text: /*
   *    Copyright (c) 2017, The OpenThread Authors.
   *    All rights reserved.
   *
   *    Redistribution and use in source and binary forms, with or without
   *    modification, are permitted provided that the following conditions are met:
   *    1. Redistributions of source code must retain the above copyright
   *       notice, this list of conditions and the following disclaimer.
   *    2. Redistributions in binary form must reproduce the above copyright
   *       notice, this list of conditions and the following disclaimer in the
   *       documentation and/or other materials provided with the distribution.
   *    3. Neither the name of the copyright holder nor the
   *       names of its contributors may be used to endorse or promote products
   *       derived from this software without specific prior written permission.
   *
   *    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   *    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   *    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   *    ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
   *    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   *    CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   *    SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   *    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   *    CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   *    ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   *    POSSIBILITY OF SUCH DAMAGE.
   */
  
  #ifndef OTBR_COMMON_EVENT_EMITTER_HPP_
  #define OTBR_COMMON_EVENT_EMITTER_HPP_
  
  #include "openthread-br/config.h"
  
  #include <list>
  #include <map>
  
  #include <stdarg.h>
  
  namespace otbr {
  
  /**
   * This class implements the basic functionality of an event emitter.
   *
   */
  class EventEmitter
  {
      /**
       * This function pointer will be called when the @p aEvent is emitted.
       *
       * @param[in]   aContext    A pointer to application-specific context.
       * @param[in]   aEvent      The emitted event id.
       * @param[in]   aArguments  The arguments associated with this event.
       *
       */
      typedef void (*Callback)(void *aContext, int aEvent, va_list aArguments);
  
  public:
      /**
       * This method register an event handler for @p aEvent.
       *
       * @param[in]   aEvent      The event id.
       * @param[in]   aCallback   The function poiner to be called.
       * @param[in]   aContext    A pointer to application-specific context.
       *
       */
      void On(int aEvent, Callback aCallback, void *aContext);
  
      /**
       * This method deregister an event handler for @p aEvent.
       *
       * @param[in]   aEvent      The event id.
       * @param[in]   aCallback   The function poiner to be called.
       * @param[in]   aContext    A pointer to application-specific context.
       *
       */
      void Off(int aEvent, Callback aCallback, void *aContext);
  
      /**
       * This method emits an event.
       *
       * @param[in]   aEvent      The event id.
       *
       */
      void Emit(int aEvent, ...);
  
  private:
      typedef std::pair<Callback, void *> Handler;
      typedef std::list<Handler>          Handlers;
      typedef std::map<int, Handlers>     Events;
      Events                              mEvents;
  };
  
  } // namespace otbr
  
  #endif // OTBR_COMMON_EVENT_EMITTER_HPP_
  