libevent使用

利用libevent编写服务端程序，主要有3部分

//创建主通知链base

1.base = event_base_new();

 

//创建要监听的事件，并将其加入到主通知链中。

2.listener_event = event_new(base, listener, EV_READ|EV_PERSIST, do_accept, (void*)base);

  event_add(listener_event, NULL);

  event_free( listener_event ); 释放由event_new申请的结构体

 

//主循环

3.event_base_dispatch(base)

 

相关网址：

以下为参考文档网址

 

http://blog.csdn.net/laoyi19861011/article/details/6539244

 

下面的代码转自

下面程序重点：

因为do_read, do_write是异步的，所以下面的程序使用了state这个结构体变量将do_read和do_write联系起来。 解决了异步之间的问题。

/* For sockaddr_in */
#include <netinet/in.h>
/* For socket functions */
#include <sys/socket.h>
/* For fcntl */
#include <fcntl.h>

#include <event2/event.h>

#include <assert.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>

#define MAX_LINE 16384
#define PORT 9999

void do_read(evutil_socket_t fd, short events, void *arg);
void do_write(evutil_socket_t fd, short events, void *arg);

struct fd_state
{
    char buffer[MAX_LINE];
    size_t buffer_used;

    size_t n_written;
    size_t write_upto;

    struct event *read_event;
    struct event *write_event;
};

struct fd_state *
alloc_fd_state(struct event_base *base, evutil_socket_t fd)
{
    struct fd_state *state = (struct fd_state *)malloc(sizeof(struct fd_state));
    if (!state)
    {
        return NULL;
    }

    state->read_event = event_new(base, fd, EV_READ|EV_PERSIST, do_read, state);
    if (!state->read_event)
    {
        free(state);
        return NULL;
    }

    state->write_event =
    event_new(base, fd, EV_WRITE|EV_PERSIST, do_write, state);
    if (!state->write_event)
    {
        event_free(state->read_event);
        free(state);
        return NULL;
    }

    assert(state->write_event);

    return state;
}

void
free_fd_state(struct fd_state *state)
{
    event_free(state->read_event);
    event_free(state->write_event);
    free(state);
}

void
do_read(evutil_socket_t fd, short events, void *arg)
{
    struct fd_state *state = arg;
    char buf[1024];
    int i;
    ssize_t result;
    while (1)
    {
//        assert(state->write_event);
        result = recv(fd, buf, sizeof(buf), 0);
        if (result <= 0)
            break;
        printf( "[%s][%d]buf=[%s]len=[%d]\n", __FILE__, __LINE__, buf, result );
    }

    memcpy( state->buffer, "reply", sizeof("reply") );
    assert(state->write_event);
    event_add(state->write_event, NULL);
    state->write_upto = state->buffer_used;

    if (result == 0)
    {
        free_fd_state(state);
    }
    else if (result < 0)
    {
        if (errno == EAGAIN) // XXXX use evutil macro
        return;
        perror("recv");
        free_fd_state(state);
    }
}





void
do_write(evutil_socket_t fd, short events, void *arg)
{
    struct fd_state *state = arg;

    printf( "[%d]\n", __LINE__ );
//    while (state->n_written < state->write_upto)
    {
//        ssize_t result = send(fd, state->buffer + state->n_written,
//             state->write_upto - state->n_written, 0);
        ssize_t result = send(fd, state->buffer, strlen(state->buffer), 0 );
        if (result < 0)
        {
            if (errno == EAGAIN) // XXX use evutil macro
                return;
            free_fd_state(state);
                return;
        }
        assert(result != 0);

        state->n_written += result;
    }

//    if (state->n_written == state->buffer_used)
    {
        state->n_written = state->write_upto = state->buffer_used = 1;
    }

    event_del(state->write_event);
}

void
do_accept(evutil_socket_t listener, short event, void *arg)
{
    struct event_base *base = arg;
    struct sockaddr_storage ss;
    socklen_t slen = sizeof(ss);

    int fd = accept(listener, (struct sockaddr*)&ss, &slen);
    if (fd < 0)
    { // XXXX eagain??
        perror("accept");
    }
    else if (fd > FD_SETSIZE)
    {
        close(fd); // XXX replace all closes with EVUTIL_CLOSESOCKET */
    }
    else
    {
        struct fd_state *state;
        evutil_make_socket_nonblocking(fd);
        state = alloc_fd_state(base, fd);

        assert(state); /*XXX err*/
        assert(state->write_event);
        event_add(state->read_event, NULL);
    }
}

void
run(void)
{
    evutil_socket_t listener;
    struct sockaddr_in sin;
    struct event_base *base;
    struct event *listener_event;

    base = event_base_new();
    if (!base)
    return; /*XXXerr*/

    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = 0;
    sin.sin_port = htons(PORT);

    listener = socket(AF_INET, SOCK_STREAM, 0);
    evutil_make_socket_nonblocking(listener);

    #ifndef WIN32
    {
        int one = 1;
        setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
    }
    #endif

    if (bind(listener, (struct sockaddr*)&sin, sizeof(sin)) < 0) {
        perror("bind");
        return;
    }

    if (listen(listener, 16)<0) {
        perror("listen");
        return;
    }

    //do_accept(evutil_socket_t listener, short event, void *arg)
    listener_event = event_new(base, listener, EV_READ|EV_PERSIST, do_accept, (void*)base);
    /*XXX check it */
    event_add(listener_event, NULL);

    event_base_dispatch(base);
}

int
main(int c, char **v)
{
    setvbuf(stdout, NULL, _IONBF, 0);

    run();
    return 0;
}