VLBIHeaderBase

class baseband.base.header.VLBIHeaderBase(words, verify=True)

Bases: ParsedHeaderBase

Base class for all VLBI headers.

Defines a number of common routines.

Generally, the actual class should define:

_struct : Struct instance that can pack/unpack header words.

_header_parser : HeaderParser instance corresponding to this class.

_properties : tuple of properties accessible/usable in initialisation

_invariants : set of keys of invariant header parts for a given type.

_stream_invarants : set of keys of invariant header parts for a stream.

It also should define properties that tell the size (getters and setters, or use a baseband.base.utils.fixedvalue if the value is the same for all instances):

payload_nbytes : number of bytes used by payload

frame_nbytes : total number of bytes for header + payload

get_time, set_time, and a corresponding time property :

time at start of payload

Parameters:

wordstuple or list of int, or None

header words (generally, 32 bit unsigned int). If given as a tuple, the header is immutable. If None, set to a list of zeros for later initialisation (and skip any verification).

verifybool, optional

Whether to do basic verification of integrity. For the base class, checks that the number of words is consistent with the struct size.

Attributes Summary

mutable	Whether the header can be modified.
nbytes	Size of the header in bytes.

Methods Summary

copy(**kwargs)	Create a mutable and independent copy of the header.
fromfile(fh, *args, **kwargs)	Read VLBI Header from file.
fromkeys(*args, **kwargs)	Initialise a header from parsed values.
fromvalues(*args, **kwargs)	Initialise a header from parsed values.
invariant_pattern([invariants])	Pattern and mask shared between headers of a type or stream.
invariants()	Set of keys of invariant header parts.
keys()	All keys defined for this header.
tofile(fh)	Write VLBI frame header to filehandle.
update(*[, verify])	Update the header by setting keywords or properties.
verify()	Verify that the length of the words is consistent.

Attributes Documentation

mutable

Whether the header can be modified.

nbytes

Size of the header in bytes.

Methods Documentation

copy(**kwargs)

Create a mutable and independent copy of the header.

Keyword arguments can be passed on as needed by possible subclasses.

classmethod fromfile(fh, *args, **kwargs)

Read VLBI Header from file.

Arguments are the same as for class initialisation. The header constructed will be immutable.

classmethod fromkeys(*args, **kwargs)

Initialise a header from parsed values.

Like fromvalues, but without any interpretation of keywords.

Raises:

KeyErrorif not all keys required are present in kwargs

classmethod fromvalues(*args, **kwargs)

Initialise a header from parsed values.

Here, the parsed values must be given as keyword arguments, i.e., for any header = cls(<words>), cls.fromvalues(**header) == header.

However, unlike for the fromkeys class method, data can also be set using arguments named after header methods, such as time.

Parameters:

*args

Possible arguments required to initialize an empty header.

**kwargs

Values used to initialize header keys or methods.

classmethod invariant_pattern(invariants=None, **kwargs)

Pattern and mask shared between headers of a type or stream.

This is mostly for use inside locate_frames().

Parameters:

invariantsset of str, optional

Set of keys to header parts that are shared between all headers of a given type or within a given stream/file. Default: from invariants().

**kwargs

Keyword arguments needed to instantiate an empty header. (Mostly for Mark 4).

Returns:

patternlist of int

The pattern that is shared between headers. If called on an instance, just the header words; if called on a class, words with defaults for the relevant parts set.

masklist of int

For each entry in pattern a bit mask with bits set for the parts that are invariant.

classmethod invariants()

Set of keys of invariant header parts.

On the class, this returns keys of parts that are shared by all headers for the type, on an instance, those that are shared with other headers in the same file.

If neither are defined, returns ‘sync_pattern’ if the header containts that key.

keys()

All keys defined for this header.

tofile(fh)

Write VLBI frame header to filehandle.

update(*, verify=True, **kwargs)

Update the header by setting keywords or properties.

Here, any keywords matching header keys are applied first, and any remaining ones are used to set header properties, in the order set by the class (in _properties).

Parameters:

verifybool, optional

If True (default), verify integrity after updating.

**kwargs

Arguments used to set keywords and properties.

verify()

Verify that the length of the words is consistent.

Subclasses should override this to do more thorough checks.