用Builder C++设计串行口COM1或COM2的读写操作

// （which this program does not do） you will have the si
uation occ
ur
// where the first byte to arrive will cause the WaitFor
ultipleObj
ects（）
// function to stop waiting. The WaitForMultipleObjects
） function

// resets the event handle in m_OverlappedStruct.hEvent
o the non-
signelead state
// as it returns.
//
// If in the time between the reset of this event and th
call to
// ReadFile（） more bytes arrive, the m_OverlappedStruct.
Event hand
le will be set again
// to the signeled state. When the call to ReadFile（） oc
urs, it wi
ll
// read all of the bytes from the buffer, and the progra
will
// loop back around to WaitCommEvent（）.
//
// At this point you will be in the situation where m_Ov
rlappedStr
uct.hEvent is set,
// but there are no bytes available to read. If you pro
eed and ca
ll
// ReadFile（）, it will return immediatly due to the asyn
port setu
p, but
// GetOverlappedResults（） will not return until the next
character
arrives.
//
// It is not desirable for the GetOverlappedResults（） fu
ction to b
e in
// this state. The thread shutdown event （event 0） and
he WriteFi
le（）
// event （Event2） will not work if the thread is blocked
by GetOver
lappedResults（）.
//
// The solution to this is to check the buffer with a ca
l to Clear
CommError（）.
// This call will reset the event handle, and if there a
e no bytes
to read
// we can loop back through WaitCommEvent（） again, then
roceed.
// If there are really bytes to read, do nothing and pro
eed.

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

if （comstat.cbInQue == 0）
continue；
} // end if bResult

// Main wait function. This function will normally block the th
ead

// until one of nine events occur that require action.
Event = WaitForMultipleObjects（3, port-＞m_hEventArray, false, IN
INI
TE）；

switch （Event）
{
case 0:
{
// Shutdown event. This is event zero so it wil
be
// the higest priority and be serviced first.

port-＞m_bThreadAlive = false；

// Kill this thread. break is not needed, but m
kes me feel bette

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