480 lines
11 KiB
C
480 lines
11 KiB
C
/* A splay-tree datatype.
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Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
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Contributed by Mark Mitchell (mark@markmitchell.com).
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This file is part of GNU CC.
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GNU CC is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU CC is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU CC; see the file COPYING. If not, write to
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the Free Software Foundation, 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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/* For an easily readable description of splay-trees, see:
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Lewis, Harry R. and Denenberg, Larry. Data Structures and Their
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Algorithms. Harper-Collins, Inc. 1991. */
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#ifdef HAVE_STDLIB_H
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#include <stdlib.h>
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#endif
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#include <stdio.h>
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#include "libiberty.h"
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#include "splay-tree.h"
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static void splay_tree_delete_helper PARAMS((splay_tree,
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splay_tree_node));
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static void splay_tree_splay PARAMS((splay_tree,
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splay_tree_key));
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static splay_tree_node splay_tree_splay_helper
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PARAMS((splay_tree,
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splay_tree_key,
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splay_tree_node*,
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splay_tree_node*,
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splay_tree_node*));
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static int splay_tree_foreach_helper PARAMS((splay_tree,
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splay_tree_node,
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splay_tree_foreach_fn,
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void*));
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/* Deallocate NODE (a member of SP), and all its sub-trees. */
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static void
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splay_tree_delete_helper (sp, node)
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splay_tree sp;
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splay_tree_node node;
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{
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if (!node)
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return;
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splay_tree_delete_helper (sp, node->left);
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splay_tree_delete_helper (sp, node->right);
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if (sp->delete_key)
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(*sp->delete_key)(node->key);
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if (sp->delete_value)
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(*sp->delete_value)(node->value);
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free ((char*) node);
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}
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/* Help splay SP around KEY. PARENT and GRANDPARENT are the parent
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and grandparent, respectively, of NODE. */
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static splay_tree_node
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splay_tree_splay_helper (sp, key, node, parent, grandparent)
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splay_tree sp;
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splay_tree_key key;
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splay_tree_node *node;
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splay_tree_node *parent;
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splay_tree_node *grandparent;
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{
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splay_tree_node *next;
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splay_tree_node n;
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int comparison;
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n = *node;
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if (!n)
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return *parent;
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comparison = (*sp->comp) (key, n->key);
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if (comparison == 0)
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/* We've found the target. */
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next = 0;
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else if (comparison < 0)
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/* The target is to the left. */
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next = &n->left;
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else
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/* The target is to the right. */
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next = &n->right;
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if (next)
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{
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/* Continue down the tree. */
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n = splay_tree_splay_helper (sp, key, next, node, parent);
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/* The recursive call will change the place to which NODE
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points. */
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if (*node != n)
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return n;
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}
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if (!parent)
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/* NODE is the root. We are done. */
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return n;
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/* First, handle the case where there is no grandparent (i.e.,
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*PARENT is the root of the tree.) */
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if (!grandparent)
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{
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if (n == (*parent)->left)
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{
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*node = n->right;
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n->right = *parent;
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}
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else
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{
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*node = n->left;
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n->left = *parent;
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}
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*parent = n;
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return n;
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}
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/* Next handle the cases where both N and *PARENT are left children,
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or where both are right children. */
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if (n == (*parent)->left && *parent == (*grandparent)->left)
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{
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splay_tree_node p = *parent;
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(*grandparent)->left = p->right;
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p->right = *grandparent;
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p->left = n->right;
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n->right = p;
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*grandparent = n;
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return n;
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}
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else if (n == (*parent)->right && *parent == (*grandparent)->right)
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{
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splay_tree_node p = *parent;
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(*grandparent)->right = p->left;
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p->left = *grandparent;
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p->right = n->left;
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n->left = p;
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*grandparent = n;
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return n;
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}
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/* Finally, deal with the case where N is a left child, but *PARENT
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is a right child, or vice versa. */
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if (n == (*parent)->left)
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{
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(*parent)->left = n->right;
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n->right = *parent;
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(*grandparent)->right = n->left;
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n->left = *grandparent;
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*grandparent = n;
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return n;
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}
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else
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{
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(*parent)->right = n->left;
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n->left = *parent;
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(*grandparent)->left = n->right;
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n->right = *grandparent;
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*grandparent = n;
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return n;
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}
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}
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/* Splay SP around KEY. */
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static void
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splay_tree_splay (sp, key)
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splay_tree sp;
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splay_tree_key key;
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{
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if (sp->root == 0)
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return;
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splay_tree_splay_helper (sp, key, &sp->root,
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/*grandparent=*/0, /*parent=*/0);
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}
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/* Call FN, passing it the DATA, for every node below NODE, all of
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which are from SP, following an in-order traversal. If FN every
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returns a non-zero value, the iteration ceases immediately, and the
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value is returned. Otherwise, this function returns 0. */
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static int
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splay_tree_foreach_helper (sp, node, fn, data)
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splay_tree sp;
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splay_tree_node node;
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splay_tree_foreach_fn fn;
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void* data;
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{
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int val;
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if (!node)
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return 0;
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val = splay_tree_foreach_helper (sp, node->left, fn, data);
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if (val)
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return val;
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val = (*fn)(node, data);
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if (val)
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return val;
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return splay_tree_foreach_helper (sp, node->right, fn, data);
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}
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/* Allocate a new splay tree, using COMPARE_FN to compare nodes,
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DELETE_KEY_FN to deallocate keys, and DELETE_VALUE_FN to deallocate
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values. */
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splay_tree
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splay_tree_new (compare_fn, delete_key_fn, delete_value_fn)
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splay_tree_compare_fn compare_fn;
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splay_tree_delete_key_fn delete_key_fn;
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splay_tree_delete_value_fn delete_value_fn;
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{
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splay_tree sp = (splay_tree) xmalloc (sizeof (struct splay_tree_s));
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sp->root = 0;
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sp->comp = compare_fn;
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sp->delete_key = delete_key_fn;
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sp->delete_value = delete_value_fn;
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return sp;
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}
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/* Deallocate SP. */
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void
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splay_tree_delete (sp)
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splay_tree sp;
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{
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splay_tree_delete_helper (sp, sp->root);
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free ((char*) sp);
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}
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/* Insert a new node (associating KEY with DATA) into SP. If a
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previous node with the indicated KEY exists, its data is replaced
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with the new value. Returns the new node. */
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splay_tree_node
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splay_tree_insert (sp, key, value)
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splay_tree sp;
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splay_tree_key key;
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splay_tree_value value;
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{
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int comparison = 0;
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splay_tree_splay (sp, key);
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if (sp->root)
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comparison = (*sp->comp)(sp->root->key, key);
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if (sp->root && comparison == 0)
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{
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/* If the root of the tree already has the indicated KEY, just
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replace the value with VALUE. */
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if (sp->delete_value)
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(*sp->delete_value)(sp->root->value);
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sp->root->value = value;
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}
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else
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{
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/* Create a new node, and insert it at the root. */
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splay_tree_node node;
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node = (splay_tree_node) xmalloc (sizeof (struct splay_tree_node_s));
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node->key = key;
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node->value = value;
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if (!sp->root)
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node->left = node->right = 0;
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else if (comparison < 0)
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{
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node->left = sp->root;
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node->right = node->left->right;
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node->left->right = 0;
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}
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else
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{
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node->right = sp->root;
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node->left = node->right->left;
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node->right->left = 0;
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}
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sp->root = node;
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}
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return sp->root;
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}
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/* Remove KEY from SP. It is not an error if it did not exist. */
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void
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splay_tree_remove (sp, key)
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splay_tree sp;
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splay_tree_key key;
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{
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splay_tree_splay (sp, key);
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if (sp->root && (*sp->comp) (sp->root->key, key) == 0)
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{
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splay_tree_node left, right;
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left = sp->root->left;
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right = sp->root->right;
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/* Delete the root node itself. */
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if (sp->delete_value)
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(*sp->delete_value) (sp->root->value);
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free (sp->root);
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/* One of the children is now the root. Doesn't matter much
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which, so long as we preserve the properties of the tree. */
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if (left)
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{
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sp->root = left;
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/* If there was a right child as well, hang it off the
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right-most leaf of the left child. */
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if (right)
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{
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while (left->right)
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left = left->right;
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left->right = right;
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}
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}
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else
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sp->root = right;
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}
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}
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/* Lookup KEY in SP, returning VALUE if present, and NULL
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otherwise. */
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splay_tree_node
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splay_tree_lookup (sp, key)
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splay_tree sp;
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splay_tree_key key;
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{
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splay_tree_splay (sp, key);
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if (sp->root && (*sp->comp)(sp->root->key, key) == 0)
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return sp->root;
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else
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return 0;
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}
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/* Return the immediate predecessor KEY, or NULL if there is no
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predecessor. KEY need not be present in the tree. */
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splay_tree_node
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splay_tree_predecessor (sp, key)
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splay_tree sp;
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splay_tree_key key;
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{
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int comparison;
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splay_tree_node node;
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/* If the tree is empty, there is certainly no predecessor. */
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if (!sp->root)
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return NULL;
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/* Splay the tree around KEY. That will leave either the KEY
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itself, its predecessor, or its successor at the root. */
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splay_tree_splay (sp, key);
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comparison = (*sp->comp)(sp->root->key, key);
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/* If the predecessor is at the root, just return it. */
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if (comparison < 0)
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return sp->root;
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/* Otherwise, find the leftmost element of the right subtree. */
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node = sp->root->left;
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if (node)
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while (node->right)
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node = node->right;
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return node;
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}
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/* Return the immediate successor KEY, or NULL if there is no
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predecessor. KEY need not be present in the tree. */
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splay_tree_node
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splay_tree_successor (sp, key)
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splay_tree sp;
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splay_tree_key key;
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{
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int comparison;
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splay_tree_node node;
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/* If the tree is empty, there is certainly no predecessor. */
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if (!sp->root)
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return NULL;
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/* Splay the tree around KEY. That will leave either the KEY
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itself, its predecessor, or its successor at the root. */
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splay_tree_splay (sp, key);
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comparison = (*sp->comp)(sp->root->key, key);
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/* If the successor is at the root, just return it. */
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if (comparison > 0)
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return sp->root;
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/* Otherwise, find the rightmost element of the left subtree. */
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node = sp->root->right;
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if (node)
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while (node->left)
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node = node->left;
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return node;
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}
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/* Call FN, passing it the DATA, for every node in SP, following an
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in-order traversal. If FN every returns a non-zero value, the
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iteration ceases immediately, and the value is returned.
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Otherwise, this function returns 0. */
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int
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splay_tree_foreach (sp, fn, data)
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splay_tree sp;
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splay_tree_foreach_fn fn;
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void *data;
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{
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return splay_tree_foreach_helper (sp, sp->root, fn, data);
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}
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/* Splay-tree comparison function, treating the keys as ints. */
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int
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splay_tree_compare_ints (k1, k2)
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splay_tree_key k1;
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splay_tree_key k2;
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{
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if ((int) k1 < (int) k2)
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return -1;
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else if ((int) k1 > (int) k2)
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return 1;
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else
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return 0;
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}
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/* Splay-tree comparison function, treating the keys as pointers. */
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int
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splay_tree_compare_pointers (k1, k2)
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splay_tree_key k1;
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splay_tree_key k2;
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{
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if ((char*) k1 < (char*) k2)
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return -1;
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else if ((char*) k1 > (char*) k2)
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return 1;
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else
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return 0;
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}
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