/* Converts |tree|, which must be in the shape of a vine, into a balanced
   tree. */
static void
vine_to_tree (struct tbst_table *tree)
{
  unsigned long vine;   /* Number of nodes in main vine. */
  unsigned long leaves; /* Nodes in incomplete bottom level, if any. */
  int height;           /* Height of produced balanced tree. */

  leaves = tree->tbst_count + 1;
  for (;;)
    {
      unsigned long next = leaves & (leaves - 1);
      if (next == 0)
        break;
      leaves = next;
    }
  leaves = tree->tbst_count + 1 - leaves;

  compress ((struct tbst_node *) &tree->tbst_root, 0, leaves);

  vine = tree->tbst_count - leaves;
  height = 1 + (leaves > 0);
  if (vine > 1)
    {
      unsigned long nonleaves = vine / 2;
      leaves /= 2;
      if (leaves > nonleaves)
        {
          leaves = nonleaves;
          nonleaves = 0;
        }
      else
        nonleaves -= leaves;

      compress ((struct tbst_node *) &tree->tbst_root, leaves, nonleaves);
      vine /= 2;
      height++;
    }
  while (vine > 1)
    {
      compress ((struct tbst_node *) &tree->tbst_root, vine / 2, 0);
      vine /= 2;
      height++;
    }
}