epoll()

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epoll通过在Linux内核中申请一个简易的文件系统(文件系统一般用什么数据结构实现?B+树)。
1)调用epoll_create()建立一个epoll对象(在epoll文件系统中为这个句柄对象分配资源)

2)调用epoll_ctl向epoll对象中添加这100万个连接的套接字

3)调用epoll_wait收集发生的事件的连接
进程启动时建立一个epoll对象,然后在需要的时候向这个epoll对象中添加或者删除连接。同时,epoll_wait的效率也非常高,因为调用epoll_wait时,并没有一股脑的向操作系统复制这100万个连接的句柄数据,内核也不需要去遍历全部的连接。

*/
#include <sys/socket.h>
#include <sys/epoll.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <iostream>
using namespace std;
#define MAX_EVENTS 500
struct myevent_s

    int fd;
    void (*call_back)(int fd, int events, void *arg);
    int events;
    void *arg;
    int status; // 1: in epoll wait list, 0 not in
    char buff[128]; // recv data buffer
    int len, s_offset;
    long last_active; // last active time
;
// set event
void EventSet(myevent_s *ev, int fd, void (*call_back)(int, int, void*), void *arg)

    ev->fd = fd;
    ev->call_back = call_back;
    ev->events = 0;
    ev->arg = arg;
    ev->status = 0;
    bzero(ev->buff, sizeof(ev->buff));
    ev->s_offset = 0;
    ev->len = 0;
    ev->last_active = time(NULL);

// add/mod an event to epoll
void EventAdd(int epollFd, int events, myevent_s *ev)

    struct epoll_event epv = 0, 0;
    int op;
    epv.data.ptr = ev;
    epv.events = ev->events = events;
    if(ev->status == 1)
        op = EPOLL_CTL_MOD;
    
    else
        op = EPOLL_CTL_ADD;
        ev->status = 1;
    
    if(epoll_ctl(epollFd, op, ev->fd, &epv) < 0)
        printf("Event Add failed[fd=%d], evnets[%d]\n", ev->fd, events);
    else
        printf("Event Add OK[fd=%d], op=%d, evnets[%0X]\n", ev->fd, op, events);

// delete an event from epoll
void EventDel(int epollFd, myevent_s *ev)

    struct epoll_event epv = 0, 0;
    if(ev->status != 1) return;
    epv.data.ptr = ev;
    ev->status = 0;
    epoll_ctl(epollFd, EPOLL_CTL_DEL, ev->fd, &epv);

int g_epollFd; //global
myevent_s g_Events[MAX_EVENTS+1]; // g_Events[MAX_EVENTS] is used by listen fd  global array
void RecvData(int fd, int events, void *arg);
void SendData(int fd, int events, void *arg);
// accept new connections from clients
void AcceptConn(int fd, int events, void *arg)

    struct sockaddr_in sin;
    socklen_t len = sizeof(struct sockaddr_in);
    int nfd, i;
    // accept
    if((nfd = accept(fd, (struct sockaddr*)&sin, &len)) == -1)
    
        if(errno != EAGAIN && errno != EINTR)
        
        
        printf("%s: accept, %d", __func__, errno);
        return;
    
    do
    
        for(i = 0; i < MAX_EVENTS; i++)
        
            if(g_Events[i].status == 0)
            
                break;
            
        
        if(i == MAX_EVENTS)
        
            printf("%s:max connection limit[%d].", __func__, MAX_EVENTS);
            break;
        
        // set nonblocking
        int iret = 0;
        if((iret = fcntl(nfd, F_SETFL, O_NONBLOCK)) < 0)
        
            printf("%s: fcntl nonblocking failed:%d", __func__, iret);
            break;
        
        // add a read event for receive data
        EventSet(&g_Events[i], nfd, RecvData, &g_Events[i]);
        EventAdd(g_epollFd, EPOLLIN, &g_Events[i]);
    while(0);
    printf("new conn[%s:%d][time:%d], pos[%d]\n", inet_ntoa(sin.sin_addr),
            ntohs(sin.sin_port), g_Events[i].last_active, i);

// receive data
void RecvData(int fd, int events, void *arg)

    struct myevent_s *ev = (struct myevent_s*)arg;
    int len;
    // receive data
    len = recv(fd, ev->buff+ev->len, sizeof(ev->buff)-1-ev->len, 0);
    EventDel(g_epollFd, ev);
    if(len > 0)
    
        ev->len += len;
        ev->buff[len] = ‘\0‘;
        printf("C[%d]:%s\n", fd, ev->buff);
        // change to send event
        EventSet(ev, fd, SendData, ev);
        EventAdd(g_epollFd, EPOLLOUT, ev);
    
    else if(len == 0)
    
        close(ev->fd);
        printf("[fd=%d] pos[%d], closed gracefully.\n", fd, ev-g_Events);
    
    else
    
        close(ev->fd);
        printf("recv[fd=%d] error[%d]:%s\n", fd, errno, strerror(errno));
    

// send data
void SendData(int fd, int events, void *arg)

    struct myevent_s *ev = (struct myevent_s*)arg;
    int len;
    // send data
    len = send(fd, ev->buff + ev->s_offset, ev->len - ev->s_offset, 0);
    if(len > 0)
    
        printf("send[fd=%d], [%d<->%d]%s\n", fd, len, ev->len, ev->buff);
        ev->s_offset += len;
        if(ev->s_offset == ev->len)
        
            // change to receive event
            EventDel(g_epollFd, ev);
            EventSet(ev, fd, RecvData, ev);
            EventAdd(g_epollFd, EPOLLIN, ev);
        
    
    else
    
        close(ev->fd);
        EventDel(g_epollFd, ev);
        printf("send[fd=%d] error[%d]\n", fd, errno);
    

void InitListenSocket(int epollFd, short port)

    int listenFd = socket(AF_INET, SOCK_STREAM, 0);
    fcntl(listenFd, F_SETFL, O_NONBLOCK); // set non-blocking
    printf("server listen fd=%d\n", listenFd);
    EventSet(&g_Events[MAX_EVENTS], listenFd, AcceptConn, &g_Events[MAX_EVENTS]);
    // add listen socket
    EventAdd(epollFd, EPOLLIN, &g_Events[MAX_EVENTS]);
    // bind & listen
    sockaddr_in sin;
    bzero(&sin, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = INADDR_ANY;
    sin.sin_port = htons(port);
    bind(listenFd, (const sockaddr*)&sin, sizeof(sin));
    listen(listenFd, 5);

int main(int argc, char **argv)

    unsigned short port = 12345; // default port
    if(argc == 2)
        port = atoi(argv[1]);
    
    // create epoll
    g_epollFd = epoll_create(MAX_EVENTS);  //create a epoll obj
    if(g_epollFd <= 0) printf("create epoll failed.%d\n", g_epollFd);
    // create & bind listen socket, and add to epoll, set non-blocking
    InitListenSocket(g_epollFd, port);  //init socket
    // event loop
    struct epoll_event events[MAX_EVENTS];
    printf("server running:port[%d]\n", port);
    int checkPos = 0;
    while(1)
        // a simple timeout check here, every time 100, better to use a mini-heap, and add timer event
        long now = time(NULL);
        for(int i = 0; i < 100; i++, checkPos++) // doesn‘t check listen fd
        
            if(checkPos == MAX_EVENTS) checkPos = 0; // recycle
            if(g_Events[checkPos].status != 1) continue;
            long duration = now - g_Events[checkPos].last_active;
            if(duration >= 60) // 60s timeout
            
                close(g_Events[checkPos].fd);
                printf("[fd=%d] timeout[%d--%d].\n", g_Events[checkPos].fd, g_Events[checkPos].last_active, now);
                EventDel(g_epollFd, &g_Events[checkPos]);
            
        
        // wait for events to happen
        int fds = epoll_wait(g_epollFd, events, MAX_EVENTS, 1000);
        if(fds < 0)
            printf("epoll_wait error, exit\n");
            break;
        
        for(int i = 0; i < fds; i++)
            myevent_s *ev = (struct myevent_s*)events[i].data.ptr;
            if((events[i].events&EPOLLIN)&&(ev->events&EPOLLIN)) // read event
            
                ev->call_back(ev->fd, events[i].events, ev->arg);
            
            if((events[i].events&EPOLLOUT)&&(ev->events&EPOLLOUT)) // write event
            
                ev->call_back(ev->fd, events[i].events, ev->arg);
            
        
    
    // free resource
    return 0;


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