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<title>Class Poco::Semaphore</title>
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<h1 class="namespace"><a href="Poco.html" class="namespace">Poco</a></h1>
<h1 class="symbol">class Semaphore</h1>
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<p>
<b>Library:</b> Foundation<br />
<b>Package:</b> Threading<br />
<b>Header:</b> Poco/Semaphore.h</p>
<h2>Description</h2>
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<p>A <a href="Poco.Semaphore.html" title="class Poco::Semaphore">Semaphore</a> is a synchronization object with the following characteristics: A semaphore has a value that is constrained to be a non-negative integer and two atomic operations. The allowable operations are V (here called <a href="Poco.Semaphore.html#9892" title="Poco::Semaphore::set()">set</a>()) and P (here called <a href="Poco.Semaphore.html#9893" title="Poco::Semaphore::wait()">wait</a>()). A V (<a href="Poco.Semaphore.html#9892" title="Poco::Semaphore::set()">set</a>()) operation increases the value of the semaphore by one. A P (<a href="Poco.Semaphore.html#9893" title="Poco::Semaphore::wait()">wait</a>()) operation decreases the value of the semaphore by one, provided that can be done without violating the constraint that the value be non-negative. A P (<a href="Poco.Semaphore.html#9893" title="Poco::Semaphore::wait()">wait</a>()) operation that is initiated when the value of the semaphore is 0 suspends the calling thread. The calling thread may continue when the value becomes positive again. </p>
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<h2>Inheritance</h2>
<p><b>Direct Base Classes: </b>SemaphoreImpl</p>
<p><b>All Base Classes: </b>SemaphoreImpl</p>
<h2>Member Summary</h2>
<p><b>Member Functions: </b><a href="Poco.Semaphore.html#9892" title="Poco::Semaphore::set()">set</a>, <a href="Poco.Semaphore.html#9896" title="Poco::Semaphore::tryWait()">tryWait</a>, <a href="Poco.Semaphore.html#9893" title="Poco::Semaphore::wait()">wait</a></p>
<h2>Constructors</h2>
<h3><a name="9886">Semaphore</a></h3>
<p class="decl"><a href="Poco.Semaphore.html" title="class Poco::Semaphore">Semaphore</a>(<br /> int n<br />);</p>
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<p></p>
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<h3><a name="9888">Semaphore</a></h3>
<p class="decl"><a href="Poco.Semaphore.html" title="class Poco::Semaphore">Semaphore</a>(<br /> int n,<br /> int max<br />);</p>
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<p>Creates the semaphore. The current value of the semaphore is given in n. The maximum value of the semaphore is given in max. If only n is given, it must be greater than zero. If both n and max are given, max must be greater than zero, n must be greater than or equal to zero and less than or equal to max. </p>
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<h2>Destructor</h2>
<h3><a name="9891">~Semaphore</a></h3>
<p class="decl">~<a href="Poco.Semaphore.html" title="class Poco::Semaphore">Semaphore</a>();</p>
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<p>Destroys the semaphore. </p>
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<h2>Member Functions</h2>
<h3><a name="9892">set</a> <img src="images/inline.gif" alt="inline" title="inline" style="vertical-align:baseline;" border="0" /> </h3>
<p class="decl">void set();</p>
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<p>Increments the semaphore's value by one and thus signals the semaphore. Another thread waiting for the semaphore will be able to continue. </p>
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<h3><a name="9896">tryWait</a> <img src="images/inline.gif" alt="inline" title="inline" style="vertical-align:baseline;" border="0" /> </h3>
<p class="decl">bool tryWait(<br /> long milliseconds<br />);</p>
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<p>Waits for the semaphore to become signalled. To become signalled, a semaphore's value must be greater than zero. Returns true if the semaphore became signalled within the specified time interval, false otherwise. Decrements the semaphore's value by one if successful. </p>
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<h3><a name="9893">wait</a> <img src="images/inline.gif" alt="inline" title="inline" style="vertical-align:baseline;" border="0" /> </h3>
<p class="decl">void wait();</p>
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<p>Waits for the semaphore to become signalled. To become signalled, a semaphore's value must be greater than zero. Decrements the semaphore's value by one. </p>
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<h3><a name="9894">wait</a></h3>
<p class="decl">void wait(<br /> long milliseconds<br />);</p>
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<p>Waits for the semaphore to become signalled. To become signalled, a semaphore's value must be greater than zero. Throws a <a href="Poco.TimeoutException.html" title="class Poco::TimeoutException">TimeoutException</a> if the semaphore does not become signalled within the specified time interval. Decrements the semaphore's value by one if successful. </p>
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<p class="footer">POCO C++ Libraries 1.3.6-all<br />
Copyright © 2009, <a href="http://pocoproject.org/" target="_blank">Applied Informatics Software Engineering GmbH and Contributors</a></p>
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