muduo_net库源码分析

• Channel是selectable IO channel，负责注册与响应IO 事件，它不拥有file descriptor。

• Channel是Acceptor、Connector、EventLoop、TimerQueue、TcpConnection的成员，生命期由后者控制。

  
  

  
  

时序图

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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

#include
#include
#include

namespace muduo
{
namespace net
{

class Channel; //聚合
class Poller; //组合
///
/// 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();

  void quit();

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

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

  /*断言是否在Loop 线程中*/
  void assertInLoopThread()
  {
      //如果不是在LoopThread中，终止程序
    if (!isInLoopThread())
    {
      abortNotInLoopThread();
    }
  }
  //判断是在当前线程是否在LoopThread中
  bool isInLoopThread() const { return threadId_ == CurrentThread::tid(); }

  static EventLoop* getEventLoopOfCurrentThread();

 private:
  void abortNotInLoopThread();

  void printActiveChannels() const; // DEBUG

  typedef std::vector ChannelList;

  bool looping_; /*是否处于循环状态 atomic */
  bool quit_; /*是否退出Loop atomic */
  bool eventHandling_; /*当前是否处于事件处理的状态 atomic */
  const pid_t threadId_;        // 当前对象所属线程ID
  Timestamp pollReturnTime_;    //调用poller时候的返回时间
  boost::scoped_ptr poller_; //poller对象，生命周期由EventLoop控制
  ChannelList activeChannels_;  // Poller返回的活动通道 ，
                                //就是活动状态的socket///typedef std::vector ChannelList;
  Channel* currentActiveChannel_;   // 当前正在处理的活动通道
};

}
}
#endif  // MUDUO_NET_EVENTLOOP_H

EventLoop源文件

EventLoop.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
#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;
}

EventLoop* EventLoop::getEventLoopOfCurrentThread()
{
  return t_loopInThisThread;
}
/*
事件循环，该函数不能夸线程调用
只能在创建该对象的线程中调用
**/

EventLoop::EventLoop()
  : looping_(false),
    quit_(false),
    eventHandling_(false),
    threadId_(CurrentThread::tid()),
    poller_(Poller::newDefaultPoller(this)),
    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_;
  }
  //如果当前线程没有创建EventLoop对象，则创建EventLoop对象，并且进行绑定
  else
  {
    t_loopInThisThread = this;
  }
}

EventLoop::~EventLoop()
{
  t_loopInThisThread = NULL;
}
 //这是IO线程
// 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()
{
//断言是否处于非循环状态
  assert(!looping_);
  // 断言当前处于创建该对象的线程中
  assertInLoopThread();
  looping_ = true;
  LOG_TRACE << "EventLoop " << this << " start looping";

  //::poll(NULL, 0, 5*1000);
  //循环直到退出
  while (!quit_)
  {
  //先清除活动通道
    activeChannels_.clear();
    //调用poller_->poll返回活动的通道 &activeChannels_以及poll返回的时间
    pollReturnTime_ = poller_->poll(kPollTimeMs, &activeChannels_);
    //++iteration_;
    //输出 处于活动状态的channel 到日志中
    if (Logger::logLevel() <= Logger::TRACE)
    {
      printActiveChannels();
    }
    // TODO sort channel by priority
    //当前事件处理状态设为true
    eventHandling_ = true;
    //循环处理活动通道的事件
    for (ChannelList::iterator it = activeChannels_.begin();
        it != activeChannels_.end(); ++it)
    {
      currentActiveChannel_ = *it;
      currentActiveChannel_->handleEvent(pollReturnTime_);
    }
    //把当前的活动通道设为 NULL
    currentActiveChannel_ = NULL;
    //当前事件处理状态设为false
    eventHandling_ = false;
    //doPendingFunctors();
  }

  LOG_TRACE << "EventLoop " << this << " stop looping";
  looping_ = false;
}
 //该函数可以跨线程调用，这也是防止程序
void EventLoop::quit()
{
  quit_ = true; //由于是多线程访问这个变量，那么是否需要保护这个变量？？，要的。但是quit_是布尔类型，是一种对布尔类型的变量操作是一种原子操作，所以我们不用显式的进行保护了
  if (!isInLoopThread())
  {
    //wakeup();
  }
}

// 用于注册或者更新 channel的事件
void EventLoop::updateChannel(Channel* channel)
{
  // 断言Channel 是否属于当前的EventLoop对象
  assert(channel->ownerLoop() == this);
  // 断言EventLoop所属的线程是当前的线程
  assertInLoopThread();
  // 更新channel的事件
  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);
}

//如果不是在LoopThread线程中将终止线程
void EventLoop::abortNotInLoopThread()
{
  LOG_FATAL << "EventLoop::abortNotInLoopThread - EventLoop " << this
            << " was created in threadId_ = " << threadId_
            << ", current thread id = " <<  CurrentThread::tid();
}

/*打印处于活动状态的channel 到日志中*/
void EventLoop::printActiveChannels() const
{
  for (ChannelList::const_iterator it = activeChannels_.begin();
      it != activeChannels_.end(); ++it)
  {
    const Channel* ch = *it;
    LOG_TRACE << "{" << ch->reventsToString() << "} ";
  }
}

---

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Poller头文件

poller.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 an internal header file, you should not include this.

#ifndef MUDUO_NET_POLLER_H
#define MUDUO_NET_POLLER_H

#include
#include

#include
#include

namespace muduo
{
namespace net
{

class Channel;

///
/// Base class for IO Multiplexing
///
/// This class doesn't own the Channel objects.
class Poller : boost::noncopyable
{
 public:
  typedef std::vector ChannelList;

  Poller(EventLoop* loop);
  virtual ~Poller();

  /// Polls the I/O events.
  /// Must be called in the loop thread.
  virtual Timestamp poll(int timeoutMs, ChannelList* activeChannels) = 0;

  /// Changes the interested I/O events.
  /// Must be called in the loop thread.
  virtual void updateChannel(Channel* channel) = 0;

  /// Remove the channel, when it destructs.
  /// Must be called in the loop thread.
  virtual void removeChannel(Channel* channel) = 0;

  static Poller* newDefaultPoller(EventLoop* loop);

  void assertInLoopThread()
  {
    ownerLoop_->assertInLoopThread();
  }

 private:
  EventLoop* ownerLoop_;    // Poller所属EventLoop
};

}
}
#endif  // MUDUO_NET_POLLER_H

Poller源文件

poller.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

using namespace muduo;
using namespace muduo::net;

Poller::Poller(EventLoop* loop)
  : ownerLoop_(loop)
{
}

Poller::~Poller()
{
}

---

---

PollPoller头文件

pollpoller.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 an internal header file, you should not include this.

#ifndef MUDUO_NET_POLLER_POLLPOLLER_H
#define MUDUO_NET_POLLER_POLLPOLLER_H

#include

#include
#include

struct pollfd;

namespace muduo
{
namespace net
{

///
/// IO Multiplexing with poll(2).
///
class PollPoller : public Poller
{
 public:

  PollPoller(EventLoop* loop);
  virtual ~PollPoller();

  /*返回活动的通道列表*/
  virtual Timestamp poll(int timeoutMs, ChannelList* activeChannels);
  virtual void updateChannel(Channel* channel);
  virtual void removeChannel(Channel* channel);

 private:
  void fillActiveChannels(int numEvents,
                          ChannelList* activeChannels) const;

  typedef std::vector<struct pollfd> PollFdList;
  typedef std::map<int, Channel*> ChannelMap; // key是文件描述符，value是Channel*
  PollFdList pollfds_; // 事件结构
  /*被关注的通道列表 ， 不是活动的通道列表*/
  ChannelMap channels_;
};

}
}
#endif  // MUDUO_NET_POLLER_POLLPOLLER_H

PollPoller源文件

pollpoller.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
#include

#include
#include

using namespace muduo;
using namespace muduo::net;

PollPoller::PollPoller(EventLoop* loop)
  : Poller(loop)
{
}

PollPoller::~PollPoller()
{
}

/*
真正的poll 函数，终于到主角了^<>^  ///
**/
Timestamp PollPoller::poll(int timeoutMs, ChannelList* activeChannels)
{
  // XXX pollfds_ shouldn't change
  int numEvents = ::poll(&*pollfds_.begin(), pollfds_.size(), timeoutMs);
  Timestamp now(Timestamp::now());
  //如果有活动事件 ， 则填充到activeChannels 中去
  if (numEvents > 0)
  {
    LOG_TRACE << numEvents << " events happended";
    fillActiveChannels(numEvents, activeChannels);
  }
  else if (numEvents == 0)
  {
    LOG_TRACE << " nothing happended";
  }
  else
  {
    LOG_SYSERR << "PollPoller::poll()";
  }
  return now;
}

//填充活动通道
// activeChannels 活动通道
// pollfds_       已注册的事件集合
/*被关注的通道列表 ， 不是活动的通道列表*/
void PollPoller::fillActiveChannels(int numEvents,
                                    ChannelList* activeChannels) const
{
  for (PollFdList::const_iterator pfd = pollfds_.begin();
      pfd != pollfds_.end() && numEvents > 0; ++pfd)
  {
    //返回活动的文件描述符
    if (pfd->revents > 0)
    {
      --numEvents;
      // 从关注列表channels_中找出 已产生事件 的fd---》channel
      ChannelMap::const_iterator ch = channels_.find(pfd->fd);
      // 断言是否已近到了channels_的尾部
      assert(ch != channels_.end());
      // 获取活动channel
      Channel* channel = ch->second;
      // 断言channel的文件描述符是否和pfd 的描述符一致
      assert(channel->fd() == pfd->fd);
      // 设置channel的事件
      channel->set_revents(pfd->revents);
      // pfd->revents = 0;
      // 把活动channel 加入activeChannel容器
      activeChannels->push_back(channel);
    }
  }
}

/*
更行channel通道，
**/
void PollPoller::updateChannel(Channel* channel)
{
  //断言实在LoopThread 当中
  Poller::assertInLoopThread();
  LOG_TRACE << "fd = " << channel->fd() << " events = " << channel->events();
  //如果新的通道，还没有注册事件
  if (channel->index() < 0)
  {
    // index < 0说明是一个新的通道
    // a new one, add to pollfds_
    //断言是新的通道
    assert(channels_.find(channel->fd()) == channels_.end());

    //注册事件
    struct pollfd pfd;
    pfd.fd = channel->fd();
    pfd.events = static_cast<short>(channel->events());
    pfd.revents = 0;
    pollfds_.push_back(pfd);
    //channel在pollfds中索引
    int idx = static_cast<int>(pollfds_.size())-1;
    //更新channel的索引
    channel->set_index(idx);
    //加入channels_ 的map中
    channels_[pfd.fd] = channel;
  }
  else
  {
    // update existing one
    //断言channel 已存在--》 channels_ ,index >0 < pollfds_.size()
    assert(channels_.find(channel->fd()) != channels_.end());
    assert(channels_[channel->fd()] == channel);
    int idx = channel->index();
    assert(0 <= idx && idx < static_cast<int>(pollfds_.size()));
    struct pollfd& pfd = pollfds_[idx];

    assert(pfd.fd == channel->fd() || pfd.fd == -channel->fd()-1);

    //下面才是真正的更新
    pfd.events = static_cast<short>(channel->events());
    //revents 貌似不用清零？？？
    pfd.revents = 0;
    // 将一个通道暂时更改为不关注事件，但不从Poller中移除该通道
    if (channel->isNoneEvent())
    {
      // ignore this pollfd
      // 暂时忽略该文件描述符的事件
      // 这里pfd.fd 可以直接设置为-1 ， -1是为了排除0描述符的干扰
      pfd.fd = -channel->fd()-1; // 这样子设置是为了removeChannel优化
    }
  }
}

// 把channel 真正的从pollfds 中移除
void PollPoller::removeChannel(Channel* channel)
{
  Poller::assertInLoopThread();
  LOG_TRACE << "fd = " << channel->fd();
  assert(channels_.find(channel->fd()) != channels_.end());
  assert(channels_[channel->fd()] == channel);
  //要移除的channel一定是没有关注事件了
  assert(channel->isNoneEvent());
  int idx = channel->index();
  assert(0 <= idx && idx < static_cast<int>(pollfds_.size()));
  const struct pollfd& pfd = pollfds_[idx]; (void)pfd;

  assert(pfd.fd == -channel->fd()-1 && pfd.events == channel->events());

  //1-----------》先把channel 从channels_中移除
  size_t n = channels_.erase(channel->fd());
  assert(n == 1); (void)n;
  //2-----------》如果是最后一个，则直接移除
  if (implicit_cast<size_t>(idx) == pollfds_.size()-1)
  {
    pollfds_.pop_back();
  }
  else
  {
    // 2----------》这里移除的算法复杂度是O(1)，将待删除元素与最后一个元素交换再pop_back
    int channelAtEnd = pollfds_.back().fd;
    iter_swap(pollfds_.begin()+idx, pollfds_.end()-1);

    //channelAtEnd 是从 pollfds_ 里面拿出来的，所以可能是负数
    if (channelAtEnd < 0)
    {
      channelAtEnd = -channelAtEnd-1;
    }
    channels_[channelAtEnd]->set_index(idx);
    pollfds_.pop_back();
  }
}

---

---

Channel头文件

channel.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 an internal header file, you should not include this.

#ifndef MUDUO_NET_CHANNEL_H
#define MUDUO_NET_CHANNEL_H

#include
#include
#include
#include

#include

namespace muduo
{
namespace net
{

class EventLoop;

///
/// A selectable I/O channel.
///
/// This class doesn't own the file descriptor.
/// The file descriptor could be a socket,
/// an eventfd, a timerfd, or a signalfd
class Channel : boost::noncopyable //不可拷贝的
{
 public:
  /*事件回调处理函数*/
  typedef boost::function<void()> EventCallback;
  /*读事件的回调处理*/
  typedef boost::function<void(Timestamp)> ReadEventCallback;
  /*一个EventLoop 包含多个Channel ， 一个channel只属于一个EventLoop
  Channel（n）-----> EventLoop
  */
  Channel(EventLoop* loop, int fd);
  //虚构函数没干什么事^V^
  ~Channel();

  void handleEvent(Timestamp receiveTime);

  /*回调函数的注册*/
  // 读的回调函数
  void setReadCallback(const ReadEventCallback& cb)
  { readCallback_ = cb; }
  // 写的回调函数
  void setWriteCallback(const EventCallback& cb)
  { writeCallback_ = cb; }
  // 关闭的回调函数
  void setCloseCallback(const EventCallback& cb)
  { closeCallback_ = cb; }
  // 出错的回调函数
  void setErrorCallback(const EventCallback& cb)
  { errorCallback_ = cb; }
//

  /*
这个函数下一节才开始分析^V^ ...
这个函数跟TcpConnection 生命周期是有关系的，为了防止在事件处理的时候
  **/
  /// Tie this channel to the owner object managed by shared_ptr,
  /// prevent the owner object being destroyed in handleEvent.
  void tie(const boost::shared_ptr<void>&);

  //channel 的描述符
  int fd() const { return fd_; }
  // channel注册的事件（关注的事件）
  int events() const { return events_; }

  // poller 实际返回的事件，
  void set_revents(int revt) { revents_ = revt; } // used by pollers

  //清空channel的事件
  // int revents() const { return revents_; }
  bool isNoneEvent() const { return events_ == kNoneEvent; }

  void enableReading() { events_ |= kReadEvent; update(); }
  // void disableReading() { events_ &= ~kReadEvent; update(); }
  void enableWriting() { events_ |= kWriteEvent; update(); }
  void disableWriting() { events_ &= ~kWriteEvent; update(); }
  void disableAll() { events_ = kNoneEvent; update(); }
  bool isWriting() const { return events_ & kWriteEvent; }

  // for Poller ； 在Poller数组中的索引
  int index() { return index_; }
  // 设置channel在poller的索引
  void set_index(int idx) { index_ = idx; }

  // for debug 事件的调试信息
  string reventsToString() const;

  void doNotLogHup() { logHup_ = false; }

  EventLoop* ownerLoop() { return loop_; }
  void remove();

 private:
  void update();
  void handleEventWithGuard(Timestamp receiveTime);

  //事件常量
  //没有事件就是说等于零
  static const int kNoneEvent;
  static const int kReadEvent;
  static const int kWriteEvent;

  EventLoop* loop_;         // 所属EventLoop
  const int  fd_;           // 文件描述符，但不负责关闭该文件描述符
  int        events_;       // 关注的事件
  int        revents_;      // poll/epoll返回的事件
  int        index_;        // used by Poller.表示在poll的事件数组中的序号
  bool       logHup_;       // for POLLHUP

  // 下面两个是负责生存期的控制
  boost::weak_ptr<void> tie_;
  bool tied_;


  bool eventHandling_;      // 是否处于处理事件中
  ReadEventCallback readCallback_;
  EventCallback writeCallback_;
  EventCallback closeCallback_;
  EventCallback errorCallback_;
};

}
}
#endif  // MUDUO_NET_CHANNEL_H

Channel源文件

channel.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

#include

#include

using namespace muduo;
using namespace muduo::net;

const int Channel::kNoneEvent = 0; //没有事件
const int Channel::kReadEvent = POLLIN | POLLPRI; //产生量可读事件或者紧急数据
const int Channel::kWriteEvent = POLLOUT;

Channel::Channel(EventLoop* loop, int fd__)
  : loop_(loop),
    fd_(fd__),
    events_(0),
    revents_(0),
    index_(-1),  //没加入poller是，channel的索引为 -1
    logHup_(true),
    tied_(false),
    eventHandling_(false)   //channel的事件处理状态初始化为 false
{
}

Channel::~Channel()
{
  assert(!eventHandling_);
}

void Channel::tie(const boost::shared_ptr<void>& obj)
{
  tie_ = obj;
  tied_ = true;
}

//更新channel的事件
void Channel::update()
{
  loop_->updateChannel(this);
}

// 调用这个函数之前确保调用disableAll
//  void disableAll() { events_ = kNoneEvent; update()-->assert(isNoneEvent()); }
void Channel::remove()
{
  assert(isNoneEvent());
  loop_->removeChannel(this);
}
/**
  当时到达时，调用事件处理函数handleEvent进行处理
*/
void Channel::handleEvent(Timestamp receiveTime)
{
  boost::shared_ptr<void> guard;
  if (tied_)
  {
    guard = tie_.lock();
    if (guard)
    {
      handleEventWithGuard(receiveTime);
    }
  }
  else
  {
    handleEventWithGuard(receiveTime);
  }
}

/**
 事件处理
**/
void Channel::handleEventWithGuard(Timestamp receiveTime)
{//把channel的事件处理状态设为 true
  eventHandling_ = true;
  //如果poller返回的channel 事件是pollhup挂断（写时才会产生），并且不是可读的
  if ((revents_ & POLLHUP) && !(revents_ & POLLIN))
  {
    // 如果挂断了
    if (logHup_)
    {
      LOG_WARN << "Channel::handle_event() POLLHUP";
    }
    //如果挂断了，就返回closeCallback
    if (closeCallback_) closeCallback_();
  }

  //文件描述符不合法或者文件描述符没有打开
  if (revents_ & POLLNVAL)
  {
    LOG_WARN << "Channel::handle_event() POLLNVAL";
  }

  if (revents_ & (POLLERR | POLLNVAL))
  {
    if (errorCallback_) errorCallback_();
  }
  //可读事件 ，
  //POLLRDHUP :stream socket peer closed connection ，or shutdown writing half of connection
  //POLLPRI : there is urgent data to read
  if (revents_ & (POLLIN | POLLPRI | POLLRDHUP))
  {
    if (readCallback_) readCallback_(receiveTime);
  }
  //可写事件
  if (revents_ & POLLOUT)
  {
    if (writeCallback_) writeCallback_();
  }
  //事件处理完后，把事件处理状态恢复为false状态
  eventHandling_ = false;
}

string Channel::reventsToString() const
{
  std::ostringstream oss;
  oss << fd_ << ": ";
  if (revents_ & POLLIN)
    oss << "IN ";
  if (revents_ & POLLPRI)
    oss << "PRI ";
  if (revents_ & POLLOUT)
    oss << "OUT ";
  if (revents_ & POLLHUP)
    oss << "HUP ";
  if (revents_ & POLLRDHUP)
    oss << "RDHUP ";
  if (revents_ & POLLERR)
    oss << "ERR ";
  if (revents_ & POLLNVAL)
    oss << "NVAL ";

  return oss.str().c_str();
}