space_packet_parser.packets

Packet containers and parsing utilities for space packets.

Attributes

BuiltinDataTypes
ParameterDataTypes

Classes

_Parameter	Mixin class for storing access to the raw value of a parsed data item.
BinaryParameter	A class to represent a binary data item.
BoolParameter	A class to represent a parsed boolean data item.
FloatParameter	A class to represent a float data item.
IntParameter	A class to represent a integer data item.
StrParameter	A class to represent a string data item.
RawPacketData	A class to represent raw packet data as bytes but whose length is represented by bit length.
CCSDSPacket	CCSDS Packet
Parseable	Defines an object that can be parsed from packet data.
SequenceContainer	<xtce:SequenceContainer>

Functions

_extract_bits(data, start_bit, nbits)

Extract nbits from the data starting from the least significant end.

Module Contents

space_packet_parser.packets.BuiltinDataTypes

class space_packet_parser.packets._Parameter

Mixin class for storing access to the raw value of a parsed data item.

The raw value is the closest representation of the data item as it appears in the packet. e.g. bytes for binary data, int for integer data, etc. It has not been calibrated or adjusted in any way and is an easy way for user’s to debug the transformations that happened after the fact.

Notes

We need to override the __new__ method to store the raw value of the data item on immutable built-in types. So this is just a way of allowing us to inject our own attribute into the built-in types.

class space_packet_parser.packets.BinaryParameter

Bases: _Parameter, bytes

A class to represent a binary data item.

class space_packet_parser.packets.BoolParameter

Bases: _Parameter, int

A class to represent a parsed boolean data item.

__repr__() → str

Return repr(self).

class space_packet_parser.packets.FloatParameter

Bases: _Parameter, float

A class to represent a float data item.

class space_packet_parser.packets.IntParameter

Bases: _Parameter, int

A class to represent a integer data item.

class space_packet_parser.packets.StrParameter

Bases: _Parameter, str

A class to represent a string data item.

space_packet_parser.packets.ParameterDataTypes

class space_packet_parser.packets.RawPacketData(data: bytes, *, pos: int = 0)

Bases: bytes

A class to represent raw packet data as bytes but whose length is represented by bit length.

This class is a subclass of bytes and is used to represent the raw packet data in a more readable way. It is used to store the raw packet data in the Packet class and used to keep track of the current parsing position.

Parameters:

data (bytes) – Raw packet data. Full CCSDS packets are always an integer number of bytes.

pos

_nbits

__len__()

Return len(self).

__repr__()

Return repr(self).

read_as_bytes(nbits: int) → bytes

Read a number of bits from the packet data as bytes. Reads minimum number of complete bytes required to capture nbits. Moves pos cursor nbits forward, even if nbits is not an integer number of bytes.

Parameters:

nbits (int) – Number of bits to read

Returns:

Raw bytes from the packet data

Return type:

bytes

read_as_int(nbits: int) → int

Read a number of bits from the packet data as an integer.

Parameters:

nbits (int) – Number of bits to read

Returns:

Integer representation of the bits read from the packet

Return type:

int

class space_packet_parser.packets.CCSDSPacket(*args, raw_data: bytes = b'', **kwargs)

Bases: dict

CCSDS Packet

Container that stores the raw packet data (bytes) as an instance attribute and the parsed data items in a dict interface. A CCSDSPacket generally begins as an empty dictionary that gets filled as the packet is parsed. The first 7 items in the dictionary make up the packet header (accessed with CCSDSPacket.header), and the rest of the items make up the user data (accessed with CCSDSPacket.user_data). To access the raw bytes of the packet, use the CCSDSPacket.raw_data attribute.

Parameters:

• *args (Mapping or Iterable) – Initial items to store in the packet, passed to the dict() constructor.

• raw_data (bytes, optional) – The binary data for a single packet.

• **kwargs (dict) – Additional packet items to store, passed to the dict() constructor.

raw_data

property header: dict

The header content of the packet.

property user_data: dict

The user data content of the packet.

class space_packet_parser.packets.Parseable

Bases: Protocol

Defines an object that can be parsed from packet data.

parse(packet: CCSDSPacket, **parse_value_kwargs) → None

Parse this entry from the packet data and add the necessary items to the packet.

class space_packet_parser.packets.SequenceContainer

Bases: Parseable

<xtce:SequenceContainer>

Parameters:

• name (str) – Container name

• entry_list (list) – List of Parameter objects

• long_description (str) – Long description of the container

• base_container_name (str) – Name of the base container from which this may inherit if restriction criteria are met.

• restriction_criteria (list) – A list of MatchCriteria elements that evaluate to determine whether the SequenceContainer should be included.

• abstract (bool) – True if container has abstract=true attribute. False otherwise.

• inheritors (list, Optional) – List of SequenceContainer objects that may inherit this one’s entry list if their restriction criteria are met. Any SequenceContainers with this container as base_container_name should be listed here.

name: str

entry_list: list

short_description: str | None = None

long_description: str | None = None

base_container_name: str | None = None

restriction_criteria: list | None

abstract: bool = False

inheritors: List[SequenceContainer] | None

__post_init__()

parse(packet: CCSDSPacket, **parse_value_kwargs) → None

Parse the entry list of parameters/containers in the order they are expected in the packet.

This could be recursive if the entry list contains SequenceContainers.

space_packet_parser.packets._extract_bits(data: bytes, start_bit: int, nbits: int)

Extract nbits from the data starting from the least significant end.

If data = 00110101 11001010, start_bit = 2, nbits = 9, then the bits extracted are “110101110”. Those bits are turned into a Python integer and returned.

Parameters:

• data (bytes) – Data to extract bits from

• start_bit (int) – Starting bit location within the data

• nbits (int) – Number of bits to extract

Returns:

Extracted bits as an integer

Return type:

int