File ROOTLegacyReader.h

namespace podio
class ROOTLegacyReader
#include <podio/ROOTLegacyReader.h>

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.

Public Functions

ROOTLegacyReader() = default

Create a SIOLegacyReader.

~ROOTLegacyReader() = default

Destructor.

ROOTLegacyReader(const ROOTLegacyReader&) = delete

The SIOLegacyReader is not copy-able.

ROOTLegacyReader &operator=(const ROOTLegacyReader&) = delete

The SIOLegacyReader is not copy-able.

void openFile(const std::string &filename)

Open a single file for reading.

Parameters:

filename – The name of the input file

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

Open multiple files for reading and then treat them as if they are one file.

This usually boils down to “the files have been written with the same

”settings”, e.g. they are outputs of a batched process.

Note

All of the files are assumed to have the same structure. Specifically this means:

  • The collections that are contained in the individual event are always the same

Parameters:

filenames – The filenames of all input files that should be read

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

Read the next data entry from which a Frame can be constructed.

Note

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

Returns:

FrameData from which a podio::Frame can be constructed if there are still entries left to read. Otherwise a nullptr

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

Read the desired data entry from which a Frame can be constructed.

Note

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

Returns:

FrameData from which a podio::Frame can be constructed if the desired entry exists. Otherwise a nullptr

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

Get the number of entries for the given name.

Parameters:

name – The name of the category

Returns:

The number of entries that are available for the category

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

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

Returns:

The podio build version

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

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

Returns:

The names of the available categories from the file

Private Functions

std::pair<TTree*, unsigned> getLocalTreeAndEntry(const std::string &treename)
void createCollectionBranches(const std::vector<root_utils::CollectionWriteInfoT> &collInfo)
podio::GenericParameters readEventMetaData()
podio::CollectionReadBuffers getCollectionBuffers(const std::pair<std::string, detail::CollectionInfo> &collInfo)
std::unique_ptr<podio::ROOTFrameData> readEntry()

Private Members

std::vector<std::pair<std::string, detail::CollectionInfo>> m_storedClasses = {}
std::shared_ptr<CollectionIDTable> m_table = {nullptr}
std::unique_ptr<TChain> m_chain = {nullptr}
unsigned m_eventNumber = {0}
std::vector<root_utils::CollectionBranches> m_collectionBranches = {}
podio::version::Version m_fileVersion = {0, 0, 0}

Private Static Attributes

static constexpr auto m_categoryName = "events"

The only category name that is available from legacy files.