callbackList.h

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/*********************************************************************************
** Copyright (c) 2021 MAK Technologies, Inc.
** All rights reserved.
*********************************************************************************/


#pragma once

#include <list>
#include <algorithm>

namespace Legion
{
   template<typename Cb, typename... Param>
   class CallbackList
   {
   public:
      CallbackList()
         :myEntryLevel(0)
      {

      }

      ~CallbackList()
      {

      }

      bool add(Cb cb)
      {
         if (myEntryLevel > 0)
         {
            myToAddCallbacks.push_back(cb);
            return true;
         }
         else
         {
            //protect against double add
            typename 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 (myEntryLevel > 0)
         {
            myToRemoveCallbacks.push_back(cb);
         }
         else
         {
            myCallbacks.remove(cb);
         }

         return true;
      }

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

         //if we are truly done, stop executing, and clear any deferred lists
         if (myEntryLevel == 0)
         {
            //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;
      int myEntryLevel;
   };

}