RHICoreResourceCollection.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "RHIResources.h"
#include "RHIResourceCollection.h"
#include "RHICommandList.h"
#include "DynamicRHI.h"
#include "Containers/ResourceArray.h"
 
#if PLATFORM_SUPPORTS_BINDLESS_RENDERING
 
namespace UE::RHICore
{
    template<typename TType>
    inline size_t CalculateResourceCollectionMemorySize(TConstArrayView<TType> InValues)
    {
        return (1 + InValues.Num()) * sizeof(uint32);
    }
 
    inline FRHIDescriptorHandle GetHandleForResourceCollectionValue(const FRHIResourceCollectionMember& Member)
    {
        switch (Member.Type)
        {
        case FRHIResourceCollectionMember::EType::Texture:
            return static_cast<const FRHITexture*>(Member.Resource)->GetDefaultBindlessHandle();
        case FRHIResourceCollectionMember::EType::TextureReference:
            return static_cast<const FRHITextureReference*>(Member.Resource)->GetBindlessHandle();
        case FRHIResourceCollectionMember::EType::ShaderResourceView:
            return static_cast<const FRHIShaderResourceView*>(Member.Resource)->GetBindlessHandle();
        }
 
        return FRHIDescriptorHandle();
    }
 
    inline FRHIDescriptorHandle GetHandleForResourceCollectionValue(const FRHIDescriptorHandle& Handle)
    {
        return Handle;
    }
 
    inline void FillResourceCollectionUpdateMemory(uint32* Destination, TConstArrayView<FRHIResourceCollectionMember> InValues)
    {
        int32 WriteIndex = 0;
 
        for (const FRHIResourceCollectionMember& Value : InValues)
        {
            const FRHIDescriptorHandle Handle = GetHandleForResourceCollectionValue(Value);
            check(Handle.IsValid());
 
            const uint32 BindlessIndex = Handle.IsValid() ? Handle.GetIndex() : 0;
 
            Destination[WriteIndex] = BindlessIndex;
            ++WriteIndex;
        }
    }
 
    inline void FillResourceCollectionMemory(uint32* Destination, TConstArrayView<FRHIResourceCollectionMember> InValues)
    {
        Destination[0] = static_cast<uint32>(InValues.Num());
 
        FillResourceCollectionUpdateMemory(Destination + 1, InValues);
    }
 
    inline void FillResourceCollectionMemory(TRHIBufferInitializer<uint32>& Destination, TConstArrayView<FRHIResourceCollectionMember> InValues)
    {
        FillResourceCollectionMemory(Destination.GetWritableData(), InValues);
    }
 
    inline FRHIBuffer* CreateResourceCollectionBuffer(FRHICommandListBase& RHICmdList, TConstArrayView<FRHIResourceCollectionMember> InMembers)
    {
        const size_t BufferSize = UE::RHICore::CalculateResourceCollectionMemorySize(InMembers);
 
        const FRHIBufferCreateDesc CreateDesc =
            FRHIBufferCreateDesc::CreateByteAddress(TEXT("ResourceCollection"), BufferSize, sizeof(uint32))
            .AddUsage(EBufferUsageFlags::Static)
            .SetInitialState(ERHIAccess::SRVMask)
            .SetInitActionInitializer();
 
        TRHIBufferInitializer<uint32> Initializer = RHICmdList.CreateBufferInitializer(CreateDesc);
        UE::RHICore::FillResourceCollectionMemory(Initializer, InMembers);
 
        return Initializer.Finalize();
    }
 
    class FGenericResourceCollection : public FRHIResourceCollection
    {
    public:
        FGenericResourceCollection(FRHICommandListBase& RHICmdList, TConstArrayView<FRHIResourceCollectionMember> InMembers)
            : FRHIResourceCollection(InMembers)
            , Buffer(CreateResourceCollectionBuffer(RHICmdList, InMembers))
        {
            FRHIViewDesc::FBufferSRV::FInitializer ViewDesc = FRHIViewDesc::CreateBufferSRV().SetType(FRHIViewDesc::EBufferType::Raw);
            ShaderResourceView = RHICmdList.CreateShaderResourceView(Buffer, ViewDesc);
        }
 
        ~FGenericResourceCollection() = default;
 
        // FRHIResourceCollection
        virtual FRHIDescriptorHandle GetBindlessHandle() const final
        {
            return ShaderResourceView->GetBindlessHandle();
        }
        //~FRHIResourceCollection
 
        FRHIShaderResourceView* GetShaderResourceView() const
        {
            return ShaderResourceView;
        }
 
        TRefCountPtr<FRHIBuffer> Buffer;
        TRefCountPtr<FRHIShaderResourceView> ShaderResourceView;
    };
 
    inline FRHIResourceCollectionRef CreateGenericResourceCollection(FRHICommandListBase& RHICmdList, TConstArrayView<FRHIResourceCollectionMember> InMembers)
    {
        return new FGenericResourceCollection(RHICmdList, InMembers);
    }
 
    inline TConstArrayView<FRHIResourceCollectionMember> GetValidResourceCollectionUpdateList(FRHIResourceCollection* ResourceCollection, uint32 StartIndex, TConstArrayView<FRHIResourceCollectionMember> InUpdates)
    {
        const uint32 CollectionSize = ResourceCollection->GetMembers().Num();
        if (StartIndex >= CollectionSize)
        {
            // Invalid start index
            return {};
        }
 
        const int32 UpdateCount = FMath::Min<int32>(InUpdates.Num(), CollectionSize - StartIndex);
        return InUpdates.Left(UpdateCount);
    }
 
    inline void UpdateGenericResourceCollection(FRHICommandListBase& RHICmdList, FGenericResourceCollection* ResourceCollection, uint32 StartIndex, TConstArrayView<FRHIResourceCollectionMember> InMemberUpdates)
    {
        TConstArrayView<FRHIResourceCollectionMember> MemberUpdates = UE::RHICore::GetValidResourceCollectionUpdateList(ResourceCollection, StartIndex, InMemberUpdates);
        if (!MemberUpdates.IsEmpty())
        {
            // We can't reliably lock with offsets, so we will have to update the entire resource.
 
            ResourceCollection->UpdateMembers(StartIndex, MemberUpdates);
            TConstArrayView<FRHIResourceCollectionMember> Members = ResourceCollection->GetMembers();
 
            const uint32 UploadSize = UE::RHICore::CalculateResourceCollectionMemorySize(Members);
            uint32* UploadData = reinterpret_cast<uint32*>(RHICmdList.LockBuffer(ResourceCollection->Buffer, 0, UploadSize, RLM_WriteOnly));
 
            UE::RHICore::FillResourceCollectionMemory(UploadData, Members);
 
            RHICmdList.UnlockBuffer(ResourceCollection->Buffer);
        }
    }
}
 
#endif // PLATFORM_SUPPORTS_BINDLESS_RENDERING