EpollPoller --- muduo_net库源码分析（27）

EpollPoller的头文件

// 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_EPOLLPOLLER_H
#define MUDUO_NET_POLLER_EPOLLPOLLER_H

#include <muduo/net/Poller.h>

#include <map>
#include <vector>

struct epoll_event;

namespace muduo
{
namespace net
{

///
/// IO Multiplexing with epoll(4).
///
class EPollPoller : public Poller
{
public:
EPollPoller(EventLoop* loop);
virtual ~EPollPoller();
// timeoutMs 超时事件
// activeChannels活动通道
virtual Timestamp poll(int timeoutMs, ChannelList* activeChannels);
//更新通道
virtual void updateChannel(Channel* channel);
//移除通道
virtual void removeChannel(Channel* channel);

private:
// EventListd的初始值
static const int kInitEventListSize = 16;

void fillActiveChannels(int numEvents,
ChannelList* activeChannels) const;
//更新
void update(int operation, Channel* channel);

typedef std::vector<struct epoll_event> EventList;

typedef std::map<int, Channel*> ChannelMap;

//文件描述符 = epoll_create1(EPOLL_CLOEXEC)，用来表示要关注事件的fd的集合的描述符
int epollfd_;
// epoll_wait返回的活动的通道channelList
EventList events_;
//通道map
ChannelMap channels_;
};

}
}
#endif  // MUDUO_NET_POLLER_EPOLLPOLLER_H

EpollPoller的源文件

// 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/EPollPoller.h>

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

#include <boost/static_assert.hpp>

#include <assert.h>
#include <errno.h>
#include <poll.h>
#include <sys/epoll.h>

using namespace muduo;
using namespace muduo::net;

// On Linux, the constants of poll(2) and epoll(4)
// are expected to be the same.
BOOST_STATIC_ASSERT(EPOLLIN == POLLIN);
BOOST_STATIC_ASSERT(EPOLLPRI == POLLPRI);
BOOST_STATIC_ASSERT(EPOLLOUT == POLLOUT);
BOOST_STATIC_ASSERT(EPOLLRDHUP == POLLRDHUP);
BOOST_STATIC_ASSERT(EPOLLERR == POLLERR);
BOOST_STATIC_ASSERT(EPOLLHUP == POLLHUP);

namespace
{
const int kNew = -1; //新通道
const int kAdded = 1; //要关注的通道
const int kDeleted = 2; //要删除的通道
}

EPollPoller::EPollPoller(EventLoop* loop)
: Poller(loop),
epollfd_(::epoll_create1(EPOLL_CLOEXEC)),
events_(kInitEventListSize)
{
if (epollfd_ < 0)
{
LOG_SYSFATAL << "EPollPoller::EPollPoller";
}
}

EPollPoller::~EPollPoller()
{
::close(epollfd_);
}

// IO 线程
Timestamp EPollPoller::poll(int timeoutMs, ChannelList* activeChannels)
{
//监听事件的到来
int numEvents = ::epoll_wait(epollfd_,
&*events_.begin(),
static_cast<int>(events_.size()),
timeoutMs);

Timestamp now(Timestamp::now());
if (numEvents > 0)
{
LOG_TRACE << numEvents << " events happended";
/*添加活动通道channel*/
fillActiveChannels(numEvents, activeChannels);
//如果活动通道的容器已满，则增加活动通道容器的容量
if (implicit_cast<size_t>(numEvents) == events_.size())
{
events_.resize(events_.size()*2);
}
}
else if (numEvents == 0)
{
LOG_TRACE << " nothing happended";
}
else
{
LOG_SYSERR << "EPollPoller::poll()";
}
return now;
}

/*添加活动通道channel*/
void EPollPoller::fillActiveChannels(int numEvents,
ChannelList* activeChannels) const
{
assert(implicit_cast<size_t>(numEvents) <= events_.size());
for (int i = 0; i < numEvents; ++i)
{
Channel* channel = static_cast<Channel*>(events_[i].data.ptr);
//如果是调试状态，则
#ifndef NDEBUG
int fd = channel->fd();
ChannelMap::const_iterator it = channels_.find(fd);
assert(it != channels_.end());
assert(it->second == channel);
#endif
//否则直接跳到这里
// 设置channel的“可用事件”
channel->set_revents(events_[i].events);
// 加入活动通道容器
activeChannels->push_back(channel);
}
}

//更新某个通道 channel
void EPollPoller::updateChannel(Channel* channel)
{
//断言 在IO线程中
Poller::assertInLoopThread();
LOG_TRACE << "fd = " << channel->fd() << " events = " << channel->events();

//channel 的默认值是 -1 ， ---->>channel class
const int index = channel->index();
// kNew 表示有新的通道要增加，kDeleted表示将已不关注事件的fd重新关注事件，及时重新加到epollfd_中去
if (index == kNew || index == kDeleted)
{
// a new one, add with EPOLL_CTL_ADD
int fd = channel->fd();
if (index == kNew)
{
//如果是新的channel，那么在channels_里面是找不到的
assert(channels_.find(fd) == channels_.end());
//添加到channels_中
channels_[fd] = channel;
}

else // index == kDeleted
{
assert(channels_.find(fd) != channels_.end());
assert(channels_[fd] == channel);
}
//
channel->set_index(kAdded);
update(EPOLL_CTL_ADD, channel);
}
else
{
// update existing one with EPOLL_CTL_MOD/DEL
int fd = channel->fd();
(void)fd;
assert(channels_.find(fd) != channels_.end());
assert(channels_[fd] == channel);
//断言已经在channels_里面了，并且已在epollfd_中
assert(index == kAdded);

//剔除channel的关注事件
//如果channel没有事件关注了，就把他从epollfd_中剔除掉
if (channel->isNoneEvent())
{
update(EPOLL_CTL_DEL, channel);
//更新index = kDeleted
channel->set_index(kDeleted);
}
else
{
update(EPOLL_CTL_MOD, channel);
}
}
}

// 移除channel
void EPollPoller::removeChannel(Channel* channel)
{
//断言实在IO线程中
Poller::assertInLoopThread();
int fd = channel->fd();
LOG_TRACE << "fd = " << fd;
//断言能在channels_里面找到channel
assert(channels_.find(fd) != channels_.end());
assert(channels_[fd] == channel);
//断言所要移除的channel已经没有事件关注了，但是此时在event_里面可能还有他的记录
assert(channel->isNoneEvent());
int index = channel->index();
//断言
assert(index == kAdded || index == kDeleted);
//真正从channels_里面删除掉channel
size_t n = channels_.erase(fd);
(void)n;
assert(n == 1);

//从event_中剔除channel
if (index == kAdded)
{
update(EPOLL_CTL_DEL, channel);
}

// channel现在变成新的channel了
channel->set_index(kNew);
}

void EPollPoller::update(int operation, Channel* channel)
{
struct epoll_event event;
bzero(&event, sizeof event);
event.events = channel->events();
event.data.ptr = channel;
int fd = channel->fd();
//更新操作
if (::epoll_ctl(epollfd_, operation, fd, &event) < 0)
{
//写入日志
if (operation == EPOLL_CTL_DEL)
{
LOG_SYSERR << "epoll_ctl op=" << operation << " fd=" << fd;
}
else
{
LOG_SYSFATAL << "epoll_ctl op=" << operation << " fd=" << fd;
}
}
}

测试程序

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

#include <boost/bind.hpp>

#include <stdio.h>
#include <sys/timerfd.h>

using namespace muduo;
using namespace muduo::net;

EventLoop* g_loop;
int timerfd;

void timeout(Timestamp receiveTime)
{
printf("Timeout!\n");
uint64_t howmany;
::read(timerfd, &howmany, sizeof howmany);
g_loop->quit();
}

int main(void)
{
EventLoop loop;
g_loop = &loop;

timerfd = ::timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK | TFD_CLOEXEC);
Channel channel(&loop, timerfd);
channel.setReadCallback(boost::bind(timeout, _1));
channel.enableReading();

struct itimerspec howlong;
bzero(&howlong, sizeof howlong);
howlong.it_value.tv_sec = 1;
::timerfd_settime(timerfd, 0, &howlong, NULL);

loop.loop();

::close(timerfd);
}

[root@localhost bin]# ./reactor_test03
20131020 02:24:05.657327Z  4009 TRACE EventLoop EventLoop created 0xBFD2AAD4 in thread 4009 - EventLoop.cc:42
20131020 02:24:05.657513Z  4009 TRACE updateChannel fd = 4 events = 3 - EPollPoller.cc:104
20131020 02:24:05.657554Z  4009 TRACE loop EventLoop 0xBFD2AAD4 start looping - EventLoop.cc:68
20131020 02:24:06.658756Z  4009 TRACE poll 1 events happended - EPollPoller.cc:65
20131020 02:24:06.658972Z  4009 TRACE printActiveChannels {4: IN }  - EventLoop.cc:139
Timeout!
20131020 02:24:06.659008Z  4009 TRACE loop EventLoop 0xBFD2AAD4 stop looping - EventLoop.cc:93
[root@localhost bin]#