I/O多路转接之epoll模型

雨点打透心脏的1/2处 2022-06-11 07:20 142阅读 0赞

epoll是性能最好的没有之一  
epoll有三个系统调用函数  
epoll\_create 创建文件描述符、来标识epoll模型  
epoll\_ctl  
epoll\_wait  
![这里写图片描述][SouthEast]

#include<stdio.h>
    #include <sys/epoll.h>
    #include <sys/types.h>
    #include <sys/socket.h>
    #include <sys/time.h>
    #include <sys/types.h>
    #include <unistd.h>
    #include<arpa/inet.h>
    #include<netinet/in.h>
    #include<string.h>
    #include<unistd.h>
    #include<stdlib.h>
    #define SIZE 64
    static void Usage(char*proc)
    {
        printf("%s [local_ip] [local_port]\n",proc);
    }
    int startUp(char*ip,int port)
    {
       int sock=socket(AF_INET,SOCK_STREAM,0);
        if(sock<0)
        {
            perror("socket");
            exit(2);
        }
        int opt=1;
        setsockopt(sock,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(opt));
        struct sockaddr_in server;
        server.sin_family=AF_INET;
        server.sin_port=htons(atoi(port));
        server.sin_addr.s_addr=inet_addr(ip);
        if(bind(sock,(struct sockaddr*)&server,sizeof(struct sockaddr_in))<0)
        {
            perror("bind");
            exit(3);
        }
        if(listen(sock,10)<0)
        {
            perror("listen");
            exit(4);
        }
        return sock;
    }
    int main(int argv,char*argc[])
    {
        if(argv!=3)
        {
            Usage(argc[0]);
            return 1;
        }
        int listen_sock=startUp(argc[1],argc[2]);
        int epfd= epoll_create(256);
        if(epfd<0)
        {
           perror("epoll_create");
           return 5;
        }
        struct epoll_event ev;
        ev.events=EPOLLIN;
        ev.data.fd=listen_sock;
        epoll_ctl(epfd,EPOLL_CTL_ADD,listen_sock,&ev);
        struct epoll_event revs[64];  
        int nums=-1;
        int timeout=5000;
        while(1)
        {
            switch((nums=epoll_wait(epfd,revs,SIZE,timeout)))
            {
               case -1:
                   perror("epoll_wait");
                   return 6;
               case 0:
                   printf("timeout\n");
                   break;
                default:
                   {
                   int i=0;
                   for(i=0;i<nums;i++)
                   {
                       printf("nums %d\n",nums);
                       int fd=revs[i].data.fd;
                       if(fd==listen_sock&&revs[i].events&EPOLLIN)
                       {
                              struct sockaddr_in client;
                              socklen_t len=sizeof(client);
                              int newsock=accept(listen_sock,(struct sockaddr*)&client,&len);
                              if(newsock<0)
                              {
                                  perror("accept");
                                  continue;
                              }
                              printf("get a client [%s] [%d]\n",inet_ntoa(client.sin_addr),ntohs(client.sin_port));
                              ev.events=EPOLLIN;
                              ev.data.fd=newsock;
                              epoll_ctl(epfd,EPOLL_CTL_ADD,newsock,&ev);
                       }
                    else if(fd!=listen_sock)
                       {
                           printf("hahah\n");
                           if(revs[i].events&EPOLLIN)
                           {
                              char buf[1024];
                              ssize_t s=read(fd,buf,sizeof(buf)-1);
                              if(s>0)
                              {
                                  buf[s]=0;
                                  printf("client say:%s\n",buf);
                                  ev.events=EPOLLOUT;
                                  ev.data.fd=fd;
                                  epoll_ctl(epfd, EPOLL_CTL_MOD,fd,&ev);
                              }
                              else if(s==0)
                              {
                                  printf("client is quit\n");
                                  close(fd);
                                  epoll_ctl(epfd,EPOLL_CTL_DEL,fd,&ev);
                              }
                              else
                              {
                                  perror("read");
                                  close(fd);
                                  epoll_ctl(epfd,EPOLL_CTL_DEL,fd,&ev);                       }
                           }
                           else if(revs[i].events&EPOLLOUT)
                           {
                                 const char* msg = "HTTP/1.1 200 OK\r\n\r\n<html><h1>Hello epoll!</h1></html>";
                                  write(fd,msg,strlen(msg));
                                  close(fd);
                                  epoll_ctl(epfd,EPOLL_CTL_DEL,fd,&ev);
    
                           }
                           else
                           {
    
                           }
                       }
                       else
                       {
    
                       }
                   }
                   }
                 break;
            }
    
        }
        return 0;
    }

epolls是一种高性能服务器。  
1、他底层的红黑树能够高效的进行增删改查  
2、采用回调机制不需要轮询  
3、一旦关心的文件描述符上对应的事件发生就激活放入就绪队列  
4、上层直接从就绪队列中取  
5、就绪队列连续并且返回值是实际就绪的个数，这样即使需要遍历也会遍历的都是有效的  
6、采用内存映射机制，少了数据的拷贝。

[SouthEast]: /images/20220611/f717babe7d6a4a2da67aface227a1fab.png