[XML-SIG] SAX2: Parser properties

[Lars Marius Garshol]

The first three properties come from the JavaSAX proposal, while the
last one was invented by yours truly.


http://xml.org/sax/properties/namespace-sep <String> (write-only)
  Set the separator to be used between the URI part of a name and the
  local part of a name when namespace processing is being performed
  (see the http://xml.org/sax/features/namespaces feature).  By
  default, the separator is a single space.  This property may not be
  set while a parse is in progress (throws a SAXNotSupportedException).

http://xml.org/sax/properties/dom-node <Node> (read-only)
  Get the DOM node currently being visited, if the SAX parser is
  iterating over a DOM tree.  If the parser recognises and supports
  this property but is not currently visiting a DOM node, it should
  return null (this is a good way to check for availability before the
  parse begins).

  This property doesn't make much sense for Python, but I see no point
  in leaving it out, either.

http://xml.org/sax/properties/xml-string <String> (read-only)
  Get the literal string of characters associated with the current
  event.  If the parser recognises and supports this property but is
  not currently parsing text, it should return null (this is a good
  way to check for availability before the parse begins).  I stole
  this idea from Expat.


In addition, I think PySAX needs the following property:

http://python.org/sax/properties/data-encoding <String> (read/write)
  This property can be used to control which character encoding is
  used for data events that come from the parser. In Java this is not
  an issue since all strings are Unicode, but in Python it is. Expat
  reports UTF-8, while xmlproc/xmllib just pass on whatever they're
  given.

  Do we need a special SAXEncodingNotSupportedException for this?
  Otherwise it may be impossible to tell whether the parser doesn't
  support this at all or whether it just doesn't support this
  particular encoding.

--Lars M.