[gambit-list] Returning a byte array from C

Mikael mikael.rcv at gmail.com
Thu Sep 26 10:36:32 EDT 2013

Cool! Ahh, this is because with ___FIX() it's implicit that the passed
value will fit in a fixnum whereas with (c-lambda ([args]) int code) needs
a conditional for if the return value would be a bignum.

Beyond this, can it ever be faster with regard to use (##c-code code) than
(c-lambda (scheme-object:s) scheme-object code)?

Vijay: Feel free to document what you got from this on the wiki - this is
like the most essential stuff ever so it deserves a place there.

2013/9/26 Marc Feeley <feeley at iro.umontreal.ca>

> On 2013-09-26, at 12:21 AM, Vijay Mathew <vijay.the.lisper at gmail.com>
> wrote:
> > Thanks again for all the great feedback!
> >
> > I think the call to ____FIX() is not required if Scheme code access the
> C function through a declaration like this:
> >
> > (define read-bytes (c-lambda (int unsigned-int scheme-object) int
> "read_bytes"))
> >
> > Is that correct?
> That is correct.  However, using ___FIX() is faster for converting a C
> integer to a Scheme fixnum.  And ___INT() is faster for converting a Scheme
> fixnum to a C integer. So better performance is obtained with:
> (define read-bytes
>   (c-lambda (scheme-object scheme-object scheme-object)
>             scheme-object
>    "___result = ___FIX(read
> (___INT(___arg1),___BODY(___arg3),___INT(___arg2));"))
> Marc
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