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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 Red Black Trees
3 (C) 1999 Andrea Arcangeli <andrea@suse.de>
4 (C) 2002 David Woodhouse <dwmw2@infradead.org>
5
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2 of the License, or
9 (at your option) any later version.
10
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software
18 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19
20 linux/lib/rbtree.c
21*/
22
23#include <linux/rbtree.h>
24#include <linux/module.h>
25
26static void __rb_rotate_left(struct rb_node *node, struct rb_root *root)
27{
28 struct rb_node *right = node->rb_right;
David Woodhouse55a98102006-04-21 13:35:51 +010029 struct rb_node *parent = rb_parent(node);
Linus Torvalds1da177e2005-04-16 15:20:36 -070030
31 if ((node->rb_right = right->rb_left))
David Woodhouse55a98102006-04-21 13:35:51 +010032 rb_set_parent(right->rb_left, node);
Linus Torvalds1da177e2005-04-16 15:20:36 -070033 right->rb_left = node;
34
David Woodhouse55a98102006-04-21 13:35:51 +010035 rb_set_parent(right, parent);
36
37 if (parent)
Linus Torvalds1da177e2005-04-16 15:20:36 -070038 {
David Woodhouse55a98102006-04-21 13:35:51 +010039 if (node == parent->rb_left)
40 parent->rb_left = right;
Linus Torvalds1da177e2005-04-16 15:20:36 -070041 else
David Woodhouse55a98102006-04-21 13:35:51 +010042 parent->rb_right = right;
Linus Torvalds1da177e2005-04-16 15:20:36 -070043 }
44 else
45 root->rb_node = right;
David Woodhouse55a98102006-04-21 13:35:51 +010046 rb_set_parent(node, right);
Linus Torvalds1da177e2005-04-16 15:20:36 -070047}
48
49static void __rb_rotate_right(struct rb_node *node, struct rb_root *root)
50{
51 struct rb_node *left = node->rb_left;
David Woodhouse55a98102006-04-21 13:35:51 +010052 struct rb_node *parent = rb_parent(node);
Linus Torvalds1da177e2005-04-16 15:20:36 -070053
54 if ((node->rb_left = left->rb_right))
David Woodhouse55a98102006-04-21 13:35:51 +010055 rb_set_parent(left->rb_right, node);
Linus Torvalds1da177e2005-04-16 15:20:36 -070056 left->rb_right = node;
57
David Woodhouse55a98102006-04-21 13:35:51 +010058 rb_set_parent(left, parent);
59
60 if (parent)
Linus Torvalds1da177e2005-04-16 15:20:36 -070061 {
David Woodhouse55a98102006-04-21 13:35:51 +010062 if (node == parent->rb_right)
63 parent->rb_right = left;
Linus Torvalds1da177e2005-04-16 15:20:36 -070064 else
David Woodhouse55a98102006-04-21 13:35:51 +010065 parent->rb_left = left;
Linus Torvalds1da177e2005-04-16 15:20:36 -070066 }
67 else
68 root->rb_node = left;
David Woodhouse55a98102006-04-21 13:35:51 +010069 rb_set_parent(node, left);
Linus Torvalds1da177e2005-04-16 15:20:36 -070070}
71
72void rb_insert_color(struct rb_node *node, struct rb_root *root)
73{
74 struct rb_node *parent, *gparent;
75
David Woodhouse55a98102006-04-21 13:35:51 +010076 while ((parent = rb_parent(node)) && rb_is_red(parent))
Linus Torvalds1da177e2005-04-16 15:20:36 -070077 {
David Woodhouse55a98102006-04-21 13:35:51 +010078 gparent = rb_parent(parent);
Linus Torvalds1da177e2005-04-16 15:20:36 -070079
80 if (parent == gparent->rb_left)
81 {
82 {
83 register struct rb_node *uncle = gparent->rb_right;
David Woodhouse55a98102006-04-21 13:35:51 +010084 if (uncle && rb_is_red(uncle))
Linus Torvalds1da177e2005-04-16 15:20:36 -070085 {
David Woodhouse55a98102006-04-21 13:35:51 +010086 rb_set_black(uncle);
87 rb_set_black(parent);
88 rb_set_red(gparent);
Linus Torvalds1da177e2005-04-16 15:20:36 -070089 node = gparent;
90 continue;
91 }
92 }
93
94 if (parent->rb_right == node)
95 {
96 register struct rb_node *tmp;
97 __rb_rotate_left(parent, root);
98 tmp = parent;
99 parent = node;
100 node = tmp;
101 }
102
David Woodhouse55a98102006-04-21 13:35:51 +0100103 rb_set_black(parent);
104 rb_set_red(gparent);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 __rb_rotate_right(gparent, root);
106 } else {
107 {
108 register struct rb_node *uncle = gparent->rb_left;
David Woodhouse55a98102006-04-21 13:35:51 +0100109 if (uncle && rb_is_red(uncle))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110 {
David Woodhouse55a98102006-04-21 13:35:51 +0100111 rb_set_black(uncle);
112 rb_set_black(parent);
113 rb_set_red(gparent);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 node = gparent;
115 continue;
116 }
117 }
118
119 if (parent->rb_left == node)
120 {
121 register struct rb_node *tmp;
122 __rb_rotate_right(parent, root);
123 tmp = parent;
124 parent = node;
125 node = tmp;
126 }
127
David Woodhouse55a98102006-04-21 13:35:51 +0100128 rb_set_black(parent);
129 rb_set_red(gparent);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130 __rb_rotate_left(gparent, root);
131 }
132 }
133
David Woodhouse55a98102006-04-21 13:35:51 +0100134 rb_set_black(root->rb_node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135}
136EXPORT_SYMBOL(rb_insert_color);
137
138static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
139 struct rb_root *root)
140{
141 struct rb_node *other;
142
David Woodhouse55a98102006-04-21 13:35:51 +0100143 while ((!node || rb_is_black(node)) && node != root->rb_node)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700144 {
145 if (parent->rb_left == node)
146 {
147 other = parent->rb_right;
David Woodhouse55a98102006-04-21 13:35:51 +0100148 if (rb_is_red(other))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149 {
David Woodhouse55a98102006-04-21 13:35:51 +0100150 rb_set_black(other);
151 rb_set_red(parent);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700152 __rb_rotate_left(parent, root);
153 other = parent->rb_right;
154 }
David Woodhouse55a98102006-04-21 13:35:51 +0100155 if ((!other->rb_left || rb_is_black(other->rb_left)) &&
156 (!other->rb_right || rb_is_black(other->rb_right)))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157 {
David Woodhouse55a98102006-04-21 13:35:51 +0100158 rb_set_red(other);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 node = parent;
David Woodhouse55a98102006-04-21 13:35:51 +0100160 parent = rb_parent(node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161 }
162 else
163 {
David Woodhouse55a98102006-04-21 13:35:51 +0100164 if (!other->rb_right || rb_is_black(other->rb_right))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165 {
Wolfram Strepp55a63992009-03-31 15:23:45 -0700166 rb_set_black(other->rb_left);
David Woodhouse55a98102006-04-21 13:35:51 +0100167 rb_set_red(other);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700168 __rb_rotate_right(other, root);
169 other = parent->rb_right;
170 }
David Woodhouse2f3243a2006-06-05 20:19:05 +0100171 rb_set_color(other, rb_color(parent));
David Woodhouse55a98102006-04-21 13:35:51 +0100172 rb_set_black(parent);
Wolfram Strepp55a63992009-03-31 15:23:45 -0700173 rb_set_black(other->rb_right);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700174 __rb_rotate_left(parent, root);
175 node = root->rb_node;
176 break;
177 }
178 }
179 else
180 {
181 other = parent->rb_left;
David Woodhouse55a98102006-04-21 13:35:51 +0100182 if (rb_is_red(other))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183 {
David Woodhouse55a98102006-04-21 13:35:51 +0100184 rb_set_black(other);
185 rb_set_red(parent);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186 __rb_rotate_right(parent, root);
187 other = parent->rb_left;
188 }
David Woodhouse55a98102006-04-21 13:35:51 +0100189 if ((!other->rb_left || rb_is_black(other->rb_left)) &&
190 (!other->rb_right || rb_is_black(other->rb_right)))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191 {
David Woodhouse55a98102006-04-21 13:35:51 +0100192 rb_set_red(other);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193 node = parent;
David Woodhouse55a98102006-04-21 13:35:51 +0100194 parent = rb_parent(node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700195 }
196 else
197 {
David Woodhouse55a98102006-04-21 13:35:51 +0100198 if (!other->rb_left || rb_is_black(other->rb_left))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700199 {
Wolfram Strepp55a63992009-03-31 15:23:45 -0700200 rb_set_black(other->rb_right);
David Woodhouse55a98102006-04-21 13:35:51 +0100201 rb_set_red(other);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202 __rb_rotate_left(other, root);
203 other = parent->rb_left;
204 }
David Woodhouse2f3243a2006-06-05 20:19:05 +0100205 rb_set_color(other, rb_color(parent));
David Woodhouse55a98102006-04-21 13:35:51 +0100206 rb_set_black(parent);
Wolfram Strepp55a63992009-03-31 15:23:45 -0700207 rb_set_black(other->rb_left);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700208 __rb_rotate_right(parent, root);
209 node = root->rb_node;
210 break;
211 }
212 }
213 }
214 if (node)
David Woodhouse55a98102006-04-21 13:35:51 +0100215 rb_set_black(node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700216}
217
218void rb_erase(struct rb_node *node, struct rb_root *root)
219{
220 struct rb_node *child, *parent;
221 int color;
222
223 if (!node->rb_left)
224 child = node->rb_right;
225 else if (!node->rb_right)
226 child = node->rb_left;
227 else
228 {
229 struct rb_node *old = node, *left;
230
231 node = node->rb_right;
232 while ((left = node->rb_left) != NULL)
233 node = left;
234 child = node->rb_right;
David Woodhouse55a98102006-04-21 13:35:51 +0100235 parent = rb_parent(node);
David Woodhouse2f3243a2006-06-05 20:19:05 +0100236 color = rb_color(node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700237
238 if (child)
David Woodhouse55a98102006-04-21 13:35:51 +0100239 rb_set_parent(child, parent);
240 if (parent == old) {
David Woodhouse1975e592006-04-21 13:30:36 +0100241 parent->rb_right = child;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242 parent = node;
David Woodhouse55a98102006-04-21 13:35:51 +0100243 } else
David Woodhouse1975e592006-04-21 13:30:36 +0100244 parent->rb_left = child;
245
David Woodhouse2f3243a2006-06-05 20:19:05 +0100246 node->rb_parent_color = old->rb_parent_color;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700247 node->rb_right = old->rb_right;
248 node->rb_left = old->rb_left;
249
David Woodhouse55a98102006-04-21 13:35:51 +0100250 if (rb_parent(old))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251 {
David Woodhouse55a98102006-04-21 13:35:51 +0100252 if (rb_parent(old)->rb_left == old)
253 rb_parent(old)->rb_left = node;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700254 else
David Woodhouse55a98102006-04-21 13:35:51 +0100255 rb_parent(old)->rb_right = node;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700256 } else
257 root->rb_node = node;
258
David Woodhouse55a98102006-04-21 13:35:51 +0100259 rb_set_parent(old->rb_left, node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700260 if (old->rb_right)
David Woodhouse55a98102006-04-21 13:35:51 +0100261 rb_set_parent(old->rb_right, node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262 goto color;
263 }
264
David Woodhouse55a98102006-04-21 13:35:51 +0100265 parent = rb_parent(node);
David Woodhouse2f3243a2006-06-05 20:19:05 +0100266 color = rb_color(node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267
268 if (child)
David Woodhouse55a98102006-04-21 13:35:51 +0100269 rb_set_parent(child, parent);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700270 if (parent)
271 {
272 if (parent->rb_left == node)
273 parent->rb_left = child;
274 else
275 parent->rb_right = child;
276 }
277 else
278 root->rb_node = child;
279
280 color:
281 if (color == RB_BLACK)
282 __rb_erase_color(child, parent, root);
283}
284EXPORT_SYMBOL(rb_erase);
285
286/*
287 * This function returns the first node (in sort order) of the tree.
288 */
Artem Bityutskiyf4b477c2009-01-10 11:12:09 +0000289struct rb_node *rb_first(const struct rb_root *root)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700290{
291 struct rb_node *n;
292
293 n = root->rb_node;
294 if (!n)
295 return NULL;
296 while (n->rb_left)
297 n = n->rb_left;
298 return n;
299}
300EXPORT_SYMBOL(rb_first);
301
Artem Bityutskiyf4b477c2009-01-10 11:12:09 +0000302struct rb_node *rb_last(const struct rb_root *root)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700303{
304 struct rb_node *n;
305
306 n = root->rb_node;
307 if (!n)
308 return NULL;
309 while (n->rb_right)
310 n = n->rb_right;
311 return n;
312}
313EXPORT_SYMBOL(rb_last);
314
Artem Bityutskiyf4b477c2009-01-10 11:12:09 +0000315struct rb_node *rb_next(const struct rb_node *node)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700316{
David Woodhouse55a98102006-04-21 13:35:51 +0100317 struct rb_node *parent;
318
Jens Axboe10fd48f2006-07-11 21:15:52 +0200319 if (rb_parent(node) == node)
320 return NULL;
321
Linus Torvalds1da177e2005-04-16 15:20:36 -0700322 /* If we have a right-hand child, go down and then left as far
323 as we can. */
324 if (node->rb_right) {
325 node = node->rb_right;
326 while (node->rb_left)
327 node=node->rb_left;
Artem Bityutskiyf4b477c2009-01-10 11:12:09 +0000328 return (struct rb_node *)node;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700329 }
330
331 /* No right-hand children. Everything down and left is
332 smaller than us, so any 'next' node must be in the general
333 direction of our parent. Go up the tree; any time the
334 ancestor is a right-hand child of its parent, keep going
335 up. First time it's a left-hand child of its parent, said
336 parent is our 'next' node. */
David Woodhouse55a98102006-04-21 13:35:51 +0100337 while ((parent = rb_parent(node)) && node == parent->rb_right)
338 node = parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700339
David Woodhouse55a98102006-04-21 13:35:51 +0100340 return parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341}
342EXPORT_SYMBOL(rb_next);
343
Artem Bityutskiyf4b477c2009-01-10 11:12:09 +0000344struct rb_node *rb_prev(const struct rb_node *node)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700345{
David Woodhouse55a98102006-04-21 13:35:51 +0100346 struct rb_node *parent;
347
Jens Axboe10fd48f2006-07-11 21:15:52 +0200348 if (rb_parent(node) == node)
349 return NULL;
350
Linus Torvalds1da177e2005-04-16 15:20:36 -0700351 /* If we have a left-hand child, go down and then right as far
352 as we can. */
353 if (node->rb_left) {
354 node = node->rb_left;
355 while (node->rb_right)
356 node=node->rb_right;
Artem Bityutskiyf4b477c2009-01-10 11:12:09 +0000357 return (struct rb_node *)node;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700358 }
359
360 /* No left-hand children. Go up till we find an ancestor which
361 is a right-hand child of its parent */
David Woodhouse55a98102006-04-21 13:35:51 +0100362 while ((parent = rb_parent(node)) && node == parent->rb_left)
363 node = parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700364
David Woodhouse55a98102006-04-21 13:35:51 +0100365 return parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700366}
367EXPORT_SYMBOL(rb_prev);
368
369void rb_replace_node(struct rb_node *victim, struct rb_node *new,
370 struct rb_root *root)
371{
David Woodhouse55a98102006-04-21 13:35:51 +0100372 struct rb_node *parent = rb_parent(victim);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700373
374 /* Set the surrounding nodes to point to the replacement */
375 if (parent) {
376 if (victim == parent->rb_left)
377 parent->rb_left = new;
378 else
379 parent->rb_right = new;
380 } else {
381 root->rb_node = new;
382 }
383 if (victim->rb_left)
David Woodhouse55a98102006-04-21 13:35:51 +0100384 rb_set_parent(victim->rb_left, new);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700385 if (victim->rb_right)
David Woodhouse55a98102006-04-21 13:35:51 +0100386 rb_set_parent(victim->rb_right, new);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387
388 /* Copy the pointers/colour from the victim to the replacement */
389 *new = *victim;
390}
391EXPORT_SYMBOL(rb_replace_node);