Factory.h

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// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
 
#include "Core/Types.h"
#include "Core/Group.h"
#ifdef CADKERNEL_DEV
#include "UI/DefineForDebug.h"
#endif
 
#include "Containers/List.h"
 
 
namespace UE::CADKernel
{
 
template<class ElementType>
class TFactory
{
    static const int32 MaxSize = 256;
 
protected:
    TDoubleLinkedList<TArray<ElementType>> StackOfEntitySet;
    TArray<ElementType*> FreeEntityStack;
#ifdef DEBUG_FACTORY
    int32 AllocatedElementNum = 0;
    int32 UsedElementNum = 0;
    int32 AvailableElementNum = 0;
#endif
 
private:
    void FillFreeEntityStack()
    {
        StackOfEntitySet.AddHead(TArray<ElementType>());
        TArray<ElementType>& EntityPool = StackOfEntitySet.GetHead()->GetValue();
        EntityPool.SetNum(MaxSize);
        for (ElementType& Entity : EntityPool)
        {
            FreeEntityStack.Add(&Entity);
        }
#ifdef DEBUG_FACTORY
        AllocatedElementNum += MaxSize;
#endif
    }
 
public:
    TFactory()
    {
        FreeEntityStack.Reserve(MaxSize);
    }
 
    void DeleteEntity(ElementType* Entity)
    {
        Entity->Clean();
        FreeEntityStack.Add(Entity);
#ifdef DEBUG_FACTORY
        UsedElementNum--;
        ensureCADKernel(UsedElementNum + FreeEntityStack.Num() == AllocatedElementNum);
#endif
    }
 
    ElementType& New()
    {
#ifdef DEBUG_FACTORY
        ensureCADKernel(UsedElementNum + FreeEntityStack.Num() == AllocatedElementNum);
#endif
        if (FreeEntityStack.IsEmpty())
        {
            FillFreeEntityStack();
        }
#ifdef DEBUG_FACTORY
        UsedElementNum++;
#endif
        return *FreeEntityStack.Pop(EAllowShrinking::No);
    }
};
} // namespace UE::CADKernel