IO多路复用

IO多路复用

使用单线程处理多事件并发

1. select

//创建套接字并监听
int sockfd = socket(...);
bind(sockfd,...);
listen(sockfd,n);

//接收来自客户端的连接,假设有5个
for(int i = 0; i < 5; ++i){
    fds[i] = accept(sockfd,...);
    if(fds[i] > max) max = fds[i];
}

//select:

fd_set rset;
while(1){
    FD_ZERO(&rset);   //置0
    for(int i = 0; i < 5; ++i){
        FD_SET(fds[i],&rset);   //将对应的文件描述符在rset置1
    }
    select(max+1,&rset,NULL,NULL,NULL);   //有文件描述符读到数据的话则返回；

    for(int i = 0; i < 5; ++i){
        if(FD_ISSET(fds[i],&rset)){   //找到有数据的文件描述符，处理
            read(fds[i],buffer,sizeof(buffer)-1);
        }
    }
}

2. poll

for(int i = 0; i < 5; ++i){
    pollfds.fd = accept(sockfd,...);
    pollfd.events = POLLIN;
}

while(1){
    poll(pollfds,5,NULL);

    for(i = 0; i < 5; ++i){
        if(pollfds[i].revents & POLLIN){
            pollfds[i].revent = 0;
            read(pollfds[i].fd,buffer,sizeof(buffer));
        }
    }
}

3. epoll

//epoll:
 int server_fd,epoll_fd;
 server_fd = socket(AF_INET, SOCK_STREAM, 0);
 bind(...);
 listen(...)

 epoll_fd = epoll_create1(1);   
 epoll_ctl(epoll_fd, EPOLL_CTL_ADD, server_fd, &ev);  //注册
 while (1) {
        int num_events = epoll_wait(epoll_fd, events, MAX_EVENTS, -1); // 阻塞等待事件
        for (int i = 0; i < num_events; i++) {
            processing(...)处理
        }
}