13.5.3 Starting at a Found Node

To start from a particular item, we search for it in the tree. If it exists then we initialize the traverser to it. Otherwise, we initialize the traverser to the null item and return a null pointer. There are no surprises here.

507. <PBST traverser search initializer 507> =
void *
pbst_t_find (struct pbst_traverser *trav, struct pbst_table *tree, void *item) 
{
  struct pbst_node *p;
  int dir;

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

  trav->pbst_table = tree;
  for (p = tree->pbst_root; p != NULL; p = p->pbst_link[dir]) 
    {
      int cmp = tree->pbst_compare (item, p->pbst_data, tree->pbst_param);
      if (cmp == 0) 
        {
          trav->pbst_node = p;
          return p->pbst_data;
        }

      dir = cmp > 0;
    }

  trav->pbst_node = NULL;
  return NULL;
}

This code is included in 504 and 548.