13.Redis事件模型
void aeMain(aeEventLoop *eventLoop) {
eventLoop->stop = 0;
while (!eventLoop->stop) {
// 進入事件迴圈可能會進入睡眠狀態。在睡眠之前，執行預設定的函式 aeSetBeforeSleepProc()。
if (eventLoop->beforesleep != NULL)
eventLoop->beforesleep(eventLoop);
// AE_ALL_EVENTS 表示處理所有的事件
aeProcessEvents(eventLoop, AE_ALL_EVENTS);
}
}
// 先處理定時事件，然後處理套接字事件
int aeProcessEvents(aeEventLoop *eventLoop, int flags)
{
int processed = 0, numevents;
/* Nothing to do? return ASAP */
if (!(flags & AE_TIME_EVENTS) && !(flags & AE_FILE_EVENTS)) return 0;
/* Note that we want call select() even if there are no
* file events to process as long as we want to process time
* events, in order to sleep until the next time event is ready
* to fire. */
if (eventLoop->maxfd != -1 ||
((flags & AE_TIME_EVENTS) && !(flags & AE_DONT_WAIT))) {
int j;
aeTimeEvent *shortest = NULL;
// tvp 會在 IO 多路複用的函式呼叫中用到，表示超時時間
struct timeval tv, *tvp;
// 得到最短將來會發生的定時事件
if (flags & AE_TIME_EVENTS && !(flags & AE_DONT_WAIT))
shortest = aeSearchNearestTimer(eventLoop);
// 計算睡眠的最短時間
if (shortest) { // 存在定時事件
long now_sec, now_ms;
/* Calculate the time missing for the nearest
* timer to fire. */
// 得到當前時間
aeGetTime(&now_sec, &now_ms);
tvp = &tv;
tvp->tv_sec = shortest->when_sec - now_sec;
if (shortest->when_ms < now_ms) { // 需要借位
// 減法中的借位，毫秒向秒借位
tvp->tv_usec = ((shortest->when_ms+1000) - now_ms)*1000;
tvp->tv_sec --;
} else { // 不需要借位，直接減
tvp->tv_usec = (shortest->when_ms - now_ms)*1000;
}
// 當前系統時間已經超過定時事件設定的時間
if (tvp->tv_sec < 0) tvp->tv_sec = 0;
if (tvp->tv_usec < 0) tvp->tv_usec = 0;
} else {
/* If we have to check for events but need to return
* ASAP because of AE_DONT_WAIT we need to set the timeout
* to zero */
// 如果沒有定時事件，見機行事
if (flags & AE_DONT_WAIT) {
tv.tv_sec = tv.tv_usec = 0;
tvp = &tv;
} else {
/* Otherwise we can block */
tvp = NULL; /* wait forever */
}
}
// 呼叫 IO 多路複用函式阻塞監聽
numevents = aeApiPoll(eventLoop, tvp);
// 處理已經觸發的事件
for (j = 0; j < numevents; j++) {
// 找到 I/O 事件表中儲存的資料
aeFileEvent *fe = &eventLoop->events[eventLoop->fired[j].fd];
int mask = eventLoop->fired[j].mask;
int fd = eventLoop->fired[j].fd;
int rfired = 0;
/* note the fe->mask & mask & ... code: maybe an already processed
* event removed an element that fired and we still didn't
* processed, so we check if the event is still valid. */
// 讀事件
if (fe->mask & mask & AE_READABLE) {
rfired = 1;
fe->rfileProc(eventLoop,fd,fe->clientData,mask);
}
// 寫事件
if (fe->mask & mask & AE_WRITABLE) {
if (!rfired || fe->wfileProc != fe->rfileProc)
fe->wfileProc(eventLoop,fd,fe->clientData,mask);
}
processed++;
}
}
// 處理定時事件
/* Check time events */
if (flags & AE_TIME_EVENTS)
processed += processTimeEvents(eventLoop);
return processed; /* return the number of processed file/time events */
}