redis源码笔记－ae

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 <sys/epoll.h>
 2 
 3 typedef struct aeApiState {
 4     int epfd;
 5     struct epoll_event events[AE_SETSIZE]; //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[fd].mask == AE_NONE ?
31             EPOLL_CTL_ADD : EPOLL_CTL_MOD;
32 
33     ee.events = 0;
34     mask |= eventLoop->events[fd].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[fd].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[j].fd = e->data.fd;
79             eventLoop->fired[j].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 }