root / ncclient / transport / session.py @ 7b02d55b
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# Copyright 2009 Shikhar Bhushan
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from Queue import Queue |
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from threading import Thread, Lock, Event |
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from ncclient import xml_ |
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from ncclient.capabilities import Capabilities |
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from errors import TransportError |
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import logging |
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logger = logging.getLogger('ncclient.transport.session')
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class Session(Thread): |
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"Base class for use by transport protocol implementations."
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def __init__(self, capabilities): |
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Thread.__init__(self)
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self.setDaemon(True) |
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self._listeners = set() # 3.0's weakset would be ideal |
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self._lock = Lock()
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self.setName('session') |
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self._q = Queue()
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self._client_capabilities = capabilities
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self._server_capabilities = None # yet |
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self._id = None # session-id |
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self._connected = False # to be set/cleared by subclass implementation |
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logger.debug('%r created: client_capabilities=%r' %
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(self, self._client_capabilities)) |
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def _dispatch_message(self, raw): |
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try:
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root = xml_.parse_root(raw) |
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except Exception as e: |
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logger.error('error parsing dispatch message: %s' % e)
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return
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with self._lock: |
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listeners = list(self._listeners) |
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for l in listeners: |
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logger.debug('dispatching message to %r' % l)
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l.callback(root, raw) # no try-except; fail loudly if you must!
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def _dispatch_error(self, err): |
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with self._lock: |
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listeners = list(self._listeners) |
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for l in listeners: |
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logger.debug('dispatching error to %r' % l)
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try: # here we can be more considerate with catching exceptions |
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l.errback(err) |
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except Exception as e: |
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logger.warning('error dispatching to %r: %r' % (l, e))
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def _post_connect(self): |
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"Greeting stuff"
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init_event = Event() |
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error = [None] # so that err_cb can bind error[0]. just how it is. |
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# callbacks
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def ok_cb(id, capabilities): |
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self._id = id |
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self._server_capabilities = capabilities
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init_event.set() |
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def err_cb(err): |
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error[0] = err
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init_event.set() |
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listener = HelloHandler(ok_cb, err_cb) |
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self.add_listener(listener)
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self.send(HelloHandler.build(self._client_capabilities)) |
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logger.debug('starting main loop')
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self.start()
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# we expect server's hello message
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init_event.wait() |
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# received hello message or an error happened
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self.remove_listener(listener)
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if error[0]: |
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raise error[0] |
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#if ':base:1.0' not in self.server_capabilities:
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# raise MissingCapabilityError(':base:1.0')
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logger.info('initialized: session-id=%s | server_capabilities=%s' %
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(self._id, self._server_capabilities)) |
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def add_listener(self, listener): |
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"""Register a listener that will be notified of incoming messages and
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errors.
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:type listener: :class:`SessionListener`
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"""
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logger.debug('installing listener %r' % listener)
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if not isinstance(listener, SessionListener): |
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raise SessionError("Listener must be a SessionListener type") |
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with self._lock: |
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self._listeners.add(listener)
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def remove_listener(self, listener): |
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"""Unregister some listener; ignore if the listener was never
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registered.
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:type listener: :class:`SessionListener`
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"""
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logger.debug('discarding listener %r' % listener)
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with self._lock: |
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self._listeners.discard(listener)
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def get_listener_instance(self, cls): |
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"""If a listener of the specified type is registered, returns the
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instance.
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:type cls: :class:`SessionListener`
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"""
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with self._lock: |
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for listener in self._listeners: |
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if isinstance(listener, cls): |
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return listener
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def connect(self, *args, **kwds): # subclass implements |
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raise NotImplementedError |
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def run(self): # subclass implements |
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raise NotImplementedError |
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def send(self, message): |
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"""Send the supplied *message* to NETCONF server.
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:arg message: an XML document
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:type message: `string`
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"""
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if not self.connected: |
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raise TransportError('Not connected to NETCONF server') |
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logger.debug('queueing %s' % message)
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self._q.put(message)
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### Properties
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@property
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def connected(self): |
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"Connection status of the session."
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return self._connected |
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@property
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def client_capabilities(self): |
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"Client's :class:`Capabilities`"
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return self._client_capabilities |
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@property
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def server_capabilities(self): |
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"Server's :class:`Capabilities`"
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return self._server_capabilities |
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@property
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def id(self): |
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"""A `string` representing the `session-id`. If the session has not
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been initialized it will be :const:`None`"""
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return self._id |
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class SessionListener(object): |
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"""Base class for :class:`Session` listeners, which are notified when a new
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NETCONF message is received or an error occurs.
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.. note::
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Avoid time-intensive tasks in a callback's context.
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"""
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def callback(self, root, raw): |
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"""Called when a new XML document is received. The `root` argument
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allows the callback to determine whether it wants to further process the
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document.
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:arg root: tuple of `(tag, attributes)` where `tag` is the qualified name of the root element and `attributes` is a dictionary of its attributes (also qualified names)
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:type root: `tuple`
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:arg raw: XML document
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:type raw: `string`
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"""
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raise NotImplementedError |
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def errback(self, ex): |
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"""Called when an error occurs.
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:type ex: :exc:`Exception`
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"""
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raise NotImplementedError |
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class HelloHandler(SessionListener): |
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def __init__(self, init_cb, error_cb): |
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self._init_cb = init_cb
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self._error_cb = error_cb
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def callback(self, root, raw): |
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if xml_.unqualify(root[0]) == 'hello': |
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try:
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id, capabilities = HelloHandler.parse(raw)
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except Exception as e: |
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self._error_cb(e)
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else:
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self._init_cb(id, capabilities) |
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def errback(self, err): |
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self._error_cb(err)
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@staticmethod
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def build(capabilities): |
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"Given a list of capability URI's returns <hello> message XML string"
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spec = { |
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'tag': 'hello', |
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'attrib': {'xmlns': xml_.BASE_NS_1_0}, |
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'subtree': [{
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'tag': 'capabilities', |
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'subtree': # this is fun :-) |
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[{'tag': 'capability', 'text': uri} for uri in capabilities] |
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}] |
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} |
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return xml_.dtree2xml(spec)
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@staticmethod
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def parse(raw): |
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"Returns tuple of (session-id (str), capabilities (Capabilities)"
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sid, capabilities = 0, []
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root = xml_.xml2ele(raw) |
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for child in root.getchildren(): |
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tag = xml_.unqualify(child.tag) |
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if tag == 'session-id': |
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sid = child.text |
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elif tag == 'capabilities': |
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for cap in child.getchildren(): |
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if xml_.unqualify(cap.tag) == 'capability': |
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capabilities.append(cap.text) |
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return sid, Capabilities(capabilities)
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