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我正在实现代码，因此我可以在网络连接到达时接受它们，将它们从它们的到达套接字中分离，创建一个 std::packaged_task 任务，将该任务排队在一个双端队列容器中，然后稍后在它们的任务线程中执行这些任务。Bo Qian 在 YouTube 上关于“C++ 线程 #9：packaged_task”的讲座让这一切变得简单，展示了如何做到这一点。

#include "stdafx.h"
#include <afxsock.h>
#include <condition_variable>
#include <deque>
#include <future>

std::condition_variable notifyDequeNotEmptyCondVar;
std::mutex decodeMu;

class MyRxDecode : public CAsyncSocket
{
public:
  static std::deque< std::packaged_task< bool() > > rxAcceptedTasks;

  static bool StartDecode( SOCKET socket )
  {
    bool result = true;

    // Attach detached socket to this socket
    //result = Attach( socket ); //  error C2352: 'CAsyncSocket::Attach': illegal call of non-static member function
    return result;
  }

  static bool DecodeTaskThread()
  {
    std::packaged_task< bool() > DecodingTask;

    {
      std::unique_lock< std::mutex > dequeLocker( decodeMu ); // makes sure all deque actions are atomic
      notifyDequeNotEmptyCondVar.wait( dequeLocker, [] () { return !rxAcceptedTasks.empty(); } ); // wait until notified that deque is not empty
      DecodingTask = std::move( rxAcceptedTasks.front() );
      rxAcceptedTasks.pop_front();
    }

    DecodingTask(); // has no arg because the arg was previously bound to the functor passed in

    return true;
  }
};


class MyListener : CAsyncSocket
{
  virtual void OnAccept( int nErrorCode ) // is called when other socket does a connect on this socket's endpoint
  {
    CAsyncSocket syncSocket; // msdn prescribes creating stack socket
    if( Accept( syncSocket ) )
    {
      AsyncSelect( FD_READ | FD_CLOSE ); // msdn
      SOCKET socket = syncSocket.Detach(); // msdn

      // Bo Qian's lecture explains how this packaged task code works and is made thread safe.
      // Create task in separate thread to process this connection and push onto deque. The main advantage of a packaged task compared to using a functor is the former links the callable object to a future, which is useful in a multi-threaded environment (Bo Qian).
      std::thread decodeThread( MyRxDecode::DecodeTaskThread ); // pass-by-value ctor
      std::packaged_task< bool() > rxAcceptTask( std::bind( MyRxDecode::StartDecode, socket ) ); // binds function with its param to create functor wh is passed to packaged task's ctor
      std::future< bool > rxAcceptTaskFuture = rxAcceptTask.get_future();

      {
        std::lock_guard< std::mutex > locker( decodeMu );
        MyRxDecode::rxAcceptedTasks.push_back( std::move( rxAcceptTask ) );
      }
      notifyDequeNotEmptyCondVar.notify_one();
      bool taskResult = rxAcceptTaskFuture.get();
      decodeThread.join();

      CAsyncSocket::OnAccept( nErrorCode ); // msdn
    }
  }
};

std::deque< std::packaged_task< bool() > > MyRxDecode::rxAcceptedTasks;

int main()
{
  return 0;
}

在我的情况下，代码无法编译，因为我的 StartDecode 是一个试图调用非静态 Attach 的静态方法。StartDecode 是一个静态方法，因为 std::bind 用于将“套接字”绑定到任务。'socket' 通常会被传入 StartDecode 方法，但为了使打包任务中的 'future' 正常工作，必须使用 std::bind 提前绑定任何传入的参数。但是一旦 StartDecode 设置为静态，对 CAsyncSocket 的 Attach（非静态）的调用会导致错误 C2352。

如何从静态 MyRxDecode::StartDecode 调用非静态 Attach 方法？有没有办法避免将套接字参数绑定到任务而不使其成为静态？

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1 回答 1

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std::bind 允许您调用非静态成员函数。请参阅 cppreference.com->std::bind：

Notes
… when invoking a pointer to non-static member function or pointer to  
non-static data member, the first argument has to be a reference or pointer (including, 
possibly, smart pointer such as std::shared_ptr and std::unique_ptr) to an object whose 
member will be accessed.

用以下代码替换上面代码中rxAcceptTask的定义：

std::packaged_task< bool() > rxAcceptTask( std::bind( &MyRxDecode::StartDecode, &myRxDecode, socket ) );

让bool StartDecode( SOCKET socket )成员函数变为非静态的。

于 2016-06-14T21:05:33.957 回答