9_3.cpp

// LT 和 ET 模式
#include<sys/types.h>
#include<sys/socket.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<stdlib.h>
#include<sys/epoll.h>
#include<pthread.h>

#define MAX_EVENT_NUMBER 1024
#define BUFFER_SIZE 10


// 将文件描述符设置为非阻塞的
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_addrlength = sizeof(client_address);
            int connfd = accept(listenfd, (struct sockaddr*)&client_address, &client_addrlength);
            addfd(epollfd, connfd, false); // 对connfd禁用ET模式
        }
        else if(events[i].events & EPOLLIN){
            // 只要socket读缓存中还有未读出的数据，这段代码就被触发
            printf("event trigger once\n");
            memset(buf, '\0', BUFFER_SIZE);
            int ret = recv(sockfd, buf, BUFFER_SIZE-1, 0);
            if(ret <= 0){ close(sockfd); continue; }
            printf("get %d bytes of content: %s\n", ret, buf);
        }
        else{
            printf("something else happened\n");
        }
    }
}


// ET模式工作流程
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);
        }
        else if(events[i].events & EPOLLIN){
            // 这段代码不会被重复触发，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
            printf("event trigger once\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，下面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)){
                        printf("read later\n");
                        break;
                    }
                    close(sockfd);
                    break;
                }
                else if(ret == 0){ close(sockfd); }
                else{ printf("get %d bytes of content: %s\n", ret, buf); }
            }

        }
        else{ printf("something else happened\n"); }
    }
}


int main(int argc, char* argv[]){
    if(argc <= 2){
        printf("usage: %s IP PORT\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){
            printf("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;
}