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that use it are valid. Merged revisions 53047-53048 via svnmerge from https://svn.boost.org/svn/boost/trunk ........ r53047 | danieljames | 2009-05-16 15:17:20 +0100 (Sat, 16 May 2009) | 1 line Fix some validation errors. ........ r53048 | danieljames | 2009-05-16 15:23:59 +0100 (Sat, 16 May 2009) | 1 line Use a local copy of the valid HTML 4.01 icon. ........ [SVN r53258]
180 lines
4.2 KiB
HTML
180 lines
4.2 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
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"http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta http-equiv="Content-Language" content="en-us">
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<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
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<link href="../pool.css" rel="stylesheet" type="text/css">
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<title>guard - Auto-lock/unlock-er</title>
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</head>
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<body>
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<img src="../../../../boost.png" width="276" height="86" alt="C++ Boost">
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<h1 align="center">guard - Auto-lock/unlock-er</h1>
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<h2>Introduction</h2>
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<p>detail/guard.hpp provides a type <span class=
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"code">guard<Mutex></span> that allows scoped access to the
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<span class="code">Mutex</span>'s locking and unlocking operations. It is
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used to ensure that a <span class="code">Mutex</span> is unlocked, even if
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an exception is thrown.</p>
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<h2>Synopsis</h2>
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<pre class="code">
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namespace details {
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namespace pool {
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template <typename Mutex>
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class guard
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{
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private:
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guard(const guard &);
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void operator=(const guard &);
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public:
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explicit guard(Mutex & mtx);
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~guard();
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};
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} // namespace pool
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} // namespace details
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</pre>
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<h2>Semantics</h2>
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<table border align="center" summary="">
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<caption>
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<em>Symbol Table</em>
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</caption>
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<tr>
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<th>Symbol</th>
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<th>Meaning</th>
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</tr>
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<tr>
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<td class="code">T</td>
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<td><span class="code">guard<Mutex></span></td>
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</tr>
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<tr>
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<td class="code">m</td>
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<td>value of type <span class="code">Mutex &</span></td>
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</tr>
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<tr>
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<td class="code">g</td>
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<td>value of type <span class="code">guard<Mutex></span></td>
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</tr>
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</table><br>
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<table border align="center" summary="">
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<caption>
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<em>Requirements on <span class="code">Mutex</span></em>
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</caption>
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<tr>
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<th>Expression</th>
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<th>Return Type</th>
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<th>Assertion/Note/Pre/Post-Condition</th>
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</tr>
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<tr>
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<td class="code">m.lock()</td>
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<td>not used</td>
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<td>Locks the mutex referred to by <span class="code">m</span></td>
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</tr>
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<tr>
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<td class="code">m.unlock()</td>
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<td>not used</td>
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<td>Unlocks the mutex referred to by <span class="code">m</span></td>
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</tr>
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</table><br>
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<table border align="center" summary="">
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<caption>
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<em>Requirements satisfied by <span class="code">guard</span></em>
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</caption>
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<tr>
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<th>Expression</th>
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<th>Assertion/Note/Pre/Post-Condition</th>
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</tr>
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<tr>
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<td class="code">T(m)</td>
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<td>Locks the mutex referred to by <span class="code">m</span>; binds
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<span class="code">T(m)</span> to <span class="code">m</span></td>
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</tr>
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<tr>
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<td class="code">(&g)->~T()</td>
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<td>Unlocks the mutex that <span class="code">g</span> is bound to</td>
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</tr>
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</table>
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<h2>Example</h2>
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<p>Given a (platform-specific) <span class="code">mutex</span> class, we
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can wrap code as follows:</p>
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<pre class="code">
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extern mutex global_lock;
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static void f()
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{
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boost::details::pool::guard<mutex> g(global_lock);
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// g's constructor locks "global_lock"
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... // do anything:
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// throw exceptions
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// return
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// or just fall through
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} // g's destructor unlocks "global_lock"
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</pre>
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<h2>Dependencies</h2>
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<p>None.</p>
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<h2>Future Directions</h2>
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<p>This header will eventually be replaced by a Boost multithreading
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library.</p>
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<hr>
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<p><a href="http://validator.w3.org/check?uri=referer"><img border="0" src=
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"../../../../doc/images/valid-html401.png" alt="Valid HTML 4.01 Transitional"
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height="31" width="88"></a></p>
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<p>Revised
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<!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B, %Y" startspan -->05
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December, 2006<!--webbot bot="Timestamp" endspan i-checksum="38516" --></p>
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<p><i>Copyright © 2000, 2001 Stephen Cleary (scleary AT jerviswebb DOT
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com)</i></p>
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<p><i>Distributed under the Boost Software License, Version 1.0. (See
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accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a>
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or copy at <a href=
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"http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</i></p>
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</body>
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</html>
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