alarmlib.c

#include    <sys/time.h>
#include    <signal.h>
#include    <errno.h>
#include    <stdio.h>
#include    <stdlib.h>
#include    <unistd.h>

/*
 *  alarmlib.c  
 *          timer functions for higher resolution clock
 *
 *          set_ticker( number_of_milliseconds )
 *              arranges for the interval timer to issue
 *              SIGALRM's at regular intervals
 *          millisleep( number_of_milliseconds )
 *
 *  version 12.04.01 changed interface to set_ticker so it rets -1 on error
 *  version 98.03.16
 */

int set_ticker(int n_msecs)
/*
 *  arg in milliseconds, converted into micro seoncds
 *  Returns -1 on error, 0 if no error
 */
{
    struct itimerval new_timeset, old_timeset;
    long    n_sec, n_usecs;

    n_sec = n_msecs / 1000;
    n_usecs = (n_msecs % 1000) * 1000L;

    new_timeset.it_interval.tv_sec  = n_sec;    /* set reload  */
    new_timeset.it_interval.tv_usec = n_usecs;  /* new ticker value */
    new_timeset.it_value.tv_sec     = n_sec  ;  /* store this   */
    new_timeset.it_value.tv_usec    = n_usecs ; /* and this     */

    
    if (setitimer(ITIMER_REAL, &new_timeset, &old_timeset) != 0 ){
        printf("Error with timer..errno=%d\n", errno );
        return -1;
    }
    return 0;
}

static void my_handler(int);

void millisleep( int n )
{
    signal(SIGALRM , my_handler);  /* set handler      */
    set_ticker(n);                 /* set alarm timer  */
    pause();                       /* wait for sigalrm */
}
static void
my_handler(int s)
{
    set_ticker(0);                 /* turns off ticker */
}