class DownloadTask
{
     //省略n行代码
public:
    int m_threads;//需创建的线程总数
    CCriticalSection m_cs;//临界区
    void Stop();
};

class HttpDownload
{
    //省略n行代码
    HttpDownload(DownloadTask* task): m_task(task) { }
public:
    DownloadTask* m_task;
    void Start();//开始下载
}

//在某一个函数中
{
    DownloadTask* myTask =  new DownloadTask()
    HttpDownload* download = new HttpDownload(myTask);
    for(int i = 0; i < myTask->m_threads; ++i)
        AfxBeginThread(downloadThreadFun, download);
    return 0;
}

UINT downloadThreadFun(LPVOID lParam)
{
    auto_ptr<HttpDownload> pDownload((HttpDownload*)lParam);
    pDownload->Start();
    return 0;
}

void SetStop(DownloadTask* task)
{
    task->Stop();
    delete task;
}

class DownloadTask
{
     //省略n行代码
public:
    int m_threads;//需要创建的线程总数
    CCriticalSection m_cs;//临界区
    int m_currentThreads;//当前运行的线程数
    void Stop();
};

UINT downloadThreadFun(LPVOID lParam)
{
      auto_ptr<HttpDownload> pDownload((HttpDownload*)lParam);
      CSingleLock singleLock(&pDownload->m_task->m_cs);
      pDownload->Start();
      singleLock.Lock()
      --pDownload->m_task->m_currentThreads;
      return 0;
}

void SetStop(DownloadTask* task)
{
     CSingleLock singleLock(&task->m_cs);
     task->Stop();
     singleLock.Lock();
     if(task->m_currentThreads == 0)
        delete task;
     return 0;
}