def validate_checksum(telegram):
"""
:param str telegram:
:raises ParseError:
:raises InvalidChecksumError:
"""
# Extract the part for which the checksum applies.
checksum_contents = re.search(r'\/.+\!', telegram, re.DOTALL)
# Extract the hexadecimal checksum value itself.
# The line ending '\r\n' for the checksum line can be ignored.
checksum_hex = re.search(r'((?<=\!)[0-9A-Z]{4})+', telegram)
if not checksum_contents or not checksum_hex:
raise ParseError(
'Failed to perform CRC validation because the telegram is '
'incomplete. The checksum and/or content values are missing.'
)
calculated_crc = TelegramParser.crc16(checksum_contents.group(0))
expected_crc = int(checksum_hex.group(0), base=16)
if calculated_crc != expected_crc:
raise InvalidChecksumError(
"Invalid telegram. The CRC checksum '{}' does not match the "
"expected '{}'".format(
calculated_crc,
expected_crc
)
)
def _parse(self, line):
# Match value groups, but exclude the parentheses
pattern = re.compile(r'((?<=\()[0-9a-zA-Z\.\*\-\:]{0,}(?=\)))')
values = re.findall(pattern, line)
if not self._is_line_wellformed(line, values):
raise ParseError("Invalid '%s' line for '%s'", line, self)
# Convert empty value groups to None for clarity.
values = [None if value == '' else value for value in values]
return self._parse_values(values)
def _parse(self, line):
# Match value groups, but exclude the parentheses
pattern = re.compile(r'((?<=\()[0-9a-zA-Z\.\*]{0,}(?=\)))+')
values = re.findall(pattern, line)
# Convert empty value groups to None for clarity.
values = [None if value == '' else value for value in values]
if not values or len(values) != len(self.value_formats):
raise ParseError("Invalid '%s' line for '%s'", line, self)
return [self.value_formats[i].parse(value)
for i, value in enumerate(values)]
def parse(self, telegram_data):
"""
Parse telegram from string to dict.
The telegram str type makes python 2.x integration easier.
:param str telegram_data: full telegram from start ('/') to checksum
('!ABCD') including line endings in between the telegram's lines
:rtype: dict
:returns: Shortened example:
{
..
r'\d-\d:96\.1\.1.+?\r\n': <CosemObject>, # EQUIPMENT_IDENTIFIER
r'\d-\d:1\.8\.1.+?\r\n': <CosemObject>, # ELECTRICITY_USED_TARIFF_1
r'\d-\d:24\.3\.0.+?\r\n.+?\r\n': <MBusObject>, # GAS_METER_READING
..
}
:raises ParseError:
:raises InvalidChecksumError:
"""
if self.apply_checksum_validation \
and self.telegram_specification['checksum_support']:
self.validate_checksum(telegram_data)
telegram = {}
for signature, parser in self.telegram_specification['objects'].items(
):
match = re.search(signature, telegram_data, re.DOTALL)
# All telegram specification lines/signatures are expected to be
# present.
if not match:
raise ParseError('Telegram specification does not match '
'telegram data')
telegram[signature] = parser.parse(match.group(0))
return telegram