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

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: '{%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:]

### XML with Python data structures

def to_element(spec):

    "TODO: docstring"

    if iselement(spec):

        return spec

    elif isinstance(spec, basestring):

        return ET.XML(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(XMLConverter.build(subele))

        return ele

    elif 'comment' in spec:

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

    else:

        raise ContentError('Invalid tree spec')

def from_xml(xml):

    return ET.fromstring(xml)

def to_xml(repr, encoding='utf-8'):

    "TODO: docstring"

    xml = ET.tostring(to_element(repr), 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))

## Utility functions

iselement = ET.iselement

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

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

    namespaced XML. Supply qualified name if using strict mode.

    """

    found = None

    if strict:

        found = ele.find(tag)

    else:

        for qname in multiqualify(tag):

            found = ele.find(qname)

            if found is not None:

                break

    return found

def parse_root(raw):

    '''Internal use.

    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 root_ensured(rep, req_tag, req_attrs=None):

    rep = to_element(rep)

    if rep.tag not in (req_tag, qualify(req_tag)):

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

    if req_attrs is not None:

        pass # TODO

    return rep