VVMTree.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#if WITH_VERSE_VM || defined(__INTELLISENSE__)
 
#include "VerseVM/VVMWriteBarrier.h"
 
namespace Verse
{
template <typename DerivedType>
struct TIntrusiveTree
{
    TWriteBarrier<DerivedType> Parent;
    TWriteBarrier<DerivedType> LastChild;
    TWriteBarrier<DerivedType> Prev;
    TWriteBarrier<DerivedType> Next;
 
    TIntrusiveTree(FAccessContext Context, DerivedType* Parent)
        : Parent(Context, Parent)
    {
        if (Parent)
        {
            if (Parent->LastChild)
            {
                Prev.Set(Context, Parent->LastChild.Get());
                Parent->LastChild->Next.Set(Context, This());
            }
            Parent->LastChild.Set(Context, This());
        }
    }
 
    template <bool bTransactional>
    void Detach(FAllocationContext Context)
    {
        if (Parent && Parent->LastChild.Get() == This())
        {
            V_DIE_IF(Next);
            Parent->LastChild.template Set<bTransactional>(Context, Prev.Get());
        }
        if (Prev)
        {
            V_DIE_UNLESS(Prev->Next.Get() == This());
            Prev->Next.template Set<bTransactional>(Context, Next.Get());
        }
        if (Next)
        {
            V_DIE_UNLESS(Next->Prev.Get() == This());
            Next->Prev.template Set<bTransactional>(Context, Prev.Get());
        }
        Prev.template Reset<bTransactional>(Context);
        Next.template Reset<bTransactional>(Context);
    }
 
    void Detach(FAllocationContext Context)
    {
        Detach<false>(::MoveTemp(Context));
    }
 
    void DetachTransactionally(FAllocationContext Context)
    {
        Detach<true>(::MoveTemp(Context));
    }
 
    // Visit each element of the subtree rooted at `this`.
    template <typename FunctionType>
    void ForEach(FunctionType&& Function)
    {
        if (LIKELY(!LastChild.Get()))
        {
            Function(*This());
            return;
        }
 
        TArray<DerivedType*> ToVisit;
        ToVisit.Push(This());
        while (ToVisit.Num())
        {
            DerivedType* Derived = ToVisit.Pop();
            Function(*Derived);
            for (DerivedType* Child = Derived->LastChild.Get(); Child; Child = Child->Prev.Get())
            {
                ToVisit.Push(Child);
            }
        }
    }
 
    DerivedType* This()
    {
        return static_cast<DerivedType*>(this);
    }
 
    template <typename TVisitor>
    void VisitReferencesImpl(TVisitor& Visitor)
    {
        Visitor.Visit(Parent, TEXT("Parent"));
        Visitor.Visit(LastChild, TEXT("LastChild"));
        Visitor.Visit(Prev, TEXT("Prev"));
        Visitor.Visit(Next, TEXT("Next"));
    }
};
} // namespace Verse
 
#endif