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<li class="navelem"><b>sf</b></li><li class="navelem"><a class="el" href="classsf_1_1Mutex.html">Mutex</a></li> </ul>
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<div class="title">sf::Mutex Class Reference<div class="ingroups"><a class="el" href="group__system.html">System module</a></div></div> </div>
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<p>Blocks concurrent access to shared resources from multiple threads.
<a href="classsf_1_1Mutex.html#details">More...</a></p>
<p><code>#include &lt;<a class="el" href="Mutex_8hpp_source.html">Mutex.hpp</a>&gt;</code></p>
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Inheritance diagram for sf::Mutex:</div>
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Public Member Functions</h2></td></tr>
<tr class="memitem:a9bd52a48320fd7b6db8a78037aad276e"><td class="memItemLeft" align="right" valign="top">&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classsf_1_1Mutex.html#a9bd52a48320fd7b6db8a78037aad276e">Mutex</a> ()</td></tr>
<tr class="memdesc:a9bd52a48320fd7b6db8a78037aad276e"><td class="mdescLeft">&#160;</td><td class="mdescRight">Default constructor. <a href="#a9bd52a48320fd7b6db8a78037aad276e">More...</a><br /></td></tr>
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<tr class="memitem:a9f76a67b7b6d3918131a692179b4e3f2"><td class="memItemLeft" align="right" valign="top">&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classsf_1_1Mutex.html#a9f76a67b7b6d3918131a692179b4e3f2">~Mutex</a> ()</td></tr>
<tr class="memdesc:a9f76a67b7b6d3918131a692179b4e3f2"><td class="mdescLeft">&#160;</td><td class="mdescRight">Destructor. <a href="#a9f76a67b7b6d3918131a692179b4e3f2">More...</a><br /></td></tr>
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<tr class="memitem:a1a16956a6bbea764480c1b80f2e45763"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classsf_1_1Mutex.html#a1a16956a6bbea764480c1b80f2e45763">lock</a> ()</td></tr>
<tr class="memdesc:a1a16956a6bbea764480c1b80f2e45763"><td class="mdescLeft">&#160;</td><td class="mdescRight"><a class="el" href="classsf_1_1Lock.html" title="Automatic wrapper for locking and unlocking mutexes. ">Lock</a> the mutex. <a href="#a1a16956a6bbea764480c1b80f2e45763">More...</a><br /></td></tr>
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<tr class="memitem:ade71268ffc5e80756652058b01c23c33"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classsf_1_1Mutex.html#ade71268ffc5e80756652058b01c23c33">unlock</a> ()</td></tr>
<tr class="memdesc:ade71268ffc5e80756652058b01c23c33"><td class="mdescLeft">&#160;</td><td class="mdescRight">Unlock the mutex. <a href="#ade71268ffc5e80756652058b01c23c33">More...</a><br /></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p>Blocks concurrent access to shared resources from multiple threads. </p>
<p><a class="el" href="classsf_1_1Mutex.html" title="Blocks concurrent access to shared resources from multiple threads. ">Mutex</a> stands for "MUTual EXclusion".</p>
<p>A mutex is a synchronization object, used when multiple threads are involved.</p>
<p>When you want to protect a part of the code from being accessed simultaneously by multiple threads, you typically use a mutex. When a thread is locked by a mutex, any other thread trying to lock it will be blocked until the mutex is released by the thread that locked it. This way, you can allow only one thread at a time to access a critical region of your code.</p>
<p>Usage example: </p><div class="fragment"><div class="line">Database database; <span class="comment">// this is a critical resource that needs some protection</span></div><div class="line"><a class="code" href="classsf_1_1Mutex.html">sf::Mutex</a> mutex;</div><div class="line"></div><div class="line"><span class="keywordtype">void</span> thread1()</div><div class="line">{</div><div class="line"> mutex.<a class="code" href="classsf_1_1Mutex.html#a1a16956a6bbea764480c1b80f2e45763">lock</a>(); <span class="comment">// this call will block the thread if the mutex is already locked by thread2</span></div><div class="line"> database.write(...);</div><div class="line"> mutex.<a class="code" href="classsf_1_1Mutex.html#ade71268ffc5e80756652058b01c23c33">unlock</a>(); <span class="comment">// if thread2 was waiting, it will now be unblocked</span></div><div class="line">}</div><div class="line"></div><div class="line"><span class="keywordtype">void</span> thread2()</div><div class="line">{</div><div class="line"> mutex.<a class="code" href="classsf_1_1Mutex.html#a1a16956a6bbea764480c1b80f2e45763">lock</a>(); <span class="comment">// this call will block the thread if the mutex is already locked by thread1</span></div><div class="line"> database.write(...);</div><div class="line"> mutex.<a class="code" href="classsf_1_1Mutex.html#ade71268ffc5e80756652058b01c23c33">unlock</a>(); <span class="comment">// if thread1 was waiting, it will now be unblocked</span></div><div class="line">}</div></div><!-- fragment --><p>Be very careful with mutexes. A bad usage can lead to bad problems, like deadlocks (two threads are waiting for each other and the application is globally stuck).</p>
<p>To make the usage of mutexes more robust, particularly in environments where exceptions can be thrown, you should use the helper class <a class="el" href="classsf_1_1Lock.html" title="Automatic wrapper for locking and unlocking mutexes. ">sf::Lock</a> to lock/unlock mutexes.</p>
<p>SFML mutexes are recursive, which means that you can lock a mutex multiple times in the same thread without creating a deadlock. In this case, the first call to <a class="el" href="classsf_1_1Mutex.html#a1a16956a6bbea764480c1b80f2e45763" title="Lock the mutex. ">lock()</a> behaves as usual, and the following ones have no effect. However, you must call <a class="el" href="classsf_1_1Mutex.html#ade71268ffc5e80756652058b01c23c33" title="Unlock the mutex. ">unlock()</a> exactly as many times as you called <a class="el" href="classsf_1_1Mutex.html#a1a16956a6bbea764480c1b80f2e45763" title="Lock the mutex. ">lock()</a>. If you don't, the mutex won't be released.</p>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="classsf_1_1Lock.html" title="Automatic wrapper for locking and unlocking mutexes. ">sf::Lock</a> </dd></dl>
<p class="definition">Definition at line <a class="el" href="Mutex_8hpp_source.html#l00047">47</a> of file <a class="el" href="Mutex_8hpp_source.html">Mutex.hpp</a>.</p>
</div><h2 class="groupheader">Constructor &amp; Destructor Documentation</h2>
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<h2 class="memtitle"><span class="permalink"><a href="#a9bd52a48320fd7b6db8a78037aad276e">&#9670;&nbsp;</a></span>Mutex()</h2>
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<td class="memname">sf::Mutex::Mutex </td>
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<p>Default constructor. </p>
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<h2 class="memtitle"><span class="permalink"><a href="#a9f76a67b7b6d3918131a692179b4e3f2">&#9670;&nbsp;</a></span>~Mutex()</h2>
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<td class="memname">sf::Mutex::~Mutex </td>
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<p>Destructor. </p>
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<h2 class="groupheader">Member Function Documentation</h2>
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<h2 class="memtitle"><span class="permalink"><a href="#a1a16956a6bbea764480c1b80f2e45763">&#9670;&nbsp;</a></span>lock()</h2>
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<td class="memname">void sf::Mutex::lock </td>
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<p><a class="el" href="classsf_1_1Lock.html" title="Automatic wrapper for locking and unlocking mutexes. ">Lock</a> the mutex. </p>
<p>If the mutex is already locked in another thread, this call will block the execution until the mutex is released.</p>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="classsf_1_1Mutex.html#ade71268ffc5e80756652058b01c23c33" title="Unlock the mutex. ">unlock</a> </dd></dl>
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<h2 class="memtitle"><span class="permalink"><a href="#ade71268ffc5e80756652058b01c23c33">&#9670;&nbsp;</a></span>unlock()</h2>
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<td class="memname">void sf::Mutex::unlock </td>
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<p>Unlock the mutex. </p>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="classsf_1_1Mutex.html#a1a16956a6bbea764480c1b80f2e45763" title="Lock the mutex. ">lock</a> </dd></dl>
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