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<html><!-- #BeginTemplate "/Templates/tmpl.dwt" --><head><!-- #BeginEditable "doctitle" --> <title>PTypes: multithreading: trigger</title><!-- #EndEditable --> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link rel="stylesheet" href="styles.css"></head><body bgcolor="#FFFFFF" leftmargin="40" marginwidth="40"><p><a href="../index.html"><img src="title-1.7.gif" width="213" height="34" alt="C++ Portable Types Library (PTypes) Version 1.7" border="0"></a> <hr noshade><!-- #BeginEditable "body" --> <p class="hpath"><a href="index.html">Top</a>: <a href="async.html">Multithreading</a>: trigger</p><blockquote> <pre class="lang">#include <pasync.h>trigger::trigger(bool autoreset, bool initstate);void trigger::wait();void trigger::post();void trigger::signal(); <span class="comment">// alias for post()</span>void trigger::reset();</pre></blockquote><p><span class="lang">Trigger</span> is a simple synchronization object typically used to notify one or more threads about some event. Trigger can be viewed as a simplified semaphore, which has only two states and does not count the number of wait's and post's. Multiple threads can wait for an event to occur; either one thread or all threads waiting on a trigger are being released as soon as some other thread signals the <span class="lang">trigger</span> object. Auto-reset triggers release only one thread each time <span class="lang">post()</span> is called, and manual-reset triggers release all waiting threads at once. <span class="lang">Trigger</span> mimics the Win32 Event object.</p><p><span class="def">trigger::trigger(bool autoreset, bool initstate)</span> creates a trigger object with the initial state <span class="lang">initstate</span>. The <span class="lang">autoreset</span> feature defines whether the trigger object will automatically reset its state back to non-signaled when <span class="lang">post()</span> is called.</p><p><span class="def">void trigger::wait()</span> waits until the state of the trigger object becomes signaled, or returns immediately if the object is in signaled state already.</p><p><span class="def">void trigger::post()</span> signals the trigger object. If this is an auto-reset trigger, only one thread will be released and the state of the object will be set to non-signaled. If this is a manual-reset trigger, the state of the object is set to signaled and all threads waiting on the object are being released. Subsequent calls to <span class="lang">wait()</span> from any number of concurrent threads will return immediately.</p><p> <span class="def">void trigger::signal()</span> is an alias for <span class="lang">post()</span>.</p><p><span class="def">void trigger::reset()</span> resets the state of the trigger object to non-signaled.</p><p class="seealso">See also: <a href="async.thread.html">thread</a>, <a href="async.mutex.html">mutex</a>, <a href="async.rwlock.html">rwlock</a>, <a href="async.semaphore.html">semaphore</a>, <a href="async.examples.html">Examples</a></p><!-- #EndEditable --><hr size="1"><a href="../index.html" class="ns">PTypes home</a></body><!-- #EndTemplate --></html>?? 快捷鍵說明
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