Package lxml :: Module ElementInclude
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Source Code for Module lxml.ElementInclude

  1  # 
  2  # ElementTree 
  3  # $Id: ElementInclude.py 1862 2004-06-18 07:31:02Z Fredrik $ 
  4  # 
  5  # limited xinclude support for element trees 
  6  # 
  7  # history: 
  8  # 2003-08-15 fl   created 
  9  # 2003-11-14 fl   fixed default loader 
 10  # 
 11  # Copyright (c) 2003-2004 by Fredrik Lundh.  All rights reserved. 
 12  # 
 13  # fredrik@pythonware.com 
 14  # http://www.pythonware.com 
 15  # 
 16  # -------------------------------------------------------------------- 
 17  # The ElementTree toolkit is 
 18  # 
 19  # Copyright (c) 1999-2004 by Fredrik Lundh 
 20  # 
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 26  # its associated documentation for any purpose and without fee is 
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 29  # notice appear in supporting documentation, and that the name of 
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 32  # prior permission. 
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 40  # ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 
 41  # OF THIS SOFTWARE. 
 42  # -------------------------------------------------------------------- 
 43   
 44  """ 
 45  Limited XInclude support for the ElementTree package. 
 46   
 47  While lxml.etree has full support for XInclude (see 
 48  `etree.ElementTree.xinclude()`), this module provides a simpler, pure 
 49  Python, ElementTree compatible implementation that supports a simple 
 50  form of custom URL resolvers. 
 51  """ 
 52   
 53  from lxml import etree 
 54  try: 
 55      from urlparse import urljoin 
 56      from urllib2 import urlopen 
 57  except ImportError: 
 58      # Python 3 
 59      from urllib.parse import urljoin 
 60      from urllib.request import urlopen 
 61   
 62  XINCLUDE = "{http://www.w3.org/2001/XInclude}" 
 63   
 64  XINCLUDE_INCLUDE = XINCLUDE + "include" 
 65  XINCLUDE_FALLBACK = XINCLUDE + "fallback" 
 66  XINCLUDE_ITER_TAG = XINCLUDE + "*" 
 67   
 68  # For security reasons, the inclusion depth is limited to this read-only value by default. 
 69  DEFAULT_MAX_INCLUSION_DEPTH = 6 
 70   
 71   
 72  ## 
 73  # Fatal include error. 
 74   
75 -class FatalIncludeError(etree.LxmlSyntaxError):
76 pass
77 78
79 -class LimitedRecursiveIncludeError(FatalIncludeError):
80 pass
81 82 83 ## 84 # ET compatible default loader. 85 # This loader reads an included resource from disk. 86 # 87 # @param href Resource reference. 88 # @param parse Parse mode. Either "xml" or "text". 89 # @param encoding Optional text encoding. 90 # @return The expanded resource. If the parse mode is "xml", this 91 # is an ElementTree instance. If the parse mode is "text", this 92 # is a Unicode string. If the loader fails, it can return None 93 # or raise an IOError exception. 94 # @throws IOError If the loader fails to load the resource. 95
96 -def default_loader(href, parse, encoding=None):
97 file = open(href, 'rb') 98 if parse == "xml": 99 data = etree.parse(file).getroot() 100 else: 101 data = file.read() 102 if not encoding: 103 encoding = 'utf-8' 104 data = data.decode(encoding) 105 file.close() 106 return data
107 108 109 ## 110 # Default loader used by lxml.etree - handles custom resolvers properly 111 # 112
113 -def _lxml_default_loader(href, parse, encoding=None, parser=None):
114 if parse == "xml": 115 data = etree.parse(href, parser).getroot() 116 else: 117 if "://" in href: 118 f = urlopen(href) 119 else: 120 f = open(href, 'rb') 121 data = f.read() 122 f.close() 123 if not encoding: 124 encoding = 'utf-8' 125 data = data.decode(encoding) 126 return data
127 128 129 ## 130 # Wrapper for ET compatibility - drops the parser 131
132 -def _wrap_et_loader(loader):
133 def load(href, parse, encoding=None, parser=None): 134 return loader(href, parse, encoding)
135 return load 136 137 138 ## 139 # Expand XInclude directives. 140 # 141 # @param elem Root element. 142 # @param loader Optional resource loader. If omitted, it defaults 143 # to {@link default_loader}. If given, it should be a callable 144 # that implements the same interface as <b>default_loader</b>. 145 # @param base_url The base URL of the original file, to resolve 146 # relative include file references. 147 # @param max_depth The maximum number of recursive inclusions. 148 # Limited to reduce the risk of malicious content explosion. 149 # Pass None to disable the limitation. 150 # @throws LimitedRecursiveIncludeError If the {@link max_depth} was exceeded. 151 # @throws FatalIncludeError If the function fails to include a given 152 # resource, or if the tree contains malformed XInclude elements. 153 # @throws IOError If the function fails to load a given resource. 154 # @returns the node or its replacement if it was an XInclude node 155
156 -def include(elem, loader=None, base_url=None, 157 max_depth=DEFAULT_MAX_INCLUSION_DEPTH):
158 if max_depth is None: 159 max_depth = -1 160 elif max_depth < 0: 161 raise ValueError("expected non-negative depth or None for 'max_depth', got %r" % max_depth) 162 163 if base_url is None: 164 if hasattr(elem, 'getroot'): 165 tree = elem 166 elem = elem.getroot() 167 else: 168 tree = elem.getroottree() 169 if hasattr(tree, 'docinfo'): 170 base_url = tree.docinfo.URL 171 elif hasattr(elem, 'getroot'): 172 elem = elem.getroot() 173 _include(elem, loader, base_url, max_depth)
174 175
176 -def _include(elem, loader=None, base_url=None, 177 max_depth=DEFAULT_MAX_INCLUSION_DEPTH, _parent_hrefs=None):
178 if loader is not None: 179 load_include = _wrap_et_loader(loader) 180 else: 181 load_include = _lxml_default_loader 182 183 if _parent_hrefs is None: 184 _parent_hrefs = set() 185 186 parser = elem.getroottree().parser 187 188 include_elements = list( 189 elem.iter(XINCLUDE_ITER_TAG)) 190 191 for e in include_elements: 192 if e.tag == XINCLUDE_INCLUDE: 193 # process xinclude directive 194 href = urljoin(base_url, e.get("href")) 195 parse = e.get("parse", "xml") 196 parent = e.getparent() 197 if parse == "xml": 198 if href in _parent_hrefs: 199 raise FatalIncludeError( 200 "recursive include of %r detected" % href 201 ) 202 if max_depth == 0: 203 raise LimitedRecursiveIncludeError( 204 "maximum xinclude depth reached when including file %s" % href) 205 _parent_hrefs.add(href) 206 node = load_include(href, parse, parser=parser) 207 if node is None: 208 raise FatalIncludeError( 209 "cannot load %r as %r" % (href, parse) 210 ) 211 node = _include(node, loader, href, max_depth - 1, _parent_hrefs) 212 if e.tail: 213 node.tail = (node.tail or "") + e.tail 214 if parent is None: 215 return node # replaced the root node! 216 parent.replace(e, node) 217 elif parse == "text": 218 text = load_include(href, parse, encoding=e.get("encoding")) 219 if text is None: 220 raise FatalIncludeError( 221 "cannot load %r as %r" % (href, parse) 222 ) 223 predecessor = e.getprevious() 224 if predecessor is not None: 225 predecessor.tail = (predecessor.tail or "") + text 226 elif parent is None: 227 return text # replaced the root node! 228 else: 229 parent.text = (parent.text or "") + text + (e.tail or "") 230 parent.remove(e) 231 else: 232 raise FatalIncludeError( 233 "unknown parse type in xi:include tag (%r)" % parse 234 ) 235 elif e.tag == XINCLUDE_FALLBACK: 236 parent = e.getparent() 237 if parent is not None and parent.tag != XINCLUDE_INCLUDE: 238 raise FatalIncludeError( 239 "xi:fallback tag must be child of xi:include (%r)" % e.tag 240 ) 241 else: 242 raise FatalIncludeError( 243 "Invalid element found in XInclude namespace (%r)" % e.tag 244 ) 245 return elem
246