CamlIDL and string options.

[David Brown <caml-list@davidb.org>]

I'm trying to write a camlidl interface for a function that returns a
char *.  I want the ML result to be a string option.  If the returned
pointer is null, then return None, otherwise return the string it
points to in Some.

I can make it work, but only by writing my own c2ml routine:

value field_to_ml (one_field *_c2, camlidl_ctx _ctx)
{
  value _v1;
  value _v3;
  if ((*_c2) == NULL) {
    _v1 = Val_int(0);
  } else {
    _v3 = copy_string (*_c2);
    Begin_root(_v3)
      _v1 = camlidl_alloc_small(1, 0);
      Field(_v1, 0) = _v3;
    End_roots();
  }
  return _v1;
}

Ideally, I would like to be able to use another field to get the
length, but that function needs another argument that the interface
function gets as an argument.

--------------------------------------------------
In actuality, the function is more complicated than even this.  It
actually returns a char**.  There is a function available that returns
the number of char*'s in it.  There is another function that returns
the length of each char* (provided they aren't NULL).

The other possibility is that someone else has already written an
interface of MySQL, and I'm duplicating their effort.

Dave Brown