I'm trying to read a Mac's built-in modem in raw mode (after some
help from this lists months ago, then a long period of downtime)
and I'm running into something annoying. When data shows up, it
comes through as a small burst (100 characters or so) followed by a
brief pause (.02 seconds, say) and then another small burst (32
characters).
The difficulty I'm having is that the read() I eventually issue
returns before the second burst shows up. Here's the setup routine.
static int set_local_mode(int inFileDescriptor)
{
int theResult = 0;
struct termios theOptions = {};
My understanding is that if this completes successfully, the read()
should return after once there has been a half-second interval
since the last character received. The buffer passed to read() is
much larger than the returned data, and the commented line doesn't
have any impact (c_lflag is already zero by the time we get there).
Any advice?
Your code asks for one character, so the VMIN requirement will be
satisfied before the VTIME requirement starts (VTIME is the number of
time periods to wait after the last character is received; until the
first character is received, there is no time requirement). I think
that is why you get the return before the second burst.
Also, if at the time of the call, there are bytes queued up, they
will be copied and if the VMIN requirement is thereby satisfied,
return is immediate.
Regards,
Justin
--
Justin C. Walker, Curmudgeon-At-Large
Institute for General Semantics
--------
Some people have a mental horizon of radius zero, and
call it their point of view.
-- David Hilbert
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