Class podio::Reader

class Reader

Generic (type erased) reader class that can handle different I/O backends transparently.

Offers some more high level functionality compared to the lower level backend specific readers that this class wraps. In contrast to the lower level readers that usually return arbitrary FrameData, this interface class will return fully constructed Frames. In addition, it provides convenience methods to deal specifically with the “events” frame category.

Note

The recommended way to construct is to use the makeReader() functions since they handle the instantiation of the correct low level readers

Public Functions

template<typename T>
Reader(std::unique_ptr<T> actualReader)

Create a reader from a low level reader.

Template Parameters:

T – The type of the low level reader (will be deduced)

Parameters:

actualReader – a low level reader that provides access to FrameDataT

Reader(const Reader&) = delete

Reader &operator=(const Reader&) = delete

Reader(Reader&&) = default

Reader &operator=(Reader&&) = default

~Reader() = default

inline podio::Frame readNextFrame(const std::string &name, const std::vector<std::string> &collsToRead = {})

Read the next frame of a given category.

Parameters:

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

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

Throws:

std::invalid_argument – in case the category is not available or in case no more entries are available

Returns:

A fully constructed Frame with the contents read from file

inline podio::Frame readNextEvent(const std::vector<std::string> &collsToRead = {})

Read the next frame of the “events” category.

Parameters:

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

Throws:

std::invalid_argument – in case no (more) events are available

Returns:

A fully constructed Frame with the contents read from file

inline podio::Frame readFrame(const std::string &name, size_t index, const std::vector<std::string> &collsToRead = {})

Read a specific frame for a given category.

Parameters:

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

• index – The entry number to read

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

Throws:

std::invalid_argument – in case the category is not available or in case the specified entry is not available

Returns:

A fully constructed Frame with the contents read from file

inline podio::Frame readEvent(size_t index, const std::vector<std::string> &collsToRead = {})

Read a specific frame of the “events” category.

Parameters:

• index – The event number to read

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

Throws:

std::invalid_argument – in case the desired event is not available

Returns:

A fully constructed Frame with the contents read from file

inline size_t 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 size_t getEvents() const

Get the number of events.

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 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

inline 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

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