Re: Interfacing C procedure using an array as parameter ?

[Xavier Leroy <Xavier.Leroy@inria.fr>]

> 	This is the first time I interface C/OCaml and also I have
> 	a problem : How do I use a parameter which is a pointer
> 	on the beginning of an integer array ?

To get you started, here are functions to convert between a C integer
array and a Caml integer array. (Warning: untested code ahead.)

value c_intarray_to_caml_intarray(int * carray, unsigned int nelts)
{
  value mlarray;
  int i;

  mlarray = nelts < Max_young_wosize ? alloc(nelts, 0) : alloc_shr(nelts, 0);
  for (i = 0; i < nelts; i++) Field(mlarray, i) = Val_int(carray[i]);
  return mlarray;
}

int caml_intarray_to_c_intarray(value mlarray,
                                int ** carray /*out parameter*/,
                                unsigned int * nelts /*out parameter*/)
{
  unsigned int len;
  int * p;
  int i;

  len = Wosize_val(mlarray);
  p = malloc(len * sizeof(int));
  if (p == NULL) return -1;
  for (i = 0; i < len; i++) p[i] = Int_val(Field(mlarray, i));
  *carray = p;
  *nelts = len;
  return 0;
}

Hope this helps,

- Xavier Leroy