/* Searches for |item| in |tree|.
   If found, initializes |trav| to the item found and returns the item
   as well.
   If there is no matching item, initializes |trav| to the null item
   and returns |NULL|. */
void *
avl_t_find (struct avl_traverser *trav, struct avl_table *tree, void *item)
{
  struct avl_node *p, *q;

  assert (trav != NULL && tree != NULL && item != NULL);
  trav->avl_table = tree;
  trav->avl_height = 0;
  trav->avl_generation = tree->avl_generation;
  for (p = tree->avl_root; p != NULL; p = q)
    {
      int cmp = tree->avl_compare (item, p->avl_data, tree->avl_param);

      if (cmp < 0)
        q = p->avl_link[0];
      else if (cmp > 0)
        q = p->avl_link[1];
      else /* |cmp == 0| */
        {
          trav->avl_node = p;
          return p->avl_data;
        }

      assert (trav->avl_height < AVL_MAX_HEIGHT);
      trav->avl_stack[trav->avl_height++] = p;
    }

  trav->avl_height = 0;
  trav->avl_node = NULL;
  return NULL;
}