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