/* Initializes |trav| for |tree|
   and selects and returns a pointer to its least-valued item.
   Returns |NULL| if |tree| contains no nodes. */
void *
bst_t_first (struct bst_traverser *trav, struct bst_table *tree)
{
  struct bst_node *x;

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

  trav->bst_table = tree;
  trav->bst_height = 0;
  trav->bst_generation = tree->bst_generation;

  x = tree->bst_root;
  if (x != NULL)
    while (x->bst_link[0] != NULL)
      {
        if (trav->bst_height >= BST_MAX_HEIGHT)
          {
            bst_balance (tree);
            return bst_t_first (trav, tree);
          }

        trav->bst_stack[trav->bst_height++] = x;
        x = x->bst_link[0];
      }
  trav->bst_node = x;

  return x != NULL ? x->bst_data : NULL;
}

