100 lines
3.5 KiB
Python
100 lines
3.5 KiB
Python
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"""Registration facilities for DOM. This module should not be used
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directly. Instead, the functions getDOMImplementation and
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registerDOMImplementation should be imported from xml.dom."""
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# This is a list of well-known implementations. Well-known names
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# should be published by posting to xml-sig@python.org, and are
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# subsequently recorded in this file.
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import sys
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well_known_implementations = {
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'minidom':'xml.dom.minidom',
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'4DOM': 'xml.dom.DOMImplementation',
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}
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# DOM implementations not officially registered should register
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# themselves with their
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registered = {}
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def registerDOMImplementation(name, factory):
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"""registerDOMImplementation(name, factory)
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Register the factory function with the name. The factory function
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should return an object which implements the DOMImplementation
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interface. The factory function can either return the same object,
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or a new one (e.g. if that implementation supports some
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customization)."""
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registered[name] = factory
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def _good_enough(dom, features):
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"_good_enough(dom, features) -> Return 1 if the dom offers the features"
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for f,v in features:
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if not dom.hasFeature(f,v):
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return 0
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return 1
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def getDOMImplementation(name=None, features=()):
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"""getDOMImplementation(name = None, features = ()) -> DOM implementation.
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Return a suitable DOM implementation. The name is either
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well-known, the module name of a DOM implementation, or None. If
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it is not None, imports the corresponding module and returns
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DOMImplementation object if the import succeeds.
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If name is not given, consider the available implementations to
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find one with the required feature set. If no implementation can
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be found, raise an ImportError. The features list must be a sequence
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of (feature, version) pairs which are passed to hasFeature."""
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import os
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creator = None
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mod = well_known_implementations.get(name)
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if mod:
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mod = __import__(mod, {}, {}, ['getDOMImplementation'])
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return mod.getDOMImplementation()
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elif name:
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return registered[name]()
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elif not sys.flags.ignore_environment and "PYTHON_DOM" in os.environ:
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return getDOMImplementation(name = os.environ["PYTHON_DOM"])
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# User did not specify a name, try implementations in arbitrary
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# order, returning the one that has the required features
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if isinstance(features, str):
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features = _parse_feature_string(features)
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for creator in registered.values():
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dom = creator()
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if _good_enough(dom, features):
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return dom
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for creator in well_known_implementations.keys():
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try:
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dom = getDOMImplementation(name = creator)
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except Exception: # typically ImportError, or AttributeError
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continue
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if _good_enough(dom, features):
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return dom
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raise ImportError("no suitable DOM implementation found")
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def _parse_feature_string(s):
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features = []
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parts = s.split()
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i = 0
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length = len(parts)
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while i < length:
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feature = parts[i]
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if feature[0] in "0123456789":
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raise ValueError("bad feature name: %r" % (feature,))
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i = i + 1
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version = None
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if i < length:
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v = parts[i]
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if v[0] in "0123456789":
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i = i + 1
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version = v
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features.append((feature, version))
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return tuple(features)
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