Working with metadata (AtomsUnreal)

Metadatas are one of the basic entities in Atoms. They wrap basic data types and inherit the basic object AtomsCore::Metadata.

The basic Metadata class has functions to clone, copy, serialize etc.

These are the basic metadata type that can be used inside Atoms:

BoolMetadata
BoolArrayMetadata
IntMetadata
IntArrayMetadata
DoubleMetadata
DoubleArrayMetadata
Vector3Metadata
Vector3ArrayMetadata
EulerMetadata
EulerArrayMetadata
QuaternionMetadata
QuaternionArrayMetadata
MatrixMetadata
MatrixArrayMetadata
CurveMetadata
CurveArrayetadata
MeshMetadata
MeshArrayMetadata
ImageMetadata
PoseMetadata
SkeletonMetadata

These are container metadata types:

MapMetadata
ArrayMetadata

Unreal Specific metadata:

UnrealObjectMetadata (value is a TWeakObjectPtr - declared inside AtomsObjectMetadata.h)
UnrealObjectArrayMetadata (Array of TWeakObjectPtr - declared inside AtomsObjectMetadata.h)

Creating metadatas

You can create metadatas using the constructor of each type or you can use the metadata factory. Every metadata type has a unique typeId, it's used to register the metadata inside the metadata factory. Since the serialization code relies on this factory.

AtomsCore::IntMetadata intMeta(5);
AtomsCore::DoubleMetadata doubleMeta(654.4);

AtomsCore::MetadataFactory& factory = AtomsCore::MetadataFactory::instance();
AtomsPtr<AtomsCore::Metadata> data = factory.createMetadata(AtomsCore::Vector3Metadata::staticTypeId());

MapMetada

The MapMetadata is a map container for metadatas. It can store different metadata types at the same time. It uses strings as keys.

To insert data inside a MapMetadata use the addEntry function. This function can clone the input metadata or store directly the input smart pointer, increasing the reference counter.

AtomsCore::MapMetadata mapMeta;
// Insert element cloning the data
mapMeta.addEnetry("myKey1", &AtomsCore::IntMetadata(4));

AtomsPtr<AtomsCore::DoubleMetadata> doubleMeta(new AtomsCore::DoubleMetadata(5.7));
// Insert element cloning the data
mapMeta.addEntry("myKey2", std::static_pointer_cast<AtomsCore::Metadata>(doubleMeta), true);

AtomsPtr<AtomsCore::Vector3Metadata> vecMeta(new AtomsCore::Vector3Metadata(AtomsCore::Vector3(1,0,0));
// Insert element without cloning, copying the smart pointer and increasing the reference counter
mapMeta.addEntry("myKey3", std::static_pointer_cast<AtomsCore::Metadata>(vecMeta), false);

To get an entry from the map, use the getEntry or getTypedEntry function

AtomsPtr<AtomsCore::Vector3Metadata> vecData = mapMeta.getTypedEntry<AtomsCore::Vector3Metadata>("myKey3");
AtomsPtr<Metadata> intData = mapMeta.getEntry("myKey1");

ArrayMetadata

The array metadata is similar to the MapMetadata but it stores metadata in a vector rather than a map.

Creating a new metadata type

To create a new metadata type you must inherit the base Metadata class and register the new type in the metadata factory.

#include <AtomsCore/Metadata/MetadataImpl.h>

class FooData
{
public:
	float a;
	double b;
	char c;
};

typedef AtomsCore::MetadataImpl<FooData> FooMetadata;
template<> bool AtomsCore::MetadataImpl<FooData>::serialise(Archive& outStream) const;
template<> bool AtomsCore::MetadataImpl<FooData>::deserialise(Archive& inStream);
template<> size_t MetadataImpl<FooData>::memSize() const;
template<> void AtomsCore::MetadataImpl<FooData>::toString(std::stringstream& inStream) const;
template class AtomsCore::MetadataImpl<FooData>;

template<> std::string AtomsCore::MetadataImpl<FooData>::staticTypeStr() { return "FooMetadata"; } //!< Bool metadata static type
template<> unsigned int AtomsCore::MetadataImpl<FooData>::staticTypeId() { return  9999999; } //!< This must be a unique id

template<> bool AtomsCore::MetadataImpl<FooData>::serialise(Archive& outStream) const
{
	if (outStream.size == 0)
	{
		outStream.resize(memSize());
	}
	// the type id must be the first data to serialise
	outStream << typeId();
	outStream << m_value.a;
	outStream << m_value.b;
	outStream << m_value.c;
}
template<> bool AtomsCore::MetadataImpl<FooData>::deserialise(Archive& inStream)
{
	unsigned int typeIdValue;
	inStream >> typeIdValue;
	if (typeIdValue != staticTypeId())
		return false;
	inStream >> m_value.a;
	inStream >> m_value.b;
	inStream >> m_value.c;
	return true;
}

template<> void AtomsCore::MetadataImpl<FooData>::toString(std::stringstream& inStream) const
{
	inStream << "FooData: a - " << m_value.a << " b - " << m_value.b << " c - " << m_value.c;
}

template<> size_t TypedArrayMetadata<FooData>::memSize() const
	{
		return sizeof(unsigned int) + sizeof(float) + sizeof(double) + sizeof(char); //typeid + a + b + c 
	}


template class AtomsCore::MetadataImpl<FooData>;

void registerFooMetadata()
{
	MetadataFactory& factory = MetadataFactory::instance();
	factory.registerMetadata(FooMetadata::staticTypeStr(), FooMetadata::staticTypeId(), &FooMetadata::creator);
	
}