Qt Reference Documentation

# waitconditions.cpp Example File

threads/waitconditions/waitconditions.cpp

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     ** This file is part of the examples of the Qt Toolkit.
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     #include <QtGui>

     #include <stdio.h>
     #include <stdlib.h>

     #ifdef Q_WS_S60
     const int DataSize = 300;
     #else
     const int DataSize = 100000;
     #endif

     const int BufferSize = 8192;
     char buffer[BufferSize];

     QWaitCondition bufferNotEmpty;
     QWaitCondition bufferNotFull;
     QMutex mutex;
     int numUsedBytes = 0;

     class Producer : public QThread
     {
     public:
         Producer(QObject *parent = NULL) : QThread(parent)
         {
         }

         void 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
     {
         Q_OBJECT
     public:
         Consumer(QObject *parent = NULL) : QThread(parent)
         {
         }

         void run()
         {
             for (int i = 0; i < DataSize; ++i) {
                 mutex.lock();
                 if (numUsedBytes == 0)
                     bufferNotEmpty.wait(&mutex);
                 mutex.unlock();

         #ifdef Q_WS_S60
                 emit stringConsumed(QString(buffer[i % BufferSize]));
         #else
                 fprintf(stderr, "%c", buffer[i % BufferSize]);
         #endif

                 mutex.lock();
                 --numUsedBytes;
                 bufferNotFull.wakeAll();
                 mutex.unlock();
             }
             fprintf(stderr, "\n");
         }

     signals:
         void stringConsumed(const QString &text);
     };

     #ifdef Q_WS_S60
     class PlainTextEdit : public QPlainTextEdit
     {
         Q_OBJECT
     public:
         PlainTextEdit(QWidget *parent = NULL) : QPlainTextEdit(parent), producer(NULL), consumer(NULL)
         {
             setTextInteractionFlags(Qt::NoTextInteraction);

             producer = new Producer(this);
             consumer = new Consumer(this);

             QObject::connect(consumer, SIGNAL(stringConsumed(const QString &)), SLOT(insertPlainText(const QString &)), Qt::BlockingQueuedConnection);

             QTimer::singleShot(0, this, SLOT(startThreads()));
         }

     protected:
         Producer *producer;
         Consumer *consumer;

     protected slots:
         void startThreads()
         {
             producer->start();
             consumer->start();
         }
     };
     #endif

     int main(int argc, char *argv[])
     {
     #ifdef Q_WS_S60
         QApplication app(argc, argv);

         PlainTextEdit console;
         console.showMaximized();

         return app.exec();
     #else
         QCoreApplication app(argc, argv);
         Producer producer;
         Consumer consumer;
         producer.start();
         consumer.start();
         producer.wait();
         consumer.wait();
         return 0;
     #endif
     }

     #include "waitconditions.moc"