handy源码阅读（五）：PollerBase类

使用poll内核函数等待事件发生：

struct PollerBase: private noncopyable {
  int64_t id_;
  int lastActive_;
  PollerBase(): lastActive_(-1) {
    static std::atomic id(0);
    id_ = ++id;
  }

  virtual void addChannel(Channel* ch) = 0;
  virtual void removeChannel(Channel* ch) = 0;
  virtual void updateChannel(Channel* ch) = 0;
  virtual ~PollerBase() {};
};

struct PollerEpoll : public PollerBase {
  int fd_;
  std::set liveChannels_;
  struct epoll_event activeEvs_[kMaxEvents];

  PollerEpoll();
  ~PollerEpoll();
  void addChannel(Channel* ch) override;
  void removeChannel(Channel* ch) override;
  void updateChannel(Channel* ch) override;
  void loop_once(int waitMs) override;
};