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==Extends QThread to create thread==

<source lang="cpp">

Foundations of Qt Development\Chapter12\inorderthreads\main.cpp
/*
* Copyright (c) 2006-2007, Johan Thelin
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* * Neither the name of APress nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include <QApplication>
#include <QThread>
#include <QMutex>
#include <QMessageBox>
#include <QtDebug>
class TextThread : public QThread
{
public:
TextThread( QString text );

void run();

private:
QString m_text;
};
bool stopThreads = false;
TextThread::TextThread( QString text ) : QThread()
{
m_text = text;
}
QMutex mutex;
void TextThread::run()
{
while( !stopThreads )
{
mutex.lock();
if( stopThreads )
return;

qDebug() << m_text;
sleep( 1 );
mutex.unlock();
}
}
int main( int argc, char **argv )
{
QApplication app( argc, argv );

TextThread foo( "Foo" ), bar( "Bar" );

foo.start();
bar.start();

QMessageBox::information( 0, "Threading", "Close me to stop!" );

stopThreads = true;

foo.wait();
bar.wait();

return 0;
}

</source>

==Producer and consumer by Qt thread==

<source lang="cpp">

Foundations of Qt Development\Chapter12\competingsemaphore\main.cpp
/*
* Copyright (c) 2006-2007, Johan Thelin
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* * Neither the name of APress nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include <QApplication>
#include <QThread>
#include <QSemaphore>
#include <QMutex>
#include <QtDebug>
const int bufferSize = 20;
QChar buffer[ bufferSize ];
QSemaphore freeSpace( bufferSize );
QSemaphore availableData( 0 );
QSemaphore atEnd( 0 );
class TextProducer : public QThread
{
public:
TextProducer( QString text );

void run();

private:
QString m_text;
};
TextProducer::TextProducer( QString text ) : QThread()
{
atEnd.release();
m_text = text;
}
void TextProducer::run()
{
static int index = 0;
static QMutex indexMutex;

for( int i=0; i<m_text.length(); ++i )
{
freeSpace.acquire();
indexMutex.lock();
buffer[ index++ % bufferSize ] = m_text.data()[ i ];
indexMutex.unlock();

if( i == m_text.length()-1 )
atEnd.acquire();

availableData.release();
}
}
class TextConsumer : public QThread
{
public:
void run();
};
void TextConsumer::run()
{
int i = 0;

while( atEnd.available() || availableData.available() )
{
availableData.acquire();
qDebug() << buffer[ i ];
i = (i+1) % bufferSize;
freeSpace.release();
}
}
int main( int argc, char **argv )
{
QApplication app( argc, argv );

TextProducer p1( "this text is written using lower case characters."
"it will compete with a text written using upper case characters." );
TextProducer p2( "THIS TEXT IS WRITTEN USING UPPER CASE CHARACTERS!"
"IT WILL COMPETE WITH A TEXT WRITTEN USING LOWER CASE CHARACTERS!" );
TextConsumer consumer;

p1.start();
p2.start();
consumer.start();

p1.wait();
p2.wait();
consumer.wait();

return 0;
}

</source>

==Thread sleeps==

<source lang="cpp">
Foundations of Qt Development\Chapter12\simplethreads\main.cpp
/*
* Copyright (c) 2006-2007, Johan Thelin
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* * Neither the name of APress nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include <QApplication>
#include <QThread>
#include <QMessageBox>
#include <QtDebug>
class TextThread : public QThread
{
public:
TextThread( QString text );

void run();

private:
QString m_text;
};
bool stopThreads = false;
TextThread::TextThread( QString text ) : QThread()
{
m_text = text;
}
void TextThread::run()
{
while( !stopThreads )
{
qDebug() << m_text;
sleep( 1 );
}
}
int main( int argc, char **argv )
{
QApplication app( argc, argv );

TextThread foo( "Foo" ), bar( "Bar" );

foo.start();
bar.start();

QMessageBox::information( 0, "Threading", "Close me to stop!" );

stopThreads = true;

foo.wait();
bar.wait();

return 0;
}

</source>

==Using QThread==

<source lang="cpp">
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights. These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
#include <QThread>

class MyThread : public QThread
{
Q_OBJECT
protected:
void run();
};

#include <QCache>
#include <QMutex>
#include <QThreadStorage>
#include "threads.h"

void MyThread::run()

{

}

#define Counter ReentrantCounter

class Counter

{
public:
Counter() { n = 0; }
void increment() { ++n; }
void decrement() { --n; }
int value() const { return n; }
private:
int n;
};

#undef Counter
#define Counter ThreadSafeCounter

class Counter

{
public:
Counter() { n = 0; }
void increment() { QMutexLocker locker(&mutex); ++n; }
void decrement() { QMutexLocker locker(&mutex); --n; }
int value() const { QMutexLocker locker(&mutex); return n; }
private:
mutable QMutex mutex;
int n;
};

typedef int SomeClass;

QThreadStorage<QCache<QString, SomeClass> *> caches;
void cacheObject(const QString &key, SomeClass *object)

{
if (!caches.hasLocalData())
caches.setLocalData(new QCache<QString, SomeClass>);
caches.localData()->insert(key, object);
}
void removeFromCache(const QString &key)

{
if (!caches.hasLocalData())
return;
caches.localData()->remove(key);
}

int main()
{
return 0;
}

</source>

==Wait condition==

<source lang="cpp">
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the examples of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights. These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
#include <QtCore>
#include <stdio.h>
#include <stdlib.h>

const int DataSize = 100000;
const int BufferSize = 8192;
char buffer[BufferSize];
QWaitCondition bufferNotEmpty;
QWaitCondition bufferNotFull;
QMutex mutex;
int numUsedBytes = 0;

class Producer : public QThread

{
public:
void run();
};
void Producer::run()
{
qsrand(QTime(0,0,0).secsTo(QTime::currentTime()));

for (int i = 0; i < DataSize; ++i) {
mutex.lock();
if (numUsedBytes == BufferSize)
bufferNotFull.wait(&mutex);
mutex.unlock();
buffer[i % BufferSize] = "ACGT"[(int)qrand() % 4];
mutex.lock();
++numUsedBytes;
bufferNotEmpty.wakeAll();
mutex.unlock();
}
}

class Consumer : public QThread

{
public:
void run();
};
void Consumer::run()
{
for (int i = 0; i < DataSize; ++i) {
mutex.lock();
if (numUsedBytes == 0)
bufferNotEmpty.wait(&mutex);
mutex.unlock();
fprintf(stderr, "%c", buffer[i % BufferSize]);
mutex.lock();
--numUsedBytes;
bufferNotFull.wakeAll();
mutex.unlock();
}
fprintf(stderr, "\n");
}

int main(int argc, char *argv[])

{
QCoreApplication app(argc, argv);
Producer producer;
Consumer consumer;
producer.start();
consumer.start();
producer.wait();
consumer.wait();
return 0;
}

</source>

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