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/* -*- C++ -*- */
//=============================================================================
/**
* @file Process_Semaphore.h
*
* $Id$
*
* Wrapper for Dijkstra style general semaphores that work
* across processes.
*
*
* @author Doug Schmidt
*/
//=============================================================================
#ifndef ACE_PROCESS_SEMAPHORE_H
#define ACE_PROCESS_SEMAPHORE_H
#include "ace/pre.h"
#include "ace/Synch.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
#if !(defined (ACE_WIN32) || defined (ACE_HAS_POSIX_SEM) || defined (ACE_PSOS))
#include "ace/SV_Semaphore_Complex.h"
#endif /* !(ACE_WIN32 || ACE_HAS_POSIX_SEM || ACE_PSOS) */
/**
* @class ACE_Process_Semaphore
*
* @brief Wrapper for Dijkstra style general semaphores that work
* across processes.
*/
class ACE_Export ACE_Process_Semaphore
{
public:
/// Initialize the semaphore, with an initial value of <count> and a
/// maximum value of <max>.
ACE_Process_Semaphore (u_int count = 1, // By default make this unlocked.
const ACE_TCHAR *name = 0,
void * = 0,
int max = 0x7FFFFFFF);
/**
* This method is a no-op, i.e., it doesn't remove the semaphore.
* If you want to remove the semaphore, you must call the <remove>
* method explicitly.
*/
~ACE_Process_Semaphore (void);
/**
* Explicitly destroy the semaphore. Note that only one thread
* should call this method since it doesn't protect against race
* conditions.
*/
int remove (void);
/// Block the thread until the semaphore count becomes greater than
/// 0, then decrement it.
int acquire (void);
/**
* Conditionally decrement the semaphore if count is greater than 0
* (i.e., won't block). Returns -1 on failure. If we "failed"
* because someone else already had the lock, <errno> is set to
* <EBUSY>.
*/
int tryacquire (void);
/// Increment the semaphore, potentially unblocking a waiting thread.
int release (void);
/**
* Acquire semaphore ownership. This calls <acquire> and is only
* here to make the <ACE_Process_Semaphore> interface consistent
* with the other synchronization APIs.
*/
int acquire_read (void);
/**
* Acquire semaphore ownership. This calls <acquire> and is only
* here to make the <ACE_Process_Semaphore> interface consistent
* with the other synchronization APIs.
*/
int acquire_write (void);
/**
* Conditionally acquire semaphore (i.e., won't block). This calls
* <tryacquire> and is only here to make the <ACE_Process_Semaphore>
* interface consistent with the other synchronization APIs.
* Returns -1 on failure. If we "failed" because someone else
* already had the lock, <errno> is set to <EBUSY>.
*/
int tryacquire_read (void);
/**
* Conditionally acquire semaphore (i.e., won't block). This calls
* <tryacquire> and is only here to make the <ACE_Process_Semaphore>
* interface consistent with the other synchronization APIs.
* Returns -1 on failure. If we "failed" because someone else
* already had the lock, <errno> is set to <EBUSY>.
*/
int tryacquire_write (void);
/**
* This is only here to make the <ACE_Process_Semaphore>
* interface consistent with the other synchronization APIs.
* Assumes the caller has already acquired the semaphore using one of
* the above calls, and returns 0 (success) always.
*/
int tryacquire_write_upgrade (void);
#if defined (ACE_WIN32) || defined (ACE_HAS_POSIX_SEM) || defined (ACE_PSOS)
/// Return the underlying lock.
const ACE_sema_t &lock (void) const;
#endif /* ACE_WIN32 || ACE_HAS_POSIX_SEM || ACE_PSOS */
/// Dump the state of an object.
void dump (void) const;
/// Declare the dynamic allocation hooks.
ACE_ALLOC_HOOK_DECLARE;
protected:
#if defined (ACE_WIN32) || defined (ACE_HAS_POSIX_SEM) || defined (ACE_PSOS)
ACE_Semaphore lock_;
#else
/// We need this to get the right semantics...
ACE_SV_Semaphore_Complex lock_;
#endif /* ACE_WIN32 || ACE_HAS_POSIX_SEM || ACE_PSOS */
};
#if defined (__ACE_INLINE__)
#include "ace/Process_Semaphore.inl"
#endif /* __ACE_INLINE__ */
#include "ace/post.h"
#endif /* ACE_PROCESS_SEMAPHORE_H */
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