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diff --git a/doc/html/qwaitcondition.html b/doc/html/qwaitcondition.html new file mode 100644 index 0000000..a2735ec --- /dev/null +++ b/doc/html/qwaitcondition.html @@ -0,0 +1,197 @@ +<!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/qwaitcondition_unix.cpp:57 --> +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> +<title>QWaitCondition 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>QWaitCondition Class Reference</h1> + +<p>The QWaitCondition class allows waiting/waking for conditions between threads. +<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="qwaitcondition-h.html">qwaitcondition.h</a>></tt> +<p><a href="qwaitcondition-members.html">List of all member functions.</a> +<h2>Public Members</h2> +<ul> +<li class=fn><a href="#QWaitCondition"><b>QWaitCondition</b></a> ()</li> +<li class=fn>virtual <a href="#~QWaitCondition"><b>~QWaitCondition</b></a> ()</li> +<li class=fn>bool <a href="#wait"><b>wait</b></a> ( unsigned long time = ULONG_MAX )</li> +<li class=fn>bool <a href="#wait-2"><b>wait</b></a> ( QMutex * mutex, unsigned long time = ULONG_MAX )</li> +<li class=fn>void <a href="#wakeOne"><b>wakeOne</b></a> ()</li> +<li class=fn>void <a href="#wakeAll"><b>wakeAll</b></a> ()</li> +</ul> +<hr><a name="details"></a><h2>Detailed Description</h2> + + + +The QWaitCondition class allows waiting/waking for conditions between threads. +<p> + +<p> QWaitConditions allow a thread to tell other threads that some +sort of condition has been met; one or many threads can block +waiting for a QWaitCondition to set a condition with <a href="#wakeOne">wakeOne</a>() or +<a href="#wakeAll">wakeAll</a>(). Use wakeOne() to wake one randomly selected event or +wakeAll() to wake them all. For example, say we have three tasks +that should be performed every time the user presses a key; each +task could be split into a thread, each of which would have a +run() body like this: +<p> <pre> + QWaitCondition key_pressed; + + for (;;) { + key_pressed.<a href="#wait">wait</a>(); // This is a QWaitCondition global variable + // Key was pressed, do something interesting + do_something(); + } + </pre> + +<p> A fourth thread would read key presses and wake the other three +threads up every time it receives one, like this: +<p> <pre> + QWaitCondition key_pressed; + + for (;;) { + getchar(); + // Causes any thread in key_pressed.<a href="#wait">wait</a>() to return from + // that method and continue processing + key_pressed.<a href="#wakeAll">wakeAll</a>(); + } + </pre> + +<p> Note that the order the three threads are woken up in is +undefined, and that if some or all of the threads are still in +do_something() when the key is pressed, they won't be woken up +(since they're not waiting on the condition variable) and so the +task will not be performed for that key press. This can be +avoided by, for example, doing something like this: +<p> <pre> + <a href="qmutex.html">QMutex</a> mymutex; + QWaitCondition key_pressed; + int mycount=0; + + // Worker thread code + for (;;) { + key_pressed.<a href="#wait">wait</a>(); // This is a QWaitCondition global variable + mymutex.<a href="qmutex.html#lock">lock</a>(); + mycount++; + mymutex.<a href="qmutex.html#unlock">unlock</a>(); + do_something(); + mymutex.<a href="qmutex.html#lock">lock</a>(); + mycount--; + mymutex.<a href="qmutex.html#unlock">unlock</a>(); + } + + // Key reading thread code + for (;;) { + getchar(); + mymutex.<a href="qmutex.html#lock">lock</a>(); + // Sleep until there are no busy worker threads + while( mycount > 0 ) { + mymutex.<a href="qmutex.html#unlock">unlock</a>(); + sleep( 1 ); + mymutex.<a href="qmutex.html#lock">lock</a>(); + } + mymutex.<a href="qmutex.html#unlock">unlock</a>(); + key_pressed.<a href="#wakeAll">wakeAll</a>(); + } + </pre> + +<p> The mutexes are necessary because the results of two threads +attempting to change the value of the same variable simultaneously +are unpredictable. +<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="QWaitCondition"></a>QWaitCondition::QWaitCondition () +</h3> +Constructs a new event signalling, i.e. wait condition, object. + +<h3 class=fn><a name="~QWaitCondition"></a>QWaitCondition::~QWaitCondition ()<tt> [virtual]</tt> +</h3> +Deletes the event signalling, i.e. wait condition, object. + +<h3 class=fn>bool <a name="wait"></a>QWaitCondition::wait ( unsigned long time = ULONG_MAX ) +</h3> +Wait on the thread event object. The thread calling this will +block until either of these conditions is met: +<ul> +<li> Another thread signals it using <a href="#wakeOne">wakeOne</a>() or <a href="#wakeAll">wakeAll</a>(). This +function will return TRUE in this case. +<li> <em>time</em> milliseconds has elapsed. If <em>time</em> is ULONG_MAX (the +default), then the wait will never timeout (the event must be +signalled). This function will return FALSE if the wait timed +out. +</ul> +<p> <p>See also <a href="#wakeOne">wakeOne</a>() and <a href="#wakeAll">wakeAll</a>(). + +<h3 class=fn>bool <a name="wait-2"></a>QWaitCondition::wait ( <a href="qmutex.html">QMutex</a> * mutex, unsigned long time = ULONG_MAX ) +</h3> +This is an overloaded member function, provided for convenience. It behaves essentially like the above function. +<p> Release the locked <em>mutex</em> and wait on the thread event object. +The <em>mutex</em> must be initially locked by the calling thread. If <em>mutex</em> is not in a locked state, this function returns immediately. +If <em>mutex</em> is a recursive mutex, this function returns +immediately. The <em>mutex</em> will be unlocked, and the calling thread +will block until either of these conditions is met: +<ul> +<li> Another thread signals it using <a href="#wakeOne">wakeOne</a>() or <a href="#wakeAll">wakeAll</a>(). This +function will return TRUE in this case. +<li> <em>time</em> milliseconds has elapsed. If <em>time</em> is ULONG_MAX (the +default), then the wait will never timeout (the event must be +signalled). This function will return FALSE if the wait timed +out. +</ul> +<p> The mutex will be returned to the same locked state. This function +is provided to allow the atomic transition from the locked state +to the wait state. +<p> <p>See also <a href="#wakeOne">wakeOne</a>() and <a href="#wakeAll">wakeAll</a>(). + +<h3 class=fn>void <a name="wakeAll"></a>QWaitCondition::wakeAll () +</h3> +This wakes all threads waiting on the QWaitCondition. The order in +which the threads are woken up depends on the operating system's +scheduling policies, and cannot be controlled or predicted. +<p> <p>See also <a href="#wakeOne">wakeOne</a>(). + +<h3 class=fn>void <a name="wakeOne"></a>QWaitCondition::wakeOne () +</h3> +This wakes one thread waiting on the QWaitCondition. The thread +that is woken up depends on the operating system's scheduling +policies, and cannot be controlled or predicted. +<p> <p>See also <a href="#wakeAll">wakeAll</a>(). + +<!-- 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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