This code is not intended to be taken literally!
 

struct event {
       struct event * next;   /* happy doubly-linked list */
       struct event * prev;
       struct timeval when;   /* time when the event should fire */
       void (*f)(void *);     /* callback to invoke at that time */
       void *a;               /* parameter to hand the callback */
};

struct event *eventlist;

struct timeval now, event_time, timeout;
gettimeofday ( &now, NULL );

event_time.tv_sec = now.tv_sec + 25
event_time.tv_usec = now.tv_usec

boolean timeval_is_less_than( struct timeval *a, struct timeval *b) {
  blah blah blah.
}

for(ptr = eventlist; ptr != NULL && [[[ptr-> when < event_time]]]; ptr =ptr-> next);
for(ptr = eventlist; ptr != NULL && 
        timeval_is_less_than(&ptr-> when, &event_time); 
        ptr =ptr-> next);
if(ptr) { 
  new_event->next = ptr
  new_event->prev = ptr->prev
    ptr->prev->next = new_event /* if not null!!! */
  ptr->prev = new_event
    } else {
  new_event->prev = last;
  last=new_event;
 }

select_timeout.tv_sec = eventlist -> when.tv_sec - now.tv_sec 
select_timeout.tv_usec = eventlist -> when.tv_usec - now.tv_usec 
/* then cleanup the carry */

number_of_ready_filedescriptors = 
  select(........, &select_timeout); /* wait for input on any socket */

FD_SET FD_ISSET 

gettimeofday(&now, NULL);
if ( timeval_is_less_than(&eventlist->when, &now) ) {
  eventlist->f(eventlist->a);
  eventlist=eventlist->next;
  free!
 }