#include <ROOTLegacyReader.h>

Public Member Functions
	ROOTLegacyReader ()=default

	~ROOTLegacyReader ()=default

	ROOTLegacyReader (const ROOTLegacyReader &)=delete

ROOTLegacyReader &	operator= (const ROOTLegacyReader &)=delete

void	openFile (const std::string &filename)

void	openFiles (const std::vector< std::string > &filenames)

std::unique_ptr< podio::ROOTFrameData >	readNextEntry (const std::string &)

std::unique_ptr< podio::ROOTFrameData >	readEntry (const std::string &, const unsigned entry)

unsigned	getEntries (const std::string &) const
	Returns number of entries for a given category.

podio::version::Version	currentFileVersion () const
	Get the build version of podio that has been used to write the current file.

std::vector< std::string_view >	getAvailableCategories () const
	Get the names of all the availalable Frame categories in the current file(s)

Detailed Description

A root reader for reading legacy podio root files that have been written using the legacy, non Frame based I/O model. This reader grants Frame based access to those files, by mimicking the Frame I/O functionality and the interfaces of those readers.

NOTE: Since there was only one category ("events") for those legacy podio files this reader will really only work if you try to read that category, and will simply return no data if you try to read anything else.

Definition at line 48 of file ROOTLegacyReader.h.

Constructor & Destructor Documentation

◆ ROOTLegacyReader() [1/2]

podio::ROOTLegacyReader::ROOTLegacyReader ( )

default

◆ ~ROOTLegacyReader()

podio::ROOTLegacyReader::~ROOTLegacyReader ( )

default

◆ ROOTLegacyReader() [2/2]

podio::ROOTLegacyReader::ROOTLegacyReader ( const ROOTLegacyReader & )

delete

Member Function Documentation

◆ currentFileVersion()

podio::version::Version podio::ROOTLegacyReader::currentFileVersion ( ) const

inline

Get the build version of podio that has been used to write the current file.

Definition at line 84 of file ROOTLegacyReader.h.

                                                 {
    return m_fileVersion;
  }

◆ getAvailableCategories()

std::vector< std::string_view > podio::ROOTLegacyReader::getAvailableCategories ( ) const

Get the names of all the availalable Frame categories in the current file(s)

Definition at line 233 of file ROOTLegacyReader.cc.

                                                                         {
  return {m_categoryName};
}

◆ getEntries()

unsigned podio::ROOTLegacyReader::getEntries ( const std::string & name ) const

Returns number of entries for a given category.

Definition at line 178 of file ROOTLegacyReader.cc.

                                                                 {
  if (name != m_categoryName) {
    return 0;
  }
  return m_chain->GetEntries();
}

◆ openFile()

void podio::ROOTLegacyReader::openFile ( const std::string & filename )

Definition at line 131 of file ROOTLegacyReader.cc.

                                                         {
  openFiles({filename});
}

◆ openFiles()

void podio::ROOTLegacyReader::openFiles ( const std::vector< std::string > & filenames )

Definition at line 135 of file ROOTLegacyReader.cc.

                                                                      {
  m_chain = std::make_unique<TChain>("events");
  for (const auto& filename : filenames) {
    //-1 forces the headers to be read so that
    // the validity of the files can be checked
    if (!m_chain->Add(filename.c_str(), -1)) {
      throw std::runtime_error("File " + filename + " couldn't be found");
    }
  }
 
  // read the meta data and build the collectionBranches cache
  // NOTE: This is a small pessimization, if we do not read all collections
  // afterwards, but it makes the handling much easier in general
  auto metadatatree = static_cast<TTree*>(m_chain->GetFile()->Get("metadata"));
  m_table = std::make_shared<CollectionIDTable>();
  auto* table = m_table.get();
  metadatatree->SetBranchAddress("CollectionIDs", &table);
 
  podio::version::Version* versionPtr{nullptr};
  if (auto* versionBranch = root_utils::getBranch(metadatatree, "PodioVersion")) {
    versionBranch->SetAddress(&versionPtr);
  }
 
  // Check if the CollectionTypeInfo branch is there and assume that the file
  // has been written with with podio pre #197 (<0.13.1) if that is not the case
  if (auto* collInfoBranch = root_utils::getBranch(metadatatree, "CollectionTypeInfo")) {
    auto collectionInfo = new std::vector<root_utils::CollectionInfoT>;
    collInfoBranch->SetAddress(&collectionInfo);
    metadatatree->GetEntry(0);
    createCollectionBranches(*collectionInfo);
    delete collectionInfo;
  } else {
    std::cout << "PODIO: Reconstructing CollectionTypeInfo branch from other sources in file: \'"
              << m_chain->GetFile()->GetName() << "\'" << std::endl;
    metadatatree->GetEntry(0);
    const auto collectionInfo = root_utils::reconstructCollectionInfo(m_chain.get(), *m_table);
    createCollectionBranches(collectionInfo);
  }
 
  m_fileVersion = versionPtr ? *versionPtr : podio::version::Version{0, 0, 0};
  delete versionPtr;
}

Referenced by openFile().

◆ operator=()

ROOTLegacyReader & podio::ROOTLegacyReader::operator= ( const ROOTLegacyReader & )

delete

◆ readEntry()

std::unique_ptr< podio::ROOTFrameData > podio::ROOTLegacyReader::readEntry	(	const std::string &	name,
		const unsigned	entry
	)

Read the specified data entry from which a Frame can be constructed In case the entry does not exist, this returns a nullptr.

NOTE: the category name has to be "events" in this case, as only that category is available for legacy files.

Definition at line 29 of file ROOTLegacyReader.cc.

                                                                                                   {
  if (name != m_categoryName) {
    return nullptr;
  }
  m_eventNumber = entry;
  return readEntry();
}

Referenced by operator=(), readEntry(), and readNextEntry().

◆ readNextEntry()

std::unique_ptr< ROOTFrameData > podio::ROOTLegacyReader::readNextEntry ( const std::string & name )

Read the next data entry from which a Frame can be constructed. In case there are no more entries left, this returns a nullptr.