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  • IO多路复用之epoll(二)

    前一篇介绍了epoll的LT模式,LT模式注意epollout事件在数据全部写成功后需要取消关注,

    或者更改为EPOLLIN。

    而这次epoll的ET模式,要注意的是在读和写的过程中要在循环中写完或者读完所有数据,

    确保不要丢掉一些数据。

    因为epoll ET模式只在两种边缘更改的时候触发,对于读事件只在内核缓冲区由空变为

    非空通知一次用户,对于写事件,内核缓冲区只在由满变为非满的情况通知用户一次。

    下面是代码

    int main()
    {

    int eventsize = 20;
    struct epoll_event * epoll_eventsList = (struct epoll_event *)malloc(sizeof(struct epoll_event)

    *eventsize);

    //打开一个空的描述符
    int idlefd = open("/dev/null",O_RDONLY|O_CLOEXEC);
    cout << "idlefd" <<idlefd <<endl;
    //生成listen描述符

    int listenfd = socket(PF_INET, SOCK_CLOEXEC | SOCK_STREAM | SOCK_NONBLOCK, IPPROTO_TCP);
    if(listenfd < 0)
    {
    ERR_EXIT("socketfd");
    }

    //初始化地址信息
    struct sockaddr_in servaddr;
    memset(&servaddr,0 ,sizeof(struct sockaddr_in));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(6667);
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);


    int on = 1;
    if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
    ERR_EXIT("setsockopt");

    if(bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)))
    ERR_EXIT("bindError");

    if (listen(listenfd, SOMAXCONN) < 0)
    ERR_EXIT("listen");

    //记录客户端连接对应的socket
    std::vector<int> clients;
    //创建epollfd, 用于管理epoll事件表
    int epollfd;
    epollfd = epoll_create1(EPOLL_CLOEXEC);

    struct epoll_event event;
    event.data.fd = listenfd;
    event.events = EPOLLIN|EPOLLET;
    //将listenfd加入到epollfd管理的表里
    epoll_ctl(epollfd, EPOLL_CTL_ADD, listenfd, &event);

    //用于接收新连接的客户端地址
    struct sockaddr_in peeraddr;
    socklen_t peerlen;
    int connfd;
    //为了简单起见写了个很大的数组,根据文件描述符存储内容
    //其实很多项目代码采epoll.data.ptr回调具体的读写

    vector<string> recievebuf;

    for(int i = 0 ; i < 22222; i++)
    {
    recievebuf.push_back("");
    }

    while(1)
    {
    int nready = epoll_wait(epollfd, epoll_eventsList, eventsize, -1);
    if (nready == -1)
    {
    if (errno == EINTR)
    continue;

    ERR_EXIT("epoll_wait");
    }
    if (nready == 0)
    continue;

    //大小不够重新开辟

    if ((size_t)nready == eventsize)
    {
    if(eventsize * 2 >= 22222)
    {
    ERR_EXIT("too many fds");
    }

    struct epoll_event * epoll_eventsList2 = (struct epoll_event *)malloc(sizeof(struct epoll_event) * 
    eventsize *2);
    if(epoll_eventsList2)
    {
    memcpy(epoll_eventsList2,epoll_eventsList,sizeof(struct epoll_event) * eventsize);
    eventsize = eventsize * 2;
    free(epoll_eventsList);
    epoll_eventsList = epoll_eventsList2;

    }


    }


    for (int i = 0; i < nready; ++i)
    {
    //判断wait返回的events数组状态是否正常
    if ((epoll_eventsList[i].events & EPOLLERR) ||
    (epoll_eventsList[i].events & EPOLLHUP))
    {
    fprintf (stderr, "epoll error ");
    close (epoll_eventsList[i].data.fd);
    continue;

    }

    if (epoll_eventsList[i].data.fd == listenfd)
    {
    peerlen = sizeof(peeraddr);
    //ET模式accept放在while循环里

    do
    {
    connfd = ::accept4(listenfd, (struct sockaddr*)&peeraddr,
    &peerlen, SOCK_NONBLOCK | SOCK_CLOEXEC);

    if(connfd <= 0)
    break;

    std::cout<<"ip="<<inet_ntoa(peeraddr.sin_addr)<<
    " port="<<ntohs(peeraddr.sin_port)<<std::endl;
    clients.push_back(connfd);

    //将connd加入epoll表里,关注读事件

    event.data.fd = connfd;
    event.events = EPOLLIN |EPOLLET;
    epoll_ctl(epollfd, EPOLL_CTL_ADD, connfd, &event);
    cout << "loop" <<endl;
    cout << "loop" << connfd << endl;
    }while(1);
    //accept失败,判断是否接收全所有的fd
    cout << connfd << endl;
    if (connfd == -1){
    if (errno != EAGAIN && errno != ECONNABORTED
    && errno != EPROTO && errno != EINTR)
    {
    cout << "error" <<endl;
    ERR_EXIT("accept");
    }

    }

    //所有请求都处理完成
    cout << "continue"<<endl;
    continue;

    }//endif
    else if(epoll_eventsList[i].events & EPOLLIN)
    {
    connfd = epoll_eventsList[i].data.fd;
    if(connfd > 22222)
    {
    close(connfd);
    event = epoll_eventsList[i];
    epoll_ctl(epollfd, EPOLL_CTL_DEL, connfd, &event);
    clients.erase(std::remove(clients.begin(), clients.end(), connfd), clients.end());
    continue;

    }

    char buf[1024] = {0};
    if(connfd < 0)
    continue;
    int ret = 0;
    int total = 0;
    std::string strtemp;
    while(1)
    {
    cout << "begin read" <<endl;
    ret = read(connfd, buf, 1024);
    if(ret <= 0)
    {
    break;
    }

    strtemp += string(buf);
    total += ret;
    memset(buf, 0, 1024);

    if(ret < 1024)
    {
    break;
    }

    }//endwhile(1)

    cout << "end read" <<endl;
    recievebuf[connfd] = strtemp.c_str();
    cout << "buff data :" << recievebuf[connfd]<<endl; 
    if(ret == -1)
    {
    if((errno == EAGAIN) ||
    (errno == EWOULDBLOCK))
    {
    //由于内核缓冲区空了,下次有数据到来是会触发epollin
    continue;
    }


    ERR_EXIT("read");

    }//endif ret == -1

    //连接断开
    if(ret == 0)
    {
    std::cout<<"client close"<<std::endl;
    close(connfd);
    event = epoll_eventsList[i];
    epoll_ctl(epollfd, EPOLL_CTL_DEL, connfd, &event);
    clients.erase(std::remove(clients.begin(), clients.end(), connfd), clients.end());
    continue;

    }

    cout << "turn to write" << endl;
    //更改为写模式

    event.data.fd = connfd;
    event.events = EPOLLOUT | EPOLLET;

    epoll_ctl(epollfd, EPOLL_CTL_MOD, connfd, &event);
    cout << "epoll mod change success" << endl;

    }//end elif

    else //写事件
    {

    if(epoll_eventsList[i].events & EPOLLOUT)
    {
    cout << "begin write" <<endl;
    connfd = epoll_eventsList[i].data.fd;
    int count = 0;
    int totalsend = 0;
    char buf[1024];
    strcpy(buf, recievebuf[connfd].c_str());

    cout << "write buff" <<buf<<endl;
    while(1)
    {
    int totalcount = strlen(buf);
    int pos = 0;
    count = write(epoll_eventsList[i].data.fd, buf + pos, totalcount);
    cout << "write count:" << count;
    if(count < 0)
    {
    break;
    }

    if(count < totalcount)
    {
    totalcount = totalcount - count;
    pos += count;

    }
    else
    {
    break;

    }

    }//end while


    if(count == -1)
    {
    if((errno == EAGAIN) ||
    (errno == EWOULDBLOCK))
    {
    //由于内核缓冲区满了
    //于内核缓冲区满了
    continue;
    }

    ERR_EXIT("write");
    }

    if(count == 0)
    {
    std::cout<<"client close"<<std::endl;
    close(connfd);
    event = epoll_eventsList[i];
    epoll_ctl(epollfd, EPOLL_CTL_DEL, connfd, &event);
    clients.erase(std::remove(clients.begin(), clients.end(), connfd), 
    clients.end());
    continue;

    }

    event.data.fd = connfd;
    event.events = EPOLLIN|EPOLLET;
    epoll_ctl(epollfd, EPOLL_CTL_MOD, connfd, &event);

    }

    }//end eles 写事件


    }

    }

    }

    源代码下载地址:http://download.csdn.net/detail/secondtonone1/9486222

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  • 原文地址:https://www.cnblogs.com/xumaojun/p/8526512.html
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