zeroinstall/injector/qdom.py

   1 """A quick DOM implementation.
   2
   3 Python's xml.dom is very slow. The xml.sax module is also slow (as it imports urllib2).
   4 This is our light-weight version.
   5 """
   6
   7 # Copyright (C) 2009, Thomas Leonard
   8 # See the README file for details, or visit http://0install.net.
   9
  10 from xml.parsers import expat
  11
  12 class Element(object):
  13         """An XML element.
  14         @ivar uri: the element's namespace
  15         @type uri: str
  16         @ivar name: the element's localName
  17         @type name: str
  18         @ivar attrs: the element's attributes (key is in the form [namespace " "] localName
  19         @type attrs: {str: str}
  20         @ivar childNodes: children
  21         @type childNodes: [L{Element}]
  22         @ivar content: the text content
  23         @type content: str"""
  24         __slots__ = ['uri', 'name', 'attrs', 'childNodes', 'content']
  25         def __init__(self, uri, name, attrs):
  26                 self.uri = uri
  27                 self.name = name
  28                 self.attrs = attrs.copy()
  29                 self.childNodes = []
  30
  31         def __str__(self):
  32                 attrs = [n + '=' + self.attrs[n] for n in self.attrs]
  33                 start = '<{%s}%s %s' % (self.uri, self.name, ' '.join(attrs))
  34                 if self.childNodes:
  35                         return start + '>' + '\n'.join(map(str, self.childNodes)) + ('</%s>' % (self.name))
  36                 elif self.content:
  37                         return start + '>' + self.content + ('</%s>' % (self.name))
  38                 else:
  39                         return start + '/>'
  40
  41         def getAttribute(self, name):
  42                 return self.attrs.get(name, None)
  43
  44 class QSAXhandler:
  45         """SAXHandler that builds a tree of L{Element}s"""
  46         def __init__(self):
  47                 self.stack = []
  48
  49         def startElementNS(self, fullname, attrs):
  50                 split = fullname.split(' ', 1)
  51                 if len(split) == 2:
  52                         self.stack.append(Element(split[0], split[1], attrs))
  53                 else:
  54                         self.stack.append(Element(None, fullname, attrs))
  55                 self.contents = ''
  56
  57         def characters(self, data):
  58                 self.contents += data
  59
  60         def endElementNS(self, name):
  61                 contents = self.contents.strip()
  62                 self.stack[-1].content = contents
  63                 self.contents = ''
  64                 new = self.stack.pop()
  65                 if self.stack:
  66                         self.stack[-1].childNodes.append(new)
  67                 else:
  68                         self.doc = new
  69
  70 def parse(source):
  71         """Parse an XML stream into a tree of L{Element}s.
  72         @param source: data to parse
  73         @type source: file
  74         @return: the root
  75         @rtype: L{Element}"""
  76         handler = QSAXhandler()
  77         parser = expat.ParserCreate(namespace_separator = ' ')
  78
  79         parser.StartElementHandler = handler.startElementNS
  80         parser.EndElementHandler = handler.endElementNS
  81         parser.CharacterDataHandler = handler.characters
  82
  83         parser.ParseFile(source)
  84         return handler.doc