566 lines
15 KiB
C
566 lines
15 KiB
C
/* A splay-tree datatype.
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Copyright (C) 1998, 1999, 2000, 2001, 2004 Free Software Foundation, Inc.
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Contributed by Mark Mitchell (mark@markmitchell.com).
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Adapted for libmudflap from libiberty.
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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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In addition to the permissions in the GNU General Public License, the
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Free Software Foundation gives you unlimited permission to link the
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compiled version of this file into combinations with other programs,
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and to distribute those combinations without any restriction coming
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from the use of this file. (The General Public License restrictions
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do apply in other respects; for example, they cover modification of
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the file, and distribution when not linked into a combine
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executable.)
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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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#include <stdlib.h>
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#include <stdio.h>
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#include "splay-tree.h"
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static void splay_tree_delete_helper (splay_tree, splay_tree_node);
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static void splay_tree_splay (splay_tree, splay_tree_key);
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static splay_tree_node splay_tree_splay_helper (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 void *splay_tree_xmalloc (size_t size);
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static void splay_tree_free (void *object);
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/* Inline comparison function specialized for libmudflap's key type. */
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static inline int
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compare_uintptr_t (splay_tree_key k1, splay_tree_key k2)
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{
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if ((uintptr_t) k1 < (uintptr_t) k2)
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return -1;
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else if ((uintptr_t) k1 > (uintptr_t) 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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/* 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 (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 = compare_uintptr_t (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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/* Check whether our recursion depth is too high. Abort this search,
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and signal that a rebalance is required to continue. */
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if (sp->depth > sp->max_depth)
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{
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sp->rebalance_p = 1;
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return n;
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}
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/* Continue down the tree. */
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sp->depth ++;
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n = splay_tree_splay_helper (sp, key, next, node, parent);
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sp->depth --;
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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 || sp->rebalance_p)
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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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static int
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splay_tree_rebalance_helper1 (splay_tree_node n, void *array_ptr)
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{
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splay_tree_node **p = array_ptr;
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*(*p) = n;
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(*p)++;
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return 0;
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}
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static splay_tree_node
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splay_tree_rebalance_helper2 (splay_tree_node * array, unsigned low,
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unsigned high)
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{
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unsigned middle = low + (high - low) / 2;
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splay_tree_node n = array[middle];
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/* Note that since we're producing a balanced binary tree, it is not a problem
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that this function is recursive. */
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if (low + 1 <= middle)
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n->left = splay_tree_rebalance_helper2 (array, low, middle - 1);
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else
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n->left = NULL;
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if (middle + 1 <= high)
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n->right = splay_tree_rebalance_helper2 (array, middle + 1, high);
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else
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n->right = NULL;
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return n;
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}
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/* Rebalance the entire tree. Do this by copying all the node
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pointers into an array, then cleverly re-linking them. */
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void
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splay_tree_rebalance (splay_tree sp)
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{
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splay_tree_node *all_nodes, *all_nodes_1;
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if (sp->num_keys <= 2)
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return;
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all_nodes = splay_tree_xmalloc (sizeof (splay_tree_node) * sp->num_keys);
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/* Traverse all nodes to copy their addresses into this array. */
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all_nodes_1 = all_nodes;
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splay_tree_foreach (sp, splay_tree_rebalance_helper1,
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(void *) &all_nodes_1);
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/* Relink all the nodes. */
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sp->root = splay_tree_rebalance_helper2 (all_nodes, 0, sp->num_keys - 1);
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splay_tree_free (all_nodes);
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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 (splay_tree sp, 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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/* If we just splayed the tree with the same key, do nothing. */
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if (sp->last_splayed_key_p &&
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compare_uintptr_t (sp->last_splayed_key, key) == 0)
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return;
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/* Compute a maximum recursion depth for a splay tree with NUM nodes.
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The idea is to limit excessive stack usage if we're facing
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degenerate access patterns. Unfortunately such patterns can occur
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e.g. during static initialization, where many static objects might
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be registered in increasing address sequence, or during a case where
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large tree-like heap data structures are allocated quickly.
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On x86, this corresponds to roughly 200K of stack usage.
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XXX: For libmudflapth, this could be a function of __mf_opts.thread_stack. */
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sp->max_depth = 2500;
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sp->rebalance_p = sp->depth = 0;
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splay_tree_splay_helper (sp, key, &sp->root, NULL, NULL);
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if (sp->rebalance_p)
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{
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splay_tree_rebalance (sp);
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sp->rebalance_p = sp->depth = 0;
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splay_tree_splay_helper (sp, key, &sp->root, NULL, NULL);
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if (sp->rebalance_p)
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abort ();
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}
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/* Cache this splay key. */
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sp->last_splayed_key = key;
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sp->last_splayed_key_p = 1;
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}
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/* Allocate a new splay tree. */
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splay_tree
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splay_tree_new ()
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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 = NULL;
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sp->last_splayed_key_p = 0;
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sp->num_keys = 0;
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return 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 (splay_tree sp, splay_tree_key key, 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 = compare_uintptr_t (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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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_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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sp->num_keys++;
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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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sp->last_splayed_key_p = 0;
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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 (splay_tree sp, splay_tree_key key)
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{
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splay_tree_splay (sp, key);
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sp->last_splayed_key_p = 0;
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if (sp->root && compare_uintptr_t (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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splay_tree_free (sp->root);
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sp->num_keys--;
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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 (splay_tree sp, splay_tree_key key)
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{
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splay_tree_splay (sp, key);
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if (sp->root && compare_uintptr_t (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 node in SP with the greatest key. */
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splay_tree_node
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splay_tree_max (splay_tree sp)
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{
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splay_tree_node n = sp->root;
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if (!n)
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return NULL;
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while (n->right)
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n = n->right;
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return n;
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}
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/* Return the node in SP with the smallest key. */
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splay_tree_node
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splay_tree_min (splay_tree sp)
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{
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splay_tree_node n = sp->root;
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if (!n)
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return NULL;
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while (n->left)
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n = n->left;
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return n;
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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 (splay_tree sp, 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 = compare_uintptr_t (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 rightmost element of the left 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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successor. KEY need not be present in the tree. */
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splay_tree_node
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splay_tree_successor (splay_tree sp, 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 successor. */
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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 = compare_uintptr_t (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 leftmost element of the right 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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This function simulates recursion using dynamically allocated
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arrays, since it may be called from splay_tree_rebalance(), which
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in turn means that the tree is already uncomfortably deep for stack
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space limits. */
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int
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splay_tree_foreach (splay_tree st, splay_tree_foreach_fn fn, void *data)
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{
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splay_tree_node *stack1;
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char *stack2;
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unsigned sp;
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int val = 0;
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enum s { s_left, s_here, s_right, s_up };
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if (st->root == NULL) /* => num_keys == 0 */
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return 0;
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stack1 = splay_tree_xmalloc (sizeof (splay_tree_node) * st->num_keys);
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stack2 = splay_tree_xmalloc (sizeof (char) * st->num_keys);
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sp = 0;
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stack1 [sp] = st->root;
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stack2 [sp] = s_left;
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while (1)
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{
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splay_tree_node n;
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enum s s;
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n = stack1 [sp];
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s = stack2 [sp];
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/* Handle each of the four possible states separately. */
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/* 1: We're here to traverse the left subtree (if any). */
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if (s == s_left)
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{
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stack2 [sp] = s_here;
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if (n->left != NULL)
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{
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sp ++;
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stack1 [sp] = n->left;
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stack2 [sp] = s_left;
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}
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}
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/* 2: We're here to traverse this node. */
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else if (s == s_here)
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{
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stack2 [sp] = s_right;
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val = (*fn) (n, data);
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if (val) break;
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}
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/* 3: We're here to traverse the right subtree (if any). */
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else if (s == s_right)
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{
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stack2 [sp] = s_up;
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if (n->right != NULL)
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{
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sp ++;
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stack1 [sp] = n->right;
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stack2 [sp] = s_left;
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}
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}
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/* 4: We're here after both subtrees (if any) have been traversed. */
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else if (s == s_up)
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{
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/* Pop the stack. */
|
|
if (sp == 0) break; /* Popping off the root note: we're finished! */
|
|
sp --;
|
|
}
|
|
|
|
else
|
|
abort ();
|
|
}
|
|
|
|
splay_tree_free (stack1);
|
|
splay_tree_free (stack2);
|
|
return val;
|
|
}
|