libevent简单实现

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对epoll进行的封装

epoll(7)

还记得前段时间去百度面试，被问道select、poll、epoll的区别，机械式的把书本上看到的内容复述了一遍。

面试官：谈谈你自己的理解。

一时语塞，说道，epoll写代码难度有点大。面试官点了点头目测很认可。

这就与epoll的结构体有关了，比如它的void*指针可以只想用户结构体，用户结构提又可以封装一系列内容例如fd、回调等等。

man 2 epola_wait 看看它的结构体里面到底有什么。

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

Reactor

Reactor是一个设计模式，它包含了几个部分：

Handle句柄：用来标志描述符
Demultiplexer：事件分发器，即select/poll/epoll
Event Handler : 事件处理接口
Reactor：用来注册删除事件句柄，运行事件循环，就绪事件时，分发事件到回调函数上处理

这里写图片描述

libevent简单实现

#include    <stdlib.h>#include    <stdio.h>   #include    <stdio.h>#include    <sys/socket.h>#include    <sys/epoll.h>#include    <arpa/inet.h>#include    <fcntl.h>#include    <unistd.h>#include    <errno.h>#include    <string.h>#include    <time.h>#define MAX_EVENTS      1024#define BUFLEN  128#define SERV_PORT           8080/* *  status:1表示在监听事件中,0表示不在   *  last_active:记录最后一次响应时间,做超时处理 */struct  myevent_s   {    int fd; //cfd   listenfd    int events; //EPOLLIN       EPLLOUT    void    *arg;   //指向自己结构体指针    void    (*call_back)(int    fd, int events, void    *arg);    int status;    char    buf[BUFLEN];    int len;    long    last_active;};int g_efd;  /*  epoll_create返回的句柄   */struct  myevent_s g_events[MAX_EVENTS+1];   /*+1最后一个用于listenfd*/void    eventset(struct myevent_s *ev,  int fd, void (*call_back)(int,int,void  *),void *arg){    ev->fd  =   fd;    ev->call_back   =   call_back;    ev->events  =   0;    ev->arg =   arg;    ev->status  =   0;    //memset(ev->buf,   0,  sizeof(ev->buf));    //ev->len   =   0;    ev->last_active =   time(NULL);    return;}void    eventset(struct myevent_s *ev,int fd, void (*call_back)(int,int,void*), void*arg){    ev->fd  =   fd;    ev->call_back   =   call_back;    ev->events  =   0;    ev->arg =   arg;    ev->status  =   0;    //memset(ev->buf,   0,  sizeof(ev->buf));    //ev->len   =   0;    ev->last_active =   time(NULL);    return;}void    recvdata(int    fd, int events, void    *arg);void    senddata(int    fd, int events, void    *arg);void    eventadd(int efd,   int events, struct  myevent_s   *ev){    struct epoll_event epv ={0, {0}};    int op;    epv.data.ptr = ev;    epv.events= ev->events=events;    if  (ev->status == 1)    {    op = EPOLL_CTL_MOD;    }       else        {    op = EPOLL_CTL_ADD;    ev->status = 1;    }    if  (epoll_ctl(efd, op, ev->fd, &epv) < 0)    printf("event add failed    [fd=%d],events[%d]\n",  ev->fd, events);    else    printf("event add   OK  [fd=%d],    op=%d,  events[%0X]\n", ev->fd, op,events);    return;}void eventdel(int efd,  struct  myevent_s *ev){    struct epoll_event  epv = {0,   {0}};    if  (ev->status !=1)    return;    epv.data.ptr = ev;    ev->status  = 0;    epoll_ctl(efd, EPOLL_CTL_DEL, ev->fd, &epv);    return;}void acceptconn(int lfd,int events,void *arg){    struct sockaddr_in cin;    socklen_t len = sizeof(cin);    int cfd,    i;    if  ((cfd =accept(lfd, (struct sockaddr *)&cin, &len)) == -1)    {    if (errno != EAGAIN && errno != EINTR)    {        /*  暂时不做出错处理    */    }    printf("%s:accept,  %s\n",  __func__,strerror(errno));    return;    }    do      {    for(i=0;i<MAX_EVENTS;i++)    {        if  (g_events[i].status==0)        break;    }    if(i==MAX_EVENTS)       {        printf("%s: max connect limit[%d]\n",__func__,MAX_EVENTS);        break;    }    int flag=0;    if((flag=fcntl(cfd,F_SETFL,O_NONBLOCK)) <0)    {        printf("%s: fcntl   nonblocking failed, %s\n",  __func__,strerror(errno));        break;    }    eventset(&g_events[i],cfd,recvdata,&g_events[i]);    eventadd(g_efd, EPOLLIN,&g_events[i]);    }while(0);    printf("new connect [%s:%d][time:%ld],pos[%d]\n",inet_ntoa (cin.sin_addr),ntohs(cin.sin_port),g_events[i].last_active,i);    return;}void    recvdata(int fd,int events, void*arg){    struct myevent_s *ev=(struct myevent_s*)arg;    int len;    len =recv(fd,ev->buf,sizeof(ev->buf),0);    eventdel(g_efd,ev);    if  (len>0)     {    ev->len =len;    ev->buf[len]='\0';    printf("C[%d]:%s\n",fd, ev->buf);    /*  转换为发送事件 */    eventset(ev,fd,senddata,ev);    eventadd(g_efd,EPOLLOUT,ev);    }    else if(len==0)    {    close(ev->fd);    /*ev-g_events地址相减得到偏移元素位置   */    printf("[fd=%d] pos[%d],closed\n",fd,(int)(ev-g_events));    }    else    {    close(ev->fd);    printf("recv[fd=%d] error[%d]:%s\n",fd,errno,strerror(errno));    }    return;}void senddata(int fd,int events,void *arg){    struct myevent_s *ev=(struct myevent_s*)arg;    int len;    len=send(fd,ev->buf,ev->len,0);    //printf("fd=%d\tev->buf=%s\ttev->len=%d\n",    fd, ev->buf,    ev->len);    //printf("send  len =   %d\n",  len);    eventdel(g_efd,ev);    if  (len>0)    {    printf("send[fd=%d],[%d]%s\n",fd,len,ev->buf);    eventset(ev,fd,recvdata,ev);    eventadd(g_efd, EPOLLIN,ev);    }    else        {    close(ev->fd);    printf("send[fd=%d] error   %s\n",fd,strerror(errno));    }    return;}void initlistensocket(int efd,short port){    int lfd=socket(AF_INET,SOCK_STREAM,0);    fcntl(lfd,F_SETFL,O_NONBLOCK);    eventset(&g_events[MAX_EVENTS],lfd,acceptconn,&g_events[MAX_EVENTS]);    eventadd(efd,EPOLLIN,&g_events[MAX_EVENTS]);    struct sockaddr_in sin;    memset(&sin,0,sizeof(sin));    sin.sin_family=AF_INET;    sin.sin_addr.s_addr=INADDR_ANY;    sin.sin_port=htons(port);    bind(lfd,(struct sockaddr*)&sin,sizeof(sin));    listen(lfd,20);    return;}int main(int argc,char*argv[]){    unsigned short port =SERV_PORT;    if  (argc==2)    port=atoi(argv[1]);    g_efd=epoll_create(MAX_EVENTS+1);    if  (g_efd<=0)    printf("create efd in   %s  err %s\n",  __func__,strerror(errno));    initlistensocket(g_efd,port);    /*  事件循环    */    struct epoll_event events[MAX_EVENTS+1];    printf("server  running:port[%d]\n",    port);    int checkpos=0,i;    while(1){    /*  超时验证,每次测试100个链接,不测试listenfd 当客户端60秒内没        有和服务器通信,则关闭此客户端链接   */    long now=time(NULL);    for(i=0;i<100;i++,checkpos++)     {        if(checkpos ==MAX_EVENTS)        checkpos=0;        if  (g_events[checkpos].status!=1)        continue;        long duration=now-g_events[checkpos].last_active;        if  (duration>=60)        {        close(g_events[checkpos].fd);        printf("[fd=%d] timeout\n",g_events[checkpos].fd);        eventdel(g_efd, &g_events[checkpos]);        }    }    /*  等待事件发生  */    int nfd =epoll_wait(g_efd,events,MAX_EVENTS+1,1000);    if(nfd<0)       {        printf("epoll_wait  error,  exit\n");        break;    }    for(i=0;i<nfd;i++)    {        struct myevent_s*ev =(struct myevent_s*)events[i].data.ptr;        if  ((events[i].events&EPOLLIN)&&(ev->events&EPOLLIN))        {        ev->call_back(ev->fd,events[i].events,ev->arg);        }        if  ((events[i].events&EPOLLOUT)&&(ev->events&EPOLLOUT))        {        ev->call_back(ev->fd,events[i].events,ev->arg);        }    }    }    /*退出前释放所有资源*/    return 0;}

参考

深入浅出 Libevent 作者：刘丹冰
https://segmentfault.com/a/1190000002715832 （Reactor 和 Proactor）
Linux man page

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