kopia lustrzana https://github.com/projecthorus/horusdemodlib
203 wiersze
6.9 KiB
Python
203 wiersze
6.9 KiB
Python
#
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# HorusLib - Binary Packet Decoder Functions
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#
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import codecs
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import struct
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import time
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from .delegates import *
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from .checksums import *
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from .payloads import HORUS_CUSTOM_FIELDS, HORUS_PAYLOAD_LIST
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#
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# Horus Binary V1 and V2 Packet Formats
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#
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HORUS_PACKET_FORMATS = {
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'horus_binary_v1': {
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'name': 'Horus Binary v1 22 Byte Format',
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'length': 22,
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'struct': '<BH3sffHBBbBH',
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'checksum': 'crc16',
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'fields': [
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['payload_id', 'payload_id'],
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['sequence_number', 'none'],
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['time', 'time_hms'],
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['latitude', 'degree_float'],
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['longitude', 'degree_float'],
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['altitude', 'none'],
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['speed', 'none'],
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['satellites', 'none'],
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['temperature', 'none'],
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['battery_voltage', 'battery_5v_byte'],
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['checksum', 'none']
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]
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},
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'horus_binary_v2_16byte': {
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'name': 'Horus Binary v2 16 Byte Format',
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'length': 16,
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'struct': '<BBH3s3sHBBH',
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'checksum': 'crc16',
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'fields': [
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['payload_id', 'payload_id'],
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['sequence_number', 'none'],
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['time', 'time_biseconds'],
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['latitude', 'degree_fixed3'],
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['longitude', 'degree_fixed3'],
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['altitude', 'none'],
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['battery_voltage', 'battery_5v_byte'],
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['flags', 'none'],
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['checksum', 'none']
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]
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},
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'horus_binary_v2_32byte': {
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'name': 'Horus Binary v2 32 Byte Format',
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'length': 32,
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'struct': '<HH3sffHBBbB9sH',
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'checksum': 'crc16',
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'fields': [
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['payload_id', 'payload_id'],
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['sequence_number', 'none'],
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['time', 'time_hms'],
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['latitude', 'degree_float'],
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['longitude', 'degree_float'],
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['altitude', 'none'],
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['speed', 'none'],
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['satellites', 'none'],
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['temperature', 'none'],
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['battery_voltage', 'battery_5v_byte'],
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['custom', 'custom'],
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['checksum', 'none']
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]
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}
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}
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# Lookup for packet length to the appropriate format.
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HORUS_LENGTH_TO_FORMAT = {
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22: 'horus_binary_v1',
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16: 'horus_binary_v2_16byte',
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32: 'horus_binary_v2_32byte'
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}
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def decode_packet(data:bytes, packet_format:dict = None) -> dict:
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"""
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Attempt to decode a set of bytes based on a provided packet format.
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"""
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if packet_format is None:
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# Attempt to lookup the format based on the length of the data if it has not been provided.
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if len(data) in HORUS_LENGTH_TO_FORMAT:
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packet_format = HORUS_PACKET_FORMATS[HORUS_LENGTH_TO_FORMAT[len(data)]]
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# Output dictionary
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_output = {
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'packet_format': packet_format,
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'crc_ok': False,
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'payload_id': 0
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}
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# Check the length provided in the packet format matches up with the length defined by the struct.
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_struct_length = struct.calcsize(packet_format['struct'])
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if _struct_length != packet_format['length']:
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raise ValueError(f"Decoder - Provided length {packet_format['length']} and struct length ({_struct_length}) do not match!")
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# Check the length of the input data bytes matches that of the struct.
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if len(data) != _struct_length:
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raise ValueError(f"Decoder - Input data has length {len(data)}, should be length {_struct_length}.")
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# Check the Checksum
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_crc_ok = check_packet_crc(data, checksum=packet_format['checksum'])
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if not _crc_ok:
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raise ValueError("Decoder - CRC Failure.")
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else:
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_output['crc_ok'] = True
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# Now try and decode the data.
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_raw_fields = struct.unpack(packet_format['struct'], data)
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# Check the number of decoded fields is equal to the number of field definitions in the packet format.
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if len(_raw_fields) != len(packet_format['fields']):
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raise ValueError(f"Decoder - Packet format defines {len(packet_format['fields'])} fields, got {len(_raw_fields)} from struct.")
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# Now we can start extracting and formatting fields.
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_ukhas_fields = []
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for _i in range(len(_raw_fields)):
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_field_name = packet_format['fields'][_i][0]
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_field_type = packet_format['fields'][_i][1]
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_field_data = _raw_fields[_i]
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if _field_name == 'custom':
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# Attempt to interpret custom fields.
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# Note: This requires that the payload ID has been decoded prior to this field being parsed.
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if _output['payload_id'] in HORUS_CUSTOM_FIELDS:
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(_custom_data, _custom_str) = decode_custom_fields(_field_data, _output['payload_id'])
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# Add custom fields to string
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_ukhas_fields.append(_custom_str)
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# Add custom fields to output dict.
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for _field in _custom_data:
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_output[_field] = _custom_data[_field]
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# Ignore checksum field. (and maybe other fields?)
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elif _field_name not in ['checksum']:
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# Decode field to string.
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(_decoded, _decoded_str) = decode_field(_field_type, _field_data)
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_output[_field_name] = _decoded
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_ukhas_fields.append(_decoded_str)
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# Convert to a UKHAS-compliant string.
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_ukhas_str = ",".join(_ukhas_fields)
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_ukhas_crc = ukhas_crc(_ukhas_str.encode('ascii'))
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_output['ukhas_str'] = "$$" + _ukhas_str + "*" + _ukhas_crc
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return _output
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def hex_to_bytes(data:str) -> bytes:
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""" Convert a string of hexadeximal digits to a bytes representation """
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try:
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_binary_string = codecs.decode(data, 'hex')
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return _binary_string
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except TypeError as e:
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logging.error("Error parsing line as hexadecimal (%s): %s" % (str(e), data))
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return None
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if __name__ == "__main__":
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tests = [
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['horus_binary_v1', b'\x01\x12\x00\x00\x00\x23\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x1C\x9A\x95\x45', ''],
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['horus_binary_v1', b'\x01\x12\x00\x00\x00\x23\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x1C\x9A\x95\x45', 'error'],
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['horus_binary_v2_16byte', b'\x01\x12\x02\x00\x02\xbc\xeb!AR\x10\x00\xff\x00\xe1\x7e', ''],
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# id seq_no HH MM SS lat lon alt spd sat tmp bat custom data -----------------------| crc16
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['horus_binary_v2_32byte', b'\xFF\xFF\x12\x00\x00\x00\x23\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xe8\x82', '']
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]
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for _test in tests:
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_format = _test[0]
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_input = _test[1]
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_output = _test[2]
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try:
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_decoded = decode_packet(_input)
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print(f"Input ({_format}): {str(_input)} - Output: {_decoded['ukhas_str']}")
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print(_decoded)
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# Insert assert checks here.
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except ValueError as e:
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print(f"Input ({_format}): {str(_input)} - Caught Error: {str(e)}")
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assert(_output == 'error')
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print("All tests passed!")
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