多路复用I/O模型poll() 模型 代码实现

多路复用I/O模型poll() 模型 代码实现

poll()机制和select()机制是相似的，都是对多个描述符进行轮询的方式。

不同的是poll()没有描述符数目的限制。

是通过struct pollfd结构体，对每个描述符进行轮询的

struct pollfd fdarray

{

　　int fd;    /*文件描述符*/

　　short events; /*表示等待的事件*/

　　short revents;/*表示返回事件即实际发生的事件*/

};

data.h

#ifndef DATA_H
#define DATA_H
#include <string.h>
#include <stdio.h>
#include <poll.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <errno.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <arpa/inet.h>
#include <assert.h>
#include <unistd.h>
#define maxn 1100
#define MAXLINE 10
#define LISTEN 10
#define IP "127.0.0.1"
#define PORT 4578
#define BACKLOG 5
#define INFTIM -1
#endif

server.c

  1 #include "data.h"
  2 static void deal_message(struct pollfd *fd_array,int num);
  3 static void poll_accept(int sockfd);
  4
  5 static int init()
  6 {
  7     struct sockaddr_in server_in;
  8     int sockfd;
  9     if((sockfd = socket(AF_INET,SOCK_STREAM,0)) == -1)
 10     {
 11         fprintf(stderr,"socket fail,error :%s\n",strerror(errno));
 12         return -1;
 13     }
 14     bzero(&server_in,sizeof(server_in));
 15     server_in.sin_family = AF_INET;
 16     server_in.sin_port = htons(PORT);
 17     inet_pton(AF_INET,IP,&server_in.sin_addr);
 18     if(bind(sockfd,(struct sockaddr*)&server_in,sizeof(struct sockaddr)) == -1)
 19     {
 20         fprintf(stderr,"bind fail,error:%s\n",strerror(errno));
 21         return -1;
 22     }
 23     listen(sockfd,BACKLOG);
 24     return sockfd;
 25 }
 26
 27 static void poll_accept(int sockfd)
 28 {
 29     struct pollfd fd_array[maxn];
 30     int afd;
 31     int pollfd;
 32     struct sockaddr_in client_in;
 33     bzero(&client_in,sizeof(client_in));
 34     int i = 0;
 35     fd_array[0].fd = sockfd;
 36     fd_array[0].events = POLLIN;
 37     for(i=0;i<maxn;i++)
 38     {
 39         fd_array[i].fd = -1;
 40     }
 41     int num = 0;
 42     int len = sizeof(client_in);
 43     while(1)
 44     {
 45
 46         pollfd = poll(fd_array,num+1,INFTIM);
 47         if(pollfd == -1)
 48         {
 49             fprintf(stderr,"poll fail,error %s\n",strerror(errno));
 50             return;
 51         }
 52         if(pollfd == 0)
 53         {
 54             continue;
 55         }
 56         if(fd_array[0].revents & POLLOUT)
 57         {
 58             if((afd = accept(sockfd,(struct sockaddr*)&client_in,&len)) == -1)
 59             {
 60                 fprintf(stderr,"accept fail,error:%s\n",strerror(errno));
 61                 return ;
 62             }
 63         }
 64         i = 0;
 65         for(i =0;i<maxn;i++)
 66         {
 67             if(fd_array[i].fd < 0)
 68             {
 69                 fd_array[i].fd = afd;
 70                 break;
 71             }
 72         }
 73         if(i == maxn)
 74         {
 75             printf("too many to server!\n");
 76             return ;
 77         }
 78         fd_array[i].events = POLLIN;
 79         if(i > num )
 80             num = i;
 81         if(--pollfd <= 0)
 82             continue;
 83     }
 84     deal_message(fd_array,num);
 85 }
 86
 87 static void deal_message(struct pollfd *fd_array,int num)
 88 {
 89     int i,n;
 90     char buf[maxn];
 91     memset(buf,‘\0‘,sizeof(buf));
 92     for(i=1;i<=num;i++)
 93     {
 94         if(fd_array[i].fd < 0)
 95             continue;
 96         if(fd_array[i].revents&POLLIN)
 97         {
 98             n = read(fd_array[i].fd,buf,maxn);
 99             if(n == 0)
100             {
101                 close(fd_array[i].fd);
102                 fd_array[i].fd = -1;
103                 continue;
104             }
105             write(STDOUT_FILENO,buf,n);
106             write(fd_array[i].fd,buf,n);
107         }
108     }
109 }
110 int main()
111 {
112     int sockfd = init();
113     poll_accept(sockfd);
114     close(sockfd);
115     return 0;
116 }