#include	"u.h"
#include	"lib.h"
#include	"mem.h"
#include	"dat.h"
#include	"fns.h"
#include	"io.h"

Alarm	*alarmtab;
Alarms	alarms;

Alarm*
alarm(int ms, void (*f)(Alarm*), void *arg)
{
	Alarm *a, *w, *pw;
	ulong s;
	if(ms < 0)
		ms = 0;
	a = newalarm();
	a->dt = MS2TK(ms);
	a->f = f;
	a->arg = arg;
	s = splhi();
	lock(&m->alarmlock);
	pw = 0;
	for(w=m->alarm; w; pw=w, w=w->next){
		if(w->dt <= a->dt){
			a->dt -= w->dt;
			continue;
		}
		w->dt -= a->dt;
		break;
	}
	insert(&m->alarm, pw, a);
	unlock(&m->alarmlock);
	splx(s);
	return a;
}

void
cancel(Alarm *a)
{
	a->f = 0;
}

Alarm*
newalarm(void)
{
	int i;
	Alarm *a;

	for(i=0,a=alarmtab; i<conf.nalarm; i++,a++)
		if(a->busy==0 && a->f==0 && canlock(a)){
			if(a->busy){
				unlock(a);
				continue;
			}
			a->f = 0;
			a->arg = 0;
			a->busy = 1;
			unlock(a);
			return a;
		}
	panic("newalarm");
	return 0;	/* not reached */
}

void
alarminit(void)
{
	int i;

	alarmtab = ialloc(conf.nalarm*sizeof(Alarm), 0);
	for(i=0; i<conf.nalarm; i++){
		lock(&alarmtab[i]);	/* allocate locks, as they are used at interrupt time */
		unlock(&alarmtab[i]);
	}
	qlock(&alarms);
	qunlock(&alarms);
}

#define NA 10		/* alarms per clock tick */
void
checkalarms(void)
{
	int i, n;
	Alarm *a;
	void (*f)(void*);
	Alarm *alist[NA];
	ulong now;
	Proc *rp;

	if(canlock(&m->alarmlock)){
		a = m->alarm;
		if(a){
			for(n=0; a && a->dt<=0 && n<NA; n++){
				alist[n] = a;
				delete(&m->alarm, 0, a);
				a = m->alarm;
			}
			if(a)
				a->dt--;
			unlock(&m->alarmlock);

			/*  execute alarm functions outside the lock */
			for(i = 0; i < n; i++){
				f = alist[i]->f;	/* avoid race with cancel */
				if(f)
					(*f)(alist[i]);
				alist[i]->busy = 0;
			}
		} else
			unlock(&m->alarmlock);
	}

	if(m == MACHP(0) && canqlock(&alarms)) {
		now = MACHP(0)->ticks;
		while((rp = alarms.head) && rp->alarm <= now) {
			if(rp->alarm != 0L) {
				if(canlock(&rp->debug)) {
					postnote(rp, 0, "alarm", NUser);
					unlock(&rp->debug);
					rp->alarm = 0L;
				}
				else
					break;
			}
			alarms.head = rp->palarm;
		}
		qunlock(&alarms);
	}
}

ulong
procalarm(ulong time)
{
	Proc **l, *f;
	ulong when, old;

	when = MS2TK(time);
	old = u->p->alarm - MACHP(0)->ticks;
	if(when == 0) {
		u->p->alarm = 0;
		return TK2MS(old);
	}
	else
		when += MACHP(0)->ticks;

	qlock(&alarms);
	l = &alarms.head;
	for(f = *l; f; f = f->palarm) {
		if(u->p == f) {
			*l = f->palarm;
			break;
		}
		l = &f->palarm;
	}

	u->p->palarm = 0;
	if(alarms.head) {
		l = &alarms.head;
		for(f = *l; f; f = f->palarm) {
			if(f->alarm > when) {
				u->p->palarm = f;
				*l = u->p;
				goto done;
			}
			l = &f->palarm;
		}
		*l = u->p;
	}
	else
		alarms.head = u->p;
done:
	u->p->alarm = when;
	qunlock(&alarms);

	return TK2MS(old);			
}

/*
 * Insert new into list after where
 */
void
insert(List **head, List *where, List *new)
{
	if(where == 0){
		new->next = *head;
		*head = new;
	}else{
		new->next = where->next;
		where->next = new;
	}
		
}

/*
 * Delete old from list.  where->next is known to be old.
 */
void
delete(List **head, List *where, List *old)
{
	if(where == 0){
		*head = old->next;
		return;
	}
	where->next = old->next;
}