Create a timer
#include <signal.h> #include <time.h> int timer_create( clockid_t clock_id, struct sigevent * evp, timer_t * timerid );
While the processor isn't in a power-saving mode, CLOCK_SOFTTIME behaves the same as CLOCK_REALTIME.
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
The timer_create() function creates a per-process timer using the specified clock source, clock_id, as the timing base.
You can use the time ID that the function stores in timerid in subsequent calls to timer_gettime(), timer_settime(), and timer_delete().
The timer is created in the disabled state, and isn't enabled until you call timer_settime().
We recommend the following event types:
If the evp argument is NULL, a SIGALRM signal is sent to your process when the timer expires. To specify a handler for this signal, call sigaction().
/* * Demonstrate how to set up a timer that, on expiry, * sends us a pulse. This example sets the first * expiry to 1.5 seconds and the repetition interval * to 1.5 seconds. */ #include <stdio.h> #include <time.h> #include <sys/netmgr.h> #include <sys/neutrino.h> #define MY_PULSE_CODE _PULSE_CODE_MINAVAIL typedef union { struct _pulse pulse; /* your other message structures would go here too */ } my_message_t; main() { struct sigevent event; struct itimerspec itime; timer_t timer_id; int chid; int rcvid; my_message_t msg; chid = ChannelCreate(0); event.sigev_notify = SIGEV_PULSE; event.sigev_coid = ConnectAttach(ND_LOCAL_NODE, 0, chid, _NTO_SIDE_CHANNEL, 0); event.sigev_priority = getprio(0); event.sigev_code = MY_PULSE_CODE; timer_create(CLOCK_REALTIME, &event, &timer_id); itime.it_value.tv_sec = 1; /* 500 million nsecs = .5 secs */ itime.it_value.tv_nsec = 500000000; itime.it_interval.tv_sec = 1; /* 500 million nsecs = .5 secs */ itime.it_interval.tv_nsec = 500000000; timer_settime(timer_id, 0, &itime, NULL); /* * As of the timer_settime(), we will receive our pulse * in 1.5 seconds (the itime.it_value) and every 1.5 * seconds thereafter (the itime.it_interval) */ for (;;) { rcvid = MsgReceive(chid, &msg, sizeof(msg), NULL); if (rcvid == 0) { /* we got a pulse */ if (msg.pulse.code == MY_PULSE_CODE) { printf("we got a pulse from our timer\n"); } /* else other pulses ... */ } /* else other messages ... */ } }
Safety: | |
---|---|
Cancellation point | No |
Interrupt handler | No |
Signal handler | Yes |
Thread | Yes |
The QNX Neutrino version of timer_create() is different from the QNX 4 version, which was based on a draft standard.
clock_getres(), clock_gettime(), clock_settime(), nanosleep(), _pulse, sigaction(), sigevent, sleep(), TimerCreate(), timer_delete(), timer_getexpstatus(), timer_getoverrun(), timer_gettime(), timer_settime()
Clocks, Timers, and Getting a Kick Every So Often chapter of Getting Started with QNX Neutrino
Tick, Tock: Understanding the Neutrino Microkernel's Concept of Time chapter of the QNX Neutrino Programmer's Guide