muduo_net库源码分析（25)

TCP网络编程本质

    TCP网络编程最本质是的处理三个半事件
        连接建立：服务器accept（被动）接受连接，客户端connect（主动）发起连接
        连接断开：主动断开（close、shutdown），被动断开（read返回0）
        消息到达：文件描述符可读
        消息发送完毕：这算半个。对于低流量的服务，可不必关心这个事件;这里的发送完毕是指数据写入操作系统缓冲区，将由TCP协议栈负责数据的发送与重传，不代表对方已经接收到数据。

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EchoServer类图   

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什么都不做的EventLoop

• • one loop   per thread

    意思是说每个线程最多只能有一个EventLoop对象。

  • EventLoop对象构造的时候，会检查当前线程是否已经创建了其他EventLoop对象，如果已创建，终止程序（LOG_FATAL）

  • EventLoop构造函数会记住本对象所属线程（threadId_）。

  • 创建了EventLoop对象的线程称为IO线程，其功能是运行事件循环（EventLoop::loop）

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EventLoop 头文件

EventLoop.h

// Copyright 2010, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.

// Author: Shuo Chen (chenshuo at chenshuo dot com)
//
// This is a public header file, it must only include public header files.

#ifndef MUDUO_NET_EVENTLOOP_H
#define MUDUO_NET_EVENTLOOP_H

#include 

#include 
#include 

namespace muduo
{
namespace net
{

///
/// Reactor, at most one per thread.
///
/// This is an interface class, so don't expose too much details.
class EventLoop : boost::noncopyable
{
 public:
  EventLoop();
  ~EventLoop();  // force out-line dtor, for scoped_ptr members.

  ///
  /// Loops forever.
  ///
  /// Must be called in the same thread as creation of the object.
  ///
  void loop();

   //断言是否是当前的线程

  void assertInLoopThread()
  {
      //过是当前线程，直接跳过，否则调用abortNotInLoopThread
    if (!isInLoopThread())
    {
      abortNotInLoopThread();
    }
  }
  //测试是否为当前线程
  bool isInLoopThread() const { return threadId_ == CurrentThread::tid(); }

  static EventLoop* getEventLoopOfCurrentThread();

 private:
  void abortNotInLoopThread();

  bool looping_; /* atomic , 是否处于事件循环*/
  const pid_t threadId_;        // 当前对象所属线程ID
};

}
}
#endif  // MUDUO_NET_EVENTLOOP_H

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EventLoop 源文件

EventLoop.cpp

// Copyright 2010, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.

// Author: Shuo Chen (chenshuo at chenshuo dot com)

#include 

#include 

#include 

using namespace muduo;
using namespace muduo::net;

namespace
{
// 当前线程EventLoop对象指针
// 线程局部存储 ，如果不用__thread修饰的话，那么就是线程共共享的了
//这样达不到目标，。。
//初始化时，设为0就OK了
__thread EventLoop* t_loopInThisThread = 0;
}

EventLoop* EventLoop::getEventLoopOfCurrentThread()
{
  return t_loopInThisThread;
}

EventLoop::EventLoop()
  : looping_(false), //初始化为false ，表示当前还没有处于事件循环状态
    threadId_(CurrentThread::tid()) //当前的线程Id ，用于标识
{
  LOG_TRACE << "EventLoop created " << this << " in thread " << threadId_;
  // 如果当前线程已经创建了EventLoop对象，终止(LOG_FATAL),否者的话，设为当前线程this
  if (t_loopInThisThread)
  {
    LOG_FATAL << "Another EventLoop " << t_loopInThisThread
              << " exists in this thread " << threadId_;
  }
  else
  {
    t_loopInThisThread = this;
  }
}

EventLoop::~EventLoop()
{
  t_loopInThisThread = NULL;
}

// 事件循环，该函数不能跨线程调用
// 只能在创建该对象的线程中调用
void EventLoop::loop()
{
//断言还没有事件循环
  assert(!looping_);
  // 断言当前处于创建该对象的线程中
  assertInLoopThread();
  //把事件循环标识设为true
  looping_ = true;
  LOG_TRACE << "EventLoop " << this << " start looping";
  //关注事件为NULL，个数为0，延时5000
  ::poll(NULL, 0, 5*1000);

  LOG_TRACE << "EventLoop " << this << " stop looping";
  //事件循环标识设为false ，这只是测试程序
  looping_ = false;
}

//终止程序
void EventLoop::abortNotInLoopThread()
{
  LOG_FATAL << "EventLoop::abortNotInLoopThread - EventLoop " << this
            << " was created in threadId_ = " << threadId_
            << ", current thread id = " <<  CurrentThread::tid();

}

---

EventLoop 的测试程序1

#include 

#include 

using namespace muduo;
using namespace muduo::net;

/*
该程序 主要是用来测试EventLoop 是否是 一个Thread一个EventLoop
**/
void threadFunc()
{
    printf("threadFunc(): pid = %d, tid = %d\n",
        getpid(), CurrentThread::tid());

    EventLoop loop;
    loop.loop();
}

int main(void)
{
    printf("main(): pid = %d, tid = %d\n",
        getpid(), CurrentThread::tid());

    EventLoop loop;

    Thread t(threadFunc);
    t.start();

    loop.loop();
    t.join();
    return 0;
}

程序输出

[root@localhost bin]# ./reactor_test01
main(): pid = 2724, tid = 2724
20131018 04:12:55.305234Z  2724 TRACE EventLoop EventLoop created 0xBFA6B2C0 in thread 2724 - EventLoop.cc:36
20131018 04:12:55.305599Z  2724 TRACE loop EventLoop 0xBFA6B2C0 start looping - EventLoop.cc:62
threadFunc(): pid = 2724, tid = 2725
20131018 04:12:55.305792Z  2725 TRACE EventLoop EventLoop created 0xB77E0068 in thread 2725 - EventLoop.cc:36
20131018 04:12:55.305809Z  2725 TRACE loop EventLoop 0xB77E0068 start looping - EventLoop.cc:62
20131018 04:13:00.321713Z  2724 TRACE loop EventLoop 0xBFA6B2C0 stop looping - EventLoop.cc:66
20131018 04:13:00.321779Z  2725 TRACE loop EventLoop 0xB77E0068 stop looping - EventLoop.cc:66
[root@localhost bin]#

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测试程序2

#include 

#include 
/**
该程序主要用来测试，多个线程使用同一个eventloop时，程序将会错误终止！！
**/
using namespace muduo;
using namespace muduo::net;

EventLoop* g_loop;

void threadFunc()
{
    g_loop->loop();
}

int main(void)
{
    EventLoop loop;
    g_loop = &loop;
    Thread t(threadFunc);
    t.start();
    t.join();
    return 0;
}

程序输出

[root@localhost bin]# ./reactor_test02
20131018 04:15:09.010234Z  2730 TRACE EventLoop EventLoop created 0xBFD53730 in thread 2730 - EventLoop.cc:36
20131018 04:15:09.010768Z  2731 FATAL EventLoop::abortNotInLoopThread - EventLoop 0xBFD53730 was created in threadId_ = 2730, current thread id = 2731 - EventLoop.cc:72
Aborted
[root@localhost bin]#