The QWaitCondition class provides a condition variable for synchronizing threads.
//为同步线程提供条件变量

bool QWaitCondition::wait(QMutex *lockedMutex, unsigned long time = ULONG_MAX)
Releases the lockedMutex and waits on the wait condition.
//开释lockedMutex并期待条件

void QWaitCondition::wakeAll()
Wakes all threads waiting on the wait condition.
激活所有期待 期待条件的thread

include <QtCore>

include <iostream>

const int DataSize = 100000;
const int BufferSize = 4096;
char buffer[BufferSize];

QWaitCondition bufferIsNotFull;
QWaitCondition bufferIsNotEmpty;
QMutex mutex;
int usedSpace = 0;

class Producer : public QThread
{
public:

void run();

};

void Producer::run()
{

for (int i = 0; i < DataSize; ++i) {    mutex.lock();    while (usedSpace == BufferSize)//曾经填满了缓冲区，是满的        bufferIsNotFull.wait(&mutex); //期待 bufferIsNotFull    /***还有空间填充  **/    buffer[i % BufferSize] = "ACGT"[uint(std::rand()) % 4];    ++usedSpace;    bufferIsNotEmpty.wakeAll();//填充了之后，缓存区是非空的，会唤醒期待bufferIsNotEmpty的线程    mutex.unlock();}

}

class Consumer : public QThread
{
public:

void run();

};

void Consumer::run()
{

for (int i = 0; i < DataSize; ++i){    mutex.lock();    while (usedSpace == 0)// 缓存区没有任何数据，就是空的        bufferIsNotEmpty.wait(&mutex);//期待bufferIsNotEmpty    /*** 缓存区有数据 **/    std::cerr << buffer[i % BufferSize];    --usedSpace;    bufferIsNotFull.wakeAll();//生产了数据后，缓存区是非满的，会唤醒期待bufferIsNotFull的线程    mutex.unlock();}std::cerr << std::endl;

}

int main()
{

Producer producer;Consumer consumer;producer.start();consumer.start();producer.wait();consumer.wait();return 0;

}