ACE_Event_Handler

 ACE_Event_Handler
 

/**
 * @class ACE_Event_Handler
 *
 * @brief Provides an abstract interface for handling various types of
 * I/O, timer, and signal events.
 *
 * Subclasses read/write input/output on an I/O descriptor,
 * handle an exception raised on an I/O descriptor, handle a
 * timer's expiration, or handle a signal.
 */

ACE_Event_Handler 眉头注释: 提供一个抽象接口，处理各种 I/O, 定时器和信号（事件）

子类处理下面事情:  读写一个 I/O 描述字;  处理 I/O 描述字产生的异常; 处理定时器触发事件;  处理一个信号.

 

  /// Destructor is virtual to enable proper cleanup.
  virtual ~ACE_Event_Handler (void);

析构函数声明成虚的， 使得多态时保证调用子类的析构函数，让对象得到合适的析构。

 

  /// Get the I/O handle.
  virtual ACE_HANDLE get_handle (void) const;

得到 I/O handle

 

/// Set the I/O handle.
  virtual void set_handle (ACE_HANDLE);

设置 I/O handle

 

  // Priorities run from MIN_PRIORITY (which is the "lowest priority")
  // to MAX_PRIORITY (which is the "highest priority").
  /// Get the priority of the Event_Handler.
  virtual int priority (void) const;

  /// Set the priority of the Event_Handler.
  virtual void priority (int priority);

 

优先级取值区间 [MIN_PRIORITY,  MAX_PRIORITY]; 这里是优先级的 获取和设置方法。

 

  /// Called when input events occur (e.g., connection or data).
  virtual int handle_input (ACE_HANDLE fd = ACE_INVALID_HANDLE);

当有输入事件产生时， handle_input 会被调用。“输入事件”包含 一个新的连接，一些数据到达 I/O 等。

 

  /// Called when output events are possible (e.g., when flow control
  /// abates or non-blocking connection completes).
  virtual int handle_output (ACE_HANDLE fd = ACE_INVALID_HANDLE);

当输出事件可行时，handle_out 函数会被调用。输出事件包含 流控制缓和（应该是指底层发送缓存不再是满的状态）， 非阻塞连接完成了。

 

  /// Called when an exceptional events occur (e.g., SIGURG).
  virtual int handle_exception (ACE_HANDLE fd = ACE_INVALID_HANDLE);

当一个异常的事件发生时， SIGURG 信号会被触发。 异常的时间包含 “SIGURG 信号到达” 等。  当 Out_Of_Band data(带外数据) 到达了 socket, SIGURG 信号会被发送给 socket 的宿主进程。

 

  /**
   * Called when timer expires.  @a current_time represents the current
   * time that the Event_Handler was selected for timeout
   * dispatching and @a act is the asynchronous completion token that
   * was passed in when <schedule_timer> was invoked.
   */
  virtual int handle_timeout (const ACE_Time_Value ¤t_time,
                              const void *act = 0);

当定时器触发时 handle_timeout 函数会被调用； 第一个参数 current _time 表示 当前时间，这个时间是 Event_Handler 被选择超时分发的时间点。 第二个参数是异步完成标志， 这个标志是通过 schedule_timer 设置定时器时指定的。

 

  /// Called when a process exits.
  virtual int handle_exit (ACE_Process *);

当进程退出时， handle_exit 函数会被调用。

 

  /// Called when a <handle_*()> method returns -1 or when the
  /// <remove_handler> method is called on an ACE_Reactor.  The
  /// @a close_mask indicates which event has triggered the
  /// <handle_close> method callback on a particular @a handle.
  virtual int handle_close (ACE_HANDLE handle,
                            ACE_Reactor_Mask close_mask);

当某一个 handle_*() 方法返回 -1 时 或者 remove_handler 对一个 ACE_Reactor 调用时， handle_close 函数会被调用。第二个参数 close_mask 指明是哪个事件触发调用了 hand_close 回调方法， 第一个是发生事件的 handle.

 

  /// Called when object is signaled by OS (either via UNIX signals or
  /// when a Win32 object becomes signaled).
  virtual int handle_signal (int signum, siginfo_t * = 0, ucontext_t * = 0);

当对象收到操作系统的信号时，handle_signal 函数会被调用。 

  /**
   * Called to figure out whether the handler needs to resumed by the
   * reactor or the application can take care of it. The default
   * value of 0 would be returned which would allow the reactor to
   * take care of resumption of the handler. The application can
   * return a value more than zero and decide to resume the handler
   * themseleves.
   *
   * @note This method is only useful for the ACE_TP_Reactor. Sad
   * that we have to have this method in a class that is supposed to
   * be used across different components in ACE.
   */
  virtual int resume_handler (void);

这个函数会被调用来找出，到底是 reactor  需要接手 handler 还是上层应用程序接手 handler.  如果底层的函数没有重新实现此函数， 那么默认值 0 将被返回。 0 表示reactor 被允许接手 handler. 上层程序可以重载这个虚函数的实现，返回大于 0 的数字，表示上层程序将接受 handler.

  // = Accessors to set/get the various event demultiplexors.
  /// Set the event demultiplexors.
  virtual void reactor (ACE_Reactor *reactor);

  /// Get the event demultiplexors.
  virtual ACE_Reactor *reactor (void) const;

  /// Get only the reactor's timer related interface.
  virtual ACE_Reactor_Timer_Interface *reactor_timer_interface (void) const;

取得和设置多路复用解调器。

取得多路复用解调器的时间相关接口

<其他的很多看不懂>

未完。。。