20000804014.htm

C++Builder教学大全

          else <br>
          ProcessErrorMessage("GetCommState()"); <br>
          } <br>
          else <br>
          ProcessErrorMessage("SetCommMask()"); <br>
          } <br>
          else <br>
          ProcessErrorMessage("SetCommTimeouts()"); <br>
          <br>
          delete [] szPort; <br>
          delete [] szBaud; <br>
          <br>
          // flush the port <br>
          PurgeComm(m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PU 
          <br>
          RGE_TXABORT); <br>
          <br>
          // release critical section <br>
          LeaveCriticalSection(&amp;m_csCommunicationSync); <br>
          <br>
          return true; <br>
          } <br>
          <br>
          // <br>
          // The CommThread Function. <br>
          // <br>
          DWORD _stdcall TSerialPort::CommThread(LPVOID pParam) <br>
          { <br>
          // Cast the void pointer passed to the thread back to <br>
          // a pointer of TSerialPort class <br>
          TSerialPort *port = (TSerialPort*)pParam; <br>
          <br>
          // Set the status variable in the dialog class to <br>
          // TRUE to indicate the thread is running. <br>
          port-&gt;m_bThreadAlive = true; <br>
          <br>
          // Misc. variables <br>
          DWORD BytesTransfered = 0; <br>
          DWORD Event = 0; <br>
          DWORD CommEvent = 0; <br>
          DWORD dwError = 0; <br>
          COMSTAT comstat; <br>
          BOOL bResult = true; <br>
          <br>
          // Clear comm buffers at startup <br>
          if (port-&gt;m_hComm) // check if the port is opened <br>
          PurgeComm(port-&gt;m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_R 
          <br>
          ABO <br>
          RT | PURGE_TXABORT); <br>
          <br>
          // begin forever loop. This loop will run as long as the thread is a 
          <br>
          live. <br>
          for (;;) <br>
          { <br>
          <br>
          // Make a call to WaitCommEvent(). This call will return immedi <br>
          tly <br>
          <br>
          // because our port was created as an async port (FILE_FLAG_OVER <br>
          APP <br>
          ED <br>
          // and an m_OverlappedStructerlapped structure specified). This <br>
          cal <br>
          l will cause the <br>
          // m_OverlappedStructerlapped element m_OverlappedStruct.hEvent, <br>
          whi <br>
          ch is part of the m_hEventArray to <br>
          // be placed in a non-signeled state if there are no bytes avail <br>
          ble <br>
          to be read, <br>
          // or to a signeled state if there are bytes available. If this <br>
          eve <br>
          nt handle <br>
          // is set to the non-signeled state, it will be set to signeled <br>
          hen <br>
          a <br>
          // character arrives at the port. <br>
          <br>
          // we do this for each port! <br>
          <br>
          bResult = WaitCommEvent(port-&gt;m_hComm, &amp;Event, &amp;port-&gt;m_ov); 
          <br>
          <br>
          if (!bResult) <br>
          { <br>
          // If WaitCommEvent() returns FALSE, process the last er <br>
          or to dete <br>
          rmin <br>
          rmin <br>
          // the reason.. <br>
          switch (dwError = GetLastError()) <br>
          { <br>
          case ERROR_IO_PENDING: <br>
          { <br>
          // This is a normal return value if ther <br>
          are no bytes <br>
          // to read at the port. <br>
          // Do nothing and continue <br>
          break; <br>
          } <br>
          case 87: <br>
          { <br>
          // Under Windows NT, this value is retur <br>
          ed for some reason. <br>
          // I have not investigated why, but it i <br>
          also a valid reply <br>
          // Also do nothing and continue. <br>
          break; <br>
          } <br>
          default: <br>
          { <br>
          // All other error codes indicate a seri <br>
          us error has <br>
          // occured. Process this error. <br>
          port-&gt;ProcessErrorMessage("WaitCommEvent <br>
          )"); <br>
          break; <br>
          } <br>
          } <br>
          } <br>
          else <br>
          { <br>
          // If WaitCommEvent() returns TRUE, check to be sure the <br>
          e are <br>
          // actually bytes in the buffer to read. <br>
          // <br>
          // If you are reading more than one byte at a time from <br>
          he buffer <br>
          <br>
          // (which this program does not do) you will have the si <br>
          uation occ <br>
          ur <br>
          // where the first byte to arrive will cause the WaitFor <br>
          ultipleObj <br>
          ects() <br>
          // function to stop waiting. The WaitForMultipleObjects <br>
          ) function <br>
          <br>
          // resets the event handle in m_OverlappedStruct.hEvent <br>
          o the non- <br>
          signelead state <br>
          // as it returns. <br>
          // <br>
          // If in the time between the reset of this event and th <br>
          call to <br>
          // ReadFile() more bytes arrive, the m_OverlappedStruct. <br>
          Event hand <br>
          le will be set again <br>
          // to the signeled state. When the call to ReadFile() oc <br>
          urs, it wi <br>
          ll <br>
          // read all of the bytes from the buffer, and the progra <br>
          will <br>
          // loop back around to WaitCommEvent(). <br>
          // <br>
          // At this point you will be in the situation where m_Ov <br>
          rlappedStr <br>
          uct.hEvent is set, <br>
          // but there are no bytes available to read. If you pro <br>
          eed and ca <br>
          ll <br>
          // ReadFile(), it will return immediatly due to the asyn <br>
          port setu <br>
          p, but <br>
          // GetOverlappedResults() will not return until the next <br>
          character <br>
          arrives. <br>
          // <br>
          // It is not desirable for the GetOverlappedResults() fu <br>
          ction to b <br>
          e in <br>
          // this state. The thread shutdown event (event 0) and <br>
          he WriteFi <br>
          le() <br>
          // event (Event2) will not work if the thread is blocked <br>
          by GetOver <br>
          lappedResults(). <br>
          // <br>
          // The solution to this is to check the buffer with a ca <br>
          l to Clear <br>
          CommError(). <br>
          // This call will reset the event handle, and if there a <br>
          e no bytes <br>
          to read <br>
          // we can loop back through WaitCommEvent() again, then <br>
          roceed. <br>
          // If there are really bytes to read, do nothing and pro <br>
          eed. <br>
          <br>
          bResult = ClearCommError(port-&gt;m_hComm, &amp;dwError, &amp;comst 
          <br>
          t); <br>
          <br>
          if (comstat.cbInQue == 0) <br>
          continue; <br>
          } // end if bResult <br>
          <br>
          // Main wait function. This function will normally block the th <br>
          ead <br>
          <br>
          <br>
          // until one of nine events occur that require action. <br>
          Event = WaitForMultipleObjects(3, port-&gt;m_hEventArray, false, IN 
          <br>
          INI <br>
          TE); <br>
          <br>
          switch (Event) <br>
          { <br>
          case 0: <br>
          { <br>
          // Shutdown event. This is event zero so it wil <br>
          be <br>
          // the higest priority and be serviced first. <br>
          <br>
          port-&gt;m_bThreadAlive = false; <br>
          <br>
          // Kill this thread. break is not needed, but m <br>
          kes me feel bette <br>
          r. <br>
          ExitThread(100); <br>
          break; <br>
          } <br>
          case 1: // read event <br>
          { <br>
          GetCommMask(port-&gt;m_hComm, &amp;CommEvent); <br>
          if (CommEvent &amp; EV_CTS) <br>
          ::SendMessage(port-&gt;m_pOwner-&gt;Handle, WM <br>
          COMM_CTS_DETECTED, (WPAR <br>
          AM) 0, (LPARAM) port-&gt;m_nPortNr); <br>
          if (CommEvent &amp; EV_RXFLAG) <br>
          ::SendMessage(port-&gt;m_pOwner-&gt;Handle, WM <br>
          COMM_RXFLAG_DETECTED, (W <br>
          PARAM) 0, (LPARAM) port-&gt;m_nPortNr); <br>
          if (CommEvent &amp; EV_BREAK) <br>
          ::SendMessage(port-&gt;m_pOwner-&gt;Handle, WM <br>
          COMM_BREAK_DETECTED, (WP <br>
          ARAM) 0, (LPARAM) port-&gt;m_nPortNr); <br>
          if (CommEvent &amp; EV_ERR) <br>
          ::SendMessage(port-&gt;m_pOwner-&gt;Handle, WM <br>
          COMM_ERR_DETECTED, (WPAR <br>
          AM) 0, (LPARAM) port-&gt;m_nPortNr); <br>
          if (CommEvent &amp; EV_RING) <br>
          ::SendMessage(port-&gt;m_pOwner-&gt;Handle, WM <br>
          COMM_RING_DETECTED, (WPA <br>
          RAM) 0, (LPARAM) port-&gt;m_nPortNr); <br>
          <br>
          if (CommEvent &amp; EV_RXCHAR) <br>
          // Receive character event from port. <br>
          ReceiveChar(port, comstat); <br>
          <br>
          break; <br>
          } <br>
          case 2: // write event <br>
          { <br>
          // Write character event from port <br>
          WriteChar(port); <br>
          break; <br>
          } <br>
          <br>
          } // end switch <br>
          <br>
          } // close forever loop <br>
          <br>
          return 0; <br>
          } <br>
          <br>
          // <br>
          // <br>
          // start comm watching <br>
          // <br>
          BOOL TSerialPort::StartMonitoring() <br>
          { <br>
          DWORD lpThreadId; <br>
          m_HThread =CreateThread(NULL, <br>
          0, <br>
          CommThread, <br>
          this, <br>
          0, <br>
          &amp;lpThreadId); <br>
          if(m_HThread==NULL) <br>
          { <br>
          ProcessErrorMessage("Create Thread Error"); <br>
          return false; <br>
          } <br>
          return true; <br>
          } <br>
          <br>
          // <br>
          // Restart the comm thread <br>
          // <br>
          // <br>
          BOOL TSerialPort::RestartMonitoring() <br>
          { <br>
          ResumeThread(m_HThread); <br>
          return true; <br>
          } <br>
          <br>
          // <br>
          // Suspend the comm thread <br>
          // <br>
          BOOL TSerialPort::StopMonitoring() <br>
          { <br>
          SuspendThread(m_HThread); <br>
          return true; <br>