Source code for can.message

# coding: utf-8

This module contains the implementation of :class:`can.Message`.

.. note::
    Could use `@dataclass <>`__
    starting with Python 3.7.

from typing import Optional, Union

from . import typechecking

from copy import deepcopy
from math import isinf, isnan

[docs]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: float = 0.0, arbitration_id: int = 0, is_extended_id: bool = True, is_remote_frame: bool = False, is_error_frame: bool = False, channel: Optional[typechecking.Channel] = None, dlc: Optional[int] = None, data: Optional[typechecking.CanData] = None, is_fd: bool = False, bitrate_switch: bool = False, error_state_indicator: bool = False, check: bool = False, ): """ To create a message object, simply provide any of the below attributes together with additional parameters as keyword arguments to the constructor. :param 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 = 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: = bytearray() elif isinstance(data, bytearray): = data else: try: = bytearray(data) except TypeError: err = "Couldn't create message from {} ({})".format(data, type(data)) raise TypeError(err) if dlc is None: self.dlc = len( else: self.dlc = dlc if check: self._check()
[docs] def __str__(self) -> str: 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 is not None: for index in range(0, min(self.dlc, len( data_strings.append("{0:02x}".format([index])) if data_strings: # if not empty field_strings.append(" ".join(data_strings).ljust(24, " ")) else: field_strings.append(" " * 24) if ( is not None) and ( field_strings.append("'{}'".format("utf-8", "replace"))) if is not None: try: field_strings.append("Channel: {}".format( except UnicodeEncodeError: pass return " ".join(field_strings).strip()
def __len__(self) -> int: # return the dlc such that it also works on remote frames return self.dlc def __bool__(self) -> bool: return True def __repr__(self) -> str: 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 is not None: args.append("channel={!r}".format( data = ["{:#02x}".format(byte) for byte in] 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: Optional[str]) -> str: if not format_spec: return self.__str__() else: raise ValueError("non empty format_specs are not supported") def __bytes__(self) -> bytes: return bytes( def __copy__(self) -> "Message": 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,, dlc=self.dlc,, is_fd=self.is_fd, bitrate_switch=self.bitrate_switch, error_state_indicator=self.error_state_indicator, ) return new def __deepcopy__(self, memo: dict) -> "Message": 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(, memo), dlc=self.dlc, data=deepcopy(, 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 raise ValueError("remote frames may not carry any data") elif self.dlc != len( 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" )
[docs] def equals( self, other: "Message", timestamp_delta: Optional[Union[float, int]] = 1.0e-6 ) -> bool: """ Compares a given message with this one. :param other: the message to compare with :param timestamp_delta: the maximum difference at which two timestamps are still considered equal or None to not compare timestamps :return: True iff the given message equals this one """ # see 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 == and self.is_remote_frame == other.is_remote_frame and self.is_error_frame == other.is_error_frame and == and self.is_fd == other.is_fd and self.bitrate_switch == other.bitrate_switch and self.error_state_indicator == other.error_state_indicator ) )