QThread threadpool

QThread threadpool

本文关键字：threadpool QThread      更新时间：2023-10-16

我正在尝试使用 QThread 编写线程轮询。

class ThreadPool: public QObject
{
    Q_OBJECT
public:
    ThreadPool(int maxThreads);
    void addTask(MyTask *task);
private:
    int maxThreads;
    QMutex mutex;
    QVector<QPair<bool, QThread>> threads;
    QThread *getFreeThread();
public slots:
   void freeThread();
};

void ThreadPool::addTask(MyTask* task)
{
    QThread *thread = getFreeThread();
    task->moveToThread(thread);
    connect(thread, SIGNAL(started()), task, SLOT(doWork()));
    connect(task, SIGNAL(workFinished()), thread, SLOT(quit()));
    connect(thread, SIGNAL(finished()), task, SLOT(deleteLater()));
    connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));
    connect(thread, SIGNAL(finished()), this, SLOT(freeThread()));
    thread->start();
}

我正在创建有限数量的线程，我想在其中执行任务。但是，我不明白如何获取释放线程的编号。我知道QThreadPool和Qtconcurrent，但我不想使用它。也许，值得注意的是 QPair 向量中的每个线程是否免费。

  1. 您实际上并不需要QVector<QPair<bool, QThread>>来跟踪池中的所有线程，而是使用仅包含指向空闲线程的指针的QList< QThread* >。

    private:
     QList<QThread*> freeThreads; // only free threads
     QList<QThread*> allThreads; // just to count the number of all threads

  2. 在插槽 freeThread(( 中使用 QObject 中的 sender(( 方法来获取信号发送者的指针，在本例中将是 QThread，它已经变得自由

    void ThreadPool::freeThread()
{
     // get the pointer to the thread that sent the signal:
     QObject* threadFreed = QObject::sender();
     if( ! freeThreads.contains( threadFreed ) )
     {
          // save the thread pointer in list
          freeThreads << threadFreed;
     }
}

  3. 最后getFreeThread((可以看起来像这样：

    QThread* getFreeThread()
{
     if( ! freeThreads.isEmpty() )
     {
          // take the first free thread
          return freeThreads.takeFirst();
     }
     else
     {
          if(allThreads.size() < maxThreads )
          {
             // create a new thread 
             QThread* thread = new QThread(this);
             allThreads << thread;
             return thread;
          }
          else
          {
            // Maximum number of threads exceeded 
            // and no free thread is available
             return NULL;
          }
     }
}

此外，您还应该处理在addTask中返回NULL 指针的情况：

void ThreadPool::addTask(MyTask* task)
{
    QThread *thread = getFreeThread();
    if( ! thread )
    {
        // do something else
        return;
    }
    // proceed with thread execution ...
}
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