[libevent源码分析] event_set

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

voidevent_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NULLmin_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：

intevent_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_basereturn (-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

intevent_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。。。

intevent_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