gistfile1.txt

CAMLprim value caml_ba_overlap(value va, value vb)
{
  CAMLparam2 (va, vb);
  CAMLlocal1 (res);

  struct caml_ba_array * a = Caml_ba_array_val(va);
  struct caml_ba_array * b = Caml_ba_array_val(vb);
  void *src_a = a->data;
  void *src_b = b->data;
  intnat len;
  intnat a_bytes;
  intnat b_bytes;
  intnat dim_a[CAML_BA_MAX_NUM_DIMS];
  intnat dim_b[CAML_BA_MAX_NUM_DIMS];
  intnat offset;

  a_bytes = caml_ba_num_elts(a) * caml_ba_element_size[a->flags & CAML_BA_KIND_MASK];
  b_bytes = caml_ba_num_elts(b) * caml_ba_element_size[b->flags & CAML_BA_KIND_MASK];

  if (a->num_dims != b->num_dims)
    caml_invalid_argument("Bigarray.overlap: dimensions mistmatch");

  // [--b--[--]--a--] || [--b--[-a-]--]
  if (a_src >= b_src && a_src < b_src + b_bytes)
    {
      len = MIN(a_bytes, b_bytes) - (a_src - b_src);
      memset(a_dim, 0, sizeof(intnat) * CAML_BA_MAX_NUM_DIMS);
      offset = b_src + (a_src - b_src);
      for (i = b->num_dims - 1; i >= 0; i--)
        {
          b_dim[i] = offset % b->dims[i];
          offset = offset / b->dims[i];
        }
    }
  // [--a--[--]--b--] || [--[-b-]--a--]
  else if (b_src >= a_src && b_src < a_src + a_bytes)
    {
      len = MIN(a_bytes, b_bytes) - (b_src - a_src);
      memset(b_dim, 0, sizeof(intnat) * CAML_BA_MAX_NUM_DIMS);
      offset = a_src + (b_src - a_src);
      for (i = a->num_dims; i >= 0; i--)
        {
          a_dim[i] = offset % a->dims[i];
          offset = offset / a->dims[i];
        }
    }
}