[libevent源码分析] event_init

标签：tcp libevent   二维数组   源码   框架   网络   

struct event_base {
	const struct eventop *evsel;      //lievent支持select epoll kequeue..等网络api,包括init、add、del、dispatch的接口,每种网络框架都支持
	void *evbase;                     //支持相应网络api的 结构对象，必须epoll就是epoll_create返回epfd相关的内容,
    //因为每种网络接口都不一样，所以需要使用void*
	int event_count;		          //总网络事件数
	int event_count_active;	          //激活事件数

	int event_gotterm;		         //event_base_dispatch中终止while循环
	int event_break;		         //event_base_dispatch终止while立刻

	struct event_list **activequeues;//用于保存激活事件列表，是一个二维数组,第一维用于权限number，越低越高，第二维为激活列表
	int nactivequeues;              // 激活权限列表有多少个权限

	struct evsignal_info sig;       //保存着信号相关的内容

	struct event_list eventqueue;   //保存着注册的事件列表
	struct timeval event_tv;        //用于和tv_cache确定是否时间被修改了，如果使用monotonic时间是不被修改的，gettimeofday才会用到

	struct min_heap timeheap;       //用于时间堆（最小堆）管理

	struct timeval tv_cache;
};

代码如下

struct event_base *
event_init(void)
{
	struct event_base *base = event_base_new();

	if (base != NULL)
		current_base = base;//如果创建成功那么就会把current_base更新为新创建的base

	return (base);
}

struct event_base *
event_base_new(void)
{
	int i;
	struct event_base *base;

    //先创建一个even_base对象
	if ((base = calloc(1, sizeof(struct event_base))) == NULL)
		event_err(1, "%s: calloc", __func__);

	event_sigcb = NULL;
	event_gotsig = 0;

    //检测系统是否可以使用MONOTONIC time
	detect_monotonic();
    //填充base->event_tv记录创建base的时间
	gettime(base, &base->event_tv);
	
    //初始化最小定时器堆，p n a都置为0
	min_heap_ctor(&base->timeheap);
    //初始化队列first = NULL and last = &first
	TAILQ_INIT(&base->eventqueue);
    //初始化用于信号通信的socket,使用的是sockpair unix网络套接字
	base->sig.ev_signal_pair[0] = -1;
	base->sig.ev_signal_pair[1] = -1;
	
	base->evbase = NULL;
	for (i = 0; eventops[i] && !base->evbase; i++) {
    //event会优先选择epoll，这个数组是按照索引优先权下降
		base->evsel = eventops[i];

		base->evbase = base->evsel->init(base);
	}

	if (base->evbase == NULL)
		event_errx(1, "%s: no event mechanism available", __func__);

	if (getenv("EVENT_SHOW_METHOD")) 
		event_msgx("libevent using: %s\n",
			   base->evsel->name);

	/* allocate a single active event queue */
	event_base_priority_init(base, 1);

	return (base);
}

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

	if (base->event_count_active)
		return (-1);
    //先释放
	if (base->nactivequeues && npriorities != base->nactivequeues) {
		for (i = 0; i < base->nactivequeues; ++i) {
			free(base->activequeues[i]);
		}
		free(base->activequeues);
	}

	/* Allocate our priority queues */
    //先分配一维权限数组
	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__);

    //再初始化二维激活事件列表
	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);
}

[libevent源码分析] event_init

标签：tcp libevent   二维数组   源码   框架   网络   

原文地址：http://blog.csdn.net/youkuxiaobin/article/details/44112653