[libevent源码分析] event_init

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相干的内容, //由于每种网络接口都不1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1个2维数组,第1维用于权限number，越低越高，第2维为激活列表 int nactivequeues; // 激活权限列表有多少个权限 struct evsignal_info sig; //保存着信号相干的内容 struct event_list eventqueue; //保存着注册的事件列表 struct timeval event_tv; //用于和tv_cache肯定是不是时间被修改了，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; };

struct event_base * event_init(void) { struct event_base *base = event_base_new(); if (base != NULL) current_base = base;//如果创建成功那末就会把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1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; //检测系统是不是可使用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); //初始化用于信号通讯的socket,使用的是sockpair unix网络套接字 base->sig.ev_signal_pair[0] = ⑴; base->sig.ev_signal_pair[1] = ⑴; base->evbase = NULL; for (i = 0; eventops[i] && !base->evbase; i++) { //event会优先选择epoll，这个数组是依照索引优先权降落 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 ", 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 (⑴); //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1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2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); }