posix_timer.c

/**
 * How to compile in linux : 
 * gcc -lrt posix_timer.c  
 * to link posix timer functions.
 */

#include <stdio.h>
#include <time.h>
#include <signal.h>

#define SIGNO SIGUSR1
#define THREAD_TIMER

struct posix_timer {
    struct itimerspec ts;
    timer_t timer;
};

#ifdef THREAD_TIMER
void timer_handler(union sigval v)
{
    struct posix_timer* pt;

    pt = (struct posix_timer*) v.sival_ptr;
    printf("[%s]sigval_int %p\n",__FUNCTION__,pt);
    timer_settime(&pt->timer,0,&pt->ts,NULL);
}
#else
static void sigtimer_handler(int signo,siginfo_t *si,void *ucontext)
{
    struct posix_timer* pt;

    pt = (struct posix_timer*) si->si_ptr;
    printf("[%s]sigval_int %p\n",__FUNCTION__,pt);
    timer_settime(&pt->timer,0,&pt->ts,NULL);
}
#endif

main()
{
    int ret;
    struct sigevent evp;
    struct posix_timer pt;

#ifdef THREAD_TIMER
    evp.sigev_notify = SIGEV_THREAD;
    evp.sigev_notify_function = timer_handler;
    evp.sigev_value.sival_ptr = &pt;
    evp.sigev_notify_attributes = NULL;
#else
    struct sigaction act;
    sigset_t set;

    act.sa_sigaction = sigtimer_handler;
    act.sa_flags |= SA_SIGINFO;

    sigemptyset(&set);
    sigaddset(&set,SIGNO);
    sigprocmask(SIG_UNBLOCK,&set,NULL);

    if( sigaction(SIGNO,&act,NULL) < 0 ){
        perror("sigaction");
    }

    evp.sigev_notify = SIGEV_SIGNAL;
    evp.sigev_signo = SIGNO;
    evp.sigev_value.sival_ptr = &pt;
#endif

    pt.ts.it_value.tv_sec = 1;
    pt.ts.it_value.tv_nsec = 0;
    pt.ts.it_interval.tv_nsec = 2;
    pt.ts.it_interval.tv_nsec = 0;

    /* set timerid and evp */
    ret = timer_create(CLOCK_REALTIME,&evp,&pt.timer);
    if ( ret < 0 )
        perror("timer_create");

    ret = timer_settime(pt.timer,0,&pt.ts,NULL);
    if ( ret < 0 )
        perror("timer_settime");

    while(1){
        pause();
    }
}