Getting Started with QNX Neutrino - QNX Software Systems

© 2009, QNX Software Systems GmbH & Co. KG. Using timers
int chid; // channel ID (global)
int debug = 1; // set debug value, 1=on, 0=off
char *progname = "time1.c";
// forward prototypes
static void setupPulseAndTimer (void);
static void gotAPulse (void);
static void gotAMessage (int rcvid, ClientMessageT *msg);
main()
This next section of code is the mainline. It’s responsible for:
• creating the channel (via ChannelCreate()),
• calling the setupPulseAndTimer() routine (to set up a once-per-second timer, with a
pulse as the event delivery method), and then
• sitting in a “do-forever” loop waiting for pulses or messages and processing them.
Notice the check against the return value from MsgReceive() — a zero indicates it’s a
pulse (and we don’t do any strong checking to ensure that it’s our pulse), a non-zero
indicates it’s a message. The processing of the pulse or message is done by
gotAPulse() and gotAMessage().
int
main (void)
{
int rcvid;
MessageT msg;
// ignore command-line arguments
// process ID of the sender
// the message itself
if ((chid = ChannelCreate (0)) == -1) {
fprintf (stderr, "%s: couldn’t create channel!\n",
progname);
perror (NULL);
exit (EXIT_FAILURE);
}
// set up the pulse and timer
setupPulseAndTimer ();
// receive messages
for (;;) {
rcvid = MsgReceive (chid, &msg, sizeof (msg), NULL);
}
// determine who the message came from
if (rcvid == 0) {
// production code should check "code" field...
gotAPulse ();
} else {
gotAMessage (rcvid, &msg.msg);
}
}
// you’ll never get here
return (EXIT_SUCCESS);
April 30, 2009 Chapter 3 • Clocks, Timers, and Getting a Kick Every So Often 151