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 xml.etree import cElementTree as ET

iselement = ET.iselement

element2string = ET.tostring

### 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: '{%s}%s' % (ns, tag)

# i would have written a def if lambdas weren't so much fun

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

                                                        for ns in nslist]

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

def namespaced_find(ele, tag, workaround=True):

    """`workaround` is for Cisco implementations (at least the one tested), 

    which uses an incorrect namespace.

    """

    found = None

    if not workaround:

        found = ele.find(tag)

    else:

        for qname in multiqualify(tag):

            found = ele.find(qname)

            if found is not None:

                break

    return found

### Build XML using Python data structures ###

class XMLConverter:

    """Build an ElementTree.Element instance from an XML tree specification

    based on nested dictionaries. TODO: describe spec

    """

    def __init__(self, spec):

        "TODO: docstring"

        self._root = XMLConverter.build(spec)

    def to_string(self, encoding='utf-8'):

        "TODO: docstring"

        xml = ET.tostring(self._root, encoding)

        # some etree versions don't include xml decl with utf-8

        # this is a problem with some devices

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

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

    @property

    def tree(self):

        "TODO: docstring"

        return self._root

    @staticmethod

    def build(spec):

        "TODO: docstring"

        if iselement(spec):

            return spec

        elif isinstance(spec, basestring):

            return ET.XML(spec)

        ## assume isinstance(spec, dict)

        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(XMLConverter.build(subele))

            return ele

        elif 'comment' in spec:

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

        else:

            raise ContentError('Invalid tree spec')

    @staticmethod

    def from_string(xml):

        return XMLConverter.parse(ET.fromstring(xml))

    @staticmethod

    def parse(root):

        return {

            'tag': root.tag,

            'attributes': root.attrib,

            'text': root.text,

            'tail': root.tail,

            'subtree': [ XMLConverter.parse(child) for child in root.getchildren() ]

        }