Linux IO模式及 select、poll、epoll详解及源码（转）

#define IPADDRESS   "127.0.0.1"
#define PORT        8787
#define MAXSIZE     1024
#define LISTENQ     5
#define FDSIZE      1000
#define EPOLLEVENTS 100

listenfd = socket_bind(IPADDRESS,PORT);

struct epoll_event events[EPOLLEVENTS];

//创建一个描述符
epollfd = epoll_create(FDSIZE);

//添加监听描述符事件
add_event(epollfd,listenfd,EPOLLIN);

//循环等待
for ( ; ; ){
//该函数返回已经准备好的描述符事件数目
ret = epoll_wait(epollfd,events,EPOLLEVENTS,-1);
//处理接收到的连接
handle_events(epollfd,events,ret,listenfd,buf);
}

//事件处理函数
static void handle_events(int epollfd,struct epoll_event *events,int num,int listenfd,char *buf)
{
int i;
int fd;
//进行遍历;这里只要遍历已经准备好的io事件。num并不是当初epoll_create时的FDSIZE。
for (i = 0;i < num;i++)
{
fd = events[i].data.fd;
//根据描述符的类型和事件类型进行处理
if ((fd == listenfd) &&(events[i].events & EPOLLIN))
handle_accpet(epollfd,listenfd);
else if (events[i].events & EPOLLIN)
do_read(epollfd,fd,buf);
else if (events[i].events & EPOLLOUT)
do_write(epollfd,fd,buf);
}
}

//添加事件
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);
}

//处理接收到的连接。将文件描述符添加到epoll监控队列
static void handle_accpet(int epollfd,int listenfd){
int clifd;
struct sockaddr_in cliaddr;
socklen_t  cliaddrlen;
clifd = accept(listenfd,(struct sockaddr*)&cliaddr,&cliaddrlen);
if (clifd == -1)
perror("accpet error:");
else {
printf("accept a new client: %s:%d\n",inet_ntoa(cliaddr.sin_addr),cliaddr.sin_port);  //添加一个客户描述符和事件
add_event(epollfd,clifd,EPOLLIN);
}
}

//读处理
static void do_read(int epollfd,int fd,char *buf){
int nread;
nread = read(fd,buf,MAXSIZE);
if (nread == -1)     {
perror("read error:");
close(fd); //记住close fd
delete_event(epollfd,fd,EPOLLIN); //删除监听
}
else if (nread == 0)     {
fprintf(stderr,"client close.\n");
close(fd); //记住close fd
delete_event(epollfd,fd,EPOLLIN); //删除监听
}
else {
printf("read message is : %s",buf);
//修改描述符对应的事件，由读改为写
modify_event(epollfd,fd,EPOLLOUT);
}
}

//写处理
static void do_write(int epollfd,int fd,char *buf) {
int nwrite;
nwrite = write(fd,buf,strlen(buf));
if (nwrite == -1){
perror("write error:");
close(fd);   //记住close fd
delete_event(epollfd,fd,EPOLLOUT);  //删除监听
}else{
modify_event(epollfd,fd,EPOLLIN);
}
memset(buf,0,MAXSIZE);
}

//删除事件
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);
}

//修改事件
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);
}

//注：另外一端我就省了