z = (struct tavl_node *) &tree->tavl_root;
y = tree->tavl_root;
if (y != NULL)
  {
    for (q = z, p = y; ; q = p, p = p->tavl_link[dir])
      {
        int cmp = tree->tavl_compare (item, p->tavl_data, tree->tavl_param);
        if (cmp == 0)
          return &p->tavl_data;

        if (p->tavl_balance != 0)
          z = q, y = p, k = 0;
        da[k++] = dir = cmp > 0;

        if (p->tavl_tag[dir] == TAVL_THREAD)
          break;
      }
  }
else
  {
    p = z;
    dir = 0;
  }