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:
11 // * Redistributions of source code must retain the above copyright
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,
26 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
27 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
28 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
29 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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
51 namespace IlmThread {
52
53
Semaphore(unsigned int value)54 Semaphore::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
~Semaphore()68 Semaphore::~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
77 void
wait()78 Semaphore::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
103 bool
tryWait()104 Semaphore::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
122 void
post()123 Semaphore::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
143 int
value() const144 Semaphore::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