muduo网络库之EventLoop类

本篇博客针对EventLoop类做下小结。

博客代码来自于陈硕的muduo网络库，github地址https://github.com/chenshuo/muduo

学习笔记：

muduo网络库的线程类遵循one loop per thread。顾名思义每个线程只能有一个EventLoop对象，因此EventLoop独享的构造函数会检查当前线程是否已经创建了其它EventLoop对象，如果已经创建则终止程序。创建了EventLoop的线程就是IO线程，其主要功能是运行时间循环EventLoop::loop()，在该循环中调用Poller::poll()执行阻塞式等待监听事件的响应，执行对应的回调函数。EventLoop对象可以在多线程使用，但是它的某些成员函数只有在EventLoop的创建者线程使用才是线程安全的(避免race-condition)，EventLoop通过将调用函数传入pendingFunctors_，利用wakeupFd_唤醒EventLoop的创建者线程通知它及时执行pendingFunctors_中的函数。

EventLoop.h

#ifndef MUDUO_NET_EVENTLOOP_H
#define MUDUO_NET_EVENTLOOP_H

#include <atomic>
#include <functional>
#include <vector>

#include <boost/any.hpp>

#include "muduo/base/Mutex.h"
#include "muduo/base/CurrentThread.h"
#include "muduo/base/Timestamp.h"
#include "muduo/net/Callbacks.h"
#include "muduo/net/TimerId.h"

namespace muduo
{
namespace net
{

class Channel;
class Poller;
class TimerQueue;

///
/// Reactor, at most one per thread.
///
/// This is an interface class, so don't expose too much details.
class EventLoop : noncopyable
{
 public:
  typedef std::function<void()> Functor;

  EventLoop();
  ~EventLoop();  // force out-line dtor, for std::unique_ptr members.

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

  /// Quits loop.
  ///
  /// This is not 100% thread safe, if you call through a raw pointer,
  /// better to call through shared_ptr<EventLoop> for 100% safety.
  void quit();

  ///
  /// Time when poll returns, usually means data arrival.
  ///
  Timestamp pollReturnTime() const { return pollReturnTime_; }

  int64_t iteration() const { return iteration_; }

  /// Runs callback immediately in the loop thread.
  /// It wakes up the loop, and run the cb.
  /// If in the same loop thread, cb is run within the function.
  /// Safe to call from other threads.
  void runInLoop(Functor cb);
  /// Queues callback in the loop thread.
  /// Runs after finish pooling.
  /// Safe to call from other threads.
  void queueInLoop(Functor cb);

  size_t queueSize() const;

  // timers
  //  以下3个run函数是对定时器的使用
  ///
  /// Runs callback at 'time'.
  /// Safe to call from other threads.
  ///
  TimerId runAt(Timestamp time, TimerCallback cb);
  ///
  /// Runs callback after @