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 os.environ.has_key("PYTHON_DOM"):

    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)