RHIUniformBufferDataShared.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "RenderGraphResources.h"
 
namespace UE::RHICore
{
    struct FUniformDataReader
    {
        FUniformDataReader() = delete;
        FUniformDataReader(const void* InData) : Data(reinterpret_cast<const uint8*>(InData)) { }
 
        template<typename TResourceOut>
        const TResourceOut& Read(const FRHIUniformBufferResource& InResource) const
        {
            return *reinterpret_cast<const TResourceOut*>(Data + InResource.MemberOffset);
        }
 
        const uint8* Data;
    };
 
    inline FRHIDescriptorHandle GetBindlessResourceHandle(FUniformDataReader Reader, const FRHIUniformBufferResource& Resource)
    {
        switch (Resource.MemberType)
        {
        case UBMT_TEXTURE:
        {
            FRHITexture* Texture = Reader.Read<FRHITexture*>(Resource);
            return Texture ? Texture->GetDefaultBindlessHandle() : FRHIDescriptorHandle();
        }
        break;
        case UBMT_SRV:
        {
            FRHIShaderResourceView* ShaderResourceView = Reader.Read<FRHIShaderResourceView*>(Resource);
            return ShaderResourceView ? ShaderResourceView->GetBindlessHandle() : FRHIDescriptorHandle();
        }
        break;
        case UBMT_SAMPLER:
        {
            FRHISamplerState* SamplerState = Reader.Read<FRHISamplerState*>(Resource);
            return SamplerState ? SamplerState->GetBindlessHandle() : FRHIDescriptorHandle();
        }
        break;
        case UBMT_RESOURCE_COLLECTION:
        {
            FRHIResourceCollection* ResourceCollection = Reader.Read<FRHIResourceCollection*>(Resource);
            return ResourceCollection ? ResourceCollection->GetBindlessHandle() : FRHIDescriptorHandle();
        }
        break;
        case UBMT_RDG_TEXTURE:
        {
            FRDGTexture* RDGTexture = Reader.Read<FRDGTexture*>(Resource);
            FRHITexture* Texture = RDGTexture ? RDGTexture->GetRHI() : nullptr;
            return Texture ? Texture->GetDefaultBindlessHandle() : FRHIDescriptorHandle();
        }
        break;
        case UBMT_RDG_TEXTURE_SRV:
        case UBMT_RDG_TEXTURE_NON_PIXEL_SRV:
        case UBMT_RDG_BUFFER_SRV:
        {
            FRDGShaderResourceView* RDGShaderResourceView = Reader.Read<FRDGShaderResourceView*>(Resource);
            if (RDGShaderResourceView)
                RDGShaderResourceView->MarkResourceAsUsed();
 
            FRHIShaderResourceView* ShaderResourceView = RDGShaderResourceView ? RDGShaderResourceView->GetRHI() : nullptr;
            return ShaderResourceView ? ShaderResourceView->GetBindlessHandle() : FRHIDescriptorHandle();
        }
        break;
        case UBMT_UAV:
        {
            FRHIUnorderedAccessView* UnorderedAccessView = Reader.Read<FRHIUnorderedAccessView*>(Resource);
            return UnorderedAccessView ? UnorderedAccessView->GetBindlessHandle() : FRHIDescriptorHandle();
        }
        break;
        case UBMT_RDG_TEXTURE_UAV:
        case UBMT_RDG_BUFFER_UAV:
        {
            FRDGUnorderedAccessView* RDGUnorderedAccessView = Reader.Read<FRDGUnorderedAccessView*>(Resource);
            FRHIUnorderedAccessView* UnorderedAccessView = RDGUnorderedAccessView ? RDGUnorderedAccessView->GetRHI() : nullptr;
            return UnorderedAccessView ? UnorderedAccessView->GetBindlessHandle() : FRHIDescriptorHandle();
        }
        break;
 
        default:
            // Do nothing.
            break;
        }
        return FRHIDescriptorHandle();
    }
 
    inline void UpdateUniformBufferConstants(void* DestinationData, const void* SourceData, const FRHIUniformBufferLayout& Layout, bool bAllowBindless = true)
    {
        check(DestinationData != nullptr);
        check(SourceData != nullptr);
 
        // First copy wholesale
        FMemory::Memcpy(DestinationData, SourceData, Layout.ConstantBufferSize);
 
        if (bAllowBindless)
        {
            FUniformDataReader Reader(SourceData);
 
            // Then copy indices over
            for (const FRHIUniformBufferResource& Resource : Layout.Resources)
            {
                const FRHIDescriptorHandle Handle = GetBindlessResourceHandle(Reader, Resource);
                if (Handle.IsValid())
                {
                    const uint32 BindlessIndex = Handle.GetIndex();
                    FMemory::Memcpy(reinterpret_cast<uint8*>(DestinationData) + Resource.MemberOffset, &BindlessIndex, sizeof(BindlessIndex));
                }
            }
        }
    }
}