Message-ID: <Pine.LNX.4.61.0512120812060.4551@gannet.stats>
Date: 2005-12-12T08:16:55Z
From: Brian Ripley
Subject: external pointers
In-Reply-To: <Pine.LNX.4.44.0512120849200.26218-100000@reclus.nhh.no>
On Mon, 12 Dec 2005, Roger Bivand wrote:
>> Where would be best to read about externalptr? I'm having trouble
>> finding material in the manuals or the site-search.
>>
>> And would I need to use all the .Call machinery and C headers and SEXP
>> etc in order to handle externalptr objects?
>
> One package using externalptr is rgdal - Tim Keitt wrote the bindings to
> the external GDAL library for reading raster images to first return a
> pointer to a dataset (on disk) opened by GDAL, then to use the object to
> retrieve (parts of) the data. Most of the .Call/SEXP machinery is there
> (for the C++ case, GDAL is C++, so GDAL manages its own memory for its
> objects). The package also uses S4 classes, which may be overkill for your
> purposes.
RODBC is another, somewhat simpler, one.
There is documentation on developer.r-project.org, but my recollection is
that is was not up to date (and in particular not re finalizers). On my
TODO list is to add end-user documentation to `Writing R Extensions'.
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595