muduo_net库源码分析（26-1

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

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 <vector>

#include <boost/noncopyable.hpp>
#include <boost/scoped_ptr.hpp>

#include <muduo/base/CurrentThread.h>
#include <muduo/base/Thread.h>
#include <muduo/base/Timestamp.h>

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<Channel*> 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_; //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<Channel*> ChannelList;
Channel* currentActiveChannel_;   // 当前正在处理的活动通道
};

}
}
#endif  // MUDUO_NET_EVENTLOOP_H

[/code]

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 <muduo/net/EventLoop.h>

#include <muduo/base/Logging.h>
#include <muduo/net/Channel.h>
#include <muduo/net/Poller.h>

//#include <poll.h>

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() << "} ";
}
}

[/code]

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 <vector>
#include <boost/noncopyable.hpp>

#include <muduo/base/Timestamp.h>
#include <muduo/net/EventLoop.h>

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<Channel*> 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

[/code]

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 <muduo/net/Poller.h>

using namespace muduo;
using namespace muduo::net;

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

Poller::~Poller()
{
}

[/code]

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 <muduo/net/Poller.h>

#include <map>
#include <vector>

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

[/code]

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 <muduo/net/poller/PollPoller.h>

#include <muduo/base/Logging.h>
#include <muduo/base/Types.h>
#include <muduo/net/Channel.h>

#include <assert.h>
#include <poll.h>

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();
}
}

[/code]

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 <boost/function.hpp>
#include <boost/noncopyable.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/weak_ptr.hpp>

#include <muduo/base/Timestamp.h>

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

[/code]

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 <muduo/base/Logging.h>
#include <muduo/net/Channel.h>
#include <muduo/net/EventLoop.h>

#include <sstream>

#include <poll.h>

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();
}

[/code]