"""

Defines common socketcan functions.

"""

import errno

import logging

import os

import re

import struct

import subprocess

from typing import cast, Iterable, Optional

from can.interfaces.socketcan.constants import CAN_EFF_FLAG

from can import typechecking

log = logging.getLogger(__name__)

def pack_filters(can_filters: Optional[typechecking.CanFilters] = None) -> bytes:

if can_filters is None:

# Pass all messages

can_filters = [{"can_id": 0, "can_mask": 0}]

can_filter_fmt = "={}I".format(2 * len(can_filters))

filter_data = []

for can_filter in can_filters:

can_id = can_filter["can_id"]

can_mask = can_filter["can_mask"]

if "extended" in can_filter:

can_filter = cast(typechecking.CanFilterExtended, can_filter)

# Match on either 11-bit OR 29-bit messages instead of both

can_mask |= CAN_EFF_FLAG

if can_filter["extended"]:

can_id |= CAN_EFF_FLAG

filter_data.append(can_id)

filter_data.append(can_mask)

return struct.pack(can_filter_fmt, *filter_data)

_PATTERN_CAN_INTERFACE = re.compile(r"v?can\d+")

def find_available_interfaces() -> Iterable[str]:

"""Returns the names of all open can/vcan interfaces using

the ``ip link list`` command. If the lookup fails, an error

is logged to the console and an empty list is returned.

"""

try:

# adding "type vcan" would exclude physical can devices

command = ["ip", "-o", "link", "list", "up"]

output = subprocess.check_output(command, universal_newlines=True)

except Exception as e: # subprocess.CalledProcessError is too specific

log.error("failed to fetch opened can devices: %s", e)

return []

else:

# log.debug("find_available_interfaces(): output=\n%s", output)

# output contains some lines like "1: vcan42: <NOARP,UP,LOWER_UP> ..."

# extract the "vcan42" of each line

interfaces = [line.split(": ", 3)[1] for line in output.splitlines()]

log.debug(

"find_available_interfaces(): detected these interfaces (before filtering): %s",

interfaces,

)

return filter(_PATTERN_CAN_INTERFACE.match, interfaces)

def error_code_to_str(code: Optional[int]) -> str:

"""

Converts a given error code (errno) to a useful and human readable string.

:param code: a possibly invalid/unknown error code

:returns: a string explaining and containing the given error code, or a string

explaining that the errorcode is unknown if that is the case

"""

name = errno.errorcode.get(code, "UNKNOWN") # type: ignore

description = os.strerror(code) if code is not None else "NO DESCRIPTION AVAILABLE"

return f"{name} (errno {code}): {description}"