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103 lines
2.7 KiB
C++
103 lines
2.7 KiB
C++
// -*- C++ -*-
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//==========================================================================
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/**
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* @file Null_Semaphore.h
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*
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* $Id: Null_Semaphore.h 91626 2010-09-07 10:59:20Z johnnyw $
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*
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* Moved from Synch.h.
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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_NULL_SEMAPHORE_H
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#define ACE_NULL_SEMAPHORE_H
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#include /**/ "ace/pre.h"
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#include "ace/os_include/os_errno.h"
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#include "ace/os_include/sys/os_types.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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ACE_BEGIN_VERSIONED_NAMESPACE_DECL
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class ACE_Time_Value;
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/**
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* @class ACE_Null_Semaphore
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*
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* @brief Implement a do nothing ACE_Semaphore, i.e., all the methods are
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* no ops.
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*
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* Although the methods are no-ops, the return values are different for
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* the blocking as opposed to timed acquires. The blocking version of
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* acquire() is often used to serialize access to a critical section,
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* whereas the timed version is often used to wait for another thread
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* to update some condition or change some shared state. When using an
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* ACE_Null_Semaphore, however, there's no other thread involved to
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* change a state or condition (otherwise, a null semaphore would be
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* inappropriate). Returning an error value signifies that the
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* state or condition has not been (and can't be) changed, which is
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* consistent with the behavior of the threaded case where a timeout
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* occurs before the state or condition is changed.
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*/
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class ACE_Null_Semaphore
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{
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public:
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ACE_Null_Semaphore (unsigned int = 1,
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int = 0,
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const ACE_TCHAR * = 0,
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void * = 0,
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int = 0x7fffffff) {}
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~ACE_Null_Semaphore (void) {}
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/// Return 0.
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int remove (void) {return 0;}
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/// Return 0.
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int acquire (void) {return 0;}
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/// Return -1 with @c errno == @c ETIME.
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int acquire (ACE_Time_Value &) {errno = ETIME; return -1;}
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/// Return -1 with @c errno == @c ETIME.
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int acquire (ACE_Time_Value *) {errno = ETIME; return -1;}
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/// Return 0.
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int tryacquire (void) {return 0;}
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/// Return 0.
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int release (void) {return 0;}
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/// Return 0.
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int release (size_t) {return 0;}
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/// Return 0.
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int acquire_write (void) {return 0;}
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/// Return 0.
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int tryacquire_write (void) {return 0;}
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/// Return 0.
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int tryacquire_write_upgrade (void) {return 0;}
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/// Return 0.
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int acquire_read (void) {return 0;}
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/// Return 0.
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int tryacquire_read (void) {return 0;}
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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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};
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ACE_END_VERSIONED_NAMESPACE_DECL
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#include /**/ "ace/post.h"
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#endif /* ACE_NULL_SEMAPHORE_H */
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