4.9.3.4 Starting at a Found Node

Sometimes it is convenient to begin a traversal at a particular item in a tree. This function works in the same was as bst_find(), but records parent pointers in the traverser structure as it descends the tree.

67. <BST traverser search initializer 67> =
void *
bst_t_find (struct bst_traverser *trav, struct bst_table *tree, void *item) 
{
  struct bst_node *p, *q;

  assert (trav != NULL && tree != NULL && item != NULL);
  trav->bst_table = tree;
  trav->bst_height = 0;
  trav->bst_generation = tree->bst_generation;
  for (p = tree->bst_root; p != NULL; p = q) 
    {
      int cmp = tree->bst_compare (item, p->bst_data, tree->bst_param);

      if (cmp < 0) 
        q = p->bst_link[0];
      else if (cmp > 0) 
        q = p->bst_link[1];
      else /* cmp == 0 */ 
        {
          trav->bst_node = p;
          return p->bst_data;
        }

      if (trav->bst_height >= BST_MAX_HEIGHT) 
        {
          bst_balance (trav->bst_table);
          return bst_t_find (trav, tree, item);
        }
      trav->bst_stack[trav->bst_height++] = p;
    }

  trav->bst_height = 0;
  trav->bst_node = NULL;
  return NULL;
}

This code is included in 63.