Re: [Rd] external pointers

From: Prof Brian Ripley <>
Date: Mon 12 Dec 2005 - 22:05:02 GMT

On Mon, 12 Dec 2005, Byron Ellis wrote:

> There's also Luke's own site, in particular
> ~luke/R/weakfinex.html

Hmm, that _is_ a link on the page I pointed you to, under its actual subject, weak references.

> On Dec 12, 2005, at 12:16 AM, Prof Brian Ripley wrote:
>> 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, 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,        
Professor of Applied Statistics,
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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