1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Use</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="ext_concurrency.html" title="Chapter��29.��Concurrency" /><link rel="prev" href="ext_concurrency_impl.html" title="Implementation" /><link rel="next" href="appendix.html" title="Part��IV.�� Appendices" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Use</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ext_concurrency_impl.html">Prev</a>��</td><th width="60%" align="center">Chapter��29.��Concurrency</th><td width="20%" align="right">��<a accesskey="n" href="appendix.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.concurrency.use"></a>Use</h2></div></div></div><p>Typical usage of the last two constructs is demonstrated as follows: 3</p><pre class="programlisting"> 4#include <ext/concurrence.h> 5 6namespace 7{ 8 __gnu_cxx::__mutex safe_base_mutex; 9} // anonymous namespace 10 11namespace other 12{ 13 void 14 foo() 15 { 16 __gnu_cxx::__scoped_lock sentry(safe_base_mutex); 17 for (int i = 0; i < max; ++i) 18 { 19 _Safe_iterator_base* __old = __iter; 20 __iter = __iter-<_M_next; 21 __old-<_M_detach_single(); 22 } 23} 24</pre><p>In this sample code, an anonymous namespace is used to keep 25the <code class="code">__mutex</code> private to the compilation unit, 26and <code class="code">__scoped_lock</code> is used to guard access to the critical 27section within the for loop, locking the mutex on creation and freeing 28the mutex as control moves out of this block. 29</p><p>Several exception classes are used to keep track of 30concurrence-related errors. These classes 31are: <code class="code">__concurrence_lock_error</code>, <code class="code">__concurrence_unlock_error</code>, <code class="code">__concurrence_wait_error</code>, 32and <code class="code">__concurrence_broadcast_error</code>. 33</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_concurrency_impl.html">Prev</a>��</td><td width="20%" align="center"><a accesskey="u" href="ext_concurrency.html">Up</a></td><td width="40%" align="right">��<a accesskey="n" href="appendix.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Implementation��</td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top">��Part��IV.�� 34 Appendices 35</td></tr></table></div></body></html>