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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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"""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.
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"""
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from cStringIO import StringIO
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from xml.etree import cElementTree as ET
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from ncclient import NCClientError
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class ContentError(NCClientError):
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    "Raised by methods of the :mod:`content` module in case of an error."
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    pass
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### Namespace-related
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#: Base NETCONf namespace
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BASE_NS = 'urn:ietf:params:xml:ns:netconf:base:1.0'
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#: ... and this is BASE_NS according to Cisco devices tested
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CISCO_BS = 'urn:ietf:params:netconf:base:1.0'
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try:
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    register_namespace = ET.register_namespace
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except AttributeError:
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    def register_namespace(prefix, uri):
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        from xml.etree import ElementTree
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        # cElementTree uses ElementTree's _namespace_map, so that's ok
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        ElementTree._namespace_map[uri] = prefix
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# we'd like BASE_NS to be prefixed as "netconf"
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register_namespace('netconf', BASE_NS)
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qualify = lambda tag, ns=BASE_NS: tag if ns is None else '{%s}%s' % (ns, tag)
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# deprecated
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multiqualify = lambda tag, nslist=(BASE_NS, CISCO_BS): [qualify(tag, ns) for ns in nslist]
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unqualify = lambda tag: tag[tag.rfind('}')+1:]
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### XML with Python data structures
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class DictTree:
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    @staticmethod
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    def Element(spec):
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        """DictTree -> Element
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        :type spec: :obj:`dict` or :obj:`string` or :class:`~xml.etree.ElementTree.Element`
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        :rtype: :class:`~xml.etree.ElementTree.Element`
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        """
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        if iselement(spec):
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            return spec
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        elif isinstance(spec, basestring):
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            return XML.Element(spec)
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        if not isinstance(spec, dict):
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            raise ContentError("Invalid tree spec")
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        if 'tag' in spec:
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            ele = ET.Element(spec.get('tag'), spec.get('attrib', {}))
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            ele.text = spec.get('text', '')
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            ele.tail = spec.get('tail', '')
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            subtree = spec.get('subtree', [])
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            # might not be properly specified as list but may be dict
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            if isinstance(subtree, dict):
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                subtree = [subtree]
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            for subele in subtree:
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                ele.append(DictTree.Element(subele))
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            return ele
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        elif 'comment' in spec:
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            return ET.Comment(spec.get('comment'))
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        else:
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            raise ContentError('Invalid tree spec')
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    @staticmethod
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    def XML(spec, encoding='UTF-8'):
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        """DictTree -> XML
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        :type spec: :obj:`dict` or :obj:`string` or :class:`~xml.etree.ElementTree.Element`
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        :arg encoding: chraracter encoding
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        :rtype: string
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        """
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        return Element.XML(DictTree.Element(spec), encoding)
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class Element:
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    @staticmethod
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    def DictTree(ele):
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        """DictTree -> Element
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        :type spec: :class:`~xml.etree.ElementTree.Element`
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        :rtype: :obj:`dict`
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        """
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        return {
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            'tag': ele.tag,
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            'attributes': ele.attrib,
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            'text': ele.text,
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            'tail': ele.tail,
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            'subtree': [ Element.DictTree(child) for child in root.getchildren() ]
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        }
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    @staticmethod
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    def XML(ele, encoding='UTF-8'):
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        """Element -> XML
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        :type spec: :class:`~xml.etree.ElementTree.Element`
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        :arg encoding: character encoding
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        :rtype: :obj:`string`
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        """
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        xml = ET.tostring(ele, encoding)
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        if xml.startswith('<?xml'):
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            return xml
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        else:
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            return '<?xml version="1.0" encoding="%s"?>%s' % (encoding, xml)
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class XML:
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    @staticmethod
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    def DictTree(xml):
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        """XML -> DictTree
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        :type spec: :obj:`string`
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        :rtype: :obj:`dict`
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        """
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        return Element.DictTree(XML.Element(xml))
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    @staticmethod
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    def Element(xml):
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        """XML -> Element
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        :type xml: :obj:`string`
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        :rtype: :class:`~xml.etree.ElementTree.Element`
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        """
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        return ET.fromstring(xml)
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dtree2ele = DictTree.Element
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dtree2xml = DictTree.XML
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ele2dtree = Element.DictTree
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ele2xml = Element.XML
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xml2dtree = XML.DictTree
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xml2ele = XML.Element
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### Other utility functions
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iselement = ET.iselement
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def find(ele, tag, nslist=[]):
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    """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.
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    :arg nslist: optional list of namespaces
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    :type nslit: `string` `list`
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    """
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    if nslist:
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        for qname in multiqualify(tag):
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            found = ele.find(qname)
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            if found is not None:
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                return found
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    else:
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        return ele.find(tag)
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def parse_root(raw):
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    """Efficiently parses the root element of an XML document.
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    :arg raw: XML document
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    :type raw: string
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    :returns: a tuple of `(tag, attributes)`, where `tag` is the (qualified) name of the element and `attributes` is a dictionary of its attributes.
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    :rtype: `tuple`
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    """
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    fp = StringIO(raw[:1024]) # this is a guess but start element beyond 1024 bytes would be a bit absurd
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    for event, element in ET.iterparse(fp, events=('start',)):
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        return (element.tag, element.attrib)
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def validated_element(rep, tag=None, attrs=None, text=None):
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    """Checks if the root element meets the supplied criteria. Returns a :class:`~xml.etree.ElementTree.Element` instance if so, otherwise raises :exc:`ContentError`.
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    :arg tag: tag name or a list of allowable tag names
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    :arg attrs: list of required attribute names, each item may be a list of allowable alternatives
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    :arg text: textual content to match
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    :type rep: :obj:`dict` or :obj:`string` or :class:`~xml.etree.ElementTree.Element`
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    """
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    ele = dtree2ele(rep)
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    err = False
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    if tag:
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        if isinstance(tag, basestring): tag = [tag]
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        if ele.tag not in tags:
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            err = True
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    if attrs:
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        for req in attrs:
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            if isinstance(req, basestring): req = [req]
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            for alt in req:
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                if alt in ele.attrib:
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                    break
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            else:
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                err = True
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    if text and ele.text != text:
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        err = True
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    if err:
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        raise ContentError("Element [%s] does not meet requirements" % ele.tag)
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    return ele