template<typename T>
class TTreeReaderValue< T >

An interface for reading values stored in ROOT columnar datasets.

The TTreeReaderValue is a type-safe tool to be used in association with a TTreeReader to access the values stored in TTree, TNtuple and TChain datasets. TTreeReaderValue can be also used to access collections such as std::vectors or TClonesArray stored in columnar datasets but it is recommended to use TTreeReaderArray instead as it offers several advantages.

See the documentation of TTreeReader for more details and examples.

Definition at line 205 of file TTreeReaderValue.h.

Public Types
typedef bool(ROOT::Detail::TBranchProxy::*	BranchProxyRead_t) ()
enum	EReadStatus { kReadSuccess = 0 , kReadNothingYet , kReadError }
enum	ESetupStatus { kSetupMatchButEntryBeyondEnd , kSetupMakeClassModeMismatch = -9 , kSetupTreeDestructed = -8 , kSetupNotSetup = -7 , kSetupMissingCounterBranch = -6 , kSetupMissingBranch = -5 , kSetupInternalError = -4 , kSetupMissingDictionary = -3 , kSetupMismatch = -2 , kSetupNotACollection = -1 , kSetupMatch , kSetupNoCheck = 5 , kSetupMatchLeaf = 6 , kSetupMatchBranch }
	Status flags, 0 is good. More...
using	NonConstT_t = typename std::remove_const<T>::type

Public Member Functions
	TTreeReaderValue ()=delete
	TTreeReaderValue (TTreeReader &tr, const char *branchname)
T *	Get ()
	Return a pointer to the value of the current entry.
void *	GetAddress ()
	Returns the memory address of the object being read.
const char *	GetBranchName () const
TLeaf *	GetLeaf ()
	If we are reading a leaf, return the corresponding TLeaf.
virtual EReadStatus	GetReadStatus () const
ESetupStatus	GetSetupStatus () const
	Return this TTreeReaderValue's setup status.
bool	IsValid () const
	Return true if the branch was setup and read correctly.
T &	operator* ()
	Return a reference to the value of the current entry.
T *	operator-> ()
	Return a pointer to the value of the current entry.
EReadStatus	ProxyRead ()
EReadStatus	ProxyReadDefaultImpl ()
template<BranchProxyRead_t Func>
ROOT::Internal::TTreeReaderValueBase::EReadStatus	ProxyReadTemplate ()
	Try to read the value from the TBranchProxy, returns the status of the read.

Protected Types
typedef EReadStatus(TTreeReaderValueBase::*	Read_t) ()

Protected Member Functions
virtual void	CreateProxy ()
	Create the proxy object for our branch.
void	ErrorAboutMissingProxyIfNeeded ()
const char *	GetDerivedTypeName () const override
	Get the template argument as a string.
Detail::TBranchProxy *	GetProxy () const
void	MarkTreeReaderUnavailable ()
void	NotifyNewTree (TTree *newTree)
	The TTreeReader has switched to a new TTree. Update the leaf.
void	RegisterWithTreeReader ()
	Register with tree reader.
TBranch *	SearchBranchWithCompositeName (TLeaf &myleaf, TDictionary &branchActualType, std::string &err)
	Search a branch the name of which contains a ".".

Static Protected Member Functions
static const char *	GetBranchDataType (TBranch branch, TDictionary &dict, TDictionary const *curDict)
	Retrieve the type of data stored by branch; put its dictionary into dict, return its type name.
static std::string	GetElementTypeName (const std::type_info &ti)
	Stringify the template argument.

Protected Attributes
TString	fBranchName
	Name of the branch to read data from.
TDictionary *	fDict
	Type that the branch should contain.
bool	fHaveLeaf: 1
	Whether the data is in a leaf.
bool	fHaveStaticClassOffsets: 1
	Whether !fStaticClassOffsets.empty().
TLeaf *	fLeaf = nullptr
TString	fLeafName
bool	fOpaqueRead {false}
	If true, the reader will not do any type-checking against the actual type held by the branch.
Detail::TBranchProxy *	fProxy = nullptr
	Proxy for this branch, owned by TTreeReader.
Read_t	fProxyReadFunc = &TTreeReaderValueBase::ProxyReadDefaultImpl
	! Pointer to the Read implementation to use.
EReadStatus	fReadStatus: 2
	Read status of this data access.
ESetupStatus	fSetupStatus = kSetupNotSetup
	Setup status of this data access.
std::vector< Long64_t >	fStaticClassOffsets
TTreeReader *	fTreeReader
	Tree reader we belong to.

#include <TTreeReaderValue.h>

Inheritance diagram for TTreeReaderValue< T >:

Member Typedef Documentation

◆ BranchProxyRead_t

typedef bool(ROOT::Detail::TBranchProxy::* ROOT::Internal::TTreeReaderValueBase::BranchProxyRead_t) ()

inherited

Definition at line 84 of file TTreeReaderValue.h.

◆ NonConstT_t

template<typename T>

using TTreeReaderValue< T >::NonConstT_t = typename std::remove_const<T>::type

Definition at line 209 of file TTreeReaderValue.h.

◆ Read_t

typedef EReadStatus(TTreeReaderValueBase::* ROOT::Internal::TTreeReaderValueBase::Read_t) ()

protectedinherited

Definition at line 143 of file TTreeReaderValue.h.

Member Enumeration Documentation

◆ EReadStatus

enum ROOT::Internal::TTreeReaderValueBase::EReadStatus

inherited

Enumerator
kReadSuccess	Data read okay.
kReadNothingYet	Data now yet accessed.
kReadError	Problem reading data.

Definition at line 74 of file TTreeReaderValue.h.

◆ ESetupStatus

enum ROOT::Internal::TTreeReaderValueBase::ESetupStatus

inherited

Status flags, 0 is good.

Enumerator
kSetupMatchButEntryBeyondEnd	This branch has been setup, branch data type and reader template type match, but nothing can be read because we have already reached the end of the tree.
kSetupMakeClassModeMismatch	readers disagree on whether TTree::SetMakeBranch() should be on
kSetupTreeDestructed	The TTreeReader has been destructed / not set.
kSetupNotSetup	No initialization has happened yet.
kSetupMissingCounterBranch	The array cannot find its counter branch: Array[CounterBranch].
kSetupMissingBranch	The specified branch cannot be found.
kSetupInternalError	Some other error - hopefully the error message helps.
kSetupMissingDictionary	To read this branch, we need a dictionary.
kSetupMismatch	Mismatch of branch type and reader template type.
kSetupNotACollection	The branch class type is not a collection.
kSetupMatch	This branch has been set up, branch data type and reader template type match, reading should succeed.
kSetupNoCheck
kSetupMatchLeaf	This branch (or TLeaf, really) has been set up, reading should succeed.
kSetupMatchBranch	This branch has been set up, branch data type and reader template type match, reading should succeed.

Definition at line 48 of file TTreeReaderValue.h.

Constructor & Destructor Documentation

◆ TTreeReaderValue() [1/2]

template<typename T>

TTreeReaderValue< T >::TTreeReaderValue ( )

delete

◆ TTreeReaderValue() [2/2]

template<typename T>

TTreeReaderValue< T >::TTreeReaderValue	(	TTreeReader &	tr,
		const char *	branchname )

inline

Definition at line 211 of file TTreeReaderValue.h.

Member Function Documentation

◆ CreateProxy()

void ROOT::Internal::TTreeReaderValueBase::CreateProxy ( )

protectedvirtualinherited

Create the proxy object for our branch.

Reimplemented in ROOT::Internal::TTreeReaderArrayBase.

Definition at line 462 of file TTreeReaderValue.cxx.

◆ ErrorAboutMissingProxyIfNeeded()

void ROOT::Internal::TTreeReaderValueBase::ErrorAboutMissingProxyIfNeeded ( )

protectedinherited

Definition at line 842 of file TTreeReaderValue.cxx.

◆ Get()

template<typename T>

T * TTreeReaderValue< T >::Get ( )

inline

Return a pointer to the value of the current entry.

Return a nullptr and print an error if no entry has been loaded yet. The returned address is guaranteed to stay constant while a given TTree is being read from a given file, unless the branch addresses are manipulated directly (e.g. through TTree::SetBranchAddress()). The address might also change when the underlying TTree/TFile is switched, e.g. when a TChain switches files.

Definition at line 221 of file TTreeReaderValue.h.

◆ GetAddress()

void * ROOT::Internal::TTreeReaderValueBase::GetAddress ( )

inherited

Returns the memory address of the object being read.

Definition at line 266 of file TTreeReaderValue.cxx.

◆ GetBranchDataType()

const char * ROOT::Internal::TTreeReaderValueBase::GetBranchDataType	(	TBranch *	branch,
		TDictionary *&	dict,
		TDictionary const *	curDict )

staticprotectedinherited

Retrieve the type of data stored by branch; put its dictionary into dict, return its type name.

If no dictionary is available, at least its type name should be returned.

Definition at line 713 of file TTreeReaderValue.cxx.

◆ GetBranchName()

const char * ROOT::Internal::TTreeReaderValueBase::GetBranchName ( ) const

inlineinherited

Definition at line 101 of file TTreeReaderValue.h.

◆ GetDerivedTypeName()

template<typename T>

const char * TTreeReaderValue< T >::GetDerivedTypeName ( ) const

inlineoverrideprotectedvirtual

Get the template argument as a string.

Implements ROOT::Internal::TTreeReaderValueBase.

Definition at line 243 of file TTreeReaderValue.h.

◆ GetElementTypeName()

std::string ROOT::Internal::TTreeReaderValueBase::GetElementTypeName ( const std::type_info & ti )

staticprotectedinherited

Stringify the template argument.

Definition at line 226 of file TTreeReaderValue.cxx.

◆ GetLeaf()

TLeaf * ROOT::Internal::TTreeReaderValueBase::GetLeaf ( )

inlineinherited

If we are reading a leaf, return the corresponding TLeaf.

Definition at line 97 of file TTreeReaderValue.h.

◆ GetProxy()

Detail::TBranchProxy * ROOT::Internal::TTreeReaderValueBase::GetProxy ( ) const

inlineprotectedinherited

Definition at line 119 of file TTreeReaderValue.h.

◆ GetReadStatus()

virtual EReadStatus ROOT::Internal::TTreeReaderValueBase::GetReadStatus ( ) const

inlinevirtualinherited

Reimplemented in ROOT::Internal::TTreeReaderArrayBase.

Definition at line 94 of file TTreeReaderValue.h.

◆ GetSetupStatus()

ESetupStatus ROOT::Internal::TTreeReaderValueBase::GetSetupStatus ( ) const

inlineinherited

Return this TTreeReaderValue's setup status.

Use this method to check e.g. whether the TTreeReaderValue is correctly setup and ready for reading.

Definition at line 93 of file TTreeReaderValue.h.

◆ IsValid()

bool ROOT::Internal::TTreeReaderValueBase::IsValid ( ) const

inlineinherited

Return true if the branch was setup and read correctly.

Use GetSetupStatus() to only check the setup status.

Definition at line 90 of file TTreeReaderValue.h.

◆ MarkTreeReaderUnavailable()

void ROOT::Internal::TTreeReaderValueBase::MarkTreeReaderUnavailable ( )

inlineprotectedinherited

Definition at line 121 of file TTreeReaderValue.h.

◆ NotifyNewTree()

void ROOT::Internal::TTreeReaderValueBase::NotifyNewTree ( TTree * newTree )

protectedinherited

The TTreeReader has switched to a new TTree. Update the leaf.

Definition at line 238 of file TTreeReaderValue.cxx.

◆ operator*()

template<typename T>

T & TTreeReaderValue< T >::operator* ( )

inline

Return a reference to the value of the current entry.

Equivalent to dereferencing the pointer returned by Get(). Behavior is undefined if no entry has been loaded yet. Most likely a crash will occur.

Definition at line 238 of file TTreeReaderValue.h.

◆ operator->()

template<typename T>

T * TTreeReaderValue< T >::operator-> ( )

inline

Return a pointer to the value of the current entry.

Equivalent to Get().

Definition at line 233 of file TTreeReaderValue.h.

◆ ProxyRead()

EReadStatus ROOT::Internal::TTreeReaderValueBase::ProxyRead ( )

inlineinherited

Definition at line 80 of file TTreeReaderValue.h.

◆ ProxyReadDefaultImpl()

ROOT::Internal::TTreeReaderValueBase::EReadStatus ROOT::Internal::TTreeReaderValueBase::ProxyReadDefaultImpl ( )

inherited

Definition at line 158 of file TTreeReaderValue.cxx.

◆ ProxyReadTemplate()

template<ROOT::Internal::TTreeReaderValueBase::BranchProxyRead_t Func>

ROOT::Internal::TTreeReaderValueBase::EReadStatus ROOT::Internal::TTreeReaderValueBase::ProxyReadTemplate ( )

inherited

Try to read the value from the TBranchProxy, returns the status of the read.

Definition at line 148 of file TTreeReaderValue.cxx.

◆ RegisterWithTreeReader()

void ROOT::Internal::TTreeReaderValueBase::RegisterWithTreeReader ( )

protectedinherited

Register with tree reader.

Definition at line 134 of file TTreeReaderValue.cxx.

◆ SearchBranchWithCompositeName()

TBranch * ROOT::Internal::TTreeReaderValueBase::SearchBranchWithCompositeName	(	TLeaf *&	myLeaf,
		TDictionary *&	branchActualType,
		std::string &	errMsg )

protectedinherited

Search a branch the name of which contains a ".".

Parameters

[out]	myLeaf	The leaf identified by the name if found (can be untouched).
[out]	branchActualType	Dictionary associated to the type of the leaf (can be untouched).
[out]	errMsg	The error message (can be untouched).

Returns: The address of the branch if found, nullptr otherwise This method allows to efficiently search for branches which have names which contain "dots", for example "w.v.a" or "v.a". Therefore, it allows to support names such as v.a where the branch was created with this syntax:
myTree->Branch("v", &v, "a/I:b:/I")

v
@ v
Definition rootcling_impl.cxx:3554

The method has some side effects, namely it can modify fSetupStatus, fProxy and fStaticClassOffsets/fHaveStaticClassOffsets.

Definition at line 315 of file TTreeReaderValue.cxx.

Member Data Documentation

◆ fBranchName

TString ROOT::Internal::TTreeReaderValueBase::fBranchName

protectedinherited

Name of the branch to read data from.

Definition at line 136 of file TTreeReaderValue.h.

◆ fDict

TDictionary* ROOT::Internal::TTreeReaderValueBase::fDict

protectedinherited

Type that the branch should contain.

Definition at line 139 of file TTreeReaderValue.h.

◆ fHaveLeaf

bool ROOT::Internal::TTreeReaderValueBase::fHaveLeaf

protectedinherited

Whether the data is in a leaf.

Definition at line 132 of file TTreeReaderValue.h.

◆ fHaveStaticClassOffsets

bool ROOT::Internal::TTreeReaderValueBase::fHaveStaticClassOffsets

protectedinherited

Whether !fStaticClassOffsets.empty().

Definition at line 133 of file TTreeReaderValue.h.

◆ fLeaf

TLeaf* ROOT::Internal::TTreeReaderValueBase::fLeaf = nullptr

protectedinherited

Definition at line 141 of file TTreeReaderValue.h.

◆ fLeafName

TString ROOT::Internal::TTreeReaderValueBase::fLeafName

protectedinherited

Definition at line 137 of file TTreeReaderValue.h.

◆ fOpaqueRead

bool ROOT::Internal::TTreeReaderValueBase::fOpaqueRead {false}

protectedinherited

If true, the reader will not do any type-checking against the actual type held by the branch.

Useful to just check if the current entry can be read or not without caring about its value.

Note: Only used by TTreeReaderOpaqueValue.

Definition at line 151 of file TTreeReaderValue.h.

◆ fProxy

Detail::TBranchProxy* ROOT::Internal::TTreeReaderValueBase::fProxy = nullptr

protectedinherited

Proxy for this branch, owned by TTreeReader.

Definition at line 140 of file TTreeReaderValue.h.

◆ fProxyReadFunc

Read_t ROOT::Internal::TTreeReaderValueBase::fProxyReadFunc = &TTreeReaderValueBase::ProxyReadDefaultImpl

protectedinherited

! Pointer to the Read implementation to use.

Definition at line 144 of file TTreeReaderValue.h.

◆ fReadStatus

EReadStatus ROOT::Internal::TTreeReaderValueBase::fReadStatus

protectedinherited

Read status of this data access.

Definition at line 134 of file TTreeReaderValue.h.

◆ fSetupStatus

ESetupStatus ROOT::Internal::TTreeReaderValueBase::fSetupStatus = kSetupNotSetup

protectedinherited

Setup status of this data access.

Definition at line 135 of file TTreeReaderValue.h.

◆ fStaticClassOffsets

std::vector<Long64_t> ROOT::Internal::TTreeReaderValueBase::fStaticClassOffsets

protectedinherited

Definition at line 142 of file TTreeReaderValue.h.

◆ fTreeReader

TTreeReader* ROOT::Internal::TTreeReaderValueBase::fTreeReader

protectedinherited

Tree reader we belong to.

Definition at line 138 of file TTreeReaderValue.h.

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

tree/dataframe/inc/ROOT/RDF/RTreeColumnReader.hxx
tree/treeplayer/inc/TTreeReaderValue.h

Public Types

Public Member Functions

Protected Types

Protected Member Functions

Static Protected Member Functions

Protected Attributes

Member Typedef Documentation

◆ BranchProxyRead_t

◆ NonConstT_t

◆ Read_t

Member Enumeration Documentation

◆ EReadStatus

◆ ESetupStatus

Constructor & Destructor Documentation

◆ TTreeReaderValue() [1/2]

◆ TTreeReaderValue() [2/2]

Member Function Documentation

◆ CreateProxy()

◆ ErrorAboutMissingProxyIfNeeded()

◆ Get()

◆ GetAddress()

◆ GetBranchDataType()

◆ GetBranchName()

◆ GetDerivedTypeName()

◆ GetElementTypeName()

◆ GetLeaf()

◆ GetProxy()

◆ GetReadStatus()

◆ GetSetupStatus()

◆ IsValid()

◆ MarkTreeReaderUnavailable()

◆ NotifyNewTree()

◆ operator*()

◆ operator->()

◆ ProxyRead()

◆ ProxyReadDefaultImpl()

◆ ProxyReadTemplate()

◆ RegisterWithTreeReader()

◆ SearchBranchWithCompositeName()

Member Data Documentation

◆ fBranchName

◆ fDict

◆ fHaveLeaf

◆ fHaveStaticClassOffsets

◆ fLeaf

◆ fLeafName

◆ fOpaqueRead

◆ fProxy

◆ fProxyReadFunc

◆ fReadStatus

◆ fSetupStatus

◆ fStaticClassOffsets

◆ fTreeReader