Re: [Chicken-users] How do I plug into (lolevel) move-memory! ?

[felix]

On Wed, 24 Sep 2003 11:56:50 -0700, Dale Jordan <address@hidden> wrote:

> I'm trying to write a procedure with the following signature:
>
> (copy-bytes! s-bv s-offs d-bv d-offs n)
>
> that copies n bytes from a source byte-vector to a destination byte- 
> vector
> with given offsets, using the move-memory! procedure in lolevel.  I can't
> figure out the right combination of parameter juggling to get pointers to
> the two blocks;  I assume one has to dereference the pointer to the
> byte-vector body, but  various things I've tried turn up with bad 
> argument
> types.  It would be nice if the code worked for both 64 and 32 bit archs.
>
> Do I have to resort to C and FFI?

Well, the canonical weay should be:

(define (copy-bytes! s-bv s-offs d-bv d-offs n)
 (move-memory!
   (make-locative s-bv s-offs)
   (make-locative d-bv d-offs)
   n) )

But, alas, MOVE-MEMORY! doesn't handle locatives, yet
(I simply forgot and will fix this right away).

In the meantime you can use the less elegant but more
efficient

(define (copy-bytes! s-bv s-offs d-bv d-offs n)
 (##sys#copy-bytes s-bv d-bv s-offs d-offs n) )

(This does not work for SRFI-4 byte-vectors, BTW)


cheers,
felix