Initial revision

diff --git a/v7/src/microcode/avltree.c b/v7/src/microcode/avltree.c
new file mode 100644 (file)
index 0000000..02af61c
--- /dev/null
+++ b/v7/src/microcode/avltree.c
@@ -0,0 +1,254 @@
+/* -*-C-*-
+
+$Id: avltree.c,v 1.1 1993/11/05 00:45:09 gjr Exp $
+
+Copyright (c) 1993 Massachusetts Institute of Technology
+
+This material was developed by the Scheme project at the Massachusetts
+Institute of Technology, Department of Electrical Engineering and
+Computer Science.  Permission to copy this software, to redistribute
+it, and to use it for any purpose is granted, subject to the following
+restrictions and understandings.
+
+1. Any copy made of this software must include this copyright notice
+in full.
+
+2. Users of this software agree to make their best efforts (a) to
+return to the MIT Scheme project any improvements or extensions that
+they make, so that these may be included in future releases; and (b)
+to inform MIT of noteworthy uses of this software.
+
+3. All materials developed as a consequence of the use of this
+software shall duly acknowledge such use, in accordance with the usual
+standards of acknowledging credit in academic research.
+
+4. MIT has made no warrantee or representation that the operation of
+this software will be error-free, and MIT is under no obligation to
+provide any services, by way of maintenance, update, or otherwise.
+
+5. In conjunction with products arising from the use of this material,
+there shall be no use of the name of the Massachusetts Institute of
+Technology nor of any adaptation thereof in any advertising,
+promotional, or sales literature without prior written consent from
+MIT in each case. */
+
+/* This file contains the code for a simple AVL tree library.
+   It is used by the MIT Scheme microcode to quickly map
+   names to indices into various tables.
+ */
+
+#include "avltree.h"
+
+#ifndef NULL
+# define NULL ((PTR) 0)
+#endif
+
+char * tree_error_message = ((char *) NULL);
+char * tree_error_noise   = ((char *) NULL);
+
+static void
+DEFUN (tree_error, (message, noise), char * message AND char * noise)
+{
+  tree_error_message = message;
+  tree_error_noise   = noise;
+  return;
+}
+\f
+/* AVL trees.  o(log n) lookup, insert (and delete, not implemented here).
+   AVL condition: for every node
+     abs (height (node.left) - height (node.right)) < 2
+   This guarantees that the least-balanced AVL tree has Fibonacci-sized
+   branches, and therefore the height is at most the log base phi of the
+   number of nodes, where phi is the golden ratio.
+   With random insertion (or when created as below),
+   they are better, approaching log base 2.
+
+   This version does not allow duplicate entries.
+ */   
+
+#define BRANCH_HEIGHT(tree)                                            \
+  (((tree) == ((tree_node) NULL)) ? 0 : (tree)->height)
+
+#ifndef MAX
+#  define MAX(a,b) (((a) >= (b)) ? (a) : (b))
+#endif
+
+static void
+DEFUN (update_height, (tree), tree_node tree)
+{
+  tree->height = (1 + (MAX ((BRANCH_HEIGHT (tree->left)),
+                           (BRANCH_HEIGHT (tree->rite)))));
+  return;
+}
+
+static tree_node
+DEFUN (leaf_make, (name, value),
+       char * name AND unsigned long value)
+{
+  extern PTR EXFUN (malloc, (unsigned long));
+  tree_node leaf = ((tree_node) (malloc (sizeof (struct tree_node_s))));
+
+  if (leaf == ((tree_node) NULL))
+  {
+    tree_error ("leaf_make: malloc failed.\n", NULL);
+    return (leaf);
+  }
+  leaf->name = name;
+  leaf->value = value;
+  leaf->height = 1;
+  leaf->left = ((tree_node) NULL);
+  leaf->rite = ((tree_node) NULL);
+  return (leaf);
+}
+\f
+static tree_node
+DEFUN (rotate_left, (tree), tree_node tree)
+{
+  tree_node rite = tree->rite;
+  tree_node beta = rite->left;
+  tree->rite = beta;
+  rite->left = tree;
+  update_height (tree);
+  update_height (rite);
+  return (rite);
+}
+
+static tree_node
+DEFUN (rotate_rite, (tree), tree_node tree)
+{
+  tree_node left = tree->left;
+  tree_node beta = left->rite;
+  tree->left = beta;
+  left->rite = tree;
+  update_height (tree);
+  update_height (left);
+  return (left);
+}
+
+static tree_node
+DEFUN (rebalance_left, (tree), tree_node tree)
+{
+  if ((1 + (BRANCH_HEIGHT (tree->rite))) >= (BRANCH_HEIGHT (tree->left)))
+  {
+    update_height (tree);
+    return (tree);
+  }
+  else
+  {
+    tree_node q = tree->left;
+    if ((BRANCH_HEIGHT (q->rite)) > (BRANCH_HEIGHT (q->left)))
+      tree->left = (rotate_left (q));
+    return (rotate_rite (tree));
+  }
+}
+
+static tree_node
+DEFUN (rebalance_rite, (tree), tree_node tree)
+{
+  if ((1 + (BRANCH_HEIGHT (tree->left))) >= (BRANCH_HEIGHT (tree->rite)))
+  {
+    update_height (tree);
+    return (tree);
+  }
+  else
+  {
+    tree_node q = tree->rite;
+    if ((BRANCH_HEIGHT (q->left)) > (BRANCH_HEIGHT (q->rite)))
+      tree->rite = (rotate_rite (q));
+    return (rotate_left (tree));
+  }
+}
+\f
+tree_node
+DEFUN (tree_insert, (tree, name, value),
+       tree_node tree
+       AND char * name
+       AND unsigned long value)
+{
+  if (tree == ((tree_node) NULL))
+    return (leaf_make (name, value));
+  switch (strcmp_ci (name, tree->name))
+  {
+    case 0:
+      tree_error ("tree_insert: Duplicate entry %s.\n", name);
+      return (tree);
+      
+    case -1:
+    {
+      /* To the left */
+      tree->left = (tree_insert (tree->left, name, value));
+      return (rebalance_left (tree));
+    }
+
+    case 1:
+    {
+      /* To the right */
+      tree->rite = (tree_insert (tree->rite, name, value));
+      return (rebalance_rite (tree));
+    }
+  }
+}
+
+tree_node
+DEFUN (tree_lookup, (tree, name), tree_node tree AND char * name)
+{
+  while (tree != ((tree_node) NULL))
+    switch (strcmp_ci (name, tree->name))
+    {
+      case 0:
+       return (tree);
+
+      case -1:
+       tree = tree->left;
+       break;
+
+      case 1:
+       tree = tree->rite;
+       break;
+    }
+  return (tree);
+}
+\f
+tree_node
+DEFUN (tree_build, (high, names, value),
+       unsigned long high AND char ** names AND unsigned long value)
+{
+  static long bias = 0;
+
+  if (high > 1)
+  {
+    tree_node tree;
+    long middle = (high / 2);
+    long next;
+
+    if ((high & 1) == 0)
+    {
+      middle -= bias;
+      bias = (1 - bias);
+    }
+    next = (middle + 1);
+    tree = (leaf_make (names[middle], (value + middle)));
+    tree->left = (tree_build (middle, names, value));
+    tree->rite = (tree_build ((high - next), &names[next], (value + next)));
+    update_height (tree);
+    return (tree);
+  }
+  else if (high == 1)
+    return (leaf_make (* names, value));
+  else
+    return ((tree_node) NULL);
+}
+
+void
+DEFUN (tree_free, (tree), tree_node tree)
+{
+  extern void EXFUN (free, (PTR));
+
+  if (tree != ((tree_node) NULL))
+  {
+    tree_free (tree->left);
+    tree_free (tree->rite);
+    free (tree);
+  }
+  return;
+}

diff --git a/v7/src/microcode/avltree.h b/v7/src/microcode/avltree.h
new file mode 100644 (file)
index 0000000..d1e0afa
--- /dev/null
+++ b/v7/src/microcode/avltree.h
@@ -0,0 +1,60 @@
+/* -*-C-*-
+
+$Id: avltree.h,v 1.1 1993/11/05 00:45:18 gjr Exp $
+
+Copyright (c) 1993 Massachusetts Institute of Technology
+
+This material was developed by the Scheme project at the Massachusetts
+Institute of Technology, Department of Electrical Engineering and
+Computer Science.  Permission to copy this software, to redistribute
+it, and to use it for any purpose is granted, subject to the following
+restrictions and understandings.
+
+1. Any copy made of this software must include this copyright notice
+in full.
+
+2. Users of this software agree to make their best efforts (a) to
+return to the MIT Scheme project any improvements or extensions that
+they make, so that these may be included in future releases; and (b)
+to inform MIT of noteworthy uses of this software.
+
+3. All materials developed as a consequence of the use of this
+software shall duly acknowledge such use, in accordance with the usual
+standards of acknowledging credit in academic research.
+
+4. MIT has made no warrantee or representation that the operation of
+this software will be error-free, and MIT is under no obligation to
+provide any services, by way of maintenance, update, or otherwise.
+
+5. In conjunction with products arising from the use of this material,
+there shall be no use of the name of the Massachusetts Institute of
+Technology nor of any adaptation thereof in any advertising,
+promotional, or sales literature without prior written consent from
+MIT in each case. */
+
+/* This file contains external declarations for a simple
+   AVL tree library.
+   It is used by the MIT Scheme microcode to quickly map
+   names to indices into various tables.
+ */
+
+#include "ansidecl.h"
+
+extern char * tree_error_message;
+extern char * tree_error_noise;
+
+typedef struct tree_node_s * tree_node;
+
+struct tree_node_s
+{
+  int height;
+  tree_node left;
+  tree_node rite;
+  char * name;
+  unsigned long value;
+};
+
+extern tree_node EXFUN (tree_build, (unsigned long, char **, unsigned long));
+extern tree_node EXFUN (tree_lookup, (tree_node, char *));
+extern tree_node EXFUN (tree_insert, (tree_node, char *, unsigned long));
+extern void EXFUN (tree_free, (tree_node));