diff options
| author | Timothy Pearson <kb9vqf@pearsoncomputing.net> | 2011-07-10 15:24:15 -0500 |
|---|---|---|
| committer | Timothy Pearson <kb9vqf@pearsoncomputing.net> | 2011-07-10 15:24:15 -0500 |
| commit | bd0f3345a938b35ce6a12f6150373b0955b8dd12 (patch) | |
| tree | 7a520322212d48ebcb9fbe1087e7fca28b76185c /doc/html/qmutexlocker.html | |
| download | qt3-bd0f3345a938b35ce6a12f6150373b0955b8dd12.tar.gz qt3-bd0f3345a938b35ce6a12f6150373b0955b8dd12.zip | |
Add Qt3 development HEAD version
Diffstat (limited to 'doc/html/qmutexlocker.html')
| -rw-r--r-- | doc/html/qmutexlocker.html | 220 |
1 files changed, 220 insertions, 0 deletions
diff --git a/doc/html/qmutexlocker.html b/doc/html/qmutexlocker.html new file mode 100644 index 0000000..44eff46 --- /dev/null +++ b/doc/html/qmutexlocker.html @@ -0,0 +1,220 @@ +<!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/qmutex_unix.cpp:511 --> +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> +<title>QMutexLocker 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>QMutexLocker Class Reference</h1> + +<p>The QMutexLocker class simplifies locking and unlocking QMutexes. +<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="qmutex-h.html">qmutex.h</a>></tt> +<p><a href="qmutexlocker-members.html">List of all member functions.</a> +<h2>Public Members</h2> +<ul> +<li class=fn><a href="#QMutexLocker"><b>QMutexLocker</b></a> ( QMutex * mutex )</li> +<li class=fn><a href="#~QMutexLocker"><b>~QMutexLocker</b></a> ()</li> +<li class=fn>QMutex * <a href="#mutex"><b>mutex</b></a> () const</li> +</ul> +<hr><a name="details"></a><h2>Detailed Description</h2> + + +The QMutexLocker class simplifies locking and unlocking QMutexes. +<p> +<p> + +<p> The purpose of QMutexLocker is to simplify <a href="qmutex.html">QMutex</a> locking and +unlocking. Locking and unlocking a QMutex in complex functions and +statements or in exception handling code is error prone and +difficult to debug. QMutexLocker should be used in such situations +to ensure that the state of the mutex is well defined and always +locked and unlocked properly. +<p> QMutexLocker should be created within a function where a QMutex +needs to be locked. The mutex is locked when QMutexLocker is +created, and unlocked when QMutexLocker is destroyed. +<p> For example, this complex function locks a QMutex upon entering +the function and unlocks the mutex at all the exit points: +<p> <pre> + int complexFunction( int flag ) + { + mutex.lock(); + + int return_value = 0; + + switch ( flag ) { + case 0: + case 1: + { + mutex.unlock(); + return moreComplexFunction( flag ); + } + + case 2: + { + int status = anotherFunction(); + if ( status < 0 ) { + mutex.unlock(); + return -2; + } + return_value = status + flag; + break; + } + + default: + { + if ( flag > 10 ) { + mutex.unlock(); + return -1; + } + break; + } + } + + mutex.unlock(); + return return_value; + } + </pre> + +<p> This example function will get more complicated as it is +developed, which increases the likelihood that errors will occur. +<p> Using QMutexLocker greatly simplifies the code, and makes it more +readable: +<p> <pre> + int complexFunction( int flag ) + { + QMutexLocker locker( &mutex ); + + int return_value = 0; + + switch ( flag ) { + case 0: + case 1: + { + return moreComplexFunction( flag ); + } + + case 2: + { + int status = anotherFunction(); + if ( status < 0 ) + return -2; + return_value = status + flag; + break; + } + + default: + { + if ( flag > 10 ) + return -1; + break; + } + } + + return return_value; + } + </pre> + +<p> Now, the mutex will always be unlocked when the QMutexLocker +object is destroyed (when the function returns since <tt>locker</tt> is +an auto variable). Note that the mutex will be unlocked after +the call to moreComplexFunction() in this example, avoiding +possible bugs caused by unlocking the mutex too early, as in +the first example. +<p> The same principle applies to code that throws and catches +exceptions. An exception that is not caught in the function that +has locked the mutex has no way of unlocking the mutex before the +exception is passed up the stack to the calling function. +<p> QMutexLocker also provides a <a href="#mutex">mutex</a>() member function that returns +the mutex on which the QMutexLocker is operating. This is useful +for code that needs access to the mutex, such as +<a href="qwaitcondition.html#wait">QWaitCondition::wait</a>(). For example: +<p> <pre> + class SignalWaiter + { + private: + QMutexLocker locker; + + public: + SignalWaiter( <a href="qmutex.html">QMutex</a> *mutex ) + : locker( mutex ) + { + } + + void waitForSignal() + { + ... + ... + ... + + while ( ! signalled ) + waitcondition.wait( locker.<a href="#mutex">mutex</a>() ); + + ... + ... + ... + } + }; + </pre> + +<p> <p>See also <a href="qmutex.html">QMutex</a>, <a href="qwaitcondition.html">QWaitCondition</a>, <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="QMutexLocker"></a>QMutexLocker::QMutexLocker ( <a href="qmutex.html">QMutex</a> * mutex ) +</h3> + +<p> Constructs a QMutexLocker and locks <em>mutex</em>. The mutex will be +unlocked when the QMutexLocker is destroyed. If <em>mutex</em> is zero, +QMutexLocker does nothing. +<p> <p>See also <a href="qmutex.html#lock">QMutex::lock</a>(). + +<h3 class=fn><a name="~QMutexLocker"></a>QMutexLocker::~QMutexLocker () +</h3> + +<p> Destroys the QMutexLocker and unlocks the mutex which was locked +in the constructor. +<p> <p>See also <a href="#QMutexLocker">QMutexLocker::QMutexLocker</a>() and <a href="qmutex.html#unlock">QMutex::unlock</a>(). + +<h3 class=fn><a href="qmutex.html">QMutex</a> * <a name="mutex"></a>QMutexLocker::mutex () const +</h3> + +<p> Returns a pointer to the mutex which was locked in the +constructor. +<p> <p>See also <a href="#QMutexLocker">QMutexLocker::QMutexLocker</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>. All Rights Reserved.<p><address><hr><div align=center> +<table width=100% cellspacing=0 border=0><tr> +<td>Copyright © 2007 +<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a> +<td align=right><div align=right>Qt 3.3.8</div> +</table></div></address></body> +</html> |