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|
# vim: tabstop=4 shiftwidth=4 softtabstop=4
# Copyright 2011 OpenStack Foundation
# All Rights Reserved.
#
# 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.
import os.path
from lxml import etree
from xml.dom import minidom
from xml.parsers import expat
from xml import sax
from xml.sax import expatreader
from nova import exception
from nova import utils
XMLNS_V10 = 'http://docs.rackspacecloud.com/servers/api/v1.0'
XMLNS_V11 = 'http://docs.openstack.org/compute/api/v1.1'
XMLNS_COMMON_V10 = 'http://docs.openstack.org/common/api/v1.0'
XMLNS_ATOM = 'http://www.w3.org/2005/Atom'
def validate_schema(xml, schema_name):
if isinstance(xml, str):
xml = etree.fromstring(xml)
base_path = 'nova/api/openstack/compute/schemas/v1.1/'
if schema_name in ('atom', 'atom-link'):
base_path = 'nova/api/openstack/compute/schemas/'
schema_path = os.path.join(utils.novadir(),
'%s%s.rng' % (base_path, schema_name))
schema_doc = etree.parse(schema_path)
relaxng = etree.RelaxNG(schema_doc)
relaxng.assertValid(xml)
class Selector(object):
"""Selects datum to operate on from an object."""
def __init__(self, *chain):
"""Initialize the selector.
Each argument is a subsequent index into the object.
"""
self.chain = chain
def __repr__(self):
"""Return a representation of the selector."""
return "Selector" + repr(self.chain)
def __call__(self, obj, do_raise=False):
"""Select a datum to operate on.
Selects the relevant datum within the object.
:param obj: The object from which to select the object.
:param do_raise: If False (the default), return None if the
indexed datum does not exist. Otherwise,
raise a KeyError.
"""
# Walk the selector list
for elem in self.chain:
# If it's callable, call it
if callable(elem):
obj = elem(obj)
else:
# Use indexing
try:
obj = obj[elem]
except (KeyError, IndexError):
# No sense going any further
if do_raise:
# Convert to a KeyError, for consistency
raise KeyError(elem)
return None
# Return the finally-selected object
return obj
def get_items(obj):
"""Get items in obj."""
return list(obj.items())
class EmptyStringSelector(Selector):
"""Returns the empty string if Selector would return None."""
def __call__(self, obj, do_raise=False):
"""Returns empty string if the selected value does not exist."""
try:
return super(EmptyStringSelector, self).__call__(obj, True)
except KeyError:
return ""
class ConstantSelector(object):
"""Returns a constant."""
def __init__(self, value):
"""Initialize the selector.
:param value: The value to return.
"""
self.value = value
def __repr__(self):
"""Return a representation of the selector."""
return repr(self.value)
def __call__(self, _obj, _do_raise=False):
"""Select a datum to operate on.
Returns a constant value. Compatible with
Selector.__call__().
"""
return self.value
class TemplateElement(object):
"""Represent an element in the template."""
def __init__(self, tag, attrib=None, selector=None, subselector=None,
**extra):
"""Initialize an element.
Initializes an element in the template. Keyword arguments
specify attributes to be set on the element; values must be
callables. See TemplateElement.set() for more information.
:param tag: The name of the tag to create.
:param attrib: An optional dictionary of element attributes.
:param selector: An optional callable taking an object and
optional boolean do_raise indicator and
returning the object bound to the element.
:param subselector: An optional callable taking an object and
optional boolean do_raise indicator and
returning the object bound to the element.
This is used to further refine the datum
object returned by selector in the event
that it is a list of objects.
"""
# Convert selector into a Selector
if selector is None:
selector = Selector()
elif not callable(selector):
selector = Selector(selector)
# Convert subselector into a Selector
if subselector is not None and not callable(subselector):
subselector = Selector(subselector)
self.tag = tag
self.selector = selector
self.subselector = subselector
self.attrib = {}
self._text = None
self._children = []
self._childmap = {}
# Run the incoming attributes through set() so that they
# become selectorized
if not attrib:
attrib = {}
attrib.update(extra)
for k, v in attrib.items():
self.set(k, v)
def __repr__(self):
"""Return a representation of the template element."""
return ('<%s.%s %r at %#x>' %
(self.__class__.__module__, self.__class__.__name__,
self.tag, id(self)))
def __len__(self):
"""Return the number of child elements."""
return len(self._children)
def __contains__(self, key):
"""Determine whether a child node named by key exists."""
return key in self._childmap
def __getitem__(self, idx):
"""Retrieve a child node by index or name."""
if isinstance(idx, basestring):
# Allow access by node name
return self._childmap[idx]
else:
return self._children[idx]
def append(self, elem):
"""Append a child to the element."""
# Unwrap templates...
elem = elem.unwrap()
# Avoid duplications
if elem.tag in self._childmap:
raise KeyError(elem.tag)
self._children.append(elem)
self._childmap[elem.tag] = elem
def extend(self, elems):
"""Append children to the element."""
# Pre-evaluate the elements
elemmap = {}
elemlist = []
for elem in elems:
# Unwrap templates...
elem = elem.unwrap()
# Avoid duplications
if elem.tag in self._childmap or elem.tag in elemmap:
raise KeyError(elem.tag)
elemmap[elem.tag] = elem
elemlist.append(elem)
# Update the children
self._children.extend(elemlist)
self._childmap.update(elemmap)
def insert(self, idx, elem):
"""Insert a child element at the given index."""
# Unwrap templates...
elem = elem.unwrap()
# Avoid duplications
if elem.tag in self._childmap:
raise KeyError(elem.tag)
self._children.insert(idx, elem)
self._childmap[elem.tag] = elem
def remove(self, elem):
"""Remove a child element."""
# Unwrap templates...
elem = elem.unwrap()
# Check if element exists
if elem.tag not in self._childmap or self._childmap[elem.tag] != elem:
raise ValueError(_('element is not a child'))
self._children.remove(elem)
del self._childmap[elem.tag]
def get(self, key):
"""Get an attribute.
Returns a callable which performs datum selection.
:param key: The name of the attribute to get.
"""
return self.attrib[key]
def set(self, key, value=None):
"""Set an attribute.
:param key: The name of the attribute to set.
:param value: A callable taking an object and optional boolean
do_raise indicator and returning the datum bound
to the attribute. If None, a Selector() will be
constructed from the key. If a string, a
Selector() will be constructed from the string.
"""
# Convert value to a selector
if value is None:
value = Selector(key)
elif not callable(value):
value = Selector(value)
self.attrib[key] = value
def keys(self):
"""Return the attribute names."""
return self.attrib.keys()
def items(self):
"""Return the attribute names and values."""
return self.attrib.items()
def unwrap(self):
"""Unwraps a template to return a template element."""
# We are a template element
return self
def wrap(self):
"""Wraps a template element to return a template."""
# Wrap in a basic Template
return Template(self)
def apply(self, elem, obj):
"""Apply text and attributes to an etree.Element.
Applies the text and attribute instructions in the template
element to an etree.Element instance.
:param elem: An etree.Element instance.
:param obj: The base object associated with this template
element.
"""
# Start with the text...
if self.text is not None:
elem.text = unicode(self.text(obj))
# Now set up all the attributes...
for key, value in self.attrib.items():
try:
elem.set(key, unicode(value(obj, True)))
except KeyError:
# Attribute has no value, so don't include it
pass
def _render(self, parent, datum, patches, nsmap):
"""Internal rendering.
Renders the template node into an etree.Element object.
Returns the etree.Element object.
:param parent: The parent etree.Element instance.
:param datum: The datum associated with this template element.
:param patches: A list of other template elements that must
also be applied.
:param nsmap: An optional namespace dictionary to be
associated with the etree.Element instance.
"""
# Allocate a node
if callable(self.tag):
tagname = self.tag(datum)
else:
tagname = self.tag
elem = etree.Element(tagname, nsmap=nsmap)
# If we have a parent, append the node to the parent
if parent is not None:
parent.append(elem)
# If the datum is None, do nothing else
if datum is None:
return elem
# Apply this template element to the element
self.apply(elem, datum)
# Additionally, apply the patches
for patch in patches:
patch.apply(elem, datum)
# We have fully rendered the element; return it
return elem
def render(self, parent, obj, patches=[], nsmap=None):
"""Render an object.
Renders an object against this template node. Returns a list
of two-item tuples, where the first item is an etree.Element
instance and the second item is the datum associated with that
instance.
:param parent: The parent for the etree.Element instances.
:param obj: The object to render this template element
against.
:param patches: A list of other template elements to apply
when rendering this template element.
:param nsmap: An optional namespace dictionary to attach to
the etree.Element instances.
"""
# First, get the datum we're rendering
data = None if obj is None else self.selector(obj)
# Check if we should render at all
if not self.will_render(data):
return []
elif data is None:
return [(self._render(parent, None, patches, nsmap), None)]
# Make the data into a list if it isn't already
if not isinstance(data, list):
data = [data]
elif parent is None:
raise ValueError(_('root element selecting a list'))
# Render all the elements
elems = []
for datum in data:
if self.subselector is not None:
datum = self.subselector(datum)
elems.append((self._render(parent, datum, patches, nsmap), datum))
# Return all the elements rendered, as well as the
# corresponding datum for the next step down the tree
return elems
def will_render(self, datum):
"""Hook method.
An overridable hook method to determine whether this template
element will be rendered at all. By default, returns False
(inhibiting rendering) if the datum is None.
:param datum: The datum associated with this template element.
"""
# Don't render if datum is None
return datum is not None
def _text_get(self):
"""Template element text.
Either None or a callable taking an object and optional
boolean do_raise indicator and returning the datum bound to
the text of the template element.
"""
return self._text
def _text_set(self, value):
# Convert value to a selector
if value is not None and not callable(value):
value = Selector(value)
self._text = value
def _text_del(self):
self._text = None
text = property(_text_get, _text_set, _text_del)
def tree(self):
"""Return string representation of the template tree.
Returns a representation of the template rooted at this
element as a string, suitable for inclusion in debug logs.
"""
# Build the inner contents of the tag...
contents = [self.tag, '!selector=%r' % self.selector]
# Add the text...
if self.text is not None:
contents.append('!text=%r' % self.text)
# Add all the other attributes
for key, value in self.attrib.items():
contents.append('%s=%r' % (key, value))
# If there are no children, return it as a closed tag
if len(self) == 0:
return '<%s/>' % ' '.join([str(i) for i in contents])
# OK, recurse to our children
children = [c.tree() for c in self]
# Return the result
return ('<%s>%s</%s>' %
(' '.join(contents), ''.join(children), self.tag))
def SubTemplateElement(parent, tag, attrib=None, selector=None,
subselector=None, **extra):
"""Create a template element as a child of another.
Corresponds to the etree.SubElement interface. Parameters are as
for TemplateElement, with the addition of the parent.
"""
# Convert attributes
attrib = attrib or {}
attrib.update(extra)
# Get a TemplateElement
elem = TemplateElement(tag, attrib=attrib, selector=selector,
subselector=subselector)
# Append the parent safely
if parent is not None:
parent.append(elem)
return elem
class Template(object):
"""Represent a template."""
def __init__(self, root, nsmap=None):
"""Initialize a template.
:param root: The root element of the template.
:param nsmap: An optional namespace dictionary to be
associated with the root element of the
template.
"""
self.root = root.unwrap() if root is not None else None
self.nsmap = nsmap or {}
self.serialize_options = dict(encoding='UTF-8', xml_declaration=True)
def _serialize(self, parent, obj, siblings, nsmap=None):
"""Internal serialization.
Recursive routine to build a tree of etree.Element instances
from an object based on the template. Returns the first
etree.Element instance rendered, or None.
:param parent: The parent etree.Element instance. Can be
None.
:param obj: The object to render.
:param siblings: The TemplateElement instances against which
to render the object.
:param nsmap: An optional namespace dictionary to be
associated with the etree.Element instance
rendered.
"""
# First step, render the element
elems = siblings[0].render(parent, obj, siblings[1:], nsmap)
# Now, recurse to all child elements
seen = set()
for idx, sibling in enumerate(siblings):
for child in sibling:
# Have we handled this child already?
if child.tag in seen:
continue
seen.add(child.tag)
# Determine the child's siblings
nieces = [child]
for sib in siblings[idx + 1:]:
if child.tag in sib:
nieces.append(sib[child.tag])
# Now we recurse for every data element
for elem, datum in elems:
self._serialize(elem, datum, nieces)
# Return the first element; at the top level, this will be the
# root element
if elems:
return elems[0][0]
def serialize(self, obj, *args, **kwargs):
"""Serialize an object.
Serializes an object against the template. Returns a string
with the serialized XML. Positional and keyword arguments are
passed to etree.tostring().
:param obj: The object to serialize.
"""
elem = self.make_tree(obj)
if elem is None:
return ''
for k, v in self.serialize_options.items():
kwargs.setdefault(k, v)
# Serialize it into XML
return etree.tostring(elem, *args, **kwargs)
def make_tree(self, obj):
"""Create a tree.
Serializes an object against the template. Returns an Element
node with appropriate children.
:param obj: The object to serialize.
"""
# If the template is empty, return the empty string
if self.root is None:
return None
# Get the siblings and nsmap of the root element
siblings = self._siblings()
nsmap = self._nsmap()
# Form the element tree
return self._serialize(None, obj, siblings, nsmap)
def _siblings(self):
"""Hook method for computing root siblings.
An overridable hook method to return the siblings of the root
element. By default, this is the root element itself.
"""
return [self.root]
def _nsmap(self):
"""Hook method for computing the namespace dictionary.
An overridable hook method to return the namespace dictionary.
"""
return self.nsmap.copy()
def unwrap(self):
"""Unwraps a template to return a template element."""
# Return the root element
return self.root
def wrap(self):
"""Wraps a template element to return a template."""
# We are a template
return self
def apply(self, master):
"""Hook method for determining slave applicability.
An overridable hook method used to determine if this template
is applicable as a slave to a given master template.
:param master: The master template to test.
"""
return True
def tree(self):
"""Return string representation of the template tree.
Returns a representation of the template as a string, suitable
for inclusion in debug logs.
"""
return "%r: %s" % (self, self.root.tree())
class MasterTemplate(Template):
"""Represent a master template.
Master templates are versioned derivatives of templates that
additionally allow slave templates to be attached. Slave
templates allow modification of the serialized result without
directly changing the master.
"""
def __init__(self, root, version, nsmap=None):
"""Initialize a master template.
:param root: The root element of the template.
:param version: The version number of the template.
:param nsmap: An optional namespace dictionary to be
associated with the root element of the
template.
"""
super(MasterTemplate, self).__init__(root, nsmap)
self.version = version
self.slaves = []
def __repr__(self):
"""Return string representation of the template."""
return ("<%s.%s object version %s at %#x>" %
(self.__class__.__module__, self.__class__.__name__,
self.version, id(self)))
def _siblings(self):
"""Hook method for computing root siblings.
An overridable hook method to return the siblings of the root
element. This is the root element plus the root elements of
all the slave templates.
"""
return [self.root] + [slave.root for slave in self.slaves]
def _nsmap(self):
"""Hook method for computing the namespace dictionary.
An overridable hook method to return the namespace dictionary.
The namespace dictionary is computed by taking the master
template's namespace dictionary and updating it from all the
slave templates.
"""
nsmap = self.nsmap.copy()
for slave in self.slaves:
nsmap.update(slave._nsmap())
return nsmap
def attach(self, *slaves):
"""Attach one or more slave templates.
Attaches one or more slave templates to the master template.
Slave templates must have a root element with the same tag as
the master template. The slave template's apply() method will
be called to determine if the slave should be applied to this
master; if it returns False, that slave will be skipped.
(This allows filtering of slaves based on the version of the
master template.)
"""
slave_list = []
for slave in slaves:
slave = slave.wrap()
# Make sure we have a tree match
if slave.root.tag != self.root.tag:
msg = _("Template tree mismatch; adding slave %(slavetag)s to "
"master %(mastertag)s") % {'slavetag': slave.root.tag,
'mastertag': self.root.tag}
raise ValueError(msg)
# Make sure slave applies to this template
if not slave.apply(self):
continue
slave_list.append(slave)
# Add the slaves
self.slaves.extend(slave_list)
def copy(self):
"""Return a copy of this master template."""
# Return a copy of the MasterTemplate
tmp = self.__class__(self.root, self.version, self.nsmap)
tmp.slaves = self.slaves[:]
return tmp
class SlaveTemplate(Template):
"""Represent a slave template.
Slave templates are versioned derivatives of templates. Each
slave has a minimum version and optional maximum version of the
master template to which they can be attached.
"""
def __init__(self, root, min_vers, max_vers=None, nsmap=None):
"""Initialize a slave template.
:param root: The root element of the template.
:param min_vers: The minimum permissible version of the master
template for this slave template to apply.
:param max_vers: An optional upper bound for the master
template version.
:param nsmap: An optional namespace dictionary to be
associated with the root element of the
template.
"""
super(SlaveTemplate, self).__init__(root, nsmap)
self.min_vers = min_vers
self.max_vers = max_vers
def __repr__(self):
"""Return string representation of the template."""
return ("<%s.%s object versions %s-%s at %#x>" %
(self.__class__.__module__, self.__class__.__name__,
self.min_vers, self.max_vers, id(self)))
def apply(self, master):
"""Hook method for determining slave applicability.
An overridable hook method used to determine if this template
is applicable as a slave to a given master template. This
version requires the master template to have a version number
between min_vers and max_vers.
:param master: The master template to test.
"""
# Does the master meet our minimum version requirement?
if master.version < self.min_vers:
return False
# How about our maximum version requirement?
if self.max_vers is not None and master.version > self.max_vers:
return False
return True
class TemplateBuilder(object):
"""Template builder.
This class exists to allow templates to be lazily built without
having to build them each time they are needed. It must be
subclassed, and the subclass must implement the construct()
method, which must return a Template (or subclass) instance. The
constructor will always return the template returned by
construct(), or, if it has a copy() method, a copy of that
template.
"""
_tmpl = None
def __new__(cls, copy=True):
"""Construct and return a template.
:param copy: If True (the default), a copy of the template
will be constructed and returned, if possible.
"""
# Do we need to construct the template?
if cls._tmpl is None:
tmp = super(TemplateBuilder, cls).__new__(cls)
# Construct the template
cls._tmpl = tmp.construct()
# If the template has a copy attribute, return the result of
# calling it
if copy and hasattr(cls._tmpl, 'copy'):
return cls._tmpl.copy()
# Return the template
return cls._tmpl
def construct(self):
"""Construct a template.
Called to construct a template instance, which it must return.
Only called once.
"""
raise NotImplementedError(_("subclasses must implement construct()!"))
def make_links(parent, selector=None):
"""
Attach an Atom <links> element to the parent.
"""
elem = SubTemplateElement(parent, '{%s}link' % XMLNS_ATOM,
selector=selector)
elem.set('rel')
elem.set('type')
elem.set('href')
# Just for completeness...
return elem
def make_flat_dict(name, selector=None, subselector=None, ns=None):
"""
Utility for simple XML templates that traditionally used
XMLDictSerializer with no metadata. Returns a template element
where the top-level element has the given tag name, and where
sub-elements have tag names derived from the object's keys and
text derived from the object's values. This only works for flat
dictionary objects, not dictionaries containing nested lists or
dictionaries.
"""
# Set up the names we need...
if ns is None:
elemname = name
tagname = Selector(0)
else:
elemname = '{%s}%s' % (ns, name)
tagname = lambda obj, do_raise=False: '{%s}%s' % (ns, obj[0])
if selector is None:
selector = name
# Build the root element
root = TemplateElement(elemname, selector=selector,
subselector=subselector)
# Build an element to represent all the keys and values
elem = SubTemplateElement(root, tagname, selector=get_items)
elem.text = 1
# Return the template
return root
class ProtectedExpatParser(expatreader.ExpatParser):
"""An expat parser which disables DTD's and entities by default."""
def __init__(self, forbid_dtd=True, forbid_entities=True,
*args, **kwargs):
# Python 2.x old style class
expatreader.ExpatParser.__init__(self, *args, **kwargs)
self.forbid_dtd = forbid_dtd
self.forbid_entities = forbid_entities
def start_doctype_decl(self, name, sysid, pubid, has_internal_subset):
raise ValueError("Inline DTD forbidden")
def entity_decl(self, entityName, is_parameter_entity, value, base,
systemId, publicId, notationName):
raise ValueError("<!ENTITY> entity declaration forbidden")
def unparsed_entity_decl(self, name, base, sysid, pubid, notation_name):
# expat 1.2
raise ValueError("<!ENTITY> unparsed entity forbidden")
def external_entity_ref(self, context, base, systemId, publicId):
raise ValueError("<!ENTITY> external entity forbidden")
def notation_decl(self, name, base, sysid, pubid):
raise ValueError("<!ENTITY> notation forbidden")
def reset(self):
expatreader.ExpatParser.reset(self)
if self.forbid_dtd:
self._parser.StartDoctypeDeclHandler = self.start_doctype_decl
self._parser.EndDoctypeDeclHandler = None
if self.forbid_entities:
self._parser.EntityDeclHandler = self.entity_decl
self._parser.UnparsedEntityDeclHandler = self.unparsed_entity_decl
self._parser.ExternalEntityRefHandler = self.external_entity_ref
self._parser.NotationDeclHandler = self.notation_decl
try:
self._parser.SkippedEntityHandler = None
except AttributeError:
# some pyexpat versions do not support SkippedEntity
pass
def safe_minidom_parse_string(xml_string):
"""Parse an XML string using minidom safely."""
try:
return minidom.parseString(xml_string, parser=ProtectedExpatParser())
except (sax.SAXParseException, ValueError,
expat.ExpatError, LookupError) as e:
#NOTE(Vijaya Erukala): XML input such as
# <?xml version="1.0" encoding="TF-8"?>
# raises LookupError: unknown encoding: TF-8
raise exception.MalformedRequestBody(reason=str(e))
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