QThread线程池

Question

我想用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，我不明白如何获得释放线程的数量。 我知道QThreadPool和Qtconcurrent，但我不想使用它。 也许，值得注意的是QPair的矢量中的每个线程都是免费的。

Answer 1

1. 你并不真的需要一个QVector<QPair<bool, QThread>>跟踪所有的线程池中的，而不是使用QList< QThread* >其中仅保留指针指向自由线程。

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

2. 在投币freeThread（）的使用从QObject的发送者（）方法来获得的信号发送器，在这种情况下将是的QThread，这已成为自由的指针

   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（）可以是这样的：

   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; 
         } 
       } 
   
   } 
   

你也应该处理的C ase当在addTask中返回NULL指针时：

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