callbackList.h

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/*********************************************************************************
** Copyright (c) 2020 MAK Technologies, Inc.
** All rights reserved.
*********************************************************************************/


#pragma once

#include <list>

namespace Legion
{
   template<typename Cb, typename... Param>
   class CallbackList
   {
   public:
      CallbackList()
         :myIsExecuting(false)
      {

      }

      ~CallbackList()
      {

      }

      bool add(Cb cb)
      {
         if (myIsExecuting)
         {
            myToAddCallbacks.push_back(cb);
            return true;
         }
         else
         {
            //protect against double add
            std::list<Cb>::iterator iter = std::find(myCallbacks.begin(), myCallbacks.end(), cb);
            if (iter == myCallbacks.end())
            {
               myCallbacks.push_back(cb);
            }
            else
            {
               return false;
            }

            return true;
         }
      }

      bool remove(Cb cb)
      {
         if (myIsExecuting)
         {
            myToRemoveCallbacks.push_back(cb);
         }
         else
         {
            myCallbacks.remove(cb);
         }

         return true;
      }

      void execute(Param... params)
      {
         myIsExecuting = true;
         std::list<Cb>::iterator iter = myCallbacks.begin();
         for (iter; iter != myCallbacks.end(); ++iter)
         {
            (*iter)(params...);
         }
         myIsExecuting = false;

         //if callbacks were added during execution, add them
         iter = myToAddCallbacks.begin();
         for (iter; iter != myToAddCallbacks.end(); ++iter)
         {
            add(*iter);
         }
         myToAddCallbacks.clear();

         //if callbacks were removed during execution, remove them
         iter = myToRemoveCallbacks.begin();
         for (iter; iter != myToRemoveCallbacks.end(); ++iter)
         {
            remove(*iter);
         }
         myToRemoveCallbacks.clear();
      }

   protected:
      std::list<Cb> myCallbacks;
      std::list<Cb> myToAddCallbacks;
      std::list<Cb> myToRemoveCallbacks;
      bool myIsExecuting;
   };

}