Re: [xml] Python bindings: per parser context error handlers

[Daniel Veillard <veillard redhat com>]

On Sun, Jan 12, 2003 at 04:37:22PM +0100, Stéphane Bidoul wrote:
> Hi,
> 
> I'd really like to have an error handler specific
> to a given parser context in the python bindings.
> 
> I dig a bit in the code and the list and could not find
> how it could be done with the current python bindings.
> 
> If there is a way to do it, please discard this message... 
> just give me a hint ;-).
> 
> If it's not possible, here is the approach I would propose.
> 
> As I understand it, the way to do that in C is
> to specify a callback in ctx->sax->error and ctx->vctx.error.

  yes,

> Thus, there would be a libxml2mod.xmlSetParserCtxtErrorHandler(ctxt,f)

  okay

> that would look like this in C:
> 
> PyObject *
> libxml_xmlSetParserCtxtErrorHandler(ATTRIBUTE_UNUSED PyObject *self, PyObject *args)
> {
>     PyObject *py_retval;
>     xmlParserCtxtPtr ctxt;
>     PyObject *pyobj_ctxt;
>     PyObject *f;
>     PyObject *arg;
> 
>     if (!PyArg_ParseTuple(args, (char *)"OOO:xmlSetParserCtxtErrorHandler", &pyobj_ctxt, &f, &arg))
>         return(NULL);
>     ctxt = (xmlParserCtxtPtr) PyparserCtxt_Get(pyobj_ctxt);
>     Py_XINCREF(f);
>     ((xmlParserCtxtPyCtxt *)ctxt->_private)->errorFunc = f;
>     Py_XINCREF(arg);
>     ((xmlParserCtxtPyCtxt *)ctxt->_private)->errorFuncArg = arg;
> 
>     ctxt->sax->error = libxml_xmlParserCtxtErrorFuncHandler;
>     ctxt->vctxt.error = libxml_xmlParserCtxtErrorFuncHandler;
> 
>     py_retval = libxml_intWrap(1);
>     return(py_retval);
> }
> 
> It involves storing the python callback in the _private field
> of xmlParserCtxt in a structure like this:

   Hum, yes that could work

> typedef struct 
> {
>     PyObject *errorFunc;
>     PyObject *errorFuncArg;
>     PyObject *warningFunc;
>     PyObject *warningFuncArg;
> } xmlParserCtxtPyCtxt;
> 
> That _private field would be initialized in libxml_xmlParserCtxtPtrWrap
> and destroyed in libxml_xmlFreeParserCtxt.

  I'm wondering if this really covers all cases. It seems okay but
a bit of checking seems necessary

> xmlParserCtxtErrorFuncHandler would then simply build the message string
> and call _private->errorFunc(_private->errorFuncArg,message).
> 
> My early experiments show it's doable.
> Does this make any sense at all?

  Yes, I'm a bit annoyed of using the _private field, but
since that's specific to the Python wrappers, why not.

> Is there a simpler approach, or something I missed,
> or a different, preferred approach?
> Should I go further and submit a complete patch?

  You need it, if you provide a patch which works that sounds fine :-)

Daniel

-- 
Daniel Veillard      | Red Hat Network https://rhn.redhat.com/
veillard redhat com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
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