def decode_field(self, field_definition: FieldDefinition) -> RecordField:
raw_bytes = self.reader.read_bytes(
field_definition.size) # TODO endianness
type_class = BASE_TYPE_NUMBER_TO_CLASS[field_definition.base_type]
decoded_value = type_class.from_bytes(raw_bytes)
if field_definition.number == Decoder.MESSAGE_INDEX_FIELD_NUMBER:
if field_definition.base_type != UnsignedInt16.metadata(
).base_type_number:
raise FITFileContentError(
'Message Index field number {} is expected to be of type {}, {} found',
Decoder.MESSAGE_INDEX_FIELD_NUMBER, UnsignedInt16.__name__,
type_class.__name__)
if field_definition.number == Decoder.PART_INDEX_FIELD_NUMBER:
if field_definition.base_type != UnsignedInt32.metadata(
).base_type_number:
raise FITFileContentError(
'Part Index field number {} is expected to be of type {}, {} found',
Decoder.MESSAGE_INDEX_FIELD_NUMBER, UnsignedInt32.__name__,
type_class.__name__)
if field_definition.number == Decoder.TIMESTAMP_FIELD_NUMBER:
if field_definition.base_type != UnsignedInt32.metadata(
).base_type_number:
raise FITFileContentError(
'Timestamp field number {} is expected to be of type {}, {} found',
Decoder.TIMESTAMP_FIELD_NUMBER, UnsignedInt32.__name__,
type_class.__name__)
self.most_recent_timestamp = decoded_value
return RecordField(decoded_value)
def decode_message_definition(
self, header: NormalRecordHeader) -> MessageDefinition:
reserved_byte = self.reader.read_byte()
if reserved_byte:
raise FITFileContentError(
'Reserved byte after record header is not 0')
architecture = Architecture(self.reader.read_byte())
global_message_number = UnsignedInt16.from_bytes(
self.reader.read_bytes(2))
number_of_fields = self.reader.read_byte()
field_definitions = tuple([
self.decode_field_definition() for _ in range(0, number_of_fields)
])
number_of_developer_fields = self.reader.read_byte(
) if header.has_developer_data else 0
developer_field_definitions = tuple([
self.decode_field_definition()
for _ in range(0, number_of_developer_fields)
])
definition = MessageDefinition(reserved_byte, architecture,
global_message_number,
field_definitions,
developer_field_definitions)
self.message_definitions[header.local_message_type] = definition
return definition
def decode_crc(self, allow_zero) -> UnsignedInt16:
computed_crc = self.reader.crc_calculator.current
expected_crc = self.reader.read_double_byte()
self.reader.crc_calculator.reset()
if allow_zero and expected_crc == UnsignedInt16(0):
return expected_crc
if computed_crc != expected_crc:
raise FITFileContentError(
f'Invalid CRC. Expected: {expected_crc}, computed: {computed_crc}'
)
return expected_crc
def read_double_byte(self) -> UnsignedInt16:
return UnsignedInt16(
np.array([self.read_byte()
for _ in range(0, 2)]).view(UnsignedInt16)[0])
def reset(self) -> None:
self.current = UnsignedInt16(0)
def __init__(self):
self.current = UnsignedInt16(0)
class CRCCalculator:
CRC_TABLE = [
UnsignedInt16(0x0000),
UnsignedInt16(0xCC01),
UnsignedInt16(0xD801),
UnsignedInt16(0x1400),
UnsignedInt16(0xF001),
UnsignedInt16(0x3C00),
UnsignedInt16(0x2800),
UnsignedInt16(0xE401),
UnsignedInt16(0xA001),
UnsignedInt16(0x6C00),
UnsignedInt16(0x7800),
UnsignedInt16(0xB401),
UnsignedInt16(0x5000),
UnsignedInt16(0x9C01),
UnsignedInt16(0x8801),
UnsignedInt16(0x4400),
]
x000F = UnsignedInt16(0x000F)
x0FFF = UnsignedInt16(0x0FFF)
def __init__(self):
self.current = UnsignedInt16(0)
def reset(self) -> None:
self.current = UnsignedInt16(0)
def new_byte(self, byte) -> None:
crc = self.current
tmp = CRCCalculator.CRC_TABLE[
crc & CRCCalculator.x000F] # tmp = crc_table[crc & 0xF];
crc = (crc >> 4) & CRCCalculator.x0FFF # crc = (crc >> 4) & 0x0FFF;
crc = crc ^ tmp ^ CRCCalculator.CRC_TABLE[
byte
& CRCCalculator.x000F] # crc = crc ^ tmp ^ crc_table[byte & 0xF];
tmp = CRCCalculator.CRC_TABLE[
crc & CRCCalculator.x000F] # tmp = crc_table[crc & 0xF];
crc = (crc >> 4) & CRCCalculator.x0FFF # crc = (crc >> 4) & 0x0FFF;
crc = crc ^ tmp ^ CRCCalculator.CRC_TABLE[
(byte >> 4) & CRCCalculator.
x000F] # crc = crc ^ tmp ^ crc_table[(byte >> 4) & 0xF];
self.current = crc