# -*- coding: utf-8 -*-

from __future__ import print_function

import abc

import logging

logger = logging.getLogger(__name__)

class BusABC(object):

"""CAN Bus Abstract Base Class

Concrete implementations must implement the following methods:

* send

* recv

As well as setting the `channel_info` attribute to a string describing the

interface.

"""

#: a string describing the underlying bus channel

channel_info = 'unknown'

@abc.abstractmethod

def __init__(self, channel=None, can_filters=None, **config):

"""

:param channel:

The can interface identifier. Expected type is backend dependent.

:param list can_filters:

A list of dictionaries each containing a "can_id" and a "can_mask".

>>> [{"can_id": 0x11, "can_mask": 0x21}]

:param dict config:

Any backend dependent configurations are passed in this dictionary

"""

@abc.abstractmethod

def recv(self, timeout=None):

"""Block waiting for a message from the Bus.

:return:

None on timeout or a :class:`can.Message` object.

"""

raise NotImplementedError("Trying to read from a write only bus?")

@abc.abstractmethod

def send(self, msg):

"""Transmit a message to CAN bus.

Override this method to enable the transmit path.

:param msg: A :class:`can.Message` object.

:raise: :class:`can.CanError`

if the message could not be written.

"""

raise NotImplementedError("Trying to write to a readonly bus?")

def __iter__(self):

"""Allow iteration on messages as they are received.

>>> for msg in bus:

... print(msg)

:yields: :class:`can.Message` msg objects.

"""

while True:

m = self.recv(timeout=1.0)

if m is not None:

yield m

logger.debug("done iterating over bus messages")

def flush_tx_buffer(self):

"""Used for CAN backends which need to flush their transmit buffer.

"""

pass

def shutdown(self):

self.flush_tx_buffer()

__metaclass__ = abc.ABCMeta