[Chicken-users] Structs

[Felix Winkelmann]

Hi!

>Now, I don't understand how to construct an API for zlib because I 
>don't know
>how to make a z_stream structure that can be updated both in the 
scheme >side
>and the C side, and have garbage collection not foul anything up.

In this case I would create a number of foreign-lambda*s
that access the slots:

(define-foreign-type z_stream (pointer "z_stream"))

(define make-z_stream
  (foreign-lambda* z_stream ()
    "return((z_stream *)malloc(sizeof(z_stream)));") )

(define z_stream-next_in
  (foreign-lambda* c-pointer ([z_stream p])
    "return(p->next_in);") )

(define z_stream-next_in-set!
  (foreign-lambda* void ([z_stream p] [pointer x])
    "p->next_in = x;") )

...

I can send you a quick-and-dirty macro that does most
of the work. Might need one or two days (I don't have it
here on my machine at work).


cheers,
felix