/* Search |tree| for an item matching |item|, and return it if found.
   Otherwise return |NULL|. */
void *
rtbst_find (const struct rtbst_table *tree, const void *item)
{
  const struct rtbst_node *p;
  int dir;

  assert (tree != NULL && item != NULL);

  if (tree->rtbst_root == NULL)
    return NULL;

  for (p = tree->rtbst_root; ; p = p->rtbst_link[dir])
    {
      int cmp = tree->rtbst_compare (item, p->rtbst_data, tree->rtbst_param);
      if (cmp == 0)
        return p->rtbst_data;
      dir = cmp > 0;

      if (dir == 0)
        {
          if (p->rtbst_link[0] == NULL)
            return NULL;
        }
      else /* |dir == 1| */
        {
          if (p->rtbst_rtag == RTBST_THREAD)
            return NULL;
        }
    }
}