1 /* A splay-tree datatype.
2 Copyright (C) 1998 Free Software Foundation, Inc.
3 Contributed by Mark Mitchell (mark@markmitchell.com).
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify it
8 under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GNU CC is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to the Free
19 Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
21 For an easily readable description of splay-trees, see:
23 Lewis, Harry R. and Denenberg, Larry. Data Structures and Their
24 Algorithms. Harper-Collins, Inc. 1991. */
34 #include "libiberty.h"
35 #include "splay-tree.h"
37 static void splay_tree_delete_helper PARAMS((splay_tree,
39 static void splay_tree_splay PARAMS((splay_tree,
41 static splay_tree_node splay_tree_splay_helper
47 static int splay_tree_foreach_helper PARAMS((splay_tree,
49 splay_tree_foreach_fn,
52 /* Deallocate NODE (a member of SP), and all its sub-trees. */
55 splay_tree_delete_helper (sp, node)
62 splay_tree_delete_helper (sp, node->left);
63 splay_tree_delete_helper (sp, node->right);
66 (*sp->delete_key)(node->key);
68 (*sp->delete_value)(node->value);
73 /* Help splay SP around KEY. PARENT and GRANDPARENT are the parent
74 and grandparent, respectively, of NODE. */
76 static splay_tree_node
77 splay_tree_splay_helper (sp, key, node, parent, grandparent)
80 splay_tree_node *node;
81 splay_tree_node *parent;
82 splay_tree_node *grandparent;
84 splay_tree_node *next;
93 comparison = (*sp->comp) (key, n->key);
96 /* We've found the target. */
98 else if (comparison < 0)
99 /* The target is to the left. */
102 /* The target is to the right. */
107 /* Continue down the tree. */
108 n = splay_tree_splay_helper (sp, key, next, node, parent);
110 /* The recursive call will change the place to which NODE
117 /* NODE is the root. We are done. */
120 /* First, handle the case where there is no grandparent (i.e.,
121 *PARENT is the root of the tree.) */
124 if (n == (*parent)->left)
138 /* Next handle the cases where both N and *PARENT are left children,
139 or where both are right children. */
140 if (n == (*parent)->left && *parent == (*grandparent)->left)
142 splay_tree_node p = *parent;
144 (*grandparent)->left = p->right;
145 p->right = *grandparent;
151 else if (n == (*parent)->right && *parent == (*grandparent)->right)
153 splay_tree_node p = *parent;
155 (*grandparent)->right = p->left;
156 p->left = *grandparent;
163 /* Finally, deal with the case where N is a left child, but *PARENT
164 is a right child, or vice versa. */
165 if (n == (*parent)->left)
167 (*parent)->left = n->right;
169 (*grandparent)->right = n->left;
170 n->left = *grandparent;
176 (*parent)->right = n->left;
178 (*grandparent)->left = n->right;
179 n->right = *grandparent;
185 /* Splay SP around KEY. */
188 splay_tree_splay (sp, key)
195 splay_tree_splay_helper (sp, key, &sp->root,
196 /*grandparent=*/0, /*parent=*/0);
199 /* Call FN, passing it the DATA, for every node below NODE, all of
200 which are from SP, following an in-order traversal. If FN every
201 returns a non-zero value, the iteration ceases immediately, and the
202 value is returned. Otherwise, this function returns 0. */
205 splay_tree_foreach_helper (sp, node, fn, data)
207 splay_tree_node node;
208 splay_tree_foreach_fn fn;
216 val = splay_tree_foreach_helper (sp, node->left, fn, data);
220 val = (*fn)(node, data);
224 return splay_tree_foreach_helper (sp, node->right, fn, data);
227 /* Allocate a new splay tree, using COMPARE_FN to compare nodes,
228 DELETE_KEY_FN to deallocate keys, and DELETE_VALUE_FN to deallocate
232 splay_tree_new (compare_fn, delete_key_fn, delete_value_fn)
233 splay_tree_compare_fn compare_fn;
234 splay_tree_delete_key_fn delete_key_fn;
235 splay_tree_delete_value_fn delete_value_fn;
237 splay_tree sp = (splay_tree) xmalloc (sizeof (struct splay_tree));
239 sp->comp = compare_fn;
240 sp->delete_key = delete_key_fn;
241 sp->delete_value = delete_value_fn;
249 splay_tree_delete (sp)
252 splay_tree_delete_helper (sp, sp->root);
256 /* Insert a new node (associating KEY with DATA) into SP. If a
257 previous node with the indicated KEY exists, its data is replaced
258 with the new value. */
261 splay_tree_insert (sp, key, value)
264 splay_tree_value value;
268 splay_tree_splay (sp, key);
271 comparison = (*sp->comp)(sp->root->key, key);
273 if (sp->root && comparison == 0)
275 /* If the root of the tree already has the indicated KEY, just
276 replace the value with VALUE. */
277 if (sp->delete_value)
278 (*sp->delete_value)(sp->root->value);
279 sp->root->value = value;
283 /* Create a new node, and insert it at the root. */
284 splay_tree_node node;
286 node = (splay_tree_node) xmalloc (sizeof (struct splay_tree_node));
291 node->left = node->right = 0;
292 else if (comparison < 0)
294 node->left = sp->root;
295 node->right = node->left->right;
296 node->left->right = 0;
300 node->right = sp->root;
301 node->left = node->right->left;
302 node->right->left = 0;
309 /* Lookup KEY in SP, returning VALUE if present, and NULL
313 splay_tree_lookup (sp, key)
317 splay_tree_splay (sp, key);
319 if (sp->root && (*sp->comp)(sp->root->key, key) == 0)
325 /* Call FN, passing it the DATA, for every node in SP, following an
326 in-order traversal. If FN every returns a non-zero value, the
327 iteration ceases immediately, and the value is returned.
328 Otherwise, this function returns 0. */
331 splay_tree_foreach (sp, fn, data)
333 splay_tree_foreach_fn fn;
336 return splay_tree_foreach_helper (sp, sp->root, fn, data);