9-3-epoll-ltandet.c

#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <sys/epoll.h>
#include <pthread.h>
#include <stdlib.h>

#define  MAX_EVENT_NUMBER   1024
#define  BUFFER_SIZE        10

/*将文件描述符设置成非阻塞的 */
int setnonblocking(int fd)
{
    int old_option = fcntl(fd, F_GETFL);
    int new_option = old_option | O_NONBLOCK;
    fcntl(fd, F_SETFL, new_option);
    return old_option;
}

/* 将文件描述符fd上的EPOLLIN注册到epollfd指示的epoll内核事件表中，参数enable_et
 * 指定是否对fd启用ET模式
 * */
void addfd(int epollfd, int fd, bool enable_et)
{
    epoll_event event;
    event.data.fd = fd;
    event.events = EPOLLIN;
    if (enable_et) 
    {
        event.events |= EPOLLET;
    }

    epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
    setnonblocking(fd);
}


/*LT模式的工作流程 */
void lt(epoll_event *events, int number, int epollfd, int listenfd)
{
    char buf[BUFFER_SIZE];
    for(int i = 0; i < number; i++) 
    {
        int sockfd = events[i].data.fd;
        if (sockfd == listenfd) 
        {
            struct sockaddr_in client_address;
            socklen_t client_addresslength = sizeof(client_address);
            int connfd = accept(listenfd, (struct sockaddr *)&client_address, &client_addresslength);
            addfd(epollfd, connfd, false); //对connfd 禁用ET模式
        }
        else if (events[i].events & EPOLLIN) 
        {
            fprintf(stdout, "event trigger once, EPOLLIN \n");
            memset(buf, '\0', BUFFER_SIZE);
            int ret = recv(sockfd, buf, BUFFER_SIZE - 1, 0);
            if (ret <= 0) 
            {
                close(sockfd);
                continue;
            }
            fprintf(stdout, "get %d bytes of content: %s\n", ret, buf);
        }
        else
        {
            fprintf(stdout, "somethine else happened\n");
        }
    }
}

/*ET模式的工作流程*/
void et(epoll_event *events, int number, int epollfd, int listenfd)
{
    char buf[BUFFER_SIZE];
    for(int i = 0; i < number; i++) 
    {
        int sockfd = events[i].data.fd;
        if (sockfd == listenfd) 
        {
            struct sockaddr_in client_address;
            socklen_t client_addrlength = sizeof(client_address);
            int connfd = accept(listenfd, (struct sockaddr *)&client_address, &client_addrlength);
            addfd(epollfd, connfd, true); /*connfd 开启ET 模式*/
        }
        else if (events[i].events & EPOLLIN) 
        {
            /*这段代码不会重复触发，所以我们循环读取数据，
             * 以确保把socket读缓存中的所有数据读出
             */
            fprintf(stdout, "event trigger once: EPOLLIN\n");
            while(1)
            {
                memset(buf, '\0', BUFFER_SIZE);
                int ret = recv(sockfd, buf, BUFFER_SIZE - 1, 0);
                if(ret < 0)
                {
                    /*对于非阻塞IO，下的条件成立表示数据已经全部读取完毕。此后，
                     * epoll就能再次触发sockfd上的EPOLLIN事件，以驱动下一次读操作
                     */
                    if ((errno == EAGAIN) || (errno == EWOULDBLOCK) ) 
                    {
                        fprintf(stdout, "read later\n");
                        break;
                    }
                    close(sockfd);
                    break;
                }
                else if (ret == 0) 
                {
                    close(sockfd);
                }
                else
                {
                    fprintf(stdout, "got %d bytes of content: %s\n", ret, buf);
                }
            }
        }
        else
        {
            fprintf(stdout, "something else happened\n");
        }
    }
}

int main(int argc, const char *argv[])
{
    if (argc <= 2) 
    {
        fprintf(stderr, "usage: %s ip_address port_number\n", basename(argv[0]));
        return 1;
    }
    const char *ip = argv[1];
    int port       = atoi(argv[2]);

    int ret = 0;
    struct sockaddr_in address;
    bzero(&address, sizeof(address));
    address.sin_family = AF_INET;
    inet_pton(AF_INET, ip, &address.sin_addr);
    address.sin_port = htons(port);

    int listenfd = socket(PF_INET, SOCK_STREAM, 0);
    assert(listenfd > 0);

    ret = bind(listenfd, (struct sockaddr *)&address, sizeof(address));
    assert(ret != -1);

    ret = listen(listenfd, 5);
    assert(ret != -1);

    epoll_event events[MAX_EVENT_NUMBER];
    int epollfd = epoll_create(5);
    assert(epollfd != -1);
    addfd(epollfd, listenfd, true);

    while(1)
    {
        int ret = epoll_wait(epollfd, events, MAX_EVENT_NUMBER, -1);
        
        if (ret < 0) 
        {
            fprintf(stderr, "epoll failure\n");
            break;
        }

        lt(events, ret, epollfd, listenfd);  /*使用LT 模式*/
        //et(events, ret, epollfd, listenfd);  /*使用ET模式 */
    }

    close(listenfd);
    return 0;
}