minix/lib/libtimers/tmrs_set.c

   1 #include <minix/timers.h>
   2
   3 /*
   4  * Activate a timer to run function 'watchdog' at absolute time 'exp_time', as
   5  * part of timers queue 'tmrs'. If the timer is already in use, it is first
   6  * removed from the timers queue.  Then, it is put in the list of active timers
   7  * with the first to expire in front.  The caller responsible for scheduling a
   8  * new alarm for the timer if needed.  To that end, the function returns three
   9  * values: its return value (TRUE or FALSE) indicates whether there was an old
  10  * head timer; if TRUE, 'old_head' (if non-NULL) is filled with the absolute
  11  * expiry time of the old head timer.  If 'new_head' is non-NULL, it is filled
  12  * with the absolute expiry time of the new head timer.
  13  */
  14 int
  15 tmrs_settimer(minix_timer_t ** tmrs, minix_timer_t * tp, clock_t exp_time,
  16         tmr_func_t watchdog, int arg, clock_t * old_head, clock_t * new_head)
  17 {
  18         minix_timer_t **atp;
  19         int r;
  20
  21         if (*tmrs != NULL) {
  22                 if (old_head != NULL)
  23                         *old_head = (*tmrs)->tmr_exp_time;
  24                 r = TRUE;
  25         } else
  26                 r = FALSE;
  27
  28         /* Set the timer's variables. */
  29         if (tmr_is_set(tp))
  30                 (void)tmrs_clrtimer(tmrs, tp, NULL, NULL);
  31         tp->tmr_exp_time = exp_time;
  32         tp->tmr_func = watchdog;        /* set the timer object */
  33         tp->tmr_arg = arg;
  34
  35         /*
  36          * Add the timer to the active timers. The next timer due is in front.
  37          */
  38         for (atp = tmrs; *atp != NULL; atp = &(*atp)->tmr_next) {
  39                 if (tmr_is_first(exp_time, (*atp)->tmr_exp_time))
  40                         break;
  41         }
  42         tp->tmr_next = *atp;
  43         *atp = tp;
  44
  45         if (new_head != NULL)
  46                 *new_head = (*tmrs)->tmr_exp_time;
  47         return r;
  48 }