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// -*- C++ -*-
//==========================================================================
/**
* @file Null_Semaphore.h
*
* $Id$
*
* Moved from Synch.h.
*
* @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
*/
//==========================================================================
#ifndef ACE_NULL_SEMAPHORE_H
#define ACE_NULL_SEMAPHORE_H
#include /**/ "ace/pre.h"
// All methods in this class are inline, so there is no
// need to import or export on Windows. -- CAE 12/18/2003
#include "ace/os_include/os_errno.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
ACE_BEGIN_VERSIONED_NAMESPACE_DECL
class ACE_Time_Value;
/**
* @class ACE_Null_Semaphore
*
* @brief Implement a do nothing ACE_Semaphore, i.e., all the methods are
* no ops.
*
* Although the methods are no-ops, the return values are different for
* the blocking as opposed to timed acquires. The blocking version of
* acquire() is often used to serialize access to a critical section,
* whereas the timed version is often used to wait for another thread
* to update some condition or change some shared state. When using an
* ACE_Null_Semaphore, however, there's no other thread involved to
* change a state or condition (otherwise, a null semaphore would be
* inappropriate). Returning an error value signifies that the
* state or condition has not been (and can't be) changed, which is
* consistent with the behavior of the threaded case where a timeout
* occurs before the state or condition is changed.
*/
class ACE_Null_Semaphore
{
public:
ACE_Null_Semaphore (unsigned int = 1,
int = 0,
const ACE_TCHAR * = 0,
void * = 0,
int = 0x7fffffff) {}
~ACE_Null_Semaphore (void) {}
/// Return 0.
int remove (void) {return 0;}
/// Return 0.
int acquire (void) {return 0;}
/// Return -1 with <errno> == <ETIME>.
int acquire (ACE_Time_Value &) {errno = ETIME; return -1;}
/// Return -1 with <errno> == <ETIME>.
int acquire (ACE_Time_Value *) {errno = ETIME; return -1;}
/// Return 0.
int tryacquire (void) {return 0;}
/// Return 0.
int release (void) {return 0;}
/// Return 0.
int release (size_t) {return 0;}
/// Return 0.
int acquire_write (void) {return 0;}
/// Return 0.
int tryacquire_write (void) {return 0;}
/// Return 0.
int tryacquire_write_upgrade (void) {return 0;}
/// Return 0.
int acquire_read (void) {return 0;}
/// Return 0.
int tryacquire_read (void) {return 0;}
/// Dump the state of an object.
void dump (void) const {}
/// Declare the dynamic allocation hooks.
//ACE_ALLOC_HOOK_DECLARE;
};
ACE_END_VERSIONED_NAMESPACE_DECL
#include /**/ "ace/post.h"
#endif /* ACE_NULL_SEMAPHORE_H */
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