Template specializations for C++ std::variant.

The generic field for std::variant types

Definition at line 330 of file RFieldSTLMisc.hxx.

Classes
class	RVariantDeleter

Public Member Functions
	RVariantField (RVariantField &&other)=default

	RVariantField (std::string_view fieldName, std::vector< std::unique_ptr< RFieldBase > > itemFields)

	~RVariantField () override=default

size_t	GetAlignment () const final
	As a rule of thumb, the alignment is equal to the size of the type.

size_t	GetValueSize () const final
	The number of bytes taken by a value of the appropriate type.

RVariantField &	operator= (RVariantField &&other)=default

Public Member Functions inherited from ROOT::Experimental::RFieldBase
	RFieldBase (const RFieldBase &)=delete

	RFieldBase (RFieldBase &&)=default

	RFieldBase (std::string_view name, std::string_view type, ENTupleStructure structure, bool isSimple, std::size_t nRepetitions=0)
	The constructor creates the underlying column objects and connects them to either a sink or a source.

virtual	~RFieldBase ()=default

virtual void	AcceptVisitor (Detail::RFieldVisitor &visitor) const

RSchemaIterator	begin ()

RConstSchemaIterator	begin () const

RValue	BindValue (std::shared_ptr< void > objPtr)
	Creates a value from a memory location with an already constructed object.

RConstSchemaIterator	cbegin () const

RConstSchemaIterator	cend () const

std::unique_ptr< RFieldBase >	Clone (std::string_view newName) const
	Copies the field and its sub fields using a possibly new name and a new, unconnected set of columns.

RBulk	CreateBulk ()
	The returned bulk is initially empty; RBulk::ReadBulk will construct the array of values.

template<>
std::unique_ptr< void, typename RFieldBase::RCreateObjectDeleter< void >::deleter >	CreateObject () const

template<typename T >
std::unique_ptr< T, typename RCreateObjectDeleter< T >::deleter >	CreateObject () const
	Generates an object of the field type and allocates new initialized memory according to the type.

template<>
std::unique_ptr< void, typename ROOT::Experimental::RFieldBase::RCreateObjectDeleter< void >::deleter >	CreateObject () const

RValue	CreateValue ()
	Generates an object of the field type and wraps the created object in a shared pointer and returns it an RValue connected to the field.

RSchemaIterator	end ()

RConstSchemaIterator	end () const

RColumnRepresentations::Selection_t	GetColumnRepresentatives () const
	Returns the fColumnRepresentative pointee or, if unset, the field's default representative.

const std::string &	GetDescription () const
	Get the field's description.

const std::string &	GetFieldName () const

virtual std::uint32_t	GetFieldVersion () const
	Indicates an evolution of the mapping scheme from C++ type to columns.

std::size_t	GetNRepetitions () const

DescriptorId_t	GetOnDiskId () const

std::uint32_t	GetOnDiskTypeChecksum () const
	Return checksum stored in the field descriptor; only valid after a call to `ConnectPageSource()`, if the field stored a type checksum.

std::uint32_t	GetOnDiskTypeVersion () const
	Return the C++ type version stored in the field descriptor; only valid after a call to `ConnectPageSource()`

const RFieldBase *	GetParent () const

std::string	GetQualifiedFieldName () const
	Returns the field name and parent field names separated by dots ("grandparent.parent.child")

EState	GetState () const

ENTupleStructure	GetStructure () const

std::vector< RFieldBase * >	GetSubFields ()

std::vector< const RFieldBase * >	GetSubFields () const

int	GetTraits () const

const std::string &	GetTypeAlias () const

virtual std::uint32_t	GetTypeChecksum () const
	Return the current TClass reported checksum of this class. Only valid if kTraitTypeChecksum is set.

const std::string &	GetTypeName () const

virtual std::uint32_t	GetTypeVersion () const
	Indicates an evolution of the C++ type itself.

bool	HasDefaultColumnRepresentative () const
	Whether or not an explicit column representative was set.

bool	HasReadCallbacks () const

bool	IsSimple () const

RFieldBase &	operator= (const RFieldBase &)=delete

RFieldBase &	operator= (RFieldBase &&)=default

void	SetColumnRepresentatives (const RColumnRepresentations::Selection_t &representatives)
	Fixes a column representative.

void	SetDescription (std::string_view description)

void	SetOnDiskId (DescriptorId_t id)

virtual std::vector< RValue >	SplitValue (const RValue &value) const
	Creates the list of direct child values given a value for this field.

Protected Member Functions
std::size_t	AppendImpl (const void *from) final
	Operations on values of complex types, e.g.

std::unique_ptr< RFieldBase >	CloneImpl (std::string_view newName) const final
	Called by Clone(), which additionally copies the on-disk ID.

void	CommitClusterImpl () final

void	ConstructValue (void *where) const final
	Constructs value in a given location of size at least GetValueSize(). Called by the base class' CreateValue().

void	GenerateColumns () final
	Implementations in derived classes should create the backing columns corresponsing to the field type for writing.

void	GenerateColumns (const RNTupleDescriptor &desc) final
	Implementations in derived classes should create the backing columns corresponsing to the field type for reading.

const RColumnRepresentations &	GetColumnRepresentations () const final
	Implementations in derived classes should return a static RColumnRepresentations object.

std::unique_ptr< RDeleter >	GetDeleter () const final

void	ReadGlobalImpl (NTupleSize_t globalIndex, void *to) final

Protected Member Functions inherited from ROOT::Experimental::RFieldBase
size_t	AddReadCallback (ReadCallback_t func)
	Set a user-defined function to be called after reading a value, giving a chance to inspect and/or modify the value object.

std::size_t	Append (const void *from)
	Write the given value into columns.

void	Attach (std::unique_ptr< RFieldBase > child)
	Add a new subfield to the list of nested fields.

void	AutoAdjustColumnTypes (const RNTupleWriteOptions &options)
	When connecting a field to a page sink, the field's default column representation is subject to adjustment according to the write options.

void *	CreateObjectRawPtr () const
	Factory method for the field's type. The caller owns the returned pointer.

const ColumnRepresentation_t &	EnsureCompatibleColumnTypes (const RNTupleDescriptor &desc, std::uint16_t representationIndex) const
	Returns the on-disk column types found in the provided descriptor for fOnDiskId and the given representation index.

template<typename... ColumnCppTs>
void	GenerateColumnsImpl ()
	For writing, use the currently set column representative.

template<std::uint32_t ColumnIndexT, typename HeadT , typename... TailTs>
void	GenerateColumnsImpl (const ColumnRepresentation_t &representation, std::uint16_t representationIndex)
	Helpers for generating columns.

template<typename... ColumnCppTs>
void	GenerateColumnsImpl (const RNTupleDescriptor &desc)
	For reading, use the on-disk column list.

virtual RExtraTypeInfoDescriptor	GetExtraTypeInfo () const

virtual bool	HasExtraTypeInfo () const

virtual void	OnConnectPageSource ()
	Called by `ConnectPageSource()` once connected; derived classes may override this as appropriate.

void	Read (NTupleSize_t globalIndex, void *to)
	Populate a single value with data from the field.

void	Read (RClusterIndex clusterIndex, void *to)
	Populate a single value with data from the field.

std::size_t	ReadBulk (const RBulkSpec &bulkSpec)
	Returns the number of newly available values, that is the number of bools in bulkSpec.fMaskAvail that flipped from false to true.

virtual std::size_t	ReadBulkImpl (const RBulkSpec &bulkSpec)
	General implementation of bulk read.

virtual void	ReadInClusterImpl (RClusterIndex clusterIndex, void *to)

void	RemoveReadCallback (size_t idx)

Private Member Functions
	RVariantField (std::string_view name, const RVariantField &source)

Static Private Member Functions
static std::uint8_t	GetTag (const void *variantPtr, std::size_t tagOffset)
	Extracts the index from an std::variant and transforms it into the 1-based index used for the switch column The implementation supports two memory layouts that are in use: a trailing unsigned byte, zero-indexed, having the exception caused empty state encoded by the max tag value, or a trailing unsigned int instead of a char.

static std::string	GetTypeList (const std::vector< std::unique_ptr< RFieldBase > > &itemFields)

static void	SetTag (void *variantPtr, std::size_t tagOffset, std::uint8_t tag)

Private Attributes
size_t	fMaxAlignment = 1

size_t	fMaxItemSize = 0

std::vector< ClusterSize_t::ValueType >	fNWritten

size_t	fTagOffset = 0
	In the std::variant memory layout, at which byte number is the index stored.

size_t	fVariantOffset = 0
	In the std::variant memory layout, the actual union of types may start at an offset > 0.

Static Private Attributes
static constexpr std::size_t	kMaxVariants = 125

Additional Inherited Members
Public Types inherited from ROOT::Experimental::RFieldBase
using	ColumnRepresentation_t = std::vector<EColumnType>

enum class	EState { kUnconnected , kConnectedToSink , kConnectedToSource }
	During its lifetime, a field undergoes the following possible state transitions: More...

using	RConstSchemaIterator = RSchemaIteratorTemplate<true>

using	RSchemaIterator = RSchemaIteratorTemplate<false>

Static Public Member Functions inherited from ROOT::Experimental::RFieldBase
static std::vector< RCheckResult >	Check (const std::string &fieldName, const std::string &typeName)
	Checks if the given type is supported by RNTuple.

static RResult< std::unique_ptr< RFieldBase > >	Create (const std::string &fieldName, const std::string &typeName)
	Factory method to resurrect a field from the stored on-disk type information.

Static Public Attributes inherited from ROOT::Experimental::RFieldBase
static constexpr std::uint32_t	kInvalidTypeVersion = -1U

static constexpr int	kTraitMappable = 0x04
	A field of a fundamental type that can be directly mapped via `RField<T>::Map()`, i.e.

static constexpr int	kTraitTriviallyConstructible = 0x01
	No constructor needs to be called, i.e.

static constexpr int	kTraitTriviallyDestructible = 0x02
	The type is cleaned up just by freeing its memory. I.e. the destructor performs a no-op.

static constexpr int	kTraitTrivialType = kTraitTriviallyConstructible \| kTraitTriviallyDestructible
	Shorthand for types that are both trivially constructible and destructible.

static constexpr int	kTraitTypeChecksum = 0x08
	The TClass checksum is set and valid.

Static Protected Member Functions inherited from ROOT::Experimental::RFieldBase
static std::size_t	CallAppendOn (RFieldBase &other, const void *from)
	Allow derived classes to call Append and Read on other (sub) fields.

static void	CallConstructValueOn (const RFieldBase &other, void *where)
	Allow derived classes to call ConstructValue(void *) and GetDeleter on other (sub) fields.

static void *	CallCreateObjectRawPtrOn (RFieldBase &other)

static void	CallReadOn (RFieldBase &other, NTupleSize_t globalIndex, void *to)

static void	CallReadOn (RFieldBase &other, RClusterIndex clusterIndex, void *to)

static RResult< std::unique_ptr< RFieldBase > >	Create (const std::string &fieldName, const std::string &canonicalType, const std::string &typeAlias, bool continueOnError=false)
	Factory method to resurrect a field from the stored on-disk type information.

static std::unique_ptr< RDeleter >	GetDeleterOf (const RFieldBase &other)

static Internal::RColumn *	GetPrincipalColumnOf (const RFieldBase &other)
	Fields may need direct access to the principal column of their sub fields, e.g. in RRVecField::ReadBulk.

Protected Attributes inherited from ROOT::Experimental::RFieldBase
Internal::RColumn *	fAuxiliaryColumn = nullptr
	Some fields have a second column in its column representation.

std::vector< std::unique_ptr< Internal::RColumn > >	fAvailableColumns
	The columns are connected either to a sink or to a source (not to both); they are owned by the field.

std::vector< std::reference_wrapper< const ColumnRepresentation_t > >	fColumnRepresentatives
	Pointers into the static vector GetColumnRepresentations().GetSerializationTypes() when SetColumnRepresentatives is called.

std::uint32_t	fOnDiskTypeChecksum = 0
	TClass checksum cached from the descriptor after a call to `ConnectPageSource()`.

std::uint32_t	fOnDiskTypeVersion = kInvalidTypeVersion
	C++ type version cached from the descriptor after a call to `ConnectPageSource()`

RFieldBase *	fParent
	Sub fields point to their mother field.

Internal::RColumn *	fPrincipalColumn = nullptr
	All fields that have columns have a distinct main column.

std::vector< ReadCallback_t >	fReadCallbacks
	List of functions to be called after reading a value.

std::vector< std::unique_ptr< RFieldBase > >	fSubFields
	Collections and classes own sub fields.

int	fTraits = 0
	Properties of the type that allow for optimizations of collections of that type.

std::string	fTypeAlias
	A typedef or using name that was used when creating the field.

#include <ROOT/RField/RFieldSTLMisc.hxx>

Inheritance diagram for ROOT::Experimental::RVariantField:

[legend]

Constructor & Destructor Documentation

◆ RVariantField() [1/3]

ROOT::Experimental::RVariantField::RVariantField	(	std::string_view	name,
		const RVariantField &	source )

private

Definition at line 3434 of file RField.cxx.

◆ RVariantField() [2/3]

ROOT::Experimental::RVariantField::RVariantField	(	std::string_view	fieldName,
		std::vector< std::unique_ptr< RFieldBase > >	itemFields )

Definition at line 3447 of file RField.cxx.

◆ RVariantField() [3/3]

ROOT::Experimental::RVariantField::RVariantField ( RVariantField && other )

default

◆ ~RVariantField()

ROOT::Experimental::RVariantField::~RVariantField ( )

overridedefault

Member Function Documentation

◆ AppendImpl()

std::size_t ROOT::Experimental::RVariantField::AppendImpl ( const void * from )

finalprotectedvirtual

Operations on values of complex types, e.g.

ones that involve multiple columns or for which no direct column type exists.

Reimplemented from ROOT::Experimental::RFieldBase.

Definition at line 3500 of file RField.cxx.

◆ CloneImpl()

std::unique_ptr< ROOT::Experimental::RFieldBase > ROOT::Experimental::RVariantField::CloneImpl ( std::string_view newName ) const

finalprotectedvirtual

Called by Clone(), which additionally copies the on-disk ID.

Implements ROOT::Experimental::RFieldBase.

Definition at line 3481 of file RField.cxx.

◆ CommitClusterImpl()

void ROOT::Experimental::RVariantField::CommitClusterImpl ( )

finalprotectedvirtual

Reimplemented from ROOT::Experimental::RFieldBase.

Definition at line 3588 of file RField.cxx.

◆ ConstructValue()

void ROOT::Experimental::RVariantField::ConstructValue ( void * where ) const

finalprotectedvirtual

Constructs value in a given location of size at least GetValueSize(). Called by the base class' CreateValue().

Implements ROOT::Experimental::RFieldBase.

Definition at line 3549 of file RField.cxx.

◆ GenerateColumns() [1/2]

void ROOT::Experimental::RVariantField::GenerateColumns ( )

finalprotectedvirtual

Implementations in derived classes should create the backing columns corresponsing to the field type for writing.

The default implementation does not attach any columns to the field.

Reimplemented from ROOT::Experimental::RFieldBase.

Definition at line 3539 of file RField.cxx.

◆ GenerateColumns() [2/2]

void ROOT::Experimental::RVariantField::GenerateColumns ( const RNTupleDescriptor & )

finalprotectedvirtual

Implementations in derived classes should create the backing columns corresponsing to the field type for reading.

The default implementation does not attach any columns to the field. The method should check, using the page source and fOnDiskId, if the column types match and throw if they don't.

Reimplemented from ROOT::Experimental::RFieldBase.

Definition at line 3544 of file RField.cxx.

◆ GetAlignment()

size_t ROOT::Experimental::RVariantField::GetAlignment ( ) const

finalvirtual

As a rule of thumb, the alignment is equal to the size of the type.

There are, however, various exceptions to this rule depending on OS and CPU architecture. So enforce the alignment to be explicitly spelled out.

Implements ROOT::Experimental::RFieldBase.

Definition at line 3575 of file RField.cxx.

◆ GetColumnRepresentations()

const ROOT::Experimental::RFieldBase::RColumnRepresentations & ROOT::Experimental::RVariantField::GetColumnRepresentations ( ) const

finalprotectedvirtual

Implementations in derived classes should return a static RColumnRepresentations object.

The default implementation does not attach any columns to the field.

Reimplemented from ROOT::Experimental::RFieldBase.

Definition at line 3533 of file RField.cxx.

◆ GetDeleter()

std::unique_ptr< ROOT::Experimental::RFieldBase::RDeleter > ROOT::Experimental::RVariantField::GetDeleter ( ) const

finalprotectedvirtual

Reimplemented from ROOT::Experimental::RFieldBase.

Definition at line 3565 of file RField.cxx.

◆ GetTag()

std::uint8_t ROOT::Experimental::RVariantField::GetTag	(	const void *	variantPtr,
		std::size_t	tagOffset )

staticprivate

Extracts the index from an std::variant and transforms it into the 1-based index used for the switch column The implementation supports two memory layouts that are in use: a trailing unsigned byte, zero-indexed, having the exception caused empty state encoded by the max tag value, or a trailing unsigned int instead of a char.

Definition at line 3486 of file RField.cxx.

◆ GetTypeList()

std::string ROOT::Experimental::RVariantField::GetTypeList ( const std::vector< std::unique_ptr< RFieldBase > > & itemFields )

staticprivate

Definition at line 3423 of file RField.cxx.

◆ GetValueSize()

size_t ROOT::Experimental::RVariantField::GetValueSize ( ) const

finalvirtual

The number of bytes taken by a value of the appropriate type.

Implements ROOT::Experimental::RFieldBase.

Definition at line 3580 of file RField.cxx.

◆ operator=()

RVariantField & ROOT::Experimental::RVariantField::operator= ( RVariantField && other )

default

◆ ReadGlobalImpl()

void ROOT::Experimental::RVariantField::ReadGlobalImpl	(	NTupleSize_t	globalIndex,
		void *	to )

finalprotectedvirtual

Reimplemented from ROOT::Experimental::RFieldBase.

Definition at line 3514 of file RField.cxx.

◆ SetTag()

void ROOT::Experimental::RVariantField::SetTag	(	void *	variantPtr,
		std::size_t	tagOffset,
		std::uint8_t	tag )

staticprivate

Definition at line 3493 of file RField.cxx.

Member Data Documentation

◆ fMaxAlignment

size_t ROOT::Experimental::RVariantField::fMaxAlignment = 1

private

Definition at line 354 of file RFieldSTLMisc.hxx.

◆ fMaxItemSize

size_t ROOT::Experimental::RVariantField::fMaxItemSize = 0

private

Definition at line 353 of file RFieldSTLMisc.hxx.

◆ fNWritten

std::vector<ClusterSize_t::ValueType> ROOT::Experimental::RVariantField::fNWritten

private

Definition at line 359 of file RFieldSTLMisc.hxx.

◆ fTagOffset

size_t ROOT::Experimental::RVariantField::fTagOffset = 0

private

In the std::variant memory layout, at which byte number is the index stored.

Definition at line 356 of file RFieldSTLMisc.hxx.

◆ fVariantOffset

size_t ROOT::Experimental::RVariantField::fVariantOffset = 0

private

In the std::variant memory layout, the actual union of types may start at an offset > 0.

Definition at line 358 of file RFieldSTLMisc.hxx.

◆ kMaxVariants

constexpr std::size_t ROOT::Experimental::RVariantField::kMaxVariants = 125

staticconstexprprivate

Definition at line 336 of file RFieldSTLMisc.hxx.

Libraries for ROOT::Experimental::RVariantField:

[legend]

The documentation for this class was generated from the following files:

tree/ntuple/v7/inc/ROOT/RField/RFieldSTLMisc.hxx
tree/ntuple/v7/src/RField.cxx

Classes

Public Member Functions

Protected Member Functions

Private Member Functions

Static Private Member Functions

Private Attributes

Static Private Attributes

Additional Inherited Members

Constructor & Destructor Documentation

◆ RVariantField() [1/3]

◆ RVariantField() [2/3]

◆ RVariantField() [3/3]

◆ ~RVariantField()

Member Function Documentation

◆ AppendImpl()

◆ CloneImpl()

◆ CommitClusterImpl()

◆ ConstructValue()

◆ GenerateColumns() [1/2]

◆ GenerateColumns() [2/2]

◆ GetAlignment()

◆ GetColumnRepresentations()

◆ GetDeleter()

◆ GetTag()

◆ GetTypeList()

◆ GetValueSize()

◆ operator=()

◆ ReadGlobalImpl()

◆ SetTag()

Member Data Documentation

◆ fMaxAlignment

◆ fMaxItemSize

◆ fNWritten

◆ fTagOffset

◆ fVariantOffset

◆ kMaxVariants