From: Vincent Fourmond <vincent.fourmond@9online.fr>
Date: 2007-01-28T20:24:36+09:00
Subject: Communication between different C extensions


  Hello !

  A long time ago, I was bitten hard by interoperability between
different C extensions that need to access each others internals. As at
that moment I was controlling the source code of all extensions, I got
away with a (simple ?) workaround.

  Now is time for me to get bitten again. I'm currently writing a Ruby
wrapper for a C++ library providing simple symbolic calculus (and
evaluation). The extensions provides functions to apply a formula to a
great number of numbers, a bit like the following:

apply("x + y", 'x' => [1,2], 'y' => [3,4])
=> [4,6]

  I want to be able to interface that with the common libraries for
manipulating data (Narray, ruby-gsl and Dobjects, a library used by
Tioga). However, I'm not aware of any way to do this 'cleanly'. Sure, I
can hack the data structures from the headers of these extensions, but
that means breaking binary compatibility everytime a header changes -
not very much something I like.

  Is there a better way to do so ? Going through Ruby arrays isn't an
option for speed issues (very expensive to convert a double * to a VALUE
array and back to double *...). Any ideas ?

  Thanks,

	Vince

-- 
Vincent Fourmond, PhD student (not for long anymore)
http://vincent.fourmond.neuf.fr/