PreshaderTypes.h

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// Copyright Epic Games, Inc. All Rights Reserved.
#pragma once
 
#include "Shader/ShaderTypes.h"
#include "Containers/ArrayView.h"
 
namespace UE
{
namespace Shader
{
 
struct FPreshaderType
{
    FPreshaderType() = default;
    FPreshaderType(const FType& InType);
    FPreshaderType(EValueType InType);
 
    bool IsStruct() const { return StructTypeHash != 0u; }
    int32 GetNumComponents() const { return StructTypeHash != 0u ? StructComponentTypes.Num() : GetValueTypeDescription(ValueType).NumComponents; }
    EValueComponentType GetComponentType(int32 Index) const;
 
    uint64 StructTypeHash = 0u;
    TArrayView<const EValueComponentType> StructComponentTypes;
    EValueType ValueType = EValueType::Void;
};
 
struct FPreshaderValue
{
    FPreshaderType Type;
    TArrayView<FValueComponent> Component;
 
    FValue AsShaderValue(const FStructTypeRegistry* TypeRegistry = nullptr) const;
};
 
class FPreshaderStack
{
public:
    int32 Num() const { return Values.Num(); }
 
    void CheckEmpty() const
    {
        check(Values.Num() == 0);
        check(Components.Num() == 0);
    }
 
    void PushValue(const FValue& InValue);
    void PushValue(const FPreshaderValue& InValue);
    void PushValue(const FPreshaderType& InType, TArrayView<const FValueComponent> InComponents);
    TArrayView<FValueComponent> PushEmptyValue(const FPreshaderType& InType);
    FValueComponent* PushEmptyValue(EValueType InType, int32 NumComponents);
 
    FPreshaderValue PopValue();
    FPreshaderValue PeekValue(int32 Offset = 0);
 
    inline const FPreshaderType& PeekType()
    {
        return Values.Last();
    }
    inline FValueComponent* PeekComponents(int32 NumComponents)
    {
        return &Components[Components.Num() - NumComponents];
    }
 
    void PopResult(FPreshaderValue& OutValue);
 
    inline void OverrideTopType(EValueType ValueType)
    {
        check(!Values.Last().IsStruct());
        Values.Last().ValueType = ValueType;
    }
 
    inline void MergeTopTwoValues(EValueType ValueType, int32 ComponentsConsumed)
    {
        Values.RemoveAt(Values.Num() - 1, EAllowShrinking::No);
        Components.RemoveAt(Components.Num() - ComponentsConsumed, ComponentsConsumed, EAllowShrinking::No);
        Values.Last().ValueType = ValueType;
    }
 
    // Adjust component count, by adding or removing components by the specified amount
    inline void AdjustComponentCount(int32 NumComponentChange)
    {
        if (NumComponentChange > 0)
        {
            Components.AddUninitialized(NumComponentChange);
        }
        else if (NumComponentChange < 0)
        {
            Components.RemoveAt(Components.Num() + NumComponentChange, -NumComponentChange, EAllowShrinking::No);
        }
    }
 
    void Reset()
    {
        Values.Reset();
        Components.Reset();
    }
 
private:
    TArray<FPreshaderType, TNonRelocatableInlineAllocator<8>> Values;
    TArray<FValueComponent, TNonRelocatableInlineAllocator<64>> Components;
};
 
} // namespace Shader
} // namespace UE