handy源码阅读（四）：Channel类

通道，封装了可以进行epoll的一个fd。

struct Channel: private noncopyable {
  Channel(EventBase* base, int fd, int events);
  ~Channel();
  EventBase* getBase() { return base_; }
  int fd() { return fd_; }

  //通道id
  int64_d id() {  return id_; }
  short events() {  return events_; }
  //关闭通道
  void close();

  void onRead(const Task& readcb) {  readcb_ = readcb;  }
  void onWrite(const Task& writecb) {  writecb_ = writecb;  }
  void onRead(Task&& readcb) {  readcb_ = std::move(readcb);  }
  void onWrite(Task&& writecb) {  writecb_ = std::move(writecb);  }

  //启动读写监听
  void enableRead(bool enable);
  void enableWrite(bool enable);
  void enableReadWrite(bool readable, bool writeable);
  bool readEnabled();
  bool writeEnabled();

  //处理读写事件
  void handleRead() {  readcb_();  }
  void handleWrite() {  writecb_();  }

protected:
  EventBase* base_;
  PollerBase* poller_;
  int fd_;
  short events_;
  int64_t id_;
  std::function<void()> readcb_, writecb_, errorcb_;
};

其实现为：

Channel::Channel(EventBase* base, int fd, int events): base_(base), fd_(fd), events_(events) {
  fatalif(net::setNonBlock(fd_) < 0, "channel set non block failed");
  static atomic<int64_t> id(0);
  id_ = ++id;
  poller_ = base->imp_->poller_;
  poller_->addChannel(this);
}

Channel::~Channel() {
  close();
}

void Channle::enableRead(bool enable) {
  if (enable) {
    events_ |= kReadEvent;
  } else {
    events_ &= ~KReadEvent;
  }
  poller_->updateChannel(this);
}

void Channel::enableWrite(bool enable) {
  if (enable) {
    events_ |= kWriteEvent;
  } else {
    events_ &= ~kWriteEvent;
  }
  poller_->updateChannel(this);
}

void Channel::enableReadWrite(bool readable, bool writable) {
  if (readable) {
    events_ |= kReadEvent;
  } else {
    events_ &= ~kReadEvent;
  }
  if (writable) {
    events_ |= kWriteEvent;
  } else {
    events_ &= ~kWriteEvent;
  }
  poller_->updateChannel(this);
}

void Channel::close() {
  if (fd_ >= 0) {
    trace("close channel %ld fd %d", (long)id_, fd_);
    poller_->removeChannel(this);
    ::close(fd_);
    fd_ = -1;
    handleRead();
  }
}

bool Channel::readEnabled() {
  return events_ & kReadEvent;
}

bool Channel::writeEnabled() {
  return events_ & kWriteEvent;
}

 本类的核心在于使用poller类进行添加删除更新channel状态，或是直接调用对应的函数对象。