/* Calls |visit| for each of the nodes in |tree| in level order.
   Returns nonzero if successful, zero if out of memory. */
static int
bst_traverse_level_order (struct bst_table *tree, bst_item_func *visit)
{
  struct bst_node **queue;
  size_t head, tail;

  if (tree->bst_count == 0)
    return 1;

  queue = tree->bst_alloc->libavl_malloc (tree->bst_alloc,
                                          sizeof *queue * tree->bst_count);
  if (queue == NULL)
    return 0;

  head = tail = 0;
  queue[head++] = tree->bst_root;
  while (head != tail)
    {
      struct bst_node *cur = queue[tail++];
      visit (cur->bst_data, tree->bst_param);
      if (cur->bst_link[0] != NULL)
        queue[head++] = cur->bst_link[0];
      if (cur->bst_link[1] != NULL)
        queue[head++] = cur->bst_link[1];
    }
  tree->bst_alloc->libavl_free (tree->bst_alloc, queue);

  return 1;
}