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d3c97317ef
I wanted a fast and predictable memory allocator before I start working on the virtual filesystem.
Functions like malloc and realloc will not be used anymore, instead, the allocator will
need to be passed as a function parameter when doing any kind of heap allocation. For example
char* create_string(Memory::Arena *allocator);
int* create_int_array(Memory::Arena *allocator, int size);
The definition MEMORY_CAPACITY in arena.h sets the amount of memory the arena can use.
The number can be increased as needed.
Signed-off-by: Ronald Caesar <github43132@proton.me>
111 lines
3.2 KiB
C++
111 lines
3.2 KiB
C++
#ifndef POUND_ARENA_H
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#define POUND_ARENA_H
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#include <cstddef>
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#include <cstdint>
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#include <cstdlib>
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namespace Memory {
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/* Defines the default size (in bytes) for memory arenas created via arena_init() */
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#define MEMORY_CAPACITY 20480 // 20 KB
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/*
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* NAME
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* Arena - Memory management structure for efficient allocation and de-allocation.
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*
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* SYNOPSIS
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* typedef struct {
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* std::size_t capacity; Total number of bytes allocated.
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* std::size_t size; The current number of bytes consumed.
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* uint8_t* data; A pointer to the base address of the allocated memory buffer.
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* } Arena;
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*
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* DESCRIPTION
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* The arena struct handles allocating and managing contiguous memory blocks.
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*
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* RATIONALE
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* A memory arena offers a safer alternative to malloc/realloc by
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* maintaining a single contiguous block eliminates heap fragmentation
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* that occurs with frequent small allocations.
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*/
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typedef struct {
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std::size_t capacity;
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std::size_t size;
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uint8_t* data;
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} Arena;
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/*
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* NAME
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* arena_init - Initialize a memory arena with default capacity.
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*
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* SYNOPSIS
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* Arena Memory::arena_init();
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*
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* DESCRIPTION
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* The function creates and returns a new memory arena instance with a
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* pre-allocated capacity. See the definition MEMORY_CAPACITY to change the
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* default capacity.
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*
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* RETURN VALUE
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* Returns a valid Arena object on success.
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*/
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extern Arena arena_init();
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/*
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* NAME
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* arena_allocate - Allocate memory from a pre-initialized arena.
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*
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* SYNOPSIS
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* const uint8_t Memory::arena_allocate(Memory::Arena* arena, std::size_t size);
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*
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* DESCRIPTION
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* The function allocates size bytes from the specified arena. It assumes
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* the arena has sufficient capacity and returns a pointer to the allocated
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* memory region.
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*
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* RETURN VALUE
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* Returns a pointer to the first byte of the allocated memory. The returned
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* pointer is valid until the arena is reset or destroyed.
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*
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* NOTES
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* Requires Arena to be initialized with arena_init() or similar.
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*/
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const uint8_t* arena_allocate(Arena* arena, std::size_t size);
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/*
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* NAME
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* arena_reset - Reset a memory arena's allocation size to zero.
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*
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* SYNOPSIS
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* void Memory::arena_reset(Memory::Arena* arena);
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*
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* DESCRIPTION
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* The function resets the allocation size of a pre-initialized Arena to zero.
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* This effectively "frees" all memory allocated from the arena without
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* deallocating the underlying buffer, allowing reuse of the capacity for
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* future allocations.
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*
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* NOTES
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* Resets arena->size to 0 while preserving arena->capacity.
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* Does not free the underlying memory buffer.
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* Useful for reusing arenas without reallocation.
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*/
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void arena_reset(Arena* arena);
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/**
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* NAME
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* arena_free - Free the memory allocated by an arena
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*
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* SYNOPSIS
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* void Memory::arena_free(Memory::Arena* arena);
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*
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* DESCRIPTION
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* The function releases the memory buffer associated with a Arena and
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* resets its capacity and size to zero. This marks the arena as invalid for
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* future allocation unless reinitialized.
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*/
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void arena_free(Memory::Arena* arena);
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} // namespace Memory
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#endif //POUND_ARENA_H
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