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| author | Timothy Pearson <kb9vqf@pearsoncomputing.net> | 2011-07-10 15:24:15 -0500 |
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| committer | Timothy Pearson <kb9vqf@pearsoncomputing.net> | 2011-07-10 15:24:15 -0500 |
| commit | bd0f3345a938b35ce6a12f6150373b0955b8dd12 (patch) | |
| tree | 7a520322212d48ebcb9fbe1087e7fca28b76185c /doc/html/qsemaphore.html | |
| download | qt3-bd0f3345a938b35ce6a12f6150373b0955b8dd12.tar.gz qt3-bd0f3345a938b35ce6a12f6150373b0955b8dd12.zip | |
Add Qt3 development HEAD version
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| -rw-r--r-- | doc/html/qsemaphore.html | 149 |
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diff --git a/doc/html/qsemaphore.html b/doc/html/qsemaphore.html new file mode 100644 index 0000000..d789229 --- /dev/null +++ b/doc/html/qsemaphore.html @@ -0,0 +1,149 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> +<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/src/tools/qsemaphore.cpp:45 --> +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> +<title>QSemaphore Class</title> +<style type="text/css"><!-- +fn { margin-left: 1cm; text-indent: -1cm; } +a:link { color: #004faf; text-decoration: none } +a:visited { color: #672967; text-decoration: none } +body { background: #ffffff; color: black; } +--></style> +</head> +<body> + +<table border="0" cellpadding="0" cellspacing="0" width="100%"> +<tr bgcolor="#E5E5E5"> +<td valign=center> + <a href="index.html"> +<font color="#004faf">Home</font></a> + | <a href="classes.html"> +<font color="#004faf">All Classes</font></a> + | <a href="mainclasses.html"> +<font color="#004faf">Main Classes</font></a> + | <a href="annotated.html"> +<font color="#004faf">Annotated</font></a> + | <a href="groups.html"> +<font color="#004faf">Grouped Classes</font></a> + | <a href="functions.html"> +<font color="#004faf">Functions</font></a> +</td> +<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>QSemaphore Class Reference</h1> + +<p>The QSemaphore class provides a robust integer semaphore. +<a href="#details">More...</a> +<p>All the functions in this class are <a href="threads.html#threadsafe">thread-safe</a> when Qt is built with thread support.</p> +<p><tt>#include <<a href="qsemaphore-h.html">qsemaphore.h</a>></tt> +<p><a href="qsemaphore-members.html">List of all member functions.</a> +<h2>Public Members</h2> +<ul> +<li class=fn><a href="#QSemaphore"><b>QSemaphore</b></a> ( int maxcount )</li> +<li class=fn>virtual <a href="#~QSemaphore"><b>~QSemaphore</b></a> ()</li> +<li class=fn>int <a href="#available"><b>available</b></a> () const</li> +<li class=fn>int <a href="#total"><b>total</b></a> () const</li> +<li class=fn>int <a href="#operator++"><b>operator++</b></a> ( int )</li> +<li class=fn>int <a href="#operator--"><b>operator--</b></a> ( int )</li> +<li class=fn>int <a href="#operator+-eq"><b>operator+=</b></a> ( int n )</li> +<li class=fn>int <a href="#operator--eq"><b>operator-=</b></a> ( int n )</li> +<li class=fn>bool <a href="#tryAccess"><b>tryAccess</b></a> ( int n )</li> +</ul> +<hr><a name="details"></a><h2>Detailed Description</h2> + + + +The QSemaphore class provides a robust integer semaphore. +<p> + +<p> A QSemaphore can be used to serialize thread execution, in a +similar way to a <a href="qmutex.html">QMutex</a>. A semaphore differs from a mutex, in +that a semaphore can be accessed by more than one thread at a +time. +<p> For example, suppose we have an application that stores data in a +large tree structure. The application creates 10 threads +(commonly called a thread pool) to perform searches on the tree. +When the application searches the tree for some piece of data, it +uses one thread per base node to do the searching. A semaphore +could be used to make sure that two threads don't try to search +the same branch of the tree at the same time. +<p> A non-computing example of a semaphore would be dining at a +restuarant. A semaphore is initialized to have a maximum count +equal to the number of chairs in the restuarant. As people +arrive, they want a seat. As seats are filled, the semaphore is +accessed, once per person. As people leave, the access is +released, allowing more people to enter. If a party of 10 people +want to be seated, but there are only 9 seats, those 10 people +will wait, but a party of 4 people would be seated (taking the +available seats to 5, making the party of 10 people wait longer). +<p> When a semaphore is created it is given a number which is the +maximum number of concurrent accesses it will permit. Accesses to +the sempahore are gained using <a href="#operator++">operator++</a>() or <a href="#operator+-eq">operator+=</a>(), and +released with <a href="#operator--">operator--</a>() or <a href="#operator--eq">operator-=</a>(). The number of +accesses allowed is retrieved with <a href="#available">available</a>(), and the total +number with <a href="#total">total</a>(). Note that the incrementing functions will +block if there aren't enough available accesses. Use <a href="#tryAccess">tryAccess</a>() +if you want to acquire accesses without blocking. +<p>See also <a href="environment.html">Environment Classes</a> and <a href="thread.html">Threading</a>. + +<hr><h2>Member Function Documentation</h2> +<h3 class=fn><a name="QSemaphore"></a>QSemaphore::QSemaphore ( int maxcount ) +</h3> +Creates a new semaphore. The semaphore can be concurrently +accessed at most <em>maxcount</em> times. + +<h3 class=fn><a name="~QSemaphore"></a>QSemaphore::~QSemaphore ()<tt> [virtual]</tt> +</h3> +Destroys the semaphore. +<p> <b>Warning:</b> If you destroy a semaphore that has accesses in use the +resultant behavior is undefined. + +<h3 class=fn>int <a name="available"></a>QSemaphore::available () const +</h3> +Returns the number of accesses currently available to the +semaphore. + +<h3 class=fn>int <a name="operator++"></a>QSemaphore::operator++ ( int ) +</h3> +Postfix ++ operator. +<p> Try to get access to the semaphore. If <a href="#available">available</a>() == 0, this +call will block until it can get access, i.e. until <a href="#available">available</a>() > +0. + +<h3 class=fn>int <a name="operator+-eq"></a>QSemaphore::operator+= ( int n ) +</h3> +Try to get access to the semaphore. If <a href="#available">available</a>() < <em>n</em>, this +call will block until it can get all the accesses it wants, i.e. +until <a href="#available">available</a>() >= <em>n</em>. + +<h3 class=fn>int <a name="operator--"></a>QSemaphore::operator-- ( int ) +</h3> +Postfix -- operator. +<p> Release access of the semaphore. This wakes all threads waiting +for access to the semaphore. + +<h3 class=fn>int <a name="operator--eq"></a>QSemaphore::operator-= ( int n ) +</h3> +Release <em>n</em> accesses to the semaphore. + +<h3 class=fn>int <a name="total"></a>QSemaphore::total () const +</h3> +Returns the total number of accesses to the semaphore. + +<h3 class=fn>bool <a name="tryAccess"></a>QSemaphore::tryAccess ( int n ) +</h3> +Try to get access to the semaphore. If <a href="#available">available</a>() < <em>n</em>, this +function will return FALSE immediately. If <a href="#available">available</a>() >= <em>n</em>, +this function will take <em>n</em> accesses and return TRUE. This +function does <em>not</em> block. + +<!-- eof --> +<hr><p> +This file is part of the <a href="index.html">Qt toolkit</a>. +Copyright © 1995-2007 +<a href="http://www.trolltech.com/">Trolltech</a>. 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