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.

"""The :mod:`content` module provides methods for creating XML documents, parsing XML, and converting between different XML representations. It uses :mod:`~xml.etree.ElementTree` internally.

"""

from cStringIO import StringIO

from xml.etree import cElementTree as ET

from ncclient import NCClientError

class ContentError(NCClientError):

    "Raised by methods of the :mod:`content` module in case of an error."

    pass

### Namespace-related

#: Base NETCONf namespace

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

#: ... and this is BASE_NS according to Cisco devices tested

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)

# deprecated

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):

        """DictTree -> Element

        :type spec: :obj:`dict` or :obj:`string` or :class:`~xml.etree.ElementTree.Element`

        :rtype: :class:`~xml.etree.ElementTree.Element`

        """

        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('attrib', {}))

            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 not isinstance(subtree, list):

                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'):

        """DictTree -> XML

        :type spec: :obj:`dict` or :obj:`string` or :class:`~xml.etree.ElementTree.Element`

        :arg encoding: chraracter encoding

        :rtype: string

        """

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

class Element:

    @staticmethod

    def DictTree(ele):

        """DictTree -> Element

        :type spec: :class:`~xml.etree.ElementTree.Element`

        :rtype: :obj:`dict`

        """

        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'):

        """Element -> XML

        :type spec: :class:`~xml.etree.ElementTree.Element`

        :arg encoding: character encoding

        :rtype: :obj:`string`

        """

        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):

        """XML -> DictTree

        :type spec: :obj:`string`

        :rtype: :obj:`dict`

        """

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

    @staticmethod

    def Element(xml):

        """XML -> Element

        :type xml: :obj:`string`

        :rtype: :class:`~xml.etree.ElementTree.Element`

        """

        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, nslist=[]):

    """If *nslist* is empty, same as :meth:`xml.etree.ElementTree.Element.find`. If it is not, *tag* is interpreted as an unqualified name and qualified using each item in *nslist* (with a :const:`None` item in *nslit* meaning no qualification is done). The first match is returned.

    :arg nslist: optional list of namespaces

    :type nslit: `string` `list`

    """

    if nslist:

        for qname in multiqualify(tag):

            found = ele.find(qname)

            if found is not None:

                return found

    else:

        return ele.find(tag)

def parse_root(raw):

    """Efficiently parses the root element of an XML document.

    :arg raw: XML document

    :type raw: string

    :returns: a tuple of `(tag, attributes)`, where `tag` is the (qualified) name of the element and `attributes` is a dictionary of its attributes.

    :rtype: `tuple`

    """

    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, tags=None, attrs=None, text=None):

    """Checks if the root element meets the supplied criteria. Returns a :class:`~xml.etree.ElementTree.Element` instance if so, otherwise raises :exc:`ContentError`.

    :arg tags: tag name or a list of allowable tag names

    :arg attrs: list of required attribute names, each item may be a list of allowable alternatives

    :arg text: textual content to match

    :type rep: :obj:`dict` or :obj:`string` or :class:`~xml.etree.ElementTree.Element`

    """

    ele = dtree2ele(rep)

    err = False

    if tags:

        if isinstance(tags, basestring):

            tags = [tags]

        if ele.tag not in tags:

            err = True

    if attrs:

        for req in attrs:

            if isinstance(req, basestring): req = [req]

            for alt in req:

                if alt in ele.attrib:

                    break

            else:

                err = True

    if text and ele.text != text:

        err = True

    if err:

        raise ContentError("Element [%s] does not meet requirements" % ele.tag)

    return ele