#include <iostream>
#include <event2/event.h>
#include <thread>
#include <event2/listener.h>
#include <event2/bufferevent.h>
#include <event2/buffer.h>
#ifndef _WIN32
#include <signal.h>
#endif
#include <errno.h>
#include <string.h>
#define SPORT 5001
using namespace std;




bufferevent_filter_result filter_in(evbuffer* s, evbuffer* d, ev_ssize_t limit, bufferevent_flush_mode mode, void* ctx) {
	
	cout << "filter_in" << endl;

	//读取并清理源数据
	char data[1024] = { 0 };
	int len = evbuffer_remove(s, data, sizeof(data) - 1);

	//把所有字母转成大小
	for (size_t i = 0; i < len; i++)
	{
		data[i] = toupper(data[i]);
	}

	evbuffer_add(d, data, len);
	return BEV_OK;
}

bufferevent_filter_result filter_out(evbuffer* s, evbuffer* d, ev_ssize_t limit, bufferevent_flush_mode mode, void* ctx) {
	cout << "filter_out" << endl;

	//读取并清理源数据
	char data[1024] = { 0 };
	int len = evbuffer_remove(s, data, sizeof(data) - 1);

	//将回复给客户端的消息进行预处理
	string str = "";
	str += "=========\n";
	str += data;
	str += "=========\n";
	evbuffer_add(d, str.c_str(), str.size());
	return BEV_OK;
}


void read_cb(bufferevent* bev, void* arg) {
	cout << "read_cb" << endl;
	char data[1024] = { 0 };
	int len = bufferevent_read(bev, data, sizeof(data) - 1);
	cout << data << endl;

	//回消息给客户端, 经过输出过滤
	bufferevent_write(bev, data, len);
}


void write_cb(bufferevent* bev, void* arg) {
	cout << "write_cb" << endl;
}


void event_cb(bufferevent* bev, short events, void* arg) {
	cout << "event_cb" << endl;
}


void listen_cb(evconnlistener* e,  evutil_socket_t s, sockaddr *a, int socklen, void* arg) {
	cout << "====listen_cb======" << endl;

	event_base* base = (event_base*)arg;

	//创建bufferevent 绑定bufferevent filter
	bufferevent* bev = bufferevent_socket_new(base, s, BEV_OPT_CLOSE_ON_FREE);
	bufferevent* bev_filter = bufferevent_filter_new(
		bev,                        // bufferevent_socket上下文
		filter_in,                  // 输入过滤函数
		filter_out,                 // 输出过滤函数
		BEV_OPT_CLOSE_ON_FREE,      // 关闭filter同时关闭bufferevent
		0,                          // 清理的回调函数
		0                           // 传递给清理回调函数的参数
	);

	//设置bufferevent的回调函数
	bufferevent_setcb(bev_filter, read_cb, write_cb, event_cb, NULL);
	bufferevent_enable(bev_filter, EV_READ | EV_WRITE);
}


int main(int argc, char** argv) {
#if _WIN32
	//windowns 初始化socket库
	WSADATA wsa;
	WSAStartup(MAKEWORD(2, 2), &wsa);
#else
	//linux 忽略管道信号，发送数据给已关闭的socket
	if (signal(SIGPIPE, SIG_IGN) == SIG_ERR)
		return 1;
#endif

	//创建socket(使用tcp/ip协议)
	event_base* base = event_base_new();
	if (base)
	{
		cout << "event_base_new success" << endl;
	}

	// 绑定端口与地址
	sockaddr_in sin;
	memset(&sin, 0, sizeof(sin));
	sin.sin_family = AF_INET;
	sin.sin_port = htons(SPORT);
	evconnlistener* ev = evconnlistener_new_bind(
		base,                                            // libevent上下文
		listen_cb,                                       // 回调函数
		base,                                            // 回调函数的参数arg
		LEV_OPT_REUSEABLE | LEV_OPT_CLOSE_ON_FREE,       // 地址重用，关闭evconnlistener同时关闭socket
		10,                                              // 连接队列大小，对应listen函数
		(sockaddr*)&sin, sizeof(sin)                     // 绑定端口与地址
	);


	//进入事件主循环
	event_base_dispatch(base);
	event_base_free(base);
#ifdef _WIN32
	WSACleanup();
#endif // _WIN32
	return 0;
}

Makefile

test_buffer_filter:test_buffer_filter.cpp
        g++ $^ -o $@ -levent
        ./$@


clean:
        rm -rf test_buffer_filter
        rm -rf *.o

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