fire::UserReader Class Reference

class for easier reading of files written by fire More...

#include <UserReader.h>

Collaboration diagram for fire::UserReader:

Public Member Functions
	UserReader (bool wrap_around=false)
	Configure the reading mode. More...
	UserReader (const std::string &fn, unsigned long int n=0, bool wrap_around=false)
	Configure the reading mode and open a file. More...
void	open (const std::string &fn, unsigned long int n=0)
	Open the provided file, skipping an initial number of entries. More...
bool	next ()
	go to the next event entry in the file More...
unsigned long int	entries () const
	number of events in this file More...
bool	is_open () const
	check if reader is open or not More...
template<typename T >
const T &	get (const std::string &name, const std::string &pass="") const
	get the object for the current entry under the passed name More...

Private Attributes
Event	event_
	event bus for this reader
std::unique_ptr< io::Reader >	reader_
	handle of underlying reader
unsigned long int	i_entry_ {0}
	index of entry within file that is open
bool	wrap_around_ {false}
	do we wrap from end to beginning or throw exception?
bool	in_file_ {false}
	have we started yet?

Detailed Description

class for easier reading of files written by fire

The UserReader uses a specially-configured Event instance to interface with the file it is reading. This allows for it to read everything in the same manner that a processor would see while giving a user control over when to go to the next event in the file.

Note

opening the Event bus with a NULL writer is dangerous. Any development of this class needs to be done extremely carefully and tested thoroughly.

Basic Usage

fire::UserReader r("filename.h5");
while (r.next()) {
  const auto& obj = r.get<T>(name,pass);
}

Wrap Around Usage

If the reader is configured to wrap around from the end of the file to the beginning, then the reader cannot be in control of the event loop (since it would be an infinite loop). The dummy example below shows how a user can go through a file of arbitrary number of non-zero events repeating if necessary.

fire::UserReader r("filename.h5", n_events_to_skip, true);
for (std::size_t i{0}; i < n_events_wanted; ++i) {
  r.next();
  const auto& obj = r.get<T>(name, pass);
}

Constructor & Destructor Documentation

UserReader() [1/2]

fire::UserReader::UserReader

(

bool

wrap_around = false

)

Configure the reading mode.

Parameters

[in]

wrap_around

(optional) will we loop from end of file to beginning?

UserReader() [2/2]

fire::UserReader::UserReader	(	const std::string &	fn,
		unsigned long int	n = 0,
		bool	wrap_around = false
	)

Configure the reading mode and open a file.

See also

open for details on opening the file

Parameters

[in]	fn	file path to be opened
[in]	n	(optional) number of entries at beginning of file to skip
[in]	wrap_around	(optional) will we loop from end of file to beginning?

Member Function Documentation

entries()

unsigned long int fire::UserReader::entries

(

)

const

number of events in this file

Returns

number of event entries

get()

template<typename T >

const T & fire::UserReader::get ( const std::string &  name, const std::string &  pass = ""  ) const

inline

get the object for the current entry under the passed name

This is a direct call to Event::get so look there for more detailed documentation.

Template Parameters

T	type of data

Parameters

[in]	name	name of event object
[in]	pass	(optional) name of pass that produced the event object

is_open()

bool fire::UserReader::is_open

(

)

const

check if reader is open or not

Returns

true if reader is open and false otherwise

next()

bool fire::UserReader::next

(

)

go to the next event entry in the file

Exceptions

Exception

if a file hasn't been opened yet

We simply mimic the interaction between Process and Event such that Event::next is called "after" the last event and Event::load is called in preparation for the next event. If we have been configured to wrap around, then we simply re-call open and next instead of returning false at the end of the file.

Returns

true if another entry has been loaded

open()

void fire::UserReader::open	(	const std::string &	fn,
		unsigned long int	n = 0
	)

Open the provided file, skipping an initial number of entries.

See also

io::open for how we open ROOT and/or H5 files

io::root::Reader for reading of ROOT files

io::h5::Reader for reading of H5 files

Event::setInputFile for connecting the file reader and event bus

Skipping the initial number of entries is done by just calling next the requested number of times. Without any objects loaded onto the event bus, this is simply moving the entry index within Event.

Parameters

[in]	fn	file path to be opened
[in]	n	(optional) number of entries at beginning of file to skip

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The documentation for this class was generated from the following files:

• include/fire/UserReader.h
• src/fire/UserReader.cxx