On Fri, 07 Oct 2005 18:35:54 -0700, Dave said in
alt.radio.scanner:

Regarding overlapped: If overlapped I/O is not used then
there is no way to cancel an I/O operation because the
thread is blocked. WIN32 has a CancelIO function in the same
API but CancelIO cannot cancel I/O on another thread, only
the same thread. That makes it a real pain in the ass. But
overlapping allows the programmer to break the I/O off and
clean up without having to be in the same thread, AFAIK.
That's why I had to use it in this case.

Seems like plain old polled I/O - you can cancel any time the I/O
routine is still in the wait loop. The last time I did that, though,
was under DOS 2.1, so I have no idea if it can still be done in a
Windows API.