# 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 __future__ import absolute_import, division
import warnings
[docs]class Message(object):
"""
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 that the
documented ones.
"""
__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
"_dict" # see __getattr__
)
def __getattr__(self, key):
# TODO keep this for a version, in order to not break old code
# this entire method (as well as the _dict attribute in __slots__ and the __setattr__ method)
# can be removed in 4.0
# this method is only called if the attribute was not found elsewhere, like in __slots__
try:
warnings.warn("Custom attributes of messages are deprecated and will be removed in the next major version", DeprecationWarning)
return self._dict[key]
except KeyError:
raise AttributeError("'message' object has no attribute '{}'".format(key))
def __setattr__(self, key, value):
# see __getattr__
try:
super(Message, self).__setattr__(key, value)
except AttributeError:
warnings.warn("Custom attributes of messages are deprecated and will be removed in the next major version", DeprecationWarning)
self._dict[key] = value
@property
def id_type(self):
# TODO remove in 4.0
warnings.warn("Message.id_type is deprecated, use is_extended_id", DeprecationWarning)
return self.is_extended_id
@id_type.setter
def id_type(self, value):
# TODO remove in 4.0
warnings.warn("Message.id_type is deprecated, use is_extended_id", DeprecationWarning)
self.is_extended_id = value
def __init__(self, timestamp=0.0, arbitration_id=0, is_extended_id=None,
is_remote_frame=False, is_error_frame=False, channel=None,
dlc=None, data=None,
is_fd=False, bitrate_switch=False, error_state_indicator=False,
extended_id=True,
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._dict = dict() # see __getattr__
self.timestamp = timestamp
self.arbitration_id = arbitration_id
if is_extended_id is not None:
self.is_extended_id = is_extended_id
else:
self.is_extended_id = 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()
[docs] 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()):
try:
field_strings.append("'{}'".format(self.data.decode('utf-8')))
except UnicodeError:
pass
if self.channel is not None:
field_strings.append("Channel: {}".format(self.channel))
return " ".join(field_strings).strip()
def __len__(self):
return len(self.data)
def __bool__(self):
# For Python 3
return True
def __nonzero__(self):
# For Python 2
return self.__bool__()
def __repr__(self):
args = ["timestamp={}".format(self.timestamp),
"arbitration_id={:#x}".format(self.arbitration_id),
"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,
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
)
new._dict.update(self._dict)
return new
def __deepcopy__(self, memo):
new = Message(
timestamp=self.timestamp,
arbitration_id=self.arbitration_id,
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
)
new._dict.update(self._dict)
return new
def _check(self):
"""Checks if the message parameters are valid.
Assumes that the types are already correct.
:raises AssertionError: iff one or more attributes are invalid
"""
assert 0.0 <= self.timestamp, "the timestamp may not be negative"
assert not (self.is_remote_frame and self.is_error_frame), \
"a message cannot be a remote and an error frame at the sane time"
assert 0 <= self.arbitration_id, "arbitration IDs may not be negative"
if self.is_extended_id:
assert self.arbitration_id < 0x20000000, "Extended arbitration IDs must be less than 2^29"
else:
assert self.arbitration_id < 0x800, "Normal arbitration IDs must be less than 2^11"
assert 0 <= self.dlc, "DLC may not be negative"
if self.is_fd:
assert self.dlc <= 64, "DLC was {} but it should be <= 64 for CAN FD frames".format(self.dlc)
else:
assert self.dlc <= 8, "DLC was {} but it should be <= 8 for normal CAN frames".format(self.dlc)
if not self.is_remote_frame:
assert self.dlc == len(self.data), "the length of the DLC and the length of the data must match up"
if not self.is_fd:
assert not self.bitrate_switch, "bitrate switch is only allowed for CAN FD frames"
assert not self.error_state_indicator, "error stat indicator is only allowed for CAN FD frames"
[docs] 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
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
)
)