/src/FreeImage/Source/OpenEXR/IlmThread/IlmThreadSemaphorePosixCompat.cpp

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  2//
  3// Copyright (c) 2005, Industrial Light & Magic, a division of Lucas
  4// Digital Ltd. LLC
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 33///////////////////////////////////////////////////////////////////////////
 34
 35//-----------------------------------------------------------------------------
 36//
 37//	class Semaphore -- implementation for for platforms that do
 38//	support Posix threads but do not support Posix semaphores,
 39//	for example, OS X
 40//
 41//-----------------------------------------------------------------------------
 42
 43#include "IlmBaseConfig.h"
 44
 45#if HAVE_PTHREAD && !HAVE_POSIX_SEMAPHORES
 46
 47#include "IlmThreadSemaphore.h"
 48#include "Iex.h"
 49#include <assert.h>
 50
 51namespace IlmThread {
 52
 53
 54Semaphore::Semaphore (unsigned int value)
 55{
 56    if (int error = ::pthread_mutex_init (&_semaphore.mutex, 0))
 57        Iex::throwErrnoExc ("Cannot initialize mutex (%T).", error);
 58
 59    if (int error = ::pthread_cond_init (&_semaphore.nonZero, 0))
 60        Iex::throwErrnoExc ("Cannot initialize condition variable (%T).",
 61                            error);
 62
 63    _semaphore.count = value;
 64    _semaphore.numWaiting = 0;
 65}
 66
 67
 68Semaphore::~Semaphore ()
 69{
 70    int error = ::pthread_cond_destroy (&_semaphore.nonZero);
 71    assert (error == 0);
 72    error = ::pthread_mutex_destroy (&_semaphore.mutex);
 73    assert (error == 0);
 74}
 75
 76
 77void
 78Semaphore::wait ()
 79{
 80    ::pthread_mutex_lock (&_semaphore.mutex);
 81
 82    _semaphore.numWaiting++;
 83
 84    while (_semaphore.count == 0)
 85    {
 86        if (int error = ::pthread_cond_wait (&_semaphore.nonZero,
 87                                             &_semaphore.mutex))
 88	{
 89            ::pthread_mutex_unlock (&_semaphore.mutex);
 90
 91            Iex::throwErrnoExc ("Cannot wait on condition variable (%T).",
 92                                error);
 93	}
 94    }
 95
 96    _semaphore.numWaiting--;
 97    _semaphore.count--;
 98
 99    ::pthread_mutex_unlock (&_semaphore.mutex);
100}
101
102
103bool
104Semaphore::tryWait ()
105{
106    ::pthread_mutex_lock (&_semaphore.mutex);
107    
108    if (_semaphore.count == 0)
109    {
110        ::pthread_mutex_unlock (&_semaphore.mutex);
111        return false;
112    }
113    else
114    {
115        _semaphore.count--;
116        ::pthread_mutex_unlock (&_semaphore.mutex);
117        return true;
118    }
119}
120
121
122void
123Semaphore::post ()
124{
125    ::pthread_mutex_lock (&_semaphore.mutex);
126
127    if (_semaphore.numWaiting > 0)
128    {
129        if (int error = ::pthread_cond_signal (&_semaphore.nonZero))
130	{
131            ::pthread_mutex_unlock (&_semaphore.mutex);
132
133            Iex::throwErrnoExc ("Cannot signal condition variable (%T).",
134                                error);
135	}
136    }
137
138    _semaphore.count++;
139    ::pthread_mutex_unlock (&_semaphore.mutex);
140}
141
142
143int
144Semaphore::value () const
145{
146    ::pthread_mutex_lock (&_semaphore.mutex);
147    int value = _semaphore.count;
148    ::pthread_mutex_unlock (&_semaphore.mutex);
149    return value;
150}
151
152
153} // namespace IlmThread
154
155#endif