def from_bytes(cls, frame_bytes: bytes):
if not frame_is_enclosed_by_hdlc_flags(frame_bytes):
raise hdlc_exceptions.MissingHdlcFlags()
frame_format = BaseHdlcFrame.extract_format_field_from_bytes(frame_bytes)
if not frame_has_correct_length(frame_format.length, frame_bytes):
raise hdlc_exceptions.HdlcParsingError(
f"Frame data is not of length specified in frame format field. "
f"Should be {frame_format.length} but is {len(frame_bytes)}"
)
destination_address = address.HdlcAddress.destination_from_bytes(
frame_bytes, "server"
)
source_address = address.HdlcAddress.source_from_bytes(frame_bytes, "client")
fcs = frame_bytes[-3:-1]
frame = cls(destination_address, source_address)
if fcs != frame.fcs:
raise hdlc_exceptions.HdlcParsingError("FCS is not correct")
return frame
def from_bytes(cls, frame_bytes: bytes):
if not frame_is_enclosed_by_hdlc_flags(frame_bytes):
raise hdlc_exceptions.MissingHdlcFlags()
frame_format = BaseHdlcFrame.extract_format_field_from_bytes(frame_bytes)
if not frame_has_correct_length(frame_format.length, frame_bytes):
raise hdlc_exceptions.HdlcParsingError(
f"Frame data is not of length specified in frame format field. "
f"Should be {frame_format.length} but is {len(frame_bytes)}"
)
destination_address = address.HdlcAddress.destination_from_bytes(
frame_bytes, "client"
)
source_address = address.HdlcAddress.source_from_bytes(frame_bytes, "server")
hcs_position = 1 + 2 + destination_address.length + source_address.length + 1
hcs = frame_bytes[hcs_position : hcs_position + 2]
fcs = frame_bytes[-3:-1]
information = frame_bytes[hcs_position + 2 : -3]
frame = cls(destination_address, source_address, information)
if hcs != frame.hcs:
raise hdlc_exceptions.HdlcParsingError(
f"HCS is not correct. " f"Calculated: {frame.hcs!r}, in data: {hcs!r}"
)
if fcs != frame.fcs:
raise hdlc_exceptions.HdlcParsingError("FCS is not correct")
return frame
def from_bytes(cls, frame_bytes: bytes):
if not frame_is_enclosed_by_hdlc_flags(frame_bytes):
raise hdlc_exceptions.MissingHdlcFlags()
frame_format = BaseHdlcFrame.extract_format_field_from_bytes(frame_bytes)
if not frame_has_correct_length(frame_format.length, frame_bytes):
raise hdlc_exceptions.HdlcParsingError(
f"Frame data is not of length specified in frame format field. "
f"Should be {frame_format.length} but is {len(frame_bytes)}"
)
destination_address = address.HdlcAddress.destination_from_bytes(
frame_bytes, "client"
)
source_address = address.HdlcAddress.source_from_bytes(frame_bytes, "server")
control_byte_position = (
1 + 2 + destination_address.length + source_address.length
)
control_byte = frame_bytes[control_byte_position : control_byte_position + 1]
control = fields.ReceiveReadyControlField.from_bytes(control_byte)
fcs = frame_bytes[-3:-1]
frame = cls(
destination_address=destination_address,
source_address=source_address,
receive_sequence_number=control.receive_sequence_number,
final=control.is_final,
)
if fcs != frame.fcs:
raise hdlc_exceptions.HdlcParsingError("FCS is not correct")
return frame
def from_bytes(cls, in_bytes: bytes):
if len(in_bytes) != 2:
raise hdlc_exceptions.HdlcParsingError(
f"HDLC frame format length is {len(in_bytes)}, should be 2")
if not cls.correct_frame_format(in_bytes):
raise hdlc_exceptions.HdlcParsingError(
f"Received a HDLC frame of the incorrect format: {in_bytes!r}")
segmented = bool(in_bytes[0] & 0b00001000)
length = cls.get_length_from_bytes(in_bytes)
return cls(length, segmented)
def from_bytes(cls, frame_bytes: bytes):
if not frame_is_enclosed_by_hdlc_flags(frame_bytes):
raise hdlc_exceptions.MissingHdlcFlags()
frame_format = BaseHdlcFrame.extract_format_field_from_bytes(frame_bytes)
if not frame_has_correct_length(frame_format.length, frame_bytes):
raise hdlc_exceptions.HdlcParsingError(
f"Frame data is not of length specified in frame format field. "
f"Should be {frame_format.length} but is {len(frame_bytes)}"
)
destination_address = address.HdlcAddress.destination_from_bytes(
frame_bytes, "client"
)
source_address = address.HdlcAddress.source_from_bytes(frame_bytes, "server")
information_control_byte_position = (
1 + 2 + destination_address.length + source_address.length
)
information_control_byte = frame_bytes[
information_control_byte_position : information_control_byte_position + 1
]
information_control = fields.InformationControlField.from_bytes(
information_control_byte
)
hcs_position = 1 + 2 + destination_address.length + source_address.length + 1
hcs = frame_bytes[hcs_position : hcs_position + 2]
fcs = frame_bytes[-3:-1]
information = frame_bytes[hcs_position + 2 : -3]
frame = cls(
destination_address,
source_address,
information,
send_sequence_number=information_control.send_sequence_number,
receive_sequence_number=information_control.receive_sequence_number,
segmented=frame_format.segmented,
final=information_control.final,
)
if hcs != frame.hcs:
raise hdlc_exceptions.HdlcParsingError(
f"HCS is not correct Calculated: {frame.hcs!r}, in data: {hcs!r}"
)
if fcs != frame.fcs:
raise hdlc_exceptions.HdlcParsingError(
f"FCS is not correct, Calculated: {frame.fcs!r}, in data: {fcs!r}"
)
return frame