RootFileInfo Class Reference

Helper class to factorize some necessary tasks when working with Belle2 output files. More...

#include <RootFileInfo.h>

Collaboration diagram for RootFileInfo:

Public Member Functions
	RootFileInfo (const std::string &filename)
	Create an object from a given filename or url. More...
	~RootFileInfo ()
	Close the file and delete all structures associated with it.
TTree &	getPersistentTree ()
	Return a reference to the persistent tree.
TTree &	getEventTree ()
	Return a reference to the event tree.
const FileMetaData &	getFileMetaData ()
	Return the event metadata from the file. More...
const std::set< std::string > &	getBranchNames (bool persistent=false)
	Return a set of branch names for either the event or the persistent tree.
void	checkMissingBranches (const std::set< std::string > &required, bool persistent=false)
	Check if the event or persistent tree contain at least all the branches in the set of required branches. More...

Private Attributes
std::unique_ptr< TFile >	m_file
	Pointer to the file object.
std::unique_ptr< TTree >	m_persistent
	Pointer to the persistent tree.
std::unique_ptr< TTree >	m_events
	Pointer to the event tree.
std::unique_ptr< FileMetaData >	m_metadata
	Pointer to the file metadata once it has been read.
std::optional< std::set< std::string > >	m_persistentBranches
	Cached set of persistent branch names.
std::optional< std::set< std::string > >	m_eventBranches
	Cached set of event branch names.

Detailed Description

Helper class to factorize some necessary tasks when working with Belle2 output files.

Like the correct way to obtain the FileMetaData from a file or to check the list of existing branches

Definition at line 27 of file RootFileInfo.h.

Constructor & Destructor Documentation

RootFileInfo()

RootFileInfo ( const std::string &  filename )

explicit

Create an object from a given filename or url.

This will open the file and read the tree headers. It will throw exceptions if it encounters any problems:

• std::invalid_argument if the file cannot be opened at all
• std::runtime_error if any of the trees is missing or the number of entries in the persistent tree is !=1

Definition at line 18 of file RootFileInfo.cc.

  {
    // make sure TDirectory is reset after this function
    TDirectory::TContext directoryGuard;
    // Open the file
    m_file.reset(TFile::Open(filename.c_str(), "READ"));
    if (!m_file || !m_file->IsOpen()) throw std::invalid_argument("Could not open file");
    // We want to get two trees the same way but only need that here ... lambda it is
    auto getTree = [&file = this->m_file](const std::string & label, const std::string & name, std::unique_ptr<TTree>& destination) {
      TTree* tmp{nullptr};
      file->GetObject(name.c_str(), tmp);
      if (!tmp) throw std::runtime_error("No " + label + " tree found");
      destination.reset(tmp);
    };
    // So get the trees from the file and store them in the members
    getTree("persistent", c_treeNames[DataStore::c_Persistent], m_persistent);
    getTree("event", c_treeNames[DataStore::c_Event], m_events);
    // And finally check the number of entries in the persistent tree
    if (auto npersistent = m_persistent->GetEntries(); npersistent != 1) {
      throw std::runtime_error("Expected exactly one entry in persistent tree, found " + std::to_string(npersistent));
    }
  }

Member Function Documentation

checkMissingBranches()

void checkMissingBranches	(	const std::set< std::string > &	required,
		bool	persistent = false
	)

Check if the event or persistent tree contain at least all the branches in the set of required branches.

Throw a std::runtime_error if not

Definition at line 75 of file RootFileInfo.cc.

getFileMetaData()

const FileMetaData & getFileMetaData

(

)

Return the event metadata from the file.

On the first call it will be read from the persistent tree. If this fails a std::runtime_error is thrown.

Definition at line 41 of file RootFileInfo.cc.

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

• framework/io/include/RootFileInfo.h
• framework/io/src/RootFileInfo.cc