libevent（八）bufferevent 基本原理 缓冲水位分析

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

//错误，超时（连接断开时会进入）
void event_cb(bufferevent* be, short events, void* arg) {
  cout << "[E]" << flush;
  
  //读取超时事件发生后，数据读取停止
  if (events&BEV_EVENT_TIMEOUT && events&BEV_EVENT_READING)
  {
    cout << "BEV_EVENT_TIMEOUT | BEV_EVENT_READING" << endl;
    //bufferevent_enable(be, EV_READ);
    bufferevent_free(be);
  }else if (events & BEV_EVENT_ERROR)
  {
    bufferevent_free(be);
  }
  else
  {
    cout << "others" << endl;
  }
}


void read_cb(bufferevent* be, void* arg) {
  cout << "read buffer data[R]" << flush;
  char data[1024] = { 0 };

  //读取输入缓冲数据
  int len = bufferevent_read(be, data, sizeof(data) - 1);
  cout << "[" << data << "]" << endl;
  if (len <= 0)return;
  if (strstr(data, "quit")!=NULL) {
    cout << "quit and close socket!" << endl;
    bufferevent_free(be);
  }
  //发送数据，写入到输出缓冲
  bufferevent_write(be, "OK", 3);
}


void write_cb(bufferevent* be, void* arg) {
  cout << "[W]" << flush;
}



void listen_cb(evconnlistener* ev, evutil_socket_t s, sockaddr* sin, int slen, void* arg) {
  cout << ">>>listen_cb" << endl;
  event_base* base = (event_base*)arg;

  //创建bufferevent上下文(清理bufferevent时关闭socket)
  bufferevent* bev = bufferevent_socket_new(base, s, BEV_OPT_CLOSE_ON_FREE);

  //添加监控事件（读写）
  bufferevent_enable(bev, EV_READ | EV_WRITE);

  //设置水位 -- 读取水位(low_water=10, hight_water=0, 0表示无限制), 发送的数据至少10个字符，回调函数才被调用
  //设置水位 -- 写入水位(low_water=10, hight_water=0, 0表示无限制), 少于5个字符，回调函数被调用
  bufferevent_setwatermark(bev, EV_READ, 10, 0);
  bufferevent_setwatermark(bev, EV_WRITE, 5, 0);

  //超时时间的设置
  timeval t1 = { 3,0 };
  bufferevent_set_timeouts(bev, &t1, 0);

  //设置回调函数
  bufferevent_setcb(bev, read_cb, write_cb, event_cb, base);
}



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
  event_base* base = event_base_new();

  //创建网络服务器(设定地址与端口)
  sockaddr_in sin;
  memset(&sin, 0, sizeof(sin));
  sin.sin_family = AF_INET;
  sin.sin_port = htons(SPORT);
  evconnlistener* ev = evconnlistener_new_bind(
    base, 
    listen_cb, //回调函数
    base,      //回调函数的参数arg
    LEV_OPT_REUSEABLE | LEV_OPT_CLOSE_ON_FREE, 10, 
    (sockaddr*)&sin, sizeof(sin)
  );


  //进入事件主循环
  event_base_dispatch(base);
  evconnlistener_free(ev);
  event_base_free(base);

#ifdef _WIN32
  WSACleanup();
#endif // _WIN32
  return 0;
}

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