[libevent源码分析] event_base_dispatch

剖析下事件重复 event_base_dispatch

int
event_base_dispatch(struct event_base *event_base)
{
  return (event_base_loop(event_base, 0));
}
int
event_base_loop(struct event_base *base, int flags)
{
	const struct eventop *evsel = base->evsel;
	void *evbase = base->evbase;
	struct timeval tv;
	struct timeval *tv_p;
	int res, done;

	/* clear time cache */
	base->tv_cache.tv_sec = 0;

	if (base->sig.ev_signal_added)
		evsignal_base = base;                       //如果说当前ev_base已参加了信号事件，那末就把ev_signal_base指向他
	done = 0;
	while (!done) {
        //终止事件重复
		/* Terminate the loop if we have been asked to */
		if (base->event_gotterm) {
			base->event_gotterm = 0;
			break;
		}

		if (base->event_break) {
			base->event_break = 0;
			break;
		}

		/* You cannot use this interface for multi-threaded apps */
		while (event_gotsig) {
			event_gotsig = 0;
			if (event_sigcb) {
				res = (*event_sigcb)();
				if (res == -1) {
					errno = EINTR;
					return (-1);
				}
			}
		}
        /* 这个函数就是获得当前时光保留在tv中，如果时光变更了，须要更新时光最小堆中的时光,重要是获得当前时光 */
		timeout_correct(base, &tv);

		tv_p = &tv;
		if (!base->event_count_active && !(flags & EVLOOP_NONBLOCK)) {
			timeout_next(base, &tv_p);
		} else {
			/* 
			 * if we have active events, we just poll new events
			 * without waiting.
			 */
            /*
             * 如果说还存在激活事件，那末就消除掉时光
             */
			evutil_timerclear(&tv);
		}
		
		/* If we have no events, we just exit */
		if (!event_haveevents(base)) {
			event_debug(("%s: no events registered.", __func__));
			return (1);
		}

		/* update last old time */
		gettime(base, &base->event_tv);

		/* clear time cache */
		base->tv_cache.tv_sec = 0;//清0是为了当有激活事件的时候，获得体系最新时光

		res = evsel->dispatch(base, evbase, tv_p);

		if (res == -1)
			return (-1);
		gettime(base, &base->tv_cache);//这里是每次通过体系调用获得的时光

        //处置超时事件，删除超时链表节点，同时参加到激活链表
		timeout_process(base);

		if (base->event_count_active) {
			event_process_active(base);
			if (!base->event_count_active && (flags & EVLOOP_ONCE))
				done = 1;
		} else if (flags & EVLOOP_NONBLOCK)
			done = 1;
	}

	/* clear time cache */
	base->tv_cache.tv_sec = 0;

	event_debug(("%s: asked to terminate loop.", __func__));
	return (0);
}int
event_base_dispat