ACE_Select_Reactor_T 介绍 (2)

本章目录

• ACE_Select_Reactor_T 介绍
  • 类继承图
  • 类协作图
  • 类主要成员变量
  • 事件处理函数调用图
  • 事件处理主流程
    • handle_events 函数流程
    • handle_events_i 函数流程

2. ACE_Select_Reactor_T 介绍

该类继承自类ACE_Select_Reactor_Impl，实现了对IO时间、信号量、定时器的分发处理，公共的函数需要ACE_Reactor_Token进行锁定。typedef ACE_Select_Reactor_T<ACE_Select_Reactor_Token> ACE_Select_Reactor定义了常用的ACE_Select_Reactor类，可以在程序中直接使用。

2.1. 类继承图

2.2. 类协作图

ACE_Select_Reactor 核心交互图，表明了 ACE_Select_Reactor 针对 Socket/IO, 定时器，通知和信号量的整体数据结构。

2.3. 类主要成员变量

ACE_Select_Reactor_Impl继承自 ACE_Reactor_Impl，在类ACE_Select_Reactor_Impl中定义了常用的成员变量：

ace/Select_Reactor_Base.h

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/// 提供<ACE_HANDLE>到<ACE_Event_Handler *>的映射 ACE_Select_Reactor_Handler_Repository handler_rep_; /// 跟踪使用select函数返回的已触发的handle ACE_Select_Reactor_Handle_Set dispatch_set_; /// 跟踪要被select函数跟踪的句柄 ACE_Select_Reactor_Handle_Set wait_set_; /// 跟踪当前被挂起的句柄 ACE_Select_Reactor_Handle_Set suspend_set_; /// 跟踪我们感兴趣但不使用select函数触发的其他类型的各种句柄，例如 handle_*() 函数的返回值大于 0 ACE_Select_Reactor_Handle_Set ready_set_; /// 定义时间轮队列指针，默认为：ACE_Timer_Heap ACE_Timer_Queue *timer_queue_; /// 处理信号量而不是用全局/静态的变量 ACE_Sig_Handler *signal_handler_; /// 回调对象用于唤醒睡眠中的ACE_Select_Reactor，默认为ACE_Select_Reactor_Notify ACE_Reactor_Notify *notify_handler_; /// 跟踪是否需要我们自己负责删除时间队列标志 bool delete_timer_queue_; /// 跟踪是否需要我们自己删除信号句柄 bool delete_signal_handler_; /// 跟踪是否需要我们自己删除通知句柄 bool delete_notify_handler_; /// 是否进行初始化的标记 bool initialized_; /// 是否自动重启<handle_events>的事件循环，如果select被信号量中断 bool restart_; /// 表明ACE_Select_Reactor主线程在<notify>回调等待列表中的位置。如果等于-1表明在list的尾部， /// 0表明在队列首部，如果大于1表明队列等待队列需要处理的数目 int requeue_position_; /// 创建该类的的原始线程 ACE_thread_t owner_; /// 如果为true表明state已经在ACE_Event_Handler派发过程中发生了变化。这用于确定我们是否 /// 需要在<Select_Reactor>的<wait_for_multiple_events>循环中做做另外一次迭代 /// ACE_Select_Reactor_Impl::clear_dispatch_mask (ACE_HANDLE handle,ACE_Reactor_Mask mask)中修改了 /// dispatch_set_中的handle的mask，则会将该状态设置成true。 bool state_changed_; /// 如果为false，则reactor在事件分发过程中将不屏蔽信号量。这对于不注册任何信号量句柄的程序非常有用， /// 如果修改这个mask的值，可以减少内核层次锁的开销 bool mask_signals_;

注解

其中ACE_Select_Reactor_Handler_Repository handler_rep_的数据结构定义，可参见 bind 函数 。

2.4. 事件处理函数调用图

注解

calculate_timeout 函数的调用为类实现中 timer_queue_ 时间队列中最早到期时间，以便设置后续 select 调用函数的超时时间，从而实现了时间队列与IO句柄触发的整合。

2.5. 事件处理主流程

ace/Reactor.cpp

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int ACE_Reactor::run_reactor_event_loop (ACE_Time_Value &tv, REACTOR_EVENT_HOOK eh) { ACE_TRACE ("ACE_Reactor::run_reactor_event_loop"); if (this->reactor_event_loop_done ()) return 0; while (1) { int result = this->implementation_->handle_events (tv); if (eh != 0 && (*eh) (this)) continue; else if (result == -1) { if (this->implementation_->deactivated ()) result = 0; return result; } else if (result == 0) { // The <handle_events> method timed out without dispatching // anything. Because of rounding and conversion errors and // such, it could be that the wait loop (WFMO, select, etc.) // timed out, but the timer queue said it wasn't quite ready // to expire a timer. In this case, the ACE_Time_Value we // passed into handle_events won't have quite been reduced // to 0, and we need to go around again. If we are all the // way to 0, just return, as the entire time the caller // wanted to wait has been used up. if (tv.usec () > 0) continue; return 0; } // Else there were some events dispatched; go around again } ACE_NOTREACHED (return 0;) }

行12行，Reactor调用了其实现者的 handle_events(ACE_Time_Value *max_wait_time) 函数，实现类的handle_event函数承担了主要工作的分发和处理。

2.5.1. handle_events 函数流程

ace/Select_Reactor_T.cpp handle_events 函数

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template <class ACE_SELECT_REACTOR_TOKEN> int ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::handle_events (ACE_Time_Value *max_wait_time) { ACE_TRACE ("ACE_Select_Reactor_T::handle_events"); // Stash the current time -- the destructor of this object will // automatically compute how much time elapsed since this method was // called. ACE_Countdown_Time countdown (max_wait_time); #if defined (ACE_MT_SAFE) && (ACE_MT_SAFE != 0) ACE_GUARD_RETURN (ACE_SELECT_REACTOR_TOKEN, ace_mon, this->token_, -1); if (ACE_OS::thr_equal (ACE_Thread::self (), this->owner_) == 0) { errno = EACCES; return -1; } if (this->deactivated_) { errno = ESHUTDOWN; return -1; } // Update the countdown to reflect time waiting for the mutex. countdown.update (); #else if (this->deactivated_) { errno = ESHUTDOWN; return -1; } #endif /* ACE_MT_SAFE */ return this->handle_events_i (max_wait_time); }

2.5.2. handle_events_i 函数流程

ace/Select_Reactor_T.cpp handle_events_i 函数

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template <class ACE_SELECT_REACTOR_TOKEN> int ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::handle_events_i (ACE_Time_Value *max_wait_time) { int result = -1; ACE_SEH_TRY { // We use the data member dispatch_set_ as the current dispatch // set. // We need to start from a clean dispatch_set this->dispatch_set_.rd_mask_.reset (); this->dispatch_set_.wr_mask_.reset (); this->dispatch_set_.ex_mask_.reset (); int number_of_active_handles = this->wait_for_multiple_events (this->dispatch_set_, max_wait_time); result = this->dispatch (number_of_active_handles, this->dispatch_set_); } ACE_SEH_EXCEPT (this->release_token ()) { // As it stands now, we catch and then rethrow all Win32 // structured exceptions so that we can make sure to release the // <token_> lock correctly. } return result; }

行18, this->wait_for_multiple_events (this->dispatch_set_,max_wait_time) 实现了对于可分发句柄集的获取。

行21，this->dispatch (number_of_active_handles,this->dispatch_set_) 实现了对于分发句柄集的处理。

2.5.2.1. wait_for_multiple_events 函数

ace/Select_Reactor_T.cpp wait_for_multiple_events 函数

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// Must be called with lock held. template <class ACE_SELECT_REACTOR_TOKEN> int ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::wait_for_multiple_events (ACE_Select_Reactor_Handle_Set &dispatch_set, ACE_Time_Value *max_wait_time) { ACE_TRACE ("ACE_Select_Reactor_T::wait_for_multiple_events"); ACE_Time_Value timer_buf (0); ACE_Time_Value *this_timeout = 0; int number_of_active_handles = this->any_ready (dispatch_set); // If there are any bits enabled in the <ready_set_> then we'll // handle those first, otherwise we'll block in <select>. if (number_of_active_handles == 0) { do { if (this->timer_queue_ == 0) return 0; this_timeout = this->timer_queue_->calculate_timeout (max_wait_time, &timer_buf); #ifdef ACE_WIN32 // This arg is ignored on Windows and causes pointer // truncation warnings on 64-bit compiles. int const width = 0; #else int const width = this->handler_rep_.max_handlep1 (); #endif /* ACE_WIN32 */ dispatch_set.rd_mask_ = this->wait_set_.rd_mask_; dispatch_set.wr_mask_ = this->wait_set_.wr_mask_; dispatch_set.ex_mask_ = this->wait_set_.ex_mask_; number_of_active_handles = ACE_OS::select (width, dispatch_set.rd_mask_, dispatch_set.wr_mask_, dispatch_set.ex_mask_, this_timeout); } while (number_of_active_handles == -1 && this->handle_error () > 0); if (number_of_active_handles > 0) { #if !defined (ACE_WIN32) // Resynchronize the fd_sets so their "max" is set properly. dispatch_set.rd_mask_.sync (this->handler_rep_.max_handlep1 ()); dispatch_set.wr_mask_.sync (this->handler_rep_.max_handlep1 ()); dispatch_set.ex_mask_.sync (this->handler_rep_.max_handlep1 ()); #endif /* ACE_WIN32 */ } else if (number_of_active_handles == -1) { // Normally, select() will reset the bits in dispatch_set // so that only those filed descriptors that are ready will // have bits set. However, when an error occurs, the bit // set remains as it was when the select call was first made. // Thus, we now have a dispatch_set that has every file // descriptor that was originally waited for, which is not // correct. We must clear all the bit sets because we // have no idea if any of the file descriptors is ready. // // NOTE: We dont have a test case to reproduce this // problem. But pleae dont ignore this and remove it off. dispatch_set.rd_mask_.reset (); dispatch_set.wr_mask_.reset (); dispatch_set.ex_mask_.reset (); } } // Return the number of events to dispatch. return number_of_active_handles; }

行12,，this->any_ready(dispatch_set) 实现了获取不需要select函数触发的其他类型满足触发条件的句柄

行25-26，this->timer_queue_->calculate_timeout(max_wait_time,&timer_buf) 实现了对定时器队列的超时的计算

行38-42，ACE_OS::select(width,dispatch_set.rd_mask_,dispatch_set.wr_mask_,dispatch_set.ex_mask_,this_timeout) 实现了对使用select函数返回的已触发的handle的跟踪

2.5.2.2. dispatch 函数

ace/Select_Reactor_T.cpp dispatch 函数

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template <class ACE_SELECT_REACTOR_TOKEN> int ACE_Select_Reactor_T<ACE_SELECT_REACTOR_TOKEN>::dispatch (int active_handle_count, ACE_Select_Reactor_Handle_Set &dispatch_set) { ACE_TRACE ("ACE_Select_Reactor_T::dispatch"); int io_handlers_dispatched = 0; int other_handlers_dispatched = 0; int signal_occurred = 0; // The following do/while loop keeps dispatching as long as there // are still active handles. Note that the only way we should ever // iterate more than once through this loop is if signals occur // while we're dispatching other handlers. do { // We expect that the loop will decrease the number of active // handles in each iteration. If it does not, then something is // inconsistent in the state of the Reactor and we should avoid // the loop. Please read the comments on bug 2540 for more // details. int initial_handle_count = active_handle_count; // Note that we keep track of changes to our state. If any of // the dispatch_*() methods below return -1 it means that the // <wait_set_> state has changed as the result of an // <ACE_Event_Handler> being dispatched. This means that we // need to bail out and rerun the select() loop since our // existing notion of handles in <dispatch_set> may no longer be // correct. // // In the beginning, our state starts out unchanged. After // every iteration (i.e., due to signals), our state starts out // unchanged again. this->state_changed_ = false; // Perform the Template Method for dispatching all the handlers. // First check for interrupts. if (active_handle_count == -1) { // Bail out -- we got here since <select> was interrupted. if (ACE_Sig_Handler::sig_pending () != 0) { ACE_Sig_Handler::sig_pending (0); // If any HANDLES in the <ready_set_> are activated as a // result of signals they should be dispatched since // they may be time critical... active_handle_count = this->any_ready (dispatch_set); // Record the fact that the Reactor has dispatched a // handle_signal() method. We need this to return the // appropriate count below. signal_occurred = 1; } else return -1; } // Handle timers early since they may have higher latency // constraints than I/O handlers. Ideally, the order of // dispatching should be a strategy... else if (this->dispatch_timer_handlers (other_handlers_dispatched) == -1) // State has changed or timer queue has failed, exit loop. break; // Check to see if there are no more I/O handles left to // dispatch AFTER we've handled the timers... else if (active_handle_count == 0) return io_handlers_dispatched + other_handlers_dispatched + signal_occurred; // Next dispatch the notification handlers (if there are any to // dispatch). These are required to handle multi-threads that // are trying to update the <Reactor>. else if (this->dispatch_notification_handlers (dispatch_set, active_handle_count, other_handlers_dispatched) == -1) // State has changed or a serious failure has occured, so exit // loop. break; // Finally, dispatch the I/O handlers. else if (this->dispatch_io_handlers (dispatch_set, active_handle_count, io_handlers_dispatched) == -1) // State has changed, so exit loop. break; // if state changed, we need to re-eval active_handle_count, // so we will not end with an endless loop if (initial_handle_count == active_handle_count || this->state_changed_) { active_handle_count = this->any_ready (dispatch_set); } } while (active_handle_count > 0); return io_handlers_dispatched + other_handlers_dispatched + signal_occurred; }

处理顺序：

1. dispatch_timer_handlers 处理分发定时器，定时器的处理优于Socket/IO的处理。 展开流程见： 定时器与Select_Reactor的分发集成。
2. dispatch_notification_handlers 处理分发通知类消息。展开流程见： 通知与Select_Reactor 的分发集成。
3. dispatch_io_handlers 处理分发 io handlers。展开流程见： IO句柄与Select_Reactor的分发集成。