Re: [xml] Refactoring of the SAX interface for namespace support.

[Daniel Veillard <veillard redhat com>]

On Wed, Aug 13, 2003 at 09:43:19AM +0200, Fabrice Desré wrote:
>   Hi Daniel,
>
>   My preference goes to the distinct callbacks for elements and attributes.

  I think it's cleaner and more efficient than trying to push too many
arguments in a callback function. The drawback are for things like the python
bindings where the callback is marshalled into an expensive operation,
there would be more operations so the sax badings would be a bit slower.

> >       there is one thing to note, that a namespace() callback may actually
> >       provide the namepace binding for the element after startElementNs()
> >       was called like in <foo:bar xmlns:foo="bar"/>
>
>   Very good idea IMHO. This would make it easier to deal with documents 
> that use QNames in content. This callback should also be called to 
> notify when the default namespace changes.

  yep for any xmlns declaration found.

> >       there is another option even more disturbing from an API viewpoint:
> >         change name to simple const xmlChar * zero terminated to
> >         const xmlChar * with a lenght in bytes, like for the character
> >         callbacks.
> >       goal would be to minimize the number of string copies needed, this 
> > could
> >       be very effective for attribute values which operates on a 
> > non-bounded
> >       vocabulary. Minimizing the number of string allocated for tags can
> >       be done very easilly by the parser since the values pertains to a 
> > fixed
> >       vocabulary this is part of the enhancements I have long planned to do
> >       in libxml2.
>
> I'm not sure to understand you ont this. Do you mean that the attribute 
> callback could report the value of the attribute by chunks ? Or the name 
> of the attribute ?

  name of the attribute + the string + len of the string. 
Assuming no normalization or change is needed then the callback could then
operate directly from the memory buffer instead of neededing a string
allocation and duplication for each and every attribute value. A single
callback call per attribute or namespace but different:
    void attributeNs(const xmlChar *name, const xmlChar *value, int vlen,
                     const xmlChar *prefix, const xmlChar *URI);

   typically
     <h href="img.gif"/>
   would lead to 
     attributeNs("href", "img.gif\"/>", 7, NULL, NULL);
assuming no default namespace.

Daniel

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