[libevent源码分析] event_add

int event_add(struct event *ev, const struct timeval *tv) { struct event_base *base = ev->ev_base; //event_add 会把event加入到他的ev_base成员里 const struct eventop *evsel = base->evsel; //对应linux的epoll相干函数 void *evbase = base->evbase; //对应linux为 struct epollop /* * struct epollop * { * struct evepoll *fds; //分配nfiles个evepoll对象 * int nfds; //支持的最大软限制数的句柄(上面的数组个数) * struct epoll_event* events; //分配nfiles(软限制数) epoll_event对象 * int nevents; //nevents保存着上面events个数 * int epfd; //保存着epoll_create的句柄 * } */ int res = 0; event_debug(( "event_add: event: %p, %s%s%scall %p", ev, ev->ev_events & EV_READ ? "EV_READ " : " ", ev->ev_events & EV_WRITE ? "EV_WRITE " : " ", tv ? "EV_TIMEOUT " : " ", ev->ev_callback)); assert(!(ev->ev_flags & ~EVLIST_ALL)); if (tv != NULL && !(ev->ev_flags & EVLIST_TIMEOUT)) { if (min_heap_reserve(&base->timeheap, 1 + min_heap_size(&base->timeheap)) == ⑴) return (⑴); /* ENOMEM == errno */ } if ((ev->ev_events & (EV_READ|EV_WRITE|EV_SIGNAL)) && !(ev->ev_flags & (EVLIST_INSERTED|EVLIST_ACTIVE))) { res = evsel->add(evbase, ev); //注册or修改事件到epoll中去 if (res != ⑴) event_queue_insert(base, ev, EVLIST_INSERTED); //把ev插入到eventqeue中去 } /* * 如果说插入事件成功同时设置了超时时间 */ if (res != ⑴ && tv != NULL) { struct timeval now; /* *如果已存在了超时时间,那末就删除这个超时节点 */ if (ev->ev_flags & EVLIST_TIMEOUT) event_queue_remove(base, ev, EVLIST_TIMEOUT); /* Check if it is active due to a timeout. Rescheduling * this timeout before the callback can be executed * removes it from the active list. */ if ((ev->ev_flags & EVLIST_ACTIVE) && (ev->ev_res & EV_TIMEOUT)) { /* See if we are just active executing this * event in a loop */ if (ev->ev_ncalls && ev->ev_pncalls) { /* Abort loop */ *ev->ev_pncalls = 0; } event_queue_remove(base, ev, EVLIST_ACTIVE); } gettime(base, &now); evutil_timeradd(&now, tv, &ev->ev_timeout); event_debug(( "event_add: timeout in %ld seconds, call %p", tv->tv_sec, ev->ev_callback)); event_queue_insert(base, ev, EVLIST_TIMEOUT);//加入到最小超时堆中去 } return (res); }

static int epoll_add(void *arg, struct event *ev) { struct epollop *epollop = arg; struct epoll_event epev = {0, {0}}; struct evepoll *evep; int fd, op, events; /* * 信号的原理 * 1 设置信号处理函数，保存原来的信号处理函数到event的ev_base->sh_old中去 * 2 如果是首次添加信号，那末需要为所有信号追加1个信号事件来源自event->ev_base->ev_signal * 同时设置event->ev_base->ev_signal->ev_signal_added,表示信号回调事件已设置了 * 3 同时把事件追加到event->ev_base->ev_signal->evsigevents[signno]链表中去 */ if (ev->ev_events & EV_SIGNAL) //如果是加入的信号 return (evsignal_add(ev)); fd = ev->ev_fd; if (fd >= epollop->nfds) { /* Extent the file descriptor array as necessary */ //如果说当前的epoll中已满足不了新加入的句柄 if (epoll_recalc(ev->ev_base, epollop, fd) == ⑴) return (⑴); } evep = &epollop->fds[fd]; op = EPOLL_CTL_ADD; events = 0; //如果事件之前是可读 if (evep->evread != NULL) { events |= EPOLLIN; op = EPOLL_CTL_MOD; } //如果事件之前是可写 if (evep->evwrite != NULL) { events |= EPOLLOUT; op = EPOLL_CTL_MOD; } //新加入事件设置的是可读事件 if (ev->ev_events & EV_READ) events |= EPOLLIN; //新加入事件设置的是可写事件 if (ev->ev_events & EV_WRITE) events |= EPOLLOUT; epev.data.ptr = evep; epev.events = events; if (epoll_ctl(epollop->epfd, op, ev->ev_fd, &epev) == ⑴) return (⑴); /* Update events responsible */ if (ev->ev_events & EV_READ) evep->evread = ev; if (ev->ev_events & EV_WRITE) evep->evwrite = ev; return (0); }

int evsignal_add(struct event *ev) { int evsignal; struct event_base *base = ev->ev_base; //信号event的base struct evsignal_info *sig = &ev->ev_base->sig; //信号在ev_base的管理结构 if (ev->ev_events & (EV_READ|EV_WRITE)) //信号事件不支持可读可写事件 event_errx(1, "%s: EV_SIGNAL incompatible use", __func__); evsignal = EVENT_SIGNAL(ev); //信号的fd就是信号number assert(evsignal >= 0 && evsignal < NSIG); //信号不能超过NSIG这个数 if (TAILQ_EMPTY(&sig->evsigevents[evsignal])) { //如果说该信号链表为空 event_debug(("%s: %p: changing signal handler", __func__, ev)); //设置信号处理函数，同时，保存原来的信号处理函数到ev_base->sh_old中去 if (_evsignal_set_handler( base, evsignal, evsignal_handler) == ⑴) return (⑴); /* catch signals if they happen quickly */ evsignal_base = base; if (!sig->ev_signal_added) { if (event_add(&sig->ev_signal, NULL)) return (⑴); sig->ev_signal_added = 1; //加入epoll_wait中去 } } //把ev->ev_signal_next加入到sig->evsigevents[evsignal]的链表末端 /* multiple events may listen to the same signal */ TAILQ_INSERT_TAIL(&sig->evsigevents[evsignal], ev, ev_signal_next); return (0); }

/* * 所有的信号都通用1个信号处理函数 */ static void evsignal_handler(int sig) { int save_errno = errno; //保存毛病码 if (evsignal_base == NULL) { event_warn( "%s: received signal %d, but have no base configured", __func__, sig); return; } evsignal_base->sig.evsigcaught[sig]++; //引发的信号number++ evsignal_base->sig.evsignal_caught = 1; //设置信号标志，表示信号已触发 #ifndef HAVE_SIGACTION signal(sig, evsignal_handler); #endif /* Wake up our notification mechanism */ send(evsignal_base->sig.ev_signal_pair[0], "a", 1, 0); //通过写sockpair写数据来触发epoll_wait返回 errno = save_errno; }