[cffi-devel] Static vectors suitable for FFI

[Tamas K Papp]

On Thu, 07 May 2009 09:48:08 +0200, Stelian Ionescu wrote:

> On Thu, 2009-05-07 at 11:00 +0900, John Fremlin wrote:
>> Stelian Ionescu <stelian.ionescu-zeus at poste.it> writes:
>> 
>> > Attached is an implementation for SBCL. make-static-vector only
>> > allocates instances of (simple-array (unsigned-byte 8) (*)) but that
>> > can be extended to other unboxed arrays.
>> > The current sharable vector interface doesn't work very well because
>> > it doesn't allow me for instance to pin a list of vectors, but only a
>> > single vector at a time. Also, I'd prefer to avoid pinning at all
>> > given how it interferes with the GC.
>> 
>> Thanks Stelian!
>> 
>> This would be really useful as the pinning business with
>> shareable-byte-vectors is a real nuisance.
>> 
>> If the current shareable-byte-vector interface is going to be reworked
>> can I suggest that we allow (at least) simple-array
>> single-float/double-float as well? Why not just allow all unboxed array
> 
> That can be easily done.
> 
> 
>> types the underlying Lisp supports? . . . Or a limited sensible subset?
> 
> I think that we should allow all types supported by the underlying
> implementation but specify in the docs that very few are portable:
> (probably, I haven't yet checked) only bit, [un]signed-byte-{8,16,32,64}
> and single-float are portable
> 
> 
>> Having portable unboxed C-sharable float arrays would be great for our
>> numeric work.
> 
> Now we only need to see if the trick of "manually" creating unboxed
> arrays works on other implementations: CMUCL, CCL, Clisp, ECL, ...
> Allegro and Lispworks already support this with make-array's :ALLOCATION
> key arg
> 
> 
>> I should be very happy to make the Allegro CL interface.
> 
> Thanks. See if Allegro has native functions for bit-bashing, otherwise
> implement {fill,copy}-foreign-memory in terms of memset/memcpy.

Thanks Stefan,

Very neat work.  This would indeed help a lot with numeric work.

Question: is the need to manually free the object a must?  Could we
perhaps have an argument to make-static-vector that tells it to
register a finalizer when needed?

Tamas