redhat enterprise 5 下的boost::asio 库应用（4）

libev的demo上篇也说到了，那么epoll到底是如何工作的呢，为了更好的接触到底层，我们直接用epoll的API来设计一个echoserver

client的code和上篇一样

echoserver.cpp 如下

#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;  
    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;  
    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]\n", ev->fd);  
    else  
        printf("Event Add OK[fd=%d]\n", ev->fd);  
}  
// 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;  
myevent_s g_Events[MAX_EVENTS+1]; // g_Events[MAX_EVENTS] is used by listen fd   
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: bad accept", __func__);  
        }  
        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   
        if(fcntl(nfd, F_SETFL, O_NONBLOCK) < 0) break;  
        // add a read event for receive data   
        EventSet(&g_Events[i], nfd, RecvData, &g_Events[i]);  
        EventAdd(g_epollFd, EPOLLIN|EPOLLET, &g_Events[i]);  
        printf("new conn[%s:%d][time:%d]\n", inet_ntoa(sin.sin_addr), ntohs(sin.sin_port), g_Events[i].last_active);  
    }while(0);  
}  
// 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, sizeof(ev->buff)-1, 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|EPOLLET, ev);  
    }  
    else if(len == 0)  
    {  
        close(ev->fd);  
        printf("[fd=%d] closed gracefully.\n", fd);  
    }  
    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->len, 0);  
    ev->len = 0;  
    EventDel(g_epollFd, ev);  
    if(len > 0)  
    {  
        // change to receive event   
        EventSet(ev, fd, RecvData, ev);  
        EventAdd(g_epollFd, EPOLLIN|EPOLLET, ev);  
    }  
    else  
    {  
        close(ev->fd);  
        printf("recv[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|EPOLLET, &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)  
{  
    short port = 12345; // default port   
    if(argc == 2){  
        port = atoi(argv[1]);  
    }  
    // create epoll   
    g_epollFd = epoll_create(MAX_EVENTS);  
    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);  
    // 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;  
} 

和windows下的iocp的原理很形似，都是event通知，用回调函数。

那下篇我们来具体分析下，各个API和call_back的关系。