Issue on serialize FTransform Property to byte stream

Development Pipeline & Plugins Editor Scripting
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1

I have made a UStruct like this:

USTRUCT(BlueprintType)
struct FTestLocation
{
	GENERATED_BODY()

	UPROPERTY()
	int32 Value = 0;

	UPROPERTY()
	FTransform Transfrom;

	UPROPERTY()
	float Value2 = 0;
};

And I am trying to serialize/deserialize with a Buffer.

FBufferArchive SavingStream;
FTestLocation SaveLocation;
SaveLocation.Value = 1;
SaveLocation.Transfrom.SetLocation({2.f, 2.f, 2.f});
SaveLocation.Value2 = 3.f;
FTestLocation::StaticStruct()->SerializeBin(SavingStream, &SaveLocation);

FBufferReader LoadingStream(SavingStream.GetData(), SavingStream.Num(), false);
FTestLocation LoadLocation;
FTestLocation::StaticStruct()->SerializeBin(LoadingStream, &LoadLocation);

The issue is: after the Loading process,

LoadLocation.Value is loaded correctly,

LoadLocation.Transfrom is not updated at all.

LoadLocation.Value2 is clearly a trash value.

Can anyone let me know what I did wrong?

2

You can create a operator<< on the struct, which will serialize and deserialize easily from any archive.

In the struct, declare:

friend FArchive& operator<< (FArchive& Ar, FTestLocation& Struct);

Then, write an implementation in the global scope (so without namespace::), in the .cpp:

FArchive& operator<< (FArchive& Ar, FTestLocation& Struct) {
   Ar << Struct.Value;
   Ar << Struct.Transfrom;
   Ar << Struct.Value2;
   return Ar;
}

With this, any FArchive will correctly, in the same order, serialize and deserialize your struct to/from binary, just call SomeFArchive << MyFTestLocation, thanks to the fact that almost all Unreal types, such as FTransform, FVector, etc. have the operator<< overloaded already. You don’t have to worry about their internal structure, sizeof, things like that at all.

3

Thanks for the reply, yes the solution you suggested could resolve my issue.
But what I am working on is a templated solution using SerializeBin to work on all the UStruct, so Ideally I’d love to have something works without adding any new code.

Also, I am new to Unreal Engine, I am not sure if I am not using SerializeBin correctly, or this is a bug on SerializeBin? (I am going to dig into the implementation a bit later.)

4

Found the issue by debugging into the SerializeBin implementation.

For the buffer Saved by FBufferArchive since it’s FMemoryWriter, I will need to use FMemoryReader to load it.

Change

FBufferReader LoadingStream(SavingStream.GetData(), SavingStream.Num(), false);

To

FMemoryReader LoadingStream(SavingStream);

Would resolve the issue.