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# Copyright 2012 Google Inc.
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish, dis-
# tribute, sublicense, and/or sell copies of the Software, and to permit
# persons to whom the Software is furnished to do so, subject to the fol-
# lowing conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABIL-
# ITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
# SHALL THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
# IN THE SOFTWARE.
import types
from boto.exception import InvalidCorsError
from xml.sax import handler
# Relevant tags for the CORS XML document.
CORS_CONFIG = 'CorsConfig'
CORS = 'Cors'
ORIGINS = 'Origins'
ORIGIN = 'Origin'
METHODS = 'Methods'
METHOD = 'Method'
HEADERS = 'ResponseHeaders'
HEADER = 'ResponseHeader'
MAXAGESEC = 'MaxAgeSec'
class Cors(handler.ContentHandler):
"""Encapsulates the CORS configuration XML document"""
def __init__(self):
# List of CORS elements found within a CorsConfig element.
self.cors = []
# List of collections (e.g. Methods, ResponseHeaders, Origins)
# found within a CORS element. We use a list of lists here
# instead of a dictionary because the collections need to be
# preserved in the order in which they appear in the input XML
# document (and Python dictionary keys are inherently unordered).
# The elements on this list are two element tuples of the form
# (collection name, [list of collection contents]).
self.collections = []
# Lists of elements within a collection. Again a list is needed to
# preserve ordering but also because the same element may appear
# multiple times within a collection.
self.elements = []
# Dictionary mapping supported collection names to element types
# which may be contained within each.
self.legal_collections = {
ORIGINS : [ORIGIN],
METHODS : [METHOD],
HEADERS : [HEADER],
MAXAGESEC: []
}
# List of supported element types within any collection, used for
# checking validadity of a parsed element name.
self.legal_elements = [ORIGIN, METHOD, HEADER]
self.parse_level = 0
self.collection = None
self.element = None
def validateParseLevel(self, tag, level):
"""Verify parse level for a given tag."""
if self.parse_level != level:
raise InvalidCorsError('Invalid tag %s at parse level %d: ' %
(tag, self.parse_level))
def startElement(self, name, attrs, connection):
"""SAX XML logic for parsing new element found."""
if name == CORS_CONFIG:
self.validateParseLevel(name, 0)
self.parse_level += 1;
elif name == CORS:
self.validateParseLevel(name, 1)
self.parse_level += 1;
elif name in self.legal_collections:
self.validateParseLevel(name, 2)
self.parse_level += 1;
self.collection = name
elif name in self.legal_elements:
self.validateParseLevel(name, 3)
# Make sure this tag is found inside a collection tag.
if self.collection is None:
raise InvalidCorsError('Tag %s found outside collection' % name)
# Make sure this tag is allowed for the current collection tag.
if name not in self.legal_collections[self.collection]:
raise InvalidCorsError('Tag %s not allowed in %s collection' %
(name, self.collection))
self.element = name
else:
raise InvalidCorsError('Unsupported tag ' + name)
def endElement(self, name, value, connection):
"""SAX XML logic for parsing new element found."""
if name == CORS_CONFIG:
self.validateParseLevel(name, 1)
self.parse_level -= 1;
elif name == CORS:
self.validateParseLevel(name, 2)
self.parse_level -= 1;
# Terminating a CORS element, save any collections we found
# and re-initialize collections list.
self.cors.append(self.collections)
self.collections = []
elif name in self.legal_collections:
self.validateParseLevel(name, 3)
if name != self.collection:
raise InvalidCorsError('Mismatched start and end tags (%s/%s)' %
(self.collection, name))
self.parse_level -= 1;
if not self.legal_collections[name]:
# If this collection doesn't contain any sub-elements, store
# a tuple of name and this tag's element value.
self.collections.append((name, value.strip()))
else:
# Otherwise, we're terminating a collection of sub-elements,
# so store a tuple of name and list of contained elements.
self.collections.append((name, self.elements))
self.elements = []
self.collection = None
elif name in self.legal_elements:
self.validateParseLevel(name, 3)
# Make sure this tag is found inside a collection tag.
if self.collection is None:
raise InvalidCorsError('Tag %s found outside collection' % name)
# Make sure this end tag is allowed for the current collection tag.
if name not in self.legal_collections[self.collection]:
raise InvalidCorsError('Tag %s not allowed in %s collection' %
(name, self.collection))
if name != self.element:
raise InvalidCorsError('Mismatched start and end tags (%s/%s)' %
(self.element, name))
# Terminating an element tag, add it to the list of elements
# for the current collection.
self.elements.append((name, value.strip()))
self.element = None
else:
raise InvalidCorsError('Unsupported end tag ' + name)
def to_xml(self):
"""Convert CORS object into XML string representation."""
s = '<' + CORS_CONFIG + '>'
for collections in self.cors:
s += '<' + CORS + '>'
for (collection, elements_or_value) in collections:
assert collection is not None
s += '<' + collection + '>'
# If collection elements has type string, append atomic value,
# otherwise, append sequence of values in named tags.
if isinstance(elements_or_value, types.StringTypes):
s += elements_or_value
else:
for (name, value) in elements_or_value:
assert name is not None
assert value is not None
s += '<' + name + '>' + value + '</' + name + '>'
s += '</' + collection + '>'
s += '</' + CORS + '>'
s += '</' + CORS_CONFIG + '>'
return s
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