ncclient:NETCONF Python client

# Copyright 2009 Shikhar Bhushan

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

#    http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

"TODO: docstring"

from cStringIO import StringIO

from threading import Thread

from Queue import Queue

from threading import Lock

from xml.etree import cElementTree as ET

import logging

logger = logging.getLogger('ncclient.glue')

def parse_root(raw):

    '''Parse the top-level element from a string representing an XML document.

    Returns a `(tag, attributes)` tuple, where `tag` is a string representing

    the qualified name of the root element and `attributes` is an

    `{attribute: value}` dictionary.

    '''

    fp = StringIO(raw)

    for event, element in ET.iterparse(fp, events=('start',)):

        return (element.tag, element.attrib)

class Subject(Thread):

    'Meant for subclassing by transport.Session'

    def __init__(self):

        "TODO: docstring"

        Thread.__init__(self)

        self._q = Queue()

        self._listeners = set() # TODO(?) weakref

        self._lock = Lock()

    def _dispatch_message(self, raw):

        "TODO: docstring"

        root = parse_root(raw)

        with self._lock:

            listeners = list(self._listeners)

        for l in listeners:

            logger.debug('dispatching message to %r' % l)

            try:

                l.callback(root, raw)

            except Exception as e:

                logger.warning('[error] %r' % e)

    def _dispatch_error(self, err):

        "TODO: docstring"

        with self._lock:

            listeners = list(self._listeners)

        for l in listeners:

            logger.debug('dispatching error to %r' % l)

            try:

                l.errback(err)

            except Exception as e:

                logger.warning('error %r' % e)

    def add_listener(self, listener):

        "TODO: docstring"

        logger.debug('installing listener %r' % listener)

        with self._lock:

            self._listeners.add(listener)

    def remove_listener(self, listener):

        "TODO: docstring"

        logger.debug('discarding listener %r' % listener)

        with self._lock:

            self._listeners.discard(listener)

    def get_listener_instance(self, cls):

        '''This is useful when we want to maintain one listener of a particular

        type per subject i.e. a multiton.

        '''

        with self._lock:

            for listener in self._listeners:

                if isinstance(listener, cls):

                    return listener

    def send(self, message):

        "TODO: docstring"

        logger.debug('queueing %s' % message)

        self._q.put(message)

class Listener(object):

    "TODO: docstring"

    def callback(self, root, raw):

        raise NotImplementedError

    def errback(self, err):

        raise NotImplementedError