Class podio::Writer

class Writer

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

Offers some more high level functionality compared to the lower level backend specific writers that this class wraps. In addition, it provides convenience methods to deal specifically with the “events” frame category.

Note

Since this simply wraps lower level writers, some of the limitations of the wrapped writers will still apply, e.g. if used for writing ROOT files frames of a given category will have to have the same contents.

Note

The recommended way to construct is to use the makeWriter() function since that handles the instantiation of the correct low level writers

Public Functions

template<typename T>
inline Writer(std::unique_ptr<T> writer)

Create a Writer from a lower level writer.

Template Parameters:

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

Parameters:

writer – A low level writer that does the actual work

Writer(const Writer&) = delete
Writer &operator=(const Writer&) = delete
Writer(Writer&&) = default
Writer &operator=(Writer&&) = default
~Writer() = default

Destructor.

This also takes care of writing all the necessary metadata to read files back again.

inline void writeFrame(const podio::Frame &frame, const std::string &category)

Store the given frame with the given category.

This stores all available categories from the passed frame

Parameters:

  • frame – The frame to write

  • category – The category name under which this frame should be stored

inline void writeFrame(const podio::Frame &frame, const std::string &category, const std::vector<std::string> &collections)

Store the given Frame with the given category.

This stores only the desired collections and not the complete frame.

Parameters:

  • frame – The Frame to store

  • category – The category name under which this Frame should be stored

  • collections – The collection names that should be written

inline void writeEvent(const podio::Frame &frame)

Store the given frame under the “events” category.

This stores all available categories from the passed frame

Parameters:

frame – The frame to write

inline void writeEvent(const podio::Frame &frame, const std::vector<std::string> &collections)

Store the given Frame under the “events” category.

This stores only the desired collections and not the complete frame.

Parameters:

  • frame – The Frame to store

  • collections – The collection names that should be written

inline void finish()

Write the current file, including all the necessary metadata to read it again.

Note

The destructor will also call this, so letting a Writer go out of scope is also a viable way to write a readable file