RHICoreBufferInitializer.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Containers/ResourceArray.h"
#include "RHIBufferInitializer.h"
#include "RHICore.h"
#include "RHICommandList.h"
#include "RHICoreInitializerCommon.h"
 
namespace UE::RHICore
{
    // Buffer initializer that just returns the buffer on finalize.
    struct FDefaultBufferInitializer : public FRHIBufferInitializer
    {
        FDefaultBufferInitializer(FRHICommandListBase& RHICmdList, FRHIBuffer* Buffer, void* InWritableData, uint64 InWritableSize)
            : FRHIBufferInitializer(RHICmdList, Buffer, InWritableData, InWritableSize,
                [Buffer = TRefCountPtr<FRHIBuffer>(Buffer)](FRHICommandListBase&) mutable
                {
                    return MoveTemp(Buffer);
                }
            )
        {
        }
 
        FDefaultBufferInitializer(FRHICommandListBase& RHICmdList, FRHIBuffer* Buffer)
            : FDefaultBufferInitializer(RHICmdList, Buffer, nullptr, 0)
        {
        }
    };
 
    // Buffer initializer that calls Lock on creation and Unlock on finalize.
    struct FLockBufferInitializer : public FRHIBufferInitializer
    {
        FLockBufferInitializer(FRHICommandListBase& RHICmdList, FRHIBuffer* Buffer)
            : FRHIBufferInitializer(
                RHICmdList,
                Buffer,
                RHICmdList.LockBuffer(Buffer, 0, Buffer->GetDesc().Size, RLM_WriteOnly),
                Buffer->GetDesc().Size,
                [Buffer = TRefCountPtr<FRHIBuffer>(Buffer)](FRHICommandListBase& RHICmdList) mutable
                {
                    RHICmdList.UnlockBuffer(Buffer);
                    return MoveTemp(Buffer);
                })
        {
        }
    };
 
    // Buffer initializer with custom implementation. This type is necessary for access to the FRHIBufferInitializer protected constructor.
    struct FCustomBufferInitializer : public FRHIBufferInitializer
    {
        FCustomBufferInitializer(FRHICommandListBase& RHICmdList, FRHIBuffer* Buffer, void* InWritableData, uint64 InWritableSize, FFinalizeCallback&& Func)
            : FRHIBufferInitializer(RHICmdList, Buffer, InWritableData, InWritableSize, Forward<FFinalizeCallback>(Func))
        {
        }
    };
 
    class FInvalidBuffer : public FRHIBuffer
    {
    public:
        FInvalidBuffer(const FRHIBufferCreateDesc& CreateDesc)
            : FRHIBuffer(CreateDesc)
        {
        }
    };
 
    static FRHIBufferInitializer HandleUnknownBufferInitializerInitAction(FRHICommandListBase& RHICmdList, const FRHIBufferCreateDesc& CreateDesc)
    {
        UE_LOG(LogRHICore, Fatal, TEXT("Unknown or unhandled ERHIBufferInitAction: %d"), static_cast<uint32>(CreateDesc.InitAction));
 
        FInvalidBuffer* Buffer = new FInvalidBuffer(CreateDesc);
        return UE::RHICore::FDefaultBufferInitializer(RHICmdList, Buffer);
    }
 
    // Create a buffer initializer for a unified memory platform. Any init actions not handled before here will use default implementations.
    static FRHIBufferInitializer CreateUnifiedMemoryBufferInitializer(
        FRHICommandListBase& RHICmdList
        , const FRHIBufferCreateDesc& CreateDesc
        , FRHIBuffer* Buffer
        , void* WritableData
    )
    {
        if (CreateDesc.InitAction == ERHIBufferInitAction::Default)
        {
            // Use the default buffer implementation, so just return the buffer on finalize.
            return UE::RHICore::FDefaultBufferInitializer(RHICmdList, Buffer);
        }
 
        if (CreateDesc.InitAction == ERHIBufferInitAction::ResourceArray)
        {
            // Write the data from the resource array immediately, discard the resource array and then return the buffer on finalize.
            check(CreateDesc.InitialData);
 
            FMemory::Memcpy(WritableData, CreateDesc.InitialData->GetResourceData(), CreateDesc.InitialData->GetResourceDataSize());
 
            // Discard the resource array's contents.
            CreateDesc.InitialData->Discard();
 
            return UE::RHICore::FDefaultBufferInitializer(RHICmdList, Buffer);
        }
 
        if (CreateDesc.InitAction == ERHIBufferInitAction::Zeroed)
        {
            // Zero memory immediately and return the buffer on finalize
            FMemory::Memzero(WritableData, CreateDesc.Size);
            return UE::RHICore::FDefaultBufferInitializer(RHICmdList, Buffer);
        }
 
        // Let the caller fill in the writable data.
        if (CreateDesc.InitAction == ERHIBufferInitAction::Initializer)
        {
            return UE::RHICore::FDefaultBufferInitializer(RHICmdList, Buffer, WritableData, CreateDesc.Size);
        }
 
        return UE::RHICore::HandleUnknownBufferInitializerInitAction(RHICmdList, CreateDesc);
    }
}