Sorry I don't have a complete answer for you ... looks like this may
take a bit of work.

http://www.swig.org/Doc1.3/Typemaps.html#Typemaps_nn40

.... shows an example using Python.

To call your function the way you want, looks like you'll need to write
a typemap and/or helper functions to extract the Ruby array values and
populate a C array with the correct type values.  ruby.h has a bunch of
conversion macros and prototypes that will help.

Good luck!