libevent源代码分析-介绍、安装、使用

Libevent介绍

在include\event2\event.h中有关于Libevent的介绍，这里简单翻译介绍一下：
Libevent是以事件为驱动的开发可扩展的网络服务端的库。开放的API设置事件的回调函数，当事件来临时调用这个回调函数。它还支持信号和定时器。

开发者只需要简单的add/remove来将事件添加到event loop中，通过event_dispatch驱动event。

Libevent支持 /dev/poll, kqueue(2), select(2), poll(2),
epoll(4), and evports。内部的事件机制和应用接口相互独立，因此内部实现的更新不影响应用程序。Libevent可以用于多线程。

安装

在官网下载http://libevent.org。我下载了最新版本libevent-2.0.22-stable.tar.gz。放到目录，解压缩tar -zxvf ibevent-2.0.22-stable.tar.gz。
解压后进入目录，进行配置，把库安装到/usr目录下

./configure --prefix=/usr

编译安装

sudo makesudo make install

查看是否安装成功：

ls -al /usr/lib|grep libeventlrwxrwxrwx   1 root root           21  8月 11 00:04 libevent-2.0.so.5 -> libevent-2.0.so.5.1.9-rwxr-xr-x   1 root root       920932  8月 11 00:04 libevent-2.0.so.5.1.9-rw-r--r--   1 root root      1309268  8月 11 00:04 libevent.alrwxrwxrwx   1 root root           26  8月 11 00:04 libevent_core-2.0.so.5 -> libevent_core-2.0.so.5.1.9-rwxr-xr-x   1 root root       557242  8月 11 00:04 libevent_core-2.0.so.5.1.9-rw-r--r--   1 root root       821804  8月 11 00:04 libevent_core.a-rwxr-xr-x   1 root root          974  8月 11 00:04 libevent_core.lalrwxrwxrwx   1 root root           26  8月 11 00:04 libevent_core.so -> libevent_core-2.0.so.5.1.9lrwxrwxrwx   1 root root           27  8月 11 00:04 libevent_extra-2.0.so.5 -> libevent_extra-2.0.so.5.1.9-rwxr-xr-x   1 root root       379504  8月 11 00:04 libevent_extra-2.0.so.5.1.9-rw-r--r--   1 root root       487536  8月 11 00:04 libevent_extra.a-rwxr-xr-x   1 root root          981  8月 11 00:04 libevent_extra.lalrwxrwxrwx   1 root root           27  8月 11 00:04 libevent_extra.so -> libevent_extra-2.0.so.5.1.9-rwxr-xr-x   1 root root          939  8月 11 00:04 libevent.lalrwxrwxrwx   1 root root           29  8月 11 00:04 libevent_openssl-2.0.so.5 -> libevent_openssl-2.0.so.5.1.9-rwxr-xr-x   1 root root        90317  8月 11 00:04 libevent_openssl-2.0.so.5.1.9-rw-r--r--   1 root root       110340  8月 11 00:04 libevent_openssl.a-rwxr-xr-x   1 root root         1010  8月 11 00:04 libevent_openssl.lalrwxrwxrwx   1 root root           29  8月 11 00:04 libevent_openssl.so -> libevent_openssl-2.0.so.5.1.9lrwxrwxrwx   1 root root           30  8月 11 00:04 libevent_pthreads-2.0.so.5 -> libevent_pthreads-2.0.so.5.1.9-rwxr-xr-x   1 root root        20571  8月 11 00:04 libevent_pthreads-2.0.so.5.1.9-rw-r--r--   1 root root        14322  8月 11 00:04 libevent_pthreads.a-rwxr-xr-x   1 root root         1002  8月 11 00:04 libevent_pthreads.lalrwxrwxrwx   1 root root           30  8月 11 00:04 libevent_pthreads.so -> libevent_pthreads-2.0.so.5.1.9lrwxrwxrwx   1 root root           21  8月 11 00:04 libevent.so -> libevent-2.0.so.5.1.9

例子

写各测试程序，编译时要设置参数-levent，连接libevent的库。

echoServer.cc

#include <sys/socket.h>#include <sys/types.h>#include <netinet/in.h>#include <stdio.h>#include <string.h>#include <event.h>#include <stdlib.h>#include <unistd.h>#define PORT        8000#define BACKLOG     5#define MEM_SIZE    1024struct event_base* base;struct sockEvent{    struct event* readEvent;    struct event* writeEvent;    char* buffer;};void releaseSockEvent(struct sockEvent* ev)//delete from base and free it{    event_del(ev->readEvent);    free(ev->readEvent);    free(ev->writeEvent);    free(ev->buffer);    free(ev);}void handleWrite(int sock, short event, void* arg){    char* buffer = (char*)arg;    send(sock, buffer, strlen(buffer), 0);    free(buffer);}void handldRead(int sock, short event, void* arg){    struct event* writeEvent;    int size;    struct sockEvent* ev = (struct sockEvent*)arg;    ev->buffer = (char*)malloc(MEM_SIZE);    bzero(ev->buffer, MEM_SIZE);    size = recv(sock, ev->buffer, MEM_SIZE, 0);    printf("receive data:%s, size:%d\n", ev->buffer, size);    if (size == 0) //client has send FIN    {        releaseSockEvent(ev);        close(sock);        return;    }    //add event to base to send the received data    event_set(ev->writeEvent, sock, EV_WRITE, handleWrite, ev->buffer);    event_base_set(base, ev->writeEvent);    event_add(ev->writeEvent, NULL);}void handleAccept(int sock, short event, void* arg)//when new connection coming, calling this func{    struct sockaddr_in cli_addr;    int newfd;    socklen_t sinSize;    struct sockEvent* ev = (struct sockEvent*)malloc(sizeof(struct sockEvent));    ev->readEvent = (struct event*)malloc(sizeof(struct event));    ev->writeEvent = (struct event*)malloc(sizeof(struct event));    sinSize = sizeof(struct sockaddr_in);    newfd = accept(sock, (struct sockaddr*)&cli_addr, &sinSize);    //set the new coming connection event    event_set(ev->readEvent, newfd, EV_READ|EV_PERSIST, handldRead, ev);    event_base_set(base, ev->readEvent);    event_add(ev->readEvent, NULL);}int main(int argc, char* argv[]){    struct sockaddr_in serverAddr;    int sock;    sock = socket(AF_INET, SOCK_STREAM, 0);    int on = 1;    setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(int));    //memset(&serverAddr, 0, sizeof(serverAddr));    bzero(&serverAddr, sizeof(serverAddr));    serverAddr.sin_family = AF_INET;    serverAddr.sin_port = htons(PORT);    serverAddr.sin_addr.s_addr = INADDR_ANY;    bind(sock, (struct sockaddr*)&serverAddr, sizeof(struct sockaddr));    listen(sock, BACKLOG);    struct event listenEvent;    base = event_base_new();//Create new EventBase    event_set(&listenEvent, sock, EV_READ|EV_PERSIST, handleAccept, NULL);//conbine listenEvent and  it's callback function    event_base_set(base, &listenEvent);    event_add(&listenEvent, NULL);    event_base_dispatch(base);//start base    return 0;}