int _xtimer_set_absolute(xtimer_t *timer, uint32_t target)
{
uint32_t now = xtimer_now();
int res = 0;
DEBUG("timer_set_absolute(): now=%" PRIu32 " target=%" PRIu32 "\n", now, target);
timer->next = NULL;
if ((target >= now) && ((target - XTIMER_BACKOFF) < now)) {
/* backoff */
xtimer_spin_until(target + XTIMER_BACKOFF);
_shoot(timer);
return 0;
}
unsigned state = irq_disable();
if (_is_set(timer)) {
_remove(timer);
}
timer->target = target;
timer->long_target = _long_cnt;
if (target < now) {
timer->long_target++;
}
if ( (timer->long_target > _long_cnt) || !_this_high_period(target) ) {
DEBUG("xtimer_set_absolute(): the timer doesn't fit into the low-level timer's mask.\n");
_add_timer_to_long_list(&long_list_head, timer);
}
else {
if (_xtimer_lltimer_mask(now) >= target) {
DEBUG("xtimer_set_absolute(): the timer will expire in the next timer period\n");
_add_timer_to_list(&overflow_list_head, timer);
}
else {
DEBUG("timer_set_absolute(): timer will expire in this timer period.\n");
_add_timer_to_list(&timer_list_head, timer);
if (timer_list_head == timer) {
DEBUG("timer_set_absolute(): timer is new list head. updating lltimer.\n");
_lltimer_set(target - XTIMER_OVERHEAD);
}
}
}
irq_restore(state);
return res;
}
/**
* @brief parse long timers list and copy those that will expire in the current
* short timer period
*/
static void _select_long_timers(void)
{
xtimer_t *select_list_start = long_list_head;
xtimer_t *select_list_last = NULL;
/* advance long_list head so it points to the first timer of the next (not
* just started) "long timer period" */
while (long_list_head) {
if ((long_list_head->long_target <= _long_cnt) && _this_high_period(long_list_head->target)) {
select_list_last = long_list_head;
long_list_head = long_list_head->next;
}
else {
/* remaining long_list timers belong to later long periods */
break;
}
}
/* cut the "selected long timer list" at the end */
if (select_list_last) {
select_list_last->next = NULL;
}
/* merge "current timer list" and "selected long timer list" */
if (timer_list_head) {
if (select_list_last) {
/* both lists are non-empty. merge. */
timer_list_head = _merge_lists(timer_list_head, select_list_start);
}
else {
/* "selected long timer list" is empty, nothing to do */
}
}
else { /* current timer list is empty */
if (select_list_last) {
/* there's no current timer list, but a non-empty "selected long
* timer list". So just use that list as the new current timer
* list.*/
timer_list_head = select_list_start;
}
}
}