1///////////////////////////////////////////////////////////////////////////
2//
3// Copyright (c) 2005, Industrial Light & Magic, a division of Lucas
4// Digital Ltd. LLC
5//
6// All rights reserved.
7//
8// Redistribution and use in source and binary forms, with or without
9// modification, are permitted provided that the following conditions are
10// met:
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12// notice, this list of conditions and the following disclaimer.
13// *       Redistributions in binary form must reproduce the above
14// copyright notice, this list of conditions and the following disclaimer
15// in the documentation and/or other materials provided with the
16// distribution.
17// *       Neither the name of Industrial Light & Magic nor the names of
18// its contributors may be used to endorse or promote products derived
19// from this software without specific prior written permission.
20//
21// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
24// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
25// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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27// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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30// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
31// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32//
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
156