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Qt » My Qt Blocking Queue version
posted on 2010/05/13 23:10

It's strange that Qt framework doesn't have a QBlockingQueue implementation... So i have taken the QQueue, some QtConcurrent stuff and 10 minutes of my free lazy time pinch
So,  that's all!
 
#ifndef BLOCKINGQUEUE_H
#define BLOCKINGQUEUE_H
 
#include <QQueue>
#include <QMutex>
#include <QWaitCondition>



/*!
    @brief A Blocking Queue implementation
    @author Alessio 'Slux' Di Fazio
*/
template class BlockingQueue
{

private:
    QQueue queue;
    QMutex enqueueSerialAccess, dequeueWaitConditionLocker;
    QWaitCondition waitBlockingQueueAccess;

public:
    /*! Empty constructor */
    inline BlockingQueue() {}

    /*! Empty destructor */
    inline ~BlockingQueue() {};

    /*! enqueue thread safe function that wake one blocked thread that wait for dequeue. */
    inline void enqueue(const T &t)
    {
        QMutexLocker locker(&enqueueSerialAccess);

        queue.enqueue(t);
        waitBlockingQueueAccess.wakeOne();
    }

    /*! blocking queue thread safe function that block the thread if the queue is empty. */
    inline T dequeue()
    {
        dequeueWaitConditionLocker.lock();

        if (queue.isEmpty())
            waitBlockingQueueAccess.wait(&dequeueWaitConditionLocker);

        T returnVal = queue.dequeue();

        dequeueWaitConditionLocker.unlock();

        return returnVal;
    }

};

#endif // BLOCKINGQUEUE_H
 

 

And if you want to test the blocking queue...

#include <QtCore>
#include "BlockingQueue.h"

BlockingQueue blockingQueue;

class Producer : public QThread

{

public:

    QString threadName;

    Producer(const QString &name) {threadName = name;}

 

protected:

    virtual void run()

    {

        qDebug() << "Producer" << threadName << "started.";

        for(int i=0; i<100; ++i)

        {

            msleep(5);

            QString val = threadName;

            val.append(" -> ");

            val.append(QString::number(i));

            blockingQueue.enqueue(val);

        }

    }

};

class Consumer : public QThread

{

protected:

    virtual void run()

    {

        qDebug() << "Consumer started.";

        Q_FOREVER

        {

            qDebug() << "Readed queque value: " << blockingQueue.dequeue();

        }

    }

};

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

{

    QCoreApplication a(argc, argv);

    Consumer *consumer = new Consumer();

    consumer->start();

    for (int i=0; i<100; ++i)

    {

        Producer *p = new Producer(QString::number(i).prepend("PROD "));

        p->start();

    }

    return a.exec();

}

 
Slux :) 
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