[libevent源码分析] event

libevent使用event来封装网络事件回调，参数、fd。。。等一些信息,函数很简单

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; //设置成默认的current_base,如果

	ev->ev_callback = callback; //设置事件回调callback;
	ev->ev_arg = arg;           //设置参数
	ev->ev_fd = fd;             //设置句柄
	ev->ev_events = events;     //设置当前的事件
    /*
     * EV_TIMEOUT   0x01
     * EV_READ      0x02
     * EV_WRITE     0x04
     * EV_SIGNAL    0x08
     * EV_PERSIST   0x10
     */
	ev->ev_res = 0;             //记录当前激活事件的类型
	ev->ev_flags = EVLIST_INIT; //设置事件标志，用于表示当前的事件处于什么阶段
    /*
     * EVLIST_TIMEOUT   0x01     //代表event在time堆中
     * EVLIST_INSERTED  0x02     //代表event在已注册时间链表中
     * EVLIST_SIGNAL    0x04     //未见使用
     * EVLIST_ACTIVE    0x08     //代表event在激活链表中
     * EVLIST_INTERNAL  0x10     //内部使用标记
     * EVLIST_INIT      0x80     //代表event已经被初始化
     */
	ev->ev_ncalls = 0;           //代表callback被执行多少次
	ev->ev_pncalls = NULL;       //指向ev_ncallsor指向NULL

	min_heap_elem_init(ev);      //初始化时间堆中的索引值

	/* by default,we put new events into the middle priority */
	if(current_base)
		ev->ev_pri = current_base->nactivequeues/2;//设置事件的权限为中间权限为默认值
}

使用libevent在多线程中，就会存在多个event_base来进行reactor事件模型,就需要对struct event设置所归属的event_base
调用的函数如下：

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)//仅仅处在初始化中的事件对象才可以设置base,用于更新ev_base
		return (-1);

	ev->ev_base = base;
	ev->ev_pri = base->nactivequeues/2;

	return (0);
}

这样当每个线程都存在一个event_base的时候，那么就可以根据event所属的线程来设置当前的event_base,
如果不设置event_base而使用默认,那么会使用current_base,current_base设置成最后一个创建的event_base对象

设置事件权限，这个函数一般都是刚创建完event_base的使用，因为它使用的是current_base

int
event_priority_init(int npriorities)
{
  return event_base_priority_init(current_base,npriorities);
}

//重新设置event_base权限，一维是最高的。。。

int
event_base_priority_init(struct event_base *base,int npriorities)
{
int i;


if (base->event_count_active)
return (-1);


if (base->nactivequeues && npriorities != base->nactivequeues) {
for (i = 0; i < base->nactivequeues; ++i) {
free(base->activequeues[i]);
}
free(base->activequeues);
}


/* Allocate our priority queues */
base->nactivequeues = npriorities;
base->activequeues = (struct event_list **)calloc(base->nactivequeues,npriorities * sizeof(struct event_list *));
if (base->activequeues == NULL)
event_err(1,"%s: calloc",__func__);


for (i = 0; i < base->nactivequeues; ++i) {
base->activequeues[i] = malloc(sizeof(struct event_list));
if (base->activequeues[i] == NULL)
event_err(1,"%s: malloc",__func__);
TAILQ_INIT(base->activequeues[i]);
}


return (0);
}

libeven 整个源码分析和sample都在我的 githup

[libevent源码分析] event_set

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