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Poller

//监听事件的函数，返回一个事件就绪的事件  virtual Timestamp poll(int timeoutMs, ChannelList* activeChannels) = 0;  /// Changes the interested I/O events.  /// Must be called in the loop thread.  //实现为纯虚函数，在PollPoller或EPollPoller 中实现  //更新所监听的事件  virtual void updateChannel(Channel* channel) = 0;  /// Remove the channel, when it destructs.  /// Must be called in the loop thread.  //删除一个Channel   virtual void removeChannel(Channel* channel) = 0;

PollPoller

typedef std::vector
   
     PollFdList;  PollFdList pollfds_;  //struct pollfd 的数组，存放所有监听的文件描述符以及事件
   

poll

Timestamp PollPoller::poll(int timeoutMs, ChannelList* activeChannels){
     // XXX pollfds_ shouldn't change  //待处理事件的数量,在此处监听  int numEvents = ::poll(&*pollfds_.begin(), pollfds_.size(), timeoutMs);  int savedErrno = errno;  //记录事件产生的事件，便于下次定时器的跟新  Timestamp now(Timestamp::now());  //有就绪事件产生  if (numEvents > 0)  {
       LOG_TRACE << numEvents << " events happened";    //将所有有事件发生的文件描述符所对应的Channle 放到activeChannels中    fillActiveChannels(numEvents, activeChannels);  }  //事件超时  else if (numEvents == 0)  {
       LOG_TRACE << " nothing happened";  }  //产生错误  else  {
       if (savedErrno != EINTR)    {
         errno = savedErrno;      LOG_SYSERR << "PollPoller::poll()";    }  }  return now;}

fillActiveChannels

void PollPoller::fillActiveChannels(int numEvents,                                    ChannelList* activeChannels) const{
   	//依次取出就绪的事件的channel   for (PollFdList::const_iterator pfd = pollfds_.begin();      pfd != pollfds_.end() && numEvents > 0; ++pfd)  {
     	//如果当前的channel 上有事件产生    if (pfd->revents > 0)    {
         --numEvents;      ChannelMap::const_iterator ch = channels_.find(pfd->fd);      assert(ch != channels_.end());      Channel* channel = ch->second;      assert(channel->fd() == pfd->fd);	  //设置该文件描述符上的事件	  //该函数不做处理，只设置到达的事件      channel->set_revents(pfd->revents);      // pfd->revents = 0;      activeChannels->push_back(channel);    }  }}

updateChannel

void PollPoller::updateChannel(Channel* channel){
     Poller::assertInLoopThread();  //记录日志  LOG_TRACE << "fd = " << channel->fd() << " events = " << channel->events();  //如果channel->index() < 0 表示新添加一个Channel   if (channel->index() < 0)  {
       // a new one, add to pollfds_    assert(channels_.find(channel->fd()) == channels_.end());    struct pollfd pfd;	//非阻塞IO 注册    pfd.fd = channel->fd();		//新产生的文件描述符    pfd.events = static_cast
   
    (channel->events());    pfd.revents = 0;	//每次循环监听都会从pollfds_中读取需要监听的文件描述符，	//所以添加到pollfds_之后下次循环就会监听    pollfds_.push_back(pfd);    int idx = static_cast
    
     (pollfds_.size())-1;    channel->set_index(idx);	//用于管理所有的Channel 对象    channels_[pfd.fd] = channel;  }  //表示该Channel 已经存在，更新监听的事件  else  {
       // update existing one    assert(channels_.find(channel->fd()) != channels_.end());    assert(channels_[channel->fd()] == channel);    int idx = channel->index();    assert(0 <= idx && idx < static_cast
     
      (pollfds_.size()));    struct pollfd& pfd = pollfds_[idx];    assert(pfd.fd == channel->fd() || pfd.fd == -channel->fd()-1);	//更新已经存在的Channel     pfd.fd = channel->fd();    pfd.events = static_cast
      
       (channel->events());    pfd.revents = 0;    if (channel->isNoneEvent())    {
         // ignore this pollfd      pfd.fd = -channel->fd()-1;    }  }}
      
     
    
   

remove

void PollPoller::removeChannel(Channel* channel){
     Poller::assertInLoopThread();  LOG_TRACE << "fd = " << channel->fd();  //断言当前的Channel 已经存在  assert(channels_.find(channel->fd()) != channels_.end());  //断言channels_ 存在的Channel 与 要删除的Channel 一致  assert(channels_[channel->fd()] == channel);  //断言当前的channel 没有要监听的事件  assert(channel->isNoneEvent());  int idx = channel->index();  assert(0 <= idx && idx < static_cast
   
    (pollfds_.size()));  const struct pollfd& pfd = pollfds_[idx]; (void)pfd;  assert(pfd.fd == -channel->fd()-1 && pfd.events == channel->events());  //删除一个Channel   size_t n = channels_.erase(channel->fd());  assert(n == 1); (void)n;  if (implicit_cast
    
     (idx) == pollfds_.size()-1)  {
       pollfds_.pop_back();  }  else  {
       int channelAtEnd = pollfds_.back().fd;	//idx 文件描述符在vector中的位置	//将最后一个文件描述符与要删除的为文件描述符交换，	//消除了删除一个元素的数据移动带来的开销    iter_swap(pollfds_.begin()+idx, pollfds_.end()-1);    if (channelAtEnd < 0)    {
         channelAtEnd = -channelAtEnd-1;    }    //重新设置最后一个文件描述符的index    channels_[channelAtEnd]->set_index(idx);	//删除一个文件描述符    pollfds_.pop_back();  }}
    
   

EPollPoller

typedef std::vector
   
     EventList;  int epollfd_;		//epoll下用于监听其他文件描述符的文件描述符  EventList events_;	//监听的事件列表
   

关于EpollPoller 的 poll 、updateChannel 、removeChannel ,功能与PollPoller 的一样，实现的内部函数不同，这里不作介绍。

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