Re: interthread communication

From:

mfc <mfcprog@googlemail.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Sun, 22 Aug 2010 08:52:30 -0700 (PDT)

Message-ID:

<072ec6c1-d51d-4ac6-923c-e4aa83a8ad49@x21g2000yqa.googlegroups.com>

I`m writing a small demo example which simulates the hole stuff. At
the moment it seems to work but maybe there are several big or small
errors inside the code. By the way according to the protocok the
maximal amount of time where to data will be txd by the serial port
could be 1s - but should be round about 100ms.

I installed one buffer in my sdi application - pressing this button
simulate new incoming ethernet frame packets.

void TestDlg::OnBnClickedButton1()
{
   //creating some data
   CByteArray *pData = new CByteArray;
    const BYTE cbyte[] = "byte";

    for(int i=0;i<sizeof(cbyte);i++)
       pData->Add(cbyte[i]);

   //tx these data to the serial-collect thread
   m_collectThread->PostThreadMessage(UWM_GET_NEW_DATA, (WPARAM)pData,
0);
}

void CSerialCollectData::OnGetNewData(WPARAM wParam, LPARAM lParam)
{
     CByteArray *pData = (CByteArray *)wParam;

    // Queue q -> from your example "queuetest"

    if(!q.AddTail(pData))
    { /* failed */
        TRACE(_T("queue is full\n"));
        return;
    } /* failed */
    else
      long n = InterlockedIncrement(&count);

    if(FIRST_DATA)
    {
        FIRST_DATA = FALSE;
        //tell writerthread that first data arrived
        ::PostThreadMessage(WriterTheadID, UWM_START_WRITER,
(WPARAM)&q, (LPARAM)&count);
    }
}

void CSerialWriterThread::OnStartWriter(WPARAM wParam, LPARAM lParam)
{
   Queue *q = (Queue *)wParam;
   pcnt = (long *)lParam;

   WriteData(q);
}

void CSerialWriterThread::WriteData(Queue *q)
{
     CByteArray *pData;
     BOOL running = TRUE;
     DWORD EventMask;
    HANDLE objects[2];
    objects[0] = ShutdownEvent;

     hEvent = CreateEvent(NULL,false, false, _T(""));
     EventMask = FT_EVENT_MODEM_STATUS;

     while(running)
     {
          //simulate write (CByteArray *pData) to serial port (with
this small sleep delay)
         ::Sleep(200 + rand() % 500);

         //waiting for the CTS_HIGH event, which should occur after
round about 25ms -> we wait 50ms
        DWORD result = WaitForSingleObject(hEvent, 50);

        switch(result)
        {
        case WAIT_TIMEOUT:
               //send a PostThreadMessage to main-thread telling there
must be something wrong and continue
              break;

       case WAIT_OBJECT_0:
            //shutdown event
            return; //or running = FALSE

       case WAIT_OBJECT_0 + 1:
          //everthing is ok
          break;

        default:
           ASSERT(FALSE); // unknown error
           return;

        }

        if(q->GetSize() > 1)
        { //more than one packet -> transmit new packet
                 LPVOID p = q->RemoveHead();
     long n = InterlockedDecrement(pcnt);
    pData = (CByteArray *) p;
        }

     }
}

Where do I have to delete the CByteArray *pData = new CByteArray; in
the OnClickButton routine?

CSerialWriterThread::CSerialWriterThread(void)
{
    ShutdownEvent = ::CreateEvent(NULL, // security
                                   TRUE, // manual-reset
                                   FALSE, // not signaled
                                   NULL); // anonymous

}
According to one of your hints, I tried to install a shutdown event;
but how can I shutdown this thread, if e.g. the timeout error occured
several times? Writing a PostThreadMessage from the main-thread to
this thread and calling the function CSerialWriterThread::Shutdown( )?

void CSerialWriterThread::Shutdown( )
   {
    SetEvent(ShutdownEvent);
    ::WaitForSingleObject(m_hThread, INFINITE);
   }

best regards
Hans