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317 lines (267 loc) · 11 KB
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# coding: utf-8
"""
This module contains the implementation of :class:`can.Message`.
.. note::
Could use `@dataclass <https://docs.python.org/3.7/library/dataclasses.html>`__
starting with Python 3.7.
"""
from copy import deepcopy
from math import isinf, isnan
class Message:
"""
The :class:`~can.Message` object is used to represent CAN messages for
sending, receiving and other purposes like converting between different
logging formats.
Messages can use extended identifiers, be remote or error frames, contain
data and may be associated to a channel.
Messages are always compared by identity and never by value, because that
may introduce unexpected behaviour. See also :meth:`~can.Message.equals`.
:func:`~copy.copy`/:func:`~copy.deepcopy` is supported as well.
Messages do not support "dynamic" attributes, meaning any others than the
documented ones, since it uses :attr:`~object.__slots__`.
"""
__slots__ = (
"timestamp",
"arbitration_id",
"is_extended_id",
"is_remote_frame",
"is_error_frame",
"channel",
"dlc",
"data",
"is_fd",
"bitrate_switch",
"error_state_indicator",
"__weakref__", # support weak references to messages
)
def __init__(
self,
timestamp=0.0,
arbitration_id=0,
is_extended_id=True,
is_remote_frame=False,
is_error_frame=False,
channel=None,
dlc=None,
data=None,
is_fd=False,
bitrate_switch=False,
error_state_indicator=False,
check=False,
):
"""
To create a message object, simply provide any of the below attributes
together with additional parameters as keyword arguments to the constructor.
:param bool check: By default, the constructor of this class does not strictly check the input.
Thus, the caller must prevent the creation of invalid messages or
set this parameter to `True`, to raise an Error on invalid inputs.
Possible problems include the `dlc` field not matching the length of `data`
or creating a message with both `is_remote_frame` and `is_error_frame` set to `True`.
:raises ValueError: iff `check` is set to `True` and one or more arguments were invalid
"""
self.timestamp = timestamp
self.arbitration_id = arbitration_id
self.is_extended_id = is_extended_id
self.is_remote_frame = is_remote_frame
self.is_error_frame = is_error_frame
self.channel = channel
self.is_fd = is_fd
self.bitrate_switch = bitrate_switch
self.error_state_indicator = error_state_indicator
if data is None or is_remote_frame:
self.data = bytearray()
elif isinstance(data, bytearray):
self.data = data
else:
try:
self.data = bytearray(data)
except TypeError:
err = "Couldn't create message from {} ({})".format(data, type(data))
raise TypeError(err)
if dlc is None:
self.dlc = len(self.data)
else:
self.dlc = dlc
if check:
self._check()
def __str__(self):
field_strings = ["Timestamp: {0:>15.6f}".format(self.timestamp)]
if self.is_extended_id:
arbitration_id_string = "ID: {0:08x}".format(self.arbitration_id)
else:
arbitration_id_string = "ID: {0:04x}".format(self.arbitration_id)
field_strings.append(arbitration_id_string.rjust(12, " "))
flag_string = " ".join(
[
"X" if self.is_extended_id else "S",
"E" if self.is_error_frame else " ",
"R" if self.is_remote_frame else " ",
"F" if self.is_fd else " ",
"BS" if self.bitrate_switch else " ",
"EI" if self.error_state_indicator else " ",
]
)
field_strings.append(flag_string)
field_strings.append("DLC: {0:2d}".format(self.dlc))
data_strings = []
if self.data is not None:
for index in range(0, min(self.dlc, len(self.data))):
data_strings.append("{0:02x}".format(self.data[index]))
if data_strings: # if not empty
field_strings.append(" ".join(data_strings).ljust(24, " "))
else:
field_strings.append(" " * 24)
if (self.data is not None) and (self.data.isalnum()):
field_strings.append("'{}'".format(self.data.decode("utf-8", "replace")))
if self.channel is not None:
try:
field_strings.append("Channel: {}".format(self.channel))
except UnicodeEncodeError:
pass
return " ".join(field_strings).strip()
def __len__(self):
# return the dlc such that it also works on remote frames
return self.dlc
def __bool__(self):
return True
def __repr__(self):
args = [
"timestamp={}".format(self.timestamp),
"arbitration_id={:#x}".format(self.arbitration_id),
"is_extended_id={}".format(self.is_extended_id),
]
if self.is_remote_frame:
args.append("is_remote_frame={}".format(self.is_remote_frame))
if self.is_error_frame:
args.append("is_error_frame={}".format(self.is_error_frame))
if self.channel is not None:
args.append("channel={!r}".format(self.channel))
data = ["{:#02x}".format(byte) for byte in self.data]
args += ["dlc={}".format(self.dlc), "data=[{}]".format(", ".join(data))]
if self.is_fd:
args.append("is_fd=True")
args.append("bitrate_switch={}".format(self.bitrate_switch))
args.append("error_state_indicator={}".format(self.error_state_indicator))
return "can.Message({})".format(", ".join(args))
def __format__(self, format_spec):
if not format_spec:
return self.__str__()
else:
raise ValueError("non empty format_specs are not supported")
def __bytes__(self):
return bytes(self.data)
def __copy__(self):
new = Message(
timestamp=self.timestamp,
arbitration_id=self.arbitration_id,
is_extended_id=self.is_extended_id,
is_remote_frame=self.is_remote_frame,
is_error_frame=self.is_error_frame,
channel=self.channel,
dlc=self.dlc,
data=self.data,
is_fd=self.is_fd,
bitrate_switch=self.bitrate_switch,
error_state_indicator=self.error_state_indicator,
)
return new
def __deepcopy__(self, memo):
new = Message(
timestamp=self.timestamp,
arbitration_id=self.arbitration_id,
is_extended_id=self.is_extended_id,
is_remote_frame=self.is_remote_frame,
is_error_frame=self.is_error_frame,
channel=deepcopy(self.channel, memo),
dlc=self.dlc,
data=deepcopy(self.data, memo),
is_fd=self.is_fd,
bitrate_switch=self.bitrate_switch,
error_state_indicator=self.error_state_indicator,
)
return new
def _check(self):
"""Checks if the message parameters are valid.
Assumes that the types are already correct.
:raises ValueError: iff one or more attributes are invalid
"""
if self.timestamp < 0.0:
raise ValueError("the timestamp may not be negative")
if isinf(self.timestamp):
raise ValueError("the timestamp may not be infinite")
if isnan(self.timestamp):
raise ValueError("the timestamp may not be NaN")
if self.is_remote_frame and self.is_error_frame:
raise ValueError(
"a message cannot be a remote and an error frame at the sane time"
)
if self.arbitration_id < 0:
raise ValueError("arbitration IDs may not be negative")
if self.is_extended_id:
if self.arbitration_id >= 0x20000000:
raise ValueError("Extended arbitration IDs must be less than 2^29")
elif self.arbitration_id >= 0x800:
raise ValueError("Normal arbitration IDs must be less than 2^11")
if self.dlc < 0:
raise ValueError("DLC may not be negative")
if self.is_fd:
if self.dlc > 64:
raise ValueError(
"DLC was {} but it should be <= 64 for CAN FD frames".format(
self.dlc
)
)
elif self.dlc > 8:
raise ValueError(
"DLC was {} but it should be <= 8 for normal CAN frames".format(
self.dlc
)
)
if self.is_remote_frame:
if self.data:
raise ValueError("remote frames may not carry any data")
elif self.dlc != len(self.data):
raise ValueError(
"the DLC and the length of the data must match up for non remote frames"
)
if not self.is_fd:
if self.bitrate_switch:
raise ValueError("bitrate switch is only allowed for CAN FD frames")
if self.error_state_indicator:
raise ValueError(
"error state indicator is only allowed for CAN FD frames"
)
def equals(self, other, timestamp_delta=1.0e-6):
"""
Compares a given message with this one.
:param can.Message other: the message to compare with
:type timestamp_delta: float or int or None
:param timestamp_delta: the maximum difference at which two timestamps are
still considered equal or None to not compare timestamps
:rtype: bool
:return: True iff the given message equals this one
"""
# see https://github.com/hardbyte/python-can/pull/413 for a discussion
# on why a delta of 1.0e-6 was chosen
return (
# check for identity first and finish fast
self is other
or
# then check for equality by value
(
(
timestamp_delta is None
or abs(self.timestamp - other.timestamp) <= timestamp_delta
)
and self.arbitration_id == other.arbitration_id
and self.is_extended_id == other.is_extended_id
and self.dlc == other.dlc
and self.data == other.data
and self.is_remote_frame == other.is_remote_frame
and self.is_error_frame == other.is_error_frame
and self.channel == other.channel
and self.is_fd == other.is_fd
and self.bitrate_switch == other.bitrate_switch
and self.error_state_indicator == other.error_state_indicator
)
)
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