QT多线程中的互斥与同步

参考自《精通qt4编程》。

 

qt为实现线程的同步与互斥，提供了几个类。

下面主要介绍三个类：

一、QMutex和QMutexLocker

class key { public: key(){key = 0;} int createKey(){QMutexLocker locker(&mutex);++key;return key;} int value() const {QMutexLocker locker(&mutex);return key;} private: int key; Qmutex mutex; }; 

二、QSemaphore

#include <QtCore> #include <stdio.h> #include <stdlib.h> const int DataSize = 100000; const int BufferSize = 8192; int buffer[BufferSize]; QSemaphore freeBytes(BufferSize); QSemaphore usedBytes(0); class Producer : public QThread { public: void run(); }; void Producer::run() { for (int i = 0; i < DataSize; ++i) { freeBytes.acquire(); buffer[i % BufferSize] = (i % BufferSize); usedBytes.release(); } } class Consumer : public QThread { public: void run(); }; void Consumer::run() { for (int i = 0; i < DataSize; ++i) { usedBytes.acquire(); fprintf(stderr, "%d ", buffer[i % BufferSize]); if(i % 16 ==0 && i!=0) fprintf(stderr, "/n"); 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; return app.exec(); }  

三、QWaitCondition

#include <QtCore> #include <stdio.h> #include <stdlib.h> const int DataSize = 10000; const int BufferSize = 8192; int buffer[BufferSize]; QWaitCondition bufferEmpty; QWaitCondition bufferFull; QMutex mutex; int numUsedBytes = 0; int rIndex=0; class Producer : public QThread { public: void run(); }; void Producer::run() { for (int i = 0; i < DataSize; ++i) { mutex.lock(); if (numUsedBytes == BufferSize) bufferEmpty.wait(&mutex); // mutex.unlock(); buffer[i % BufferSize] = numUsedBytes; // mutex.lock(); ++numUsedBytes; bufferFull.wakeAll(); mutex.unlock(); } } class Consumer : public QThread { public: void run(); }; void Consumer::run() { forever { mutex.lock(); if (numUsedBytes == 0) bufferFull.wait(&mutex); // mutex.unlock(); printf("%ul::[%d]=%d->%d /n", currentThreadId (),rIndex,buffer[rIndex],numUsedBytes); // mutex.lock(); rIndex = (++rIndex)%BufferSize; --numUsedBytes; bufferEmpty.wakeAll(); mutex.unlock(); } printf("/n"); } int main(int argc, char *argv[]) { QCoreApplication app(argc, argv); for (int i = 0; i < BufferSize; ++i) { buffer[i ] = -1; } Producer producer; Consumer consumerA; Consumer consumerB; producer.start(); consumerA.start(); consumerB.start(); producer.wait(); consumerA.wait(); consumerB.wait(); return 0; }  

 

上面用QSemaphore和QWaitCondition两个类完成生产者和消费者实例，对

我们实际工作很有益处。