Re: [xml] Substitution of nested entity references

[Daniel Veillard <veillard redhat com>]

On Mon, Apr 08, 2002 at 01:25:44PM +0200, Henke, Markus wrote:
> Hello Daniel,

> and sorry to broach that topic again, but i'd hoped
> that the approach mentioned below is possibly worth
> a comment...  8)

  Okay, let's see ...

> Kidding asside, i really won't to press for something
> or get on someone's nerves. It's just that my
> (libxml2 based) application (an API for COBOL) is
> short to a first release version and i've to decide
> whether i've to handle the substitution of nested
> entity references on application level or to rely
> on libxml.
> If it's not intended to do the substitution in
> libxml, it's maybe a good idea to point this out in
> the docs/reference for xmlNodeGetContent(),
> xmlGetProp() and the like!?
>
>
> TIA, Markus
>
> > -----Original Message-----
> > From: Henke, Markus 
> > Sent: Wednesday, March 20, 2002 4:08 PM
> > To: 'xml gnome org'
> > Subject: RE: [xml] xmlNodeGetContent() for XML_ENTITY_REF_NODE
> >
> >
> > Hello,
> >
> > and please apologize the long response time, but there
> > where other things to take care of (among them some holidays...8).
> >
> > In the meantime i've written a routine that does the (recursive)
> > substitution for (nested) entitiy reference, and it works fine for
> > me so far (code included below).
> > Anyhow, there are some points to clarify before it may be usefull
> > for libxml2:
> >
> > - Is it possible that someone can get a xmlDocPtr to a non
> >   well-formed (possibly due to cyclic entity references)
> >   document? This could cause serious problems in this
> >   routine... 8)

  Not possible, well at  least for a document which is the result of the
parsing process.

> > - Is xmlGetDocEntity() the proper way to lookup the entity
> >   declaration in that case? There is also xmlGetDtdEntity(),
> >   i'm not shure about the difference. Both take a xmlDocPtr
> >   as parameter (and i must confess that i haven't had the
> >   time by now to examine the source for that...)

  Use xmlGetDocEntity() it will look in both the internal subset and
external subset for the entities definitions.

> > - I've assumed that a xmlEntity have only child nodes with
> >   type XML_ENTITY_REF_NODE or XML_TEXT_NODE. Is this correct,
> >   and if not, which additional cases were to take into
> >   consideration?

  Well an entity content can be any "well balanced chunk", i.e.
the result of the content [43] production:

    http://www.w3.org/TR/REC-xml#NT-content

> > I would be glad to improve this routine if there is any
> > chance that it could be used in libxml2 to resolve nested
> > entity references, i guess at least xmlNodeGetContent and
> > xmlGetProp() [xmlGetNsProp()] should do so, the reference
> > says
> > ... Entity references are substituted... e.g.
> > ... This does the entity substitution...


  Hum, the best would be to testcase xmlResolveEntityRef() 
against the result of running the parser with entity substitution
turned on. If the result were the same for the set of files in the
test suite, that would be an indication that the code is good
enough for inclusion directly in libxml2.

Daniel

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