Libevent源码分析—event_set()

void
event_set(struct event *ev, int fd, short events,
      void (*callback)(int, short, void *), void *arg)
{
    /* Take the current base - caller needs to set the real base later */
    ev->ev_base = current_base;    //设置event属于当前base；current_base通过event_init()设置
    ev->ev_callback = callback;    //设置回调函数
    ev->ev_arg = arg;    //设置回调函数的3个参数
    ev->ev_fd = fd;
    ev->ev_events = events;
    ev->ev_res = 0;
    ev->ev_flags = EVLIST_INIT;    //设置event状态
    ev->ev_ncalls = 0;
    ev->ev_pncalls = NULL;
    min_heap_elem_init(ev);    //初始化event在小根堆中索引为-1    min_heap.h
    /* by default, we put new events into the middle priority */
    if(current_base)
        ev->ev_pri = current_base->nactivequeues/2;    //设置event优先级
}

int
event_base_set(struct event_base *base, struct event *ev)
{
    /* Only innocent events may be assigned to a different base */
    if (ev->ev_flags != EVLIST_INIT)    //只能对新建的event设置其所属event_base
        return (-1);
    ev->ev_base = base;    //设置所属event_base
    ev->ev_pri = base->nactivequeues/2;    //设置优先级
    return (0);
}

int
event_priority_set(struct event *ev, int pri)
{
    if (ev->ev_flags & EVLIST_ACTIVE)    //不能对活跃的event设置优先级
        return (-1);
    if (pri < 0 || pri >= ev->ev_base->nactivequeues)
        return (-1);
    ev->ev_pri = pri;    //设置优先级
    return (0);
}