File Reader.h

namespace podio

Functions

Reader makeReader(const std::string &filename)

Create a Reader that is able to read the file or files matching a glob pattern.

This will inspect the filename as well as peek at the file contents to instantiate the correct low level reader to open and read the file

Parameters:: filename – The (path to the) file to read from. The file path can include glob patterns to match multiple files.
Returns:: A Reader that has been initialized and that can be used for reading data from the passed file

Reader makeReader(const std::vector<std::string> &filenames)

Create a Reader that is able to read the files.

This will inspect the filenames as well as peek into the first file only to decide based on the contents which low level reader to instantiate for reading. All files are assumed to be of the same I/O format, no switching between formats is possible.

Note

For SIO files this will only work with exactly one file!

Parameters:: filenames – The (paths to the) files to read from
Throws:: std::runtime_error – in case the file extensions differ or in case support for the necessary I/O backend has not been built or in case multiple files for the SIO backend are passed
Returns:: A Reader that has been initialized and that can be used for reading data from the passed files

class Reader

#include <podio/Reader.h>

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

Private Members

std::unique_ptr<ReaderConcept> m_self = {nullptr}

struct ReaderConcept

Public Functions

virtual ~ReaderConcept() = default

virtual podio::Frame readNextFrame(const std::string &name, const std::vector<std::string>&) = 0

virtual podio::Frame readFrame(const std::string &name, size_t index, const std::vector<std::string>&) = 0

virtual size_t getEntries(const std::string &name) const = 0

virtual podio::version::Version currentFileVersion() const = 0

virtual std::optional<podio::version::Version> currentFileVersion(const std::string &name) const = 0

virtual std::vector<std::string_view> getAvailableCategories() const = 0

virtual const std::string_view getDatamodelDefinition(const std::string &name) const = 0

virtual std::vector<std::string> getAvailableDatamodels() const = 0

template<typename T> struct ReaderModel : public podio::Reader::ReaderConcept 

Public Functions

inline ReaderModel(std::unique_ptr<T> reader)

ReaderModel(const ReaderModel&) = delete

ReaderModel &operator=(const ReaderModel&) = delete

ReaderModel(ReaderModel&&) = default

ReaderModel &operator=(ReaderModel&&) = default

~ReaderModel() override = default

inline podio::Frame readNextFrame(const std::string &name, const std::vector<std::string> &collsToRead) override

inline podio::Frame readFrame(const std::string &name, size_t index, const std::vector<std::string> &collsToRead) override

inline size_t getEntries(const std::string &name) const override

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

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

inline std::vector<std::string_view> getAvailableCategories() const override

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

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

Public Members

std::unique_ptr<T> m_reader