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TTreeReader Class Reference


A simple, robust and fast interface to read values from ROOT columnar datasets such as TTree, TChain or TNtuple

TTreeReader is associated to TTreeReaderValue and TTreeReaderArray which are handles to concretely access the information in the dataset.

Example code can be found in

You can generate a skeleton of TTreeReaderValue<T> and TTreeReaderArray<T> declarations for all of a tree's branches using TTree::MakeSelector().

Roottest contains an example showing the full power.

A simpler analysis example can be found below: it histograms a function of the px and py branches.

// A simple TTreeReader use: read data from hsimple.root (written by hsimple.C)
#include "TFile.h"
#include "TH1F.h"
#include "TTreeReader.h"
void hsimpleReader() {
// Create a histogram for the values we read.
TH1F("h1", "ntuple", 100, -4, 4);
// Open the file containing the tree.
TFile *myFile = TFile::Open("$ROOTSYS/tutorials/hsimple.root");
// Create a TTreeReader for the tree, for instance by passing the
// TTree's name and the TDirectory / TFile it is in.
TTreeReader myReader("ntuple", myFile);
// The branch "px" contains floats; access them as myPx.
TTreeReaderValue<Float_t> myPx(myReader, "px");
// The branch "py" contains floats, too; access those as myPy.
TTreeReaderValue<Float_t> myPy(myReader, "py");
// Loop over all entries of the TTree or TChain.
while (myReader.Next()) {
// Just access the data as if myPx and myPy were iterators (note the '*'
// in front of them):
myHist->Fill(*myPx + *myPy);
}
myHist->Draw();
}

A more complete example including error handling and a few combinations of TTreeReaderValue and TTreeReaderArray would look like this:

#include <TFile.h>
#include <TH1.h>
#include <TTreeReader.h>
#include "TriggerInfo.h"
#include "Muon.h"
#include "Tau.h"
#include <vector>
#include <iostream>
bool CheckValue(ROOT::Internal::TTreeReaderValueBase& value) {
if (value->GetSetupStatus() < 0) {
std::cerr << "Error " << value->GetSetupStatus()
<< "setting up reader for " << value->GetBranchName() << '\n';
return false;
}
return true;
}
// Analyze the tree "MyTree" in the file passed into the function.
// Returns false in case of errors.
bool analyze(TFile* file) {
// Create a TTreeReader named "MyTree" from the given TDirectory.
// The TTreeReader gives access to the TTree to the TTreeReaderValue and
// TTreeReaderArray objects. It knows the current entry number and knows
// how to iterate through the TTree.
TTreeReader reader("MyTree", file);
// Read a single float value in each tree entries:
TTreeReaderValue<float> weight(reader, "event.weight");
// Read a TriggerInfo object from the tree entries:
TTreeReaderValue<TriggerInfo> triggerInfo(reader, "triggerInfo");
//Read a vector of Muon objects from the tree entries:
TTreeReaderValue<std::vector<Muon>> muons(reader, "muons");
//Read the pT for all jets in the tree entry:
TTreeReaderArray<double> jetPt(reader, "jets.pT");
// Read the taus in the tree entry:
TTreeReaderArray<Tau> taus(reader, "taus");
// Now iterate through the TTree entries and fill a histogram.
TH1F("hist", "TTreeReader example histogram", 10, 0., 100.);
bool firstEntry = true;
while (reader.Next()) {
if (firstEntry) {
// Check that branches exist and their types match our expectation.
if (!CheckValue(weight)) return false;
if (!CheckValue(triggerInfo)) return false;
if (!CheckValue(muons)) return false;
if (!CheckValue(jetPt)) return false;
if (!CheckValue(taus)) return false;
firstentry = false;
}
// Access the TriggerInfo object as if it's a pointer.
if (!triggerInfo->hasMuonL1())
continue;
// Ditto for the vector<Muon>.
if (!muons->size())
continue;
// Access the jetPt as an array, whether the TTree stores this as
// a std::vector, std::list, TClonesArray or Jet* C-style array, with
// fixed or variable array size.
if (jetPt.GetSize() < 2 || jetPt[0] < 100)
continue;
// Access the array of taus.
if (!taus.IsEmpty()) {
// Access a float value - need to dereference as TTreeReaderValue
// behaves like an iterator
float currentWeight = *weight;
for (const Tau& tau: taus) {
hist->Fill(tau.eta(), currentWeight);
}
}
} // TTree entry / event loop
// Return true if we have iterated through all entries.
return reader.GetEntryStatus() == TTreeReader::kEntryBeyondEnd;
}

Definition at line 44 of file TTreeReader.h.

Classes

class  Iterator_t
 Iterate through the entries of a TTree. More...
 

Public Types

enum  EEntryStatus {
  kEntryValid = 0, kEntryNotLoaded, kEntryNoTree, kEntryNotFound,
  kEntryChainSetupError, kEntryChainFileError, kEntryDictionaryError, kEntryBeyondEnd,
  kEntryBadReader, kEntryUnknownError
}
 
enum  ELoadTreeStatus { kNoTree = 0, kLoadTreeNone, kInternalLoadTree, kExternalLoadTree }
 
typedef Iterator_t iterator
 
- Public Types inherited from TObject
enum  {
  kIsOnHeap = 0x01000000, kNotDeleted = 0x02000000, kZombie = 0x04000000, kInconsistent = 0x08000000,
  kBitMask = 0x00ffffff
}
 
enum  { kSingleKey = BIT(0), kOverwrite = BIT(1), kWriteDelete = BIT(2) }
 
enum  EDeprecatedStatusBits { kObjInCanvas = BIT(3) }
 
enum  EStatusBits {
  kCanDelete = BIT(0), kMustCleanup = BIT(3), kIsReferenced = BIT(4), kHasUUID = BIT(5),
  kCannotPick = BIT(6), kNoContextMenu = BIT(8), kInvalidObject = BIT(13)
}
 

Public Member Functions

 TTreeReader ()
 Default constructor. Call SetTree to connect to a TTree. More...
 
 TTreeReader (TTree *tree, TEntryList *entryList=nullptr)
 Access data from tree. More...
 
 TTreeReader (const char *keyname, TDirectory *dir, TEntryList *entryList=nullptr)
 Access data from the tree called keyname in the directory (e.g. More...
 
 TTreeReader (const char *keyname, TEntryList *entryList=nullptr)
 
 ~TTreeReader ()
 Tell all value readers that the tree reader does not exist anymore. More...
 
Iterator_t begin ()
 Return an iterator to the 0th TTree entry. More...
 
Iterator_t end () const
 Return an iterator beyond the last TTree entry. More...
 
Long64_t GetCurrentEntry () const
 Returns the index of the current entry being read. More...
 
Long64_t GetEntries () const
 Returns the number of entries of the TEntryList if one is provided, else of the TTree / TChain, independent of a range set by SetEntriesRange() by calling TTree/TChain::GetEntriesFast. More...
 
Long64_t GetEntries (Bool_t force)
 Returns the number of entries of the TEntryList if one is provided, else of the TTree / TChain, independent of a range set by SetEntriesRange(). More...
 
TEntryListGetEntryList () const
 
EEntryStatus GetEntryStatus () const
 
TTreeGetTree () const
 
Bool_t IsChain () const
 
Bool_t IsInvalid () const
 
Bool_t Notify ()
 Callback from TChain and TTree's LoadTree. More...
 
void SetTree (TTree *tree, TEntryList *entryList=nullptr)
 Set (or update) the which tree to read from. More...
 
void SetTree (const char *keyname, TEntryList *entryList=nullptr)
 
void SetTree (const char *keyname, TDirectory *dir, TEntryList *entryList=nullptr)
 Set (or update) the which tree to read from, passing the name of a tree in a directory. More...
 
Entry setters
Bool_t Next ()
 Move to the next entry (or index of the TEntryList if that is set). More...
 
EEntryStatus SetEntry (Long64_t entry)
 Set the next entry (or index of the TEntryList if that is set). More...
 
EEntryStatus SetLocalEntry (Long64_t entry)
 Set the next local tree entry. More...
 
EEntryStatus SetEntriesRange (Long64_t beginEntry, Long64_t endEntry)
 Set the begin and end entry numbers. More...
 
std::pair< Long64_t, Long64_tGetEntriesRange () const
 Get the begin and end entry numbers. More...
 
void Restart ()
 Restart a Next() loop from entry 0 (of TEntryList index 0 of fEntryList is set). More...
 
- Public Member Functions inherited from TObject
 TObject ()
 TObject constructor. More...
 
 TObject (const TObject &object)
 TObject copy ctor. More...
 
virtual ~TObject ()
 TObject destructor. More...
 
void AbstractMethod (const char *method) const
 Use this method to implement an "abstract" method that you don't want to leave purely abstract. More...
 
virtual void AppendPad (Option_t *option="")
 Append graphics object to current pad. More...
 
virtual void Browse (TBrowser *b)
 Browse object. May be overridden for another default action. More...
 
ULong_t CheckedHash ()
 Check and record whether this class has a consistent Hash/RecursiveRemove setup (*) and then return the regular Hash value for this object. More...
 
virtual const char * ClassName () const
 Returns name of class to which the object belongs. More...
 
virtual void Clear (Option_t *="")
 
virtual TObjectClone (const char *newname="") const
 Make a clone of an object using the Streamer facility. More...
 
virtual Int_t Compare (const TObject *obj) const
 Compare abstract method. More...
 
virtual void Copy (TObject &object) const
 Copy this to obj. More...
 
virtual void Delete (Option_t *option="")
 Delete this object. More...
 
virtual Int_t DistancetoPrimitive (Int_t px, Int_t py)
 Computes distance from point (px,py) to the object. More...
 
virtual void Draw (Option_t *option="")
 Default Draw method for all objects. More...
 
virtual void DrawClass () const
 Draw class inheritance tree of the class to which this object belongs. More...
 
virtual TObjectDrawClone (Option_t *option="") const
 Draw a clone of this object in the current selected pad for instance with: gROOT->SetSelectedPad(gPad). More...
 
virtual void Dump () const
 Dump contents of object on stdout. More...
 
virtual void Error (const char *method, const char *msgfmt,...) const
 Issue error message. More...
 
virtual void Execute (const char *method, const char *params, Int_t *error=0)
 Execute method on this object with the given parameter string, e.g. More...
 
virtual void Execute (TMethod *method, TObjArray *params, Int_t *error=0)
 Execute method on this object with parameters stored in the TObjArray. More...
 
virtual void ExecuteEvent (Int_t event, Int_t px, Int_t py)
 Execute action corresponding to an event at (px,py). More...
 
virtual void Fatal (const char *method, const char *msgfmt,...) const
 Issue fatal error message. More...
 
virtual TObjectFindObject (const char *name) const
 Must be redefined in derived classes. More...
 
virtual TObjectFindObject (const TObject *obj) const
 Must be redefined in derived classes. More...
 
virtual Option_tGetDrawOption () const
 Get option used by the graphics system to draw this object. More...
 
virtual const char * GetIconName () const
 Returns mime type name of object. More...
 
virtual const char * GetName () const
 Returns name of object. More...
 
virtual char * GetObjectInfo (Int_t px, Int_t py) const
 Returns string containing info about the object at position (px,py). More...
 
virtual Option_tGetOption () const
 
virtual const char * GetTitle () const
 Returns title of object. More...
 
virtual UInt_t GetUniqueID () const
 Return the unique object id. More...
 
virtual Bool_t HandleTimer (TTimer *timer)
 Execute action in response of a timer timing out. More...
 
virtual ULong_t Hash () const
 Return hash value for this object. More...
 
Bool_t HasInconsistentHash () const
 Return true is the type of this object is known to have an inconsistent setup for Hash and RecursiveRemove (i.e. More...
 
virtual void Info (const char *method, const char *msgfmt,...) const
 Issue info message. More...
 
virtual Bool_t InheritsFrom (const char *classname) const
 Returns kTRUE if object inherits from class "classname". More...
 
virtual Bool_t InheritsFrom (const TClass *cl) const
 Returns kTRUE if object inherits from TClass cl. More...
 
virtual void Inspect () const
 Dump contents of this object in a graphics canvas. More...
 
void InvertBit (UInt_t f)
 
virtual Bool_t IsEqual (const TObject *obj) const
 Default equal comparison (objects are equal if they have the same address in memory). More...
 
virtual Bool_t IsFolder () const
 Returns kTRUE in case object contains browsable objects (like containers or lists of other objects). More...
 
R__ALWAYS_INLINE Bool_t IsOnHeap () const
 
virtual Bool_t IsSortable () const
 
R__ALWAYS_INLINE Bool_t IsZombie () const
 
virtual void ls (Option_t *option="") const
 The ls function lists the contents of a class on stdout. More...
 
void MayNotUse (const char *method) const
 Use this method to signal that a method (defined in a base class) may not be called in a derived class (in principle against good design since a child class should not provide less functionality than its parent, however, sometimes it is necessary). More...
 
void Obsolete (const char *method, const char *asOfVers, const char *removedFromVers) const
 Use this method to declare a method obsolete. More...
 
void operator delete (void *ptr)
 Operator delete. More...
 
void operator delete[] (void *ptr)
 Operator delete []. More...
 
voidoperator new (size_t sz)
 
voidoperator new (size_t sz, void *vp)
 
voidoperator new[] (size_t sz)
 
voidoperator new[] (size_t sz, void *vp)
 
TObjectoperator= (const TObject &rhs)
 TObject assignment operator. More...
 
virtual void Paint (Option_t *option="")
 This method must be overridden if a class wants to paint itself. More...
 
virtual void Pop ()
 Pop on object drawn in a pad to the top of the display list. More...
 
virtual void Print (Option_t *option="") const
 This method must be overridden when a class wants to print itself. More...
 
virtual Int_t Read (const char *name)
 Read contents of object with specified name from the current directory. More...
 
virtual void RecursiveRemove (TObject *obj)
 Recursively remove this object from a list. More...
 
void ResetBit (UInt_t f)
 
virtual void SaveAs (const char *filename="", Option_t *option="") const
 Save this object in the file specified by filename. More...
 
virtual void SavePrimitive (std::ostream &out, Option_t *option="")
 Save a primitive as a C++ statement(s) on output stream "out". More...
 
void SetBit (UInt_t f, Bool_t set)
 Set or unset the user status bits as specified in f. More...
 
void SetBit (UInt_t f)
 
virtual void SetDrawOption (Option_t *option="")
 Set drawing option for object. More...
 
virtual void SetUniqueID (UInt_t uid)
 Set the unique object id. More...
 
virtual void SysError (const char *method, const char *msgfmt,...) const
 Issue system error message. More...
 
R__ALWAYS_INLINE Bool_t TestBit (UInt_t f) const
 
Int_t TestBits (UInt_t f) const
 
virtual void UseCurrentStyle ()
 Set current style settings in this object This function is called when either TCanvas::UseCurrentStyle or TROOT::ForceStyle have been invoked. More...
 
virtual void Warning (const char *method, const char *msgfmt,...) const
 Issue warning message. More...
 
virtual Int_t Write (const char *name=0, Int_t option=0, Int_t bufsize=0)
 Write this object to the current directory. More...
 
virtual Int_t Write (const char *name=0, Int_t option=0, Int_t bufsize=0) const
 Write this object to the current directory. More...
 

Static Public Attributes

static constexpr const char *const fgEntryStatusText [kEntryBeyondEnd+1]
 

Protected Types

using NamedProxies_t = std::unordered_map< std::string, std::unique_ptr< ROOT::Internal::TNamedBranchProxy > >
 

Protected Member Functions

void AddProxy (ROOT::Internal::TNamedBranchProxy *p)
 
void DeregisterValueReader (ROOT::Internal::TTreeReaderValueBase *reader)
 Remove a value reader for this tree. More...
 
ROOT::Internal::TNamedBranchProxyFindProxy (const char *branchname) const
 
void Initialize ()
 Initialization of the director. More...
 
Bool_t RegisterValueReader (ROOT::Internal::TTreeReaderValueBase *reader)
 Add a value reader for this tree. More...
 
EEntryStatus SetEntryBase (Long64_t entry, Bool_t local)
 Load an entry into the tree, return the status of the read. More...
 
Bool_t SetProxies ()
 Tell readers we now have a tree. More...
 
- Protected Member Functions inherited from TObject
virtual void DoError (int level, const char *location, const char *fmt, va_list va) const
 Interface to ErrorHandler (protected). More...
 
void MakeZombie ()
 

Private Types

enum  EStatusBits { kBitIsChain = BIT(14), kBitHaveWarnedAboutEntryListAttachedToTTree = BIT(15), kBitSetEntryBaseCallingLoadTree = BIT(16) }
 

Private Member Functions

std::string GetProxyKey (const char *branchname)
 

Private Attributes

Long64_t fBeginEntry = 0LL
 This allows us to propagate the range to the TTreeCache. More...
 
ROOT::Internal::TBranchProxyDirectorfDirector = nullptr
 proxying director, owned More...
 
Long64_t fEndEntry = -1LL
 The end of the entry loop. More...
 
Long64_t fEntry = -1
 Current (non-local) entry of fTree or of fEntryList if set. More...
 
TEntryListfEntryList = nullptr
 entry list to be used More...
 
EEntryStatus fEntryStatus = kEntryNotLoaded
 status of most recent read request More...
 
std::deque< ROOT::Internal::TFriendProxy * > fFriendProxies
 proxying for friend TTrees, owned More...
 
ELoadTreeStatus fLoadTreeStatus = kNoTree
 Indicator on how LoadTree was called 'last' time. More...
 
TNotifyLink< TTreeReaderfNotify
 
NamedProxies_t fProxies
 attached ROOT::TNamedBranchProxies; owned More...
 
Bool_t fProxiesSet = kFALSE
 True if the proxies have been set, false otherwise. More...
 
Bool_t fSetEntryBaseCallingLoadTree = kFALSE
 True if during the LoadTree execution triggered by SetEntryBase. More...
 
TTreefTree = nullptr
 tree that's read More...
 
std::deque< ROOT::Internal::TTreeReaderValueBase * > fValues
 readers that use our director More...
 

Friends

class ROOT::Internal::TTreeReaderArrayBase
 
class ROOT::Internal::TTreeReaderValueBase
 

Additional Inherited Members

- Static Public Member Functions inherited from TObject
static Long_t GetDtorOnly ()
 Return destructor only flag. More...
 
static Bool_t GetObjectStat ()
 Get status of object stat flag. More...
 
static void SetDtorOnly (void *obj)
 Set destructor only flag. More...
 
static void SetObjectStat (Bool_t stat)
 Turn on/off tracking of objects in the TObjectTable. More...
 

#include <TTreeReader.h>

Inheritance diagram for TTreeReader:
[legend]

Member Typedef Documentation

◆ iterator

Definition at line 123 of file TTreeReader.h.

◆ NamedProxies_t

using TTreeReader::NamedProxies_t = std::unordered_map<std::string, std::unique_ptr<ROOT::Internal::TNamedBranchProxy> >
protected

Definition at line 245 of file TTreeReader.h.

Member Enumeration Documentation

◆ EEntryStatus

Enumerator
kEntryValid 

data read okay

kEntryNotLoaded 

no entry has been loaded yet

kEntryNoTree 

the tree does not exist

kEntryNotFound 

the tree entry number does not exist

kEntryChainSetupError 

problem in accessing a chain element, e.g. file without the tree

kEntryChainFileError 

problem in opening a chain's file

kEntryDictionaryError 

problem reading dictionary info from tree

kEntryBeyondEnd 

last entry loop has reached its end

kEntryBadReader 

One of the readers was not successfully initialized.

kEntryUnknownError 

LoadTree return less than -4, likely a 'newer' error code.

Definition at line 125 of file TTreeReader.h.

◆ ELoadTreeStatus

Enumerator
kNoTree 

default state, no TTree is connected (formerly 'Zombie' state)

kLoadTreeNone 

Notify has not been called yet.

kInternalLoadTree 

Notify/LoadTree was last called from SetEntryBase.

kExternalLoadTree 

User code called LoadTree directly.

Definition at line 138 of file TTreeReader.h.

◆ EStatusBits

Enumerator
kBitIsChain 

our tree is a chain

kBitHaveWarnedAboutEntryListAttachedToTTree 

the tree had a TEntryList and we have warned about that

kBitSetEntryBaseCallingLoadTree 

SetEntryBase is in the process of calling TChain/TTree::LoadTree.

Definition at line 282 of file TTreeReader.h.

Constructor & Destructor Documentation

◆ TTreeReader() [1/4]

TTreeReader::TTreeReader ( )

Default constructor. Call SetTree to connect to a TTree.

Definition at line 190 of file TTreeReader.cxx.

◆ TTreeReader() [2/4]

TTreeReader::TTreeReader ( TTree tree,
TEntryList entryList = nullptr 
)

Access data from tree.

Definition at line 195 of file TTreeReader.cxx.

◆ TTreeReader() [3/4]

TTreeReader::TTreeReader ( const char *  keyname,
TDirectory dir,
TEntryList entryList = nullptr 
)

Access data from the tree called keyname in the directory (e.g.

TFile) dir, or the current directory if dir is NULL. If keyname cannot be found, or if it is not a TTree, IsInvalid() will return true.

Definition at line 212 of file TTreeReader.cxx.

◆ TTreeReader() [4/4]

TTreeReader::TTreeReader ( const char *  keyname,
TEntryList entryList = nullptr 
)
inline

Definition at line 159 of file TTreeReader.h.

◆ ~TTreeReader()

TTreeReader::~TTreeReader ( )

Tell all value readers that the tree reader does not exist anymore.

Definition at line 230 of file TTreeReader.cxx.

Member Function Documentation

◆ AddProxy()

void TTreeReader::AddProxy ( ROOT::Internal::TNamedBranchProxy p)
inlineprotected

Definition at line 253 of file TTreeReader.h.

◆ begin()

Iterator_t TTreeReader::begin ( )
inline

Return an iterator to the 0th TTree entry.

Definition at line 238 of file TTreeReader.h.

◆ DeregisterValueReader()

void TTreeReader::DeregisterValueReader ( ROOT::Internal::TTreeReaderValueBase reader)
protected

Remove a value reader for this tree.

Definition at line 644 of file TTreeReader.cxx.

◆ end()

Iterator_t TTreeReader::end ( ) const
inline

Return an iterator beyond the last TTree entry.

Definition at line 242 of file TTreeReader.h.

◆ FindProxy()

ROOT::Internal::TNamedBranchProxy* TTreeReader::FindProxy ( const char *  branchname) const
inlineprotected

Definition at line 247 of file TTreeReader.h.

◆ GetCurrentEntry()

Long64_t TTreeReader::GetCurrentEntry ( ) const
inline

Returns the index of the current entry being read.

If IsChain(), the returned index corresponds to the global entry number (i.e. not the entry number local to the chain's current tree). If fEntryList, the returned index corresponds to an index in the TEntryList; to translate to the TChain's / TTree's entry number pass it through reader.GetEntryList()->GetEntry(reader.GetCurrentEntry()).

Definition at line 233 of file TTreeReader.h.

◆ GetEntries() [1/2]

Long64_t TTreeReader::GetEntries ( ) const

Returns the number of entries of the TEntryList if one is provided, else of the TTree / TChain, independent of a range set by SetEntriesRange() by calling TTree/TChain::GetEntriesFast.

Definition at line 434 of file TTreeReader.cxx.

◆ GetEntries() [2/2]

Long64_t TTreeReader::GetEntries ( Bool_t  force)

Returns the number of entries of the TEntryList if one is provided, else of the TTree / TChain, independent of a range set by SetEntriesRange().

Parameters
forceIf IsChain() and force, determines whether all TFiles of this TChain should be opened to determine the exact number of entries of the TChain. If !IsChain(), force is ignored.

Definition at line 451 of file TTreeReader.cxx.

◆ GetEntriesRange()

std::pair<Long64_t, Long64_t> TTreeReader::GetEntriesRange ( ) const
inline

Get the begin and end entry numbers.

Returns
a pair contained the begin and end entry numbers.

Definition at line 214 of file TTreeReader.h.

◆ GetEntryList()

TEntryList* TTreeReader::GetEntryList ( ) const
inline

Definition at line 175 of file TTreeReader.h.

◆ GetEntryStatus()

EEntryStatus TTreeReader::GetEntryStatus ( ) const
inline

Definition at line 221 of file TTreeReader.h.

◆ GetProxyKey()

std::string TTreeReader::GetProxyKey ( const char *  branchname)
inlineprivate

Definition at line 275 of file TTreeReader.h.

◆ GetTree()

TTree* TTreeReader::GetTree ( ) const
inline

Definition at line 174 of file TTreeReader.h.

◆ Initialize()

void TTreeReader::Initialize ( )
protected

Initialization of the director.

Definition at line 254 of file TTreeReader.cxx.

◆ IsChain()

Bool_t TTreeReader::IsChain ( ) const
inline

Definition at line 170 of file TTreeReader.h.

◆ IsInvalid()

Bool_t TTreeReader::IsInvalid ( ) const
inline

Definition at line 172 of file TTreeReader.h.

◆ Next()

Bool_t TTreeReader::Next ( )
inline

Move to the next entry (or index of the TEntryList if that is set).

Returns
false if the previous entry was already the last entry. This allows the function to be used in while (reader.Next()) { ... }

Definition at line 183 of file TTreeReader.h.

◆ Notify()

Bool_t TTreeReader::Notify ( )
virtual

Callback from TChain and TTree's LoadTree.

Reimplemented from TObject.

Definition at line 285 of file TTreeReader.cxx.

◆ RegisterValueReader()

Bool_t TTreeReader::RegisterValueReader ( ROOT::Internal::TTreeReaderValueBase reader)
protected

Add a value reader for this tree.

Definition at line 629 of file TTreeReader.cxx.

◆ Restart()

void TTreeReader::Restart ( )

Restart a Next() loop from entry 0 (of TEntryList index 0 of fEntryList is set).

Definition at line 416 of file TTreeReader.cxx.

◆ SetEntriesRange()

TTreeReader::EEntryStatus TTreeReader::SetEntriesRange ( Long64_t  beginEntry,
Long64_t  endEntry 
)

Set the begin and end entry numbers.

Set the range of entries to be loaded by Next(); end will not be loaded.

Parameters
beginEntryThe first entry that Next() will load.
endEntryThe entry that Next() will return kFALSE on (i.e. not load anymore).

If end <= begin, end is ignored (set to -1) and only begin is used. Example:

reader.SetEntriesRange(3, 5);
while (reader.Next()) {
// Will load entries 3 and 4.
}
Parameters
beginEntryThe first entry to be loaded by Next().
endEntryThe entry where Next() will return kFALSE, not loading it.

Definition at line 384 of file TTreeReader.cxx.

◆ SetEntry()

EEntryStatus TTreeReader::SetEntry ( Long64_t  entry)
inline

Set the next entry (or index of the TEntryList if that is set).

Parameters
entryIf not TEntryList is set, the entry is a global entry (i.e. not the entry number local to the chain's current tree).
Returns
the entry's read status, i.e. whether the entry is available.

Definition at line 192 of file TTreeReader.h.

◆ SetEntryBase()

TTreeReader::EEntryStatus TTreeReader::SetEntryBase ( Long64_t  entry,
Bool_t  local 
)
protected

Load an entry into the tree, return the status of the read.

For chains, entry is the global (i.e. not tree-local) entry number, unless local is true, in which case entry specifies the entry number within the current tree. This is needed for instance for TSelector::Process().

Definition at line 475 of file TTreeReader.cxx.

◆ SetLocalEntry()

EEntryStatus TTreeReader::SetLocalEntry ( Long64_t  entry)
inline

Set the next local tree entry.

If a TEntryList is set, this function is equivalent to SetEntry().

Parameters
entryEntry number of the TChain's current TTree. This is the entry number passed for instance by TSelector::Process(entry), i.e. within TSelector::Process() always use SetLocalEntry() and not SetEntry()!
Returns
the entry's read status, i.e. whether the entry is available.

Definition at line 202 of file TTreeReader.h.

◆ SetProxies()

Bool_t TTreeReader::SetProxies ( )
protected

Tell readers we now have a tree.

fValues gets insertions during this loop (when parameterized arrays are read), invalidating iterators. Use old-school counting instead.

Definition at line 331 of file TTreeReader.cxx.

◆ SetTree() [1/3]

void TTreeReader::SetTree ( TTree tree,
TEntryList entryList = nullptr 
)

Set (or update) the which tree to read from.

tree can be a TTree or a TChain.

Definition at line 587 of file TTreeReader.cxx.

◆ SetTree() [2/3]

void TTreeReader::SetTree ( const char *  keyname,
TEntryList entryList = nullptr 
)
inline

Definition at line 165 of file TTreeReader.h.

◆ SetTree() [3/3]

void TTreeReader::SetTree ( const char *  keyname,
TDirectory dir,
TEntryList entryList = nullptr 
)

Set (or update) the which tree to read from, passing the name of a tree in a directory.

Parameters
keyname- name of the tree in dir
dir- the TDirectory to load keyname from (or gDirectory if nullptr)
entryList- the TEntryList to attach to the TTreeReader.

Definition at line 617 of file TTreeReader.cxx.

Friends And Related Function Documentation

◆ ROOT::Internal::TTreeReaderArrayBase

Definition at line 309 of file TTreeReader.h.

◆ ROOT::Internal::TTreeReaderValueBase

Definition at line 308 of file TTreeReader.h.

Member Data Documentation

◆ fBeginEntry

Long64_t TTreeReader::fBeginEntry = 0LL
private

This allows us to propagate the range to the TTreeCache.

Definition at line 304 of file TTreeReader.h.

◆ fDirector

ROOT::Internal::TBranchProxyDirector* TTreeReader::fDirector = nullptr
private

proxying director, owned

Definition at line 293 of file TTreeReader.h.

◆ fEndEntry

Long64_t TTreeReader::fEndEntry = -1LL
private

The end of the entry loop.

When set (i.e. >= 0), it provides a way to stop looping over the TTree when we reach a certain entry: Next() returns kFALSE when GetCurrentEntry() reaches fEndEntry.

Definition at line 303 of file TTreeReader.h.

◆ fEntry

Long64_t TTreeReader::fEntry = -1
private

Current (non-local) entry of fTree or of fEntryList if set.

Definition at line 298 of file TTreeReader.h.

◆ fEntryList

TEntryList* TTreeReader::fEntryList = nullptr
private

entry list to be used

Definition at line 289 of file TTreeReader.h.

◆ fEntryStatus

EEntryStatus TTreeReader::fEntryStatus = kEntryNotLoaded
private

status of most recent read request

Definition at line 290 of file TTreeReader.h.

◆ fFriendProxies

std::deque<ROOT::Internal::TFriendProxy*> TTreeReader::fFriendProxies
private

proxying for friend TTrees, owned

Definition at line 294 of file TTreeReader.h.

◆ fgEntryStatusText

constexpr const char *const TTreeReader::fgEntryStatusText
static
Initial value:
= {
"valid entry",
"the tree does not exist",
"the tree entry number does not exist",
"cannot access chain element",
"problem in opening a chain's file",
"problem reading dictionary info from tree",
"last entry loop has reached its end"
}

Definition at line 145 of file TTreeReader.h.

◆ fLoadTreeStatus

ELoadTreeStatus TTreeReader::fLoadTreeStatus = kNoTree
private

Indicator on how LoadTree was called 'last' time.

Definition at line 291 of file TTreeReader.h.

◆ fNotify

TNotifyLink<TTreeReader> TTreeReader::fNotify
private

Definition at line 292 of file TTreeReader.h.

◆ fProxies

NamedProxies_t TTreeReader::fProxies
private

attached ROOT::TNamedBranchProxies; owned

Definition at line 296 of file TTreeReader.h.

◆ fProxiesSet

Bool_t TTreeReader::fProxiesSet = kFALSE
private

True if the proxies have been set, false otherwise.

Definition at line 305 of file TTreeReader.h.

◆ fSetEntryBaseCallingLoadTree

Bool_t TTreeReader::fSetEntryBaseCallingLoadTree = kFALSE
private

True if during the LoadTree execution triggered by SetEntryBase.

Definition at line 306 of file TTreeReader.h.

◆ fTree

TTree* TTreeReader::fTree = nullptr
private

tree that's read

Definition at line 288 of file TTreeReader.h.

◆ fValues

std::deque<ROOT::Internal::TTreeReaderValueBase*> TTreeReader::fValues
private

readers that use our director

Definition at line 295 of file TTreeReader.h.

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