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 make
sudo make install

查看是否安装成功：

ls -al /usr/lib|grep libevent
lrwxrwxrwx   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.a
lrwxrwxrwx   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.la
lrwxrwxrwx   1 root root           26  8月 11 00:04 libevent_core.so -> libevent_core-2.0.so.5.1.9
lrwxrwxrwx   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.la
lrwxrwxrwx   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.la
lrwxrwxrwx   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.la
lrwxrwxrwx   1 root root           29  8月 11 00:04 libevent_openssl.so -> libevent_openssl-2.0.so.5.1.9
lrwxrwxrwx   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.la
lrwxrwxrwx   1 root root           30  8月 11 00:04 libevent_pthreads.so -> libevent_pthreads-2.0.so.5.1.9
lrwxrwxrwx   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 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define PORT        8000
#define BACKLOG     5
#define MEM_SIZE    1024

struct 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;
}