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.

from cStringIO import StringIO

from xml.etree import cElementTree as ET

from ncclient import NCClientError

class ContentError(NCClientError):

    pass

### Namespace-related

BASE_NS = 'urn:ietf:params:xml:ns:netconf:base:1.0'

# and this is BASE_NS according to cisco devices...

CISCO_BS = 'urn:ietf:params:netconf:base:1.0'

try:

    register_namespace = ET.register_namespace

except AttributeError:

    def register_namespace(prefix, uri):

        from xml.etree import ElementTree

        # cElementTree uses ElementTree's _namespace_map, so that's ok

        ElementTree._namespace_map[uri] = prefix

# we'd like BASE_NS to be prefixed as "netconf"

register_namespace('netconf', BASE_NS)

qualify = lambda tag, ns=BASE_NS: tag if ns is None else '{%s}%s' % (ns, tag)

multiqualify = lambda tag, nslist=(BASE_NS, CISCO_BS): [qualify(tag, ns) for ns in nslist]

unqualify = lambda tag: tag[tag.rfind('}')+1:]

### XML with Python data structures

class DictTree:

    @staticmethod

    def Element(spec):

        if iselement(spec):

            return spec

        elif isinstance(spec, basestring):

            return XML.Element(spec)

        if not isinstance(spec, dict):

            raise ContentError("Invalid tree spec")

        if 'tag' in spec:

            ele = ET.Element(spec.get('tag'), spec.get('attributes', {}))

            ele.text = spec.get('text', '')

            ele.tail = spec.get('tail', '')

            subtree = spec.get('subtree', [])

            # might not be properly specified as list but may be dict

            if isinstance(subtree, dict):

                subtree = [subtree]

            for subele in subtree:

                ele.append(DictTree.Element(subele))

            return ele

        elif 'comment' in spec:

            return ET.Comment(spec.get('comment'))

        else:

            raise ContentError('Invalid tree spec')

    @staticmethod

    def XML(spec, encoding='utf-8'):

        return Element.XML(DictTree.Element(spec), encoding)

class Element:

    @staticmethod

    def DictTree(ele):

        return {

            'tag': ele.tag,

            'attributes': ele.attrib,

            'text': ele.text,

            'tail': ele.tail,

            'subtree': [ Element.DictTree(child) for child in root.getchildren() ]

        }

    @staticmethod

    def XML(ele, encoding='utf-8'):

        xml = ET.tostring(ele, encoding)

        if xml.startswith('<?xml'):

            return xml

        else:

            return '<?xml version="1.0" encoding="%s"?>%s' % (encoding, xml)

class XML:

    @staticmethod

    def DictTree(xml):

        return Element.DictTree(XML.Element(xml))

    @staticmethod

    def Element(xml):

        return ET.fromstring(xml)

dtree2ele = DictTree.Element

dtree2xml = DictTree.XML

ele2dtree = Element.DictTree

ele2xml = Element.XML

xml2dtree = XML.DictTree

xml2ele = XML.Element

### Other utility functions

iselement = ET.iselement

def find(ele, tag, strict=False):

    """In strict mode, doesn't workaround Cisco implementations sending incorrectly

    namespaced XML. Supply qualified tag name if using strict mode.

    """

    if strict:

        return ele.find(tag)

    else:

        for qname in multiqualify(tag):

            found = ele.find(qname)

            if found is not None:

                return found

def parse_root(raw):

    '''Parse the top-level element from XML string.

    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[:1024]) # this is a guess but start element beyond 1024 bytes would be a bit absurd

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

        return (element.tag, element.attrib)

def validated_element(rep, tag, attrs=None):

    ele = dtree2ele(rep)

    if ele.tag not in (tag, qualify(tag)):

        raise ContentError("Required root element [%s] not found" % tag)

    if attrs is not None:

        for req in attrs:

            for attr in ele.attrib:

                if unqualify(attr) == req:

                    break

            else:

                raise ContentError("Required attribute [%s] not found in element [%s]" % (req, req_tag))

    return ele