R devel - Mar 2005 - Can crc32() assume to be available at the C level?

Dear R-develers,

Antoine Lucas suggested extending my small digest package (which provides md5
and sha-1 digests of R objects, which it are serialized if needed) with a
crc32 function, and provided a fairly complete patch.

We are now wondering if we should play it safe and bundle crc32.c (plus
utils) in the digest sources (as I do with md5 and sha1), or if we can assume
that crc32 is present on all R platforms thanks to zlib. 

Is that the case?  If so, is it a good idea to use it even though it doesn't
appear in the header files?  Or should we package "our" copy?

Thanks in advance for any advice, Dirk

-- 
Better to have an approximate answer to the right question than a precise 
answer to the wrong question.  --  John Tukey as quoted by John Chambers

On Tue, 1 Mar 2005, Dirk Eddelbuettel wrote:
> Antoine Lucas suggested extending my small digest package (which provides
md5
> and sha-1 digests of R objects, which it are serialized if needed) with a
> crc32 function, and provided a fairly complete patch.
>
> We are now wondering if we should play it safe and bundle crc32.c (plus
> utils) in the digest sources (as I do with md5 and sha1), or if we can
assume
> that crc32 is present on all R platforms thanks to zlib.
>
> Is that the case?  If so, is it a good idea to use it even though it
doesn't
> appear in the header files?  Or should we package "our" copy?
It is present, but with --with-zlib options it could be in an external 
library and hence not exported by R.bin/libR.so. So I don't think you can 
rely on finding it.

-- 
Brian D. Ripley,                  ripley@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