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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 {
David Woodhouse55a98102006-04-21 13:35:51 +0100166 struct rb_node *o_left;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700167 if ((o_left = other->rb_left))
David Woodhouse55a98102006-04-21 13:35:51 +0100168 rb_set_black(o_left);
169 rb_set_red(other);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170 __rb_rotate_right(other, root);
171 other = parent->rb_right;
172 }
David Woodhouse2f3243a2006-06-05 20:19:05 +0100173 rb_set_color(other, rb_color(parent));
David Woodhouse55a98102006-04-21 13:35:51 +0100174 rb_set_black(parent);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175 if (other->rb_right)
David Woodhouse55a98102006-04-21 13:35:51 +0100176 rb_set_black(other->rb_right);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700177 __rb_rotate_left(parent, root);
178 node = root->rb_node;
179 break;
180 }
181 }
182 else
183 {
184 other = parent->rb_left;
David Woodhouse55a98102006-04-21 13:35:51 +0100185 if (rb_is_red(other))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186 {
David Woodhouse55a98102006-04-21 13:35:51 +0100187 rb_set_black(other);
188 rb_set_red(parent);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189 __rb_rotate_right(parent, root);
190 other = parent->rb_left;
191 }
David Woodhouse55a98102006-04-21 13:35:51 +0100192 if ((!other->rb_left || rb_is_black(other->rb_left)) &&
193 (!other->rb_right || rb_is_black(other->rb_right)))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194 {
David Woodhouse55a98102006-04-21 13:35:51 +0100195 rb_set_red(other);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196 node = parent;
David Woodhouse55a98102006-04-21 13:35:51 +0100197 parent = rb_parent(node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700198 }
199 else
200 {
David Woodhouse55a98102006-04-21 13:35:51 +0100201 if (!other->rb_left || rb_is_black(other->rb_left))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202 {
203 register struct rb_node *o_right;
204 if ((o_right = other->rb_right))
David Woodhouse55a98102006-04-21 13:35:51 +0100205 rb_set_black(o_right);
206 rb_set_red(other);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207 __rb_rotate_left(other, root);
208 other = parent->rb_left;
209 }
David Woodhouse2f3243a2006-06-05 20:19:05 +0100210 rb_set_color(other, rb_color(parent));
David Woodhouse55a98102006-04-21 13:35:51 +0100211 rb_set_black(parent);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212 if (other->rb_left)
David Woodhouse55a98102006-04-21 13:35:51 +0100213 rb_set_black(other->rb_left);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214 __rb_rotate_right(parent, root);
215 node = root->rb_node;
216 break;
217 }
218 }
219 }
220 if (node)
David Woodhouse55a98102006-04-21 13:35:51 +0100221 rb_set_black(node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222}
223
224void rb_erase(struct rb_node *node, struct rb_root *root)
225{
226 struct rb_node *child, *parent;
227 int color;
228
229 if (!node->rb_left)
230 child = node->rb_right;
231 else if (!node->rb_right)
232 child = node->rb_left;
233 else
234 {
235 struct rb_node *old = node, *left;
236
237 node = node->rb_right;
238 while ((left = node->rb_left) != NULL)
239 node = left;
240 child = node->rb_right;
David Woodhouse55a98102006-04-21 13:35:51 +0100241 parent = rb_parent(node);
David Woodhouse2f3243a2006-06-05 20:19:05 +0100242 color = rb_color(node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700243
244 if (child)
David Woodhouse55a98102006-04-21 13:35:51 +0100245 rb_set_parent(child, parent);
246 if (parent == old) {
David Woodhouse1975e592006-04-21 13:30:36 +0100247 parent->rb_right = child;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700248 parent = node;
David Woodhouse55a98102006-04-21 13:35:51 +0100249 } else
David Woodhouse1975e592006-04-21 13:30:36 +0100250 parent->rb_left = child;
251
David Woodhouse2f3243a2006-06-05 20:19:05 +0100252 node->rb_parent_color = old->rb_parent_color;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700253 node->rb_right = old->rb_right;
254 node->rb_left = old->rb_left;
255
David Woodhouse55a98102006-04-21 13:35:51 +0100256 if (rb_parent(old))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700257 {
David Woodhouse55a98102006-04-21 13:35:51 +0100258 if (rb_parent(old)->rb_left == old)
259 rb_parent(old)->rb_left = node;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700260 else
David Woodhouse55a98102006-04-21 13:35:51 +0100261 rb_parent(old)->rb_right = node;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262 } else
263 root->rb_node = node;
264
David Woodhouse55a98102006-04-21 13:35:51 +0100265 rb_set_parent(old->rb_left, node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266 if (old->rb_right)
David Woodhouse55a98102006-04-21 13:35:51 +0100267 rb_set_parent(old->rb_right, node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700268 goto color;
269 }
270
David Woodhouse55a98102006-04-21 13:35:51 +0100271 parent = rb_parent(node);
David Woodhouse2f3243a2006-06-05 20:19:05 +0100272 color = rb_color(node);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700273
274 if (child)
David Woodhouse55a98102006-04-21 13:35:51 +0100275 rb_set_parent(child, parent);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700276 if (parent)
277 {
278 if (parent->rb_left == node)
279 parent->rb_left = child;
280 else
281 parent->rb_right = child;
282 }
283 else
284 root->rb_node = child;
285
286 color:
287 if (color == RB_BLACK)
288 __rb_erase_color(child, parent, root);
289}
290EXPORT_SYMBOL(rb_erase);
291
292/*
293 * This function returns the first node (in sort order) of the tree.
294 */
295struct rb_node *rb_first(struct rb_root *root)
296{
297 struct rb_node *n;
298
299 n = root->rb_node;
300 if (!n)
301 return NULL;
302 while (n->rb_left)
303 n = n->rb_left;
304 return n;
305}
306EXPORT_SYMBOL(rb_first);
307
308struct rb_node *rb_last(struct rb_root *root)
309{
310 struct rb_node *n;
311
312 n = root->rb_node;
313 if (!n)
314 return NULL;
315 while (n->rb_right)
316 n = n->rb_right;
317 return n;
318}
319EXPORT_SYMBOL(rb_last);
320
321struct rb_node *rb_next(struct rb_node *node)
322{
David Woodhouse55a98102006-04-21 13:35:51 +0100323 struct rb_node *parent;
324
Jens Axboe10fd48f2006-07-11 21:15:52 +0200325 if (rb_parent(node) == node)
326 return NULL;
327
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328 /* If we have a right-hand child, go down and then left as far
329 as we can. */
330 if (node->rb_right) {
331 node = node->rb_right;
332 while (node->rb_left)
333 node=node->rb_left;
334 return node;
335 }
336
337 /* No right-hand children. Everything down and left is
338 smaller than us, so any 'next' node must be in the general
339 direction of our parent. Go up the tree; any time the
340 ancestor is a right-hand child of its parent, keep going
341 up. First time it's a left-hand child of its parent, said
342 parent is our 'next' node. */
David Woodhouse55a98102006-04-21 13:35:51 +0100343 while ((parent = rb_parent(node)) && node == parent->rb_right)
344 node = parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700345
David Woodhouse55a98102006-04-21 13:35:51 +0100346 return parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700347}
348EXPORT_SYMBOL(rb_next);
349
350struct rb_node *rb_prev(struct rb_node *node)
351{
David Woodhouse55a98102006-04-21 13:35:51 +0100352 struct rb_node *parent;
353
Jens Axboe10fd48f2006-07-11 21:15:52 +0200354 if (rb_parent(node) == node)
355 return NULL;
356
Linus Torvalds1da177e2005-04-16 15:20:36 -0700357 /* If we have a left-hand child, go down and then right as far
358 as we can. */
359 if (node->rb_left) {
360 node = node->rb_left;
361 while (node->rb_right)
362 node=node->rb_right;
363 return node;
364 }
365
366 /* No left-hand children. Go up till we find an ancestor which
367 is a right-hand child of its parent */
David Woodhouse55a98102006-04-21 13:35:51 +0100368 while ((parent = rb_parent(node)) && node == parent->rb_left)
369 node = parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700370
David Woodhouse55a98102006-04-21 13:35:51 +0100371 return parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700372}
373EXPORT_SYMBOL(rb_prev);
374
375void rb_replace_node(struct rb_node *victim, struct rb_node *new,
376 struct rb_root *root)
377{
David Woodhouse55a98102006-04-21 13:35:51 +0100378 struct rb_node *parent = rb_parent(victim);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700379
380 /* Set the surrounding nodes to point to the replacement */
381 if (parent) {
382 if (victim == parent->rb_left)
383 parent->rb_left = new;
384 else
385 parent->rb_right = new;
386 } else {
387 root->rb_node = new;
388 }
389 if (victim->rb_left)
David Woodhouse55a98102006-04-21 13:35:51 +0100390 rb_set_parent(victim->rb_left, new);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700391 if (victim->rb_right)
David Woodhouse55a98102006-04-21 13:35:51 +0100392 rb_set_parent(victim->rb_right, new);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700393
394 /* Copy the pointers/colour from the victim to the replacement */
395 *new = *victim;
396}
397EXPORT_SYMBOL(rb_replace_node);