File RNTupleReader.h

namespace podio

class RNTupleReader

#include <podio/RNTupleReader.h>

This class has the function to read available data from disk and to prepare collections and buffers.

The RNTupleReader can be used to read files that have been written with the RNTuple backend.

The RNTupleReader provides the data as ROOTFrameData from which a podio::Frame can be constructed. It can be used to read files written by the RNTupleWriter.

Public Functions

RNTupleReader() = default

Create a RNTupleReader.

~RNTupleReader() = default

Destructor.

RNTupleReader(const RNTupleReader&) = delete

The RNTupleReader is not copy-able.

RNTupleReader &operator=(const RNTupleReader&) = delete

The RNTupleReader 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.

Note

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

• The same categories are available from all files

• The collections that are contained in the individual categories are the same across all files

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

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

Parameters:

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

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

Read the next data entry for a given category.

Parameters:

name – The category name for which to read the next entry

Returns:

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

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

Read the desired data entry for a given category.

Parameters:

• name – The category name for which to read the next entry

• entry – The entry number to read

Returns:

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

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 categores from the file

unsigned getEntries(const std::string &name)

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

inline const std::string_view getDatamodelDefinition(const std::string &name) const

Get the datamodel definition for the given name.

Parameters:

name – The name of the datamodel

Returns:

The high level definition of the datamodel in JSON format

inline std::vector<std::string> getAvailableDatamodels() const

Get all names of the datamodels that are available from this reader.

Returns:

The names of the datamodels

Private Functions

bool initCategory(const std::string &category)

Initialize the given category by filling the maps with metadata information that will be used later.

GenericParameters readEventMetaData(const std::string &name, unsigned entNum)

Read and reconstruct the generic parameters of the Frame.

template<typename T>
void readParams(const std::string &name, unsigned entNum, GenericParameters &params)

Private Members

std::unique_ptr<ROOT::Experimental::RNTupleReader> m_metadata = {}

podio::version::Version m_fileVersion = {}

DatamodelDefinitionHolder m_datamodelHolder = {}

std::unordered_map<std::string, std::vector<std::unique_ptr<ROOT::Experimental::RNTupleReader>>> m_readers = {}

std::unordered_map<std::string, std::unique_ptr<ROOT::Experimental::RNTupleReader>> m_metadata_readers = {}

std::vector<std::string> m_filenames = {}

std::unordered_map<std::string, int> m_entries = {}

std::unordered_map<std::string, unsigned> m_totalEntries = {}

std::unordered_map<std::string, CollectionInfo> m_collectionInfo = {}

std::vector<std::string> m_availableCategories = {}

std::unordered_map<std::string, std::shared_ptr<podio::CollectionIDTable>> m_idTables = {}

struct CollectionInfo

Public Members

std::vector<unsigned int> id = {}

std::vector<std::string> name = {}

std::vector<std::string> type = {}

std::vector<short> isSubsetCollection = {}

std::vector<SchemaVersionT> schemaVersion = {}