IO多路复用之epoll全面总结(必看篇)

客户端也用epoll实现，控制STDIN_FILENO、STDOUT_FILENO、和sockfd三个描述符，程序如下所示：

#include <netinet/in.h>
#include <sys/socket.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <time.h>
#include <unistd.h>
#include <sys/types.h>
#include <arpa/inet.h>

#define MAXSIZE   1024
#define IPADDRESS  "127.0.0.1"
#define SERV_PORT  8787
#define FDSIZE    1024
#define EPOLLEVENTS 20

static void handle_connection(int sockfd);
static void
handle_events(int epollfd,struct epoll_event *events,int num,int sockfd,char *buf);
static void do_read(int epollfd,int fd,int sockfd,char *buf);
static void do_read(int epollfd,int fd,int sockfd,char *buf);
static void do_write(int epollfd,int fd,int sockfd,char *buf);
static void add_event(int epollfd,int fd,int state);
static void delete_event(int epollfd,int fd,int state);
static void modify_event(int epollfd,int fd,int state);

int main(int argc,char *argv[])
{
  int         sockfd;
  struct sockaddr_in servaddr;
  sockfd = socket(AF_INET,SOCK_STREAM,0);
  bzero(&servaddr,sizeof(servaddr));
  servaddr.sin_family = AF_INET;
  servaddr.sin_port = htons(SERV_PORT);
  inet_pton(AF_INET,IPADDRESS,&servaddr.sin_addr);
  connect(sockfd,(struct sockaddr*)&servaddr,sizeof(servaddr));
  //处理连接
  handle_connection(sockfd);
  close(sockfd);
  return 0;
}


static void handle_connection(int sockfd)
{
  int epollfd;
  struct epoll_event events[EPOLLEVENTS];
  char buf[MAXSIZE];
  int ret;
  epollfd = epoll_create(FDSIZE);
  add_event(epollfd,STDIN_FILENO,EPOLLIN);
  for ( ; ; )
  {
    ret = epoll_wait(epollfd,events,EPOLLEVENTS,-1);
    handle_events(epollfd,events,ret,sockfd,buf);
  }
  close(epollfd);
}

static void
handle_events(int epollfd,struct epoll_event *events,int num,int sockfd,char *buf)
{
  int fd;
  int i;
  for (i = 0;i < num;i++)
  {
    fd = events[i].data.fd;
    if (events[i].events & EPOLLIN)
      do_read(epollfd,fd,sockfd,buf);
    else if (events[i].events & EPOLLOUT)
      do_write(epollfd,fd,sockfd,buf);
  }
}

static void do_read(int epollfd,int fd,int sockfd,char *buf)
{
  int nread;
  nread = read(fd,buf,MAXSIZE);
    if (nread == -1)
  {
    perror("read error:");
    close(fd);
  }
  else if (nread == 0)
  {
    fprintf(stderr,"server close.n");
    close(fd);
  }
  else
  {
    if (fd == STDIN_FILENO)
      add_event(epollfd,sockfd,EPOLLOUT);
    else
    {
      delete_event(epollfd,sockfd,EPOLLIN);
      add_event(epollfd,STDOUT_FILENO,EPOLLOUT);
    }
  }
}

static void do_write(int epollfd,int fd,int sockfd,char *buf)
{
  int nwrite;
  nwrite = write(fd,buf,strlen(buf));
  if (nwrite == -1)
  {
    perror("write error:");
    close(fd);
  }
  else
  {
    if (fd == STDOUT_FILENO)
      delete_event(epollfd,fd,EPOLLOUT);
    else
      modify_event(epollfd,fd,EPOLLIN);
  }
  memset(buf,0,MAXSIZE);
}

static void add_event(int epollfd,int fd,int state)
{
  struct epoll_event ev;
  ev.events = state;
  ev.data.fd = fd;
  epoll_ctl(epollfd,EPOLL_CTL_ADD,fd,&ev);
}

static void delete_event(int epollfd,int fd,int state)
{
  struct epoll_event ev;
  ev.events = state;
  ev.data.fd = fd;
  epoll_ctl(epollfd,EPOLL_CTL_DEL,fd,&ev);
}

static void modify_event(int epollfd,int fd,int state)
{
  struct epoll_event ev;
  ev.events = state;
  ev.data.fd = fd;
  epoll_ctl(epollfd,EPOLL_CTL_MOD,fd,&ev);
}								 
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