[GRASS-user] Question with Python-SWIG example [SEC=UNCLASSIFIED]

[Andrew MacIntyre]

> -----Original Message-----
> From: Glynn Clements [mailto:glynn at gclements.plus.com]
> Sent: Wednesday, 12 May 2010 1:43 AM
> To: Andrew MacIntyre
> Cc: GRASS user list; grass-dev at lists.osgeo.org
> Subject: RE: [GRASS-user] Question with Python-SWIG example
> [SEC=UNCLASSIFIED]
> 
> 
> Andrew MacIntyre wrote:
> 
> > From the SWIG examples I inferred the following type references for
> > the pointers in question:
> >
> > CELL*  =>  SWIGTYPE_p_CELL
> > FCELL*  =>  SWIGTYPE_p_FCELL
> > DCELL*  =>  SWIGTYPE_p_DCELL
> >
> > provided that CELL*/FCELL*/DCELL* are typedef'ed.
> >
> > So I expected that in pyobj_to_ptr() you could do something like
> 
> But I still don't see what happens when a function returns a CELL*
> which is subsequently passed to a function accepting a void*, or
> vice-versa. This is common enough that if SWIG can't handle it, we
> need to use something other than SWIG.

That seems to be what the SWIG Pointer Library function ptrcast() is
for, 
according to http://www.swig.org/Doc1.1/HTML/Typemaps.html, so 
something like (in Python):

	import GrassMod
	pCELL = GrassMod.Returns_CELLptr()
	pvoid = GrassMod.castptr(pCELL, "void *")
 	result = GrassMod.Takes_voidptr(pvoid)

(substitute the correct name of the GRASS SWIG module for "GrassMod")

> > If you decide to investigate using ctypes, the following links might
be
> > of interest:
> >
> > - http://starship.python.net/crew/theller/ctypes/old/codegen.html
> 
> AFAICT, this has been superseded by ctypeslib:
> 
> 	http://pypi.python.org/pypi/ctypeslib/

Thanks, the old page was something I had bookmarked.
 
> > - http://www.language-binding.net/pygccxml/pygccxml.html
> 
> I wasn't aware of this one.
> 
> I also found ctypesgen:
> 
> 	http://code.google.com/p/ctypesgen/

And that one's new to me, for which thanks.

Cheers,
Andrew.

-------------------------> "These thoughts are mine alone!" <---------
Andrew MacIntyre           Operations Branch
tel:   +61 2 6219 5356     Communications Infrastructure Division
fax:   +61 2 6253 3277     Australian Communications & Media Authority
email: andrew.macintyre at acma.gov.au            http://www.acma.gov.au/


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