C++ FArchive::Preload方法代码示例

void UUserDefinedStruct::Serialize(FArchive& Ar)
{
	Super::Serialize( Ar );

	if (Ar.IsLoading() && (EUserDefinedStructureStatus::UDSS_UpToDate == Status))
	{
		// We need to force the editor data to be preload in case anyone needs to extract variable
		// information at editor time about the user structure.
		if ( EditorData != nullptr )
		{
			Ar.Preload(EditorData);
			if (!(Ar.GetPortFlags() & PPF_Duplicate))
			{
				FStructureEditorUtils::RecreateDefaultInstanceInEditorData(this);
			}
		}

		const FStructureEditorUtils::EStructureError Result = FStructureEditorUtils::IsStructureValid(this, NULL, &ErrorMessage);
		if (FStructureEditorUtils::EStructureError::Ok != Result)
		{
			Status = EUserDefinedStructureStatus::UDSS_Error;
			UE_LOG(LogClass, Log, TEXT("UUserDefinedStruct.Serialize '%s' validation: %s"), *GetName(), *ErrorMessage);
		}
	}
}

void UByteProperty::Serialize( FArchive& Ar )
{
	Super::Serialize( Ar );
	Ar << Enum;
	if (Enum != NULL)
	{
		Ar.Preload(Enum);
	}
}

/*-----------------------------------------------------------------------------
	UByteProperty.
-----------------------------------------------------------------------------*/
void UByteProperty::SerializeItem( FArchive& Ar, void* Value, void const* Defaults ) const
{
	if(Enum && Ar.UseToResolveEnumerators())
	{
		 const int32 ResolvedIndex = Enum->ResolveEnumerator(Ar, *(uint8*)Value);
		 *(uint8*)Value = static_cast<uint8>(ResolvedIndex);
		 return;
	}

	// Serialize enum values by name unless we're not saving or loading OR for backwards compatibility
	const bool bUseBinarySerialization = (Enum == NULL) || (!Ar.IsLoading() && !Ar.IsSaving());
	if( bUseBinarySerialization )
	{
		Super::SerializeItem(Ar, Value, Defaults);
	}
	// Loading
	else if (Ar.IsLoading())
	{
		FName EnumValueName;
		Ar << EnumValueName;
		// Make sure enum is properly populated
		if( Enum->HasAnyFlags(RF_NeedLoad) )
		{
			Ar.Preload(Enum);
		}

		// There's no guarantee EnumValueName is still present in Enum, in which case Value will be set to the enum's max value.
		// On save, it will then be serialized as NAME_None.
		int32 EnumIndex = Enum->FindEnumIndex(EnumValueName);
		if (EnumIndex == INDEX_NONE)
		{
			*(uint8*)Value = Enum->GetMaxEnumValue();
		}
		else
		{
			*(uint8*)Value = Enum->GetValueByIndex(EnumIndex);
		}
	}
	// Saving
	else
	{
		FName EnumValueName;
		uint8 ByteValue = *(uint8*)Value;

		// subtract 1 because the last entry in the enum's Names array
		// is the _MAX entry
		if ( Enum->IsValidEnumValue(ByteValue) )
		{
			EnumValueName = Enum->GetNameByValue(ByteValue);
		}
		else
		{
			EnumValueName = NAME_None;
		}
		Ar << EnumValueName;
	}
}

void UArrayProperty::LinkInternal(FArchive& Ar)
{
	ULinkerLoad* MyLinker = GetLinker();
	if( MyLinker )
	{
		MyLinker->Preload(this);
	}
	Ar.Preload(Inner);
	Inner->Link(Ar);
	Super::LinkInternal(Ar);
}

void UStructProperty::SerializeItem( FArchive& Ar, void* Value, int32 MaxReadBytes, void const* Defaults ) const
{
	const bool bUseBinarySerialization = UseBinarySerialization(Ar);
	const bool bUseNativeSerialization = UseNativeSerialization();

	// Preload struct before serialization tracking to not double count time.
	if ( bUseBinarySerialization || bUseNativeSerialization)
	{
		Ar.Preload( Struct );
	}

	bool bItemSerialized = false;
	if (bUseNativeSerialization)
	{
		UScriptStruct::ICppStructOps* CppStructOps = Struct->GetCppStructOps();
		check(CppStructOps); // else should not have STRUCT_SerializeNative
		check(!Struct->InheritedCppStructOps()); // else should not have STRUCT_SerializeNative
		bItemSerialized = CppStructOps->Serialize(Ar, Value);
	}

	if (!bItemSerialized)
	{
		if( bUseBinarySerialization )
		{
			// Struct is already preloaded above.
			if ( !Ar.IsPersistent() && Ar.GetPortFlags() != 0 && !Struct->ShouldSerializeAtomically(Ar) )
			{
				Struct->SerializeBinEx( Ar, Value, Defaults, Struct );
			}
			else
			{
				Struct->SerializeBin( Ar, Value, MaxReadBytes );
			}
		}
		else
		{
			Struct->SerializeTaggedProperties( Ar, (uint8*)Value, Struct, (uint8*)Defaults );
		}
	}

	if (Struct->StructFlags & STRUCT_PostSerializeNative)
	{
		UScriptStruct::ICppStructOps* CppStructOps = Struct->GetCppStructOps();
		check(CppStructOps); // else should not have STRUCT_PostSerializeNative
		check(!Struct->InheritedCppStructOps()); // else should not have STRUCT_PostSerializeNative
		CppStructOps->PostSerialize(Ar, Value);
	}
}

void UArrayProperty::SerializeItem( FArchive& Ar, void* Value, void const* Defaults ) const
{
	checkSlow(Inner);

	// Ensure that the Inner itself has been loaded before calling SerializeItem() on it
	Ar.Preload(Inner);

	FScriptArrayHelper ArrayHelper(this, Value);
	int32		n		= ArrayHelper.Num();
	Ar << n;
	if( Ar.IsLoading() )
	{
		ArrayHelper.EmptyAndAddValues(n);
	}
	ArrayHelper.CountBytes( Ar );

	for( int32 i=0; i<n; i++ )
	{
		Inner->SerializeItem( Ar, ArrayHelper.GetRawPtr(i) );
	}
}

void UStructProperty::LinkInternal(FArchive& Ar)
{
	// We potentially have to preload the property itself here, if we were the inner of an array property
	if(HasAnyFlags(RF_NeedLoad))
	{
		GetLinker()->Preload(this);
	}

#if !(UE_BUILD_SHIPPING || UE_BUILD_TEST)
	if (Struct == NULL)
	{
		UE_LOG(LogProperty, Error, TEXT("Struct type unknown for property '%s'; perhaps the USTRUCT() was renamed or deleted?"), *GetFullName());
	}
#endif

	// Preload is required here in order to load the value of Struct->PropertiesSize
	Ar.Preload(Struct);
	if ( !ensure(Struct) )
	{
		Struct = GetFallbackStruct();
	}
	PreloadInnerStructMembers(this);
	
	ElementSize = Align(Struct->PropertiesSize, Struct->GetMinAlignment());
	if (Struct->StructFlags & STRUCT_IsPlainOldData) // if there is nothing to construct or the struct is known to be memcpy-able, then allow memcpy
	{
		PropertyFlags |= CPF_IsPlainOldData;
	}
	if (Struct->StructFlags & STRUCT_NoDestructor)
	{
		PropertyFlags |= CPF_NoDestructor;
	}
	if (Struct->StructFlags & STRUCT_ZeroConstructor)
	{
		PropertyFlags |= CPF_ZeroConstructor;
	}
}

void UArrayProperty::SerializeItem( FArchive& Ar, void* Value, void const* Defaults ) const
{
	checkSlow(Inner);

	// Ensure that the Inner itself has been loaded before calling SerializeItem() on it
	Ar.Preload(Inner);

	FScriptArrayHelper ArrayHelper(this, Value);
	int32		n		= ArrayHelper.Num();
	Ar << n;
	if( Ar.IsLoading() )
	{
		// If using a custom property list, don't empty the array on load. Not all indices may have been serialized, so we need to preserve existing values at those slots.
		if (Ar.ArUseCustomPropertyList)
		{
			const int32 OldNum = ArrayHelper.Num();
			if (n > OldNum)
			{
				ArrayHelper.AddValues(n - OldNum);
			}
			else if (n < OldNum)
			{
				ArrayHelper.RemoveValues(n, OldNum - n);
			}
		}
		else
		{
			ArrayHelper.EmptyAndAddValues(n);
		}
	}
	ArrayHelper.CountBytes( Ar );

	// Serialize a PropertyTag for the inner property of this array, allows us to validate the inner struct to see if it has changed
	FPropertyTag InnerTag(Ar, Inner, 0, (uint8*)Value, (uint8*)Defaults);
	if (Ar.UE4Ver() >= VER_UE4_INNER_ARRAY_TAG_INFO && InnerTag.Type == NAME_StructProperty)
	{
		if (Ar.IsSaving())
		{
			Ar << InnerTag;
		}
		else if (Ar.IsLoading())
		{
			Ar << InnerTag;

			auto CanSerializeFromStructWithDifferentName = [](const FArchive& InAr, const FPropertyTag& PropertyTag, const UStructProperty* StructProperty)
			{
				return PropertyTag.StructGuid.IsValid()
					&& StructProperty 
					&& StructProperty->Struct 
					&& (PropertyTag.StructGuid == StructProperty->Struct->GetCustomGuid());
			};

			// Check if the Inner property can successfully serialize, the type may have changed
			UStructProperty* StructProperty = CastChecked<UStructProperty>(Inner);
			// if check redirector to make sure if the name has changed
			FName* NewName = FLinkerLoad::StructNameRedirects.Find(InnerTag.StructName);
			FName StructName = CastChecked<UStructProperty>(StructProperty)->Struct->GetFName();
			if (NewName != nullptr && *NewName == StructName)
			{
				InnerTag.StructName = *NewName;
			}

			if (InnerTag.StructName != StructProperty->Struct->GetFName()
				&& !CanSerializeFromStructWithDifferentName(Ar, InnerTag, StructProperty))
			{
				UE_LOG(LogClass, Warning, TEXT("Property %s of %s has a struct type mismatch (tag %s != prop %s) in package:  %s. If that struct got renamed, add an entry to ActiveStructRedirects."),
					*InnerTag.Name.ToString(), *GetName(), *InnerTag.StructName.ToString(), *CastChecked<UStructProperty>(Inner)->Struct->GetName(), *Ar.GetArchiveName());

#if WITH_EDITOR
				// Ensure the structure is initialized
				for (int32 i = 0; i < n; i++)
				{
					StructProperty->Struct->InitializeDefaultValue(ArrayHelper.GetRawPtr(i));
				}
#endif // WITH_EDITOR

				// Skip the property
				const int64 StartOfProperty = Ar.Tell();
				const int64 RemainingSize = InnerTag.Size - (Ar.Tell() - StartOfProperty);
				uint8 B;
				for (int64 i = 0; i < RemainingSize; i++)
				{
					Ar << B;
				}
				return;
			}
		}
	}

	// need to know how much data this call to SerializeItem consumes, so mark where we are
	int32 DataOffset = Ar.Tell();

	// If we're using a custom property list, first serialize any explicit indices
	int32 i = 0;
	bool bSerializeRemainingItems = true;
	bool bUsingCustomPropertyList = Ar.ArUseCustomPropertyList;
	if (bUsingCustomPropertyList && Ar.ArCustomPropertyList != nullptr)
	{
		// Initially we only serialize indices that are explicitly specified (in order)
		bSerializeRemainingItems = false;
//.........这里部分代码省略.........