30muduo_net库源码分析（六）

1.EventThread

（1）任何一个线程，只要创建并运行了EventLoop，都称之为IO线程

（2）IO线程不一定是主线程

（3）muduo并发模型one loop per thread + threadpool

（4）为了方便今后使用，定义了EventLoopThread类，该类封装了IO线程

（5）EventLoopThread创建了一个线程

（6）在线程函数中创建了一个EvenLoop对象并调用EventLoop::loop

2.代码

1.EventLoopThread.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_EVENTLOOPTHREAD_H
#define MUDUO_NET_EVENTLOOPTHREAD_H

#include 
#include 
#include 

#include 

namespace muduo
{
namespace net
{

class EventLoop;

class EventLoopThread : boost::noncopyable
{
 public:
  typedef boost::function ThreadInitCallback;

  EventLoopThread(const ThreadInitCallback& cb = ThreadInitCallback());
  ~EventLoopThread();
  EventLoop* startLoop();	// 启动线程，该线程就成为了IO线程

 private:
  void threadFunc();		// 线程函数

  EventLoop* loop_;			// loop_指针指向一个EventLoop对象
  bool exiting_;
  Thread thread_;
  MutexLock mutex_;
  Condition cond_;
  ThreadInitCallback callback_;		// 回调函数在EventLoop::loop事件循环之前被调用
};

}
}

#endif  // MUDUO_NET_EVENTLOOPTHREAD_H

2.EventLoopthread.cc

// 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;


EventLoopThread::EventLoopThread(const ThreadInitCallback& cb)
  : loop_(NULL),
    exiting_(false),
    thread_(boost::bind(&EventLoopThread::threadFunc, this)),
    mutex_(),
    cond_(mutex_),
    callback_(cb)
{
}

EventLoopThread::~EventLoopThread()
{
  exiting_ = true;
  loop_->quit();		// 退出IO线程，让IO线程的loop循环退出，从而退出了IO线程
  thread_.join();
}

EventLoop* EventLoopThread::startLoop()
{
  assert(!thread_.started());
  thread_.start();

  {
    MutexLockGuard lock(mutex_);
    while (loop_ == NULL)
    {
      cond_.wait();
    }
  }

  return loop_;
}

void EventLoopThread::threadFunc()
{
  EventLoop loop;

  if (callback_)
  {
    callback_(&loop);
  }

  {
    MutexLockGuard lock(mutex_);
    // loop_指针指向了一个栈上的对象，threadFunc函数退出之后，这个指针就失效了
    // threadFunc函数退出，就意味着线程退出了，EventLoopThread对象也就没有存在的价值了。
    // 因而不会有什么大的问题
    loop_ = &loop;
    cond_.notify();
  }

  loop.loop();
  //assert(exiting_);
}

3.Reactor_test06.cc

#include 
#include 

#include 

using namespace muduo;
using namespace muduo::net;

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

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

  EventLoopThread loopThread;
  EventLoop* loop = loopThread.startLoop();
  // 异步调用runInThread，即将runInThread添加到loop对象所在IO线程，让该IO线程执行
  loop->runInLoop(runInThread);
  sleep(1);
  // runAfter内部也调用了runInLoop，所以这里也是异步调用
  loop->runAfter(2, runInThread);
  sleep(3);
  loop->quit();

  printf("exit main().\n");
}