From 6bc35c5ca0c00893f383dec89367d6dd4c91e596 Mon Sep 17 00:00:00 2001
From: Richard Brooksby <rb@ravenbrook.com>
Date: Fri, 21 Feb 2014 11:33:56 +0000
Subject: [PATCH] Generalising splayrotate operations into treerotates.

Copied from Perforce
 Change: 184431
 ServerID: perforce.ravenbrook.com
---
 mps/code/splay.c | 62 ++++--------------------------------------------
 mps/code/tree.c  | 45 +++++++++++++++++++++++++++++++++++
 mps/code/tree.h  | 11 +++++----
 3 files changed, 56 insertions(+), 62 deletions(-)

diff --git a/mps/code/splay.c b/mps/code/splay.c
index 9217e85c981..173824f6fb2 100644
--- a/mps/code/splay.c
+++ b/mps/code/splay.c
@@ -125,62 +125,6 @@ static void SplayLinkLeft(Tree *topIO, Tree *leftIO) {
 }
 
 
-/* SplayRotateLeft -- Rotate right child edge of node
- *
- * Rotates node, right child of node, and left child of right
- * child of node, leftwards in the order stated.
- *
- * See <design/splay/#impl.rotate.left>.
- */
-
-static void SplayRotateLeft(Tree *nodeIO, SplayTree tree) {
-  Tree nodeRight;
-
-  AVER(nodeIO != NULL);
-  AVERT(Tree, *nodeIO);
-  AVERT(Tree, TreeRight(*nodeIO));
-  AVERT(SplayTree, tree);
-
-  nodeRight = TreeRight(*nodeIO);
-  TreeSetRight(*nodeIO, TreeLeft(nodeRight));
-  TreeSetLeft(nodeRight, *nodeIO);
-  *nodeIO = nodeRight;
-
-  tree->updateNode(tree, TreeLeft(nodeRight));
-  /* Don't need to update new root because we know that we will */
-  /* do either a link or an assemble next, and that will sort it */
-  /* out. */
-}
-
-
-/* SplayRotateRight -- Rotate left child edge of node
- *
- * Rotates node, left child of node, and right child of left
- * child of node, leftwards in the order stated.
- *
- * See <design/splay/#impl.rotate.right>.
- */
-
-static void SplayRotateRight(Tree *nodeIO, SplayTree tree) {
-  Tree nodeLeft;
-
-  AVER(nodeIO != NULL);
-  AVERT(Tree, *nodeIO);
-  AVERT(Tree, TreeLeft(*nodeIO));
-  AVERT(SplayTree, tree);
-
-  nodeLeft = TreeLeft(*nodeIO);
-  TreeSetLeft(*nodeIO, TreeRight(nodeLeft));
-  TreeSetRight(nodeLeft, *nodeIO);
-  *nodeIO = nodeLeft;
-
-  tree->updateNode(tree, TreeRight(nodeLeft));
-  /* Don't need to update new root because we know that we will */
-  /* do either a link or an assemble next, and that will sort it */
-  /* out. */
-}
-
-
 /* SplayAssemble -- Assemble left right and top trees into one
  *
  * We do this by moving the children of the top tree to the last and
@@ -336,7 +280,8 @@ static Bool SplaySplay(Tree *nodeReturn, SplayTree tree,
         case CompareLESS: {                  /* zig-zig */
           if (TreeLeft(topLeft) == TreeEMPTY)
             goto terminalZig;
-          SplayRotateRight(&top, tree);
+          TreeRotateRight(&top);
+          tree->updateNode(tree, TreeRight(top));
           SplayLinkRight(&top, &rightFirst);
         } break;
 
@@ -373,7 +318,8 @@ static Bool SplaySplay(Tree *nodeReturn, SplayTree tree,
         case CompareGREATER: {               /* zag-zag */
           if (TreeRight(topRight) == TreeEMPTY)
             goto terminalZag;
-          SplayRotateLeft(&top, tree);
+          TreeRotateLeft(&top);
+          tree->updateNode(tree, TreeLeft(top));
           SplayLinkLeft(&top, &leftLast);
         } break;
 
diff --git a/mps/code/tree.c b/mps/code/tree.c
index 43a3bea100c..4768645b490 100644
--- a/mps/code/tree.c
+++ b/mps/code/tree.c
@@ -162,6 +162,51 @@ void TreeTraverseMorris(Tree tree, TreeVisitor visit,
 }
 
 
+/* TreeRotateLeft -- Rotate right child edge of node
+ *
+ * Rotates node, right child of node, and left child of right
+ * child of node, leftwards in the order stated.
+ */
+
+void TreeRotateLeft(Tree *treeIO)
+{
+  Tree tree, right;
+
+  AVER(treeIO != NULL);
+  tree = *treeIO;
+  AVERT(Tree, tree);
+  right = TreeRight(tree);
+  AVERT(Tree, right);
+
+  TreeSetRight(tree, TreeLeft(right));
+  TreeSetLeft(right, tree);
+
+  *treeIO = right;
+}
+
+
+/* TreeRotateRight -- Rotate left child edge of node
+ *
+ * Rotates node, left child of node, and right child of left
+ * child of node, leftwards in the order stated.
+ */
+
+void TreeRotateRight(Tree *treeIO) {
+  Tree tree, left;
+
+  AVER(treeIO != NULL);
+  tree = *treeIO;
+  AVERT(Tree, tree);
+  left = TreeLeft(tree);
+  AVERT(Tree, left);
+
+  TreeSetLeft(*treeIO, TreeRight(left));
+  TreeSetRight(left, *treeIO);
+
+  *treeIO = left;
+}
+
+
 /* C. COPYRIGHT AND LICENSE
  *
  * Copyright (C) 2014 Ravenbrook Limited <http://www.ravenbrook.com/>.
diff --git a/mps/code/tree.h b/mps/code/tree.h
index 53913e88eb7..992ed1febd7 100644
--- a/mps/code/tree.h
+++ b/mps/code/tree.h
@@ -71,12 +71,15 @@ extern Bool TreeCheckLeaf(Tree tree);
 extern Compare TreeFind(Tree *treeReturn, Tree root,
                         TreeKey key, TreeCompare compare);
 
-Bool TreeInsert(Tree *treeReturn, Tree root, Tree node,
-                TreeKey key, TreeCompare compare);
+extern Bool TreeInsert(Tree *treeReturn, Tree root, Tree node,
+                       TreeKey key, TreeCompare compare);
 
 typedef void TreeVisitor(Tree tree, void *closureP, Size closureS);
-void TreeTraverseMorris(Tree tree, TreeVisitor visit,
-                        void *closureP, Size closureS);
+extern void TreeTraverseMorris(Tree tree, TreeVisitor visit,
+                               void *closureP, Size closureS);
+
+extern void TreeRotateLeft(Tree *nodeIO);
+extern void TreeRotateRight(Tree *nodeIO);
 
 
 #endif /* tree_h */