QThread線程池

Question

我想用QThread編寫線程輪詢。

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(); 
} 

我正在創建有限數量的線程，我想在其中執行任務。 但是，我不明白如何獲得釋放線程的數量。 我知道QThreadPool和Qtconcurrent，但我不想使用它。 也許，值得注意的是QPair的矢量中的每個線程都是免費的。

Answer 1

1. 你並不真的需要一個QVector<QPair<bool, QThread>>跟蹤所有的線程池中的，而不是使用QList< QThread* >其中僅保留指針指向自由線程。

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

2. 在投幣freeThread（）的使用從QObject的發送者（）方法來獲得的信號發送器，在這種情況下將是的QThread，這已成爲自由的指針

   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. 最後getFreeThread（）可以是這樣的：

   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; 
         } 
       } 
   
   } 
   

你也應該處理的C ase當在addTask中返回NULL指針時：

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