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<h1>semaphore.h</h1><a href="semaphore_8h.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">///</span>
<a name="l00002"></a>00002 <span class="comment"></span><span class="comment">/// \file semaphore.h</span>
<a name="l00003"></a>00003 <span class="comment"></span><span class="comment">/// Simple class implementing a semaphore using pthreads mutex and condvar.</span>
<a name="l00004"></a>00004 <span class="comment"></span><span class="comment">///</span>
<a name="l00005"></a>00005 <span class="comment"></span>
<a name="l00006"></a>00006 <span class="comment">/*</span>
<a name="l00007"></a>00007 <span class="comment"> Copyright (C) 2010, RealVNC Ltd.</span>
<a name="l00008"></a>00008 <span class="comment"></span>
<a name="l00009"></a>00009 <span class="comment"> This program is free software; you can redistribute it and/or modify</span>
<a name="l00010"></a>00010 <span class="comment"> it under the terms of the GNU General Public License as published by</span>
<a name="l00011"></a>00011 <span class="comment"> the Free Software Foundation; either version 2 of the License, or</span>
<a name="l00012"></a>00012 <span class="comment"> (at your option) any later version.</span>
<a name="l00013"></a>00013 <span class="comment"></span>
<a name="l00014"></a>00014 <span class="comment"> This program is distributed in the hope that it will be useful,</span>
<a name="l00015"></a>00015 <span class="comment"> but WITHOUT ANY WARRANTY; without even the implied warranty of</span>
<a name="l00016"></a>00016 <span class="comment"> MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.</span>
<a name="l00017"></a>00017 <span class="comment"></span>
<a name="l00018"></a>00018 <span class="comment"> See the GNU General Public License in the COPYING file at the</span>
<a name="l00019"></a>00019 <span class="comment"> root directory of this project for more details.</span>
<a name="l00020"></a>00020 <span class="comment">*/</span>
<a name="l00021"></a>00021
<a name="l00022"></a>00022 <span class="preprocessor">#ifndef __BARRY_SEMAPHORE_H__</span>
<a name="l00023"></a>00023 <span class="preprocessor"></span><span class="preprocessor">#define __BARRY_SEMAPHORE_H__</span>
<a name="l00024"></a>00024 <span class="preprocessor"></span>
<a name="l00025"></a>00025 <span class="preprocessor">#include "<a class="code" href="scoped__lock_8h.html" title="Simple scope class for dealing with pthread mutex locking.">scoped_lock.h</a>"</span>
<a name="l00026"></a>00026 <span class="preprocessor">#include <pthread.h></span>
<a name="l00027"></a>00027
<a name="l00028"></a>00028 <span class="keyword">namespace </span>Barry {
<a name="l00029"></a>00029
<a name="l00030"></a>00030 <span class="keyword">class </span>semaphore
<a name="l00031"></a>00031 {
<a name="l00032"></a>00032 pthread_mutex_t *m_mutex;
<a name="l00033"></a>00033 pthread_cond_t *m_cv;
<a name="l00034"></a>00034 <span class="keywordtype">int</span> m_value;
<a name="l00035"></a>00035 <span class="keyword">public</span>:
<a name="l00036"></a>00036 semaphore(pthread_mutex_t &mutex, pthread_cond_t &cv, <span class="keywordtype">int</span> value = 0)
<a name="l00037"></a>00037 : m_mutex(&mutex)
<a name="l00038"></a>00038 , m_cv(&cv)
<a name="l00039"></a>00039 , m_value(value)
<a name="l00040"></a>00040 {
<a name="l00041"></a>00041 }
<a name="l00042"></a>00042
<a name="l00043"></a>00043 <span class="comment">// Waits for the value of this semaphore to be greater than 0 and then</span>
<a name="l00044"></a>00044 <span class="comment">// decrements it by one before returning.</span>
<a name="l00045"></a>00045 <span class="keywordtype">void</span> WaitForSignal()
<a name="l00046"></a>00046 {
<a name="l00047"></a>00047 scoped_lock lock(*m_mutex);
<a name="l00048"></a>00048 <span class="keywordflow">while</span>( m_value <= 0 ) {
<a name="l00049"></a>00049 <span class="keywordtype">int</span> ret = pthread_cond_wait(m_cv, m_mutex);
<a name="l00050"></a>00050 <span class="keywordflow">if</span>( ret != 0 ) {
<a name="l00051"></a>00051 <span class="keywordflow">throw</span> <a class="code" href="classBarry_1_1Error.html" title="The base class for any future derived exceptions.">Barry::Error</a>(<span class="stringliteral">"semaphore: failed to wait on condvar"</span>);
<a name="l00052"></a>00052 }
<a name="l00053"></a>00053 }
<a name="l00054"></a>00054 --m_value;
<a name="l00055"></a>00055 lock.unlock();
<a name="l00056"></a>00056 }
<a name="l00057"></a>00057
<a name="l00058"></a>00058 <span class="comment">// Checks for a semaphore signal without blocking. Returns true and decrements</span>
<a name="l00059"></a>00059 <span class="comment">// the semaphore if the value is greater than 0, otherwise returns false.</span>
<a name="l00060"></a>00060 <span class="keywordtype">bool</span> ReceiveSignal()
<a name="l00061"></a>00061 {
<a name="l00062"></a>00062 <span class="keywordtype">bool</span> ret = <span class="keyword">false</span>;
<a name="l00063"></a>00063 scoped_lock lock(*m_mutex);
<a name="l00064"></a>00064 <span class="keywordflow">if</span>( m_value > 0 ) {
<a name="l00065"></a>00065 --m_value;
<a name="l00066"></a>00066 ret = <span class="keyword">true</span>;
<a name="l00067"></a>00067 }
<a name="l00068"></a>00068 lock.unlock();
<a name="l00069"></a>00069 <span class="keywordflow">return</span> ret;
<a name="l00070"></a>00070 }
<a name="l00071"></a>00071
<a name="l00072"></a>00072 <span class="comment">// Increments the value of this semaphore by 1, waking any sleeping threads waiting</span>
<a name="l00073"></a>00073 <span class="comment">// on this semaphore.</span>
<a name="l00074"></a>00074 <span class="keywordtype">void</span> Signal()
<a name="l00075"></a>00075 {
<a name="l00076"></a>00076 scoped_lock lock(*m_mutex);
<a name="l00077"></a>00077 ++m_value;
<a name="l00078"></a>00078 <span class="keywordtype">int</span> ret = pthread_cond_signal(m_cv);
<a name="l00079"></a>00079 <span class="keywordflow">if</span>( ret != 0 ) {
<a name="l00080"></a>00080 <span class="keywordflow">throw</span> <a class="code" href="classBarry_1_1Error.html" title="The base class for any future derived exceptions.">Barry::Error</a>(<span class="stringliteral">"Condvar: failed to signal condvar"</span>);
<a name="l00081"></a>00081 }
<a name="l00082"></a>00082 lock.unlock();
<a name="l00083"></a>00083 }
<a name="l00084"></a>00084 };
<a name="l00085"></a>00085
<a name="l00086"></a>00086 } <span class="comment">// namespace Barry</span>
<a name="l00087"></a>00087
<a name="l00088"></a>00088 <span class="preprocessor">#endif</span>
<a name="l00089"></a>00089 <span class="preprocessor"></span>
</pre></div></div>
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