epoll的一个使用例子

使用到主要函数有：

#include <sys/epoll.h>
int epoll_create(int size);
int epoll_create1(int flags);
int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event);
int epoll_wait(int epfd, struct epoll_event *events, int maxevents, int timeout);

typedef union epoll_data {
　　void *ptr;
　　int fd;
　　uint32_t u32;
　　uint64_t u64;
} epoll_data_t;

struct epoll_event {
　　uint32_t events; /* Epoll events */
　　epoll_data_t data; /* User data variable */
};

 #define EPOLL_SIZE 1024
 int doServiceEpoll(int listenFd)
 {
     struct epoll_event events[EPOLL_SIZE];

     struct epoll_event event;
     int epollFd = epoll_create1(EPOLL_CLOEXEC);
     if(epollFd < ) {
         ERR_EXIT("epoll_create1");
     }

     event.data.fd = listenFd;
     event.events = EPOLLIN|EPOLLET;
     if(epoll_ctl(epollFd, EPOLL_CTL_ADD, listenFd, &event) < ) {
         ERR_EXIT("epoll_ctl");
     }

     int epollRet;
     int i;
     struct sockaddr_in cliAddr;
     socklen_t len;
     int acceptFd;
     int epollNum = ;
     int readNum;
     while() {
         epollRet = epoll_wait(epollFd, events, epollNum, -);
         if(epollRet < ) {
             ERR_EXIT("epollRet");
         } else if(epollRet == ) {
             continue;
         }

         for(i = ; i < epollRet; i++) {
             if(events[i].data.fd == listenFd) {
                 memset(&cliAddr, , sizeof(cliAddr));
                 len = sizeof(cliAddr);
                 if((acceptFd = accept(listenFd, (struct sockaddr *)&cliAddr, &len)) < ) {
                     ERR_EXIT("accept");
                 }
                 printf("recv a connect from %s, port %d, fd %d\n",
                     inet_ntoa(cliAddr.sin_addr), ntohs(cliAddr.sin_port), acceptFd);
                 epollNum++;
                 event.data.fd = acceptFd;
                 event.events = EPOLLIN|EPOLLET;
                 if(epoll_ctl(epollFd, EPOLL_CTL_ADD, event.data.fd , &event) < ) {
                     ERR_EXIT("epoll_ctl");
                 }
             }
             else if(events[i].events & EPOLLIN) {
                 if(events[i].data.fd < ) {
                     continue;
                 }
                 readNum = handleRead(events[i].data.fd);
                 if(readNum == READ_ERROR) {
                     ERR_EXIT("handleRead");
                 } else if(readNum == READ_CLOSE) {
                     event = events[i];
                     if(epoll_ctl(epollFd, EPOLL_CTL_DEL, event.data.fd, &event) < ) {
                         ERR_EXIT("epoll_ctl");
                     }
                     epollNum--;
                     printf("client closed, remove %d\n", events[i].data.fd);
                     close(events[i].data.fd);
                 }
             }
         }
     }
 }

1. struct epoll_event events[EPOLL_SIZE];用于返回发生了哪些事件。

2. struct epoll_event event; 是一个临时变量，用于将我们想要监视的描述符通过 epoll_ctl 添加到集合中去。

3. epollNum 表示当前监视的描述符的个数。

4. epollRet 大于0时，表示有多少个文件描述符发生相关事件。 等于0时，表示超时。

5. accept时，需要将连接套接字通过epoll_ctl 添加到集合中去。当read收到FIN时，需要将连接套接字通过epoll_ctl 从集合中删去，并close此套接字。