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3. I/O Handler的管理

«  2. ACE_Select_Reactor_T 介绍   ::   目录   ::   4. Notification 通知时间派发处理  »

本章目录

3. I/O Handler的管理

3.1. IO句柄与Select_Reactor的分发集成

3.1.1. dispatch_io_handlers 函数

ace/Select_Reactor_T.cpp dispatch_io_handlers 函数

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template <class ACE_SELECT_REACTOR_TOKEN> int
ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::dispatch_io_handlers
  (ACE_Select_Reactor_Handle_Set &dispatch_set,
   int &number_of_active_handles,
   int &number_of_handlers_dispatched)
{
  ACE_TRACE ("ACE_Select_Reactor_T::dispatch_io_handlers");

  // Handle output events (this code needs to come first to handle the
  // obscure case of piggy-backed data coming along with the final
  // handshake message of a nonblocking connection).

  if (this->dispatch_io_set (number_of_active_handles,
                             number_of_handlers_dispatched,
                             ACE_Event_Handler::WRITE_MASK,
                             dispatch_set.wr_mask_,
                             this->ready_set_.wr_mask_,
                             &ACE_Event_Handler::handle_output) == -1)
    {
      number_of_active_handles -= number_of_handlers_dispatched;
      return -1;
    }

  // ACELIB_DEBUG ((LM_DEBUG,  ACE_TEXT ("ACE_Select_Reactor_T::dispatch - EXCEPT\n")));
  if (this->dispatch_io_set (number_of_active_handles,
                             number_of_handlers_dispatched,
                             ACE_Event_Handler::EXCEPT_MASK,
                             dispatch_set.ex_mask_,
                             this->ready_set_.ex_mask_,
                             &ACE_Event_Handler::handle_exception) == -1)
    {
      number_of_active_handles -= number_of_handlers_dispatched;
      return -1;
    }

  // ACELIB_DEBUG ((LM_DEBUG,  ACE_TEXT ("ACE_Select_Reactor_T::dispatch - READ\n")));
  if (this->dispatch_io_set (number_of_active_handles,
                             number_of_handlers_dispatched,
                             ACE_Event_Handler::READ_MASK,
                             dispatch_set.rd_mask_,
                             this->ready_set_.rd_mask_,
                             &ACE_Event_Handler::handle_input) == -1)
    {
      number_of_active_handles -= number_of_handlers_dispatched;
      return -1;
    }

  number_of_active_handles -= number_of_handlers_dispatched;
  return 0;
}

3.1.2. dispatch_io_set 函数

ace/Select_Reactor_T.cpp dispatch_io_set 函数

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template <class ACE_SELECT_REACTOR_TOKEN> int
ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::dispatch_io_set
  (int number_of_active_handles,
   int &number_of_handlers_dispatched,
   int mask,
   ACE_Handle_Set &dispatch_mask,
   ACE_Handle_Set &ready_mask,
   ACE_EH_PTMF callback)
{
  ACE_TRACE ("ACE_Select_Reactor_T::dispatch_io_set");
  ACE_HANDLE handle;

  ACE_Handle_Set_Iterator handle_iter (dispatch_mask);

  while ((handle = handle_iter ()) != ACE_INVALID_HANDLE &&
         number_of_handlers_dispatched < number_of_active_handles)
    {
      ++number_of_handlers_dispatched;

      this->notify_handle (handle,
                           mask,
                           ready_mask,
                           this->handler_rep_.find (handle),
                           callback);

      // clear the bit from that dispatch mask,
      // so when we need to restart the iteration (rebuilding the iterator...)
      // we will not dispatch the already dispatched handlers
      this->clear_dispatch_mask (handle, mask);

      if (this->state_changed_)
        {

          handle_iter.reset_state ();
          this->state_changed_ = false;
        }
    }

  return 0;
}

3.1.3. notify_handle 函数

ace/Select_Reactor_T.cpp notify_handle 函数

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template <class ACE_SELECT_REACTOR_TOKEN> void
ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::notify_handle
  (ACE_HANDLE handle,
   ACE_Reactor_Mask mask,
   ACE_Handle_Set &ready_mask,
   ACE_Event_Handler *event_handler,
   ACE_EH_PTMF ptmf)
{
  ACE_TRACE ("ACE_Select_Reactor_T::notify_handle");
  // Check for removed handlers.
  if (event_handler == 0)
    return;

  bool const reference_counting_required =
    event_handler->reference_counting_policy ().value () ==
    ACE_Event_Handler::Reference_Counting_Policy::ENABLED;

  // Call add_reference() if needed.
  if (reference_counting_required)
    {
      event_handler->add_reference ();
    }

  int const status = (event_handler->*ptmf) (handle);

  if (status < 0)
    this->remove_handler_i (handle, mask);
  else if (status > 0)
    ready_mask.set_bit (handle);

  // Call remove_reference() if needed.
  if (reference_counting_required)
    event_handler->remove_reference ();
}

如果回调函数 status < 0, 则调用移除该 handle 的对应 mask：this->remove_handler_i (handle, mask) 。

如果回调函数 status > 0， 这表明该 handle 需要继续被调度处理，则需要将该 handle 设置到 ready_set_ 中再次被派发。

3.2. handler注册

3.2.1. register_handler 函数流程

ace/Select_Reactor_T.cpp register_handler 函数

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template <class ACE_SELECT_REACTOR_TOKEN> int
ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::register_handler
  (ACE_HANDLE handle,
   ACE_Event_Handler *handler,
   ACE_Reactor_Mask mask)
{
  ACE_TRACE ("ACE_Select_Reactor_T::register_handler");
  ACE_MT (ACE_GUARD_RETURN (ACE_SELECT_REACTOR_TOKEN, ace_mon, this->token_, -1));
  return this->register_handler_i (handle, handler, mask);
}

3.2.2. register_handler_i 函数流程

ace/Select_Reactor_T.cpp register_handler 函数

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template <class ACE_SELECT_REACTOR_TOKEN> int
ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::register_handler_i
  (ACE_HANDLE handle,
   ACE_Event_Handler *event_handler,
   ACE_Reactor_Mask mask)
{
  ACE_TRACE ("ACE_Select_Reactor_T::register_handler_i");

  // Insert the <handle, event_handle> tuple into the Handler
  // Repository.
  return this->handler_rep_.bind (handle, event_handler, mask);
}

3.2.3. bind 函数

映射数据结构定义

行26实现了真正的关联操作，this->event_handlers_.bind (handle, event_handler, entry); 其中变量 event_handlers_ 在程序中定义为*map_type*, 在Unix下具体定义如下 typedef ACE_Array_Base<value_type> map_type;，也即使用handle 句柄值作为数组的索引，实现了map的功能。在windows下使用了ACE_Hash_Map_Manager_Ex作为map实现的类， typedef ACE_Hash_Map_Manager_Ex<key_type,value_type, ACE_Hash<key_type>,std::equal_to<key_type>,ACE_Null_Mutex> map_type;,其中 key_type的定义为：typedef ACE_HANDLE key_type;，另外value_type定义为 typedef ACE_Event_Handler * value_type;。

ace/Select_Reactor_Base.cpp bind 函数

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// Bind the <ACE_Event_Handler *> to the <ACE_HANDLE>.
int
ACE_Select_Reactor_Handler_Repository::bind (ACE_HANDLE handle,
                                             ACE_Event_Handler *event_handler,
                                             ACE_Reactor_Mask mask)
{
  ACE_TRACE ("ACE_Select_Reactor_Handler_Repository::bind");

  if (event_handler == 0)
    return -1;

  if (handle == ACE_INVALID_HANDLE)
    handle = event_handler->get_handle ();

  if (this->invalid_handle (handle))
    return -1;

  // Is this handle already in the Reactor?
  bool existing_handle = false;

#if defined (ACE_WIN32)

  map_type::ENTRY * entry = 0;

  int const result =
    this->event_handlers_.bind (handle, event_handler, entry);

  if (result == -1)
    {
      return -1;
    }
  else if (result == 1)  // Entry already exists.
    {
      // Cannot use a different handler for an existing handle.
      if (event_handler != entry->item ())
        {
          return -1;
        }
      else
        {
          // Remember that this handle is already registered in the
          // Reactor.
          existing_handle = true;
        }
    }

#else

  // Check if this handle is already registered.
  ACE_Event_Handler * const current_handler =
    this->event_handlers_[handle];

  if (current_handler)
    {
      // Cannot use a different handler for an existing handle.
      if (current_handler != event_handler)
        return -1;

      // Remember that this handle is already registered in the
      // Reactor.
      existing_handle = true;
    }

  this->event_handlers_[handle] = event_handler;

  if (this->max_handlep1_ < handle + 1)
    this->max_handlep1_ = handle + 1;

#endif /* ACE_WIN32 */

  if (this->select_reactor_.is_suspended_i (handle))
    {
      this->select_reactor_.bit_ops (handle,
                                     mask,
                                     this->select_reactor_.suspend_set_,
                                     ACE_Reactor::ADD_MASK);
    }
  else
    {
      this->select_reactor_.bit_ops (handle,
                                     mask,
                                     this->select_reactor_.wait_set_,
                                     ACE_Reactor::ADD_MASK);

      // Note the fact that we've changed the state of the <wait_set_>,
      // which is used by the dispatching loop to determine whether it can
      // keep going or if it needs to reconsult select().
      // this->select_reactor_.state_changed_ = 1;
    }

  // If new entry, call add_reference() if needed.
  if (!existing_handle)
    event_handler->add_reference ();

  return 0;
}

3.3. handler移除

3.3.1. remove_handler 函数流程

ace/Select_Reactor_T.cpp remove_handler 函数

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template <class ACE_SELECT_REACTOR_TOKEN> int
ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::remove_handler
  (ACE_HANDLE handle,
   ACE_Reactor_Mask mask)
{
  ACE_TRACE ("ACE_Select_Reactor_T::remove_handler");
  ACE_MT (ACE_GUARD_RETURN (ACE_SELECT_REACTOR_TOKEN, ace_mon, this->token_, -1));
  return this->remove_handler_i (handle, mask);
}

3.3.2. remove_handler_i 函数流程

ace/Select_Reactor_T.cpp remove_handler_i 函数

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template <class ACE_SELECT_REACTOR_TOKEN> int
ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::remove_handler_i
  (ACE_HANDLE handle,
   ACE_Reactor_Mask mask)
{
  ACE_TRACE ("ACE_Select_Reactor_T::remove_handler_i");

  // Unbind this handle.
  return this->handler_rep_.unbind (handle, mask);
}

3.3.3. unbind 函数

ace/Select_Reactor_Base.cpp unbind 函数

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int
ACE_Select_Reactor_Handler_Repository::unbind (
  ACE_HANDLE handle,
  map_type::iterator pos,
  ACE_Reactor_Mask mask)
{
  ACE_TRACE ("ACE_Select_Reactor_Handler_Repository::unbind");

  // Retrieve event handler before unbinding it from the map.  The
  // iterator pointing to it will no longer be valid once the handler
  // is unbound.
  ACE_Event_Handler * const event_handler =
    (pos == this->event_handlers_.end ()
     ? 0
     : ACE_SELECT_REACTOR_EVENT_HANDLER (pos));

  // Clear out the <mask> bits in the Select_Reactor's wait_set.
  this->select_reactor_.bit_ops (handle,
                                 mask,
                                 this->select_reactor_.wait_set_,
                                 ACE_Reactor::CLR_MASK);

  // And suspend_set.
  this->select_reactor_.bit_ops (handle,
                                 mask,
                                 this->select_reactor_.suspend_set_,
                                 ACE_Reactor::CLR_MASK);

  // Note the fact that we've changed the state of the <wait_set_>,
  // which is used by the dispatching loop to determine whether it can
  // keep going or if it needs to reconsult select().
  // this->select_reactor_.state_changed_ = 1;

  // If there are no longer any outstanding events on this <handle>
  // then we can totally shut down the Event_Handler.

  bool const has_any_wait_mask =
    (this->select_reactor_.wait_set_.rd_mask_.is_set (handle)
     || this->select_reactor_.wait_set_.wr_mask_.is_set (handle)
     || this->select_reactor_.wait_set_.ex_mask_.is_set (handle));
  bool const has_any_suspend_mask =
    (this->select_reactor_.suspend_set_.rd_mask_.is_set (handle)
     || this->select_reactor_.suspend_set_.wr_mask_.is_set (handle)
     || this->select_reactor_.suspend_set_.ex_mask_.is_set (handle));

  bool complete_removal = false;

  if (!has_any_wait_mask && !has_any_suspend_mask)
    {
#if defined (ACE_WIN32)
      if (event_handler != 0 && this->event_handlers_.unbind (pos) == -1)
        return -1;  // Should not happen!
#else
      this->event_handlers_[handle] = 0;

      if (this->max_handlep1_ == handle + 1)
        {
          // We've deleted the last entry, so we need to figure out
          // the last valid place in the array that is worth looking
          // at.
          ACE_HANDLE const wait_rd_max =
            this->select_reactor_.wait_set_.rd_mask_.max_set ();
          ACE_HANDLE const wait_wr_max =
            this->select_reactor_.wait_set_.wr_mask_.max_set ();
          ACE_HANDLE const wait_ex_max =
            this->select_reactor_.wait_set_.ex_mask_.max_set ();

          ACE_HANDLE const suspend_rd_max =
            this->select_reactor_.suspend_set_.rd_mask_.max_set ();
          ACE_HANDLE const suspend_wr_max =
            this->select_reactor_.suspend_set_.wr_mask_.max_set ();
          ACE_HANDLE const suspend_ex_max =
            this->select_reactor_.suspend_set_.ex_mask_.max_set ();

          // Compute the maximum of six values.
          this->max_handlep1_ = wait_rd_max;
          if (this->max_handlep1_ < wait_wr_max)
            this->max_handlep1_ = wait_wr_max;
          if (this->max_handlep1_ < wait_ex_max)
            this->max_handlep1_ = wait_ex_max;

          if (this->max_handlep1_ < suspend_rd_max)
            this->max_handlep1_ = suspend_rd_max;
          if (this->max_handlep1_ < suspend_wr_max)
            this->max_handlep1_ = suspend_wr_max;
          if (this->max_handlep1_ < suspend_ex_max)
            this->max_handlep1_ = suspend_ex_max;

          ++this->max_handlep1_;
        }

#endif /* ACE_WIN32 */

      // The handle has been completely removed.
      complete_removal = true;
    }

  if (event_handler == 0)
    return -1;

  bool const requires_reference_counting =
    event_handler->reference_counting_policy ().value () ==
    ACE_Event_Handler::Reference_Counting_Policy::ENABLED;

  // Close down the <Event_Handler> unless we've been instructed not
  // to.
  if (ACE_BIT_ENABLED (mask, ACE_Event_Handler::DONT_CALL) == 0)
    (void) event_handler->handle_close (handle, mask);

  // Call remove_reference() if the removal is complete and reference
  // counting is needed.
  if (complete_removal && requires_reference_counting)
    {
      (void) event_handler->remove_reference ();
    }

  return 0;
}

警告

remove_handler 函数在后续调用 unbind 函数中，会触发对 handle_close 行107-108 的调用，需要注意，否则在 handle_close 函数中 使用 remove_handler 如果没有设置 DONT_CALL 标志，会导致 handle_close 的循环调用。

3.4. handler暂停

3.4.1. suspend_handler 函数

ace/Select_Reactor_T.cpp suspend_handler 函数

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template <class ACE_SELECT_REACTOR_TOKEN> int
ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::suspend_handler (ACE_HANDLE handle)
{
  ACE_TRACE ("ACE_Select_Reactor_T::suspend_handler");
  ACE_MT (ACE_GUARD_RETURN (ACE_SELECT_REACTOR_TOKEN, ace_mon, this->token_, -1));
  return this->suspend_i (handle);
}

3.4.2. suspend_i 函数

ace/Select_Reactor_T.cpp suspend_i 函数

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template <class ACE_SELECT_REACTOR_TOKEN> int
ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::suspend_i (ACE_HANDLE handle)
{
  ACE_TRACE ("ACE_Select_Reactor_T::suspend_i");
  if (this->handler_rep_.find (handle) == 0)
    return -1;

  if (this->wait_set_.rd_mask_.is_set (handle))
    {
      this->suspend_set_.rd_mask_.set_bit (handle);
      this->wait_set_.rd_mask_.clr_bit (handle);
    }
  if (this->wait_set_.wr_mask_.is_set (handle))
    {
      this->suspend_set_.wr_mask_.set_bit (handle);
      this->wait_set_.wr_mask_.clr_bit (handle);
    }
  if (this->wait_set_.ex_mask_.is_set (handle))
    {
      this->suspend_set_.ex_mask_.set_bit (handle);
      this->wait_set_.ex_mask_.clr_bit (handle);
    }

  // Kobi: we need to remove that handle from the
  // dispatch set as well. We use that function with all the relevant
  // masks - rd/wr/ex - all the mask. it is completely suspended
  this->clear_dispatch_mask (handle, ACE_Event_Handler::RWE_MASK);
  return 0;
}

3.5. handler恢复

3.5.1. resume_handler 函数

ace/Select_Reactor_T.cpp resume_handler 函数

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template <class ACE_SELECT_REACTOR_TOKEN> int
ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::resume_handler (ACE_HANDLE handle)
{
  ACE_TRACE ("ACE_Select_Reactor_T::resume_handler");
  ACE_MT (ACE_GUARD_RETURN (ACE_SELECT_REACTOR_TOKEN, ace_mon, this->token_, -1));
  return this->resume_i (handle);
}

3.5.2. resume_handler_i 函数

ace/Select_Reactor_T.cpp resume_handler_i 函数

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template <class ACE_SELECT_REACTOR_TOKEN> int
ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::resume_i (ACE_HANDLE handle)
{
  ACE_TRACE ("ACE_Select_Reactor_T::resume_i");
  if (this->handler_rep_.find (handle) == 0)
    return -1;

  if (this->suspend_set_.rd_mask_.is_set (handle))
    {
      this->wait_set_.rd_mask_.set_bit (handle);
      this->suspend_set_.rd_mask_.clr_bit (handle);
    }
  if (this->suspend_set_.wr_mask_.is_set (handle))
    {
      this->wait_set_.wr_mask_.set_bit (handle);
      this->suspend_set_.wr_mask_.clr_bit (handle);
    }
  if (this->suspend_set_.ex_mask_.is_set (handle))
    {
      this->wait_set_.ex_mask_.set_bit (handle);
      this->suspend_set_.ex_mask_.clr_bit (handle);
    }
  return 0;
}

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