jpayne@68: """Registration facilities for DOM. This module should not be used
jpayne@68: directly. Instead, the functions getDOMImplementation and
jpayne@68: registerDOMImplementation should be imported from xml.dom."""
jpayne@68: 
jpayne@68: # This is a list of well-known implementations.  Well-known names
jpayne@68: # should be published by posting to xml-sig@python.org, and are
jpayne@68: # subsequently recorded in this file.
jpayne@68: 
jpayne@68: import sys
jpayne@68: 
jpayne@68: well_known_implementations = {
jpayne@68:     'minidom':'xml.dom.minidom',
jpayne@68:     '4DOM': 'xml.dom.DOMImplementation',
jpayne@68:     }
jpayne@68: 
jpayne@68: # DOM implementations not officially registered should register
jpayne@68: # themselves with their
jpayne@68: 
jpayne@68: registered = {}
jpayne@68: 
jpayne@68: def registerDOMImplementation(name, factory):
jpayne@68:     """registerDOMImplementation(name, factory)
jpayne@68: 
jpayne@68:     Register the factory function with the name. The factory function
jpayne@68:     should return an object which implements the DOMImplementation
jpayne@68:     interface. The factory function can either return the same object,
jpayne@68:     or a new one (e.g. if that implementation supports some
jpayne@68:     customization)."""
jpayne@68: 
jpayne@68:     registered[name] = factory
jpayne@68: 
jpayne@68: def _good_enough(dom, features):
jpayne@68:     "_good_enough(dom, features) -> Return 1 if the dom offers the features"
jpayne@68:     for f,v in features:
jpayne@68:         if not dom.hasFeature(f,v):
jpayne@68:             return 0
jpayne@68:     return 1
jpayne@68: 
jpayne@68: def getDOMImplementation(name=None, features=()):
jpayne@68:     """getDOMImplementation(name = None, features = ()) -> DOM implementation.
jpayne@68: 
jpayne@68:     Return a suitable DOM implementation. The name is either
jpayne@68:     well-known, the module name of a DOM implementation, or None. If
jpayne@68:     it is not None, imports the corresponding module and returns
jpayne@68:     DOMImplementation object if the import succeeds.
jpayne@68: 
jpayne@68:     If name is not given, consider the available implementations to
jpayne@68:     find one with the required feature set. If no implementation can
jpayne@68:     be found, raise an ImportError. The features list must be a sequence
jpayne@68:     of (feature, version) pairs which are passed to hasFeature."""
jpayne@68: 
jpayne@68:     import os
jpayne@68:     creator = None
jpayne@68:     mod = well_known_implementations.get(name)
jpayne@68:     if mod:
jpayne@68:         mod = __import__(mod, {}, {}, ['getDOMImplementation'])
jpayne@68:         return mod.getDOMImplementation()
jpayne@68:     elif name:
jpayne@68:         return registered[name]()
jpayne@68:     elif not sys.flags.ignore_environment and "PYTHON_DOM" in os.environ:
jpayne@68:         return getDOMImplementation(name = os.environ["PYTHON_DOM"])
jpayne@68: 
jpayne@68:     # User did not specify a name, try implementations in arbitrary
jpayne@68:     # order, returning the one that has the required features
jpayne@68:     if isinstance(features, str):
jpayne@68:         features = _parse_feature_string(features)
jpayne@68:     for creator in registered.values():
jpayne@68:         dom = creator()
jpayne@68:         if _good_enough(dom, features):
jpayne@68:             return dom
jpayne@68: 
jpayne@68:     for creator in well_known_implementations.keys():
jpayne@68:         try:
jpayne@68:             dom = getDOMImplementation(name = creator)
jpayne@68:         except Exception: # typically ImportError, or AttributeError
jpayne@68:             continue
jpayne@68:         if _good_enough(dom, features):
jpayne@68:             return dom
jpayne@68: 
jpayne@68:     raise ImportError("no suitable DOM implementation found")
jpayne@68: 
jpayne@68: def _parse_feature_string(s):
jpayne@68:     features = []
jpayne@68:     parts = s.split()
jpayne@68:     i = 0
jpayne@68:     length = len(parts)
jpayne@68:     while i < length:
jpayne@68:         feature = parts[i]
jpayne@68:         if feature[0] in "0123456789":
jpayne@68:             raise ValueError("bad feature name: %r" % (feature,))
jpayne@68:         i = i + 1
jpayne@68:         version = None
jpayne@68:         if i < length:
jpayne@68:             v = parts[i]
jpayne@68:             if v[0] in "0123456789":
jpayne@68:                 i = i + 1
jpayne@68:                 version = v
jpayne@68:         features.append((feature, version))
jpayne@68:     return tuple(features)