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==Producer and consumer and QSemaphore==

<source lang="cpp">
Foundations of Qt Development\Chapter12\semaphorethreads\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 <QtDebug>
const int bufferSize = 20;
QChar buffer[ bufferSize ];
QSemaphore freeSpace( bufferSize );
QSemaphore availableData( 0 );
bool atEnd = false;
class TextProducer : public QThread
{
public:
TextProducer( QString text );

void run();

private:
QString m_text;
};
TextProducer::TextProducer( QString text ) : QThread()
{
m_text = text;
}
void TextProducer::run()
{
for( int i=0; i<m_text.length(); ++i )
{
freeSpace.acquire();
buffer[ i % bufferSize ] = m_text.data()[ i ];
if( i == m_text.length()-1 )
atEnd = true;
availableData.release();
}
}
class TextConsumer : public QThread
{
public:
void run();
};
void TextConsumer::run()
{
int i = 0;

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

TextProducer producer( "Lorem ipsum dolor sit amet, "
"consectetuer adipiscing elit. "
"Praesent tortor." );
TextConsumer consumer;

producer.start();
consumer.start();

producer.wait();
consumer.wait();

return 0;
}

</source>

==QSemaphore demo==

<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];
QSemaphore freeBytes(BufferSize);
QSemaphore usedBytes;

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) {
freeBytes.acquire();
buffer[i % BufferSize] = "ACGT"[(int)qrand() % 4];
usedBytes.release();
}
}

class Consumer : public QThread

{
public:
void run();
};
void Consumer::run()
{
for (int i = 0; i < DataSize; ++i) {
usedBytes.acquire();
fprintf(stderr, "%c", buffer[i % BufferSize]);
freeBytes.release();
}
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>

==Using QSemaphore==

<source lang="cpp">
Foundations of Qt Development\Chapter12\basicsemaphore\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 <QSemaphore>
int main( int argc, char *argv )
{
QSemaphore s( 10 );

s.acquire(); // s.available() = 9
s.acquire(5); // s.available() = 4
s.release(2); // s.available() = 6
s.release(); // s.available() = 7
s.release(5); // s.available() = 12
s.tryAcquire(15); // s.available() = 12
return 0;
}

</source>

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в 14:21, 25 мая 2010

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