space_packet_parser.encodings

DataEncoding definitions

Attributes

logger

Classes

DataEncoding	Abstract base class for XTCE data encodings
StringDataEncoding	<xtce:StringDataEncoding>
NumericDataEncoding	Abstract class that is inherited by IntegerDataEncoding and FloatDataEncoding
IntegerDataEncoding	<xtce:IntegerDataEncoding>
FloatDataEncoding	<xtce:FloatDataEncoding>
BinaryDataEncoding	<xtce:BinaryDataEncoding>

Module Contents

space_packet_parser.encodings.logger

class space_packet_parser.encodings.DataEncoding

Bases: space_packet_parser.comparisons.AttrComparable

Abstract base class for XTCE data encodings

classmethod from_data_encoding_xml_element(element: lxml.etree.Element, ns: dict) → DataEncoding

Abstractmethod:

Abstract classmethod to create a data encoding object from an XML element.

Parameters:

• element (ElementTree.Element) – XML element

• ns (dict) – XML namespace dict

Return type:

DataEncoding

static get_default_calibrator(data_encoding_element: lxml.etree.Element, ns: dict) → space_packet_parser.calibrators.Calibrator | None

Gets the default_calibrator for the data encoding element

Parameters:

• data_encoding_element (ElementTree.Element) – The data encoding element which should contain the default_calibrator

• ns (dict) – XML namespace dict

Return type:

Union[Calibrator, None]

static get_context_calibrators(data_encoding_element: lxml.etree.Element, ns: dict) → List[space_packet_parser.calibrators.ContextCalibrator] | None

Get the context default_calibrator(s) for the data encoding element

Parameters:

• data_encoding_element (ElementTree.Element) – XML element

• ns (dict) – XML namespace dict

Returns:

List of ContextCalibrator objects or None if there are no context calibrators

Return type:

Union[List[ContextCalibrator], None]

static _get_linear_adjuster(parent_element: lxml.etree.Element, ns: dict) → callable | None

Examine a parent (e.g. a <xtce:DynamicValue>) element and find a LinearAdjustment if present, creating and returning a function that evaluates the adjustment.

Parameters:

• parent_element (ElementTree.Element) – Parent element which may contain a LinearAdjustment

• ns (dict) – XML namespace dict

Returns:

adjuster – Function object that adjusts a SizeInBits value by a linear function or None if no adjuster present

Return type:

Union[callable, None]

abstract _calculate_size(packet: space_packet_parser.packets.CCSDSPacket) → int

Calculate the size of the data item in bits.

Parameters:

packet (CCSDSPacket) – Binary representation of the packet used to get the coming bits and any previously parsed data items to infer field lengths.

Returns:

Size of the data item in bits.

Return type:

int

abstract parse_value(packet: space_packet_parser.packets.CCSDSPacket, **kwargs) → space_packet_parser.packets.ParameterDataTypes

Parse a value from packet data, possibly using previously parsed data items to inform parsing.

Parameters:

packet (CCSDSPacket) – Binary representation of the packet used to get the coming bits and any previously parsed data items to infer field lengths.

Returns:

Derived value with a raw_value attribute that can be used to get the original packet data.

Return type:

packets.ParameterDataTypes

class space_packet_parser.encodings.StringDataEncoding(*, encoding: str = 'UTF-8', byte_order: str | None = None, fixed_raw_length: int | None = None, dynamic_length_reference: str | None = None, discrete_lookup_length: List[space_packet_parser.comparisons.DiscreteLookup] | None = None, use_calibrated_value: bool | None = True, length_linear_adjuster: callable | None = None, termination_character: str | None = None, leading_length_size: int | None = None)

Bases: DataEncoding

<xtce:StringDataEncoding>

_supported_encodings = ('US-ASCII', 'ISO-8859-1', 'Windows-1252', 'UTF-8', 'UTF-16', 'UTF-16LE', 'UTF-16BE', 'UTF-32',...

encoding

buffer_length_specs

termination_character

fixed_length

leading_length_size

dynamic_length_reference

use_calibrated_value

discrete_lookup_length

length_linear_adjuster

_calculate_size(packet: space_packet_parser.packets.CCSDSPacket) → int

Calculate the size of the raw string buffer field

Parameters:

packet (packets.CCSDSPacket) – Partially parsed packet for referencing previous data fields.

Returns:

Size, in bits, of the raw string buffer.

Return type:

int

_get_raw_buffer(packet: space_packet_parser.packets.CCSDSPacket) → bytes

Get the raw string buffer as bytes. This will include any leading size or termination characters.

Notes

If the buffer size is not an integer number of bytes, the bytestring is padded at the end with zeros.

Parameters:

packet (packets.CCSDSPacket) – Packet parsed so far, for referencing previous values

Returns:

The raw string buffer, padded on the RHS to a byte boundary if the raw length specified is not an integer number of bytes.

Return type:

bytes

parse_value(packet: space_packet_parser.packets.CCSDSPacket, **kwargs) → space_packet_parser.packets.StrParameter

Parse a string value from packet data, possibly using previously parsed data items to inform parsing.

Parameters:

packet (CCSDSPacket) – Binary representation of the packet used to get the coming bits and any previously parsed data items to infer field lengths.

Returns:

Parsed string value. The raw_value attribute contains the raw string bytes buffer. This includes any leading size or termination character and may be a non-integer number of bytes, padded on the RHS.

Return type:

StrParameter

classmethod from_data_encoding_xml_element(element: lxml.etree.Element, ns: dict) → StringDataEncoding

Create a data encoding object from an <xtce:StringDataEncoding> XML element.

Notes

Raw strings in XTCE can be described in two ways:

1. Using a SizeInBits/Fixed/FixedSize element that specifies the length of the raw string, including any termination character or leading size integer. This is sometimes referred to as the “container” or “memory allocation” for the string.

2. Using a Variable element that contains either a DynamicValue or a DiscreteLookup to other parameters that specify the length of the raw string, including any termination character or leading size integer.

Derived strings in XTCE can be specified in two ways:

1. Via a TerminationCharacter element that contains the hex value of the termination character in the specified encoding (e.g. UTF-16BE).

2. Via a LeadingSize element that specifies the number of bits allocated at the beginning of the raw string for an integer that specifies the subsequent length, in bits, of the derived string.

Parameters:

• element (ElementTree.Element) – XML element

• ns (dict) – XML namespace dict

Return type:

cls

class space_packet_parser.encodings.NumericDataEncoding(size_in_bits: int, encoding: str, *, byte_order: str = 'mostSignificantByteFirst', default_calibrator: space_packet_parser.calibrators.Calibrator | None = None, context_calibrators: List[space_packet_parser.calibrators.ContextCalibrator] | None = None)

Bases: DataEncoding

Abstract class that is inherited by IntegerDataEncoding and FloatDataEncoding

_data_return_class

size_in_bits

encoding

byte_order

default_calibrator

context_calibrators

_calculate_size(packet: space_packet_parser.packets.CCSDSPacket) → int

Calculate the size of the data item in bits.

Parameters:

packet (CCSDSPacket) – Binary representation of the packet used to get the coming bits and any previously parsed data items to infer field lengths.

Returns:

Size of the data item in bits.

Return type:

int

abstract _get_raw_value(packet: space_packet_parser.packets.CCSDSPacket) → int | float

Read the raw value from the packet data

Parameters:

packet (CCSDSPacket) – Binary representation of the packet used to get the coming bits and any previously parsed data items to infer field lengths.

Returns:

Raw value

Return type:

int

static _twos_complement(val: int, bit_width: int) → int

Take the twos complement of val Used when parsing ints and some floats

parse_value(packet: space_packet_parser.packets.CCSDSPacket, **kwargs) → space_packet_parser.packets.FloatParameter | space_packet_parser.packets.IntParameter

Parse a value from packet data, possibly using previously parsed data items to inform parsing.

Parameters:

packet (CCSDSPacket) – Binary representation of the packet used to get the coming bits and any previously parsed data items to infer field lengths.

Returns:

Parsed data item as either a float or integer depending on the type of encoding.

Return type:

packets.FloatParameter or packets.IntParameter

class space_packet_parser.encodings.IntegerDataEncoding(size_in_bits: int, encoding: str, *, byte_order: str = 'mostSignificantByteFirst', default_calibrator: space_packet_parser.calibrators.Calibrator | None = None, context_calibrators: List[space_packet_parser.calibrators.ContextCalibrator] | None = None)

Bases: NumericDataEncoding

<xtce:IntegerDataEncoding>

_data_return_class

_get_raw_value(packet: space_packet_parser.packets.CCSDSPacket) → int

Read the raw value from the packet data

Parameters:

packet (CCSDSPacket) – Binary representation of the packet used to get the coming bits and any previously parsed data items to infer field lengths.

Returns:

Raw value

Return type:

int

classmethod from_data_encoding_xml_element(element: lxml.etree.Element, ns: dict) → IntegerDataEncoding

Create a data encoding object from an <xtce:IntegerDataEncoding> XML element.

Parameters:

• element (ElementTree.Element) – XML element

• ns (dict) – XML namespace dict

Return type:

cls

class space_packet_parser.encodings.FloatDataEncoding(size_in_bits: int, *, encoding: str = 'IEEE-754', byte_order: str = 'mostSignificantByteFirst', default_calibrator: space_packet_parser.calibrators.Calibrator | None = None, context_calibrators: List[space_packet_parser.calibrators.ContextCalibrator] | None = None)

Bases: NumericDataEncoding

<xtce:FloatDataEncoding>

_supported_encodings = ['IEEE-754', 'MIL-1750A']

_data_return_class

_get_raw_value(packet)

Read the data in as bytes and return a float representation.

classmethod from_data_encoding_xml_element(element: lxml.etree.Element, ns: dict) → FloatDataEncoding

Create a data encoding object from an <xtce:FloatDataEncoding> XML element.

Parameters:

• element (ElementTree.Element) – XML element

• ns (dict) – XML namespace dict

Return type:

cls

class space_packet_parser.encodings.BinaryDataEncoding(*, fixed_size_in_bits: int | None = None, size_reference_parameter: str | None = None, use_calibrated_value: bool = True, size_discrete_lookup_list: List[space_packet_parser.comparisons.DiscreteLookup] | None = None, linear_adjuster: callable | None = None)

Bases: DataEncoding

<xtce:BinaryDataEncoding>

fixed_size_in_bits

size_reference_parameter

use_calibrated_value

size_discrete_lookup_list

linear_adjuster

_calculate_size(packet: space_packet_parser.packets.CCSDSPacket) → int

Determine the number of bits in the binary field.

Returns:

Format string in the bitstring format. e.g. bin:1024

Return type:

Union[str, None]

parse_value(packet: space_packet_parser.packets.CCSDSPacket, **kwargs) → space_packet_parser.packets.BinaryParameter

Parse a value from packet data, possibly using previously parsed data items to inform parsing.

Parameters:

packet (CCSDSPacket) – Binary representation of the packet used to get the coming bits and any previously parsed data items to infer field lengths.

Returns:

Parsed binary data item.

Return type:

packets.BinaryParameter

classmethod from_data_encoding_xml_element(element: lxml.etree.Element, ns: dict) → BinaryDataEncoding

Create a data encoding object from an <xtce:BinaryDataEncoding> XML element.

Parameters:

• element (ElementTree.Element) – XML element

• ns (dict) – XML namespace dict

Return type:

BinaryDataEncoding