編輯：關於Android編程
因此帶來CPU和內存的雙重開銷、但達到單機10G+ cache以及QPS上萬之後這些開銷就會給雙方相對帶來一些
細微性能差別。
基本的數據結構：@ae.h
//定義文件事件處理接口（函數指針）
typedef void aeFileProc(struct aeEventLoop *eventLoop, int fd, void *clientData, int mask); //時間事件處理接口（函數指針），該函數返回定時的時長 typedef int aeTimeProc(struct aeEventLoop *eventLoop, long long id, void *clientData); typedef void aeEventFinalizerProc(struct aeEventLoop *eventLoop, void *clientData); //aeMain中使用，在調用處理事件前調用 typedef void aeBeforeSleepProc(struct aeEventLoop *eventLoop);
//文件事件結構體
typedef struct aeFileEvent {
//讀或者寫，也用於標識該事件結構體是否正在使用
int mask; /* one of AE_(READABLE|WRITABLE) */
//讀事件的處理函數
aeFileProc *rfileProc;
//寫事件的處理函數
aeFileProc *wfileProc;
//傳遞給上述兩個函數的數據
void *clientData;
} aeFileEvent;
//時間事件
typedef struct aeTimeEvent {
//時間事件標識符，用於唯一標識該時間事件，並且用於刪除時間事件
long long id; /* time event identifier. */
long when_sec; /* seconds */
long when_ms; /* milliseconds */
//該事件對應的處理程序
aeTimeProc *timeProc;
//時間事件的最後一次處理程序，若已設置，則刪除時間事件時會被調用
aeEventFinalizerProc *finalizerProc;
void *clientData;
struct aeTimeEvent *next;
} aeTimeEvent;
//這裡用於保存已觸發的事件
typedef struct aeFiredEvent {
int fd;
int mask;
} aeFiredEvent;
/* State of an event based program */
typedef struct aeEventLoop {
//最大文件描述符的值
int maxfd; /* highest file descriptor currently registered */
//文件描述符的最大監聽數
int setsize; /* max number of file descriptors tracked */
//用於生成時間事件的唯一標識id
long long timeEventNextId;
//用於檢測系統時間是否變更（判斷標准 now
typedef struct aeApiState {
int epfd;
struct epoll_event *events;
} aeApiState;
//ae底層的數據創建以及初始化
static int aeApiCreate(aeEventLoop *eventLoop) {
aeApiState *state = zmalloc(sizeof(aeApiState));
if (!state) return -1;
//創建setsize個epoll_event
state->events = zmalloc(sizeof(struct epoll_event)*eventLoop->setsize);
if (!state->events) {
zfree(state);
return -1;
}
state->epfd = epoll_create(1024); /* 1024 is just a hint for the kernel */
if (state->epfd == -1) {
zfree(state->events);
zfree(state);
return -1;
}
eventLoop->apidata = state;
return 0;
}
//創建事件循環，setsize為最大事件的的個數，對於epoll來說也是epoll_event的個數
aeEventLoop *aeCreateEventLoop(int setsize) {
aeEventLoop *eventLoop;
int i;
//分配該結構體的內存空間
if ((eventLoop = zmalloc(sizeof(*eventLoop))) == NULL) goto err;
eventLoop->events = zmalloc(sizeof(aeFileEvent)*setsize);
eventLoop->fired = zmalloc(sizeof(aeFiredEvent)*setsize);
if (eventLoop->events == NULL || eventLoop->fired == NULL) goto err;
//初始化最多setsize個事件
eventLoop->setsize = setsize;
eventLoop->lastTime = time(NULL);
eventLoop->timeEventHead = NULL;
eventLoop->timeEventNextId = 0;
eventLoop->stop = 0;
eventLoop->maxfd = -1;
eventLoop->beforesleep = NULL;
//這一步為創建底層IO處理的數據，如epoll，創建epoll_event,和epfd
if (aeApiCreate(eventLoop) == -1) goto err;
/* Events with mask == AE_NONE are not set. So let's initialize the
* vector with it. */
for (i = 0; i < setsize; i++)
eventLoop->events[i].mask = AE_NONE;
return eventLoop;
err:
if (eventLoop) {
zfree(eventLoop->events);
zfree(eventLoop->fired);
zfree(eventLoop);
}
return NULL;
}
2、aeCreateFileEvent
對於創建文件事件，需要傳入一個該事件對應的處理程序，當事件發生時，會調用對應的回調函數。
這裡設計的aeFileEvent結構體就是將事件源（FD），事件，事件處理程序關聯起來。
//添加監聽的事件，其中如果該fd對應的事件已經存在，則為修改合並舊的事件
static int aeApiAddEvent(aeEventLoop *eventLoop, int fd, int mask) {
aeApiState *state = eventLoop->apidata;
struct epoll_event ee = {0}; /* avoid valgrind warning */
/* If the fd was already monitored for some event, we need a MOD
* operation. Otherwise we need an ADD operation. */
//判斷fd是否已經添加了事件的監聽
int op = eventLoop->events[fd].mask == AE_NONE ?
EPOLL_CTL_ADD : EPOLL_CTL_MOD;
ee.events = 0;
mask |= eventLoop->events[fd].mask; /* Merge old events */
if (mask & AE_READABLE) ee.events |= EPOLLIN;
if (mask & AE_WRITABLE) ee.events |= EPOLLOUT;
ee.data.fd = fd;
if (epoll_ctl(state->epfd,op,fd,&ee) == -1) return -1;
return 0;
}
//刪除指定事件的監聽
static void aeApiDelEvent(aeEventLoop *eventLoop, int fd, int delmask) {
aeApiState *state = eventLoop->apidata;
struct epoll_event ee = {0}; /* avoid valgrind warning */
int mask = eventLoop->events[fd].mask & (~delmask);
ee.events = 0;
if (mask & AE_READABLE) ee.events |= EPOLLIN;
if (mask & AE_WRITABLE) ee.events |= EPOLLOUT;
ee.data.fd = fd;
if (mask != AE_NONE) {
epoll_ctl(state->epfd,EPOLL_CTL_MOD,fd,&ee);
} else {
/* Note, Kernel < 2.6.9 requires a non null event pointer even for
* EPOLL_CTL_DEL. */
epoll_ctl(state->epfd,EPOLL_CTL_DEL,fd,&ee);
}
}
//創建文件事件，並將該事件注冊到eventLoop中
int aeCreateFileEvent(aeEventLoop *eventLoop, int fd, int mask,
aeFileProc *proc, void *clientData)
{
if (fd >= eventLoop->setsize) {
errno = ERANGE;
return AE_ERR;
}
//直接使用fd來獲取FileEvent，來後面分離事件時也采用這種方法（直接索引）
aeFileEvent *fe = &eventLoop->events[fd];
//該該事件添加eventLoop中或者修改原來的已有的（保留舊的）
if (aeApiAddEvent(eventLoop, fd, mask) == -1)
return AE_ERR;
fe->mask |= mask;
//將該事件的處理程序放到對應的位置
if (mask & AE_READABLE) fe->rfileProc = proc;
if (mask & AE_WRITABLE) fe->wfileProc = proc;
//設置將要傳遞給該事件處理程序的數據
fe->clientData = clientData;
if (fd > eventLoop->maxfd)
eventLoop->maxfd = fd;
return AE_OK;
}
static int aeApiPoll(aeEventLoop *eventLoop, struct timeval *tvp) {
aeApiState *state = eventLoop->apidata;
int retval, numevents = 0;
//等待事件產生
retval = epoll_wait(state->epfd,state->events,eventLoop->setsize,
tvp ? (tvp->tv_sec*1000 + tvp->tv_usec/1000) : -1);
if (retval > 0) {
int j;
numevents = retval;
for (j = 0; j < numevents; j++) {
int mask = 0;
struct epoll_event *e = state->events+j;
if (e->events & EPOLLIN) mask |= AE_READABLE;
if (e->events & EPOLLOUT) mask |= AE_WRITABLE;
if (e->events & EPOLLERR) mask |= AE_WRITABLE;
if (e->events & EPOLLHUP) mask |= AE_WRITABLE;
// 利用fired數組記錄觸發的事件
eventLoop->fired[j].fd = e->data.fd;
eventLoop->fired[j].mask = mask;
}
}
return numevents;
}
//事件處理程序
int aeProcessEvents(aeEventLoop *eventLoop, int flags)
{
int processed = 0, numevents;
//若什麼都沒有設置，則直接返回
/* Nothing to do? return ASAP */
if (!(flags & AE_TIME_EVENTS) && !(flags & AE_FILE_EVENTS)) return 0;
//如果有文件事件或者設置了時間事件並且沒有設置DONT_WAIT標志
/* 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;
struct timeval tv, *tvp;
if (flags & AE_TIME_EVENTS && !(flags & AE_DONT_WAIT))
//查找時間最早的時間事件
shortest = aeSearchNearestTimer(eventLoop);
if (shortest) {
long now_sec, now_ms;
aeGetTime(&now_sec, &now_ms);
tvp = &tv;
/* How many milliseconds we need to wait for the next
* time event to fire? */
long long ms =
(shortest->when_sec - now_sec)*1000 +
shortest->when_ms - now_ms;
// 找到最早的時間事件與當前時間差值就是epoll wait時間
if (ms > 0) {
tvp->tv_sec = ms/1000;
tvp->tv_usec = (ms % 1000)*1000;
} else {
tvp->tv_sec = 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 */
if (flags & AE_DONT_WAIT) {
tv.tv_sec = tv.tv_usec = 0;
tvp = &tv;
} else {
//如果沒有時間事件則可以阻塞、如果此時加入一個Timer event，啥時候喚醒呢？！
/* Otherwise we can block */
tvp = NULL; /* wait forever */
}
}
numevents = aeApiPoll(eventLoop, tvp);
for (j = 0; j < numevents; j++) {
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. */
if (fe->mask & mask & AE_READABLE) {
rfired = 1;
fe->rfileProc(eventLoop,fd,fe->clientData,mask);
}
if (fe->mask & mask & AE_WRITABLE) {
//這裡的判斷是為了防止重復調用
if (!rfired || fe->wfileProc != fe->rfileProc)
fe->wfileProc(eventLoop,fd,fe->clientData,mask);
}
processed++;
}
}
/* Check time events */
if (flags & AE_TIME_EVENTS)
processed += processTimeEvents(eventLoop);
return processed; /* return the number of processed file/time events */
}
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