added TREE_WANT_BOUNDARY for finding the first/last node

diff --git a/lib/redblack.h b/lib/redblack.h
index 764ca104c6ed9973da37f05ba90d743143401062..7658f25f6868a1b09b25d08c03f7e69c5eac9e1d 100644 (file)
--- a/lib/redblack.h
+++ b/lib/redblack.h
@@ -68,6 +68,8 @@
  *                     Implies TREE_DUPLICATES.
  *  TREE_WANT_SEARCH   node *search(key) -- find the node with the specified
  *                     or, if it does not exist, the nearest one.
+ *  TREE_WANT_BOUNDARY node *boundary(uns direction) -- finds smallest
+ *                     (direction==0) or largest (direction==1) node.
  *  TREE_WANT_ADJACENT node *adjacent(node *, uns direction) -- finds next
  *                     (direction==1) or previous (direction==0) node.
  *  TREE_WANT_NEW      node *new(key) -- create new node with given key.
@@ -410,6 +412,22 @@ STATIC P(node) * P(find) (T *t, TREE_KEY_DECL)
 }
 #endif
 
+#ifdef TREE_WANT_BOUNDARY
+STATIC P(node) * P(boundary) (T *t, uns direction)
+{
+       P(bucket) *n = t->root, *ns;
+       if (!n)
+               return NULL;
+       else
+       {
+               uns son = !!direction;
+               while ((ns = P(tree_son) (n, son)))
+                       n = ns;
+               return &n->n;
+       }
+}
+#endif
+
 #ifdef TREE_STORE_PARENT
 STATIC P(node) * P(adjacent) (P(node) *start, uns direction)
 {
@@ -966,6 +984,7 @@ do                                                                                  \
 #undef TREE_WANT_FIND
 #undef TREE_WANT_FIND_NEXT
 #undef TREE_WANT_SEARCH
+#undef TREE_WANT_BOUNDARY
 #undef TREE_WANT_ADJACENT
 #undef TREE_WANT_NEW
 #undef TREE_WANT_LOOKUP