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id="nav-path" class="navpath"> <ul><li class="navelem"><b>sf</b></li><li class="navelem"><a class="el" href="classsf_1_1Mutex.htm">Mutex</a></li> </ul></div></div><!-- top --><div class="header"> <div class="summary"><a href="#pub-methods">Public Member Functions</a> |<a href="classsf_1_1Mutex-members.htm">List of all members</a> </div> <div class="headertitle"><div class="title">sf::Mutex Class Reference<div class="ingroups"><a class="el" href="group__system.htm">System module</a></div></div> </div></div><!--header--><div class="contents"><p>Blocks concurrent access to shared resources from multiple threads. <a href="classsf_1_1Mutex.htm#details">More...</a></p><p><code>#include <<a class="el" href="Mutex_8hpp_source.htm">Mutex.hpp</a>></code></p><div class="dynheader">Inheritance diagram for sf::Mutex:</div><div class="dyncontent"> <div class="center"> <img src="classsf_1_1Mutex.png" usemap="#sf::Mutex_map" alt=""/> <map id="sf::Mutex_map" name="sf::Mutex_map"><area href="classsf_1_1NonCopyable.htm" title="Utility class that makes any derived class non-copyable." alt="sf::NonCopyable" shape="rect" coords="0,0,105,24"/></map> </div></div><table class="memberdecls"><tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="pub-methods"></a>Public Member Functions</h2></td></tr><tr class="memitem:a9bd52a48320fd7b6db8a78037aad276e"><td class="memItemLeft" align="right" valign="top"> </td><td class="memItemRight" valign="bottom"><a class="el" href="classsf_1_1Mutex.htm#a9bd52a48320fd7b6db8a78037aad276e">Mutex</a> ()</td></tr><tr class="memdesc:a9bd52a48320fd7b6db8a78037aad276e"><td class="mdescLeft"> </td><td class="mdescRight">Default constructor. <a href="#a9bd52a48320fd7b6db8a78037aad276e"></a><br/></td></tr><tr class="separator:a9bd52a48320fd7b6db8a78037aad276e"><td class="memSeparator" colspan="2"> </td></tr><tr class="memitem:a9f76a67b7b6d3918131a692179b4e3f2"><td class="memItemLeft" align="right" valign="top"> </td><td class="memItemRight" valign="bottom"><a class="el" href="classsf_1_1Mutex.htm#a9f76a67b7b6d3918131a692179b4e3f2">~Mutex</a> ()</td></tr><tr class="memdesc:a9f76a67b7b6d3918131a692179b4e3f2"><td class="mdescLeft"> </td><td class="mdescRight">Destructor. <a href="#a9f76a67b7b6d3918131a692179b4e3f2"></a><br/></td></tr><tr class="separator:a9f76a67b7b6d3918131a692179b4e3f2"><td class="memSeparator" colspan="2"> </td></tr><tr class="memitem:a1a16956a6bbea764480c1b80f2e45763"><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><a class="el" href="classsf_1_1Mutex.htm#a1a16956a6bbea764480c1b80f2e45763">lock</a> ()</td></tr><tr class="memdesc:a1a16956a6bbea764480c1b80f2e45763"><td class="mdescLeft"> </td><td class="mdescRight"><a class="el" href="classsf_1_1Lock.htm" title="Automatic wrapper for locking and unlocking mutexes.">Lock</a> the mutex. <a href="#a1a16956a6bbea764480c1b80f2e45763"></a><br/></td></tr><tr class="separator:a1a16956a6bbea764480c1b80f2e45763"><td class="memSeparator" colspan="2"> </td></tr><tr class="memitem:ade71268ffc5e80756652058b01c23c33"><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><a class="el" href="classsf_1_1Mutex.htm#ade71268ffc5e80756652058b01c23c33">unlock</a> ()</td></tr><tr class="memdesc:ade71268ffc5e80756652058b01c23c33"><td class="mdescLeft"> </td><td class="mdescRight">Unlock the mutex. <a href="#ade71268ffc5e80756652058b01c23c33"></a><br/></td></tr><tr class="separator:ade71268ffc5e80756652058b01c23c33"><td class="memSeparator" colspan="2"> </td></tr></table><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.htm" 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.htm" title="Blocks concurrent access to shared resources from multiple threads.">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.htm#a1a16956a6bbea764480c1b80f2e45763" title="Lock the mutex.">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.htm#ade71268ffc5e80756652058b01c23c33" title="Unlock the mutex.">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.htm#a1a16956a6bbea764480c1b80f2e45763" title="Lock the mutex.">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.htm#ade71268ffc5e80756652058b01c23c33" title="Unlock the mutex.">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.htm" 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.htm#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.htm#ade71268ffc5e80756652058b01c23c33" title="Unlock the mutex.">unlock()</a> exactly as many times as you called <a class="el" href="classsf_1_1Mutex.htm#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.htm" title="Automatic wrapper for locking and unlocking mutexes.">sf::Lock</a> </dd></dl><p>Definition at line <a class="el" href="Mutex_8hpp_source.htm#l00047">47</a> of file <a class="el" href="Mutex_8hpp_source.htm">Mutex.hpp</a>.</p></div><h2 class="groupheader">Constructor & Destructor Documentation</h2><a class="anchor" id="a9bd52a48320fd7b6db8a78037aad276e"></a><div class="memitem"><div class="memproto"> <table class="memname"> <tr> <td class="memname">sf::Mutex::Mutex </td> <td>(</td> <td class="paramname"></td><td>)</td> <td></td> </tr> </table></div><div class="memdoc"><p>Default constructor. </p></div></div><a class="anchor" id="a9f76a67b7b6d3918131a692179b4e3f2"></a><div class="memitem"><div class="memproto"> <table class="memname"> <tr> <td class="memname">sf::Mutex::~Mutex </td> <td>(</td> <td class="paramname"></td><td>)</td> <td></td> </tr> </table></div><div class="memdoc"><p>Destructor. </p></div></div><h2 class="groupheader">Member Function Documentation</h2><a class="anchor" id="a1a16956a6bbea764480c1b80f2e45763"></a><div class="memitem"><div class="memproto"> <table class="memname"> <tr> <td class="memname">void sf::Mutex::lock </td> <td>(</td> <td class="paramname"></td><td>)</td> <td></td> </tr> </table></div><div class="memdoc"><p><a class="el" href="classsf_1_1Lock.htm" 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.htm#ade71268ffc5e80756652058b01c23c33" title="Unlock the mutex.">unlock</a> </dd></dl></div></div><a class="anchor" id="ade71268ffc5e80756652058b01c23c33"></a><div class="memitem"><div class="memproto"> <table class="memname"> <tr> <td class="memname">void sf::Mutex::unlock </td> <td>(</td> <td class="paramname"></td><td>)</td> <td></td> </tr> </table></div><div class="memdoc"><p>Unlock the mutex. </p><dl class="section see"><dt>See Also</dt><dd><a class="el" href="classsf_1_1Mutex.htm#a1a16956a6bbea764480c1b80f2e45763" title="Lock the mutex.">lock</a> </dd></dl></div></div><hr/>The documentation for this class was generated from the following file:<ul><li><a class="el" href="Mutex_8hpp_source.htm">Mutex.hpp</a></li></ul></div><!-- contents --> </div> <div id="footer-container"> <div id="footer"> Copyright � Laurent Gomila :: Documentation generated by <a href="http://www.doxygen.org/" title="doxygen website">doxygen</a> :: </div> </div> <script> (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o), m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m) })(window,document,'script','//www.google-analytics.com/analytics.js','ga'); ga('create', 'UA-41898676-1', 'srchub.org'); ga('send', 'pageview'); |
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