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OpenStack Study: xmlutil.py

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# 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

import six

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.openstack.common.gettextutils import _

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'

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def validate_schema(xml, schema_name, version='v1.1'):

    if isinstance(xml, str):

        xml = etree.fromstring(xml)

    base_path = 'nova/api/openstack/compute/schemas/'

    if schema_name not in ('atom', 'atom-link'):

        base_path += '%s/' % version

    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)

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class Selector(object):

"""Selects datum to operate on from an object."""

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    def __init__(self, *chain):

        """Initialize the selector.

        Each argument is a subsequent index into the object.

        """

        self.chain = chain

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    def __repr__(self):

        """Return a representation of the selector."""

        return "Selector" + repr(self.chain)

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    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:

                if obj == '':

                    return ''

                # 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())

def get_items_without_dict(obj):

    """Get items in obj but omit any items containing a dict."""

    obj_list = list(obj.items())

    for item in obj_list:

        if isinstance(list(item)[1], dict):

            obj_list.remove(item)

    return obj_list

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def get_items(obj):

    """Get items in obj."""

    return list(obj.items())

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def get_items_without_dict(obj):

    """Get items in obj but omit any items containing a dict."""

    obj_list = list(obj.items())

    for item in obj_list:

        if isinstance(list(item)[1], dict):

            obj_list.remove(item)

    return obj_list

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class EmptyStringSelector(Selector):

"""Returns the empty string if Selector would return None."""

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    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 ""

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class ConstantSelector(object):

"""Returns a constant."""

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    def __init__(self, value):

        """Initialize the selector.

        :param value: The value to return.

        """

        self.value = value

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    def __repr__(self):

        """Return a representation of the selector."""

        return repr(self.value)

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    def __call__(self, _obj, _do_raise=False):

        """Select a datum to operate on.

        Returns a constant value.  Compatible with

        Selector.__call__().

        """

        return self.value

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class TemplateElement(object):

"""Represent an element in the template."""

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    def __init__(self, tag, attrib=None, selector=None, subselector=None,

                 colon_ns=False, **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.

        :colon_ns: An optional flag indicating whether to support k:v

                   type tagname, if True the k:v type tagname will

                   be supported by adding the k into the namespace.

        """

        # 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 = {}

        self.colon_ns = colon_ns

        # 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)

**** CubicPower OpenStack Study ****

    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)))

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    def __len__(self):

        """Return the number of child elements."""

        return len(self._children)

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    def __contains__(self, key):

        """Determine whether a child node named by key exists."""

        return key in self._childmap

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    def __getitem__(self, idx):

        """Retrieve a child node by index or name."""

        if isinstance(idx, six.string_types):

            # Allow access by node name

            return self._childmap[idx]

        else:

            return self._children[idx]

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

    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)

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

    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]

**** CubicPower OpenStack Study ****

    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]

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

    def keys(self):

        """Return the attribute names."""

        return self.attrib.keys()

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    def items(self):

        """Return the attribute names and values."""

        return self.attrib.items()

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    def unwrap(self):

        """Unwraps a template to return a template element."""

        # We are a template element

        return self

**** CubicPower OpenStack Study ****

    def wrap(self):

        """Wraps a template element to return a template."""

        # Wrap in a basic Template

        return Template(self)

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

    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

        if self.colon_ns:

            if ':' in tagname:

                if nsmap is None:

                    nsmap = {}

                colon_key, colon_name = tagname.split(':')

                nsmap[colon_key] = colon_key

                tagname = '{%s}%s' % (colon_key, colon_name)

        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

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

    def _text_del(self):

        self._text = None

    text = property(_text_get, _text_set, _text_del)

**** CubicPower OpenStack Study ****

    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' %

                (' '.join(contents), ''.join(children), self.tag))

def SubTemplateElement(parent, tag, attrib=None, selector=None,

                       subselector=None, colon_ns=False, **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, colon_ns=colon_ns)

    # Append the parent safely

    if parent is not None:

        parent.append(elem)

    return elem

**** CubicPower OpenStack Study ****

def SubTemplateElement(parent, tag, attrib=None, selector=None,

                       subselector=None, colon_ns=False, **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, colon_ns=colon_ns)

    # Append the parent safely

    if parent is not None:

        parent.append(elem)

    return elem

**** CubicPower OpenStack Study ****

class Template(object):

"""Represent a template."""

**** CubicPower OpenStack Study ****

    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)

**** CubicPower OpenStack Study ****

    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]

**** CubicPower OpenStack Study ****

    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)

**** CubicPower OpenStack Study ****

    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)

**** CubicPower OpenStack Study ****

    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]

**** CubicPower OpenStack Study ****

    def _nsmap(self):

        """Hook method for computing the namespace dictionary.

        An overridable hook method to return the namespace dictionary.

        """

        return self.nsmap.copy()

**** CubicPower OpenStack Study ****

    def unwrap(self):

        """Unwraps a template to return a template element."""

        # Return the root element

        return self.root

**** CubicPower OpenStack Study ****

    def wrap(self):

        """Wraps a template element to return a template."""

        # We are a template

        return self

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

    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())

**** CubicPower OpenStack Study ****

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.

"""

**** CubicPower OpenStack Study ****

    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 = []

**** CubicPower OpenStack Study ****

    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)))

**** CubicPower OpenStack Study ****

    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]

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

    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)

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

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.

"""

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

    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)))

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

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

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

    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  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, colon_ns=False, root=None,

                   ignore_sub_dicts=False):

    """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.

    :param root: if None, this will create the root.

    :param ignore_sub_dicts: If True, ignores any dict objects inside the

                             object. If False, causes an error if there is a

                             dict object present.

    """

    # 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

    if not root:

        # Build the root element

        root = TemplateElement(elemname, selector=selector,

                               subselector=subselector, colon_ns=colon_ns)

    choice = get_items if ignore_sub_dicts is False else get_items_without_dict

    # Build an element to represent all the keys and values

    elem = SubTemplateElement(root, tagname, selector=choice,

                              colon_ns=colon_ns)

    elem.text = 1

    # Return the template

    return root

**** CubicPower OpenStack Study ****

def make_links(parent, selector=None):

    """Attach an Atom  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

**** CubicPower OpenStack Study ****

def make_flat_dict(name, selector=None, subselector=None,

                   ns=None, colon_ns=False, root=None,

                   ignore_sub_dicts=False):

    """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.

    :param root: if None, this will create the root.

    :param ignore_sub_dicts: If True, ignores any dict objects inside the

                             object. If False, causes an error if there is a

                             dict object present.

    """

    # 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

    if not root:

        # Build the root element

        root = TemplateElement(elemname, selector=selector,

                               subselector=subselector, colon_ns=colon_ns)

    choice = get_items if ignore_sub_dicts is False else get_items_without_dict

    # Build an element to represent all the keys and values

    elem = SubTemplateElement(root, tagname, selector=choice,

                              colon_ns=colon_ns)

    elem.text = 1

    # Return the template

    return root

**** CubicPower OpenStack Study ****

class ProtectedExpatParser(expatreader.ExpatParser):

"""An expat parser which disables DTD's and entities by

**** CubicPower OpenStack Study ****

    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

**** CubicPower OpenStack Study ****

    def start_doctype_decl(self, name, sysid, pubid, has_internal_subset):

        raise ValueError("Inline DTD forbidden")

**** CubicPower OpenStack Study ****

    def entity_decl(self, entityName, is_parameter_entity, value, base,

                    systemId, publicId, notationName):

        raise ValueError(" entity declaration forbidden")

**** CubicPower OpenStack Study ****

    def unparsed_entity_decl(self, name, base, sysid, pubid, notation_name):

        # expat 1.2

        raise ValueError(" unparsed entity forbidden")

**** CubicPower OpenStack Study ****

    def external_entity_ref(self, context, base, systemId, publicId):

        raise ValueError(" external entity forbidden")

**** CubicPower OpenStack Study ****

    def notation_decl(self, name, base, sysid, pubid):

        raise ValueError(" notation forbidden")

**** CubicPower OpenStack Study ****

    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

        #                      

        #                      raises LookupError: unknown encoding: TF-8

        raise exception.MalformedRequestBody(reason=str(e))

**** CubicPower OpenStack Study ****

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

        #                      

        #                      raises LookupError: unknown encoding: TF-8

        raise exception.MalformedRequestBody(reason=str(e))