ff-interface: defcstruct

[tkunze@mvax.kgw.tu-berlin.de (Tobias Kunze)]

while trying to port code running under franz lisp on the Next i get
into troubles with mcl's ff-interface.
the main point is that i need some kind of defcstruct facility, that is,
machinery to deal with structures on the c side from within lisp:
accessors should be provided for every c-side structure field, even for
fields of embedded structures, and for elements of arrays that are
referred to via pointers.
secondly, i'm having hard times to figure out how to pass floats and 
doubles back and forth to C and Lisp; the manual has only a %copy-float
function and everything from %get/%put-byte to -long.

Do you have any clues how these things should be done in mcl?