Re: libxml2 application data

Philippe, all,

I was wrong: The integer $$node is in fact the pointer to XML::LibXML's own 
structure (attached to node's _private slot), so it is not a stable ID of a 
node - it is created when a node is first assigned to a Perl SV and destroyed 
if the last Perl SV for that node goes out of scope. One has to maintain the 
Perl scalars involved to make sure the ID is stable. So you would have to do 
e.g. 

  $hash->{$$node}=[$node,$your_data]; #store your data

and

 $hash->{$$node}[1] # retrieve your data

Excuse the confusion,

-- Petr

On Monday 22 December 2008 23:43:56 I wrote:
> Dne Monday 22 December 2008 14:48:20 philippe marguinaud napsal(a):
> > Hi Petr,
> >
> > I have thought about using the $$node trick, but when the XML tree is
> > modified ( for instance when a node is deleted ), then some of the nodes
> > are re-numbered.
>
> No, I doubt they get re-numbered as you put it. A scenario that I can think
> of is that you remove a node from the DOM and create a new one. In such a
> case of course the new node can take the memory address left by the old
> one, provided the old node was destroyed, and thus the new node's $$node
> would be equal to the old one. You have to take care of such cases in your
> code (e.g. before you make a DOM operation that destroys a node, you should
> remove the associated data from your hash).
>
> > I can provide a demo script to illustrate this if you
> > want.
>
> please do if you can think of some other case.
>
> > So I am stuck with XML::LibXML, I will have to find another module.
> >
> > Regards,
> > Philippe
>
> I'm sorry. XML::LibXML does not currently provide the feature you ask for.
> I suggested a possible work-around. Other module may better suit your
> needs, I don't know them. But if you decide to implement user data over
> XML::LibXML, here are a few further suggestions:
>
> You may wrap the critical DOM functions to deal with user-data
> transparently. If you do this meticulously, you can either replace
> XML::LibXML's DOM calls or create a new DOM layer on top of XML::LibXML.
> This all can be done in your application without modifying XML::LibXML
> itself.
>
> You may also experiment with XML::LibXML's source code and find an way to
> implement user data inside XML::LibXML (either using _private or
> otherwise). I usually take patches for new features that make sense and
> that include self-tests and documentation. Any effort is welcome.
>
> -- Petr
>
> > > From: [email protected]
> > > To: [email protected]
> > > Subject: Re: libxml2 application data
> > > Date: Mon, 22 Dec 2008 12:14:20 +0100
> > > CC: [email protected]
> > >
> > > No, XML::LibXML uses the _private slot for its own purposes. I'd
> > > suggest using a Perl hash and $$node as key ($$node is an integer
> > > that uniquely identifies a libxml2's node).
> > >
> > > -- Petr
> > >
> > > On ne 21. prosince 2008, philippe marguinaud wrote:
> > > > Hi all,
> > > >
> > > > I have written C programs using libxml2 and used to attach
> > > > application data to xml nodes using the _private field of node
> > > > structs. I would like to know whether it is possible to do that
> > > > using the Perl bindings; I have not seen anything like that in
> > > > the pod documentation.
> > > >
> > > > Regards,
> > > >
> > > > Philippe
> > > >
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