xAODTEventBranch Class Reference

Specialised class for browsing xAOD event interface objects in ROOT. More...

#include <xAODTEventBranch.h>

Inheritance diagram for xAODTEventBranch:

Collaboration diagram for xAODTEventBranch:

Public Member Functions
	xAODTEventBranch (::TTree &parent, xAOD::TEvent &event, const std::type_info &ti, const char *brName, const char *brType)
	Constructor with all the needed parameters. More...
virtual ::Int_t	GetEntry (::Long64_t entry, ::Int_t getall)
	Function getting the current entry for this branch. More...
virtual ::TClass *	IsA () const
	Function returning the type of ::TBranchObject. More...

Private Attributes
xAOD::TEvent *	m_event
	Pointer to the TEvent object reading the persistent tree. More...
const std::type_info *	m_ti
	The type of the object that needs to be read. More...
const void *	m_object
	Pointer to the object read in using TEvent. More...

Detailed Description

Specialised class for browsing xAOD event interface objects in ROOT.

In order to read xAOD interface objects/containers correctly, one needs to use the xAOD::TEvent class. Since the regular ROOT classes can't be taught how to use an external object for reading information, we need to do it using inheritance.

The design was pretty much stolen from the AthenaROOTAccess code. Luckily in this case the code can be a lot easier. Here we just need to ask the TEvent object for the correct pointer, and we're done.

Author

Attila Krasznahorkay Attil.nosp@m.a.Kr.nosp@m.aszna.nosp@m.hork.nosp@m.ay@ce.nosp@m.rn.c.nosp@m.h

Definition at line 32 of file xAODTEventBranch.h.

Constructor & Destructor Documentation

xAODTEventBranch()

xAODTEventBranch::xAODTEventBranch	(	::TTree &	parent,
		xAOD::TEvent &	event,
		const std::type_info &	ti,
		const char *	brName,
		const char *	brType
	)

Constructor with all the needed parameters.

Member Function Documentation

GetEntry()

Int_t xAODTEventBranch::GetEntry	(	::Long64_t	entry,
		::Int_t	getall
	)

Function getting the current entry for this branch.

This is the function doing the heavy lifting.

It loads the interface object for the current entry requested. Only doing some minimal overhead in the meanwhile.

Parameters

entry	The entry to be read for this object
getall	When set to 1, read all information about the branch (Not used.)

Returns

The number of bytes read, or a negative number if not successful

Definition at line 32 of file xAODTEventBranch.cxx.

                                                          {
 
   // Check if the branch is active:
   if( TestBit( kDoNotProcess ) ) {
      return 0;
   }
 
   // Check whether we already have the requested entry:
   if( fReadEntry == entry ) {
      return 1;
   }
 
   // Load the requested entry:
   if( m_event->getEntry( entry ) < 0 ) {
      Error( "GetEntry",
             XAOD_MESSAGE( "Problems with loading entry %lld" ), entry );
      return -1;
   }
 
   // Update the internal pointer:
   m_object = m_event->getInputObject( GetName(), *m_ti );
   if( ! m_object ) {
      Error( "GetEntry",
             XAOD_MESSAGE( "Failed to read variable of type \"%s\" with "
                           "key \"%s\"" ),
             GetClassName(), GetName() );
      return -1;
   }
 
   // We were successful:
   fReadEntry = entry;
   return 1;
}

IsA()

TClass * xAODTEventBranch::IsA

(

)

const

Function returning the type of ::TBranchObject.

I took this from the ARA code directly.

Apparenly TTree would not know how to handle this object if it reported its actual type. So we pretend that this is a TBranchObject object. That way TBrowser shows its contents nicely.

Returns

The class for TBranchObject

Definition at line 73 of file xAODTEventBranch.cxx.

                                    {
 
   return ::TBranchObject::IsA();
}

Member Data Documentation

m_event

xAOD::TEvent* xAODTEventBranch::m_event

private

Pointer to the TEvent object reading the persistent tree.

Definition at line 52 of file xAODTEventBranch.h.

m_object

const void* xAODTEventBranch::m_object

private

Pointer to the object read in using TEvent.

Definition at line 56 of file xAODTEventBranch.h.

m_ti

const std::type_info* xAODTEventBranch::m_ti

private

The type of the object that needs to be read.

Definition at line 54 of file xAODTEventBranch.h.

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

• xAODTEventBranch.h
• xAODTEventBranch.cxx