了解libevent

最新推荐文章于 2023-02-06 22:41:40 发布

tianzimk

最新推荐文章于 2023-02-06 22:41:40 发布

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分类专栏： libevent 文章标签： libevent

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本文介绍了如何在Windows 7和Visual Studio 2010环境下编译libevent库，并提供了编译步骤及所需配置。此外，还给出了一个简单的测试程序示例，用于验证libevent的功能。

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感觉ACE太复杂了，了解下libevent，去libevent.org官网下载libevent包（libevent-2.0.22-stable.tar.gz）。

我的环境是Win7+VS2010，菜单打开Microsoft visual studio 2010命令行工具，找到libevent解压包目录编译，编译通过，如下图：

E:\MyCode\libevent-2.0.22-stable>nmake /f Makefile.nmake

Microsoft (R) 程序维护实用工具 10.00.30319.01 版
版权所有(C) Microsoft Corporation。保留所有权利。

        cl /IWIN32-Code /Iinclude /Icompat /DWIN32 /DHAVE_CONFIG_H /I. /Ox /W3 /
wd4996 /nologo /c event.c buffer.c bufferevent.c bufferevent_sock.c bufferevent_
pair.c listener.c evmap.c log.c evutil.c strlcpy.c signal.c bufferevent_filter.c
 evthread.c bufferevent_ratelim.c evutil_rand.c win32select.c evthread_win32.c b
uffer_iocp.c event_iocp.c bufferevent_async.c

生成了libevent.lib，libevent_core.lib，libevent_extras.lib三个静态库。

VS2010配置环境后，在网上找到以下程序测试通过。

// libevent test.cpp : 定义控制台应用程序的入口点。
//
#include "stdafx.h"

#include <string.h>
#include <errno.h>
#include <stdio.h>
#include <signal.h>

#ifndef WIN32
#include <netinet/in.h>
# ifdef _XOPEN_SOURCE_EXTENDED
#  include <arpa/inet.h>
# endif
#include <sys/socket.h>
#endif

#include "event2/bufferevent.h"
#include "event2/buffer.h"
#include "event2/listener.h"
#include "event2/util.h"
#include "event2/event.h"

#include <WinSock2.h>

static const char MESSAGE[] = "Hello, World!\n";
static const int PORT = 9995;

static void conn_writecb(struct bufferevent *bev, void *user_data)
{
    struct evbuffer *output = bufferevent_get_output(bev);
    if (evbuffer_get_length(output) == 0) 
    {
        printf("flushed answer\n");
        bufferevent_free(bev);
    }
}

static void conn_eventcb(struct bufferevent *bev, short events, void *user_data)
{
    if (events & BEV_EVENT_EOF) 
    {
        printf("Connection closed.\n");
    } 
    else if (events & BEV_EVENT_ERROR) 
    {
        printf("Got an error on the connection: %s\n",
            strerror(errno));/*XXX win32*/
    }
    /* None of the other events can happen here, since we haven't enabled
     * timeouts */
    bufferevent_free(bev);
}

static void signal_cb(evutil_socket_t sig, short events, void *user_data)
{
    struct event_base *base = (struct event_base *)user_data;
    struct timeval delay = { 2, 0 };

    printf("Caught an interrupt signal; exiting cleanly in two seconds.\n");

    event_base_loopexit(base, &delay);
}

static void listener_cb(struct evconnlistener *listener, evutil_socket_t fd,
    struct sockaddr *sa, int socklen, void *user_data)
{
    struct event_base *base = (struct event_base *)user_data;
    struct bufferevent *bev;

    bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
    if (!bev) 
    {
        fprintf(stderr, "Error constructing bufferevent!");
        event_base_loopbreak(base);
        return;
    }
    bufferevent_setcb(bev, NULL, conn_writecb, conn_eventcb, NULL);
    bufferevent_enable(bev, EV_WRITE);
    bufferevent_disable(bev, EV_READ);

    bufferevent_write(bev, MESSAGE, strlen(MESSAGE));
}

int main(int argc, char **argv)
{
    struct event_base *base;
    struct evconnlistener *listener;
    struct event *signal_event;

    struct sockaddr_in sin;

#ifdef WIN32
    WSADATA wsa_data;
    WSAStartup(0x0201, &wsa_data);
#endif

    base = event_base_new();
    if (!base) 
    {
        fprintf(stderr, "Could not initialize libevent!\n");
        return 1;
    }

    memset(&sin, 0, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_port = htons(PORT);

    listener = evconnlistener_new_bind(base, listener_cb, (void *)base,
        LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE, -1,
        (struct sockaddr*)&sin,
        sizeof(sin));

    if (!listener) 
    {
        fprintf(stderr, "Could not create a listener!\n");
        return 1;
    }

    signal_event = evsignal_new(base, SIGINT, signal_cb, (void *)base);

    if (!signal_event || event_add(signal_event, NULL)<0) 
    {
        fprintf(stderr, "Could not create/add a signal event!\n");
        return 1;
    }

    event_base_dispatch(base);

    evconnlistener_free(listener);
    event_free(signal_event);
    event_base_free(base);

    printf("done\n");
    return 0;
}

配置..\include目录时，记得把libevent-2.0.22-stable下WIN32-Code\event2下event-config.h头文件拷贝到工程配置目录..\include\event2中。

关于那三个lib介绍：

libevent_core.lib：All core event and buffer functionality. This library contains all the event_base, evbuffer, bufferevent, and utility functions.

libevent_extras.lib：This library defines protocol-specific functionality that you may or may not want for your application, including HTTP, DNS, and RPC.

libevent.lib：This library exists for historical reasons; it contains the contents of both libevent_core and libevent_extra. You shouldn’t use it; it may go away in a future version of Libevent.

接下来慢慢了解。