131 lines
4.8 KiB
C++
131 lines
4.8 KiB
C++
// Copyright Epic Games, Inc. All Rights Reserved.
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#pragma once
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#include "Containers/UnrealString.h"
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#include "CoreMinimal.h"
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#include "CoreTypes.h"
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#include "IStructSerializerBackend.h"
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#include "Misc/EnumClassFlags.h"
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#include "Serialization/JsonWriter.h"
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#include "Templates/SharedPointer.h"
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#include "UObject/PropertyPortFlags.h"
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#include "UObject/UnrealType.h"
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class FArchive;
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/**
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* Implements a writer for UStruct serialization using Json.
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*
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* Note: The underlying Json serializer is currently hard-coded to use UCS2CHAR and pretty-print.
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* This is because the current JsonWriter API does not allow writers to be substituted since it's
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* all based on templates. At some point we will refactor the low-level Json API to provide more
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* flexibility for serialization.
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*/
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class FJsonStructSerializerBackend
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: public IStructSerializerBackend
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{
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public:
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/**
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* Creates and initializes a new legacy instance.
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* @note Deprecated, use the two-parameter constructor with EStructSerializerBackendFlags::Legacy if you need backwards compatibility with code compiled prior to 4.22.
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*
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* @param InArchive The archive to serialize into.
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*/
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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.")
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FJsonStructSerializerBackend( FArchive& InArchive )
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: JsonWriter(TJsonWriter<UCS2CHAR>::Create(&InArchive))
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, Flags(EStructSerializerBackendFlags::Legacy)
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{ }
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/**
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* Creates and initializes a new instance with the given flags.
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*
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* @param InArchive The archive to serialize into.
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* @param InFlags The flags that control the serialization behavior (typically EStructSerializerBackendFlags::Default).
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*/
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FJsonStructSerializerBackend( FArchive& InArchive, const EStructSerializerBackendFlags InFlags )
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: JsonWriter(TJsonWriter<UCS2CHAR>::Create(&InArchive))
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, Flags(InFlags)
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{ }
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public:
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// IStructSerializerBackend interface
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SERIALIZATION_API virtual void BeginArray(const FStructSerializerState& State) override;
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SERIALIZATION_API virtual void BeginStructure(const FStructSerializerState& State) override;
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SERIALIZATION_API virtual void EndArray(const FStructSerializerState& State) override;
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SERIALIZATION_API virtual void EndStructure(const FStructSerializerState& State) override;
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SERIALIZATION_API virtual void WriteComment(const FString& Comment) override;
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SERIALIZATION_API virtual void WriteProperty(const FStructSerializerState& State, int32 ArrayIndex = 0) override;
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SERIALIZATION_API virtual bool WritePODArray(const FStructSerializerState& State) override;
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protected:
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// Allow access to the internal JsonWriter to subclasses
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TSharedRef<TJsonWriter<UCS2CHAR>>& GetWriter()
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{
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return JsonWriter;
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}
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// Writes a property value to the serialization output.
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template<typename ValueType>
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void WritePropertyValue(const FStructSerializerState& State, const ValueType& Value)
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{
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//Write only value in case of no property or container elements
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if ((State.ValueProperty == nullptr) ||
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((State.ValueProperty->ArrayDim > 1
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|| State.ValueProperty->GetOwner<FArrayProperty>()
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|| State.ValueProperty->GetOwner<FSetProperty>()
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|| (State.ValueProperty->GetOwner<FMapProperty>() && State.KeyProperty == nullptr)) && !EnumHasAnyFlags(State.StateFlags, EStructSerializerStateFlags::WritingContainerElement)))
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{
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JsonWriter->WriteValue(Value);
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}
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//Write Key:Value in case of a map entry
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else if (State.KeyProperty != nullptr)
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{
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FString KeyString;
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State.KeyProperty->ExportTextItem_Direct(KeyString, State.KeyData, nullptr, nullptr, PPF_None);
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JsonWriter->WriteValue(KeyString, Value);
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}
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//Write PropertyName:Value for any other cases (single array element, single property, etc...)
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else
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{
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JsonWriter->WriteValue(State.ValueProperty->GetName(), Value);
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}
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}
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// Writes a null value to the serialization output.
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void WriteNull(const FStructSerializerState& State)
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{
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if ((State.ValueProperty == nullptr) ||
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((State.ValueProperty->ArrayDim > 1
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|| State.ValueProperty->GetOwner<FArrayProperty>()
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|| State.ValueProperty->GetOwner<FSetProperty>()
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|| (State.ValueProperty->GetOwner<FMapProperty>() && State.KeyProperty == nullptr)) && !EnumHasAnyFlags(State.StateFlags, EStructSerializerStateFlags::WritingContainerElement)))
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{
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JsonWriter->WriteNull();
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}
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else if (State.KeyProperty != nullptr)
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{
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FString KeyString;
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State.KeyProperty->ExportTextItem_Direct(KeyString, State.KeyData, nullptr, nullptr, PPF_None);
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JsonWriter->WriteNull(KeyString);
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}
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else
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{
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JsonWriter->WriteNull(State.ValueProperty->GetName());
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}
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}
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private:
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/** Holds the Json writer used for the actual serialization. */
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TSharedRef<TJsonWriter<UCS2CHAR>> JsonWriter;
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/** Flags controlling the serialization behavior. */
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EStructSerializerBackendFlags Flags;
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};
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