Steel Bank Common Lisp

On Fri, 23 Sep 2005, Cyrus Harmon wrote:

> Dear sbcl-help,
>
> Forgive me if this is just a bad idea altogether, but, is it possible to take 
> an arbitrary hunk of memory and trick sbcl into thinking that it is an array? 
> Obviously, I don't want this region to be gc'ed  or moved, but if I could 
> just read/write into it, that would be nice.

The foreign function interface (called alien) makes it possible to access such 
memory, but this is not to "trick" sbcl. The manual tells you how to call malloc 
from lisp, and how to access the memory.

http://www.sbcl.org/manual/
http://www.sbcl.org/manual/Foreign-Function-Interface.html
http://www.sbcl.org/manual/Foreign-Dynamic-Allocation.html

Alternatively you can call external C functions doing this work, also explained 
in the same section of the manual.

-- 
Gisle Sælensminde, Phd student, Scientific programmer
Computational biology unit, University of Bergen, Norway
Email: gisle@...

On Fri, 23 Sep 2005, Cyrus Harmon wrote:

> Forgive me if this is just a bad idea altogether, but, is it possible to take 
> an arbitrary hunk of memory and trick sbcl into thinking that it is an array? 
> Obviously, I don't want this region to be gc'ed  or moved, but if I could 
> just read/write into it, that would be nice.

Do you need a non-movable array, or do you need to refer to external 
memory allocated by a third-party library?

In the latter case the alien interface should get you started, and in the 
first the (unsupported) SB-INT:MAKE-STATIC-VECTOR should do what you 
need.

There is no fundamental reason why it has to be unsupported: essentially 
if the interface was double-checked for sanity, some tests written, and 
possibly extended into MAKE-STATIC-ARRAY it could IMO be moved to SB-EXT.

Also, if your data is in non-lisp memory but laid out in a manner 
compatible with SBCL you might look at MAKE-STATIC-VECTOR and 
ALLOCATE-STATIC-VECTOR, and see if you can extend MAKE-ARRAY to accept eg. 
a SAP as an argument to :DISPLACED-TO.

Cheers,

  -- Nikodemus              Schemer: "Buddha is small, clean, and serious."
                   Lispnik: "Buddha is big, has hairy armpits, and laughs."