Freeing allocated C-memory by GC (destructors)

Freeing allocated C-memory by GC (destructors)

[Oliver Bandel]

Hello,

after using some non-permanent allocating C-stuff
together with OCaml, I think about going one step further and
now have allocated memory from C represented as OCaml-variables
(in the concrete example I have married some of my C-stuff that
uses jpeglib to get information from picture-files, and
now think about representing complete picture-data as
OCaml-variables).

So, I want to have the possibility to have malloced/calloced
data avaliable in OCaml, and that the GC calls C-destructor-
functions (using free(3)) when the values are of no use anymore.


How to say the GC, which is the destructor-functions
for a variable, which has been created?

TIA,
   Oliver

RE: [Caml-list] Freeing allocated C-memory by GC (destructors)

[RABIH.ELCHAAR]

Use custom_blocks, passing the corresponding functions (mainly the finalizer)
Here is an example of random generator defined in c and wrapped in ocaml

#define Gen(v) (*((int **) Data_custom_val(v)))

static void finalize_Gen(value v)
{
  int * stream = Gen(v);
  free_Gen(stream);
}

CAMLexport struct custom_operations Gen_ops = {
  "mlfi_Gen_state",
  //custom_finalize_default,
  &finalize_Gen,
  custom_compare_default,
  custom_hash_default,
  custom_serialize_default,
  custom_deserialize_default
};


CAMLprim value Gen_make(value init_seed, value rng_type, value rng_parameter, ...)
{
  CAMLparam5(init_seed,rng_type,rng_parameter,...);
  CAMLlocal1(t);
  int *stream;
  unsigned long int seed; 
  int rngtype;
  int rngparameter;

  seed = Unsigned_long_val(init_seed);

  rngtype = getRngType(rng_type);
  rngparameter = getRngParameter(rng_parameter);

  /* we create here the custom block, with the correct free operator */  
  t = alloc_custom(&Gen_ops, sizeof(int *), 0, 1);
  stream = init_Gen(rngtype,...,seed,rngparameter);
  Gen(t) = stream;

  CAMLreturn(t);
}

-----Message d'origine-----
De : caml-list-bounces@yquem.inria.fr [mailto:caml-list-bounces@yquem.inria.fr] De la part de Oliver Bandel
Envoyé : mercredi 23 janvier 2008 17:46
À : caml-list@inria.fr
Objet : [Caml-list] Freeing allocated C-memory by GC (destructors)

Hello,

after using some non-permanent allocating C-stuff
together with OCaml, I think about going one step further and
now have allocated memory from C represented as OCaml-variables
(in the concrete example I have married some of my C-stuff that
uses jpeglib to get information from picture-files, and
now think about representing complete picture-data as
OCaml-variables).

So, I want to have the possibility to have malloced/calloced
data avaliable in OCaml, and that the GC calls C-destructor-
functions (using free(3)) when the values are of no use anymore.


How to say the GC, which is the destructor-functions
for a variable, which has been created?

TIA,
   Oliver

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