages.
+    m_hash_storage = hs;
+    m_data_storage = ds;
+
+    // Set verification block sizes.
+    m_verification_block_size = verif_block_size;
+    m_verification_block_order = ILog2(static_cast<u32>(verif_block_size));
+    ASSERT(m_verification_block_size == 1ll << m_verification_block_order);
+
+    // Set upper layer block sizes.
+    upper_layer_verif_block_size = std::max(upper_layer_verif_block_size, HashSize);
+    m_upper_layer_verification_block_size = upper_layer_verif_block_size;
+    m_upper_layer_verification_block_order = ILog2(static_cast<u32>(upper_layer_verif_block_size));
+    ASSERT(m_upper_layer_verification_block_size == 1ll << m_upper_layer_verification_block_order);
+
+    // Validate sizes.
+    {
+        s64 hash_size = m_hash_storage->GetSize();
+        s64 data_size = m_data_storage->GetSize();
+        ASSERT(((hash_size / HashSize) * m_verification_block_size) >= data_size);
+    }
+
+    // Set data.
+    m_is_real_data = is_real_data;
+}
+
+void IntegrityVerificationStorage::Finalize() {
+    m_hash_storage = VirtualFile();
+    m_data_storage = VirtualFile();
+}
+
+size_t IntegrityVerificationStorage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Succeed if zero size.
+    if (size == 0) {
+        return size;
+    }
+
+    // Validate arguments.
+    ASSERT(buffer != nullptr);
+
+    // Validate the offset.
+    s64 data_size = m_data_storage->GetSize();
+    ASSERT(offset <= static_cast<size_t>(data_size));
+
+    // Validate the access range.
+    ASSERT(R_SUCCEEDED(IStorage::CheckAccessRange(
+        offset, size, Common::AlignUp(data_size, static_cast<size_t>(m_verification_block_size)))));
+
+    // Determine the read extents.
+    size_t read_size = size;
+    if (static_cast<s64>(offset + read_size) > data_size) {
+        // Determine the padding sizes.
+        s64 padding_offset = data_size - offset;
+        size_t padding_size = static_cast<size_t>(
+            m_verification_block_size - (padding_offset & (m_verification_block_size - 1)));
+        ASSERT(static_cast<s64>(padding_size) < m_verification_block_size);
+
+        // Clear the padding.
+        std::memset(static_cast<u8*>(buffer) + padding_offset, 0, padding_size);
+
+        // Set the new in-bounds size.
+        read_size = static_cast<size_t>(data_size - offset);
+    }
+
+    // Perform the read.
+    return m_data_storage->Read(buffer, read_size, offset);
+}
+
+size_t IntegrityVerificationStorage::GetSize() const {
+    return m_data_storage->GetSize();
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_integrity_verification_storage.h

@@ -0,0 +1,65 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <optional>
+
+#include "core/file_sys/fssystem/fs_i_storage.h"
+#include "core/file_sys/fssystem/fs_types.h"
+
+namespace FileSys {
+
+class IntegrityVerificationStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(IntegrityVerificationStorage);
+    YUZU_NON_MOVEABLE(IntegrityVerificationStorage);
+
+public:
+    static constexpr s64 HashSize = 256 / 8;
+
+    struct BlockHash {
+        std::array<u8, HashSize> hash;
+    };
+    static_assert(std::is_trivial_v<BlockHash>);
+
+public:
+    IntegrityVerificationStorage()
+        : m_verification_block_size(0), m_verification_block_order(0),
+          m_upper_layer_verification_block_size(0), m_upper_layer_verification_block_order(0) {}
+    virtual ~IntegrityVerificationStorage() override {
+        this->Finalize();
+    }
+
+    void Initialize(VirtualFile hs, VirtualFile ds, s64 verif_block_size,
+                    s64 upper_layer_verif_block_size, bool is_real_data);
+    void Finalize();
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+    virtual size_t GetSize() const override;
+
+    s64 GetBlockSize() const {
+        return m_verification_block_size;
+    }
+
+private:
+    static void SetValidationBit(BlockHash* hash) {
+        ASSERT(hash != nullptr);
+        hash->hash[HashSize - 1] |= 0x80;
+    }
+
+    static bool IsValidationBit(const BlockHash* hash) {
+        ASSERT(hash != nullptr);
+        return (hash->hash[HashSize - 1] & 0x80) != 0;
+    }
+
+private:
+    VirtualFile m_hash_storage;
+    VirtualFile m_data_storage;
+    s64 m_verification_block_size;
+    s64 m_verification_block_order;
+    s64 m_upper_layer_verification_block_size;
+    s64 m_upper_layer_verification_block_order;
+    bool m_is_real_data;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_memory_resource_buffer_hold_storage.h

@@ -0,0 +1,61 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fs_i_storage.h"
+
+namespace FileSys {
+
+class MemoryResourceBufferHoldStorage : public IStorage {
+    YUZU_NON_COPYABLE(MemoryResourceBufferHoldStorage);
+    YUZU_NON_MOVEABLE(MemoryResourceBufferHoldStorage);
+
+public:
+    MemoryResourceBufferHoldStorage(VirtualFile storage, size_t buffer_size)
+        : m_storage(std::move(storage)), m_buffer(::operator new(buffer_size)),
+          m_buffer_size(buffer_size) {}
+
+    virtual ~MemoryResourceBufferHoldStorage() {
+        // If we have a buffer, deallocate it.
+        if (m_buffer != nullptr) {
+            ::operator delete(m_buffer);
+        }
+    }
+
+    bool IsValid() const {
+        return m_buffer != nullptr;
+    }
+    void* GetBuffer() const {
+        return m_buffer;
+    }
+
+public:
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+        // Check pre-conditions.
+        ASSERT(m_storage != nullptr);
+
+        return m_storage->Read(buffer, size, offset);
+    }
+
+    virtual size_t GetSize() const override {
+        // Check pre-conditions.
+        ASSERT(m_storage != nullptr);
+
+        return m_storage->GetSize();
+    }
+
+    virtual size_t Write(const u8* buffer, size_t size, size_t offset) override {
+        // Check pre-conditions.
+        ASSERT(m_storage != nullptr);
+
+        return m_storage->Write(buffer, size, offset);
+    }
+
+private:
+    VirtualFile m_storage;
+    void* m_buffer;
+    size_t m_buffer_size;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_nca_file_system_driver.h

@@ -0,0 +1,364 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fssystem_compression_common.h"
+#include "core/file_sys/fssystem/fssystem_nca_header.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+
+class CompressedStorage;
+class AesCtrCounterExtendedStorage;
+class IndirectStorage;
+class SparseStorage;
+
+struct NcaCryptoConfiguration;
+
+using KeyGenerationFunction = void (*)(void* dst_key, size_t dst_key_size, const void* src_key,
+                                       size_t src_key_size, s32 key_type);
+using VerifySign1Function = bool (*)(const void* sig, size_t sig_size, const void* data,
+                                     size_t data_size, u8 generation);
+
+struct NcaCryptoConfiguration {
+    static constexpr size_t Rsa2048KeyModulusSize = 2048 / 8;
+    static constexpr size_t Rsa2048KeyPublicExponentSize = 3;
+    static constexpr size_t Rsa2048KeyPrivateExponentSize = Rsa2048KeyModulusSize;
+
+    static constexpr size_t Aes128KeySize = 128 / 8;
+
+    static constexpr size_t Header1SignatureKeyGenerationMax = 1;
+
+    static constexpr s32 KeyAreaEncryptionKeyIndexCount = 3;
+    static constexpr s32 HeaderEncryptionKeyCount = 2;
+
+    static constexpr u8 KeyAreaEncryptionKeyIndexZeroKey = 0xFF;
+
+    static constexpr size_t KeyGenerationMax = 32;
+
+    std::array<const u8*, Header1SignatureKeyGenerationMax + 1> header_1_sign_key_moduli;
+    std::array<u8, Rsa2048KeyPublicExponentSize> header_1_sign_key_public_exponent;
+    std::array<std::array<u8, Aes128KeySize>, KeyAreaEncryptionKeyIndexCount>
+        key_area_encryption_key_source;
+    std::array<u8, Aes128KeySize> header_encryption_key_source;
+    std::array<std::array<u8, Aes128KeySize>, HeaderEncryptionKeyCount>
+        header_encrypted_encryption_keys;
+    KeyGenerationFunction generate_key;
+    VerifySign1Function verify_sign1;
+    bool is_plaintext_header_available;
+    bool is_available_sw_key;
+};
+static_assert(std::is_trivial_v<NcaCryptoConfiguration>);
+
+struct NcaCompressionConfiguration {
+    GetDecompressorFunction get_decompressor;
+};
+static_assert(std::is_trivial_v<NcaCompressionConfiguration>);
+
+constexpr inline s32 KeyAreaEncryptionKeyCount =
+    NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexCount *
+    NcaCryptoConfiguration::KeyGenerationMax;
+
+enum class KeyType : s32 {
+    ZeroKey = -2,
+    InvalidKey = -1,
+    NcaHeaderKey1 = KeyAreaEncryptionKeyCount + 0,
+    NcaHeaderKey2 = KeyAreaEncryptionKeyCount + 1,
+    NcaExternalKey = KeyAreaEncryptionKeyCount + 2,
+    SaveDataDeviceUniqueMac = KeyAreaEncryptionKeyCount + 3,
+    SaveDataSeedUniqueMac = KeyAreaEncryptionKeyCount + 4,
+    SaveDataTransferMac = KeyAreaEncryptionKeyCount + 5,
+};
+
+constexpr inline bool IsInvalidKeyTypeValue(s32 key_type) {
+    return key_type < 0;
+}
+
+constexpr inline s32 GetKeyTypeValue(u8 key_index, u8 key_generation) {
+    if (key_index == NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexZeroKey) {
+        return static_cast<s32>(KeyType::ZeroKey);
+    }
+
+    if (key_index >= NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexCount) {
+        return static_cast<s32>(KeyType::InvalidKey);
+    }
+
+    return NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexCount * key_generation + key_index;
+}
+
+class NcaReader {
+    YUZU_NON_COPYABLE(NcaReader);
+    YUZU_NON_MOVEABLE(NcaReader);
+
+public:
+    NcaReader();
+    ~NcaReader();
+
+    Result Initialize(VirtualFile base_storage, const NcaCryptoConfiguration& crypto_cfg,
+                      const NcaCompressionConfiguration& compression_cfg);
+
+    VirtualFile GetSharedBodyStorage();
+    u32 GetMagic() const;
+    NcaHeader::DistributionType GetDistributionType() const;
+    NcaHeader::ContentType GetContentType() const;
+    u8 GetHeaderSign1KeyGeneration() const;
+    u8 GetKeyGeneration() const;
+    u8 GetKeyIndex() const;
+    u64 GetContentSize() const;
+    u64 GetProgramId() const;
+    u32 GetContentIndex() const;
+    u32 GetSdkAddonVersion() const;
+    void GetRightsId(u8* dst, size_t dst_size) const;
+    bool HasFsInfo(s32 index) const;
+    s32 GetFsCount() const;
+    const Hash& GetFsHeaderHash(s32 index) const;
+    void GetFsHeaderHash(Hash* dst, s32 index) const;
+    void GetFsInfo(NcaHeader::FsInfo* dst, s32 index) const;
+    u64 GetFsOffset(s32 index) const;
+    u64 GetFsEndOffset(s32 index) const;
+    u64 GetFsSize(s32 index) const;
+    void GetEncryptedKey(void* dst, size_t size) const;
+    const void* GetDecryptionKey(s32 index) const;
+    bool HasValidInternalKey() const;
+    bool HasInternalDecryptionKeyForAesHw() const;
+    bool IsSoftwareAesPrioritized() const;
+    void PrioritizeSoftwareAes();
+    bool IsAvailableSwKey() const;
+    bool HasExternalDecryptionKey() const;
+    const void* GetExternalDecryptionKey() const;
+    void SetExternalDecryptionKey(const void* src, size_t size);
+    void GetRawData(void* dst, size_t dst_size) const;
+    NcaHeader::EncryptionType GetEncryptionType() const;
+    Result ReadHeader(NcaFsHeader* dst, s32 index) const;
+
+    GetDecompressorFunction GetDecompressor() const;
+
+    bool GetHeaderSign1Valid() const;
+
+    void GetHeaderSign2(void* dst, size_t size) const;
+
+private:
+    NcaHeader m_header;
+    std::array<std::array<u8, NcaCryptoConfiguration::Aes128KeySize>,
+               NcaHeader::DecryptionKey_Count>
+        m_decryption_keys;
+    VirtualFile m_body_storage;
+    VirtualFile m_header_storage;
+    std::array<u8, NcaCryptoConfiguration::Aes128KeySize> m_external_decryption_key;
+    bool m_is_software_aes_prioritized;
+    bool m_is_available_sw_key;
+    NcaHeader::EncryptionType m_header_encryption_type;
+    bool m_is_header_sign1_signature_valid;
+    GetDecompressorFunction m_get_decompressor;
+};
+
+class NcaFsHeaderReader {
+    YUZU_NON_COPYABLE(NcaFsHeaderReader);
+    YUZU_NON_MOVEABLE(NcaFsHeaderReader);
+
+public:
+    NcaFsHeaderReader() : m_fs_index(-1) {
+        std::memset(std::addressof(m_data), 0, sizeof(m_data));
+    }
+
+    Result Initialize(const NcaReader& reader, s32 index);
+    bool IsInitialized() const {
+        return m_fs_index >= 0;
+    }
+
+    void GetRawData(void* dst, size_t dst_size) const;
+
+    NcaFsHeader::HashData& GetHashData();
+    const NcaFsHeader::HashData& GetHashData() const;
+    u16 GetVersion() const;
+    s32 GetFsIndex() const;
+    NcaFsHeader::FsType GetFsType() const;
+    NcaFsHeader::HashType GetHashType() const;
+    NcaFsHeader::EncryptionType GetEncryptionType() const;
+    NcaPatchInfo& GetPatchInfo();
+    const NcaPatchInfo& GetPatchInfo() const;
+    const NcaAesCtrUpperIv GetAesCtrUpperIv() const;
+
+    bool IsSkipLayerHashEncryption() const;
+    Result GetHashTargetOffset(s64* out) const;
+
+    bool ExistsSparseLayer() const;
+    NcaSparseInfo& GetSparseInfo();
+    const NcaSparseInfo& GetSparseInfo() const;
+
+    bool ExistsCompressionLayer() const;
+    NcaCompressionInfo& GetCompressionInfo();
+    const NcaCompressionInfo& GetCompressionInfo() const;
+
+    bool ExistsPatchMetaHashLayer() const;
+    NcaMetaDataHashDataInfo& GetPatchMetaDataHashDataInfo();
+    const NcaMetaDataHashDataInfo& GetPatchMetaDataHashDataInfo() const;
+    NcaFsHeader::MetaDataHashType GetPatchMetaHashType() const;
+
+    bool ExistsSparseMetaHashLayer() const;
+    NcaMetaDataHashDataInfo& GetSparseMetaDataHashDataInfo();
+    const NcaMetaDataHashDataInfo& GetSparseMetaDataHashDataInfo() const;
+    NcaFsHeader::MetaDataHashType GetSparseMetaHashType() const;
+
+private:
+    NcaFsHeader m_data;
+    s32 m_fs_index;
+};
+
+class NcaFileSystemDriver {
+    YUZU_NON_COPYABLE(NcaFileSystemDriver);
+    YUZU_NON_MOVEABLE(NcaFileSystemDriver);
+
+public:
+    struct StorageContext {
+        bool open_raw_storage;
+        VirtualFile body_substorage;
+        std::shared_ptr<SparseStorage> current_sparse_storage;
+        VirtualFile sparse_storage_meta_storage;
+        std::shared_ptr<SparseStorage> original_sparse_storage;
+        void* external_current_sparse_storage;
+        void* external_original_sparse_storage;
+        VirtualFile aes_ctr_ex_storage_meta_storage;
+        VirtualFile aes_ctr_ex_storage_data_storage;
+        std::shared_ptr<AesCtrCounterExtendedStorage> aes_ctr_ex_storage;
+        VirtualFile indirect_storage_meta_storage;
+        std::shared_ptr<IndirectStorage> indirect_storage;
+        VirtualFile fs_data_storage;
+        VirtualFile compressed_storage_meta_storage;
+        std::shared_ptr<CompressedStorage> compressed_storage;
+
+        VirtualFile patch_layer_info_storage;
+        VirtualFile sparse_layer_info_storage;
+
+        VirtualFile external_original_storage;
+    };
+
+private:
+    enum class AlignmentStorageRequirement {
+        CacheBlockSize = 0,
+        None = 1,
+    };
+
+public:
+    static Result SetupFsHeaderReader(NcaFsHeaderReader* out, const NcaReader& reader,
+                                      s32 fs_index);
+
+public:
+    NcaFileSystemDriver(std::shared_ptr<NcaReader> reader) : m_original_reader(), m_reader(reader) {
+        ASSERT(m_reader != nullptr);
+    }
+
+    NcaFileSystemDriver(std::shared_ptr<NcaReader> original_reader,
+                        std::shared_ptr<NcaReader> reader)
+        : m_original_reader(original_reader), m_reader(reader) {
+        ASSERT(m_reader != nullptr);
+    }
+
+    Result OpenStorageWithContext(VirtualFile* out, NcaFsHeaderReader* out_header_reader,
+                                  s32 fs_index, StorageContext* ctx);
+
+    Result OpenStorage(VirtualFile* out, NcaFsHeaderReader* out_header_reader, s32 fs_index) {
+        // Create a storage context.
+        StorageContext ctx{};
+
+        // Open the storage.
+        R_RETURN(OpenStorageWithContext(out, out_header_reader, fs_index, std::addressof(ctx)));
+    }
+
+public:
+    Result CreateStorageByRawStorage(VirtualFile* out, const NcaFsHeaderReader* header_reader,
+                                     VirtualFile raw_storage, StorageContext* ctx);
+
+private:
+    Result OpenStorageImpl(VirtualFile* out, NcaFsHeaderReader* out_header_reader, s32 fs_index,
+                           StorageContext* ctx);
+
+    Result OpenIndirectableStorageAsOriginal(VirtualFile* out,
+                                             const NcaFsHeaderReader* header_reader,
+                                             StorageContext* ctx);
+
+    Result CreateBodySubStorage(VirtualFile* out, s64 offset, s64 size);
+
+    Result CreateAesCtrStorage(VirtualFile* out, VirtualFile base_storage, s64 offset,
+                               const NcaAesCtrUpperIv& upper_iv,
+                               AlignmentStorageRequirement alignment_storage_requirement);
+    Result CreateAesXtsStorage(VirtualFile* out, VirtualFile base_storage, s64 offset);
+
+    Result CreateSparseStorageMetaStorage(VirtualFile* out, VirtualFile base_storage, s64 offset,
+                                          const NcaAesCtrUpperIv& upper_iv,
+                                          const NcaSparseInfo& sparse_info);
+    Result CreateSparseStorageCore(std::shared_ptr<SparseStorage>* out, VirtualFile base_storage,
+                                   s64 base_size, VirtualFile meta_storage,
+                                   const NcaSparseInfo& sparse_info, bool external_info);
+    Result CreateSparseStorage(VirtualFile* out, s64* out_fs_data_offset,
+                               std::shared_ptr<SparseStorage>* out_sparse_storage,
+                               VirtualFile* out_meta_storage, s32 index,
+                               const NcaAesCtrUpperIv& upper_iv, const NcaSparseInfo& sparse_info);
+
+    Result CreateSparseStorageMetaStorageWithVerification(
+        VirtualFile* out, VirtualFile* out_verification, VirtualFile base_storage, s64 offset,
+        const NcaAesCtrUpperIv& upper_iv, const NcaSparseInfo& sparse_info,
+        const NcaMetaDataHashDataInfo& meta_data_hash_data_info);
+    Result CreateSparseStorageWithVerification(
+        VirtualFile* out, s64* out_fs_data_offset,
+        std::shared_ptr<SparseStorage>* out_sparse_storage, VirtualFile* out_meta_storage,
+        VirtualFile* out_verification, s32 index, const NcaAesCtrUpperIv& upper_iv,
+        const NcaSparseInfo& sparse_info, const NcaMetaDataHashDataInfo& meta_data_hash_data_info,
+        NcaFsHeader::MetaDataHashType meta_data_hash_type);
+
+    Result CreateAesCtrExStorageMetaStorage(VirtualFile* out, VirtualFile base_storage, s64 offset,
+                                            NcaFsHeader::EncryptionType encryption_type,
+                                            const NcaAesCtrUpperIv& upper_iv,
+                                            const NcaPatchInfo& patch_info);
+    Result CreateAesCtrExStorage(VirtualFile* out,
+                                 std::shared_ptr<AesCtrCounterExtendedStorage>* out_ext,
+                                 VirtualFile base_storage, VirtualFile meta_storage,
+                                 s64 counter_offset, const NcaAesCtrUpperIv& upper_iv,
+                                 const NcaPatchInfo& patch_info);
+
+    Result CreateIndirectStorageMetaStorage(VirtualFile* out, VirtualFile base_storage,
+                                            const NcaPatchInfo& patch_info);
+    Result CreateIndirectStorage(VirtualFile* out, std::shared_ptr<IndirectStorage>* out_ind,
+                                 VirtualFile base_storage, VirtualFile original_data_storage,
+                                 VirtualFile meta_storage, const NcaPatchInfo& patch_info);
+
+    Result CreatePatchMetaStorage(VirtualFile* out_aes_ctr_ex_meta, VirtualFile* out_indirect_meta,
+                                  VirtualFile* out_verification, VirtualFile base_storage,
+                                  s64 offset, const NcaAesCtrUpperIv& upper_iv,
+                                  const NcaPatchInfo& patch_info,
+                                  const NcaMetaDataHashDataInfo& meta_data_hash_data_info);
+
+    Result CreateSha256Storage(VirtualFile* out, VirtualFile base_storage,
+                               const NcaFsHeader::HashData::HierarchicalSha256Data& sha256_data);
+
+    Result CreateIntegrityVerificationStorage(
+        VirtualFile* out, VirtualFile base_storage,
+        const NcaFsHeader::HashData::IntegrityMetaInfo& meta_info);
+    Result CreateIntegrityVerificationStorageForMeta(
+        VirtualFile* out, VirtualFile* out_verification, VirtualFile base_storage, s64 offset,
+        const NcaMetaDataHashDataInfo& meta_data_hash_data_info);
+    Result CreateIntegrityVerificationStorageImpl(
+        VirtualFile* out, VirtualFile base_storage,
+        const NcaFsHeader::HashData::IntegrityMetaInfo& meta_info, s64 layer_info_offset,
+        int max_data_cache_entries, int max_hash_cache_entries, s8 buffer_level);
+
+    Result CreateRegionSwitchStorage(VirtualFile* out, const NcaFsHeaderReader* header_reader,
+                                     VirtualFile inside_storage, VirtualFile outside_storage);
+
+    Result CreateCompressedStorage(VirtualFile* out, std::shared_ptr<CompressedStorage>* out_cmp,
+                                   VirtualFile* out_meta, VirtualFile base_storage,
+                                   const NcaCompressionInfo& compression_info);
+
+public:
+    Result CreateCompressedStorage(VirtualFile* out, std::shared_ptr<CompressedStorage>* out_cmp,
+                                   VirtualFile* out_meta, VirtualFile base_storage,
+                                   const NcaCompressionInfo& compression_info,
+                                   GetDecompressorFunction get_decompressor);
+
+private:
+    std::shared_ptr<NcaReader> m_original_reader;
+    std::shared_ptr<NcaReader> m_reader;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_nca_header.cpp

@@ -0,0 +1,20 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/fssystem/fssystem_nca_header.h"
+
+namespace FileSys {
+
+u8 NcaHeader::GetProperKeyGeneration() const {
+    return std::max(this->key_generation, this->key_generation_2);
+}
+
+bool NcaPatchInfo::HasIndirectTable() const {
+    return this->indirect_size != 0;
+}
+
+bool NcaPatchInfo::HasAesCtrExTable() const {
+    return this->aes_ctr_ex_size != 0;
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_nca_header.h

@@ -0,0 +1,338 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+#include "common/literals.h"
+
+#include "core/file_sys/errors.h"
+#include "core/file_sys/fssystem/fs_types.h"
+
+namespace FileSys {
+
+using namespace Common::Literals;
+
+struct Hash {
+    static constexpr std::size_t Size = 256 / 8;
+    std::array<u8, Size> value;
+};
+static_assert(sizeof(Hash) == Hash::Size);
+static_assert(std::is_trivial_v<Hash>);
+
+using NcaDigest = Hash;
+
+struct NcaHeader {
+    enum class ContentType : u8 {
+        Program = 0,
+        Meta = 1,
+        Control = 2,
+        Manual = 3,
+        Data = 4,
+        PublicData = 5,
+
+        Start = Program,
+        End = PublicData,
+    };
+
+    enum class DistributionType : u8 {
+        Download = 0,
+        GameCard = 1,
+
+        Start = Download,
+        End = GameCard,
+    };
+
+    enum class EncryptionType : u8 {
+        Auto = 0,
+        None = 1,
+    };
+
+    enum DecryptionKey {
+        DecryptionKey_AesXts = 0,
+        DecryptionKey_AesXts1 = DecryptionKey_AesXts,
+        DecryptionKey_AesXts2 = 1,
+        DecryptionKey_AesCtr = 2,
+        DecryptionKey_AesCtrEx = 3,
+        DecryptionKey_AesCtrHw = 4,
+        DecryptionKey_Count,
+    };
+
+    struct FsInfo {
+        u32 start_sector;
+        u32 end_sector;
+        u32 hash_sectors;
+        u32 reserved;
+    };
+    static_assert(sizeof(FsInfo) == 0x10);
+    static_assert(std::is_trivial_v<FsInfo>);
+
+    static constexpr u32 Magic0 = Common::MakeMagic('N', 'C', 'A', '0');
+    static constexpr u32 Magic1 = Common::MakeMagic('N', 'C', 'A', '1');
+    static constexpr u32 Magic2 = Common::MakeMagic('N', 'C', 'A', '2');
+    static constexpr u32 Magic3 = Common::MakeMagic('N', 'C', 'A', '3');
+
+    static constexpr u32 Magic = Magic3;
+
+    static constexpr std::size_t Size = 1_KiB;
+    static constexpr s32 FsCountMax = 4;
+    static constexpr std::size_t HeaderSignCount = 2;
+    static constexpr std::size_t HeaderSignSize = 0x100;
+    static constexpr std::size_t EncryptedKeyAreaSize = 0x100;
+    static constexpr std::size_t SectorSize = 0x200;
+    static constexpr std::size_t SectorShift = 9;
+    static constexpr std::size_t RightsIdSize = 0x10;
+    static constexpr std::size_t XtsBlockSize = 0x200;
+    static constexpr std::size_t CtrBlockSize = 0x10;
+
+    static_assert(SectorSize == (1 << SectorShift));
+
+    // Data members.
+    std::array<u8, HeaderSignSize> header_sign_1;
+    std::array<u8, HeaderSignSize> header_sign_2;
+    u32 magic;
+    DistributionType distribution_type;
+    ContentType content_type;
+    u8 key_generation;
+    u8 key_index;
+    u64 content_size;
+    u64 program_id;
+    u32 content_index;
+    u32 sdk_addon_version;
+    u8 key_generation_2;
+    u8 header1_signature_key_generation;
+    std::array<u8, 2> reserved_222;
+    std::array<u32, 3> reserved_224;
+    std::array<u8, RightsIdSize> rights_id;
+    std::array<FsInfo, FsCountMax> fs_info;
+    std::array<Hash, FsCountMax> fs_header_hash;
+    std::array<u8, EncryptedKeyAreaSize> encrypted_key_area;
+
+    static constexpr u64 SectorToByte(u32 sector) {
+        return static_cast<u64>(sector) << SectorShift;
+    }
+
+    static constexpr u32 ByteToSector(u64 byte) {
+        return static_cast<u32>(byte >> SectorShift);
+    }
+
+    u8 GetProperKeyGeneration() const;
+};
+static_assert(sizeof(NcaHeader) == NcaHeader::Size);
+static_assert(std::is_trivial_v<NcaHeader>);
+
+struct NcaBucketInfo {
+    static constexpr size_t HeaderSize = 0x10;
+    Int64 offset;
+    Int64 size;
+    std::array<u8, HeaderSize> header;
+};
+static_assert(std::is_trivial_v<NcaBucketInfo>);
+
+struct NcaPatchInfo {
+    static constexpr size_t Size = 0x40;
+    static constexpr size_t Offset = 0x100;
+
+    Int64 indirect_offset;
+    Int64 indirect_size;
+    std::array<u8, NcaBucketInfo::HeaderSize> indirect_header;
+    Int64 aes_ctr_ex_offset;
+    Int64 aes_ctr_ex_size;
+    std::array<u8, NcaBucketInfo::HeaderSize> aes_ctr_ex_header;
+
+    bool HasIndirectTable() const;
+    bool HasAesCtrExTable() const;
+};
+static_assert(std::is_trivial_v<NcaPatchInfo>);
+
+union NcaAesCtrUpperIv {
+    u64 value;
+    struct {
+        u32 generation;
+        u32 secure_value;
+    } part;
+};
+static_assert(std::is_trivial_v<NcaAesCtrUpperIv>);
+
+struct NcaSparseInfo {
+    NcaBucketInfo bucket;
+    Int64 physical_offset;
+    u16 generation;
+    std::array<u8, 6> reserved;
+
+    s64 GetPhysicalSize() const {
+        return this->bucket.offset + this->bucket.size;
+    }
+
+    u32 GetGeneration() const {
+        return static_cast<u32>(this->generation) << 16;
+    }
+
+    const NcaAesCtrUpperIv MakeAesCtrUpperIv(NcaAesCtrUpperIv upper_iv) const {
+        NcaAesCtrUpperIv sparse_upper_iv = upper_iv;
+        sparse_upper_iv.part.generation = this->GetGeneration();
+        return sparse_upper_iv;
+    }
+};
+static_assert(std::is_trivial_v<NcaSparseInfo>);
+
+struct NcaCompressionInfo {
+    NcaBucketInfo bucket;
+    std::array<u8, 8> resreved;
+};
+static_assert(std::is_trivial_v<NcaCompressionInfo>);
+
+struct NcaMetaDataHashDataInfo {
+    Int64 offset;
+    Int64 size;
+    Hash hash;
+};
+static_assert(std::is_trivial_v<NcaMetaDataHashDataInfo>);
+
+struct NcaFsHeader {
+    static constexpr size_t Size = 0x200;
+    static constexpr size_t HashDataOffset = 0x8;
+
+    struct Region {
+        Int64 offset;
+        Int64 size;
+    };
+    static_assert(std::is_trivial_v<Region>);
+
+    enum class FsType : u8 {
+        RomFs = 0,
+        PartitionFs = 1,
+    };
+
+    enum class EncryptionType : u8 {
+        Auto = 0,
+        None = 1,
+        AesXts = 2,
+        AesCtr = 3,
+        AesCtrEx = 4,
+        AesCtrSkipLayerHash = 5,
+        AesCtrExSkipLayerHash = 6,
+    };
+
+    enum class HashType : u8 {
+        Auto = 0,
+        None = 1,
+        HierarchicalSha256Hash = 2,
+        HierarchicalIntegrityHash = 3,
+        AutoSha3 = 4,
+        HierarchicalSha3256Hash = 5,
+        HierarchicalIntegritySha3Hash = 6,
+    };
+
+    enum class MetaDataHashType : u8 {
+        None = 0,
+        HierarchicalIntegrity = 1,
+    };
+
+    union HashData {
+        struct HierarchicalSha256Data {
+            static constexpr size_t HashLayerCountMax = 5;
+            static const size_t MasterHashOffset;
+
+            Hash fs_data_master_hash;
+            s32 hash_block_size;
+            s32 hash_layer_count;
+            std::array<Region, HashLayerCountMax> hash_layer_region;
+        } hierarchical_sha256_data;
+        static_assert(std::is_trivial_v<HierarchicalSha256Data>);
+
+        struct IntegrityMetaInfo {
+            static const size_t MasterHashOffset;
+
+            u32 magic;
+            u32 version;
+            u32 master_hash_size;
+
+            struct LevelHashInfo {
+                u32 max_layers;
+
+                struct HierarchicalIntegrityVerificationLevelInformation {
+                    static constexpr size_t IntegrityMaxLayerCount = 7;
+                    Int64 offset;
+                    Int64 size;
+                    s32 block_order;
+                    std::array<u8, 4> reserved;
+                };
+                std::array<
+                    HierarchicalIntegrityVerificationLevelInformation,
+                    HierarchicalIntegrityVerificationLevelInformation::IntegrityMaxLayerCount - 1>
+                    info;
+
+                struct SignatureSalt {
+                    static constexpr size_t Size = 0x20;
+                    std::array<u8, Size> value;
+                };
+                SignatureSalt seed;
+            } level_hash_info;
+
+            Hash master_hash;
+        } integrity_meta_info;
+        static_assert(std::is_trivial_v<IntegrityMetaInfo>);
+
+        std::array<u8, NcaPatchInfo::Offset - HashDataOffset> padding;
+    };
+
+    u16 version;
+    FsType fs_type;
+    HashType hash_type;
+    EncryptionType encryption_type;
+    MetaDataHashType meta_data_hash_type;
+    std::array<u8, 2> reserved;
+    HashData hash_data;
+    NcaPatchInfo patch_info;
+    NcaAesCtrUpperIv aes_ctr_upper_iv;
+    NcaSparseInfo sparse_info;
+    NcaCompressionInfo compression_info;
+    NcaMetaDataHashDataInfo meta_data_hash_data_info;
+    std::array<u8, 0x30> pad;
+
+    bool IsSkipLayerHashEncryption() const {
+        return this->encryption_type == EncryptionType::AesCtrSkipLayerHash ||
+               this->encryption_type == EncryptionType::AesCtrExSkipLayerHash;
+    }
+
+    Result GetHashTargetOffset(s64* out) const {
+        switch (this->hash_type) {
+        case HashType::HierarchicalIntegrityHash:
+        case HashType::HierarchicalIntegritySha3Hash:
+            *out = this->hash_data.integrity_meta_info.level_hash_info
+                       .info[this->hash_data.integrity_meta_info.level_hash_info.max_layers - 2]
+                       .offset;
+            R_SUCCEED();
+        case HashType::HierarchicalSha256Hash:
+        case HashType::HierarchicalSha3256Hash:
+            *out =
+                this->hash_data.hierarchical_sha256_data
+                    .hash_layer_region[this->hash_data.hierarchical_sha256_data.hash_layer_count -
+                                       1]
+                    .offset;
+            R_SUCCEED();
+        default:
+            R_THROW(ResultInvalidNcaFsHeader);
+        }
+    }
+};
+static_assert(sizeof(NcaFsHeader) == NcaFsHeader::Size);
+static_assert(std::is_trivial_v<NcaFsHeader>);
+static_assert(offsetof(NcaFsHeader, patch_info) == NcaPatchInfo::Offset);
+
+inline constexpr const size_t NcaFsHeader::HashData::HierarchicalSha256Data::MasterHashOffset =
+    offsetof(NcaFsHeader, hash_data.hierarchical_sha256_data.fs_data_master_hash);
+inline constexpr const size_t NcaFsHeader::HashData::IntegrityMetaInfo::MasterHashOffset =
+    offsetof(NcaFsHeader, hash_data.integrity_meta_info.master_hash);
+
+struct NcaMetaDataHashData {
+    s64 layer_info_offset;
+    NcaFsHeader::HashData::IntegrityMetaInfo integrity_meta_info;
+};
+static_assert(sizeof(NcaMetaDataHashData) ==
+              sizeof(NcaFsHeader::HashData::IntegrityMetaInfo) + sizeof(s64));
+static_assert(std::is_trivial_v<NcaMetaDataHashData>);
+
+} // namespace FileSys

core/fs/fssystem/fssystem_nca_reader.cpp

@@ -0,0 +1,531 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/fssystem/fssystem_aes_xts_storage.h"
+#include "core/file_sys/fssystem/fssystem_nca_file_system_driver.h"
+#include "core/file_sys/vfs/vfs_offset.h"
+
+namespace FileSys {
+
+namespace {
+
+constexpr inline u32 SdkAddonVersionMin = 0x000B0000;
+constexpr inline size_t Aes128KeySize = 0x10;
+constexpr const std::array<u8, Aes128KeySize> ZeroKey{};
+
+constexpr Result CheckNcaMagic(u32 magic) {
+    // Verify the magic is not a deprecated one.
+    R_UNLESS(magic != NcaHeader::Magic0, ResultUnsupportedSdkVersion);
+    R_UNLESS(magic != NcaHeader::Magic1, ResultUnsupportedSdkVersion);
+    R_UNLESS(magic != NcaHeader::Magic2, ResultUnsupportedSdkVersion);
+
+    // Verify the magic is the current one.
+    R_UNLESS(magic == NcaHeader::Magic3, ResultInvalidNcaSignature);
+
+    R_SUCCEED();
+}
+
+} // namespace
+
+NcaReader::NcaReader()
+    : m_body_storage(), m_header_storage(), m_is_software_aes_prioritized(false),
+      m_is_available_sw_key(false), m_header_encryption_type(NcaHeader::EncryptionType::Auto),
+      m_get_decompressor() {
+    std::memset(std::addressof(m_header), 0, sizeof(m_header));
+    std::memset(std::addressof(m_decryption_keys), 0, sizeof(m_decryption_keys));
+    std::memset(std::addressof(m_external_decryption_key), 0, sizeof(m_external_decryption_key));
+}
+
+NcaReader::~NcaReader() {}
+
+Result NcaReader::Initialize(VirtualFile base_storage, const NcaCryptoConfiguration& crypto_cfg,
+                             const NcaCompressionConfiguration& compression_cfg) {
+    // Validate preconditions.
+    ASSERT(base_storage != nullptr);
+    ASSERT(m_body_storage == nullptr);
+
+    // Create the work header storage storage.
+    VirtualFile work_header_storage;
+
+    // We need to be able to generate keys.
+    R_UNLESS(crypto_cfg.generate_key != nullptr, ResultInvalidArgument);
+
+    // Generate keys for header.
+    using AesXtsStorageForNcaHeader = AesXtsStorage;
+
+    constexpr std::array<s32, NcaCryptoConfiguration::HeaderEncryptionKeyCount>
+        HeaderKeyTypeValues = {
+            static_cast<s32>(KeyType::NcaHeaderKey1),
+            static_cast<s32>(KeyType::NcaHeaderKey2),
+        };
+
+    std::array<std::array<u8, NcaCryptoConfiguration::Aes128KeySize>,
+               NcaCryptoConfiguration::HeaderEncryptionKeyCount>
+        header_decryption_keys;
+    for (size_t i = 0; i < NcaCryptoConfiguration::HeaderEncryptionKeyCount; i++) {
+        crypto_cfg.generate_key(header_decryption_keys[i].data(),
+                                AesXtsStorageForNcaHeader::KeySize,
+                                crypto_cfg.header_encrypted_encryption_keys[i].data(),
+                                AesXtsStorageForNcaHeader::KeySize, HeaderKeyTypeValues[i]);
+    }
+
+    // Create the header storage.
+    std::array<u8, AesXtsStorageForNcaHeader::IvSize> header_iv = {};
+    work_header_storage = std::make_unique<AesXtsStorageForNcaHeader>(
+        base_storage, header_decryption_keys[0].data(), header_decryption_keys[1].data(),
+        AesXtsStorageForNcaHeader::KeySize, header_iv.data(), AesXtsStorageForNcaHeader::IvSize,
+        NcaHeader::XtsBlockSize);
+
+    // Check that we successfully created the storage.
+    R_UNLESS(work_header_storage != nullptr, ResultAllocationMemoryFailedInNcaReaderA);
+
+    // Read the header.
+    work_header_storage->ReadObject(std::addressof(m_header), 0);
+
+    // Validate the magic.
+    if (const Result magic_result = CheckNcaMagic(m_header.magic); R_FAILED(magic_result)) {
+        // Try to use a plaintext header.
+        base_storage->ReadObject(std::addressof(m_header), 0);
+        R_UNLESS(R_SUCCEEDED(CheckNcaMagic(m_header.magic)), magic_result);
+
+        // Configure to use the plaintext header.
+        auto base_storage_size = base_storage->GetSize();
+        work_header_storage = std::make_shared<OffsetVfsFile>(base_storage, base_storage_size, 0);
+        R_UNLESS(work_header_storage != nullptr, ResultAllocationMemoryFailedInNcaReaderA);
+
+        // Set encryption type as plaintext.
+        m_header_encryption_type = NcaHeader::EncryptionType::None;
+    }
+
+    // Verify the header sign1.
+    if (crypto_cfg.verify_sign1 != nullptr) {
+        const u8* sig = m_header.header_sign_1.data();
+        const size_t sig_size = NcaHeader::HeaderSignSize;
+        const u8* msg =
+            static_cast<const u8*>(static_cast<const void*>(std::addressof(m_header.magic)));
+        const size_t msg_size =
+            NcaHeader::Size - NcaHeader::HeaderSignSize * NcaHeader::HeaderSignCount;
+
+        m_is_header_sign1_signature_valid = crypto_cfg.verify_sign1(
+            sig, sig_size, msg, msg_size, m_header.header1_signature_key_generation);
+
+        if (!m_is_header_sign1_signature_valid) {
+            LOG_WARNING(Common_Filesystem, "Invalid NCA header sign1");
+        }
+    }
+
+    // Validate the sdk version.
+    R_UNLESS(m_header.sdk_addon_version >= SdkAddonVersionMin, ResultUnsupportedSdkVersion);
+
+    // Validate the key index.
+    R_UNLESS(m_header.key_index < NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexCount ||
+                 m_header.key_index == NcaCryptoConfiguration::KeyAreaEncryptionKeyIndexZeroKey,
+             ResultInvalidNcaKeyIndex);
+
+    // Check if we have a rights id.
+    constexpr const std::array<u8, NcaHeader::RightsIdSize> ZeroRightsId{};
+    if (std::memcmp(ZeroRightsId.data(), m_header.rights_id.data(), NcaHeader::RightsIdSize) == 0) {
+        // If we don't, then we don't have an external key, so we need to generate decryption keys.
+        crypto_cfg.generate_key(
+            m_decryption_keys[NcaHeader::DecryptionKey_AesCtr].data(), Aes128KeySize,
+            m_header.encrypted_key_area.data() + NcaHeader::DecryptionKey_AesCtr * Aes128KeySize,
+            Aes128KeySize, GetKeyTypeValue(m_header.key_index, m_header.GetProperKeyGeneration()));
+        crypto_cfg.generate_key(
+            m_decryption_keys[NcaHeader::DecryptionKey_AesXts1].data(), Aes128KeySize,
+            m_header.encrypted_key_area.data() + NcaHeader::DecryptionKey_AesXts1 * Aes128KeySize,
+            Aes128KeySize, GetKeyTypeValue(m_header.key_index, m_header.GetProperKeyGeneration()));
+        crypto_cfg.generate_key(
+            m_decryption_keys[NcaHeader::DecryptionKey_AesXts2].data(), Aes128KeySize,
+            m_header.encrypted_key_area.data() + NcaHeader::DecryptionKey_AesXts2 * Aes128KeySize,
+            Aes128KeySize, GetKeyTypeValue(m_header.key_index, m_header.GetProperKeyGeneration()));
+        crypto_cfg.generate_key(
+            m_decryption_keys[NcaHeader::DecryptionKey_AesCtrEx].data(), Aes128KeySize,
+            m_header.encrypted_key_area.data() + NcaHeader::DecryptionKey_AesCtrEx * Aes128KeySize,
+            Aes128KeySize, GetKeyTypeValue(m_header.key_index, m_header.GetProperKeyGeneration()));
+
+        // Copy the hardware speed emulation key.
+        std::memcpy(m_decryption_keys[NcaHeader::DecryptionKey_AesCtrHw].data(),
+                    m_header.encrypted_key_area.data() +
+                        NcaHeader::DecryptionKey_AesCtrHw * Aes128KeySize,
+                    Aes128KeySize);
+    }
+
+    // Clear the external decryption key.
+    std::memset(m_external_decryption_key.data(), 0, m_external_decryption_key.size());
+
+    // Set software key availability.
+    m_is_available_sw_key = crypto_cfg.is_available_sw_key;
+
+    // Set our decompressor function getter.
+    m_get_decompressor = compression_cfg.get_decompressor;
+
+    // Set our storages.
+    m_header_storage = std::move(work_header_storage);
+    m_body_storage = std::move(base_storage);
+
+    R_SUCCEED();
+}
+
+VirtualFile NcaReader::GetSharedBodyStorage() {
+    ASSERT(m_body_storage != nullptr);
+    return m_body_storage;
+}
+
+u32 NcaReader::GetMagic() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.magic;
+}
+
+NcaHeader::DistributionType NcaReader::GetDistributionType() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.distribution_type;
+}
+
+NcaHeader::ContentType NcaReader::GetContentType() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.content_type;
+}
+
+u8 NcaReader::GetHeaderSign1KeyGeneration() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.header1_signature_key_generation;
+}
+
+u8 NcaReader::GetKeyGeneration() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.GetProperKeyGeneration();
+}
+
+u8 NcaReader::GetKeyIndex() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.key_index;
+}
+
+u64 NcaReader::GetContentSize() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.content_size;
+}
+
+u64 NcaReader::GetProgramId() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.program_id;
+}
+
+u32 NcaReader::GetContentIndex() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.content_index;
+}
+
+u32 NcaReader::GetSdkAddonVersion() const {
+    ASSERT(m_body_storage != nullptr);
+    return m_header.sdk_addon_version;
+}
+
+void NcaReader::GetRightsId(u8* dst, size_t dst_size) const {
+    ASSERT(dst != nullptr);
+    ASSERT(dst_size >= NcaHeader::RightsIdSize);
+
+    std::memcpy(dst, m_header.rights_id.data(), NcaHeader::RightsIdSize);
+}
+
+bool NcaReader::HasFsInfo(s32 index) const {
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    return m_header.fs_info[index].start_sector != 0 || m_header.fs_info[index].end_sector != 0;
+}
+
+s32 NcaReader::GetFsCount() const {
+    ASSERT(m_body_storage != nullptr);
+    for (s32 i = 0; i < NcaHeader::FsCountMax; i++) {
+        if (!this->HasFsInfo(i)) {
+            return i;
+        }
+    }
+    return NcaHeader::FsCountMax;
+}
+
+const Hash& NcaReader::GetFsHeaderHash(s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    return m_header.fs_header_hash[index];
+}
+
+void NcaReader::GetFsHeaderHash(Hash* dst, s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    ASSERT(dst != nullptr);
+    std::memcpy(dst, std::addressof(m_header.fs_header_hash[index]), sizeof(*dst));
+}
+
+void NcaReader::GetFsInfo(NcaHeader::FsInfo* dst, s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    ASSERT(dst != nullptr);
+    std::memcpy(dst, std::addressof(m_header.fs_info[index]), sizeof(*dst));
+}
+
+u64 NcaReader::GetFsOffset(s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    return NcaHeader::SectorToByte(m_header.fs_info[index].start_sector);
+}
+
+u64 NcaReader::GetFsEndOffset(s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    return NcaHeader::SectorToByte(m_header.fs_info[index].end_sector);
+}
+
+u64 NcaReader::GetFsSize(s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+    return NcaHeader::SectorToByte(m_header.fs_info[index].end_sector -
+                                   m_header.fs_info[index].start_sector);
+}
+
+void NcaReader::GetEncryptedKey(void* dst, size_t size) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(dst != nullptr);
+    ASSERT(size >= NcaHeader::EncryptedKeyAreaSize);
+
+    std::memcpy(dst, m_header.encrypted_key_area.data(), NcaHeader::EncryptedKeyAreaSize);
+}
+
+const void* NcaReader::GetDecryptionKey(s32 index) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::DecryptionKey_Count);
+    return m_decryption_keys[index].data();
+}
+
+bool NcaReader::HasValidInternalKey() const {
+    for (s32 i = 0; i < NcaHeader::DecryptionKey_Count; i++) {
+        if (std::memcmp(ZeroKey.data(), m_header.encrypted_key_area.data() + i * Aes128KeySize,
+                        Aes128KeySize) != 0) {
+            return true;
+        }
+    }
+    return false;
+}
+
+bool NcaReader::HasInternalDecryptionKeyForAesHw() const {
+    return std::memcmp(ZeroKey.data(), this->GetDecryptionKey(NcaHeader::DecryptionKey_AesCtrHw),
+                       Aes128KeySize) != 0;
+}
+
+bool NcaReader::IsSoftwareAesPrioritized() const {
+    return m_is_software_aes_prioritized;
+}
+
+void NcaReader::PrioritizeSoftwareAes() {
+    m_is_software_aes_prioritized = true;
+}
+
+bool NcaReader::IsAvailableSwKey() const {
+    return m_is_available_sw_key;
+}
+
+bool NcaReader::HasExternalDecryptionKey() const {
+    return std::memcmp(ZeroKey.data(), this->GetExternalDecryptionKey(), Aes128KeySize) != 0;
+}
+
+const void* NcaReader::GetExternalDecryptionKey() const {
+    return m_external_decryption_key.data();
+}
+
+void NcaReader::SetExternalDecryptionKey(const void* src, size_t size) {
+    ASSERT(src != nullptr);
+    ASSERT(size == sizeof(m_external_decryption_key));
+
+    std::memcpy(m_external_decryption_key.data(), src, sizeof(m_external_decryption_key));
+}
+
+void NcaReader::GetRawData(void* dst, size_t dst_size) const {
+    ASSERT(m_body_storage != nullptr);
+    ASSERT(dst != nullptr);
+    ASSERT(dst_size >= sizeof(NcaHeader));
+
+    std::memcpy(dst, std::addressof(m_header), sizeof(NcaHeader));
+}
+
+GetDecompressorFunction NcaReader::GetDecompressor() const {
+    ASSERT(m_get_decompressor != nullptr);
+    return m_get_decompressor;
+}
+
+NcaHeader::EncryptionType NcaReader::GetEncryptionType() const {
+    return m_header_encryption_type;
+}
+
+Result NcaReader::ReadHeader(NcaFsHeader* dst, s32 index) const {
+    ASSERT(dst != nullptr);
+    ASSERT(0 <= index && index < NcaHeader::FsCountMax);
+
+    const s64 offset = sizeof(NcaHeader) + sizeof(NcaFsHeader) * index;
+    m_header_storage->ReadObject(dst, offset);
+
+    R_SUCCEED();
+}
+
+bool NcaReader::GetHeaderSign1Valid() const {
+    return m_is_header_sign1_signature_valid;
+}
+
+void NcaReader::GetHeaderSign2(void* dst, size_t size) const {
+    ASSERT(dst != nullptr);
+    ASSERT(size == NcaHeader::HeaderSignSize);
+
+    std::memcpy(dst, m_header.header_sign_2.data(), size);
+}
+
+Result NcaFsHeaderReader::Initialize(const NcaReader& reader, s32 index) {
+    // Reset ourselves to uninitialized.
+    m_fs_index = -1;
+
+    // Read the header.
+    R_TRY(reader.ReadHeader(std::addressof(m_data), index));
+
+    // Set our index.
+    m_fs_index = index;
+    R_SUCCEED();
+}
+
+void NcaFsHeaderReader::GetRawData(void* dst, size_t dst_size) const {
+    ASSERT(this->IsInitialized());
+    ASSERT(dst != nullptr);
+    ASSERT(dst_size >= sizeof(NcaFsHeader));
+
+    std::memcpy(dst, std::addressof(m_data), sizeof(NcaFsHeader));
+}
+
+NcaFsHeader::HashData& NcaFsHeaderReader::GetHashData() {
+    ASSERT(this->IsInitialized());
+    return m_data.hash_data;
+}
+
+const NcaFsHeader::HashData& NcaFsHeaderReader::GetHashData() const {
+    ASSERT(this->IsInitialized());
+    return m_data.hash_data;
+}
+
+u16 NcaFsHeaderReader::GetVersion() const {
+    ASSERT(this->IsInitialized());
+    return m_data.version;
+}
+
+s32 NcaFsHeaderReader::GetFsIndex() const {
+    ASSERT(this->IsInitialized());
+    return m_fs_index;
+}
+
+NcaFsHeader::FsType NcaFsHeaderReader::GetFsType() const {
+    ASSERT(this->IsInitialized());
+    return m_data.fs_type;
+}
+
+NcaFsHeader::HashType NcaFsHeaderReader::GetHashType() const {
+    ASSERT(this->IsInitialized());
+    return m_data.hash_type;
+}
+
+NcaFsHeader::EncryptionType NcaFsHeaderReader::GetEncryptionType() const {
+    ASSERT(this->IsInitialized());
+    return m_data.encryption_type;
+}
+
+NcaPatchInfo& NcaFsHeaderReader::GetPatchInfo() {
+    ASSERT(this->IsInitialized());
+    return m_data.patch_info;
+}
+
+const NcaPatchInfo& NcaFsHeaderReader::GetPatchInfo() const {
+    ASSERT(this->IsInitialized());
+    return m_data.patch_info;
+}
+
+const NcaAesCtrUpperIv NcaFsHeaderReader::GetAesCtrUpperIv() const {
+    ASSERT(this->IsInitialized());
+    return m_data.aes_ctr_upper_iv;
+}
+
+bool NcaFsHeaderReader::IsSkipLayerHashEncryption() const {
+    ASSERT(this->IsInitialized());
+    return m_data.IsSkipLayerHashEncryption();
+}
+
+Result NcaFsHeaderReader::GetHashTargetOffset(s64* out) const {
+    ASSERT(out != nullptr);
+    ASSERT(this->IsInitialized());
+
+    R_RETURN(m_data.GetHashTargetOffset(out));
+}
+
+bool NcaFsHeaderReader::ExistsSparseLayer() const {
+    ASSERT(this->IsInitialized());
+    return m_data.sparse_info.generation != 0;
+}
+
+NcaSparseInfo& NcaFsHeaderReader::GetSparseInfo() {
+    ASSERT(this->IsInitialized());
+    return m_data.sparse_info;
+}
+
+const NcaSparseInfo& NcaFsHeaderReader::GetSparseInfo() const {
+    ASSERT(this->IsInitialized());
+    return m_data.sparse_info;
+}
+
+bool NcaFsHeaderReader::ExistsCompressionLayer() const {
+    ASSERT(this->IsInitialized());
+    return m_data.compression_info.bucket.offset != 0 && m_data.compression_info.bucket.size != 0;
+}
+
+NcaCompressionInfo& NcaFsHeaderReader::GetCompressionInfo() {
+    ASSERT(this->IsInitialized());
+    return m_data.compression_info;
+}
+
+const NcaCompressionInfo& NcaFsHeaderReader::GetCompressionInfo() const {
+    ASSERT(this->IsInitialized());
+    return m_data.compression_info;
+}
+
+bool NcaFsHeaderReader::ExistsPatchMetaHashLayer() const {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_data_info.size != 0 && this->GetPatchInfo().HasIndirectTable();
+}
+
+NcaMetaDataHashDataInfo& NcaFsHeaderReader::GetPatchMetaDataHashDataInfo() {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_data_info;
+}
+
+const NcaMetaDataHashDataInfo& NcaFsHeaderReader::GetPatchMetaDataHashDataInfo() const {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_data_info;
+}
+
+NcaFsHeader::MetaDataHashType NcaFsHeaderReader::GetPatchMetaHashType() const {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_type;
+}
+
+bool NcaFsHeaderReader::ExistsSparseMetaHashLayer() const {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_data_info.size != 0 && this->ExistsSparseLayer();
+}
+
+NcaMetaDataHashDataInfo& NcaFsHeaderReader::GetSparseMetaDataHashDataInfo() {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_data_info;
+}
+
+const NcaMetaDataHashDataInfo& NcaFsHeaderReader::GetSparseMetaDataHashDataInfo() const {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_data_info;
+}
+
+NcaFsHeader::MetaDataHashType NcaFsHeaderReader::GetSparseMetaHashType() const {
+    ASSERT(this->IsInitialized());
+    return m_data.meta_data_hash_type;
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_pooled_buffer.cpp

@@ -0,0 +1,61 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "common/alignment.h"
+#include "core/file_sys/fssystem/fssystem_pooled_buffer.h"
+
+namespace FileSys {
+
+namespace {
+
+constexpr size_t HeapBlockSize = BufferPoolAlignment;
+static_assert(HeapBlockSize == 4_KiB);
+
+// A heap block is 4KiB. An order is a power of two.
+// This gives blocks of the order 32KiB, 512KiB, 4MiB.
+constexpr s32 HeapOrderMax = 7;
+constexpr s32 HeapOrderMaxForLarge = HeapOrderMax + 3;
+
+constexpr size_t HeapAllocatableSizeMax = HeapBlockSize * (static_cast<size_t>(1) << HeapOrderMax);
+constexpr size_t HeapAllocatableSizeMaxForLarge =
+    HeapBlockSize * (static_cast<size_t>(1) << HeapOrderMaxForLarge);
+
+} // namespace
+
+size_t PooledBuffer::GetAllocatableSizeMaxCore(bool large) {
+    return large ? HeapAllocatableSizeMaxForLarge : HeapAllocatableSizeMax;
+}
+
+void PooledBuffer::AllocateCore(size_t ideal_size, size_t required_size, bool large) {
+    // Ensure preconditions.
+    ASSERT(m_buffer == nullptr);
+
+    // Check that we can allocate this size.
+    ASSERT(required_size <= GetAllocatableSizeMaxCore(large));
+
+    const size_t target_size =
+        std::min(std::max(ideal_size, required_size), GetAllocatableSizeMaxCore(large));
+
+    // Dummy implementation for allocate.
+    if (target_size > 0) {
+        m_buffer =
+            reinterpret_cast<char*>(::operator new(target_size, std::align_val_t{HeapBlockSize}));
+        m_size = target_size;
+
+        // Ensure postconditions.
+        ASSERT(m_buffer != nullptr);
+    }
+}
+
+void PooledBuffer::Shrink(size_t ideal_size) {
+    ASSERT(ideal_size <= GetAllocatableSizeMaxCore(true));
+
+    // Shrinking to zero means that we have no buffer.
+    if (ideal_size == 0) {
+        ::operator delete(m_buffer, std::align_val_t{HeapBlockSize});
+        m_buffer = nullptr;
+        m_size = ideal_size;
+    }
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_pooled_buffer.h

@@ -0,0 +1,95 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+#include "common/literals.h"
+#include "core/hle/result.h"
+
+namespace FileSys {
+
+using namespace Common::Literals;
+
+constexpr inline size_t BufferPoolAlignment = 4_KiB;
+constexpr inline size_t BufferPoolWorkSize = 320;
+
+class PooledBuffer {
+    YUZU_NON_COPYABLE(PooledBuffer);
+
+public:
+    // Constructor/Destructor.
+    constexpr PooledBuffer() : m_buffer(), m_size() {}
+
+    PooledBuffer(size_t ideal_size, size_t required_size) : m_buffer(), m_size() {
+        this->Allocate(ideal_size, required_size);
+    }
+
+    ~PooledBuffer() {
+        this->Deallocate();
+    }
+
+    // Move and assignment.
+    explicit PooledBuffer(PooledBuffer&& rhs) : m_buffer(rhs.m_buffer), m_size(rhs.m_size) {
+        rhs.m_buffer = nullptr;
+        rhs.m_size = 0;
+    }
+
+    PooledBuffer& operator=(PooledBuffer&& rhs) {
+        PooledBuffer(std::move(rhs)).Swap(*this);
+        return *this;
+    }
+
+    // Allocation API.
+    void Allocate(size_t ideal_size, size_t required_size) {
+        return this->AllocateCore(ideal_size, required_size, false);
+    }
+
+    void AllocateParticularlyLarge(size_t ideal_size, size_t required_size) {
+        return this->AllocateCore(ideal_size, required_size, true);
+    }
+
+    void Shrink(size_t ideal_size);
+
+    void Deallocate() {
+        // Shrink the buffer to empty.
+        this->Shrink(0);
+        ASSERT(m_buffer == nullptr);
+    }
+
+    char* GetBuffer() const {
+        ASSERT(m_buffer != nullptr);
+        return m_buffer;
+    }
+
+    size_t GetSize() const {
+        ASSERT(m_buffer != nullptr);
+        return m_size;
+    }
+
+public:
+    static size_t GetAllocatableSizeMax() {
+        return GetAllocatableSizeMaxCore(false);
+    }
+    static size_t GetAllocatableParticularlyLargeSizeMax() {
+        return GetAllocatableSizeMaxCore(true);
+    }
+
+private:
+    static size_t GetAllocatableSizeMaxCore(bool large);
+
+private:
+    void Swap(PooledBuffer& rhs) {
+        std::swap(m_buffer, rhs.m_buffer);
+        std::swap(m_size, rhs.m_size);
+    }
+
+    void AllocateCore(size_t ideal_size, size_t required_size, bool large);
+
+private:
+    char* m_buffer;
+    size_t m_size;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_sparse_storage.cpp

@@ -0,0 +1,39 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/fssystem/fssystem_sparse_storage.h"
+
+namespace FileSys {
+
+size_t SparseStorage::Read(u8* buffer, size_t size, size_t offset) const {
+    // Validate preconditions.
+    ASSERT(this->IsInitialized());
+    ASSERT(buffer != nullptr);
+
+    // Allow zero size.
+    if (size == 0) {
+        return size;
+    }
+
+    SparseStorage* self = const_cast<SparseStorage*>(this);
+
+    if (self->GetEntryTable().IsEmpty()) {
+        BucketTree::Offsets table_offsets;
+        ASSERT(R_SUCCEEDED(self->GetEntryTable().GetOffsets(std::addressof(table_offsets))));
+        ASSERT(table_offsets.IsInclude(offset, size));
+
+        std::memset(buffer, 0, size);
+    } else {
+        self->OperatePerEntry<false, true>(
+            offset, size,
+            [=](VirtualFile storage, s64 data_offset, s64 cur_offset, s64 cur_size) -> Result {
+                storage->Read(reinterpret_cast<u8*>(buffer) + (cur_offset - offset),
+                              static_cast<size_t>(cur_size), data_offset);
+                R_SUCCEED();
+            });
+    }
+
+    return size;
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_sparse_storage.h

@@ -0,0 +1,72 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fssystem_indirect_storage.h"
+
+namespace FileSys {
+
+class SparseStorage : public IndirectStorage {
+    YUZU_NON_COPYABLE(SparseStorage);
+    YUZU_NON_MOVEABLE(SparseStorage);
+
+private:
+    class ZeroStorage : public IReadOnlyStorage {
+    public:
+        ZeroStorage() {}
+        virtual ~ZeroStorage() {}
+
+        virtual size_t GetSize() const override {
+            return std::numeric_limits<size_t>::max();
+        }
+
+        virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+            ASSERT(buffer != nullptr || size == 0);
+
+            if (size > 0) {
+                std::memset(buffer, 0, size);
+            }
+
+            return size;
+        }
+    };
+
+public:
+    SparseStorage() : IndirectStorage(), m_zero_storage(std::make_shared<ZeroStorage>()) {}
+    virtual ~SparseStorage() {}
+
+    using IndirectStorage::Initialize;
+
+    void Initialize(s64 end_offset) {
+        this->GetEntryTable().Initialize(NodeSize, end_offset);
+        this->SetZeroStorage();
+    }
+
+    void SetDataStorage(VirtualFile storage) {
+        ASSERT(this->IsInitialized());
+
+        this->SetStorage(0, storage);
+        this->SetZeroStorage();
+    }
+
+    template <typename T>
+    void SetDataStorage(T storage, s64 offset, s64 size) {
+        ASSERT(this->IsInitialized());
+
+        this->SetStorage(0, storage, offset, size);
+        this->SetZeroStorage();
+    }
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override;
+
+private:
+    void SetZeroStorage() {
+        return this->SetStorage(1, m_zero_storage, 0, std::numeric_limits<s64>::max());
+    }
+
+private:
+    VirtualFile m_zero_storage;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_switch_storage.h

@@ -0,0 +1,80 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/fssystem/fs_i_storage.h"
+
+namespace FileSys {
+
+class RegionSwitchStorage : public IReadOnlyStorage {
+    YUZU_NON_COPYABLE(RegionSwitchStorage);
+    YUZU_NON_MOVEABLE(RegionSwitchStorage);
+
+public:
+    struct Region {
+        s64 offset;
+        s64 size;
+    };
+
+public:
+    RegionSwitchStorage(VirtualFile&& i, VirtualFile&& o, Region r)
+        : m_inside_region_storage(std::move(i)), m_outside_region_storage(std::move(o)),
+          m_region(r) {}
+
+    virtual size_t Read(u8* buffer, size_t size, size_t offset) const override {
+        // Process until we're done.
+        size_t processed = 0;
+        while (processed < size) {
+            // Process on the appropriate storage.
+            s64 cur_size = 0;
+            if (this->CheckRegions(std::addressof(cur_size), offset + processed,
+                                   size - processed)) {
+                m_inside_region_storage->Read(buffer + processed, cur_size, offset + processed);
+            } else {
+                m_outside_region_storage->Read(buffer + processed, cur_size, offset + processed);
+            }
+
+            // Advance.
+            processed += cur_size;
+        }
+
+        return size;
+    }
+
+    virtual size_t GetSize() const override {
+        return m_inside_region_storage->GetSize();
+    }
+
+private:
+    bool CheckRegions(s64* out_current_size, s64 offset, s64 size) const {
+        // Check if our region contains the access.
+        if (m_region.offset <= offset) {
+            if (offset < m_region.offset + m_region.size) {
+                if (m_region.offset + m_region.size <= offset + size) {
+                    *out_current_size = m_region.offset + m_region.size - offset;
+                } else {
+                    *out_current_size = size;
+                }
+                return true;
+            } else {
+                *out_current_size = size;
+                return false;
+            }
+        } else {
+            if (m_region.offset <= offset + size) {
+                *out_current_size = m_region.offset - offset;
+            } else {
+                *out_current_size = size;
+            }
+            return false;
+        }
+    }
+
+private:
+    VirtualFile m_inside_region_storage;
+    VirtualFile m_outside_region_storage;
+    Region m_region;
+};
+
+} // namespace FileSys

core/fs/fssystem/fssystem_utility.cpp

@@ -0,0 +1,27 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/file_sys/fssystem/fssystem_utility.h"
+
+namespace FileSys {
+
+void AddCounter(void* counter_, size_t counter_size, u64 value) {
+    u8* counter = static_cast<u8*>(counter_);
+    u64 remaining = value;
+    u8 carry = 0;
+
+    for (size_t i = 0; i < counter_size; i++) {
+        auto sum = counter[counter_size - 1 - i] + (remaining & 0xFF) + carry;
+        carry = static_cast<u8>(sum >> (sizeof(u8) * 8));
+        auto sum8 = static_cast<u8>(sum & 0xFF);
+
+        counter[counter_size - 1 - i] = sum8;
+
+        remaining >>= (sizeof(u8) * 8);
+        if (carry == 0 && remaining == 0) {
+            break;
+        }
+    }
+}
+
+} // namespace FileSys

core/fs/fssystem/fssystem_utility.h

@@ -0,0 +1,12 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_funcs.h"
+
+namespace FileSys {
+
+void AddCounter(void* counter, size_t counter_size, u64 value);
+
+}

core/fs/ips_layer.cpp

@@ -0,0 +1,344 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <algorithm>
+#include <cstring>
+#include <map>
+#include <sstream>
+#include <string>
+#include <utility>
+
+#include "common/hex_util.h"
+#include "common/logging/log.h"
+#include "common/swap.h"
+#include "core/file_sys/ips_layer.h"
+#include "core/file_sys/vfs/vfs_vector.h"
+
+namespace FileSys {
+
+enum class IPSFileType {
+    IPS,
+    IPS32,
+    Error,
+};
+
+constexpr std::array<std::pair<const char*, const char*>, 11> ESCAPE_CHARACTER_MAP{{
+    {"\\a", "\a"},
+    {"\\b", "\b"},
+    {"\\f", "\f"},
+    {"\\n", "\n"},
+    {"\\r", "\r"},
+    {"\\t", "\t"},
+    {"\\v", "\v"},
+    {"\\\\", "\\"},
+    {"\\\'", "\'"},
+    {"\\\"", "\""},
+    {"\\\?", "\?"},
+}};
+
+static IPSFileType IdentifyMagic(const std::vector<u8>& magic) {
+    if (magic.size() != 5) {
+        return IPSFileType::Error;
+    }
+
+    static constexpr std::array<u8, 5> patch_magic{{'P', 'A', 'T', 'C', 'H'}};
+    if (std::equal(magic.begin(), magic.end(), patch_magic.begin())) {
+        return IPSFileType::IPS;
+    }
+
+    static constexpr std::array<u8, 5> ips32_magic{{'I', 'P', 'S', '3', '2'}};
+    if (std::equal(magic.begin(), magic.end(), ips32_magic.begin())) {
+        return IPSFileType::IPS32;
+    }
+
+    return IPSFileType::Error;
+}
+
+static bool IsEOF(IPSFileType type, const std::vector<u8>& data) {
+    static constexpr std::array<u8, 3> eof{{'E', 'O', 'F'}};
+    if (type == IPSFileType::IPS && std::equal(data.begin(), data.end(), eof.begin())) {
+        return true;
+    }
+
+    static constexpr std::array<u8, 4> eeof{{'E', 'E', 'O', 'F'}};
+    return type == IPSFileType::IPS32 && std::equal(data.begin(), data.end(), eeof.begin());
+}
+
+VirtualFile PatchIPS(const VirtualFile& in, const VirtualFile& ips) {
+    if (in == nullptr || ips == nullptr)
+        return nullptr;
+
+    const auto type = IdentifyMagic(ips->ReadBytes(0x5));
+    if (type == IPSFileType::Error)
+        return nullptr;
+
+    auto in_data = in->ReadAllBytes();
+    if (in_data.size() == 0) {
+        return nullptr;
+    }
+
+    std::vector<u8> temp(type == IPSFileType::IPS ? 3 : 4);
+    u64 offset = 5; // After header
+    while (ips->Read(temp.data(), temp.size(), offset) == temp.size()) {
+        offset += temp.size();
+        if (IsEOF(type, temp)) {
+            break;
+        }
+
+        u32 real_offset{};
+        if (type == IPSFileType::IPS32)
+            real_offset = (temp[0] << 24) | (temp[1] << 16) | (temp[2] << 8) | temp[3];
+        else
+            real_offset = (temp[0] << 16) | (temp[1] << 8) | temp[2];
+
+        if (real_offset > in_data.size()) {
+            return nullptr;
+        }
+
+        u16 data_size{};
+        if (ips->ReadObject(&data_size, offset) != sizeof(u16))
+            return nullptr;
+        data_size = Common::swap16(data_size);
+        offset += sizeof(u16);
+
+        if (data_size == 0) { // RLE
+            u16 rle_size{};
+            if (ips->ReadObject(&rle_size, offset) != sizeof(u16))
+                return nullptr;
+            rle_size = Common::swap16(rle_size);
+            offset += sizeof(u16);
+
+            const auto data = ips->ReadByte(offset++);
+            if (!data)
+                return nullptr;
+
+            if (real_offset + rle_size > in_data.size())
+                rle_size = static_cast<u16>(in_data.size() - real_offset);
+            std::memset(in_data.data() + real_offset, *data, rle_size);
+        } else { // Standard Patch
+            auto read = data_size;
+            if (real_offset + read > in_data.size())
+                read = static_cast<u16>(in_data.size() - real_offset);
+            if (ips->Read(in_data.data() + real_offset, read, offset) != data_size)
+                return nullptr;
+            offset += data_size;
+        }
+    }
+
+    if (!IsEOF(type, temp)) {
+        return nullptr;
+    }
+
+    return std::make_shared<VectorVfsFile>(std::move(in_data), in->GetName(),
+                                           in->GetContainingDirectory());
+}
+
+struct IPSwitchCompiler::IPSwitchPatch {
+    std::string name;
+    bool enabled;
+    std::map<u32, std::vector<u8>> records;
+};
+
+IPSwitchCompiler::IPSwitchCompiler(VirtualFile patch_text_) : patch_text(std::move(patch_text_)) {
+    Parse();
+}
+
+IPSwitchCompiler::~IPSwitchCompiler() = default;
+
+std::array<u8, 32> IPSwitchCompiler::GetBuildID() const {
+    return nso_build_id;
+}
+
+bool IPSwitchCompiler::IsValid() const {
+    return valid;
+}
+
+static bool StartsWith(std::string_view base, std::string_view check) {
+    return base.size() >= check.size() && base.substr(0, check.size()) == check;
+}
+
+static std::string EscapeStringSequences(std::string in) {
+    for (const auto& seq : ESCAPE_CHARACTER_MAP) {
+        for (auto index = in.find(seq.first); index != std::string::npos;
+             index = in.find(seq.first, index)) {
+            in.replace(index, std::strlen(seq.first), seq.second);
+            index += std::strlen(seq.second);
+        }
+    }
+
+    return in;
+}
+
+void IPSwitchCompiler::ParseFlag(const std::string& line) {
+    if (StartsWith(line, "@flag offset_shift ")) {
+        // Offset Shift Flag
+        offset_shift = std::strtoll(line.substr(19).c_str(), nullptr, 0);
+    } else if (StartsWith(line, "@little-endian")) {
+        // Set values to read as little endian
+        is_little_endian = true;
+    } else if (StartsWith(line, "@big-endian")) {
+        // Set values to read as big endian
+        is_little_endian = false;
+    } else if (StartsWith(line, "@flag print_values")) {
+        // Force printing of applied values
+        print_values = true;
+    }
+}
+
+void IPSwitchCompiler::Parse() {
+    const auto bytes = patch_text->ReadAllBytes();
+    std::stringstream s;
+    s.write(reinterpret_cast<const char*>(bytes.data()), bytes.size());
+
+    std::vector<std::string> lines;
+    std::string stream_line;
+    while (std::getline(s, stream_line)) {
+        // Remove a trailing \r
+        if (!stream_line.empty() && stream_line.back() == '\r')
+            stream_line.pop_back();
+        lines.push_back(std::move(stream_line));
+    }
+
+    for (std::size_t i = 0; i < lines.size(); ++i) {
+        auto line = lines[i];
+
+        // Remove midline comments
+        std::size_t comment_index = std::string::npos;
+        bool within_string = false;
+        for (std::size_t k = 0; k < line.size(); ++k) {
+            if (line[k] == '\"' && (k > 0 && line[k - 1] != '\\')) {
+                within_string = !within_string;
+            } else if (line[k] == '\\' && (k < line.size() - 1 && line[k + 1] == '\\')) {
+                comment_index = k;
+                break;
+            }
+        }
+
+        if (!StartsWith(line, "//") && comment_index != std::string::npos) {
+            last_comment = line.substr(comment_index + 2);
+            line = line.substr(0, comment_index);
+        }
+
+        if (StartsWith(line, "@stop")) {
+            // Force stop
+            break;
+        } else if (StartsWith(line, "@nsobid-")) {
+            // NSO Build ID Specifier
+            const auto raw_build_id = fmt::format("{:0<64}", line.substr(8));
+            nso_build_id = Common::HexStringToArray<0x20>(raw_build_id);
+        } else if (StartsWith(line, "#")) {
+            // Mandatory Comment
+            LOG_INFO(Loader, "[IPSwitchCompiler ('{}')] Forced output comment: {}",
+                     patch_text->GetName(), line.substr(1));
+        } else if (StartsWith(line, "//")) {
+            // Normal Comment
+            last_comment = line.substr(2);
+            if (last_comment.find_first_not_of(' ') == std::string::npos)
+                continue;
+            if (last_comment.find_first_not_of(' ') != 0)
+                last_comment = last_comment.substr(last_comment.find_first_not_of(' '));
+        } else if (StartsWith(line, "@enabled") || StartsWith(line, "@disabled")) {
+            // Start of patch
+            const auto enabled = StartsWith(line, "@enabled");
+            if (i == 0)
+                return;
+            LOG_INFO(Loader, "[IPSwitchCompiler ('{}')] Parsing patch '{}' ({})",
+                     patch_text->GetName(), last_comment, line.substr(1));
+
+            IPSwitchPatch patch{last_comment, enabled, {}};
+
+            // Read rest of patch
+            while (true) {
+                if (i + 1 >= lines.size()) {
+                    break;
+                }
+
+                const auto& patch_line = lines[++i];
+
+                // Start of new patch
+                if (StartsWith(patch_line, "@enabled") || StartsWith(patch_line, "@disabled")) {
+                    --i;
+                    break;
+                }
+
+                // Check for a flag
+                if (StartsWith(patch_line, "@")) {
+                    ParseFlag(patch_line);
+                    continue;
+                }
+
+                // 11 - 8 hex digit offset + space + minimum two digit overwrite val
+                if (patch_line.length() < 11)
+                    break;
+                auto offset = std::strtoul(patch_line.substr(0, 8).c_str(), nullptr, 16);
+                offset += static_cast<unsigned long>(offset_shift);
+
+                std::vector<u8> replace;
+                // 9 - first char of replacement val
+                if (patch_line[9] == '\"') {
+                    // string replacement
+                    auto end_index = patch_line.find('\"', 10);
+                    if (end_index == std::string::npos || end_index < 10)
+                        return;
+                    while (patch_line[end_index - 1] == '\\') {
+                        end_index = patch_line.find('\"', end_index + 1);
+                        if (end_index == std::string::npos || end_index < 10)
+                            return;
+                    }
+
+                    auto value = patch_line.substr(10, end_index - 10);
+                    value = EscapeStringSequences(value);
+                    replace.reserve(value.size());
+                    std::copy(value.begin(), value.end(), std::back_inserter(replace));
+                } else {
+                    // hex replacement
+                    const auto value =
+                        patch_line.substr(9, patch_line.find_first_of(" /\r\n", 9) - 9);
+                    replace = Common::HexStringToVector(value, is_little_endian);
+                }
+
+                if (print_values) {
+                    LOG_INFO(Loader,
+                             "[IPSwitchCompiler ('{}')]     - Patching value at offset 0x{:08X} "
+                             "with byte string '{}'",
+                             patch_text->GetName(), offset, Common::HexToString(replace));
+                }
+
+                patch.records.insert_or_assign(static_cast<u32>(offset), std::move(replace));
+            }
+
+            patches.push_back(std::move(patch));
+        } else if (StartsWith(line, "@")) {
+            ParseFlag(line);
+        }
+    }
+
+    valid = true;
+}
+
+VirtualFile IPSwitchCompiler::Apply(const VirtualFile& in) const {
+    if (in == nullptr || !valid)
+        return nullptr;
+
+    auto in_data = in->ReadAllBytes();
+
+    for (const auto& patch : patches) {
+        if (!patch.enabled)
+            continue;
+
+        for (const auto& record : patch.records) {
+            if (record.first >= in_data.size())
+                continue;
+            auto replace_size = record.second.size();
+            if (record.first + replace_size > in_data.size())
+                replace_size = in_data.size() - record.first;
+            for (std::size_t i = 0; i < replace_size; ++i)
+                in_data[i + record.first] = record.second[i];
+        }
+    }
+
+    return std::make_shared<VectorVfsFile>(std::move(in_data), in->GetName(),
+                                           in->GetContainingDirectory());
+}
+
+} // namespace FileSys

core/fs/ips_layer.h

@@ -0,0 +1,43 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+#include <memory>
+#include <vector>
+
+#include "common/common_types.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+
+VirtualFile PatchIPS(const VirtualFile& in, const VirtualFile& ips);
+
+class IPSwitchCompiler {
+public:
+    explicit IPSwitchCompiler(VirtualFile patch_text);
+    ~IPSwitchCompiler();
+
+    std::array<u8, 0x20> GetBuildID() const;
+    bool IsValid() const;
+    VirtualFile Apply(const VirtualFile& in) const;
+
+private:
+    struct IPSwitchPatch;
+
+    void ParseFlag(const std::string& flag);
+    void Parse();
+
+    bool valid = false;
+
+    VirtualFile patch_text;
+    std::vector<IPSwitchPatch> patches;
+    std::array<u8, 0x20> nso_build_id{};
+    bool is_little_endian = false;
+    s64 offset_shift = 0;
+    bool print_values = false;
+    std::string last_comment = "";
+};
+
+} // namespace FileSys

core/fs/kernel_executable.cpp

@@ -0,0 +1,230 @@
+// SPDX-FileCopyrightText: Copyright 2019 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <cstring>
+
+#include "common/string_util.h"
+#include "core/file_sys/kernel_executable.h"
+#include "core/file_sys/vfs/vfs_offset.h"
+#include "core/loader/loader.h"
+
+namespace FileSys {
+
+constexpr u32 INI_MAX_KIPS = 0x50;
+
+namespace {
+bool DecompressBLZ(std::vector<u8>& data) {
+    if (data.size() < 0xC)
+        return {};
+
+    const auto data_size = data.size() - 0xC;
+
+    u32 compressed_size{};
+    u32 init_index{};
+    u32 additional_size{};
+    std::memcpy(&compressed_size, data.data() + data_size, sizeof(u32));
+    std::memcpy(&init_index, data.data() + data_size + 0x4, sizeof(u32));
+    std::memcpy(&additional_size, data.data() + data_size + 0x8, sizeof(u32));
+
+    const auto start_offset = data.size() - compressed_size;
+    data.resize(compressed_size + additional_size + start_offset);
+
+    std::size_t index = compressed_size - init_index;
+    std::size_t out_index = compressed_size + additional_size;
+
+    while (out_index > 0) {
+        --index;
+        auto control = data[index + start_offset];
+        for (size_t i = 0; i < 8; ++i) {
+            if (((control << i) & 0x80) > 0) {
+                if (index < 2) {
+                    return false;
+                }
+                index -= 2;
+                std::size_t segment_offset =
+                    data[index + start_offset] | data[index + start_offset + 1] << 8;
+                std::size_t segment_size = ((segment_offset >> 12) & 0xF) + 3;
+                segment_offset &= 0xFFF;
+                segment_offset += 3;
+
+                if (out_index < segment_size)
+                    segment_size = out_index;
+
+                if (out_index < segment_size) {
+                    return false;
+                }
+
+                out_index -= segment_size;
+
+                for (size_t j = 0; j < segment_size; ++j) {
+                    if (out_index + j + segment_offset + start_offset >= data.size()) {
+                        return false;
+                    }
+                    data[out_index + j + start_offset] =
+                        data[out_index + j + segment_offset + start_offset];
+                }
+            } else {
+                if (out_index < 1) {
+                    return false;
+                }
+                --out_index;
+                --index;
+                data[out_index + start_offset] = data[index + start_offset];
+            }
+
+            if (out_index == 0)
+                break;
+        }
+    }
+
+    return true;
+}
+} // Anonymous namespace
+
+KIP::KIP(const VirtualFile& file) : status(Loader::ResultStatus::Success) {
+    if (file == nullptr) {
+        status = Loader::ResultStatus::ErrorNullFile;
+        return;
+    }
+
+    if (file->GetSize() < sizeof(KIPHeader) || file->ReadObject(&header) != sizeof(KIPHeader)) {
+        status = Loader::ResultStatus::ErrorBadKIPHeader;
+        return;
+    }
+
+    if (header.magic != Common::MakeMagic('K', 'I', 'P', '1')) {
+        status = Loader::ResultStatus::ErrorBadKIPHeader;
+        return;
+    }
+
+    u64 offset = sizeof(KIPHeader);
+    for (std::size_t i = 0; i < header.sections.size(); ++i) {
+        auto compressed = file->ReadBytes(header.sections[i].compressed_size, offset);
+        offset += header.sections[i].compressed_size;
+
+        if (header.sections[i].compressed_size == 0 && header.sections[i].decompressed_size != 0) {
+            decompressed_sections[i] = std::vector<u8>(header.sections[i].decompressed_size);
+        } else if (header.sections[i].compressed_size == header.sections[i].decompressed_size) {
+            decompressed_sections[i] = std::move(compressed);
+        } else {
+            decompressed_sections[i] = compressed;
+            if (!DecompressBLZ(decompressed_sections[i])) {
+                status = Loader::ResultStatus::ErrorBLZDecompressionFailed;
+                return;
+            }
+        }
+    }
+}
+
+Loader::ResultStatus KIP::GetStatus() const {
+    return status;
+}
+
+std::string KIP::GetName() const {
+    return Common::StringFromFixedZeroTerminatedBuffer(header.name.data(), header.name.size());
+}
+
+u64 KIP::GetTitleID() const {
+    return header.title_id;
+}
+
+std::vector<u8> KIP::GetSectionDecompressed(u8 index) const {
+    return decompressed_sections[index];
+}
+
+bool KIP::Is64Bit() const {
+    return (header.flags & 0x8) != 0;
+}
+
+bool KIP::Is39BitAddressSpace() const {
+    return (header.flags & 0x10) != 0;
+}
+
+bool KIP::IsService() const {
+    return (header.flags & 0x20) != 0;
+}
+
+std::vector<u32> KIP::GetKernelCapabilities() const {
+    return std::vector<u32>(header.capabilities.begin(), header.capabilities.end());
+}
+
+s32 KIP::GetMainThreadPriority() const {
+    return static_cast<s32>(header.main_thread_priority);
+}
+
+u32 KIP::GetMainThreadStackSize() const {
+    return header.sections[1].attribute;
+}
+
+u32 KIP::GetMainThreadCpuCore() const {
+    return header.default_core;
+}
+
+const std::vector<u8>& KIP::GetTextSection() const {
+    return decompressed_sections[0];
+}
+
+const std::vector<u8>& KIP::GetRODataSection() const {
+    return decompressed_sections[1];
+}
+
+const std::vector<u8>& KIP::GetDataSection() const {
+    return decompressed_sections[2];
+}
+
+u32 KIP::GetTextOffset() const {
+    return header.sections[0].offset;
+}
+
+u32 KIP::GetRODataOffset() const {
+    return header.sections[1].offset;
+}
+
+u32 KIP::GetDataOffset() const {
+    return header.sections[2].offset;
+}
+
+u32 KIP::GetBSSSize() const {
+    return header.sections[3].decompressed_size;
+}
+
+u32 KIP::GetBSSOffset() const {
+    return header.sections[3].offset;
+}
+
+INI::INI(const VirtualFile& file) : status(Loader::ResultStatus::Success) {
+    if (file->GetSize() < sizeof(INIHeader) || file->ReadObject(&header) != sizeof(INIHeader)) {
+        status = Loader::ResultStatus::ErrorBadINIHeader;
+        return;
+    }
+
+    if (header.magic != Common::MakeMagic('I', 'N', 'I', '1')) {
+        status = Loader::ResultStatus::ErrorBadINIHeader;
+        return;
+    }
+
+    if (header.kip_count > INI_MAX_KIPS) {
+        status = Loader::ResultStatus::ErrorINITooManyKIPs;
+        return;
+    }
+
+    u64 offset = sizeof(INIHeader);
+    for (std::size_t i = 0; i < header.kip_count; ++i) {
+        const auto kip_file =
+            std::make_shared<OffsetVfsFile>(file, file->GetSize() - offset, offset);
+        KIP kip(kip_file);
+        if (kip.GetStatus() == Loader::ResultStatus::Success) {
+            kips.push_back(std::move(kip));
+        }
+    }
+}
+
+Loader::ResultStatus INI::GetStatus() const {
+    return status;
+}
+
+const std::vector<KIP>& INI::GetKIPs() const {
+    return kips;
+}
+
+} // namespace FileSys

core/fs/kernel_executable.h

@@ -0,0 +1,106 @@
+// SPDX-FileCopyrightText: Copyright 2019 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+#include <string>
+#include <vector>
+
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+#include "common/swap.h"
+#include "core/file_sys/vfs/vfs_types.h"
+
+namespace Loader {
+enum class ResultStatus : u16;
+}
+
+namespace FileSys {
+
+struct KIPSectionHeader {
+    u32_le offset;
+    u32_le decompressed_size;
+    u32_le compressed_size;
+    u32_le attribute;
+};
+static_assert(sizeof(KIPSectionHeader) == 0x10, "KIPSectionHeader has incorrect size.");
+
+struct KIPHeader {
+    u32_le magic;
+    std::array<char, 0xC> name;
+    u64_le title_id;
+    u32_le process_category;
+    u8 main_thread_priority;
+    u8 default_core;
+    INSERT_PADDING_BYTES(1);
+    u8 flags;
+    std::array<KIPSectionHeader, 6> sections;
+    std::array<u32, 0x20> capabilities;
+};
+static_assert(sizeof(KIPHeader) == 0x100, "KIPHeader has incorrect size.");
+
+struct INIHeader {
+    u32_le magic;
+    u32_le size;
+    u32_le kip_count;
+    INSERT_PADDING_BYTES(0x4);
+};
+static_assert(sizeof(INIHeader) == 0x10, "INIHeader has incorrect size.");
+
+// Kernel Internal Process
+class KIP {
+public:
+    explicit KIP(const VirtualFile& file);
+
+    Loader::ResultStatus GetStatus() const;
+
+    std::string GetName() const;
+    u64 GetTitleID() const;
+    std::vector<u8> GetSectionDecompressed(u8 index) const;
+
+    // Executable Flags
+    bool Is64Bit() const;
+    bool Is39BitAddressSpace() const;
+    bool IsService() const;
+
+    std::vector<u32> GetKernelCapabilities() const;
+
+    s32 GetMainThreadPriority() const;
+    u32 GetMainThreadStackSize() const;
+    u32 GetMainThreadCpuCore() const;
+
+    const std::vector<u8>& GetTextSection() const;
+    const std::vector<u8>& GetRODataSection() const;
+    const std::vector<u8>& GetDataSection() const;
+
+    u32 GetTextOffset() const;
+    u32 GetRODataOffset() const;
+    u32 GetDataOffset() const;
+
+    u32 GetBSSSize() const;
+    u32 GetBSSOffset() const;
+
+private:
+    Loader::ResultStatus status;
+
+    KIPHeader header{};
+    std::array<std::vector<u8>, 6> decompressed_sections;
+};
+
+class INI {
+public:
+    explicit INI(const VirtualFile& file);
+
+    Loader::ResultStatus GetStatus() const;
+
+    const std::vector<KIP>& GetKIPs() const;
+
+private:
+    Loader::ResultStatus status;
+
+    INIHeader header{};
+    std::vector<KIP> kips;
+};
+
+} // namespace FileSys

core/fs/nca_metadata.cpp

@@ -0,0 +1,128 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <cstring>
+#include "common/common_types.h"
+#include "common/logging/log.h"
+#include "common/swap.h"
+#include "core/file_sys/nca_metadata.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+
+CNMT::CNMT(VirtualFile file) {
+    if (file->ReadObject(&header) != sizeof(CNMTHeader))
+        return;
+
+    // If type is {Application, Update, AOC} has opt-header.
+    if (header.type >= TitleType::Application && header.type <= TitleType::AOC) {
+        if (file->ReadObject(&opt_header, sizeof(CNMTHeader)) != sizeof(OptionalHeader)) {
+            LOG_WARNING(Loader, "Failed to read optional header.");
+        }
+    }
+
+    for (u16 i = 0; i < header.number_content_entries; ++i) {
+        auto& next = content_records.emplace_back(ContentRecord{});
+        if (file->ReadObject(&next, sizeof(CNMTHeader) + i * sizeof(ContentRecord) +
+                                        header.table_offset) != sizeof(ContentRecord)) {
+            content_records.erase(content_records.end() - 1);
+        }
+    }
+
+    for (u16 i = 0; i < header.number_meta_entries; ++i) {
+        auto& next = meta_records.emplace_back(MetaRecord{});
+        if (file->ReadObject(&next, sizeof(CNMTHeader) + i * sizeof(MetaRecord) +
+                                        header.table_offset) != sizeof(MetaRecord)) {
+            meta_records.erase(meta_records.end() - 1);
+        }
+    }
+}
+
+CNMT::CNMT(CNMTHeader header_, OptionalHeader opt_header_,
+           std::vector<ContentRecord> content_records_, std::vector<MetaRecord> meta_records_)
+    : header(std::move(header_)), opt_header(std::move(opt_header_)),
+      content_records(std::move(content_records_)), meta_records(std::move(meta_records_)) {}
+
+CNMT::~CNMT() = default;
+
+const CNMTHeader& CNMT::GetHeader() const {
+    return header;
+}
+
+u64 CNMT::GetTitleID() const {
+    return header.title_id;
+}
+
+u32 CNMT::GetTitleVersion() const {
+    return header.title_version;
+}
+
+TitleType CNMT::GetType() const {
+    return header.type;
+}
+
+const std::vector<ContentRecord>& CNMT::GetContentRecords() const {
+    return content_records;
+}
+
+const std::vector<MetaRecord>& CNMT::GetMetaRecords() const {
+    return meta_records;
+}
+
+bool CNMT::UnionRecords(const CNMT& other) {
+    bool change = false;
+    for (const auto& rec : other.content_records) {
+        const auto iter = std::find_if(content_records.begin(), content_records.end(),
+                                       [&rec](const ContentRecord& r) {
+                                           return r.nca_id == rec.nca_id && r.type == rec.type;
+                                       });
+        if (iter == content_records.end()) {
+            content_records.emplace_back(rec);
+            ++header.number_content_entries;
+            change = true;
+        }
+    }
+    for (const auto& rec : other.meta_records) {
+        const auto iter =
+            std::find_if(meta_records.begin(), meta_records.end(), [&rec](const MetaRecord& r) {
+                return r.title_id == rec.title_id && r.title_version == rec.title_version &&
+                       r.type == rec.type;
+            });
+        if (iter == meta_records.end()) {
+            meta_records.emplace_back(rec);
+            ++header.number_meta_entries;
+            change = true;
+        }
+    }
+    return change;
+}
+
+std::vector<u8> CNMT::Serialize() const {
+    const bool has_opt_header =
+        header.type >= TitleType::Application && header.type <= TitleType::AOC;
+    const auto dead_zone = header.table_offset + sizeof(CNMTHeader);
+    std::vector<u8> out(
+        std::max(sizeof(CNMTHeader) + (has_opt_header ? sizeof(OptionalHeader) : 0), dead_zone) +
+        content_records.size() * sizeof(ContentRecord) + meta_records.size() * sizeof(MetaRecord));
+    memcpy(out.data(), &header, sizeof(CNMTHeader));
+
+    // Optional Header
+    if (has_opt_header) {
+        memcpy(out.data() + sizeof(CNMTHeader), &opt_header, sizeof(OptionalHeader));
+    }
+
+    u64_le offset = header.table_offset;
+
+    for (const auto& rec : content_records) {
+        memcpy(out.data() + offset + sizeof(CNMTHeader), &rec, sizeof(ContentRecord));
+        offset += sizeof(ContentRecord);
+    }
+
+    for (const auto& rec : meta_records) {
+        memcpy(out.data() + offset + sizeof(CNMTHeader), &rec, sizeof(MetaRecord));
+        offset += sizeof(MetaRecord);
+    }
+
+    return out;
+}
+} // namespace FileSys

core/fs/nca_metadata.h

@@ -0,0 +1,113 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+#include <vector>
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+#include "common/swap.h"
+#include "core/file_sys/vfs/vfs_types.h"
+
+namespace FileSys {
+class CNMT;
+
+struct CNMTHeader;
+struct OptionalHeader;
+
+enum class TitleType : u8 {
+    SystemProgram = 0x01,
+    SystemDataArchive = 0x02,
+    SystemUpdate = 0x03,
+    FirmwarePackageA = 0x04,
+    FirmwarePackageB = 0x05,
+    Application = 0x80,
+    Update = 0x81,
+    AOC = 0x82,
+    DeltaTitle = 0x83,
+};
+
+enum class ContentRecordType : u8 {
+    Meta = 0,
+    Program = 1,
+    Data = 2,
+    Control = 3,
+    HtmlDocument = 4,
+    LegalInformation = 5,
+    DeltaFragment = 6,
+};
+
+struct ContentRecord {
+    std::array<u8, 0x20> hash;
+    std::array<u8, 0x10> nca_id;
+    std::array<u8, 0x6> size;
+    ContentRecordType type;
+    INSERT_PADDING_BYTES(1);
+};
+static_assert(sizeof(ContentRecord) == 0x38, "ContentRecord has incorrect size.");
+
+constexpr ContentRecord EMPTY_META_CONTENT_RECORD{{}, {}, {}, ContentRecordType::Meta, {}};
+
+struct MetaRecord {
+    u64_le title_id;
+    u32_le title_version;
+    TitleType type;
+    u8 install_byte;
+    INSERT_PADDING_BYTES(2);
+};
+static_assert(sizeof(MetaRecord) == 0x10, "MetaRecord has incorrect size.");
+
+struct OptionalHeader {
+    u64_le title_id;
+    u64_le minimum_version;
+};
+static_assert(sizeof(OptionalHeader) == 0x10, "OptionalHeader has incorrect size.");
+
+struct CNMTHeader {
+    u64_le title_id;
+    u32_le title_version;
+    TitleType type;
+    u8 reserved;
+    u16_le table_offset;
+    u16_le number_content_entries;
+    u16_le number_meta_entries;
+    u8 attributes;
+    std::array<u8, 2> reserved2;
+    u8 is_committed;
+    u32_le required_download_system_version;
+    std::array<u8, 4> reserved3;
+};
+static_assert(sizeof(CNMTHeader) == 0x20, "CNMTHeader has incorrect size.");
+
+// A class representing the format used by NCA metadata files, typically named {}.cnmt.nca or
+// meta0.ncd. These describe which NCA's belong with which titles in the registered cache.
+class CNMT {
+public:
+    explicit CNMT(VirtualFile file);
+    CNMT(CNMTHeader header_, OptionalHeader opt_header_,
+         std::vector<ContentRecord> content_records_, std::vector<MetaRecord> meta_records_);
+    ~CNMT();
+
+    const CNMTHeader& GetHeader() const;
+    u64 GetTitleID() const;
+    u32 GetTitleVersion() const;
+    TitleType GetType() const;
+
+    const std::vector<ContentRecord>& GetContentRecords() const;
+    const std::vector<MetaRecord>& GetMetaRecords() const;
+
+    bool UnionRecords(const CNMT& other);
+    std::vector<u8> Serialize() const;
+
+private:
+    CNMTHeader header;
+    OptionalHeader opt_header;
+    std::vector<ContentRecord> content_records;
+    std::vector<MetaRecord> meta_records;
+
+    // TODO(DarkLordZach): According to switchbrew, for Patch-type there is additional data
+    // after the table. This is not documented, unfortunately.
+};
+
+} // namespace FileSys

core/fs/partition_filesystem.cpp

@@ -0,0 +1,116 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <algorithm>
+#include <cstddef>
+#include <cstring>
+#include <iterator>
+#include <utility>
+
+#include "common/logging/log.h"
+#include "core/file_sys/partition_filesystem.h"
+#include "core/file_sys/vfs/vfs_offset.h"
+#include "core/loader/loader.h"
+
+namespace FileSys {
+
+bool PartitionFilesystem::Header::HasValidMagicValue() const {
+    return magic == Common::MakeMagic('H', 'F', 'S', '0') ||
+           magic == Common::MakeMagic('P', 'F', 'S', '0');
+}
+
+PartitionFilesystem::PartitionFilesystem(VirtualFile file) {
+    // At least be as large as the header
+    if (file->GetSize() < sizeof(Header)) {
+        status = Loader::ResultStatus::ErrorBadPFSHeader;
+        return;
+    }
+
+    // For cartridges, HFSs can get very large, so we need to calculate the size up to
+    // the actual content itself instead of just blindly reading in the entire file.
+    if (sizeof(Header) != file->ReadObject(&pfs_header)) {
+        status = Loader::ResultStatus::ErrorBadPFSHeader;
+        return;
+    }
+
+    if (!pfs_header.HasValidMagicValue()) {
+        status = Loader::ResultStatus::ErrorBadPFSHeader;
+        return;
+    }
+
+    is_hfs = pfs_header.magic == Common::MakeMagic('H', 'F', 'S', '0');
+
+    std::size_t entry_size = is_hfs ? sizeof(HFSEntry) : sizeof(PFSEntry);
+    std::size_t metadata_size =
+        sizeof(Header) + (pfs_header.num_entries * entry_size) + pfs_header.strtab_size;
+
+    // Actually read in now...
+    std::vector<u8> file_data = file->ReadBytes(metadata_size);
+    const std::size_t total_size = file_data.size();
+    file_data.push_back(0);
+
+    if (total_size != metadata_size) {
+        status = Loader::ResultStatus::ErrorIncorrectPFSFileSize;
+        return;
+    }
+
+    std::size_t entries_offset = sizeof(Header);
+    std::size_t strtab_offset = entries_offset + (pfs_header.num_entries * entry_size);
+    content_offset = strtab_offset + pfs_header.strtab_size;
+    for (u16 i = 0; i < pfs_header.num_entries; i++) {
+        FSEntry entry;
+
+        memcpy(&entry, &file_data[entries_offset + (i * entry_size)], sizeof(FSEntry));
+        std::string name(
+            reinterpret_cast<const char*>(&file_data[strtab_offset + entry.strtab_offset]));
+
+        offsets.insert_or_assign(name, content_offset + entry.offset);
+        sizes.insert_or_assign(name, entry.size);
+
+        pfs_files.emplace_back(std::make_shared<OffsetVfsFile>(
+            file, entry.size, content_offset + entry.offset, std::move(name)));
+    }
+
+    status = Loader::ResultStatus::Success;
+}
+
+PartitionFilesystem::~PartitionFilesystem() = default;
+
+Loader::ResultStatus PartitionFilesystem::GetStatus() const {
+    return status;
+}
+
+std::map<std::string, u64> PartitionFilesystem::GetFileOffsets() const {
+    return offsets;
+}
+
+std::map<std::string, u64> PartitionFilesystem::GetFileSizes() const {
+    return sizes;
+}
+
+std::vector<VirtualFile> PartitionFilesystem::GetFiles() const {
+    return pfs_files;
+}
+
+std::vector<VirtualDir> PartitionFilesystem::GetSubdirectories() const {
+    return {};
+}
+
+std::string PartitionFilesystem::GetName() const {
+    return is_hfs ? "HFS0" : "PFS0";
+}
+
+VirtualDir PartitionFilesystem::GetParentDirectory() const {
+    // TODO(DarkLordZach): Add support for nested containers.
+    return nullptr;
+}
+
+void PartitionFilesystem::PrintDebugInfo() const {
+    LOG_DEBUG(Service_FS, "Magic:                  {:.4}", pfs_header.magic);
+    LOG_DEBUG(Service_FS, "Files:                  {}", pfs_header.num_entries);
+    for (u32 i = 0; i < pfs_header.num_entries; i++) {
+        LOG_DEBUG(Service_FS, " > File {}:              {} (0x{:X} bytes)", i,
+                  pfs_files[i]->GetName(), pfs_files[i]->GetSize());
+    }
+}
+} // namespace FileSys

core/fs/partition_filesystem.h

@@ -0,0 +1,91 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+#include <string>
+#include <vector>
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+#include "common/swap.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace Loader {
+enum class ResultStatus : u16;
+}
+
+namespace FileSys {
+
+/**
+ * Helper which implements an interface to parse PFS/HFS filesystems.
+ * Data can either be loaded from a file path or data with an offset into it.
+ */
+class PartitionFilesystem : public ReadOnlyVfsDirectory {
+public:
+    explicit PartitionFilesystem(VirtualFile file);
+    ~PartitionFilesystem() override;
+
+    Loader::ResultStatus GetStatus() const;
+
+    std::map<std::string, u64> GetFileOffsets() const;
+    std::map<std::string, u64> GetFileSizes() const;
+
+    std::vector<VirtualFile> GetFiles() const override;
+    std::vector<VirtualDir> GetSubdirectories() const override;
+    std::string GetName() const override;
+    VirtualDir GetParentDirectory() const override;
+    void PrintDebugInfo() const;
+
+private:
+    struct Header {
+        u32_le magic;
+        u32_le num_entries;
+        u32_le strtab_size;
+        INSERT_PADDING_BYTES(0x4);
+
+        bool HasValidMagicValue() const;
+    };
+
+    static_assert(sizeof(Header) == 0x10, "PFS/HFS header structure size is wrong");
+
+#pragma pack(push, 1)
+    struct FSEntry {
+        u64_le offset;
+        u64_le size;
+        u32_le strtab_offset;
+    };
+
+    static_assert(sizeof(FSEntry) == 0x14, "FS entry structure size is wrong");
+
+    struct PFSEntry {
+        FSEntry fs_entry;
+        INSERT_PADDING_BYTES(0x4);
+    };
+
+    static_assert(sizeof(PFSEntry) == 0x18, "PFS entry structure size is wrong");
+
+    struct HFSEntry {
+        FSEntry fs_entry;
+        u32_le hash_region_size;
+        INSERT_PADDING_BYTES(0x8);
+        std::array<char, 0x20> hash;
+    };
+
+    static_assert(sizeof(HFSEntry) == 0x40, "HFS entry structure size is wrong");
+
+#pragma pack(pop)
+
+    Loader::ResultStatus status{};
+
+    Header pfs_header{};
+    bool is_hfs = false;
+    std::size_t content_offset = 0;
+
+    std::map<std::string, u64> offsets;
+    std::map<std::string, u64> sizes;
+
+    std::vector<VirtualFile> pfs_files;
+};
+
+} // namespace FileSys

core/fs/patch_manager.cpp

@@ -0,0 +1,696 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <algorithm>
+#include <array>
+#include <cstddef>
+#include <cstring>
+
+#include "common/hex_util.h"
+#include "common/logging/log.h"
+#include "common/settings.h"
+#ifndef _WIN32
+#include "common/string_util.h"
+#endif
+
+#include "core/core.h"
+#include "core/file_sys/common_funcs.h"
+#include "core/file_sys/content_archive.h"
+#include "core/file_sys/control_metadata.h"
+#include "core/file_sys/ips_layer.h"
+#include "core/file_sys/patch_manager.h"
+#include "core/file_sys/registered_cache.h"
+#include "core/file_sys/romfs.h"
+#include "core/file_sys/vfs/vfs_cached.h"
+#include "core/file_sys/vfs/vfs_layered.h"
+#include "core/file_sys/vfs/vfs_vector.h"
+#include "core/hle/service/filesystem/filesystem.h"
+#include "core/hle/service/ns/language.h"
+#include "core/hle/service/set/settings_server.h"
+#include "core/loader/loader.h"
+#include "core/loader/nso.h"
+#include "core/memory/cheat_engine.h"
+
+namespace FileSys {
+namespace {
+
+constexpr u32 SINGLE_BYTE_MODULUS = 0x100;
+
+constexpr std::array<const char*, 14> EXEFS_FILE_NAMES{
+    "main",    "main.npdm", "rtld",    "sdk",     "subsdk0", "subsdk1", "subsdk2",
+    "subsdk3", "subsdk4",   "subsdk5", "subsdk6", "subsdk7", "subsdk8", "subsdk9",
+};
+
+enum class TitleVersionFormat : u8 {
+    ThreeElements, ///< vX.Y.Z
+    FourElements,  ///< vX.Y.Z.W
+};
+
+std::string FormatTitleVersion(u32 version,
+                               TitleVersionFormat format = TitleVersionFormat::ThreeElements) {
+    std::array<u8, sizeof(u32)> bytes{};
+    bytes[0] = static_cast<u8>(version % SINGLE_BYTE_MODULUS);
+    for (std::size_t i = 1; i < bytes.size(); ++i) {
+        version /= SINGLE_BYTE_MODULUS;
+        bytes[i] = static_cast<u8>(version % SINGLE_BYTE_MODULUS);
+    }
+
+    if (format == TitleVersionFormat::FourElements) {
+        return fmt::format("v{}.{}.{}.{}", bytes[3], bytes[2], bytes[1], bytes[0]);
+    }
+    return fmt::format("v{}.{}.{}", bytes[3], bytes[2], bytes[1]);
+}
+
+// Returns a directory with name matching name case-insensitive. Returns nullptr if directory
+// doesn't have a directory with name.
+VirtualDir FindSubdirectoryCaseless(const VirtualDir dir, std::string_view name) {
+#ifdef _WIN32
+    return dir->GetSubdirectory(name);
+#else
+    const auto subdirs = dir->GetSubdirectories();
+    for (const auto& subdir : subdirs) {
+        std::string dir_name = Common::ToLower(subdir->GetName());
+        if (dir_name == name) {
+            return subdir;
+        }
+    }
+
+    return nullptr;
+#endif
+}
+
+std::optional<std::vector<Core::Memory::CheatEntry>> ReadCheatFileFromFolder(
+    u64 title_id, const PatchManager::BuildID& build_id_, const VirtualDir& base_path, bool upper) {
+    const auto build_id_raw = Common::HexToString(build_id_, upper);
+    const auto build_id = build_id_raw.substr(0, sizeof(u64) * 2);
+    const auto file = base_path->GetFile(fmt::format("{}.txt", build_id));
+
+    if (file == nullptr) {
+        LOG_INFO(Common_Filesystem, "No cheats file found for title_id={:016X}, build_id={}",
+                 title_id, build_id);
+        return std::nullopt;
+    }
+
+    std::vector<u8> data(file->GetSize());
+    if (file->Read(data.data(), data.size()) != data.size()) {
+        LOG_INFO(Common_Filesystem, "Failed to read cheats file for title_id={:016X}, build_id={}",
+                 title_id, build_id);
+        return std::nullopt;
+    }
+
+    const Core::Memory::TextCheatParser parser;
+    return parser.Parse(std::string_view(reinterpret_cast<const char*>(data.data()), data.size()));
+}
+
+void AppendCommaIfNotEmpty(std::string& to, std::string_view with) {
+    if (to.empty()) {
+        to += with;
+    } else {
+        to += ", ";
+        to += with;
+    }
+}
+
+bool IsDirValidAndNonEmpty(const VirtualDir& dir) {
+    return dir != nullptr && (!dir->GetFiles().empty() || !dir->GetSubdirectories().empty());
+}
+} // Anonymous namespace
+
+PatchManager::PatchManager(u64 title_id_,
+                           const Service::FileSystem::FileSystemController& fs_controller_,
+                           const ContentProvider& content_provider_)
+    : title_id{title_id_}, fs_controller{fs_controller_}, content_provider{content_provider_} {}
+
+PatchManager::~PatchManager() = default;
+
+u64 PatchManager::GetTitleID() const {
+    return title_id;
+}
+
+VirtualDir PatchManager::PatchExeFS(VirtualDir exefs) const {
+    LOG_INFO(Loader, "Patching ExeFS for title_id={:016X}", title_id);
+
+    if (exefs == nullptr)
+        return exefs;
+
+    const auto& disabled = Settings::values.disabled_addons[title_id];
+    const auto update_disabled =
+        std::find(disabled.cbegin(), disabled.cend(), "Update") != disabled.cend();
+
+    // Game Updates
+    const auto update_tid = GetUpdateTitleID(title_id);
+    const auto update = content_provider.GetEntry(update_tid, ContentRecordType::Program);
+
+    if (!update_disabled && update != nullptr && update->GetExeFS() != nullptr) {
+        LOG_INFO(Loader, "    ExeFS: Update ({}) applied successfully",
+                 FormatTitleVersion(content_provider.GetEntryVersion(update_tid).value_or(0)));
+        exefs = update->GetExeFS();
+    }
+
+    // LayeredExeFS
+    const auto load_dir = fs_controller.GetModificationLoadRoot(title_id);
+    const auto sdmc_load_dir = fs_controller.GetSDMCModificationLoadRoot(title_id);
+
+    std::vector<VirtualDir> patch_dirs = {sdmc_load_dir};
+    if (load_dir != nullptr) {
+        const auto load_patch_dirs = load_dir->GetSubdirectories();
+        patch_dirs.insert(patch_dirs.end(), load_patch_dirs.begin(), load_patch_dirs.end());
+    }
+
+    std::sort(patch_dirs.begin(), patch_dirs.end(),
+              [](const VirtualDir& l, const VirtualDir& r) { return l->GetName() < r->GetName(); });
+
+    std::vector<VirtualDir> layers;
+    layers.reserve(patch_dirs.size() + 1);
+    for (const auto& subdir : patch_dirs) {
+        if (std::find(disabled.begin(), disabled.end(), subdir->GetName()) != disabled.end())
+            continue;
+
+        auto exefs_dir = FindSubdirectoryCaseless(subdir, "exefs");
+        if (exefs_dir != nullptr)
+            layers.push_back(std::move(exefs_dir));
+    }
+    layers.push_back(exefs);
+
+    auto layered = LayeredVfsDirectory::MakeLayeredDirectory(std::move(layers));
+    if (layered != nullptr) {
+        LOG_INFO(Loader, "    ExeFS: LayeredExeFS patches applied successfully");
+        exefs = std::move(layered);
+    }
+
+    if (Settings::values.dump_exefs) {
+        LOG_INFO(Loader, "Dumping ExeFS for title_id={:016X}", title_id);
+        const auto dump_dir = fs_controller.GetModificationDumpRoot(title_id);
+        if (dump_dir != nullptr) {
+            const auto exefs_dir = GetOrCreateDirectoryRelative(dump_dir, "/exefs");
+            VfsRawCopyD(exefs, exefs_dir);
+        }
+    }
+
+    return exefs;
+}
+
+std::vector<VirtualFile> PatchManager::CollectPatches(const std::vector<VirtualDir>& patch_dirs,
+                                                      const std::string& build_id) const {
+    const auto& disabled = Settings::values.disabled_addons[title_id];
+    const auto nso_build_id = fmt::format("{:0<64}", build_id);
+
+    std::vector<VirtualFile> out;
+    out.reserve(patch_dirs.size());
+    for (const auto& subdir : patch_dirs) {
+        if (std::find(disabled.cbegin(), disabled.cend(), subdir->GetName()) != disabled.cend())
+            continue;
+
+        auto exefs_dir = FindSubdirectoryCaseless(subdir, "exefs");
+        if (exefs_dir != nullptr) {
+            for (const auto& file : exefs_dir->GetFiles()) {
+                if (file->GetExtension() == "ips") {
+                    auto name = file->GetName();
+
+                    const auto this_build_id =
+                        fmt::format("{:0<64}", name.substr(0, name.find('.')));
+                    if (nso_build_id == this_build_id)
+                        out.push_back(file);
+                } else if (file->GetExtension() == "pchtxt") {
+                    IPSwitchCompiler compiler{file};
+                    if (!compiler.IsValid())
+                        continue;
+
+                    const auto this_build_id = Common::HexToString(compiler.GetBuildID());
+                    if (nso_build_id == this_build_id)
+                        out.push_back(file);
+                }
+            }
+        }
+    }
+
+    return out;
+}
+
+std::vector<u8> PatchManager::PatchNSO(const std::vector<u8>& nso, const std::string& name) const {
+    if (nso.size() < sizeof(Loader::NSOHeader)) {
+        return nso;
+    }
+
+    Loader::NSOHeader header;
+    std::memcpy(&header, nso.data(), sizeof(header));
+
+    if (header.magic != Common::MakeMagic('N', 'S', 'O', '0')) {
+        return nso;
+    }
+
+    const auto build_id_raw = Common::HexToString(header.build_id);
+    const auto build_id = build_id_raw.substr(0, build_id_raw.find_last_not_of('0') + 1);
+
+    if (Settings::values.dump_nso) {
+        LOG_INFO(Loader, "Dumping NSO for name={}, build_id={}, title_id={:016X}", name, build_id,
+                 title_id);
+        const auto dump_dir = fs_controller.GetModificationDumpRoot(title_id);
+        if (dump_dir != nullptr) {
+            const auto nso_dir = GetOrCreateDirectoryRelative(dump_dir, "/nso");
+            const auto file = nso_dir->CreateFile(fmt::format("{}-{}.nso", name, build_id));
+
+            file->Resize(nso.size());
+            file->WriteBytes(nso);
+        }
+    }
+
+    LOG_INFO(Loader, "Patching NSO for name={}, build_id={}", name, build_id);
+
+    const auto load_dir = fs_controller.GetModificationLoadRoot(title_id);
+    if (load_dir == nullptr) {
+        LOG_ERROR(Loader, "Cannot load mods for invalid title_id={:016X}", title_id);
+        return nso;
+    }
+
+    auto patch_dirs = load_dir->GetSubdirectories();
+    std::sort(patch_dirs.begin(), patch_dirs.end(),
+              [](const VirtualDir& l, const VirtualDir& r) { return l->GetName() < r->GetName(); });
+    const auto patches = CollectPatches(patch_dirs, build_id);
+
+    auto out = nso;
+    for (const auto& patch_file : patches) {
+        if (patch_file->GetExtension() == "ips") {
+            LOG_INFO(Loader, "    - Applying IPS patch from mod \"{}\"",
+                     patch_file->GetContainingDirectory()->GetParentDirectory()->GetName());
+            const auto patched = PatchIPS(std::make_shared<VectorVfsFile>(out), patch_file);
+            if (patched != nullptr)
+                out = patched->ReadAllBytes();
+        } else if (patch_file->GetExtension() == "pchtxt") {
+            LOG_INFO(Loader, "    - Applying IPSwitch patch from mod \"{}\"",
+                     patch_file->GetContainingDirectory()->GetParentDirectory()->GetName());
+            const IPSwitchCompiler compiler{patch_file};
+            const auto patched = compiler.Apply(std::make_shared<VectorVfsFile>(out));
+            if (patched != nullptr)
+                out = patched->ReadAllBytes();
+        }
+    }
+
+    if (out.size() < sizeof(Loader::NSOHeader)) {
+        return nso;
+    }
+
+    std::memcpy(out.data(), &header, sizeof(header));
+    return out;
+}
+
+bool PatchManager::HasNSOPatch(const BuildID& build_id_, std::string_view name) const {
+    const auto build_id_raw = Common::HexToString(build_id_);
+    const auto build_id = build_id_raw.substr(0, build_id_raw.find_last_not_of('0') + 1);
+
+    LOG_INFO(Loader, "Querying NSO patch existence for build_id={}, name={}", build_id, name);
+
+    const auto load_dir = fs_controller.GetModificationLoadRoot(title_id);
+    if (load_dir == nullptr) {
+        LOG_ERROR(Loader, "Cannot load mods for invalid title_id={:016X}", title_id);
+        return false;
+    }
+
+    auto patch_dirs = load_dir->GetSubdirectories();
+    std::sort(patch_dirs.begin(), patch_dirs.end(),
+              [](const VirtualDir& l, const VirtualDir& r) { return l->GetName() < r->GetName(); });
+
+    return !CollectPatches(patch_dirs, build_id).empty();
+}
+
+std::vector<Core::Memory::CheatEntry> PatchManager::CreateCheatList(
+    const BuildID& build_id_) const {
+    const auto load_dir = fs_controller.GetModificationLoadRoot(title_id);
+    if (load_dir == nullptr) {
+        LOG_ERROR(Loader, "Cannot load mods for invalid title_id={:016X}", title_id);
+        return {};
+    }
+
+    const auto& disabled = Settings::values.disabled_addons[title_id];
+    auto patch_dirs = load_dir->GetSubdirectories();
+    std::sort(patch_dirs.begin(), patch_dirs.end(),
+              [](const VirtualDir& l, const VirtualDir& r) { return l->GetName() < r->GetName(); });
+
+    std::vector<Core::Memory::CheatEntry> out;
+    for (const auto& subdir : patch_dirs) {
+        if (std::find(disabled.cbegin(), disabled.cend(), subdir->GetName()) != disabled.cend()) {
+            continue;
+        }
+
+        auto cheats_dir = FindSubdirectoryCaseless(subdir, "cheats");
+        if (cheats_dir != nullptr) {
+            if (const auto res = ReadCheatFileFromFolder(title_id, build_id_, cheats_dir, true)) {
+                std::copy(res->begin(), res->end(), std::back_inserter(out));
+                continue;
+            }
+
+            if (const auto res = ReadCheatFileFromFolder(title_id, build_id_, cheats_dir, false)) {
+                std::copy(res->begin(), res->end(), std::back_inserter(out));
+            }
+        }
+    }
+
+    return out;
+}
+
+static void ApplyLayeredFS(VirtualFile& romfs, u64 title_id, ContentRecordType type,
+                           const Service::FileSystem::FileSystemController& fs_controller) {
+    const auto load_dir = fs_controller.GetModificationLoadRoot(title_id);
+    const auto sdmc_load_dir = fs_controller.GetSDMCModificationLoadRoot(title_id);
+    if ((type != ContentRecordType::Program && type != ContentRecordType::Data &&
+         type != ContentRecordType::HtmlDocument) ||
+        (load_dir == nullptr && sdmc_load_dir == nullptr)) {
+        return;
+    }
+
+    const auto& disabled = Settings::values.disabled_addons[title_id];
+    std::vector<VirtualDir> patch_dirs = load_dir->GetSubdirectories();
+    if (std::find(disabled.cbegin(), disabled.cend(), "SDMC") == disabled.cend()) {
+        patch_dirs.push_back(sdmc_load_dir);
+    }
+    std::sort(patch_dirs.begin(), patch_dirs.end(),
+              [](const VirtualDir& l, const VirtualDir& r) { return l->GetName() < r->GetName(); });
+
+    std::vector<VirtualDir> layers;
+    std::vector<VirtualDir> layers_ext;
+    layers.reserve(patch_dirs.size() + 1);
+    layers_ext.reserve(patch_dirs.size() + 1);
+    for (const auto& subdir : patch_dirs) {
+        if (std::find(disabled.cbegin(), disabled.cend(), subdir->GetName()) != disabled.cend()) {
+            continue;
+        }
+
+        auto romfs_dir = FindSubdirectoryCaseless(subdir, "romfs");
+        if (romfs_dir != nullptr)
+            layers.emplace_back(std::make_shared<CachedVfsDirectory>(std::move(romfs_dir)));
+
+        auto ext_dir = FindSubdirectoryCaseless(subdir, "romfs_ext");
+        if (ext_dir != nullptr)
+            layers_ext.emplace_back(std::make_shared<CachedVfsDirectory>(std::move(ext_dir)));
+
+        if (type == ContentRecordType::HtmlDocument) {
+            auto manual_dir = FindSubdirectoryCaseless(subdir, "manual_html");
+            if (manual_dir != nullptr)
+                layers.emplace_back(std::make_shared<CachedVfsDirectory>(std::move(manual_dir)));
+        }
+    }
+
+    // When there are no layers to apply, return early as there is no need to rebuild the RomFS
+    if (layers.empty() && layers_ext.empty()) {
+        return;
+    }
+
+    auto extracted = ExtractRomFS(romfs);
+    if (extracted == nullptr) {
+        return;
+    }
+
+    layers.emplace_back(std::move(extracted));
+
+    auto layered = LayeredVfsDirectory::MakeLayeredDirectory(std::move(layers));
+    if (layered == nullptr) {
+        return;
+    }
+
+    auto layered_ext = LayeredVfsDirectory::MakeLayeredDirectory(std::move(layers_ext));
+
+    auto packed = CreateRomFS(std::move(layered), std::move(layered_ext));
+    if (packed == nullptr) {
+        return;
+    }
+
+    LOG_INFO(Loader, "    RomFS: LayeredFS patches applied successfully");
+    romfs = std::move(packed);
+}
+
+VirtualFile PatchManager::PatchRomFS(const NCA* base_nca, VirtualFile base_romfs,
+                                     ContentRecordType type, VirtualFile packed_update_raw,
+                                     bool apply_layeredfs) const {
+    const auto log_string = fmt::format("Patching RomFS for title_id={:016X}, type={:02X}",
+                                        title_id, static_cast<u8>(type));
+    if (type == ContentRecordType::Program || type == ContentRecordType::Data) {
+        LOG_INFO(Loader, "{}", log_string);
+    } else {
+        LOG_DEBUG(Loader, "{}", log_string);
+    }
+
+    auto romfs = base_romfs;
+
+    // Game Updates
+    const auto update_tid = GetUpdateTitleID(title_id);
+    const auto update_raw = content_provider.GetEntryRaw(update_tid, type);
+
+    const auto& disabled = Settings::values.disabled_addons[title_id];
+    const auto update_disabled =
+        std::find(disabled.cbegin(), disabled.cend(), "Update") != disabled.cend();
+
+    if (!update_disabled && update_raw != nullptr && base_nca != nullptr) {
+        const auto new_nca = std::make_shared<NCA>(update_raw, base_nca);
+        if (new_nca->GetStatus() == Loader::ResultStatus::Success &&
+            new_nca->GetRomFS() != nullptr) {
+            LOG_INFO(Loader, "    RomFS: Update ({}) applied successfully",
+                     FormatTitleVersion(content_provider.GetEntryVersion(update_tid).value_or(0)));
+            romfs = new_nca->GetRomFS();
+            const auto version =
+                FormatTitleVersion(content_provider.GetEntryVersion(update_tid).value_or(0));
+        }
+    } else if (!update_disabled && packed_update_raw != nullptr && base_nca != nullptr) {
+        const auto new_nca = std::make_shared<NCA>(packed_update_raw, base_nca);
+        if (new_nca->GetStatus() == Loader::ResultStatus::Success &&
+            new_nca->GetRomFS() != nullptr) {
+            LOG_INFO(Loader, "    RomFS: Update (PACKED) applied successfully");
+            romfs = new_nca->GetRomFS();
+        }
+    }
+
+    // LayeredFS
+    if (apply_layeredfs) {
+        ApplyLayeredFS(romfs, title_id, type, fs_controller);
+    }
+
+    return romfs;
+}
+
+std::vector<Patch> PatchManager::GetPatches(VirtualFile update_raw) const {
+    if (title_id == 0) {
+        return {};
+    }
+
+    std::vector<Patch> out;
+    const auto& disabled = Settings::values.disabled_addons[title_id];
+
+    // Game Updates
+    const auto update_tid = GetUpdateTitleID(title_id);
+    PatchManager update{update_tid, fs_controller, content_provider};
+    const auto metadata = update.GetControlMetadata();
+    const auto& nacp = metadata.first;
+
+    const auto update_disabled =
+        std::find(disabled.cbegin(), disabled.cend(), "Update") != disabled.cend();
+    Patch update_patch = {.enabled = !update_disabled,
+                          .name = "Update",
+                          .version = "",
+                          .type = PatchType::Update,
+                          .program_id = title_id,
+                          .title_id = title_id};
+
+    if (nacp != nullptr) {
+        update_patch.version = nacp->GetVersionString();
+        out.push_back(update_patch);
+    } else {
+        if (content_provider.HasEntry(update_tid, ContentRecordType::Program)) {
+            const auto meta_ver = content_provider.GetEntryVersion(update_tid);
+            if (meta_ver.value_or(0) == 0) {
+                out.push_back(update_patch);
+            } else {
+                update_patch.version = FormatTitleVersion(*meta_ver);
+                out.push_back(update_patch);
+            }
+        } else if (update_raw != nullptr) {
+            update_patch.version = "PACKED";
+            out.push_back(update_patch);
+        }
+    }
+
+    // General Mods (LayeredFS and IPS)
+    const auto mod_dir = fs_controller.GetModificationLoadRoot(title_id);
+    if (mod_dir != nullptr) {
+        for (const auto& mod : mod_dir->GetSubdirectories()) {
+            std::string types;
+
+            const auto exefs_dir = FindSubdirectoryCaseless(mod, "exefs");
+            if (IsDirValidAndNonEmpty(exefs_dir)) {
+                bool ips = false;
+                bool ipswitch = false;
+                bool layeredfs = false;
+
+                for (const auto& file : exefs_dir->GetFiles()) {
+                    if (file->GetExtension() == "ips") {
+                        ips = true;
+                    } else if (file->GetExtension() == "pchtxt") {
+                        ipswitch = true;
+                    } else if (std::find(EXEFS_FILE_NAMES.begin(), EXEFS_FILE_NAMES.end(),
+                                         file->GetName()) != EXEFS_FILE_NAMES.end()) {
+                        layeredfs = true;
+                    }
+                }
+
+                if (ips)
+                    AppendCommaIfNotEmpty(types, "IPS");
+                if (ipswitch)
+                    AppendCommaIfNotEmpty(types, "IPSwitch");
+                if (layeredfs)
+                    AppendCommaIfNotEmpty(types, "LayeredExeFS");
+            }
+            if (IsDirValidAndNonEmpty(FindSubdirectoryCaseless(mod, "romfs")))
+                AppendCommaIfNotEmpty(types, "LayeredFS");
+            if (IsDirValidAndNonEmpty(FindSubdirectoryCaseless(mod, "cheats")))
+                AppendCommaIfNotEmpty(types, "Cheats");
+
+            if (types.empty())
+                continue;
+
+            const auto mod_disabled =
+                std::find(disabled.begin(), disabled.end(), mod->GetName()) != disabled.end();
+            out.push_back({.enabled = !mod_disabled,
+                           .name = mod->GetName(),
+                           .version = types,
+                           .type = PatchType::Mod,
+                           .program_id = title_id,
+                           .title_id = title_id});
+        }
+    }
+
+    // SDMC mod directory (RomFS LayeredFS)
+    const auto sdmc_mod_dir = fs_controller.GetSDMCModificationLoadRoot(title_id);
+    if (sdmc_mod_dir != nullptr) {
+        std::string types;
+        if (IsDirValidAndNonEmpty(FindSubdirectoryCaseless(sdmc_mod_dir, "exefs"))) {
+            AppendCommaIfNotEmpty(types, "LayeredExeFS");
+        }
+        if (IsDirValidAndNonEmpty(FindSubdirectoryCaseless(sdmc_mod_dir, "romfs"))) {
+            AppendCommaIfNotEmpty(types, "LayeredFS");
+        }
+
+        if (!types.empty()) {
+            const auto mod_disabled =
+                std::find(disabled.begin(), disabled.end(), "SDMC") != disabled.end();
+            out.push_back({.enabled = !mod_disabled,
+                           .name = "SDMC",
+                           .version = types,
+                           .type = PatchType::Mod,
+                           .program_id = title_id,
+                           .title_id = title_id});
+        }
+    }
+
+    // DLC
+    const auto dlc_entries =
+        content_provider.ListEntriesFilter(TitleType::AOC, ContentRecordType::Data);
+    std::vector<ContentProviderEntry> dlc_match;
+    dlc_match.reserve(dlc_entries.size());
+    std::copy_if(dlc_entries.begin(), dlc_entries.end(), std::back_inserter(dlc_match),
+                 [this](const ContentProviderEntry& entry) {
+                     return GetBaseTitleID(entry.title_id) == title_id &&
+                            content_provider.GetEntry(entry)->GetStatus() ==
+                                Loader::ResultStatus::Success;
+                 });
+    if (!dlc_match.empty()) {
+        // Ensure sorted so DLC IDs show in order.
+        std::sort(dlc_match.begin(), dlc_match.end());
+
+        std::string list;
+        for (size_t i = 0; i < dlc_match.size() - 1; ++i)
+            list += fmt::format("{}, ", dlc_match[i].title_id & 0x7FF);
+
+        list += fmt::format("{}", dlc_match.back().title_id & 0x7FF);
+
+        const auto dlc_disabled =
+            std::find(disabled.begin(), disabled.end(), "DLC") != disabled.end();
+        out.push_back({.enabled = !dlc_disabled,
+                       .name = "DLC",
+                       .version = std::move(list),
+                       .type = PatchType::DLC,
+                       .program_id = title_id,
+                       .title_id = dlc_match.back().title_id});
+    }
+
+    return out;
+}
+
+std::optional<u32> PatchManager::GetGameVersion() const {
+    const auto update_tid = GetUpdateTitleID(title_id);
+    if (content_provider.HasEntry(update_tid, ContentRecordType::Program)) {
+        return content_provider.GetEntryVersion(update_tid);
+    }
+
+    return content_provider.GetEntryVersion(title_id);
+}
+
+PatchManager::Metadata PatchManager::GetControlMetadata() const {
+    const auto base_control_nca = content_provider.GetEntry(title_id, ContentRecordType::Control);
+    if (base_control_nca == nullptr) {
+        return {};
+    }
+
+    return ParseControlNCA(*base_control_nca);
+}
+
+PatchManager::Metadata PatchManager::ParseControlNCA(const NCA& nca) const {
+    const auto base_romfs = nca.GetRomFS();
+    if (base_romfs == nullptr) {
+        return {};
+    }
+
+    const auto romfs = PatchRomFS(&nca, base_romfs, ContentRecordType::Control);
+    if (romfs == nullptr) {
+        return {};
+    }
+
+    const auto extracted = ExtractRomFS(romfs);
+    if (extracted == nullptr) {
+        return {};
+    }
+
+    auto nacp_file = extracted->GetFile("control.nacp");
+    if (nacp_file == nullptr) {
+        nacp_file = extracted->GetFile("Control.nacp");
+    }
+
+    auto nacp = nacp_file == nullptr ? nullptr : std::make_unique<NACP>(nacp_file);
+
+    // Get language code from settings
+    const auto language_code = Service::Set::GetLanguageCodeFromIndex(
+        static_cast<u32>(Settings::values.language_index.GetValue()));
+
+    // Convert to application language and get priority list
+    const auto application_language =
+        Service::NS::ConvertToApplicationLanguage(language_code)
+            .value_or(Service::NS::ApplicationLanguage::AmericanEnglish);
+    const auto language_priority_list =
+        Service::NS::GetApplicationLanguagePriorityList(application_language);
+
+    // Convert to language names
+    auto priority_language_names = FileSys::LANGUAGE_NAMES; // Copy
+    if (language_priority_list) {
+        for (size_t i = 0; i < priority_language_names.size(); ++i) {
+            // Relies on FileSys::LANGUAGE_NAMES being in the same order as
+            // Service::NS::ApplicationLanguage
+            const auto language_index = static_cast<u8>(language_priority_list->at(i));
+
+            if (language_index < FileSys::LANGUAGE_NAMES.size()) {
+                priority_language_names[i] = FileSys::LANGUAGE_NAMES[language_index];
+            } else {
+                // Not a catastrophe, unlikely to happen
+                LOG_WARNING(Loader, "Invalid language index {}", language_index);
+            }
+        }
+    }
+
+    // Get first matching icon
+    VirtualFile icon_file;
+    for (const auto& language : priority_language_names) {
+        icon_file = extracted->GetFile(std::string("icon_").append(language).append(".dat"));
+        if (icon_file != nullptr) {
+            break;
+        }
+    }
+
+    return {std::move(nacp), icon_file};
+}
+} // namespace FileSys

core/fs/patch_manager.h

@@ -0,0 +1,103 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <map>
+#include <memory>
+#include <optional>
+#include <string>
+#include "common/common_types.h"
+#include "core/file_sys/nca_metadata.h"
+#include "core/file_sys/vfs/vfs_types.h"
+#include "core/memory/dmnt_cheat_types.h"
+
+namespace Core {
+class System;
+}
+
+namespace Service::FileSystem {
+class FileSystemController;
+}
+
+namespace FileSys {
+
+class ContentProvider;
+class NCA;
+class NACP;
+
+enum class PatchType { Update, DLC, Mod };
+
+struct Patch {
+    bool enabled;
+    std::string name;
+    std::string version;
+    PatchType type;
+    u64 program_id;
+    u64 title_id;
+};
+
+// A centralized class to manage patches to games.
+class PatchManager {
+public:
+    using BuildID = std::array<u8, 0x20>;
+    using Metadata = std::pair<std::unique_ptr<NACP>, VirtualFile>;
+
+    explicit PatchManager(u64 title_id_,
+                          const Service::FileSystem::FileSystemController& fs_controller_,
+                          const ContentProvider& content_provider_);
+    ~PatchManager();
+
+    [[nodiscard]] u64 GetTitleID() const;
+
+    // Currently tracked ExeFS patches:
+    // - Game Updates
+    [[nodiscard]] VirtualDir PatchExeFS(VirtualDir exefs) const;
+
+    // Currently tracked NSO patches:
+    // - IPS
+    // - IPSwitch
+    [[nodiscard]] std::vector<u8> PatchNSO(const std::vector<u8>& nso,
+                                           const std::string& name) const;
+
+    // Checks to see if PatchNSO() will have any effect given the NSO's build ID.
+    // Used to prevent expensive copies in NSO loader.
+    [[nodiscard]] bool HasNSOPatch(const BuildID& build_id, std::string_view name) const;
+
+    // Creates a CheatList object with all
+    [[nodiscard]] std::vector<Core::Memory::CheatEntry> CreateCheatList(
+        const BuildID& build_id) const;
+
+    // Currently tracked RomFS patches:
+    // - Game Updates
+    // - LayeredFS
+    [[nodiscard]] VirtualFile PatchRomFS(const NCA* base_nca, VirtualFile base_romfs,
+                                         ContentRecordType type = ContentRecordType::Program,
+                                         VirtualFile packed_update_raw = nullptr,
+                                         bool apply_layeredfs = true) const;
+
+    // Returns a vector of patches
+    [[nodiscard]] std::vector<Patch> GetPatches(VirtualFile update_raw = nullptr) const;
+
+    // If the game update exists, returns the u32 version field in its Meta-type NCA. If that fails,
+    // it will fallback to the Meta-type NCA of the base game. If that fails, the result will be
+    // std::nullopt
+    [[nodiscard]] std::optional<u32> GetGameVersion() const;
+
+    // Given title_id of the program, attempts to get the control data of the update and parse
+    // it, falling back to the base control data.
+    [[nodiscard]] Metadata GetControlMetadata() const;
+
+    // Version of GetControlMetadata that takes an arbitrary NCA
+    [[nodiscard]] Metadata ParseControlNCA(const NCA& nca) const;
+
+private:
+    [[nodiscard]] std::vector<VirtualFile> CollectPatches(const std::vector<VirtualDir>& patch_dirs,
+                                                          const std::string& build_id) const;
+
+    u64 title_id;
+    const Service::FileSystem::FileSystemController& fs_controller;
+    const ContentProvider& content_provider;
+};
+
+} // namespace FileSys

core/fs/program_metadata.cpp

@@ -0,0 +1,220 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <cstddef>
+#include <vector>
+
+#include "common/logging/log.h"
+#include "common/scope_exit.h"
+#include "core/file_sys/program_metadata.h"
+#include "core/file_sys/vfs/vfs.h"
+#include "core/loader/loader.h"
+
+namespace FileSys {
+
+ProgramMetadata::ProgramMetadata() = default;
+
+ProgramMetadata::~ProgramMetadata() = default;
+
+Loader::ResultStatus ProgramMetadata::Load(VirtualFile file) {
+    const std::size_t total_size = file->GetSize();
+    if (total_size < sizeof(Header)) {
+        return Loader::ResultStatus::ErrorBadNPDMHeader;
+    }
+
+    if (sizeof(Header) != file->ReadObject(&npdm_header)) {
+        return Loader::ResultStatus::ErrorBadNPDMHeader;
+    }
+
+    if (sizeof(AcidHeader) != file->ReadObject(&acid_header, npdm_header.acid_offset)) {
+        return Loader::ResultStatus::ErrorBadACIDHeader;
+    }
+
+    if (sizeof(AciHeader) != file->ReadObject(&aci_header, npdm_header.aci_offset)) {
+        return Loader::ResultStatus::ErrorBadACIHeader;
+    }
+
+    // Load acid_file_access per-component instead of the entire struct, since this struct does not
+    // reflect the layout of the real data.
+    std::size_t current_offset = acid_header.fac_offset;
+    if (sizeof(FileAccessControl::version) != file->ReadBytes(&acid_file_access.version,
+                                                              sizeof(FileAccessControl::version),
+                                                              current_offset)) {
+        return Loader::ResultStatus::ErrorBadFileAccessControl;
+    }
+    if (sizeof(FileAccessControl::permissions) !=
+        file->ReadBytes(&acid_file_access.permissions, sizeof(FileAccessControl::permissions),
+                        current_offset += sizeof(FileAccessControl::version) + 3)) {
+        return Loader::ResultStatus::ErrorBadFileAccessControl;
+    }
+    if (sizeof(FileAccessControl::unknown) !=
+        file->ReadBytes(&acid_file_access.unknown, sizeof(FileAccessControl::unknown),
+                        current_offset + sizeof(FileAccessControl::permissions))) {
+        return Loader::ResultStatus::ErrorBadFileAccessControl;
+    }
+
+    // Load aci_file_access per-component instead of the entire struct, same as acid_file_access
+    current_offset = aci_header.fah_offset;
+    if (sizeof(FileAccessHeader::version) != file->ReadBytes(&aci_file_access.version,
+                                                             sizeof(FileAccessHeader::version),
+                                                             current_offset)) {
+        return Loader::ResultStatus::ErrorBadFileAccessHeader;
+    }
+    if (sizeof(FileAccessHeader::permissions) !=
+        file->ReadBytes(&aci_file_access.permissions, sizeof(FileAccessHeader::permissions),
+                        current_offset += sizeof(FileAccessHeader::version) + 3)) {
+        return Loader::ResultStatus::ErrorBadFileAccessHeader;
+    }
+    if (sizeof(FileAccessHeader::unk_offset) !=
+        file->ReadBytes(&aci_file_access.unk_offset, sizeof(FileAccessHeader::unk_offset),
+                        current_offset += sizeof(FileAccessHeader::permissions))) {
+        return Loader::ResultStatus::ErrorBadFileAccessHeader;
+    }
+    if (sizeof(FileAccessHeader::unk_size) !=
+        file->ReadBytes(&aci_file_access.unk_size, sizeof(FileAccessHeader::unk_size),
+                        current_offset += sizeof(FileAccessHeader::unk_offset))) {
+        return Loader::ResultStatus::ErrorBadFileAccessHeader;
+    }
+    if (sizeof(FileAccessHeader::unk_offset_2) !=
+        file->ReadBytes(&aci_file_access.unk_offset_2, sizeof(FileAccessHeader::unk_offset_2),
+                        current_offset += sizeof(FileAccessHeader::unk_size))) {
+        return Loader::ResultStatus::ErrorBadFileAccessHeader;
+    }
+    if (sizeof(FileAccessHeader::unk_size_2) !=
+        file->ReadBytes(&aci_file_access.unk_size_2, sizeof(FileAccessHeader::unk_size_2),
+                        current_offset + sizeof(FileAccessHeader::unk_offset_2))) {
+        return Loader::ResultStatus::ErrorBadFileAccessHeader;
+    }
+
+    aci_kernel_capabilities.resize(aci_header.kac_size / sizeof(u32));
+    const u64 read_size = aci_header.kac_size;
+    const u64 read_offset = npdm_header.aci_offset + aci_header.kac_offset;
+    if (file->ReadBytes(aci_kernel_capabilities.data(), read_size, read_offset) != read_size) {
+        return Loader::ResultStatus::ErrorBadKernelCapabilityDescriptors;
+    }
+
+    return Loader::ResultStatus::Success;
+}
+
+Loader::ResultStatus ProgramMetadata::Reload(VirtualFile file) {
+    const u64 original_program_id = aci_header.title_id;
+    SCOPE_EXIT {
+        aci_header.title_id = original_program_id;
+    };
+
+    return this->Load(file);
+}
+
+/*static*/ ProgramMetadata ProgramMetadata::GetDefault() {
+    // Allow use of cores 0~3 and thread priorities 16~63.
+    constexpr u32 default_thread_info_capability = 0x30043F7;
+
+    ProgramMetadata result;
+
+    result.LoadManual(
+        true /*is_64_bit*/, FileSys::ProgramAddressSpaceType::Is39Bit /*address_space*/,
+        0x2c /*main_thread_prio*/, 0 /*main_thread_core*/, 0x100000 /*main_thread_stack_size*/,
+        0 /*title_id*/, 0xFFFFFFFFFFFFFFFF /*filesystem_permissions*/, 0 /*system_resource_size*/,
+        {default_thread_info_capability} /*capabilities*/);
+
+    return result;
+}
+
+void ProgramMetadata::LoadManual(bool is_64_bit, ProgramAddressSpaceType address_space,
+                                 s32 main_thread_prio, u32 main_thread_core,
+                                 u32 main_thread_stack_size, u64 title_id,
+                                 u64 filesystem_permissions, u32 system_resource_size,
+                                 KernelCapabilityDescriptors capabilities) {
+    npdm_header.has_64_bit_instructions.Assign(is_64_bit);
+    npdm_header.address_space_type.Assign(address_space);
+    npdm_header.main_thread_priority = static_cast<u8>(main_thread_prio);
+    npdm_header.main_thread_cpu = static_cast<u8>(main_thread_core);
+    npdm_header.main_stack_size = main_thread_stack_size;
+    aci_header.title_id = title_id;
+    aci_file_access.permissions = filesystem_permissions;
+    npdm_header.system_resource_size = system_resource_size;
+    aci_kernel_capabilities = std::move(capabilities);
+}
+
+bool ProgramMetadata::Is64BitProgram() const {
+    return npdm_header.has_64_bit_instructions.As<bool>();
+}
+
+ProgramAddressSpaceType ProgramMetadata::GetAddressSpaceType() const {
+    return npdm_header.address_space_type;
+}
+
+u8 ProgramMetadata::GetMainThreadPriority() const {
+    return npdm_header.main_thread_priority;
+}
+
+u8 ProgramMetadata::GetMainThreadCore() const {
+    return npdm_header.main_thread_cpu;
+}
+
+u32 ProgramMetadata::GetMainThreadStackSize() const {
+    return npdm_header.main_stack_size;
+}
+
+u64 ProgramMetadata::GetTitleID() const {
+    return aci_header.title_id;
+}
+
+u64 ProgramMetadata::GetFilesystemPermissions() const {
+    return aci_file_access.permissions;
+}
+
+u32 ProgramMetadata::GetSystemResourceSize() const {
+    return npdm_header.system_resource_size;
+}
+
+PoolPartition ProgramMetadata::GetPoolPartition() const {
+    return acid_header.pool_partition;
+}
+
+const ProgramMetadata::KernelCapabilityDescriptors& ProgramMetadata::GetKernelCapabilities() const {
+    return aci_kernel_capabilities;
+}
+
+void ProgramMetadata::Print() const {
+    LOG_DEBUG(Service_FS, "Magic:                  {:.4}", npdm_header.magic.data());
+    LOG_DEBUG(Service_FS, "Main thread priority:   0x{:02X}", npdm_header.main_thread_priority);
+    LOG_DEBUG(Service_FS, "Main thread core:       {}", npdm_header.main_thread_cpu);
+    LOG_DEBUG(Service_FS, "Main thread stack size: 0x{:X} bytes", npdm_header.main_stack_size);
+    LOG_DEBUG(Service_FS, "Process category:       {}", npdm_header.process_category);
+    LOG_DEBUG(Service_FS, "Flags:                  0x{:02X}", npdm_header.flags);
+    LOG_DEBUG(Service_FS, " > 64-bit instructions: {}",
+              npdm_header.has_64_bit_instructions ? "YES" : "NO");
+
+    const char* address_space = "Unknown";
+    switch (npdm_header.address_space_type) {
+    case ProgramAddressSpaceType::Is36Bit:
+        address_space = "64-bit (36-bit address space)";
+        break;
+    case ProgramAddressSpaceType::Is39Bit:
+        address_space = "64-bit (39-bit address space)";
+        break;
+    case ProgramAddressSpaceType::Is32Bit:
+        address_space = "32-bit";
+        break;
+    case ProgramAddressSpaceType::Is32BitNoMap:
+        address_space = "32-bit (no map region)";
+        break;
+    }
+
+    LOG_DEBUG(Service_FS, " > Address space:       {}\n", address_space);
+
+    // Begin ACID printing (potential perms, signed)
+    LOG_DEBUG(Service_FS, "Magic:                  {:.4}", acid_header.magic.data());
+    LOG_DEBUG(Service_FS, "Flags:                  0x{:02X}", acid_header.flags);
+    LOG_DEBUG(Service_FS, " > Is Retail:           {}", acid_header.production_flag ? "YES" : "NO");
+    LOG_DEBUG(Service_FS, "Title ID Min:           0x{:016X}", acid_header.title_id_min);
+    LOG_DEBUG(Service_FS, "Title ID Max:           0x{:016X}", acid_header.title_id_max);
+    LOG_DEBUG(Service_FS, "Filesystem Access:      0x{:016X}\n", acid_file_access.permissions);
+
+    // Begin ACI0 printing (actual perms, unsigned)
+    LOG_DEBUG(Service_FS, "Magic:                  {:.4}", aci_header.magic.data());
+    LOG_DEBUG(Service_FS, "Title ID:               0x{:016X}", aci_header.title_id);
+    LOG_DEBUG(Service_FS, "Filesystem Access:      0x{:016X}\n", aci_file_access.permissions);
+}
+} // namespace FileSys

core/fs/program_metadata.h

@@ -0,0 +1,189 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+#include <vector>
+
+#include "common/bit_field.h"
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+#include "common/swap.h"
+#include "core/file_sys/vfs/vfs_types.h"
+
+namespace Loader {
+enum class ResultStatus : u16;
+}
+
+namespace FileSys {
+
+enum class ProgramAddressSpaceType : u8 {
+    Is32Bit = 0,
+    Is36Bit = 1,
+    Is32BitNoMap = 2,
+    Is39Bit = 3,
+};
+
+enum class ProgramFilePermission : u64 {
+    MountContent = 1ULL << 0,
+    SaveDataBackup = 1ULL << 5,
+    SdCard = 1ULL << 21,
+    Calibration = 1ULL << 34,
+    Bit62 = 1ULL << 62,
+    Everything = 1ULL << 63,
+};
+
+enum class PoolPartition : u32 {
+    Application = 0,
+    Applet = 1,
+    System = 2,
+    SystemNonSecure = 3,
+};
+
+/**
+ * Helper which implements an interface to parse Program Description Metadata (NPDM)
+ * Data can either be loaded from a file path or with data and an offset into it.
+ */
+class ProgramMetadata {
+public:
+    using KernelCapabilityDescriptors = std::vector<u32>;
+
+    ProgramMetadata();
+    ~ProgramMetadata();
+
+    ProgramMetadata(const ProgramMetadata&) = default;
+    ProgramMetadata& operator=(const ProgramMetadata&) = default;
+
+    ProgramMetadata(ProgramMetadata&&) = default;
+    ProgramMetadata& operator=(ProgramMetadata&&) = default;
+
+    /// Gets a default ProgramMetadata configuration, should only be used for homebrew formats where
+    /// we do not have an NPDM file
+    static ProgramMetadata GetDefault();
+
+    Loader::ResultStatus Load(VirtualFile file);
+    Loader::ResultStatus Reload(VirtualFile file);
+
+    /// Load from parameters instead of NPDM file, used for KIP
+    void LoadManual(bool is_64_bit, ProgramAddressSpaceType address_space, s32 main_thread_prio,
+                    u32 main_thread_core, u32 main_thread_stack_size, u64 title_id,
+                    u64 filesystem_permissions, u32 system_resource_size,
+                    KernelCapabilityDescriptors capabilities);
+
+    bool Is64BitProgram() const;
+    ProgramAddressSpaceType GetAddressSpaceType() const;
+    u8 GetMainThreadPriority() const;
+    u8 GetMainThreadCore() const;
+    u32 GetMainThreadStackSize() const;
+    u64 GetTitleID() const;
+    u64 GetFilesystemPermissions() const;
+    u32 GetSystemResourceSize() const;
+    PoolPartition GetPoolPartition() const;
+    const KernelCapabilityDescriptors& GetKernelCapabilities() const;
+    const std::array<u8, 0x10>& GetName() const {
+        return npdm_header.application_name;
+    }
+
+    void Print() const;
+
+private:
+    struct Header {
+        std::array<char, 4> magic;
+        std::array<u8, 8> reserved;
+        union {
+            u8 flags;
+
+            BitField<0, 1, u8> has_64_bit_instructions;
+            BitField<1, 3, ProgramAddressSpaceType> address_space_type;
+            BitField<4, 4, u8> reserved_2;
+        };
+        u8 reserved_3;
+        u8 main_thread_priority;
+        u8 main_thread_cpu;
+        std::array<u8, 4> reserved_4;
+        u32_le system_resource_size;
+        u32_le process_category;
+        u32_le main_stack_size;
+        std::array<u8, 0x10> application_name;
+        std::array<u8, 0x40> reserved_5;
+        u32_le aci_offset;
+        u32_le aci_size;
+        u32_le acid_offset;
+        u32_le acid_size;
+    };
+
+    static_assert(sizeof(Header) == 0x80, "NPDM header structure size is wrong");
+
+    struct AcidHeader {
+        std::array<u8, 0x100> signature;
+        std::array<u8, 0x100> nca_modulus;
+        std::array<char, 4> magic;
+        u32_le nca_size;
+        std::array<u8, 0x4> reserved;
+        union {
+            u32 flags;
+
+            BitField<0, 1, u32> production_flag;
+            BitField<1, 1, u32> unqualified_approval;
+            BitField<2, 4, PoolPartition> pool_partition;
+        };
+        u64_le title_id_min;
+        u64_le title_id_max;
+        u32_le fac_offset;
+        u32_le fac_size;
+        u32_le sac_offset;
+        u32_le sac_size;
+        u32_le kac_offset;
+        u32_le kac_size;
+        INSERT_PADDING_BYTES(0x8);
+    };
+
+    static_assert(sizeof(AcidHeader) == 0x240, "ACID header structure size is wrong");
+
+    struct AciHeader {
+        std::array<char, 4> magic;
+        std::array<u8, 0xC> reserved;
+        u64_le title_id;
+        INSERT_PADDING_BYTES(0x8);
+        u32_le fah_offset;
+        u32_le fah_size;
+        u32_le sac_offset;
+        u32_le sac_size;
+        u32_le kac_offset;
+        u32_le kac_size;
+        INSERT_PADDING_BYTES(0x8);
+    };
+
+    static_assert(sizeof(AciHeader) == 0x40, "ACI0 header structure size is wrong");
+
+    // FileAccessControl and FileAccessHeader need loaded per-component: this layout does not
+    // reflect the real layout to avoid reference binding to misaligned addresses
+    struct FileAccessControl {
+        u8 version;
+        // 3 padding bytes
+        u64_le permissions;
+        std::array<u8, 0x20> unknown;
+    };
+
+    struct FileAccessHeader {
+        u8 version;
+        // 3 padding bytes
+        u64_le permissions;
+        u32_le unk_offset;
+        u32_le unk_size;
+        u32_le unk_offset_2;
+        u32_le unk_size_2;
+    };
+
+    Header npdm_header{};
+    AciHeader aci_header{};
+    AcidHeader acid_header{};
+
+    FileAccessControl acid_file_access{};
+    FileAccessHeader aci_file_access{};
+
+    KernelCapabilityDescriptors aci_kernel_capabilities{};
+};
+
+} // namespace FileSys

core/fs/registered_cache.h

@@ -0,0 +1,265 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+#include <functional>
+#include <memory>
+#include <string>
+#include <vector>
+#include <boost/container/flat_map.hpp>
+#include "common/common_types.h"
+#include "core/crypto/key_manager.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+class CNMT;
+class NCA;
+class NSP;
+class XCI;
+
+enum class ContentRecordType : u8;
+enum class NCAContentType : u8;
+enum class TitleType : u8;
+
+struct ContentRecord;
+struct CNMTHeader;
+struct MetaRecord;
+class RegisteredCache;
+
+using NcaID = std::array<u8, 0x10>;
+using ContentProviderParsingFunction = std::function<VirtualFile(const VirtualFile&, const NcaID&)>;
+using VfsCopyFunction = std::function<bool(const VirtualFile&, const VirtualFile&, size_t)>;
+
+enum class InstallResult {
+    Success,
+    OverwriteExisting,
+    ErrorAlreadyExists,
+    ErrorCopyFailed,
+    ErrorMetaFailed,
+    ErrorBaseInstall,
+};
+
+struct ContentProviderEntry {
+    u64 title_id;
+    ContentRecordType type;
+
+    std::string DebugInfo() const;
+};
+
+constexpr u64 GetUpdateTitleID(u64 base_title_id) {
+    return base_title_id | 0x800;
+}
+
+ContentRecordType GetCRTypeFromNCAType(NCAContentType type);
+
+// boost flat_map requires operator< for O(log(n)) lookups.
+bool operator<(const ContentProviderEntry& lhs, const ContentProviderEntry& rhs);
+
+// std unique requires operator== to identify duplicates.
+bool operator==(const ContentProviderEntry& lhs, const ContentProviderEntry& rhs);
+bool operator!=(const ContentProviderEntry& lhs, const ContentProviderEntry& rhs);
+
+class ContentProvider {
+public:
+    virtual ~ContentProvider();
+
+    virtual void Refresh() = 0;
+
+    virtual bool HasEntry(u64 title_id, ContentRecordType type) const = 0;
+    bool HasEntry(ContentProviderEntry entry) const;
+
+    virtual std::optional<u32> GetEntryVersion(u64 title_id) const = 0;
+
+    virtual VirtualFile GetEntryUnparsed(u64 title_id, ContentRecordType type) const = 0;
+    VirtualFile GetEntryUnparsed(ContentProviderEntry entry) const;
+
+    virtual VirtualFile GetEntryRaw(u64 title_id, ContentRecordType type) const = 0;
+    VirtualFile GetEntryRaw(ContentProviderEntry entry) const;
+
+    virtual std::unique_ptr<NCA> GetEntry(u64 title_id, ContentRecordType type) const = 0;
+    std::unique_ptr<NCA> GetEntry(ContentProviderEntry entry) const;
+
+    virtual std::vector<ContentProviderEntry> ListEntries() const;
+
+    // If a parameter is not std::nullopt, it will be filtered for from all entries.
+    virtual std::vector<ContentProviderEntry> ListEntriesFilter(
+        std::optional<TitleType> title_type = {}, std::optional<ContentRecordType> record_type = {},
+        std::optional<u64> title_id = {}) const = 0;
+
+protected:
+    // A single instance of KeyManager to be used by GetEntry()
+    Core::Crypto::KeyManager& keys = Core::Crypto::KeyManager::Instance();
+};
+
+class PlaceholderCache {
+public:
+    explicit PlaceholderCache(VirtualDir dir);
+
+    bool Create(const NcaID& id, u64 size) const;
+    bool Delete(const NcaID& id) const;
+    bool Exists(const NcaID& id) const;
+    bool Write(const NcaID& id, u64 offset, const std::vector<u8>& data) const;
+    bool Register(RegisteredCache* cache, const NcaID& placeholder, const NcaID& install) const;
+    bool CleanAll() const;
+    std::optional<std::array<u8, 0x10>> GetRightsID(const NcaID& id) const;
+    u64 Size(const NcaID& id) const;
+    bool SetSize(const NcaID& id, u64 new_size) const;
+    std::vector<NcaID> List() const;
+
+    static NcaID Generate();
+
+private:
+    VirtualDir dir;
+};
+
+/*
+ * A class that catalogues NCAs in the registered directory structure.
+ * Nintendo's registered format follows this structure:
+ *
+ * Root
+ *   | 000000XX <- XX is the ____ two digits of the NcaID
+ *       | <hash>.nca <- hash is the NcaID (first half of SHA256 over entire file) (folder)
+ *         | 00
+ *         | 01 <- Actual content split along 4GB boundaries. (optional)
+ *
+ * (This impl also supports substituting the nca dir for an nca file, as that's more convenient
+ * when 4GB splitting can be ignored.)
+ */
+class RegisteredCache : public ContentProvider {
+    friend class PlaceholderCache;
+
+public:
+    // Parsing function defines the conversion from raw file to NCA. If there are other steps
+    // besides creating the NCA from the file (e.g. NAX0 on SD Card), that should go in a custom
+    // parsing function.
+    explicit RegisteredCache(
+        VirtualDir dir, ContentProviderParsingFunction parsing_function =
+                            [](const VirtualFile& file, const NcaID& id) { return file; });
+    ~RegisteredCache() override;
+
+    void Refresh() override;
+
+    bool HasEntry(u64 title_id, ContentRecordType type) const override;
+
+    std::optional<u32> GetEntryVersion(u64 title_id) const override;
+
+    VirtualFile GetEntryUnparsed(u64 title_id, ContentRecordType type) const override;
+
+    VirtualFile GetEntryRaw(u64 title_id, ContentRecordType type) const override;
+
+    std::unique_ptr<NCA> GetEntry(u64 title_id, ContentRecordType type) const override;
+
+    // If a parameter is not std::nullopt, it will be filtered for from all entries.
+    std::vector<ContentProviderEntry> ListEntriesFilter(
+        std::optional<TitleType> title_type = {}, std::optional<ContentRecordType> record_type = {},
+        std::optional<u64> title_id = {}) const override;
+
+    // Raw copies all the ncas from the xci/nsp to the csache. Does some quick checks to make sure
+    // there is a meta NCA and all of them are accessible.
+    InstallResult InstallEntry(const XCI& xci, bool overwrite_if_exists = false,
+                               const VfsCopyFunction& copy = &VfsRawCopy);
+    InstallResult InstallEntry(const NSP& nsp, bool overwrite_if_exists = false,
+                               const VfsCopyFunction& copy = &VfsRawCopy);
+
+    // Due to the fact that we must use Meta-type NCAs to determine the existence of files, this
+    // poses quite a challenge. Instead of creating a new meta NCA for this file, yuzu will create a
+    // dir inside the NAND called 'yuzu_meta' and store the raw CNMT there.
+    // TODO(DarkLordZach): Author real meta-type NCAs and install those.
+    InstallResult InstallEntry(const NCA& nca, TitleType type, bool overwrite_if_exists = false,
+                               const VfsCopyFunction& copy = &VfsRawCopy);
+
+    InstallResult InstallEntry(const NCA& nca, const CNMTHeader& base_header,
+                               const ContentRecord& base_record, bool overwrite_if_exists = false,
+                               const VfsCopyFunction& copy = &VfsRawCopy);
+
+    // Removes an existing entry based on title id
+    bool RemoveExistingEntry(u64 title_id) const;
+
+private:
+    template <typename T>
+    void IterateAllMetadata(std::vector<T>& out,
+                            std::function<T(const CNMT&, const ContentRecord&)> proc,
+                            std::function<bool(const CNMT&, const ContentRecord&)> filter) const;
+    std::vector<NcaID> AccumulateFiles() const;
+    void ProcessFiles(const std::vector<NcaID>& ids);
+    void AccumulateYuzuMeta();
+    std::optional<NcaID> GetNcaIDFromMetadata(u64 title_id, ContentRecordType type) const;
+    VirtualFile GetFileAtID(NcaID id) const;
+    VirtualFile OpenFileOrDirectoryConcat(const VirtualDir& open_dir, std::string_view path) const;
+    InstallResult RawInstallNCA(const NCA& nca, const VfsCopyFunction& copy,
+                                bool overwrite_if_exists, std::optional<NcaID> override_id = {});
+    bool RawInstallYuzuMeta(const CNMT& cnmt);
+
+    VirtualDir dir;
+    ContentProviderParsingFunction parser;
+
+    // maps tid -> NcaID of meta
+    std::map<u64, NcaID> meta_id;
+    // maps tid -> meta
+    std::map<u64, CNMT> meta;
+    // maps tid -> meta for CNMT in yuzu_meta
+    std::map<u64, CNMT> yuzu_meta;
+};
+
+enum class ContentProviderUnionSlot {
+    SysNAND,        ///< System NAND
+    UserNAND,       ///< User NAND
+    SDMC,           ///< SD Card
+    FrontendManual, ///< Frontend-defined game list or similar
+};
+
+// Combines multiple ContentProvider(s) (i.e. SysNAND, UserNAND, SDMC) into one interface.
+class ContentProviderUnion : public ContentProvider {
+public:
+    ~ContentProviderUnion() override;
+
+    void SetSlot(ContentProviderUnionSlot slot, ContentProvider* provider);
+    void ClearSlot(ContentProviderUnionSlot slot);
+
+    void Refresh() override;
+    bool HasEntry(u64 title_id, ContentRecordType type) const override;
+    std::optional<u32> GetEntryVersion(u64 title_id) const override;
+    VirtualFile GetEntryUnparsed(u64 title_id, ContentRecordType type) const override;
+    VirtualFile GetEntryRaw(u64 title_id, ContentRecordType type) const override;
+    std::unique_ptr<NCA> GetEntry(u64 title_id, ContentRecordType type) const override;
+    std::vector<ContentProviderEntry> ListEntriesFilter(
+        std::optional<TitleType> title_type, std::optional<ContentRecordType> record_type,
+        std::optional<u64> title_id) const override;
+
+    std::vector<std::pair<ContentProviderUnionSlot, ContentProviderEntry>> ListEntriesFilterOrigin(
+        std::optional<ContentProviderUnionSlot> origin = {},
+        std::optional<TitleType> title_type = {}, std::optional<ContentRecordType> record_type = {},
+        std::optional<u64> title_id = {}) const;
+
+    std::optional<ContentProviderUnionSlot> GetSlotForEntry(u64 title_id,
+                                                            ContentRecordType type) const;
+
+private:
+    std::map<ContentProviderUnionSlot, ContentProvider*> providers;
+};
+
+class ManualContentProvider : public ContentProvider {
+public:
+    ~ManualContentProvider() override;
+
+    void AddEntry(TitleType title_type, ContentRecordType content_type, u64 title_id,
+                  VirtualFile file);
+    void ClearAllEntries();
+
+    void Refresh() override;
+    bool HasEntry(u64 title_id, ContentRecordType type) const override;
+    std::optional<u32> GetEntryVersion(u64 title_id) const override;
+    VirtualFile GetEntryUnparsed(u64 title_id, ContentRecordType type) const override;
+    VirtualFile GetEntryRaw(u64 title_id, ContentRecordType type) const override;
+    std::unique_ptr<NCA> GetEntry(u64 title_id, ContentRecordType type) const override;
+    std::vector<ContentProviderEntry> ListEntriesFilter(
+        std::optional<TitleType> title_type, std::optional<ContentRecordType> record_type,
+        std::optional<u64> title_id) const override;
+
+private:
+    std::map<std::tuple<TitleType, ContentRecordType, u64>, VirtualFile> entries;
+};
+
+} // namespace FileSys

core/fs/romfs.cpp

@@ -0,0 +1,167 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <memory>
+
+#include "common/assert.h"
+#include "common/common_types.h"
+#include "common/string_util.h"
+#include "common/swap.h"
+#include "core/file_sys/fsmitm_romfsbuild.h"
+#include "core/file_sys/romfs.h"
+#include "core/file_sys/vfs/vfs.h"
+#include "core/file_sys/vfs/vfs_cached.h"
+#include "core/file_sys/vfs/vfs_concat.h"
+#include "core/file_sys/vfs/vfs_offset.h"
+#include "core/file_sys/vfs/vfs_vector.h"
+
+namespace FileSys {
+namespace {
+constexpr u32 ROMFS_ENTRY_EMPTY = 0xFFFFFFFF;
+
+struct TableLocation {
+    u64_le offset;
+    u64_le size;
+};
+static_assert(sizeof(TableLocation) == 0x10, "TableLocation has incorrect size.");
+
+struct RomFSHeader {
+    u64_le header_size;
+    TableLocation directory_hash;
+    TableLocation directory_meta;
+    TableLocation file_hash;
+    TableLocation file_meta;
+    u64_le data_offset;
+};
+static_assert(sizeof(RomFSHeader) == 0x50, "RomFSHeader has incorrect size.");
+
+struct DirectoryEntry {
+    u32_le parent;
+    u32_le sibling;
+    u32_le child_dir;
+    u32_le child_file;
+    u32_le hash;
+    u32_le name_length;
+};
+static_assert(sizeof(DirectoryEntry) == 0x18, "DirectoryEntry has incorrect size.");
+
+struct FileEntry {
+    u32_le parent;
+    u32_le sibling;
+    u64_le offset;
+    u64_le size;
+    u32_le hash;
+    u32_le name_length;
+};
+static_assert(sizeof(FileEntry) == 0x20, "FileEntry has incorrect size.");
+
+struct RomFSTraversalContext {
+    RomFSHeader header;
+    VirtualFile file;
+    std::vector<u8> directory_meta;
+    std::vector<u8> file_meta;
+};
+
+template <typename EntryType, auto Member>
+std::pair<EntryType, std::string> GetEntry(const RomFSTraversalContext& ctx, size_t offset) {
+    const size_t entry_end = offset + sizeof(EntryType);
+    const std::vector<u8>& vec = ctx.*Member;
+    const size_t size = vec.size();
+    const u8* data = vec.data();
+    EntryType entry{};
+
+    if (entry_end > size) {
+        return {};
+    }
+    std::memcpy(&entry, data + offset, sizeof(EntryType));
+
+    const size_t name_length = std::min(entry_end + entry.name_length, size) - entry_end;
+    std::string name(reinterpret_cast<const char*>(data + entry_end), name_length);
+
+    return {entry, std::move(name)};
+}
+
+std::pair<DirectoryEntry, std::string> GetDirectoryEntry(const RomFSTraversalContext& ctx,
+                                                         size_t directory_offset) {
+    return GetEntry<DirectoryEntry, &RomFSTraversalContext::directory_meta>(ctx, directory_offset);
+}
+
+std::pair<FileEntry, std::string> GetFileEntry(const RomFSTraversalContext& ctx,
+                                               size_t file_offset) {
+    return GetEntry<FileEntry, &RomFSTraversalContext::file_meta>(ctx, file_offset);
+}
+
+void ProcessFile(const RomFSTraversalContext& ctx, u32 this_file_offset,
+                 std::shared_ptr<VectorVfsDirectory>& parent) {
+    while (this_file_offset != ROMFS_ENTRY_EMPTY) {
+        auto entry = GetFileEntry(ctx, this_file_offset);
+
+        parent->AddFile(std::make_shared<OffsetVfsFile>(ctx.file, entry.first.size,
+                                                        entry.first.offset + ctx.header.data_offset,
+                                                        std::move(entry.second)));
+
+        this_file_offset = entry.first.sibling;
+    }
+}
+
+void ProcessDirectory(const RomFSTraversalContext& ctx, u32 this_dir_offset,
+                      std::shared_ptr<VectorVfsDirectory>& parent) {
+    while (this_dir_offset != ROMFS_ENTRY_EMPTY) {
+        auto entry = GetDirectoryEntry(ctx, this_dir_offset);
+        auto current = std::make_shared<VectorVfsDirectory>(
+            std::vector<VirtualFile>{}, std::vector<VirtualDir>{}, entry.second);
+
+        if (entry.first.child_file != ROMFS_ENTRY_EMPTY) {
+            ProcessFile(ctx, entry.first.child_file, current);
+        }
+
+        if (entry.first.child_dir != ROMFS_ENTRY_EMPTY) {
+            ProcessDirectory(ctx, entry.first.child_dir, current);
+        }
+
+        parent->AddDirectory(current);
+        this_dir_offset = entry.first.sibling;
+    }
+}
+} // Anonymous namespace
+
+VirtualDir ExtractRomFS(VirtualFile file) {
+    auto root_container = std::make_shared<VectorVfsDirectory>();
+    if (!file) {
+        return root_container;
+    }
+
+    RomFSTraversalContext ctx{};
+
+    if (file->ReadObject(&ctx.header) != sizeof(RomFSHeader)) {
+        return nullptr;
+    }
+
+    if (ctx.header.header_size != sizeof(RomFSHeader)) {
+        return nullptr;
+    }
+
+    ctx.file = file;
+    ctx.directory_meta =
+        file->ReadBytes(ctx.header.directory_meta.size, ctx.header.directory_meta.offset);
+    ctx.file_meta = file->ReadBytes(ctx.header.file_meta.size, ctx.header.file_meta.offset);
+
+    ProcessDirectory(ctx, 0, root_container);
+
+    if (auto root = root_container->GetSubdirectory(""); root) {
+        return root;
+    }
+
+    ASSERT(false);
+    return nullptr;
+}
+
+VirtualFile CreateRomFS(VirtualDir dir, VirtualDir ext) {
+    if (dir == nullptr)
+        return nullptr;
+
+    RomFSBuildContext ctx{dir, ext};
+    return ConcatenatedVfsFile::MakeConcatenatedFile(0, dir->GetName(), ctx.Build());
+}
+
+} // namespace FileSys

core/fs/romfs.h

@@ -0,0 +1,18 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+
+// Converts a RomFS binary blob to VFS Filesystem
+// Returns nullptr on failure
+VirtualDir ExtractRomFS(VirtualFile file);
+
+// Converts a VFS filesystem into a RomFS binary
+// Returns nullptr on failure
+VirtualFile CreateRomFS(VirtualDir dir, VirtualDir ext = nullptr);
+
+} // namespace FileSys

core/fs/romfs_factory.cpp

@@ -0,0 +1,96 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <memory>
+#include "common/assert.h"
+#include "common/common_types.h"
+#include "common/logging/log.h"
+#include "core/file_sys/common_funcs.h"
+#include "core/file_sys/content_archive.h"
+#include "core/file_sys/nca_metadata.h"
+#include "core/file_sys/patch_manager.h"
+#include "core/file_sys/registered_cache.h"
+#include "core/file_sys/romfs_factory.h"
+#include "core/hle/kernel/k_process.h"
+#include "core/hle/service/filesystem/filesystem.h"
+#include "core/loader/loader.h"
+
+namespace FileSys {
+
+RomFSFactory::RomFSFactory(Loader::AppLoader& app_loader, ContentProvider& provider,
+                           Service::FileSystem::FileSystemController& controller)
+    : content_provider{provider}, filesystem_controller{controller} {
+    // Load the RomFS from the app
+    if (app_loader.ReadRomFS(file) != Loader::ResultStatus::Success) {
+        LOG_WARNING(Service_FS, "Unable to read base RomFS");
+    }
+
+    updatable = app_loader.IsRomFSUpdatable();
+}
+
+RomFSFactory::~RomFSFactory() = default;
+
+void RomFSFactory::SetPackedUpdate(VirtualFile update_raw_file) {
+    packed_update_raw = std::move(update_raw_file);
+}
+
+VirtualFile RomFSFactory::OpenCurrentProcess(u64 current_process_title_id) const {
+    if (!updatable) {
+        return file;
+    }
+
+    const auto type = ContentRecordType::Program;
+    const auto nca = content_provider.GetEntry(current_process_title_id, type);
+    const PatchManager patch_manager{current_process_title_id, filesystem_controller,
+                                     content_provider};
+    return patch_manager.PatchRomFS(nca.get(), file, ContentRecordType::Program, packed_update_raw);
+}
+
+VirtualFile RomFSFactory::OpenPatchedRomFS(u64 title_id, ContentRecordType type) const {
+    auto nca = content_provider.GetEntry(title_id, type);
+
+    if (nca == nullptr) {
+        return nullptr;
+    }
+
+    const PatchManager patch_manager{title_id, filesystem_controller, content_provider};
+
+    return patch_manager.PatchRomFS(nca.get(), nca->GetRomFS(), type);
+}
+
+VirtualFile RomFSFactory::OpenPatchedRomFSWithProgramIndex(u64 title_id, u8 program_index,
+                                                           ContentRecordType type) const {
+    const auto res_title_id = GetBaseTitleIDWithProgramIndex(title_id, program_index);
+
+    return OpenPatchedRomFS(res_title_id, type);
+}
+
+VirtualFile RomFSFactory::Open(u64 title_id, StorageId storage, ContentRecordType type) const {
+    const std::shared_ptr<NCA> res = GetEntry(title_id, storage, type);
+    if (res == nullptr) {
+        return nullptr;
+    }
+
+    return res->GetRomFS();
+}
+
+std::shared_ptr<NCA> RomFSFactory::GetEntry(u64 title_id, StorageId storage,
+                                            ContentRecordType type) const {
+    switch (storage) {
+    case StorageId::None:
+        return content_provider.GetEntry(title_id, type);
+    case StorageId::NandSystem:
+        return filesystem_controller.GetSystemNANDContents()->GetEntry(title_id, type);
+    case StorageId::NandUser:
+        return filesystem_controller.GetUserNANDContents()->GetEntry(title_id, type);
+    case StorageId::SdCard:
+        return filesystem_controller.GetSDMCContents()->GetEntry(title_id, type);
+    case StorageId::Host:
+    case StorageId::GameCard:
+    default:
+        UNIMPLEMENTED_MSG("Unimplemented storage_id={:02X}", static_cast<u8>(storage));
+        return nullptr;
+    }
+}
+
+} // namespace FileSys

core/fs/romfs_factory.h

@@ -0,0 +1,64 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <memory>
+
+#include "common/common_types.h"
+#include "core/file_sys/vfs/vfs_types.h"
+#include "core/hle/result.h"
+
+namespace Loader {
+class AppLoader;
+} // namespace Loader
+
+namespace Service::FileSystem {
+class FileSystemController;
+}
+
+namespace FileSys {
+
+class ContentProvider;
+class NCA;
+
+enum class ContentRecordType : u8;
+
+enum class StorageId : u8 {
+    None = 0,
+    Host = 1,
+    GameCard = 2,
+    NandSystem = 3,
+    NandUser = 4,
+    SdCard = 5,
+};
+
+/// File system interface to the RomFS archive
+class RomFSFactory {
+public:
+    explicit RomFSFactory(Loader::AppLoader& app_loader, ContentProvider& provider,
+                          Service::FileSystem::FileSystemController& controller);
+    ~RomFSFactory();
+
+    void SetPackedUpdate(VirtualFile packed_update_raw);
+    [[nodiscard]] VirtualFile OpenCurrentProcess(u64 current_process_title_id) const;
+    [[nodiscard]] VirtualFile OpenPatchedRomFS(u64 title_id, ContentRecordType type) const;
+    [[nodiscard]] VirtualFile OpenPatchedRomFSWithProgramIndex(u64 title_id, u8 program_index,
+                                                               ContentRecordType type) const;
+    [[nodiscard]] VirtualFile Open(u64 title_id, StorageId storage, ContentRecordType type) const;
+    [[nodiscard]] std::shared_ptr<NCA> GetEntry(u64 title_id, StorageId storage,
+                                                ContentRecordType type) const;
+
+private:
+    VirtualFile file;
+    VirtualFile packed_update_raw;
+
+    VirtualFile base;
+
+    bool updatable;
+
+    ContentProvider& content_provider;
+    Service::FileSystem::FileSystemController& filesystem_controller;
+};
+
+} // namespace FileSys

core/fs/savedata_factory.cpp

@@ -0,0 +1,194 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <memory>
+#include "common/assert.h"
+#include "common/common_types.h"
+#include "common/logging/log.h"
+#include "common/uuid.h"
+#include "core/core.h"
+#include "core/file_sys/savedata_factory.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace FileSys {
+
+namespace {
+
+bool ShouldSaveDataBeAutomaticallyCreated(SaveDataSpaceId space, const SaveDataAttribute& attr) {
+    return attr.type == SaveDataType::Cache || attr.type == SaveDataType::Temporary ||
+           (space == SaveDataSpaceId::User && ///< Normal Save Data -- Current Title & User
+            (attr.type == SaveDataType::Account || attr.type == SaveDataType::Device) &&
+            attr.program_id == 0 && attr.system_save_data_id == 0);
+}
+
+std::string GetFutureSaveDataPath(SaveDataSpaceId space_id, SaveDataType type, u64 title_id,
+                                  u128 user_id) {
+    // Only detect nand user saves.
+    const auto space_id_path = [space_id]() -> std::string_view {
+        switch (space_id) {
+        case SaveDataSpaceId::User:
+            return "/user/save";
+        default:
+            return "";
+        }
+    }();
+
+    if (space_id_path.empty()) {
+        return "";
+    }
+
+    Common::UUID uuid;
+    std::memcpy(uuid.uuid.data(), user_id.data(), sizeof(Common::UUID));
+
+    // Only detect account/device saves from the future location.
+    switch (type) {
+    case SaveDataType::Account:
+        return fmt::format("{}/account/{}/{:016X}/0", space_id_path, uuid.RawString(), title_id);
+    case SaveDataType::Device:
+        return fmt::format("{}/device/{:016X}/0", space_id_path, title_id);
+    default:
+        return "";
+    }
+}
+
+} // Anonymous namespace
+
+SaveDataFactory::SaveDataFactory(Core::System& system_, ProgramId program_id_,
+                                 VirtualDir save_directory_)
+    : system{system_}, program_id{program_id_}, dir{std::move(save_directory_)} {
+    // Delete all temporary storages
+    // On hardware, it is expected that temporary storage be empty at first use.
+    dir->DeleteSubdirectoryRecursive("temp");
+}
+
+SaveDataFactory::~SaveDataFactory() = default;
+
+VirtualDir SaveDataFactory::Create(SaveDataSpaceId space, const SaveDataAttribute& meta) const {
+    const auto save_directory = GetFullPath(program_id, dir, space, meta.type, meta.program_id,
+                                            meta.user_id, meta.system_save_data_id);
+
+    return dir->CreateDirectoryRelative(save_directory);
+}
+
+VirtualDir SaveDataFactory::Open(SaveDataSpaceId space, const SaveDataAttribute& meta) const {
+
+    const auto save_directory = GetFullPath(program_id, dir, space, meta.type, meta.program_id,
+                                            meta.user_id, meta.system_save_data_id);
+
+    auto out = dir->GetDirectoryRelative(save_directory);
+
+    if (out == nullptr && (ShouldSaveDataBeAutomaticallyCreated(space, meta) && auto_create)) {
+        return Create(space, meta);
+    }
+
+    return out;
+}
+
+VirtualDir SaveDataFactory::GetSaveDataSpaceDirectory(SaveDataSpaceId space) const {
+    return dir->GetDirectoryRelative(GetSaveDataSpaceIdPath(space));
+}
+
+std::string SaveDataFactory::GetSaveDataSpaceIdPath(SaveDataSpaceId space) {
+    switch (space) {
+    case SaveDataSpaceId::System:
+        return "/system/";
+    case SaveDataSpaceId::User:
+        return "/user/";
+    case SaveDataSpaceId::Temporary:
+        return "/temp/";
+    default:
+        ASSERT_MSG(false, "Unrecognized SaveDataSpaceId: {:02X}", static_cast<u8>(space));
+        return "/unrecognized/"; ///< To prevent corruption when ignoring asserts.
+    }
+}
+
+std::string SaveDataFactory::GetFullPath(ProgramId program_id, VirtualDir dir,
+                                         SaveDataSpaceId space, SaveDataType type, u64 title_id,
+                                         u128 user_id, u64 save_id) {
+    // According to switchbrew, if a save is of type SaveData and the title id field is 0, it should
+    // be interpreted as the title id of the current process.
+    if (type == SaveDataType::Account || type == SaveDataType::Device) {
+        if (title_id == 0) {
+            title_id = program_id;
+        }
+    }
+
+    // For compat with a future impl.
+    if (std::string future_path =
+            GetFutureSaveDataPath(space, type, title_id & ~(0xFFULL), user_id);
+        !future_path.empty()) {
+        // Check if this location exists, and prefer it over the old.
+        if (const auto future_dir = dir->GetDirectoryRelative(future_path); future_dir != nullptr) {
+            LOG_INFO(Service_FS, "Using save at new location: {}", future_path);
+            return future_path;
+        }
+    }
+
+    std::string out = GetSaveDataSpaceIdPath(space);
+
+    switch (type) {
+    case SaveDataType::System:
+        return fmt::format("{}save/{:016X}/{:016X}{:016X}", out, save_id, user_id[1], user_id[0]);
+    case SaveDataType::Account:
+    case SaveDataType::Device:
+        return fmt::format("{}save/{:016X}/{:016X}{:016X}/{:016X}", out, 0, user_id[1], user_id[0],
+                           title_id);
+    case SaveDataType::Temporary:
+        return fmt::format("{}{:016X}/{:016X}{:016X}/{:016X}", out, 0, user_id[1], user_id[0],
+                           title_id);
+    case SaveDataType::Cache:
+        return fmt::format("{}save/cache/{:016X}", out, title_id);
+    default:
+        ASSERT_MSG(false, "Unrecognized SaveDataType: {:02X}", static_cast<u8>(type));
+        return fmt::format("{}save/unknown_{:X}/{:016X}", out, static_cast<u8>(type), title_id);
+    }
+}
+
+std::string SaveDataFactory::GetUserGameSaveDataRoot(u128 user_id, bool future) {
+    if (future) {
+        Common::UUID uuid;
+        std::memcpy(uuid.uuid.data(), user_id.data(), sizeof(Common::UUID));
+        return fmt::format("/user/save/account/{}", uuid.RawString());
+    }
+    return fmt::format("/user/save/{:016X}/{:016X}{:016X}", 0, user_id[1], user_id[0]);
+}
+
+SaveDataSize SaveDataFactory::ReadSaveDataSize(SaveDataType type, u64 title_id,
+                                               u128 user_id) const {
+    const auto path =
+        GetFullPath(program_id, dir, SaveDataSpaceId::User, type, title_id, user_id, 0);
+    const auto relative_dir = GetOrCreateDirectoryRelative(dir, path);
+
+    const auto size_file = relative_dir->GetFile(GetSaveDataSizeFileName());
+    if (size_file == nullptr || size_file->GetSize() < sizeof(SaveDataSize)) {
+        return {0, 0};
+    }
+
+    SaveDataSize out;
+    if (size_file->ReadObject(&out) != sizeof(SaveDataSize)) {
+        return {0, 0};
+    }
+
+    return out;
+}
+
+void SaveDataFactory::WriteSaveDataSize(SaveDataType type, u64 title_id, u128 user_id,
+                                        SaveDataSize new_value) const {
+    const auto path =
+        GetFullPath(program_id, dir, SaveDataSpaceId::User, type, title_id, user_id, 0);
+    const auto relative_dir = GetOrCreateDirectoryRelative(dir, path);
+
+    const auto size_file = relative_dir->CreateFile(GetSaveDataSizeFileName());
+    if (size_file == nullptr) {
+        return;
+    }
+
+    size_file->Resize(sizeof(SaveDataSize));
+    size_file->WriteObject(new_value);
+}
+
+void SaveDataFactory::SetAutoCreate(bool state) {
+    auto_create = state;
+}
+
+} // namespace FileSys

core/fs/savedata_factory.h

@@ -0,0 +1,56 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <memory>
+#include <string>
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+#include "core/file_sys/fs_save_data_types.h"
+#include "core/file_sys/vfs/vfs.h"
+#include "core/hle/result.h"
+
+namespace Core {
+class System;
+}
+
+namespace FileSys {
+
+constexpr const char* GetSaveDataSizeFileName() {
+    return ".yuzu_save_size";
+}
+
+using ProgramId = u64;
+
+/// File system interface to the SaveData archive
+class SaveDataFactory {
+public:
+    explicit SaveDataFactory(Core::System& system_, ProgramId program_id_,
+                             VirtualDir save_directory_);
+    ~SaveDataFactory();
+
+    VirtualDir Create(SaveDataSpaceId space, const SaveDataAttribute& meta) const;
+    VirtualDir Open(SaveDataSpaceId space, const SaveDataAttribute& meta) const;
+
+    VirtualDir GetSaveDataSpaceDirectory(SaveDataSpaceId space) const;
+
+    static std::string GetSaveDataSpaceIdPath(SaveDataSpaceId space);
+    static std::string GetFullPath(ProgramId program_id, VirtualDir dir, SaveDataSpaceId space,
+                                   SaveDataType type, u64 title_id, u128 user_id, u64 save_id);
+    static std::string GetUserGameSaveDataRoot(u128 user_id, bool future);
+
+    SaveDataSize ReadSaveDataSize(SaveDataType type, u64 title_id, u128 user_id) const;
+    void WriteSaveDataSize(SaveDataType type, u64 title_id, u128 user_id,
+                           SaveDataSize new_value) const;
+
+    void SetAutoCreate(bool state);
+
+private:
+    Core::System& system;
+    ProgramId program_id;
+    VirtualDir dir;
+    bool auto_create{true};
+};
+
+} // namespace FileSys

core/fs/sdmc_factory.cpp

@@ -0,0 +1,62 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <memory>
+#include "core/file_sys/registered_cache.h"
+#include "core/file_sys/sdmc_factory.h"
+#include "core/file_sys/vfs/vfs.h"
+#include "core/file_sys/xts_archive.h"
+
+namespace FileSys {
+
+constexpr u64 SDMC_TOTAL_SIZE = 0x10000000000; // 1 TiB
+
+SDMCFactory::SDMCFactory(VirtualDir sd_dir_, VirtualDir sd_mod_dir_)
+    : sd_dir(std::move(sd_dir_)), sd_mod_dir(std::move(sd_mod_dir_)),
+      contents(std::make_unique<RegisteredCache>(
+          GetOrCreateDirectoryRelative(sd_dir, "/Nintendo/Contents/registered"),
+          [](const VirtualFile& file, const NcaID& id) {
+              return NAX{file, id}.GetDecrypted();
+          })),
+      placeholder(std::make_unique<PlaceholderCache>(
+          GetOrCreateDirectoryRelative(sd_dir, "/Nintendo/Contents/placehld"))) {}
+
+SDMCFactory::~SDMCFactory() = default;
+
+VirtualDir SDMCFactory::Open() const {
+    return sd_dir;
+}
+
+VirtualDir SDMCFactory::GetSDMCModificationLoadRoot(u64 title_id) const {
+    // LayeredFS doesn't work on updates and title id-less homebrew
+    if (title_id == 0 || (title_id & 0xFFF) == 0x800) {
+        return nullptr;
+    }
+    return GetOrCreateDirectoryRelative(sd_mod_dir, fmt::format("/{:016X}", title_id));
+}
+
+VirtualDir SDMCFactory::GetSDMCContentDirectory() const {
+    return GetOrCreateDirectoryRelative(sd_dir, "/Nintendo/Contents");
+}
+
+RegisteredCache* SDMCFactory::GetSDMCContents() const {
+    return contents.get();
+}
+
+PlaceholderCache* SDMCFactory::GetSDMCPlaceholder() const {
+    return placeholder.get();
+}
+
+VirtualDir SDMCFactory::GetImageDirectory() const {
+    return GetOrCreateDirectoryRelative(sd_dir, "/Nintendo/Album");
+}
+
+u64 SDMCFactory::GetSDMCFreeSpace() const {
+    return GetSDMCTotalSpace() - sd_dir->GetSize();
+}
+
+u64 SDMCFactory::GetSDMCTotalSpace() const {
+    return SDMC_TOTAL_SIZE;
+}
+
+} // namespace FileSys

core/fs/sdmc_factory.h

@@ -0,0 +1,42 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <memory>
+#include "core/file_sys/vfs/vfs_types.h"
+#include "core/hle/result.h"
+
+namespace FileSys {
+
+class RegisteredCache;
+class PlaceholderCache;
+
+/// File system interface to the SDCard archive
+class SDMCFactory {
+public:
+    explicit SDMCFactory(VirtualDir sd_dir_, VirtualDir sd_mod_dir_);
+    ~SDMCFactory();
+
+    VirtualDir Open() const;
+
+    VirtualDir GetSDMCModificationLoadRoot(u64 title_id) const;
+    VirtualDir GetSDMCContentDirectory() const;
+
+    RegisteredCache* GetSDMCContents() const;
+    PlaceholderCache* GetSDMCPlaceholder() const;
+
+    VirtualDir GetImageDirectory() const;
+
+    u64 GetSDMCFreeSpace() const;
+    u64 GetSDMCTotalSpace() const;
+
+private:
+    VirtualDir sd_dir;
+    VirtualDir sd_mod_dir;
+
+    std::unique_ptr<RegisteredCache> contents;
+    std::unique_ptr<PlaceholderCache> placeholder;
+};
+
+} // namespace FileSys

core/fs/submission_package.cpp

@@ -0,0 +1,289 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <algorithm>
+#include <cstring>
+
+#include <fmt/ostream.h>
+
+#include "common/hex_util.h"
+#include "common/logging/log.h"
+#include "core/crypto/key_manager.h"
+#include "core/file_sys/content_archive.h"
+#include "core/file_sys/nca_metadata.h"
+#include "core/file_sys/partition_filesystem.h"
+#include "core/file_sys/program_metadata.h"
+#include "core/file_sys/submission_package.h"
+#include "core/loader/loader.h"
+
+namespace FileSys {
+
+NSP::NSP(VirtualFile file_, u64 title_id_, std::size_t program_index_)
+    : file(std::move(file_)), expected_program_id(title_id_),
+      program_index(program_index_), status{Loader::ResultStatus::Success},
+      pfs(std::make_shared<PartitionFilesystem>(file)), keys{Core::Crypto::KeyManager::Instance()} {
+    if (pfs->GetStatus() != Loader::ResultStatus::Success) {
+        status = pfs->GetStatus();
+        return;
+    }
+
+    const auto files = pfs->GetFiles();
+
+    if (IsDirectoryExeFS(pfs)) {
+        extracted = true;
+        InitializeExeFSAndRomFS(files);
+        return;
+    }
+
+    SetTicketKeys(files);
+    ReadNCAs(files);
+}
+
+NSP::~NSP() = default;
+
+Loader::ResultStatus NSP::GetStatus() const {
+    return status;
+}
+
+Loader::ResultStatus NSP::GetProgramStatus() const {
+    if (IsExtractedType() && GetExeFS() != nullptr && FileSys::IsDirectoryExeFS(GetExeFS())) {
+        return Loader::ResultStatus::Success;
+    }
+
+    const auto iter = program_status.find(GetProgramTitleID());
+    if (iter == program_status.end())
+        return Loader::ResultStatus::ErrorNSPMissingProgramNCA;
+    return iter->second;
+}
+
+u64 NSP::GetProgramTitleID() const {
+    if (IsExtractedType()) {
+        return GetExtractedTitleID() + program_index;
+    }
+
+    auto program_id = expected_program_id;
+    if (program_id == 0) {
+        if (!program_status.empty()) {
+            program_id = program_status.begin()->first;
+        }
+    }
+
+    program_id = program_id + program_index;
+    if (program_status.find(program_id) != program_status.end()) {
+        return program_id;
+    }
+
+    const auto ids = GetProgramTitleIDs();
+    const auto iter =
+        std::find_if(ids.begin(), ids.end(), [](u64 tid) { return (tid & 0x800) == 0; });
+    return iter == ids.end() ? 0 : *iter;
+}
+
+u64 NSP::GetExtractedTitleID() const {
+    if (GetExeFS() == nullptr || !IsDirectoryExeFS(GetExeFS())) {
+        return 0;
+    }
+
+    ProgramMetadata meta;
+    if (meta.Load(GetExeFS()->GetFile("main.npdm")) == Loader::ResultStatus::Success) {
+        return meta.GetTitleID();
+    } else {
+        return 0;
+    }
+}
+
+std::vector<u64> NSP::GetProgramTitleIDs() const {
+    if (IsExtractedType()) {
+        return {GetExtractedTitleID()};
+    }
+
+    std::vector<u64> out{program_ids.cbegin(), program_ids.cend()};
+    return out;
+}
+
+bool NSP::IsExtractedType() const {
+    return extracted;
+}
+
+VirtualFile NSP::GetRomFS() const {
+    return romfs;
+}
+
+VirtualDir NSP::GetExeFS() const {
+    return exefs;
+}
+
+std::vector<std::shared_ptr<NCA>> NSP::GetNCAsCollapsed() const {
+    if (extracted)
+        LOG_WARNING(Service_FS, "called on an NSP that is of type extracted.");
+    std::vector<std::shared_ptr<NCA>> out;
+    for (const auto& map : ncas) {
+        for (const auto& inner_map : map.second)
+            out.push_back(inner_map.second);
+    }
+    return out;
+}
+
+std::multimap<u64, std::shared_ptr<NCA>> NSP::GetNCAsByTitleID() const {
+    if (extracted)
+        LOG_WARNING(Service_FS, "called on an NSP that is of type extracted.");
+    std::multimap<u64, std::shared_ptr<NCA>> out;
+    for (const auto& map : ncas) {
+        for (const auto& inner_map : map.second)
+            out.emplace(map.first, inner_map.second);
+    }
+    return out;
+}
+
+std::map<u64, std::map<std::pair<TitleType, ContentRecordType>, std::shared_ptr<NCA>>>
+NSP::GetNCAs() const {
+    return ncas;
+}
+
+std::shared_ptr<NCA> NSP::GetNCA(u64 title_id, ContentRecordType type, TitleType title_type) const {
+    if (extracted)
+        LOG_WARNING(Service_FS, "called on an NSP that is of type extracted.");
+
+    const auto title_id_iter = ncas.find(title_id);
+    if (title_id_iter == ncas.end())
+        return nullptr;
+
+    const auto type_iter = title_id_iter->second.find({title_type, type});
+    if (type_iter == title_id_iter->second.end())
+        return nullptr;
+
+    return type_iter->second;
+}
+
+VirtualFile NSP::GetNCAFile(u64 title_id, ContentRecordType type, TitleType title_type) const {
+    if (extracted)
+        LOG_WARNING(Service_FS, "called on an NSP that is of type extracted.");
+    const auto nca = GetNCA(title_id, type, title_type);
+    if (nca != nullptr)
+        return nca->GetBaseFile();
+    return nullptr;
+}
+
+std::vector<VirtualFile> NSP::GetFiles() const {
+    return pfs->GetFiles();
+}
+
+std::vector<VirtualDir> NSP::GetSubdirectories() const {
+    return pfs->GetSubdirectories();
+}
+
+std::string NSP::GetName() const {
+    return file->GetName();
+}
+
+VirtualDir NSP::GetParentDirectory() const {
+    return file->GetContainingDirectory();
+}
+
+void NSP::SetTicketKeys(const std::vector<VirtualFile>& files) {
+    for (const auto& ticket_file : files) {
+        if (ticket_file == nullptr) {
+            continue;
+        }
+
+        if (ticket_file->GetExtension() != "tik") {
+            continue;
+        }
+
+        auto ticket = Core::Crypto::Ticket::Read(ticket_file);
+        if (!keys.AddTicket(ticket)) {
+            LOG_WARNING(Common_Filesystem, "Could not load NSP ticket {}", ticket_file->GetName());
+            continue;
+        }
+    }
+}
+
+void NSP::InitializeExeFSAndRomFS(const std::vector<VirtualFile>& files) {
+    exefs = pfs;
+
+    const auto iter = std::find_if(files.begin(), files.end(), [](const VirtualFile& entry) {
+        return entry->GetName().rfind(".romfs") != std::string::npos;
+    });
+
+    if (iter == files.end()) {
+        return;
+    }
+
+    romfs = *iter;
+}
+
+void NSP::ReadNCAs(const std::vector<VirtualFile>& files) {
+    for (const auto& outer_file : files) {
+        if (outer_file->GetName().size() < 9 ||
+            outer_file->GetName().substr(outer_file->GetName().size() - 9) != ".cnmt.nca") {
+            continue;
+        }
+
+        const auto nca = std::make_shared<NCA>(outer_file);
+        if (nca->GetStatus() != Loader::ResultStatus::Success || nca->GetSubdirectories().empty()) {
+            program_status[nca->GetTitleId()] = nca->GetStatus();
+            continue;
+        }
+
+        const auto section0 = nca->GetSubdirectories()[0];
+
+        for (const auto& inner_file : section0->GetFiles()) {
+            if (inner_file->GetExtension() != "cnmt") {
+                continue;
+            }
+
+            const CNMT cnmt(inner_file);
+
+            ncas[cnmt.GetTitleID()][{cnmt.GetType(), ContentRecordType::Meta}] = nca;
+
+            for (const auto& rec : cnmt.GetContentRecords()) {
+                const auto id_string = Common::HexToString(rec.nca_id, false);
+                auto next_file = pfs->GetFile(fmt::format("{}.nca", id_string));
+
+                if (next_file == nullptr) {
+                    if (rec.type != ContentRecordType::DeltaFragment) {
+                        LOG_WARNING(Service_FS,
+                                    "NCA with ID {}.nca is listed in content metadata, but cannot "
+                                    "be found in PFS. NSP appears to be corrupted.",
+                                    id_string);
+                    }
+
+                    continue;
+                }
+
+                auto next_nca = std::make_shared<NCA>(std::move(next_file));
+
+                if (next_nca->GetType() == NCAContentType::Program) {
+                    program_status[next_nca->GetTitleId()] = next_nca->GetStatus();
+                    program_ids.insert(next_nca->GetTitleId() & 0xFFFFFFFFFFFFF000);
+                }
+
+                if (next_nca->GetStatus() != Loader::ResultStatus::Success &&
+                    next_nca->GetStatus() != Loader::ResultStatus::ErrorMissingBKTRBaseRomFS) {
+                    continue;
+                }
+
+                // If the last 3 hexadecimal digits of the CNMT TitleID is 0x800 or is missing the
+                // BKTRBaseRomFS, this is an update NCA. Otherwise, this is a base NCA.
+                if ((cnmt.GetTitleID() & 0x800) != 0 ||
+                    next_nca->GetStatus() == Loader::ResultStatus::ErrorMissingBKTRBaseRomFS) {
+                    // If the last 3 hexadecimal digits of the NCA's TitleID is between 0x1 and
+                    // 0x7FF, this is a multi-program update NCA. Otherwise, this is a regular
+                    // update NCA.
+                    if ((next_nca->GetTitleId() & 0x7FF) != 0 &&
+                        (next_nca->GetTitleId() & 0x800) == 0) {
+                        ncas[next_nca->GetTitleId()][{cnmt.GetType(), rec.type}] =
+                            std::move(next_nca);
+                    } else {
+                        ncas[cnmt.GetTitleID()][{cnmt.GetType(), rec.type}] = std::move(next_nca);
+                    }
+                } else {
+                    ncas[next_nca->GetTitleId()][{cnmt.GetType(), rec.type}] = std::move(next_nca);
+                }
+            }
+
+            break;
+        }
+    }
+}
+} // namespace FileSys

core/fs/submission_package.h

@@ -0,0 +1,90 @@
+// SPDX-FileCopyrightText: Copyright 2018 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <map>
+#include <memory>
+#include <set>
+#include <vector>
+#include "common/common_types.h"
+#include "core/file_sys/nca_metadata.h"
+#include "core/file_sys/vfs/vfs.h"
+
+namespace Core::Crypto {
+class KeyManager;
+}
+
+namespace Loader {
+enum class ResultStatus : u16;
+}
+
+namespace FileSys {
+
+class NCA;
+class PartitionFilesystem;
+
+enum class ContentRecordType : u8;
+
+class NSP : public ReadOnlyVfsDirectory {
+public:
+    explicit NSP(VirtualFile file_, u64 title_id = 0, std::size_t program_index_ = 0);
+    ~NSP() override;
+
+    Loader::ResultStatus GetStatus() const;
+    Loader::ResultStatus GetProgramStatus() const;
+    // Should only be used when one title id can be assured.
+    u64 GetProgramTitleID() const;
+    u64 GetExtractedTitleID() const;
+    std::vector<u64> GetProgramTitleIDs() const;
+
+    bool IsExtractedType() const;
+
+    // Common (Can be safely called on both types)
+    VirtualFile GetRomFS() const;
+    VirtualDir GetExeFS() const;
+
+    // Type 0 Only (Collection of NCAs + Certificate + Ticket + Meta XML)
+    std::vector<std::shared_ptr<NCA>> GetNCAsCollapsed() const;
+    std::multimap<u64, std::shared_ptr<NCA>> GetNCAsByTitleID() const;
+    std::map<u64, std::map<std::pair<TitleType, ContentRecordType>, std::shared_ptr<NCA>>> GetNCAs()
+        const;
+    std::shared_ptr<NCA> GetNCA(u64 title_id, ContentRecordType type,
+                                TitleType title_type = TitleType::Application) const;
+    VirtualFile GetNCAFile(u64 title_id, ContentRecordType type,
+                           TitleType title_type = TitleType::Application) const;
+
+    std::vector<VirtualFile> GetFiles() const override;
+
+    std::vector<VirtualDir> GetSubdirectories() const override;
+
+    std::string GetName() const override;
+
+    VirtualDir GetParentDirectory() const override;
+
+private:
+    void SetTicketKeys(const std::vector<VirtualFile>& files);
+    void InitializeExeFSAndRomFS(const std::vector<VirtualFile>& files);
+    void ReadNCAs(const std::vector<VirtualFile>& files);
+
+    VirtualFile file;
+
+    const u64 expected_program_id;
+    const std::size_t program_index;
+
+    bool extracted = false;
+    Loader::ResultStatus status;
+    std::map<u64, Loader::ResultStatus> program_status;
+
+    std::shared_ptr<PartitionFilesystem> pfs;
+    // Map title id -> {map type -> NCA}
+    std::map<u64, std::map<std::pair<TitleType, ContentRecordType>, std::shared_ptr<NCA>>> ncas;
+    std::set<u64> program_ids;
+    std::vector<VirtualFile> ticket_files;
+
+    Core::Crypto::KeyManager& keys;
+
+    VirtualFile romfs;
+    VirtualDir exefs;
+};
+} // namespace FileSys

core/fs/system_archive/data/font_chinese_simplified.h

@@ -0,0 +1,12 @@
+// SPDX-FileCopyrightText: Copyright 2019 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+
+namespace FileSys::SystemArchive::SharedFontData {
+
+extern const std::array<unsigned char, 217276> FONT_CHINESE_SIMPLIFIED;
+
+} // namespace FileSys::SystemArchive::SharedFontData

core/fs/system_archive/data/font_chinese_traditional.h

@@ -0,0 +1,12 @@
+// SPDX-FileCopyrightText: Copyright 2019 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+
+namespace FileSys::SystemArchive::SharedFontData {
+
+extern const std::array<unsigned char, 222236> FONT_CHINESE_TRADITIONAL;
+
+} // namespace FileSys::SystemArchive::SharedFontData