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##############################################################################
#
# Copyright (c) 2005 Zope Corporation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
"""Type sniffer for page template input
$Id$
"""
import xml.parsers.expat
XML_PREFIXES = [
"<?xml", # ascii, utf-8
"\xef\xbb\xbf<?xml", # utf-8 w/ byte order mark
"\0<\0?\0x\0m\0l", # utf-16 big endian
"<\0?\0x\0m\0l\0", # utf-16 little endian
"\xfe\xff\0<\0?\0x\0m\0l", # utf-16 big endian w/ byte order mark
"\xff\xfe<\0?\0x\0m\0l\0", # utf-16 little endian w/ byte order mark
]
XML_PREFIX_MAX_LENGTH = max(map(len, XML_PREFIXES))
class NamespaceFound(Exception):
# This exception is throwned by the parser when a namespace is
# found to stop the parsing.
pass
def StartNamespaceDeclHandler(prefix, url):
# Called when an element contains a namespace declaration.
raise NamespaceFound
def sniff_type(text):
"""Return 'text/xml' if text appears to be XML, otherwise return None.
o if the document contains the xml process header <?xml ... ?>
o if the document contains any namespace declarations
"""
# Check the xml processing header
for prefix in XML_PREFIXES:
if text.startswith(prefix):
return "text/xml"
# Check if the document contains any namespace declarations
parser = xml.parsers.expat.ParserCreate(namespace_separator=' ')
parser.StartNamespaceDeclHandler = StartNamespaceDeclHandler
try:
parser.Parse(text)
except xml.parsers.expat.ExpatError:
return None
except NamespaceFound:
return "text/xml"
else:
return None
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