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. */
27 #include "libiberty.h"
29 #include "splay-tree.h"
31 static void splay_tree_delete_helper PARAMS((splay_tree,
33 static void splay_tree_splay PARAMS((splay_tree,
35 static splay_tree_node splay_tree_splay_helper
41 static int splay_tree_foreach_helper PARAMS((splay_tree,
43 splay_tree_foreach_fn,
46 /* Deallocate NODE (a member of SP), and all its sub-trees. */
49 splay_tree_delete_helper (sp, node)
56 splay_tree_delete_helper (sp, node->left);
57 splay_tree_delete_helper (sp, node->right);
60 (*sp->delete_key)(node->key);
62 (*sp->delete_value)(node->value);
67 /* Help splay SP around KEY. PARENT and GRANDPARENT are the parent
68 and grandparent, respectively, of NODE. */
70 static splay_tree_node
71 splay_tree_splay_helper (sp, key, node, parent, grandparent)
74 splay_tree_node *node;
75 splay_tree_node *parent;
76 splay_tree_node *grandparent;
78 splay_tree_node *next;
87 comparison = (*sp->comp) (key, n->key);
90 /* We've found the target. */
92 else if (comparison < 0)
93 /* The target is to the left. */
96 /* The target is to the right. */
101 /* Continue down the tree. */
102 n = splay_tree_splay_helper (sp, key, next, node, parent);
104 /* The recursive call will change the place to which NODE
111 /* NODE is the root. We are done. */
114 /* First, handle the case where there is no grandparent (i.e.,
115 *PARENT is the root of the tree.) */
118 if (n == (*parent)->left)
132 /* Next handle the cases where both N and *PARENT are left children,
133 or where both are right children. */
134 if (n == (*parent)->left && *parent == (*grandparent)->left)
136 splay_tree_node p = *parent;
138 (*grandparent)->left = p->right;
139 p->right = *grandparent;
145 else if (n == (*parent)->right && *parent == (*grandparent)->right)
147 splay_tree_node p = *parent;
149 (*grandparent)->right = p->left;
150 p->left = *grandparent;
157 /* Finally, deal with the case where N is a left child, but *PARENT
158 is a right child, or vice versa. */
159 if (n == (*parent)->left)
161 (*parent)->left = n->right;
163 (*grandparent)->right = n->left;
164 n->left = *grandparent;
170 (*parent)->right = n->left;
172 (*grandparent)->left = n->right;
173 n->right = *grandparent;
179 /* Splay SP around KEY. */
182 splay_tree_splay (sp, key)
189 splay_tree_splay_helper (sp, key, &sp->root,
190 /*grandparent=*/0, /*parent=*/0);
193 /* Call FN, passing it the DATA, for every node below NODE, all of
194 which are from SP, following an in-order traversal. If FN every
195 returns a non-zero value, the iteration ceases immediately, and the
196 value is returned. Otherwise, this function returns 0. */
199 splay_tree_foreach_helper (sp, node, fn, data)
201 splay_tree_node node;
202 splay_tree_foreach_fn fn;
210 val = splay_tree_foreach_helper (sp, node->left, fn, data);
214 val = (*fn)(node, data);
218 return splay_tree_foreach_helper (sp, node->right, fn, data);
221 /* Allocate a new splay tree, using COMPARE_FN to compare nodes,
222 DELETE_KEY_FN to deallocate keys, and DELETE_VALUE_FN to deallocate
226 splay_tree_new (compare_fn, delete_key_fn, delete_value_fn)
227 splay_tree_compare_fn compare_fn;
228 splay_tree_delete_key_fn delete_key_fn;
229 splay_tree_delete_value_fn delete_value_fn;
231 splay_tree sp = (splay_tree) xmalloc (sizeof (struct splay_tree));
233 sp->comp = compare_fn;
234 sp->delete_key = delete_key_fn;
235 sp->delete_value = delete_value_fn;
243 splay_tree_delete (sp)
246 splay_tree_delete_helper (sp, sp->root);
250 /* Insert a new node (associating KEY with DATA) into SP. If a
251 previous node with the indicated KEY exists, its data is replaced
252 with the new value. */
255 splay_tree_insert (sp, key, value)
258 splay_tree_value value;
262 splay_tree_splay (sp, key);
265 comparison = (*sp->comp)(sp->root->key, key);
267 if (sp->root && comparison == 0)
269 /* If the root of the tree already has the indicated KEY, just
270 replace the value with VALUE. */
271 if (sp->delete_value)
272 (*sp->delete_value)(sp->root->value);
273 sp->root->value = value;
277 /* Create a new node, and insert it at the root. */
278 splay_tree_node node;
280 node = (splay_tree_node) xmalloc (sizeof (struct splay_tree_node));
285 node->left = node->right = 0;
286 else if (comparison < 0)
288 node->left = sp->root;
289 node->right = node->left->right;
290 node->left->right = 0;
294 node->right = sp->root;
295 node->left = node->right->left;
296 node->right->left = 0;
303 /* Lookup KEY in SP, returning VALUE if present, and NULL
307 splay_tree_lookup (sp, key)
311 splay_tree_splay (sp, key);
313 if (sp->root && (*sp->comp)(sp->root->key, key) == 0)
319 /* Call FN, passing it the DATA, for every node in SP, following an
320 in-order traversal. If FN every returns a non-zero value, the
321 iteration ceases immediately, and the value is returned.
322 Otherwise, this function returns 0. */
325 splay_tree_foreach (sp, fn, data)
327 splay_tree_foreach_fn fn;
330 return splay_tree_foreach_helper (sp, sp->root, fn, data);