ACE Reactor框架设计的目标是，实现一种灵活的事件处理机制，使应用无需为了满足事件处理的需要而编写平台相关的中心代码。使用Reactor框架，应用要实现其事件处理只需要做三件事情。ONE：从 ACE_Event_Handler 派生一个或多个类，并给各个虚回调方法增加应用特有的事件处理行为。#include <ace/Event_Handler.h>//...class Service : public ACE_Event_Handler{/// Called when input events occur (e.g., connection or data).virtual int handle_input (ACE_HANDLE fd = ACE_INVALID_HANDLE);/// 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);/// Called when an exceptional events occur (e.g., SIGURG).virtual int handle_exception (ACE_HANDLE fd = ACE_INVALID_HANDLE);/** * Called when timer expires. <current_time> represents the current * time that the <Event_Handler> was selected for timeout * dispatching and <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);/// Called when a process exits.virtual int handle_exit (ACE_Process *);/// Called when a <handle_*()> method returns -1 or when the/// <remove_handler> method is called on an ACE_Reactor. The/// <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);/// 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);virtual int handle_qos (ACE_HANDLE = ACE_INVALID_HANDLE);virtual int handle_group_qos (ACE_HANDLE = ACE_INVALID_HANDLE);/// Get the I/O handle.virtual ACE_HANDLE get_handle (void) const;//根据应用选择性的重载}TWO：向 ACE_Reactor 类登记应用的事件处理对象，把每个事件处理对象与它感兴趣的事件关联起来。先看ACE_Reactor（<ace/Reactor.h>）成员register_handler一个声明（还有其它几个传不同参数）：/** * Register handler for I/O events. * * A handler can be associated with multiple handles. A handle * cannot be associated with multiple handlers. * * The handle will come from ACE_Event_Handler::get_handle(). * * Reactor will call ACE_Event_Handler::add_reference() for a new * handler/handle pair. * * If this handler/handle pair has already been registered, any new * masks specified will be added. In this case, * ACE_Event_Handler::add_reference() will not be called. * * If the registered handler is currently suspended, it will remain * suspended. When the handler is resumed, it will have the * existing masks plus any masks added through this call. Handlers * do not have partial suspensions. */virtual int register_handler (ACE_Event_Handler *event_handler, ACE_Reactor_Mask mask);ACE_Reactor_Mask声明于 <ace/Event_Handler.h> 中：enum{ LO_PRIORITY = 0, HI_PRIORITY = 10, NULL_MASK = 0,#if defined (ACE_USE_POLL) READ_MASK = POLLIN, WRITE_MASK = POLLOUT, EXCEPT_MASK = POLLPRI,#else /* USE SELECT */ READ_MASK = (1 << 0), WRITE_MASK = (1 << 1), EXCEPT_MASK = (1 << 2),#endif /* ACE_USE_POLL */ ACCEPT_MASK = (1 << 3), CONNECT_MASK = (1 << 4), TIMER_MASK = (1 << 5), QOS_MASK = (1 << 6), GROUP_QOS_MASK = (1 << 7), SIGNAL_MASK = (1 << 8), ALL_EVENTS_MASK = READ_MASK | WRITE_MASK | EXCEPT_MASK | ACCEPT_MASK | CONNECT_MASK | TIMER_MASK | QOS_MASK | GROUP_QOS_MASK | SIGNAL_MASK, RWE_MASK = READ_MASK | WRITE_MASK | EXCEPT_MASK, DONT_CALL = (1 << 9)};你可在 Service 类中，把每个事件处理对象与它感兴趣的事件关联起来： this->reactor()->register_handler(this, ACE_Event_Handler::READ_MASK);//关联virtual int handle_input (ACE_HANDLE fd = ACE_INVALID_HANDLE);回调函数。向 ACE_Reactor 类登记应用的事件处理对象： Service service; service.reactor(ACE_Reactor::instance());THREE：运行 ACE_Reactor 事件循环。 ACE_Reactor::instance()->run_reactor_event_loop(); //还有其它的几个循环函数，还没有具体研究可以看出，我们用的是一个 ACE_Reactor 单件，由 ACE_Object_Manager 管理它。
