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      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 
     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 
     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
     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
    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
    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
    144 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