JsonStructSerializerBackend.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Containers/UnrealString.h"
#include "CoreMinimal.h"
#include "CoreTypes.h"
#include "IStructSerializerBackend.h"
#include "Misc/EnumClassFlags.h"
#include "Serialization/JsonWriter.h"
#include "Templates/SharedPointer.h"
#include "UObject/PropertyPortFlags.h"
#include "UObject/UnrealType.h"
 
class FArchive;
 
class FJsonStructSerializerBackend
    : public IStructSerializerBackend
{
public:
 
    UE_DEPRECATED(4.22, "Use the two-parameter constructor with EStructSerializerBackendFlags::Legacy only if you need backwards compatibility with code compiled prior to 4.22; otherwise use EStructSerializerBackendFlags::Default.")
    FJsonStructSerializerBackend( FArchive& InArchive )
        : JsonWriter(TJsonWriter<UCS2CHAR>::Create(&InArchive))
        , Flags(EStructSerializerBackendFlags::Legacy)
    { }
 
    FJsonStructSerializerBackend( FArchive& InArchive, const EStructSerializerBackendFlags InFlags )
        : JsonWriter(TJsonWriter<UCS2CHAR>::Create(&InArchive))
        , Flags(InFlags)
    { }
 
public:
 
    // IStructSerializerBackend interface
 
    SERIALIZATION_API virtual void BeginArray(const FStructSerializerState& State) override;
    SERIALIZATION_API virtual void BeginStructure(const FStructSerializerState& State) override;
    SERIALIZATION_API virtual void EndArray(const FStructSerializerState& State) override;
    SERIALIZATION_API virtual void EndStructure(const FStructSerializerState& State) override;
    SERIALIZATION_API virtual void WriteComment(const FString& Comment) override;
    SERIALIZATION_API virtual void WriteProperty(const FStructSerializerState& State, int32 ArrayIndex = 0) override;
    SERIALIZATION_API virtual bool WritePODArray(const FStructSerializerState& State) override;
 
protected:
 
    // Allow access to the internal JsonWriter to subclasses
    TSharedRef<TJsonWriter<UCS2CHAR>>& GetWriter()
    {
        return JsonWriter;
    }
 
    // Writes a property value to the serialization output.
    template<typename ValueType>
    void WritePropertyValue(const FStructSerializerState& State, const ValueType& Value)
    {
        //Write only value in case of no property or container elements
        if ((State.ValueProperty == nullptr) ||
            ((State.ValueProperty->ArrayDim > 1
                || State.ValueProperty->GetOwner<FArrayProperty>()
                || State.ValueProperty->GetOwner<FSetProperty>()
                || (State.ValueProperty->GetOwner<FMapProperty>() && State.KeyProperty == nullptr)) && !EnumHasAnyFlags(State.StateFlags, EStructSerializerStateFlags::WritingContainerElement)))
        {
            JsonWriter->WriteValue(Value);
        }
        //Write Key:Value in case of a map entry
        else if (State.KeyProperty != nullptr)
        {
            FString KeyString;
            State.KeyProperty->ExportTextItem_Direct(KeyString, State.KeyData, nullptr, nullptr, PPF_None);
            JsonWriter->WriteValue(KeyString, Value);
        }
        //Write PropertyName:Value for any other cases (single array element, single property, etc...)
        else
        {
            JsonWriter->WriteValue(State.ValueProperty->GetName(), Value);
        }
    }
 
    // Writes a null value to the serialization output.
    void WriteNull(const FStructSerializerState& State)
    {
        if ((State.ValueProperty == nullptr) ||
            ((State.ValueProperty->ArrayDim > 1
                || State.ValueProperty->GetOwner<FArrayProperty>()
                || State.ValueProperty->GetOwner<FSetProperty>()
                || (State.ValueProperty->GetOwner<FMapProperty>() && State.KeyProperty == nullptr)) && !EnumHasAnyFlags(State.StateFlags, EStructSerializerStateFlags::WritingContainerElement)))
        {
            JsonWriter->WriteNull();
        }
        else if (State.KeyProperty != nullptr)
        {
            FString KeyString;
            State.KeyProperty->ExportTextItem_Direct(KeyString, State.KeyData, nullptr, nullptr, PPF_None);
            JsonWriter->WriteNull(KeyString);
        }
        else
        {
            JsonWriter->WriteNull(State.ValueProperty->GetName());
        }
    }
 
private:
 
    TSharedRef<TJsonWriter<UCS2CHAR>> JsonWriter;
 
    EStructSerializerBackendFlags Flags;
};