AppPkg/Applications/Python/Python-2.7.10/Lib/xml/dom/domreg.py

   1 """Registration facilities for DOM. This module should not be used
   2 directly. Instead, the functions getDOMImplementation and
   3 registerDOMImplementation should be imported from xml.dom."""
   4
   5 from xml.dom.minicompat import *  # isinstance, StringTypes
   6
   7 # This is a list of well-known implementations.  Well-known names
   8 # should be published by posting to xml-sig@python.org, and are
   9 # subsequently recorded in this file.
  10
  11 well_known_implementations = {
  12     'minidom':'xml.dom.minidom',
  13     '4DOM': 'xml.dom.DOMImplementation',
  14     }
  15
  16 # DOM implementations not officially registered should register
  17 # themselves with their
  18
  19 registered = {}
  20
  21 def registerDOMImplementation(name, factory):
  22     """registerDOMImplementation(name, factory)
  23
  24     Register the factory function with the name. The factory function
  25     should return an object which implements the DOMImplementation
  26     interface. The factory function can either return the same object,
  27     or a new one (e.g. if that implementation supports some
  28     customization)."""
  29
  30     registered[name] = factory
  31
  32 def _good_enough(dom, features):
  33     "_good_enough(dom, features) -> Return 1 if the dom offers the features"
  34     for f,v in features:
  35         if not dom.hasFeature(f,v):
  36             return 0
  37     return 1
  38
  39 def getDOMImplementation(name = None, features = ()):
  40     """getDOMImplementation(name = None, features = ()) -> DOM implementation.
  41
  42     Return a suitable DOM implementation. The name is either
  43     well-known, the module name of a DOM implementation, or None. If
  44     it is not None, imports the corresponding module and returns
  45     DOMImplementation object if the import succeeds.
  46
  47     If name is not given, consider the available implementations to
  48     find one with the required feature set. If no implementation can
  49     be found, raise an ImportError. The features list must be a sequence
  50     of (feature, version) pairs which are passed to hasFeature."""
  51
  52     import os
  53     creator = None
  54     mod = well_known_implementations.get(name)
  55     if mod:
  56         mod = __import__(mod, {}, {}, ['getDOMImplementation'])
  57         return mod.getDOMImplementation()
  58     elif name:
  59         return registered[name]()
  60     elif "PYTHON_DOM" in os.environ:
  61         return getDOMImplementation(name = os.environ["PYTHON_DOM"])
  62
  63     # User did not specify a name, try implementations in arbitrary
  64     # order, returning the one that has the required features
  65     if isinstance(features, StringTypes):
  66         features = _parse_feature_string(features)
  67     for creator in registered.values():
  68         dom = creator()
  69         if _good_enough(dom, features):
  70             return dom
  71
  72     for creator in well_known_implementations.keys():
  73         try:
  74             dom = getDOMImplementation(name = creator)
  75         except StandardError: # typically ImportError, or AttributeError
  76             continue
  77         if _good_enough(dom, features):
  78             return dom
  79
  80     raise ImportError,"no suitable DOM implementation found"
  81
  82 def _parse_feature_string(s):
  83     features = []
  84     parts = s.split()
  85     i = 0
  86     length = len(parts)
  87     while i < length:
  88         feature = parts[i]
  89         if feature[0] in "0123456789":
  90             raise ValueError, "bad feature name: %r" % (feature,)
  91         i = i + 1
  92         version = None
  93         if i < length:
  94             v = parts[i]
  95             if v[0] in "0123456789":
  96                 i = i + 1
  97                 version = v
  98         features.append((feature, version))
  99     return tuple(features)