Getting Started with QNX Neutrino - QNX Software Systems

© 2009, QNX Software Systems GmbH & Co. KG. Pulses
The value member is actually a union:
union sigval {
int sival_int;
void *sival_ptr;
};
Therefore (expanding on the server example above), you often see code like:
#include
rcvid = MsgReceive (chid, ...
if (rcvid == 0) {
// it’s a pulse
// determine the type of pulse
switch (msg.pulse.code) {
case MY_PULSE_TIMER:
// One of your timers went off, do something
// about it...
break;
case MY_PULSE_HWINT:
// A hardware interrupt service routine sent
// you a pulse. There’s a value in the "value"
// member that you need to examine:
val = msg.pulse.value.sival_int;
// Do something about it...
break;
case _PULSE_CODE_UNBLOCK:
// A pulse from the kernel, indicating a client
// unblock was received, do something about it...
break;
// etc...
} else { // it’s a regular message
}
// determine the type of message
// handle it
This code assumes, of course, that you’ve set up your msg structure to contain a
struct _pulse pulse; member, and that the manifest constants
MY_PULSE_TIMER and MY_PULSE_HWINT are defined. The pulse code
_PULSE_CODE_UNBLOCK is one of those negative-numbered kernel pulses
mentioned above. You can find a complete list of them in along
with a brief description of the value field.
April 30, 2009 Chapter 2 • Message Passing 115