redis源码笔记－ae_epoll.c
这部分代码是具体事件触发网络库的底层实现。Linux下有epoll设施，而且其效率是现在最高的。注意即使高效如redis，其也只是选择了自动档－水平触发（自动档和手动档的典故请自行google）。据说libevent也是使用的水平触发。废话不多说，看代码吧。1 #include
2
3 typedef struct aeApiState {
4 int epfd;
5 struct epoll_event events; //存的是epoll_wait返回后得到的事件列表
6 } aeApiState; //作为eventLoop结构的apidata存储
7
8 static int aeApiCreate(aeEventLoop *eventLoop) {
9 aeApiState *state = zmalloc(sizeof(aeApiState));
10
11 if (!state) return -1;
12 state->epfd = epoll_create(1024); /* 1024 is just an hint for the kernel */
13 if (state->epfd == -1) return -1;
14 eventLoop->apidata = state;
15 return 0;
16 }
17
18 static void aeApiFree(aeEventLoop *eventLoop) {
19 aeApiState *state = eventLoop->apidata;
20
21 close(state->epfd);
22 zfree(state);
23 }
24
25 static int aeApiAddEvent(aeEventLoop *eventLoop, int fd, int mask) {
26 aeApiState *state = eventLoop->apidata;
27 struct epoll_event ee;
28 /* If the fd was already monitored for some event, we need a MOD
29 * operation. Otherwise we need an ADD operation. */
30 int op = eventLoop->events.mask == AE_NONE ?
31 EPOLL_CTL_ADD : EPOLL_CTL_MOD;
32
33 ee.events = 0;
34 mask |= eventLoop->events.mask; /* Merge old events */
35 if (mask & AE_READABLE) ee.events |= EPOLLIN;
36 if (mask & AE_WRITABLE) ee.events |= EPOLLOUT;
37 ee.data.u64 = 0; /* avoid valgrind warning */
38 ee.data.fd = fd;
39 if (epoll_ctl(state->epfd,op,fd,&ee) == -1) return -1;
40 return 0;
41 }
42
43 static void aeApiDelEvent(aeEventLoop *eventLoop, int fd, int delmask) {
44 aeApiState *state = eventLoop->apidata;
45 struct epoll_event ee;
46 int mask = eventLoop->events.mask & (~delmask);
47
48 ee.events = 0;
49 if (mask & AE_READABLE) ee.events |= EPOLLIN;
50 if (mask & AE_WRITABLE) ee.events |= EPOLLOUT;
51 ee.data.u64 = 0; /* avoid valgrind warning */
52 ee.data.fd = fd;
53 if (mask != AE_NONE) {
54 epoll_ctl(state->epfd,EPOLL_CTL_MOD,fd,&ee);
55 } else {
56 /* Note, Kernel < 2.6.9 requires a non null event pointer even for
57 * EPOLL_CTL_DEL. */
58 epoll_ctl(state->epfd,EPOLL_CTL_DEL,fd,&ee);
59 }
60 }
61
62 static int aeApiPoll(aeEventLoop *eventLoop, struct timeval *tvp) {
63 aeApiState *state = eventLoop->apidata;
64 int retval, numevents = 0;
65
66 retval = epoll_wait(state->epfd,state->events,AE_SETSIZE,
67 tvp ? (tvp->tv_sec*1000 + tvp->tv_usec/1000) : -1);
68 if (retval > 0) {
69 int j;
70
71 numevents = retval;
72 for (j = 0; j < numevents; j++) {
73 int mask = 0;
74 struct epoll_event *e = state->events+j;
75
76 if (e->events & EPOLLIN) mask |= AE_READABLE;
77 if (e->events & EPOLLOUT) mask |= AE_WRITABLE;
78 eventLoop->fired.fd = e->data.fd;
79 eventLoop->fired.mask = mask;
//在fired数组里注册
80 }
81 }
82 return numevents;
83 }
84
85 static char *aeApiName(void) {
86 return "epoll";
87 }
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