DADAFileReader

class baseband.dada.base.DADAFileReader(fh_raw)

Bases: baseband.vlbi_base.base.VLBIFileReaderBase

Simple reader for DADA files.

Wraps a binary filehandle, providing methods to help interpret the data, such as read_frame and get_frame_rate. By default, frame payloads are mapped rather than fully read into physical memory.

Parameters:

fh_raw : filehandle

Filehandle of the raw binary data file.

Attributes Summary

info	Standardized information on file readers.

Methods Summary

close()
get_frame_rate()	Determine the number of frames per second.
read_frame([memmap, verify])	Read the frame header and read or map the corresponding payload.
read_header()	Read a single header from the file.

Attributes Documentation

info

Standardized information on file readers.

The info descriptor has a number of standard attributes, which are determined from arguments passed in opening the file, from the first header (info.header0) and from possibly scanning the file to determine the duration of frames.

Examples

The most common use is simply to print information:

>>> from baseband.data import SAMPLE_MARK5B
>>> from baseband import mark5b
>>> fh = mark5b.open(SAMPLE_MARK5B, 'rb')
>>> fh.info
File information:
format = mark5b
frame_rate = 6400.0 Hz
bps = 2
complex_data = False

missing:  nchan: needed to determine sample shape and rate.
          kday, ref_time: needed to infer full times.

>>> fh.close()

>>> fh = mark5b.open(SAMPLE_MARK5B, 'rb', kday=56000, nchan=8)
>>> fh.info
File information:
format = mark5b
frame_rate = 6400.0 Hz
sample_rate = 32.0 MHz
samples_per_frame = 5000
sample_shape = (8,)
bps = 2
complex_data = False
start_time = 2014-06-13T05:30:01.000000000
>>> fh.close()

Attributes

format	(str or None) File format, or None if the underlying file cannot be parsed.
frame_rate	(Quantity) Number of data frames per unit of time.
sample_rate	(Quantity) Complete samples per unit of time.
samples_per_frame	(int) Number of complete samples in each frame.
sample_shape	(tuple) Dimensions of each complete sample (e.g., (nchan,)).
bps	(int) Number of bits used to encode each elementary sample.
complex_data	(bool) Whether the data are complex.
start_time	(Time) Time of the first complete sample.
missing	(dict) Entries are keyed by names of arguments that should be passed to the file reader to obtain full information. The associated entries explain why these arguments are needed.

Methods Documentation

close()

get_frame_rate()

Determine the number of frames per second.

The routine uses the sample rate and number of samples per frame from the first header in the file.

Returns:

frame_rate : Quantity

Frames per second.

read_frame(memmap=True, verify=True)

Read the frame header and read or map the corresponding payload.

Parameters:

memmap : bool, optional

If True (default), map the payload using memmap, so that parts are only loaded into memory as needed to access data.

verify : bool, optional

Whether to do basic checks of frame integrity. Default: True.

Returns:

frame : DADAFrame

With .header and .payload properties. The .data property returns all data encoded in the frame. Since this may be too large to fit in memory, it may be better to access the parts of interest by slicing the frame.

read_header()

Read a single header from the file.

Returns:header : DADAHeader