Overlapped I/O on XP

[donna rigas]

Hi -

I'm using overlapped i/o on Windows 98 and on XP
and am getting different results.

Here's the code snippet:

// read the command id and the message length
BOOL rc;
ResetEvent(m_Se rialRecvOL.hEve nt);
rc = ReadFile(m_hSer ialPort, &buf[1], 6, pBytesRead,
(LPOVERLAPPED) &m_SerialRecvOL );
if (!rc && GetLastError() == ERROR_IO_PENDIN G) {
waitStatus = WaitForSingleOb ject(
m_SerialRecvOL. hEvent, 5000);
if (status == WAIT_OBJECT_0){
GetOverlappedRe sult(m_hSerialP ort,
&m_SerialRecvOL , pBytesRead, FALSE);
rc = TRUE;
}
}

On windows 98, ReadFile returns with rc = false
and pBytesRead = 0 and then the operation is
successfully completed later and GetOverlappedRe sult
fills in pBytesRead with 6 to indicate 6 bytes read.

On XP, ReadFile returns right away with rc = true
and *pBytesRead = 3. I don't get all my data (6 bytes),
yet the call to ReadFile indicates that it's done
even though it only reads 3 bytes.

Can anyone tell me what I'm missing here?

Thanks,
Donna Rigas
ioline corporation

[Doug Forster]

Hi,

I think this is normal for a serial port. You need to keep reading until no
more data arrives, or you have the data you are expecting. Not sure
specifically why W98 and XP behaviour differs but this is hardly surprising
as XP is a NT derivative so completely different underlying code.

PS This is not really a suitable NG for this subject

Cheers

Doug Forster

"donna rigas" <an*******@disc ussions.microso ft.com> wrote in message
news:0c******** *************** *****@phx.gbl.. .

Hi -

I'm using overlapped i/o on Windows 98 and on XP
and am getting different results.

Here's the code snippet:

// read the command id and the message length
BOOL rc;
ResetEvent(m_Se rialRecvOL.hEve nt);
rc = ReadFile(m_hSer ialPort, &buf[1], 6, pBytesRead,
(LPOVERLAPPED) &m_SerialRecvOL );
if (!rc && GetLastError() == ERROR_IO_PENDIN G) {
waitStatus = WaitForSingleOb ject(
m_SerialRecvOL. hEvent, 5000);
if (status == WAIT_OBJECT_0){
GetOverlappedRe sult(m_hSerialP ort,
&m_SerialRecvOL , pBytesRead, FALSE);
rc = TRUE;
}
}

On windows 98, ReadFile returns with rc = false
and pBytesRead = 0 and then the operation is
successfully completed later and GetOverlappedRe sult
fills in pBytesRead with 6 to indicate 6 bytes read.

On XP, ReadFile returns right away with rc = true
and *pBytesRead = 3. I don't get all my data (6 bytes),
yet the call to ReadFile indicates that it's done
even though it only reads 3 bytes.

Can anyone tell me what I'm missing here?

Thanks,
Donna Rigas
ioline corporation