# coding: utf-8
"""
Utilities and configuration file parsing.
"""
import json
import os
import os.path
import platform
import re
import logging
from configparser import ConfigParser
import can
from can.interfaces import VALID_INTERFACES
log = logging.getLogger("can.util")
# List of valid data lengths for a CAN FD message
CAN_FD_DLC = [0, 1, 2, 3, 4, 5, 6, 7, 8, 12, 16, 20, 24, 32, 48, 64]
REQUIRED_KEYS = ["interface", "channel"]
CONFIG_FILES = ["~/can.conf"]
if platform.system() == "Linux":
CONFIG_FILES.extend(["/etc/can.conf", "~/.can", "~/.canrc"])
elif platform.system() == "Windows" or platform.python_implementation() == "IronPython":
CONFIG_FILES.extend(["can.ini", os.path.join(os.getenv("APPDATA", ""), "can.ini")])
[docs]def load_file_config(path=None, section="default"):
"""
Loads configuration from file with following content::
[default]
interface = socketcan
channel = can0
:param path:
path to config file. If not specified, several sensible
default locations are tried depending on platform.
:param section:
name of the section to read configuration from.
"""
config = ConfigParser()
if path is None:
config.read([os.path.expanduser(path) for path in CONFIG_FILES])
else:
config.read(path)
_config = {}
if config.has_section(section):
_config.update(dict((key, val) for key, val in config.items(section)))
return _config
[docs]def load_environment_config(context=None):
"""
Loads config dict from environmental variables (if set):
* CAN_INTERFACE
* CAN_CHANNEL
* CAN_BITRATE
* CAN_CONFIG
if context is supplied, "_{context}" is appended to the environment
variable name we will look at. For example if context="ABC":
* CAN_INTERFACE_ABC
* CAN_CHANNEL_ABC
* CAN_BITRATE_ABC
* CAN_CONFIG_ABC
"""
mapper = {
"interface": "CAN_INTERFACE",
"channel": "CAN_CHANNEL",
"bitrate": "CAN_BITRATE",
}
context_suffix = "_{}".format(context) if context else ""
config = {}
can_config_key = "CAN_CONFIG" + context_suffix
if can_config_key in os.environ:
config = json.loads(os.environ.get(can_config_key))
for key, val in mapper.items():
if val in os.environ:
config[key] = os.environ.get(val + context_suffix)
return config
[docs]def load_config(path=None, config=None, context=None):
"""
Returns a dict with configuration details which is loaded from (in this order):
- config
- can.rc
- Environment variables CAN_INTERFACE, CAN_CHANNEL, CAN_BITRATE
- Config files ``/etc/can.conf`` or ``~/.can`` or ``~/.canrc``
where the latter may add or replace values of the former.
Interface can be any of the strings from ``can.VALID_INTERFACES`` for example:
kvaser, socketcan, pcan, usb2can, ixxat, nican, virtual.
.. note::
The key ``bustype`` is copied to ``interface`` if that one is missing
and does never appear in the result.
:param path:
Optional path to config file.
:param config:
A dict which may set the 'interface', and/or the 'channel', or neither.
It may set other values that are passed through.
:param context:
Extra 'context' pass to config sources. This can be use to section
other than 'default' in the configuration file.
:return:
A config dictionary that should contain 'interface' & 'channel'::
{
'interface': 'python-can backend interface to use',
'channel': 'default channel to use',
# possibly more
}
Note ``None`` will be used if all the options are exhausted without
finding a value.
All unused values are passed from ``config`` over to this.
:raises:
NotImplementedError if the ``interface`` isn't recognized
"""
# start with an empty dict to apply filtering to all sources
given_config = config or {}
config = {}
# use the given dict for default values
config_sources = [
given_config,
can.rc,
lambda _context: load_environment_config( # pylint: disable=unnecessary-lambda
_context
),
lambda _context: load_environment_config(),
lambda _context: load_file_config(path, _context),
lambda _context: load_file_config(path),
]
# Slightly complex here to only search for the file config if required
for cfg in config_sources:
if callable(cfg):
cfg = cfg(context)
# remove legacy operator (and copy to interface if not already present)
if "bustype" in cfg:
if "interface" not in cfg or not cfg["interface"]:
cfg["interface"] = cfg["bustype"]
del cfg["bustype"]
# copy all new parameters
for key in cfg:
if key not in config:
config[key] = cfg[key]
# substitute None for all values not found
for key in REQUIRED_KEYS:
if key not in config:
config[key] = None
if config["interface"] not in VALID_INTERFACES:
raise NotImplementedError(
"Invalid CAN Bus Type - {}".format(config["interface"])
)
if "bitrate" in config:
config["bitrate"] = int(config["bitrate"])
if "fd" in config:
config["fd"] = config["fd"] not in ("0", "False", "false")
if "data_bitrate" in config:
config["data_bitrate"] = int(config["data_bitrate"])
# Create bit timing configuration if given
timing_conf = {}
for key in (
"f_clock",
"brp",
"tseg1",
"tseg2",
"sjw",
"nof_samples",
"btr0",
"btr1",
):
if key in config:
timing_conf[key] = int(config[key], base=0)
del config[key]
if timing_conf:
timing_conf["bitrate"] = config.get("bitrate")
config["timing"] = can.BitTiming(**timing_conf)
can.log.debug("can config: {}".format(config))
return config
[docs]def set_logging_level(level_name=None):
"""Set the logging level for the "can" logger.
Expects one of: 'critical', 'error', 'warning', 'info', 'debug', 'subdebug'
"""
can_logger = logging.getLogger("can")
try:
can_logger.setLevel(getattr(logging, level_name.upper()))
except AttributeError:
can_logger.setLevel(logging.DEBUG)
log.debug("Logging set to {}".format(level_name))
[docs]def len2dlc(length):
"""Calculate the DLC from data length.
:param int length: Length in number of bytes (0-64)
:returns: DLC (0-15)
:rtype: int
"""
if length <= 8:
return length
for dlc, nof_bytes in enumerate(CAN_FD_DLC):
if nof_bytes >= length:
return dlc
return 15
[docs]def dlc2len(dlc):
"""Calculate the data length from DLC.
:param int dlc: DLC (0-15)
:returns: Data length in number of bytes (0-64)
:rtype: int
"""
return CAN_FD_DLC[dlc] if dlc <= 15 else 64
[docs]def channel2int(channel):
"""Try to convert the channel to an integer.
:param channel:
Channel string (e.g. can0, CAN1) or integer
:returns: Channel integer or `None` if unsuccessful
:rtype: int
"""
if channel is None:
return None
if isinstance(channel, int):
return channel
# String and byte objects have a lower() method
if hasattr(channel, "lower"):
match = re.match(r".*(\d+)$", channel)
if match:
return int(match.group(1))
return None
if __name__ == "__main__":
print("Searching for configuration named:")
print("\n".join(CONFIG_FILES))
print()
print("Settings:")
print(load_config())