用Builder C++设计串行口COM1或COM2的读写操作

EnterCriticalSection（&port-＞m_csCommunicationSync）；

// ClearCommError（） will update the COMSTAT structure and
// clear any other errors.

bResult = ClearCommError（port-＞m_hComm, &dwError, &comstat）；

LeaveCriticalSection（&port-＞m_csCommunicationSync）；

// start forever loop. I use this type of loop because I
// do not know at runtime how many loops this will have to
// run. My solution is to start a forever loop and to
// break out of it when I have processed all of the
// data available. Be careful with this approach and
// be sure your loop will exit.
// My reasons for this are not as clear in this sample
// as it is in my production code, but I have found this
// solutiion to be the most efficient way to do this.

if （comstat.cbInQue == 0）
{
// break out when all bytes have been read
break；
}

EnterCriticalSection（&port-＞m_csCommunicationSync）；

if （bRead）
{
bResult = ReadFile（port-＞m_hComm, // Handl
to COMM port
&RXBuff,
/ RX Buffer Pointer
1,
/ Read one byte
&BytesRead,
/ Stores number of bytes read
&port-＞m_ov）；
/ pointer to the m_ov structure
// deal with the error code
if （!bResult）
{
switch （dwError = GetLastError（））
{
case ERROR_IO_PENDING:
{
// asynchronous i/o is s
ill in progress
// Proceed on to GetOver
appedResults（）；
bRead = false；
break；
}
default:
{
// Another error has occ
red. Process this error.
port-＞ProcessErrorMessag
（"ReadFile（）"）；
break；
}
}
}
else
{
// ReadFile（） returned complete. It is not neces
ary to call GetOv
erlappedResults（）
bRead = true；
}
} // close if （bRead）

if （!bRead）
{
bRead = true；
bResult = GetOverlappedResult（port-＞m_hComm, // Handl
to COMM port

&port-＞m_ov, // Overlapped structure

&BytesRead, // Stores number of bytes read

true）； // Wait flag

// deal with the error code
if （!bResult）
{
port-＞ProcessErrorMessage（"GetOverlappedResults（
in ReadFile（）"）；

}
} // close if （!bRead）

LeaveCriticalSection（&port-＞m_csCommunicationSync）；

// notify parent that a byte was received
::SendMessage（（port-＞m_pOwner）-＞Handle, WM_COMM_RXCHAR, （WPARAM）

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