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137 lines
3.7 KiB
C++
137 lines
3.7 KiB
C++
// -*- C++ -*-
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//
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//=============================================================================
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/**
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* @file RW_Process_Mutex.h
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*
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* $Id: RW_Process_Mutex.h 87487 2009-11-12 07:54:39Z johnnyw $
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*
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* @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
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*/
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//=============================================================================
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#ifndef ACE_RW_PROCESS_MUTEX_H
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#define ACE_RW_PROCESS_MUTEX_H
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#include /**/ "ace/pre.h"
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#include "ace/File_Lock.h"
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#if !defined (ACE_LACKS_PRAGMA_ONCE)
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# pragma once
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#endif /* ACE_LACKS_PRAGMA_ONCE */
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#include "ace/Default_Constants.h"
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ACE_BEGIN_VERSIONED_NAMESPACE_DECL
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/**
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* @class ACE_RW_Process_Mutex
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*
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* @brief Wrapper for readers/writer locks that exist across processes.
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*
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* @note This class uses an ACE_File_Lock as its implementation. Thus, it
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* can only be reliably used between separate processes, rather than
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* threads in the same process. This isn't a limitation of ACE, it's simply
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* the file lock semantics on UNIX and Win32.
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*
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* @todo For systems with pthread_rwlockattr_setpshared one
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* may consider using them to make the mutex faster.
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*/
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class ACE_Export ACE_RW_Process_Mutex
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{
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public:
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/// Create a cross-process readers/writer mutex, passing in the optional
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/// @a name, @a flags and @a mode \sa ACE_File_Lock.
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/// If not specified, a name is generated and flags and mode are set
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/// to default platform values.
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ACE_RW_Process_Mutex (const ACE_TCHAR *name = 0,
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int flags = O_CREAT|O_RDWR,
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mode_t mode = ACE_DEFAULT_RW_PROCESS_MUTEX_PERMS);
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~ACE_RW_Process_Mutex (void);
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/**
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* Explicitly destroy the mutex. Note that only one thread should
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* call this method since it doesn't protect against race
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* conditions.
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*/
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int remove (void);
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/// Same as acquire_write().
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/// Acquire lock ownership; blocks until the lock is acquired or the
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/// operation fails.
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int acquire (void);
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/**
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* Same as tryacquire_write().
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* Try to acquire the lock, but do not block if the lock is not immediately
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* acquired.
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*
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* @retval -1 on failure. If the lock is already held, @c errno is set
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* to @c EBUSY.
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*/
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int tryacquire (void);
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/// Release lock.
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int release (void);
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/// Acquire read lock; blocks until the lock is acquired or the
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/// operation fails.
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int acquire_read (void);
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/// Acquire write lock; blocks until the lock is acquired or the
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/// operation fails.
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int acquire_write (void);
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/**
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* Try to acquire the read lock, but do not block if the lock is not
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* immediately acquired.
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*
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* @retval -1 on failure. If the lock is already held, @c errno is set
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* to @c EBUSY.
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*/
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int tryacquire_read (void);
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/**
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* Try to acquire the write lock, but do not block if the lock is not
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* immediately acquired.
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*
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* @retval -1 on failure. If the lock is already held, @c errno is set
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* to @c EBUSY.
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*/
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int tryacquire_write (void);
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/// Attempt to upgrade a read lock to a write lock. Returns 0 on
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/// success, -1 on failure.
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int tryacquire_write_upgrade (void);
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/// Return the underlying lock.
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const ACE_File_Lock &lock (void) const;
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/// Dump the state of an object.
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void dump (void) const;
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/// Declare the dynamic allocation hooks.
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ACE_ALLOC_HOOK_DECLARE;
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private:
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/// If the user does not provide a name we generate a unique name in
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/// this buffer.
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ACE_TCHAR name_[ACE_UNIQUE_NAME_LEN];
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/// Create and return the unique name.
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const ACE_TCHAR *unique_name (void);
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/// We need this to get the readers/writer semantics...
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ACE_File_Lock lock_;
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};
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ACE_END_VERSIONED_NAMESPACE_DECL
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#if defined (__ACE_INLINE__)
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#include "ace/RW_Process_Mutex.inl"
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#endif /* __ACE_INLINE__ */
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#include /**/ "ace/post.h"
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#endif /* ACE_RW_PROCESS_MUTEX_H */
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