PC通过串口读取rs232条码扫描枪扫描的条码有关问题

UINT __cdecl OnWatchCom(LPVOID lparam){    CBillDlg *pDlg = (CBillDlg *)lparam;    if(pDlg == NULL) return -1;    CString strResult;    char buff[128] = {0};    while(pDlg->m_IsWatching)    {        if(pDlg->m_Com.ReadCom(buff,128,2000))        {            pDlg->m_Com.ClearComBuf(PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR);            strResult.Format(_T("%s"),buff);            if(!strResult.IsEmpty())            {                pDlg->m_strBillNo = strResult;                pDlg->UpdateData(0);                    }        }        Sleep(50);    }    return 0;}BOOL CComport::ReadCom(char *buff, int nlen, int dwMiniTimeout){    if(!IsOpen()) return FALSE;    OVERLAPPED m_osRead;    memset(&m_osRead,0,sizeof(OVERLAPPED));    m_osRead.hEvent=CreateEvent(NULL,TRUE,FALSE,NULL);    COMSTAT ComStat;    DWORD dwErrorFlags;        memset(buff,'\0',nlen);    DWORD dwBytesRead=nlen;//读取的字节数    BOOL bReadStat;    ClearComErr(&dwErrorFlags,&ComStat);    dwBytesRead=min(dwBytesRead, (DWORD)ComStat.cbInQue);    bReadStat=ReadFile(m_hCom,buff,dwBytesRead,&dwBytesRead,&m_osRead);    if(!bReadStat)    {        if(GetLastError()==ERROR_IO_PENDING)//GetLastError()函数返回ERROR_IO_PENDING,表明串口正在进行读操作        {            //GetOverlappedResult(m_hCom,&m_osRead,&dwBytesRead,TRUE);            WaitForSingleObject(m_osRead.hEvent,dwMiniTimeout);            //使用WaitForSingleObject函数等待，直到读操作完成或延时已达到2秒钟            //当串口读操作进行完毕后，m_osRead的hEvent事件会变为有信号            //ResetEvent(m_osRead.hEvent);        }    }    CloseHandle(m_osRead.hEvent);    return TRUE;}