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poller是I/O多路复用接口抽象虚基类,对I/O多路复用API的封装,muduo提供了EPollPoller和PollPoller派生类(epoll和poll),所以不支持select.
newDefaultPoller()默认选择epoll
主要接口
poll
是Poller的核心功能#xff0c;使用派生类的poll或者epoll_wait来阻塞等待I…简介
poller是I/O多路复用接口抽象虚基类,对I/O多路复用API的封装,muduo提供了EPollPoller和PollPoller派生类(epoll和poll),所以不支持select.
newDefaultPoller()默认选择epoll
主要接口
poll
是Poller的核心功能使用派生类的poll或者epoll_wait来阻塞等待IO事件发生 通过派生类的实现来填充EventLoop的activeChannelList_
static createNewPoller
工厂函数创建一个Poller实例 在EpollPoller中每个实例对应一个epollfd
update
更新I/O多路复用的状态例如epoll_ctl的ADDMODDEL
主要成员
loop
控制当前Poller的EventLoop指针 其余成员由派生类实现
源码剖析
poller.h
#ifndef MUDUO_NET_POLLER_H
#define MUDUO_NET_POLLER_H#include map
#include vector#include muduo/base/Timestamp.h
#include muduo/net/EventLoop.hnamespace muduo
{
namespace net
{class Channel;///
/// Base class for IO Multiplexing
///
/// This class doesnt own the Channel objects.
class Poller : noncopyable
{public:typedef std::vectorChannel* 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;//判断是否存在virtual bool hasChannel(Channel* channel) const;//创建一个poller,默认是epollstatic Poller* newDefaultPoller(EventLoop* loop);void assertInLoopThread() const{ownerLoop_-assertInLoopThread();}protected:typedef std::mapint, Channel* ChannelMap;ChannelMap channels_;private:EventLoop* ownerLoop_;
};} // namespace net
} // namespace muduo#endif // MUDUO_NET_POLLER_H
poller.cc
#include muduo/net/Poller.h
#include muduo/net/Channel.husing namespace muduo;
using namespace muduo::net;Poller::Poller(EventLoop* loop): ownerLoop_(loop)
{
}Poller::~Poller() default;bool Poller::hasChannel(Channel* channel) const
{assertInLoopThread();ChannelMap::const_iterator it channels_.find(channel-fd());return it ! channels_.end() it-second channel;
}EPollPoller.h
#ifndef MUDUO_NET_POLLER_EPOLLPOLLER_H
#define MUDUO_NET_POLLER_EPOLLPOLLER_H#include muduo/net/Poller.h#include vectorstruct epoll_event;namespace muduo
{
namespace net
{///
/// IO Multiplexing with epoll(4).
///
class EPollPoller : public Poller
{public:EPollPoller(EventLoop* loop);~EPollPoller() override;Timestamp poll(int timeoutMs, ChannelList* activeChannels) override;void updateChannel(Channel* channel) override;void removeChannel(Channel* channel) override;private:static const int kInitEventListSize 16;static const char* operationToString(int op);void fillActiveChannels(int numEvents,ChannelList* activeChannels) const;void update(int operation, Channel* channel);typedef std::vectorstruct epoll_event EventList;int epollfd_;EventList events_;
};} // namespace net
} // namespace muduo
#endif // MUDUO_NET_POLLER_EPOLLPOLLER_H
EPollPoller.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/EPollPoller.h#include muduo/base/Logging.h
#include muduo/net/Channel.h#include assert.h
#include errno.h
#include poll.h
#include sys/epoll.h
#include unistd.husing namespace muduo;
using namespace muduo::net;/*struct epoll_event
{uint32_t events; //Epoll eventsepoll_data_t data; //User data variable
} __attribute__ ((__packed__));typedef union epoll_data
{void *ptr;int fd;uint32_t u32;uint64_t u64;
} epoll_data_t;*/// On Linux, the constants of poll(2) and epoll(4)
// are expected to be the same.
static_assert(EPOLLIN POLLIN, epoll uses same flag values as poll);
static_assert(EPOLLPRI POLLPRI, epoll uses same flag values as poll);
static_assert(EPOLLOUT POLLOUT, epoll uses same flag values as poll);
static_assert(EPOLLRDHUP POLLRDHUP, epoll uses same flag values as poll);
static_assert(EPOLLERR POLLERR, epoll uses same flag values as poll);
static_assert(EPOLLHUP POLLHUP, epoll uses same flag values as poll);namespace
{
const int kNew -1; //channel尚未添加到poller中
const int kAdded 1; //已经添加了
const int kDeleted 2; //之前监听过了后来移除了监听
}//当flag EPOLL_CLOEXEC创建的epfd会设置FD_CLOEXEC
//FD_CLOEXEC表示当程序执行exec函数时本fd将被系统自动关闭,表示不传递给exec创建的新进程
EPollPoller::EPollPoller(EventLoop* loop): Poller(loop),//创建epollfd使用带1的版本//如果参数为0,则与epoll_create版本相同,设置为O_CLOEXEC,查看open函数的这个参数解释,//子进程fork并调用exec时会关闭这个fdepollfd_(::epoll_create1(EPOLL_CLOEXEC)), events_(kInitEventListSize) //vector这样用时初始化kInitEventListSize个大小空间,默认16
{if (epollfd_ 0) //在构造函数中判断0就abort(){LOG_SYSFATAL EPollPoller::EPollPoller;}
}EPollPoller::~EPollPoller()
{::close(epollfd_);
}Timestamp EPollPoller::poll(int timeoutMs, ChannelList* activeChannels)//ChannelList是一个存放channel的vector
{LOG_TRACE fd total count channels_.size();int numEvents ::epoll_wait(epollfd_,*events_.begin(), //events_已初始化,是存放epoll_event的vectorstatic_castint(events_.size()), //监控套接字的数目timeoutMs);int savedErrno errno;Timestamp now(Timestamp::now());if (numEvents 0){LOG_TRACE numEvents events happened;fillActiveChannels(numEvents, activeChannels);if (implicit_castsize_t(numEvents) events_.size()) //如果返回的事件数目等于当前事件数组大小就分配2倍空间{events_.resize(events_.size()*2);}}else if (numEvents 0){LOG_TRACE nothing happened;}else{// error happens, log uncommon onesif (savedErrno ! EINTR){errno savedErrno;LOG_SYSERR EPollPoller::poll();}}return now;
}//把返回到的这么多个事件添加到activeChannels
void EPollPoller::fillActiveChannels(int numEvents,ChannelList* activeChannels) const
{assert(implicit_castsize_t(numEvents) events_.size());for (int i 0; i numEvents; i) //确定它的大小小于events_的大小因为events_是预留的事件vector{Channel* channel static_castChannel*(events_[i].data.ptr);
#ifndef NDEBUGint fd channel-fd(); //debug时做一下检测ChannelMap::const_iterator it channels_.find(fd);assert(it ! channels_.end());assert(it-second channel);
#endifchannel-set_revents(events_[i].events); //把已发生的事件传给channel,写到通道当中activeChannels-push_back(channel); //并且push_back进activeChannels}
}//这个函数被调用是因为channel-enablereading()被调用再调用channel-update()再event_loop-updateChannel()再-epoll或poll的updateChannel被调用
//
void EPollPoller::updateChannel(Channel* channel)
{Poller::assertInLoopThread(); //在IO线程const int index channel-index(); //初始状态index是-1LOG_INFO fd channel-fd() events channel-events() index index;// 当是新的或是之前监听过后来移除了监听// 两者的区别在于,新的channel 之前没有在epoll 中保存// 而 del 的之前在 channels_ 中保存了但是没有被放入epoll_ctl中监听if (index kNew || index kDeleted) //index是在poll中是下标在epoll中是三种状态上面有三个常量{// a new one, add with EPOLL_CTL_ADDint fd channel-fd();if (index kNew){assert(channels_.find(fd) channels_.end()); //channels_是一个Mapchannels_[fd] channel;}else // index kDeleted{assert(channels_.find(fd) ! channels_.end());assert(channels_[fd] channel);}channel-set_index(kAdded);update(EPOLL_CTL_ADD, channel); //注册事件}else{// update existing one with EPOLL_CTL_MOD/DELint fd channel-fd();(void)fd;assert(channels_.find(fd) ! channels_.end());assert(channels_[fd] channel);assert(index kAdded);// 既然已经添加了那么可能的修改就是修改监听的时间或者不在监听// 因此这里先判断是否是没有监听的事件了如果是那么直接移除、if (channel-isNoneEvent()) //判断无事件{update(EPOLL_CTL_DEL, channel); //删除事件channel-set_index(kDeleted); //删除后被设置为kDeleted}else{update(EPOLL_CTL_MOD, channel); //修改已注册的监听事件}}
}void EPollPoller::removeChannel(Channel* channel)
{Poller::assertInLoopThread(); //判断是否在IO线程int fd channel-fd();LOG_TRACE fd fd;assert(channels_.find(fd) ! channels_.end());assert(channels_[fd] channel);assert(channel-isNoneEvent());int index channel-index();assert(index kAdded || index kDeleted);size_t n channels_.erase(fd); //删除(void)n; assert(n 1);if (index kAdded){update(EPOLL_CTL_DEL, channel);}channel-set_index(kNew);
}void EPollPoller::update(int operation, Channel* channel)
{printf(-------%s,line.%d-------\n,__FUNCTION__,__LINE__);struct epoll_event event; //存放数据的结构体memZero(event, sizeof event);event.events channel-events(); //注册的事件event.data.ptr channel;int fd channel-fd();LOG_INFO epoll_ctl op operationToString(operation) fd fd event { channel-eventsToString() };if (::epoll_ctl(epollfd_, operation, fd, event) 0)//epoll_ctl失败返回-1{if (operation EPOLL_CTL_DEL){LOG_SYSERR epoll_ctl op operationToString(operation) fd fd;}else{LOG_SYSFATAL epoll_ctl op operationToString(operation) fd fd;}}
}const char* EPollPoller::operationToString(int op)
{switch (op){case EPOLL_CTL_ADD:return ADD;case EPOLL_CTL_DEL:return DEL;case EPOLL_CTL_MOD:return MOD;default:assert(false ERROR op);return Unknown Operation;}
}
