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 < 0) {
        ERR_EXIT("epoll_create1");
    }

    event.data.fd = listenFd;
    event.events = EPOLLIN|EPOLLET;
    if(epoll_ctl(epollFd, EPOLL_CTL_ADD, listenFd, &event) < 0) {
        ERR_EXIT("epoll_ctl");
    }
    
    int epollRet;
    int i;
    struct sockaddr_in cliAddr;
    socklen_t len;
    int acceptFd;
    int epollNum = 1;
    int readNum;
    while(1) {
        epollRet = epoll_wait(epollFd, events, epollNum, -1);
        if(epollRet < 0) {
            ERR_EXIT("epollRet");
        } else if(epollRet == 0) {
            continue;
        }

        for(i = 0; i < epollRet; i++) {
            if(events[i].data.fd == listenFd) {
                memset(&cliAddr, 0, sizeof(cliAddr));
                len = sizeof(cliAddr);
                if((acceptFd = accept(listenFd, (struct sockaddr *)&cliAddr, &len)) < 0) {
                    ERR_EXIT("accept");
                }
                printf("recv a connect from %s, port %d, fd %d
", 
                    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) < 0) {
                    ERR_EXIT("epoll_ctl");
                }
            } 
            else if(events[i].events & EPOLLIN) {
                if(events[i].data.fd < 0) {
                    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) < 0) { 
                        ERR_EXIT("epoll_ctl");
                    }
                    epollNum--;
                    printf("client closed, remove %d
", 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。