1 /*
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 "rbtree.h"
24
__rb_rotate_left(struct rb_node * node,struct rb_root * root)25 static void __rb_rotate_left(struct rb_node *node, struct rb_root *root)
26 {
27 struct rb_node *right = node->rb_right;
28 struct rb_node *parent = ext2fs_rb_parent(node);
29
30 if ((node->rb_right = right->rb_left))
31 ext2fs_rb_set_parent(right->rb_left, node);
32 right->rb_left = node;
33
34 ext2fs_rb_set_parent(right, parent);
35
36 if (parent)
37 {
38 if (node == parent->rb_left)
39 parent->rb_left = right;
40 else
41 parent->rb_right = right;
42 }
43 else
44 root->rb_node = right;
45 ext2fs_rb_set_parent(node, right);
46 }
47
__rb_rotate_right(struct rb_node * node,struct rb_root * root)48 static void __rb_rotate_right(struct rb_node *node, struct rb_root *root)
49 {
50 struct rb_node *left = node->rb_left;
51 struct rb_node *parent = ext2fs_rb_parent(node);
52
53 if ((node->rb_left = left->rb_right))
54 ext2fs_rb_set_parent(left->rb_right, node);
55 left->rb_right = node;
56
57 ext2fs_rb_set_parent(left, parent);
58
59 if (parent)
60 {
61 if (node == parent->rb_right)
62 parent->rb_right = left;
63 else
64 parent->rb_left = left;
65 }
66 else
67 root->rb_node = left;
68 ext2fs_rb_set_parent(node, left);
69 }
70
ext2fs_rb_insert_color(struct rb_node * node,struct rb_root * root)71 void ext2fs_rb_insert_color(struct rb_node *node, struct rb_root *root)
72 {
73 struct rb_node *parent, *gparent;
74
75 while ((parent = ext2fs_rb_parent(node)) && ext2fs_rb_is_red(parent))
76 {
77 gparent = ext2fs_rb_parent(parent);
78
79 if (parent == gparent->rb_left)
80 {
81 {
82 register struct rb_node *uncle = gparent->rb_right;
83 if (uncle && ext2fs_rb_is_red(uncle))
84 {
85 ext2fs_rb_set_black(uncle);
86 ext2fs_rb_set_black(parent);
87 ext2fs_rb_set_red(gparent);
88 node = gparent;
89 continue;
90 }
91 }
92
93 if (parent->rb_right == node)
94 {
95 register struct rb_node *tmp;
96 __rb_rotate_left(parent, root);
97 tmp = parent;
98 parent = node;
99 node = tmp;
100 }
101
102 ext2fs_rb_set_black(parent);
103 ext2fs_rb_set_red(gparent);
104 __rb_rotate_right(gparent, root);
105 } else {
106 {
107 register struct rb_node *uncle = gparent->rb_left;
108 if (uncle && ext2fs_rb_is_red(uncle))
109 {
110 ext2fs_rb_set_black(uncle);
111 ext2fs_rb_set_black(parent);
112 ext2fs_rb_set_red(gparent);
113 node = gparent;
114 continue;
115 }
116 }
117
118 if (parent->rb_left == node)
119 {
120 register struct rb_node *tmp;
121 __rb_rotate_right(parent, root);
122 tmp = parent;
123 parent = node;
124 node = tmp;
125 }
126
127 ext2fs_rb_set_black(parent);
128 ext2fs_rb_set_red(gparent);
129 __rb_rotate_left(gparent, root);
130 }
131 }
132
133 ext2fs_rb_set_black(root->rb_node);
134 }
135
__rb_erase_color(struct rb_node * node,struct rb_node * parent,struct rb_root * root)136 static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
137 struct rb_root *root)
138 {
139 struct rb_node *other;
140
141 while ((!node || ext2fs_rb_is_black(node)) && node != root->rb_node)
142 {
143 if (parent->rb_left == node)
144 {
145 other = parent->rb_right;
146 if (ext2fs_rb_is_red(other))
147 {
148 ext2fs_rb_set_black(other);
149 ext2fs_rb_set_red(parent);
150 __rb_rotate_left(parent, root);
151 other = parent->rb_right;
152 }
153 if ((!other->rb_left || ext2fs_rb_is_black(other->rb_left)) &&
154 (!other->rb_right || ext2fs_rb_is_black(other->rb_right)))
155 {
156 ext2fs_rb_set_red(other);
157 node = parent;
158 parent = ext2fs_rb_parent(node);
159 }
160 else
161 {
162 if (!other->rb_right || ext2fs_rb_is_black(other->rb_right))
163 {
164 ext2fs_rb_set_black(other->rb_left);
165 ext2fs_rb_set_red(other);
166 __rb_rotate_right(other, root);
167 other = parent->rb_right;
168 }
169 ext2fs_rb_set_color(other, ext2fs_rb_color(parent));
170 ext2fs_rb_set_black(parent);
171 ext2fs_rb_set_black(other->rb_right);
172 __rb_rotate_left(parent, root);
173 node = root->rb_node;
174 break;
175 }
176 }
177 else
178 {
179 other = parent->rb_left;
180 if (ext2fs_rb_is_red(other))
181 {
182 ext2fs_rb_set_black(other);
183 ext2fs_rb_set_red(parent);
184 __rb_rotate_right(parent, root);
185 other = parent->rb_left;
186 }
187 if ((!other->rb_left || ext2fs_rb_is_black(other->rb_left)) &&
188 (!other->rb_right || ext2fs_rb_is_black(other->rb_right)))
189 {
190 ext2fs_rb_set_red(other);
191 node = parent;
192 parent = ext2fs_rb_parent(node);
193 }
194 else
195 {
196 if (!other->rb_left || ext2fs_rb_is_black(other->rb_left))
197 {
198 ext2fs_rb_set_black(other->rb_right);
199 ext2fs_rb_set_red(other);
200 __rb_rotate_left(other, root);
201 other = parent->rb_left;
202 }
203 ext2fs_rb_set_color(other, ext2fs_rb_color(parent));
204 ext2fs_rb_set_black(parent);
205 ext2fs_rb_set_black(other->rb_left);
206 __rb_rotate_right(parent, root);
207 node = root->rb_node;
208 break;
209 }
210 }
211 }
212 if (node)
213 ext2fs_rb_set_black(node);
214 }
215
ext2fs_rb_erase(struct rb_node * node,struct rb_root * root)216 void ext2fs_rb_erase(struct rb_node *node, struct rb_root *root)
217 {
218 struct rb_node *child, *parent;
219 int color;
220
221 if (!node->rb_left)
222 child = node->rb_right;
223 else if (!node->rb_right)
224 child = node->rb_left;
225 else
226 {
227 struct rb_node *old = node, *left;
228
229 node = node->rb_right;
230 while ((left = node->rb_left) != NULL)
231 node = left;
232
233 if (ext2fs_rb_parent(old)) {
234 if (ext2fs_rb_parent(old)->rb_left == old)
235 ext2fs_rb_parent(old)->rb_left = node;
236 else
237 ext2fs_rb_parent(old)->rb_right = node;
238 } else
239 root->rb_node = node;
240
241 child = node->rb_right;
242 parent = ext2fs_rb_parent(node);
243 color = ext2fs_rb_color(node);
244
245 if (parent == old) {
246 parent = node;
247 } else {
248 if (child)
249 ext2fs_rb_set_parent(child, parent);
250 parent->rb_left = child;
251
252 node->rb_right = old->rb_right;
253 ext2fs_rb_set_parent(old->rb_right, node);
254 }
255
256 node->rb_parent_color = old->rb_parent_color;
257 node->rb_left = old->rb_left;
258 ext2fs_rb_set_parent(old->rb_left, node);
259
260 goto color;
261 }
262
263 parent = ext2fs_rb_parent(node);
264 color = ext2fs_rb_color(node);
265
266 if (child)
267 ext2fs_rb_set_parent(child, parent);
268 if (parent)
269 {
270 if (parent->rb_left == node)
271 parent->rb_left = child;
272 else
273 parent->rb_right = child;
274 }
275 else
276 root->rb_node = child;
277
278 color:
279 if (color == RB_BLACK)
280 __rb_erase_color(child, parent, root);
281 }
282
ext2fs_rb_augment_path(struct rb_node * node,rb_augment_f func,void * data)283 static void ext2fs_rb_augment_path(struct rb_node *node, rb_augment_f func, void *data)
284 {
285 struct rb_node *parent;
286
287 up:
288 func(node, data);
289 parent = ext2fs_rb_parent(node);
290 if (!parent)
291 return;
292
293 if (node == parent->rb_left && parent->rb_right)
294 func(parent->rb_right, data);
295 else if (parent->rb_left)
296 func(parent->rb_left, data);
297
298 node = parent;
299 goto up;
300 }
301
302 /*
303 * after inserting @node into the tree, update the tree to account for
304 * both the new entry and any damage done by rebalance
305 */
ext2fs_rb_augment_insert(struct rb_node * node,rb_augment_f func,void * data)306 void ext2fs_rb_augment_insert(struct rb_node *node, rb_augment_f func, void *data)
307 {
308 if (node->rb_left)
309 node = node->rb_left;
310 else if (node->rb_right)
311 node = node->rb_right;
312
313 ext2fs_rb_augment_path(node, func, data);
314 }
315
316 /*
317 * before removing the node, find the deepest node on the rebalance path
318 * that will still be there after @node gets removed
319 */
ext2fs_rb_augment_erase_begin(struct rb_node * node)320 struct rb_node *ext2fs_rb_augment_erase_begin(struct rb_node *node)
321 {
322 struct rb_node *deepest;
323
324 if (!node->rb_right && !node->rb_left)
325 deepest = ext2fs_rb_parent(node);
326 else if (!node->rb_right)
327 deepest = node->rb_left;
328 else if (!node->rb_left)
329 deepest = node->rb_right;
330 else {
331 deepest = ext2fs_rb_next(node);
332 if (deepest->rb_right)
333 deepest = deepest->rb_right;
334 else if (ext2fs_rb_parent(deepest) != node)
335 deepest = ext2fs_rb_parent(deepest);
336 }
337
338 return deepest;
339 }
340
341 /*
342 * after removal, update the tree to account for the removed entry
343 * and any rebalance damage.
344 */
ext2fs_rb_augment_erase_end(struct rb_node * node,rb_augment_f func,void * data)345 void ext2fs_rb_augment_erase_end(struct rb_node *node, rb_augment_f func, void *data)
346 {
347 if (node)
348 ext2fs_rb_augment_path(node, func, data);
349 }
350
351 /*
352 * This function returns the first node (in sort order) of the tree.
353 */
ext2fs_rb_first(const struct rb_root * root)354 struct rb_node *ext2fs_rb_first(const struct rb_root *root)
355 {
356 struct rb_node *n;
357
358 n = root->rb_node;
359 if (!n)
360 return NULL;
361 while (n->rb_left)
362 n = n->rb_left;
363 return n;
364 }
365
ext2fs_rb_last(const struct rb_root * root)366 struct rb_node *ext2fs_rb_last(const struct rb_root *root)
367 {
368 struct rb_node *n;
369
370 n = root->rb_node;
371 if (!n)
372 return NULL;
373 while (n->rb_right)
374 n = n->rb_right;
375 return n;
376 }
377
ext2fs_rb_next(struct rb_node * node)378 struct rb_node *ext2fs_rb_next(struct rb_node *node)
379 {
380 struct rb_node *parent;
381
382 if (ext2fs_rb_parent(node) == node)
383 return NULL;
384
385 /* If we have a right-hand child, go down and then left as far
386 as we can. */
387 if (node->rb_right) {
388 node = node->rb_right;
389 while (node->rb_left)
390 node=node->rb_left;
391 return (struct rb_node *)node;
392 }
393
394 /* No right-hand children. Everything down and left is
395 smaller than us, so any 'next' node must be in the general
396 direction of our parent. Go up the tree; any time the
397 ancestor is a right-hand child of its parent, keep going
398 up. First time it's a left-hand child of its parent, said
399 parent is our 'next' node. */
400 while ((parent = ext2fs_rb_parent(node)) && node == parent->rb_right)
401 node = parent;
402
403 return parent;
404 }
405
ext2fs_rb_prev(struct rb_node * node)406 struct rb_node *ext2fs_rb_prev(struct rb_node *node)
407 {
408 struct rb_node *parent;
409
410 if (ext2fs_rb_parent(node) == node)
411 return NULL;
412
413 /* If we have a left-hand child, go down and then right as far
414 as we can. */
415 if (node->rb_left) {
416 node = node->rb_left;
417 while (node->rb_right)
418 node=node->rb_right;
419 return (struct rb_node *)node;
420 }
421
422 /* No left-hand children. Go up till we find an ancestor which
423 is a right-hand child of its parent */
424 while ((parent = ext2fs_rb_parent(node)) && node == parent->rb_left)
425 node = parent;
426
427 return parent;
428 }
429
ext2fs_rb_replace_node(struct rb_node * victim,struct rb_node * new,struct rb_root * root)430 void ext2fs_rb_replace_node(struct rb_node *victim, struct rb_node *new,
431 struct rb_root *root)
432 {
433 struct rb_node *parent = ext2fs_rb_parent(victim);
434
435 /* Set the surrounding nodes to point to the replacement */
436 if (parent) {
437 if (victim == parent->rb_left)
438 parent->rb_left = new;
439 else
440 parent->rb_right = new;
441 } else {
442 root->rb_node = new;
443 }
444 if (victim->rb_left)
445 ext2fs_rb_set_parent(victim->rb_left, new);
446 if (victim->rb_right)
447 ext2fs_rb_set_parent(victim->rb_right, new);
448
449 /* Copy the pointers/colour from the victim to the replacement */
450 *new = *victim;
451 }
452