[Rd] Accessing a c-level complicated structure from R

[Scionforbai]

Hello,
R-devel seems to be the appropriated list for what I'm to ask: soory
if I'm wrong. I am a c newbie but nevertheless I am trying to 'couple'
an extern c software with R. The compiled library is actually a
stand-alone c program, which uses text file for input and output. It
uses *lots* of differents and (to me) rather complicated and nested
"struct"s to represent data for intern calculation. I want to make
this program a -shared lib to use with R.
I have (among many others) the following question: can I access from R
a c-level defined struct, as input/output of my .C called function? If
yes... how?

Any clue, manual, tutorial on c programming with R (other than R-exts
and R-ints),  and hint is greatly appreciated...
Thanks,
Scion