改过拉还是不对，线程读数据的问题

Question

初始化部分 
DCB dcb;
   COMMTIMEOUTS TimeOuts;
   hComDev=CreateFile("COM1",GENERIC_READ|GENERIC_WRITE,0,NULL,OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL|FILE_FLAG_OVERLAPPED,NULL);
   if(hComDev==INVALID_HANDLE_VALUE) 
   {

   AfxMessageBox("串口错误");
   }
   SetupComm(hComDev,1024,1024);   
   GetCommState(hComDev,&dcb);
   dcb.BaudRate=CBR_9600;
   dcb.fParity=NOPARITY;
   dcb.ByteSize=8;
   dcb.StopBits=ONESTOPBIT;
SetCommMask(hComDev,EV_ERR|EV_RXCHAR);
   PurgeComm(hComDev, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR );
   SetCommState(hComDev,&dcb);
    TimeOuts.ReadIntervalTimeout=0xFFFFFFFF; 
TimeOuts.ReadTotalTimeoutMultiplier=0; 
TimeOuts.ReadTotalTimeoutConstant=1000; 
TimeOuts.WriteTotalTimeoutMultiplier=2*9600/dcb.BaudRate ; 
TimeOuts.WriteTotalTimeoutConstant=25;
   SetCommTimeouts(hComDev,&TimeOuts);
   CEdit*edt1=(CEdit*)GetDlgItem(IDC_EDIT2);
   SetCommMask( hComDev, EV_RXCHAR );
   m_pThread=AfxBeginThread(CommProc,(LPVOID)edt1, THREAD_PRIORITY_NORMAL, 0,0, NULL);
线程读数据部分
UINT CommProc(LPVOID pParam)
{
DWORD       dwEvtMask ;
DWORD length;
char buf[200]={0};
CString sss;
COMSTAT ComStat;
DWORD dwErrorFlags;
OVERLAPPED   m_osRead={0};
// SetCommMask( hComDev, EV_RXCHAR );

for( ; ;)
{
char buf[200]={0};
dwEvtMask = 0;
WaitCommEvent( hComDev, &dwEvtMask, NULL );
  if ((dwEvtMask & EV_RXCHAR) == EV_RXCHAR)
  {    
ClearCommError(hComDev,&dwErrorFlags,&ComStat);
length=min(255, ComStat.cbInQue);
 if(length > 0)
  {
 m_osRead.hEvent = CreateEvent(NULL,TRUE,FALSE,NULL); 
ReadFile(hComDev,buf,length,&length,&m_osRead);
if(WaitForSingleObject(m_osRead.hEvent,3000)==WAIT_TIMEOUT);
// Sleep(500);
sss.Format("%s",buf);
CEdit*ed=(CEdit*)pParam;
ed->SetWindowText(sss);

  }
return (UINT)0;
}
现在显示读回的数据始终不对，数据不是一次被都会的，尔是几次读回的，我是想一次读回缓冲区的数据，
如果去掉WaitForSingleObject函数，用延时数据分两次被读回，第一次读回前8个字节，第二次读回剩余的字节