net1. Reactor关键结构——EventLoop事件循环类

muduo的简化类图

时序图：

EventLoop类

1. EventLoop事件循环类，是对事件循环的抽象。
2. one loop per thread意思是说每个线程最多只能有一个EventLoop对象。
3. 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）。
4. EventLoop构造函数会记住本对象所属线程（threadId_）。
5. 创建了EventLoop对象的线程称为IO线程，其功能是通过EventLoop::loop()运行事件循环(while循环)。
6. 一个EventLoop可以有多个Channel和FileDescriptor。
7. EventLoop::loop()主要有四个作用，按顺序处理定时器事件，IO多路复用检测，处理检测返回的活动通道事件，处理自己的额外消息事件

数据成员：

当前是否处于循环状态即是否在loop()函数中
bool looping_：当前是否处于循环状态即是否在loop()函数中 atomic
bool quit_：当前是否退出循环状态即是否退出loop()函数 atomic
bool eventHandling_：当前是否处于事件处理的状态 atomic
bool callingPendingFunctors_：当前是否处于调用pending函数的状态atomic
const pid_t threadId_：当前对象所属线程ID
Timestamp pollReturnTime_：调用poll()函数时所返回的时间戳
boost::scoped_ptr poller_：一个用于I/O复用的Poller对象poller_，调用智能指针，Poller的生存期由EventLoop()来控制
boost::scoped_ptr timerQueue_：指向TimerQueue的timerQueue_
int wakeupFd_：用于eventfd所创建的文件描述符，线程间事件通知
boost::scoped_ptr wakeupChannel_：wakeupFd_所对应的通道，该通道将会纳入poller_来管理
ChannelList activeChannels_：Poller返回的活动通道列表activeChannels_
Channel* currentActiveChannel_：当前正在处理的活动通道
MutexLock mutex_：互斥量mutex_
std::vector pendingFunctors_：该IO线程的任务队列，pending函数集合pendingFunctors_
typedef

typedef std::vector ChannelList

成员函数：

EventLoop()：构造函数，调用Poller::newDefaultPoller(this)初始化poller_对象
~EventLoop()：析构函数
void loop()：事件循环函数loop()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 quit()：事件循环终止函数quit()，可以跨线程调用
Timestamp pollReturnTime() const ：返回时间戳pollReturnTime_
void runInLoop(const Functor& cb)：runInLoop()在I/O线程中执行某个回调函数，该函数可以跨线程调用，loop对象在其他线程中异步调用runInThread，则会调用queueInLoop将cb添加到该loop对象所属的IO线程
void queueInLoop(const Functor& cb)：当调用者并非当前EventLoop所在线程时，将Functor存入EventLoop的任务队列
从而保证Functor由IO线程执行，这是线程安全的保证之一
TimerId runAt(const Timestamp& time, const TimerCallback& cb)：在某个时刻运行定时器
TimerId runAfter(double delay, const TimerCallback& cb)：过一段时间运行定时器
TimerId runEvery(double interval, const TimerCallback& cb)：每隔一段时间运行定时器
void cancel(TimerId timerId)：取消定时器
void wakeup()：唤醒等待的线程
void updateChannel(Channel* channel)：在Poller中添加或者更新通道
void removeChannel(Channel* channel)：从Poller中移除通道
void assertInLoopThread()：断言当前处于创建该对象的线程中
bool isInLoopThread() const ：判断是否处于创建该EventLoop对象的线程
bool eventHandling() const：判断当前是否处于事件处理的状态
static EventLoop* getEventLoopOfCurrentThread()：返回线程局部存储的当前线程指向的EventLoop对象的指针
void abortNotInLoopThread()：终止程序
void handleRead()：wakeupChannel_的ReadCallback()回调函数
void doPendingFunctors()：调用pendingFunctors_里面的所有函数
void printActiveChannels() const：打印活动通道列表activeChannels_里的通道

EventLoop.h

// 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 

#include 
#include 
#include 
#include 
#include 

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 : boost::noncopyable
{
 public:
  typedef boost::function<void()> Functor;

  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();

  void quit();

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

  /// 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(const Functor& cb);
  /// Queues callback in the loop thread.
  /// Runs after finish pooling.
  /// Safe to call from other threads.
  void queueInLoop(const Functor& cb);

  // timers

  ///
  /// Runs callback at 'time'.
  /// Safe to call from other threads.
  ///
  TimerId runAt(const Timestamp& time, const TimerCallback& cb);
  ///
  /// Runs callback after @c delay seconds.
  /// Safe to call from other threads.
  ///
  TimerId runAfter(double delay, const TimerCallback& cb);
  ///
  /// Runs callback every @c interval seconds.
  /// Safe to call from other threads.
  ///
  TimerId runEvery(double interval, const TimerCallback& cb);
  ///
  /// Cancels the timer.
  /// Safe to call from other threads.
  ///
  void cancel(TimerId timerId);

  // internal usage
  void wakeup();
  void updateChannel(Channel* channel);		// 在Poller中添加或者更新通道
  void removeChannel(Channel* channel);		// 从Poller中移除通道

  void assertInLoopThread()
  {
    if (!isInLoopThread())
    {
      abortNotInLoopThread();
    }
  }
  bool isInLoopThread() const { return threadId_ == CurrentThread::tid(); }

  bool eventHandling() const { return eventHandling_; }

  static EventLoop* getEventLoopOfCurrentThread();

 private:
  void abortNotInLoopThread();
  void handleRead();  // waked up
  void doPendingFunctors();

  void printActiveChannels() const; // DEBUG

  typedef std::vector<Channel*> ChannelList;
  
  bool looping_; /* atomic */
  bool quit_; /* atomic */
  bool eventHandling_; /* atomic */
  bool callingPendingFunctors_; /* atomic */
  const pid_t threadId_;		// 当前对象所属线程ID
  Timestamp pollReturnTime_;
  boost::scoped_ptr<Poller> poller_;
  boost::scoped_ptr<TimerQueue> timerQueue_;
  int wakeupFd_;				// 用于eventfd
  // unlike in TimerQueue, which is an internal class,
  // we don't expose Channel to client.
  boost::scoped_ptr<Channel> wakeupChannel_;	// 该通道将会纳入poller_来管理
  ChannelList activeChannels_;		// Poller返回的活动通道
  Channel* currentActiveChannel_;	// 当前正在处理的活动通道
  MutexLock mutex_;
  std::vector<Functor> pendingFunctors_; // @BuardedBy mutex_
};

}
}
#endif  // MUDUO_NET_EVENTLOOP_H

EventLoop.cc

#include 

#include 
#include 
#include 
#include 

//#include 
#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
__thread EventLoop* t_loopInThisThread = 0;

const int kPollTimeMs = 10000;

int createEventfd()
{
  int evtfd = ::eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
  if (evtfd < 0)
  {
    LOG_SYSERR << "Failed in eventfd";
    abort();
  }
  return evtfd;
}

#pragma GCC diagnostic ignored "-Wold-style-cast"
class IgnoreSigPipe
{
 public:
  IgnoreSigPipe()
  {
    ::signal(SIGPIPE, SIG_IGN);
    LOG_TRACE << "Ignore SIGPIPE";
  }
};
#pragma GCC diagnostic error "-Wold-style-cast"

IgnoreSigPipe initObj;
}

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

EventLoop::EventLoop()
  : looping_(false),
    quit_(false),
    eventHandling_(false),
    callingPendingFunctors_(false),
    threadId_(CurrentThread::tid()),
    poller_(Poller::newDefaultPoller(this)),
    timerQueue_(new TimerQueue(this)),
    wakeupFd_(createEventfd()),
    wakeupChannel_(new Channel(this, wakeupFd_)),
    currentActiveChannel_(NULL)
{
  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)
  if (t_loopInThisThread)
  {
    LOG_FATAL << "Another EventLoop " << t_loopInThisThread
              << " exists in this thread " << threadId_;
  }
  else
  {
    t_loopInThisThread = this;
  }
  wakeupChannel_->setReadCallback(
      boost::bind(&EventLoop::handleRead, this));
  // we are always reading the wakeupfd
  wakeupChannel_->enableReading();
}

EventLoop::~EventLoop()
{
  ::close(wakeupFd_);
  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()
{
  assert(!looping_);
  // 断言当前处于创建该对象的线程中
  assertInLoopThread();
  looping_ = true;
  quit_ = false;
  LOG_TRACE << "EventLoop " << this << " start looping";

  //::poll(NULL, 0, 5*1000);
  while (!quit_)
  {
    activeChannels_.clear();
    pollReturnTime_ = poller_->poll(kPollTimeMs, &activeChannels_);
    //++iteration_;
    if (Logger::logLevel() <= Logger::TRACE)
    {
      printActiveChannels();
    }
    // TODO sort channel by priority
    eventHandling_ = true;
    for (ChannelList::iterator it = activeChannels_.begin();
        it != activeChannels_.end(); ++it)
    {
      currentActiveChannel_ = *it;
      currentActiveChannel_->handleEvent(pollReturnTime_);
    }
    currentActiveChannel_ = NULL;
    eventHandling_ = false;
    doPendingFunctors();
  }

  LOG_TRACE << "EventLoop " << this << " stop looping";
  looping_ = false;
}

// 该函数可以跨线程调用
void EventLoop::quit()
{
  quit_ = true;
  if (!isInLoopThread())
  {
    wakeup();
  }
}

// 在I/O线程中执行某个回调函数，该函数可以跨线程调用
void EventLoop::runInLoop(const Functor& cb)
{
  if (isInLoopThread())
  {
    // 如果是当前IO线程调用runInLoop，则同步调用cb
    cb();
  }
  else
  {
    // 如果是其它线程调用runInLoop，则异步地将cb添加到队列
    queueInLoop(cb);
  }
}

void EventLoop::queueInLoop(const Functor& cb)
{
  {
  MutexLockGuard lock(mutex_);
  pendingFunctors_.push_back(cb);
  }

  // 调用queueInLoop的线程不是IO线程需要唤醒
  // 或者调用queueInLoop的线程是IO线程，并且此时正在调用pending functor，需要唤醒
  // 只有IO线程的事件回调中调用queueInLoop才不需要唤醒
  if (!isInLoopThread() || callingPendingFunctors_)
  {
    wakeup();
  }
}

TimerId EventLoop::runAt(const Timestamp& time, const TimerCallback& cb)
{
  return timerQueue_->addTimer(cb, time, 0.0);
}

TimerId EventLoop::runAfter(double delay, const TimerCallback& cb)
{
  Timestamp time(addTime(Timestamp::now(), delay));
  return runAt(time, cb);
}

TimerId EventLoop::runEvery(double interval, const TimerCallback& cb)
{
  Timestamp time(addTime(Timestamp::now(), interval));
  return timerQueue_->addTimer(cb, time, interval);
}

void EventLoop::cancel(TimerId timerId)
{
  return timerQueue_->cancel(timerId);
}

void EventLoop::updateChannel(Channel* channel)
{
  assert(channel->ownerLoop() == this);
  assertInLoopThread();
  poller_->updateChannel(channel);
}

void EventLoop::removeChannel(Channel* channel)
{
  assert(channel->ownerLoop() == this);
  assertInLoopThread();
  if (eventHandling_)
  {
    assert(currentActiveChannel_ == channel ||
        std::find(activeChannels_.begin(), activeChannels_.end(), channel) == activeChannels_.end());
  }
  poller_->removeChannel(channel);
}

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

void EventLoop::wakeup()
{
  uint64_t one = 1;
  //ssize_t n = sockets::write(wakeupFd_, &one, sizeof one);
  ssize_t n = ::write(wakeupFd_, &one, sizeof one);
  if (n != sizeof one)
  {
    LOG_ERROR << "EventLoop::wakeup() writes " << n << " bytes instead of 8";
  }
}

void EventLoop::handleRead()
{
  uint64_t one = 1;
  //ssize_t n = sockets::read(wakeupFd_, &one, sizeof one);
  ssize_t n = ::read(wakeupFd_, &one, sizeof one);
  if (n != sizeof one)
  {
    LOG_ERROR << "EventLoop::handleRead() reads " << n << " bytes instead of 8";
  }
}

void EventLoop::doPendingFunctors()
{
  std::vector<Functor> functors;
  callingPendingFunctors_ = true;

  {
  MutexLockGuard lock(mutex_);
  functors.swap(pendingFunctors_);
  }

  for (size_t i = 0; i < functors.size(); ++i)
  {
    functors[i]();
  }
  callingPendingFunctors_ = false;
}

void EventLoop::printActiveChannels() const
{
  for (ChannelList::const_iterator it = activeChannels_.begin();
      it != activeChannels_.end(); ++it)
  {
    const Channel* ch = *it;
    LOG_TRACE << "{" << ch->reventsToString() << "} ";
  }
}