Class podio::SIOReader

class SIOReader

The SIOReader can be used to read files that have been written with the SIO backend.

The SIOReader provides the data as SIOFrameData from which a podio::Frame can be constructed. It can be used to read files written by the SIOWriter.

Public Functions

SIOReader()

Create an SIOReader.

~SIOReader() = default

SIOReader destructor.

SIOReader(const SIOReader&) = delete

The SIOReader is not copy-able.

SIOReader &operator=(const SIOReader&) = delete

The SIOReader is not copy-able.

std::unique_ptr<podio::SIOFrameData> readNextEntry(const std::string &name, const std::vector<std::string> &collsToRead = {})

Read the next data entry for a given category.

Note

Given how the SIO files are currently laid out it is in fact not possible to only read a subset of a Frame. Rather the subset of collections to read will be an artificial limit on the returned SIOFrameData. Limiting the collections to read will not improve I/O performance.

Parameters:

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

  • collsToRead – (optional) the collection names that should be read. If not provided (or empty) all collections will be read

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::SIOFrameData> readEntry(const std::string &name, const unsigned entry, const std::vector<std::string> &collsToRead = {})

Read the desired data entry for a given category.

Note

Given how the SIO files are currently laid out it is in fact not possible to only read a subset of a Frame. Rather the subset of collections to read will be an artificial limit on the returned SIOFrameData. Limiting the collections to read will not improve I/O performance.

Parameters:

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

  • entry – The entry number to read

  • collsToRead – (optional) the collection names that should be read. If not provided (or empty) all collections will be read

Returns:

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

void openFile(const std::string &filename)

Open the passed file for reading.

Parameters:

filename – The path to the file to read from

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 std::optional<podio::version::Version> currentFileVersion(const std::string &name) const

Get the (build) version of a datamodel that has been used to write the current file.

Parameters:

name – The name of the datamodel

Returns:

The (build) version of the datamodel if available or an empty optional

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

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

Returns:

The names of the available categores from the file

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