RootFileInfo Class Reference

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

#include <RootFileInfo.h>

Public Member Functions
	RootFileInfo (const std::string &filename)
	Create an object from a given filename or url.
	~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.
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.

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.

  {
    // So let's get the list of existing branches
    const auto& existing = getBranchNames(persistent);
    // and fill a list of branches which are in required but not existing
    std::vector<std::string> missing;
    std::set_difference(required.begin(), required.end(), existing.begin(), existing.end(),
                        std::inserter(missing, missing.begin()));
    // and if that is not empty we complain
    if (!missing.empty()) {
      std::stringstream message;
      message << "Branches missing from event tree: ";
      for (const auto& name : missing) {
        message << name << ", ";
      }
      throw std::runtime_error(message.str());
    }
  }

getBranchNames()

const std::set< std::string > & getBranchNames

(

bool

persistent = false

)

Return a set of branch names for either the event or the persistent tree.

Definition at line 55 of file RootFileInfo.cc.

  {
    // which set of branches are we looking at?
    std::optional<std::set<std::string>>& cache{persistent ? m_persistentBranches : m_eventBranches};
    // if we didn't create the list already do it now
    if (!cache) {
      TTree& tree{persistent ? *m_persistent :* m_events};
      std::set<std::string> result;
      for (const TObject* obj : * (tree.GetListOfBranches())) {
        const auto* branch = dynamic_cast<const TBranch*>(obj);
        if (!branch) throw std::runtime_error("Entry in list of branches is no branch");
        result.emplace(branch->GetName());
      }
      // and remember
      cache.emplace(std::move(result));
    }
    // and just return the content
    return *cache;
  }

getEventTree()

TTree & getEventTree ( )

inline

Return a reference to the event tree.

Definition at line 42 of file RootFileInfo.h.

{ return *m_events; }

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.

  {
    if (!m_metadata) {
      // object not set yet, get it from file
      FileMetaData* metadata{nullptr};
      auto branchStatus = m_persistent->SetBranchAddress("FileMetaData", &metadata);
      if (branchStatus < 0) throw std::runtime_error("Error retrieving FileMetaData branch: " + std::to_string(branchStatus));
      if (m_persistent->GetEntry(0) <= 0 || !metadata) throw std::runtime_error("Cannot read FileMetaData");
      // and remembber
      m_metadata.reset(metadata);
    }
    return *m_metadata;
  }

getPersistentTree()

TTree & getPersistentTree ( )

inline

Return a reference to the persistent tree.

Definition at line 40 of file RootFileInfo.h.

{ return *m_persistent; }

Member Data Documentation

m_eventBranches

std::optional<std::set<std::string> > m_eventBranches

private

Cached set of event branch names.

Definition at line 65 of file RootFileInfo.h.

m_events

std::unique_ptr<TTree> m_events

private

Pointer to the event tree.

Definition at line 59 of file RootFileInfo.h.

m_file

std::unique_ptr<TFile> m_file

private

Pointer to the file object.

Definition at line 55 of file RootFileInfo.h.

m_metadata

std::unique_ptr<FileMetaData> m_metadata

private

Pointer to the file metadata once it has been read.

Definition at line 61 of file RootFileInfo.h.

m_persistent

std::unique_ptr<TTree> m_persistent

private

Pointer to the persistent tree.

Definition at line 57 of file RootFileInfo.h.

m_persistentBranches

std::optional<std::set<std::string> > m_persistentBranches

private

Cached set of persistent branch names.

Definition at line 63 of file RootFileInfo.h.

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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