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Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | Red Black Trees | |
3 | (C) 1999 Andrea Arcangeli <andrea@suse.de> | |
4 | (C) 2002 David Woodhouse <dwmw2@infradead.org> | |
46b6135a ML |
5 | (C) 2012 Michel Lespinasse <walken@google.com> |
6 | ||
1da177e4 LT |
7 | This program is free software; you can redistribute it and/or modify |
8 | it under the terms of the GNU General Public License as published by | |
9 | the Free Software Foundation; either version 2 of the License, or | |
10 | (at your option) any later version. | |
11 | ||
12 | This program is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | GNU General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU General Public License | |
18 | along with this program; if not, write to the Free Software | |
19 | Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
20 | ||
21 | linux/lib/rbtree.c | |
22 | */ | |
23 | ||
24 | #include <linux/rbtree.h> | |
8bc3bcc9 | 25 | #include <linux/export.h> |
1da177e4 | 26 | |
5bc9188a ML |
27 | /* |
28 | * red-black trees properties: http://en.wikipedia.org/wiki/Rbtree | |
29 | * | |
30 | * 1) A node is either red or black | |
31 | * 2) The root is black | |
32 | * 3) All leaves (NULL) are black | |
33 | * 4) Both children of every red node are black | |
34 | * 5) Every simple path from root to leaves contains the same number | |
35 | * of black nodes. | |
36 | * | |
37 | * 4 and 5 give the O(log n) guarantee, since 4 implies you cannot have two | |
38 | * consecutive red nodes in a path and every red node is therefore followed by | |
39 | * a black. So if B is the number of black nodes on every simple path (as per | |
40 | * 5), then the longest possible path due to 4 is 2B. | |
41 | * | |
42 | * We shall indicate color with case, where black nodes are uppercase and red | |
6280d235 ML |
43 | * nodes will be lowercase. Unknown color nodes shall be drawn as red within |
44 | * parentheses and have some accompanying text comment. | |
5bc9188a ML |
45 | */ |
46 | ||
bf7ad8ee ML |
47 | #define RB_RED 0 |
48 | #define RB_BLACK 1 | |
49 | ||
4f035ad6 ML |
50 | #define __rb_parent(pc) ((struct rb_node *)(pc & ~3)) |
51 | ||
52 | #define __rb_color(pc) ((pc) & 1) | |
53 | #define __rb_is_black(pc) __rb_color(pc) | |
54 | #define __rb_is_red(pc) (!__rb_color(pc)) | |
55 | #define rb_color(rb) __rb_color((rb)->__rb_parent_color) | |
56 | #define rb_is_red(rb) __rb_is_red((rb)->__rb_parent_color) | |
57 | #define rb_is_black(rb) __rb_is_black((rb)->__rb_parent_color) | |
bf7ad8ee | 58 | |
46b6135a ML |
59 | static inline void rb_set_black(struct rb_node *rb) |
60 | { | |
61 | rb->__rb_parent_color |= RB_BLACK; | |
62 | } | |
63 | ||
bf7ad8ee ML |
64 | static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p) |
65 | { | |
66 | rb->__rb_parent_color = rb_color(rb) | (unsigned long)p; | |
67 | } | |
bf7ad8ee | 68 | |
5bc9188a ML |
69 | static inline void rb_set_parent_color(struct rb_node *rb, |
70 | struct rb_node *p, int color) | |
71 | { | |
72 | rb->__rb_parent_color = (unsigned long)p | color; | |
73 | } | |
74 | ||
75 | static inline struct rb_node *rb_red_parent(struct rb_node *red) | |
76 | { | |
77 | return (struct rb_node *)red->__rb_parent_color; | |
78 | } | |
79 | ||
7abc704a ML |
80 | static inline void |
81 | __rb_change_child(struct rb_node *old, struct rb_node *new, | |
82 | struct rb_node *parent, struct rb_root *root) | |
83 | { | |
84 | if (parent) { | |
85 | if (parent->rb_left == old) | |
86 | parent->rb_left = new; | |
87 | else | |
88 | parent->rb_right = new; | |
89 | } else | |
90 | root->rb_node = new; | |
91 | } | |
92 | ||
5bc9188a ML |
93 | /* |
94 | * Helper function for rotations: | |
95 | * - old's parent and color get assigned to new | |
96 | * - old gets assigned new as a parent and 'color' as a color. | |
97 | */ | |
98 | static inline void | |
99 | __rb_rotate_set_parents(struct rb_node *old, struct rb_node *new, | |
100 | struct rb_root *root, int color) | |
101 | { | |
102 | struct rb_node *parent = rb_parent(old); | |
103 | new->__rb_parent_color = old->__rb_parent_color; | |
104 | rb_set_parent_color(old, new, color); | |
7abc704a | 105 | __rb_change_child(old, new, parent, root); |
5bc9188a ML |
106 | } |
107 | ||
1da177e4 LT |
108 | void rb_insert_color(struct rb_node *node, struct rb_root *root) |
109 | { | |
5bc9188a | 110 | struct rb_node *parent = rb_red_parent(node), *gparent, *tmp; |
1da177e4 | 111 | |
6d58452d ML |
112 | while (true) { |
113 | /* | |
114 | * Loop invariant: node is red | |
115 | * | |
116 | * If there is a black parent, we are done. | |
117 | * Otherwise, take some corrective action as we don't | |
118 | * want a red root or two consecutive red nodes. | |
119 | */ | |
6d58452d | 120 | if (!parent) { |
5bc9188a | 121 | rb_set_parent_color(node, NULL, RB_BLACK); |
6d58452d ML |
122 | break; |
123 | } else if (rb_is_black(parent)) | |
124 | break; | |
125 | ||
5bc9188a ML |
126 | gparent = rb_red_parent(parent); |
127 | ||
59633abf ML |
128 | tmp = gparent->rb_right; |
129 | if (parent != tmp) { /* parent == gparent->rb_left */ | |
5bc9188a ML |
130 | if (tmp && rb_is_red(tmp)) { |
131 | /* | |
132 | * Case 1 - color flips | |
133 | * | |
134 | * G g | |
135 | * / \ / \ | |
136 | * p u --> P U | |
137 | * / / | |
138 | * n N | |
139 | * | |
140 | * However, since g's parent might be red, and | |
141 | * 4) does not allow this, we need to recurse | |
142 | * at g. | |
143 | */ | |
144 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
145 | rb_set_parent_color(parent, gparent, RB_BLACK); | |
146 | node = gparent; | |
147 | parent = rb_parent(node); | |
148 | rb_set_parent_color(node, parent, RB_RED); | |
149 | continue; | |
1da177e4 LT |
150 | } |
151 | ||
59633abf ML |
152 | tmp = parent->rb_right; |
153 | if (node == tmp) { | |
5bc9188a ML |
154 | /* |
155 | * Case 2 - left rotate at parent | |
156 | * | |
157 | * G G | |
158 | * / \ / \ | |
159 | * p U --> n U | |
160 | * \ / | |
161 | * n p | |
162 | * | |
163 | * This still leaves us in violation of 4), the | |
164 | * continuation into Case 3 will fix that. | |
165 | */ | |
166 | parent->rb_right = tmp = node->rb_left; | |
167 | node->rb_left = parent; | |
168 | if (tmp) | |
169 | rb_set_parent_color(tmp, parent, | |
170 | RB_BLACK); | |
171 | rb_set_parent_color(parent, node, RB_RED); | |
1da177e4 | 172 | parent = node; |
59633abf | 173 | tmp = node->rb_right; |
1da177e4 LT |
174 | } |
175 | ||
5bc9188a ML |
176 | /* |
177 | * Case 3 - right rotate at gparent | |
178 | * | |
179 | * G P | |
180 | * / \ / \ | |
181 | * p U --> n g | |
182 | * / \ | |
183 | * n U | |
184 | */ | |
59633abf | 185 | gparent->rb_left = tmp; /* == parent->rb_right */ |
5bc9188a ML |
186 | parent->rb_right = gparent; |
187 | if (tmp) | |
188 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
189 | __rb_rotate_set_parents(gparent, parent, root, RB_RED); | |
1f052865 | 190 | break; |
1da177e4 | 191 | } else { |
5bc9188a ML |
192 | tmp = gparent->rb_left; |
193 | if (tmp && rb_is_red(tmp)) { | |
194 | /* Case 1 - color flips */ | |
195 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
196 | rb_set_parent_color(parent, gparent, RB_BLACK); | |
197 | node = gparent; | |
198 | parent = rb_parent(node); | |
199 | rb_set_parent_color(node, parent, RB_RED); | |
200 | continue; | |
1da177e4 LT |
201 | } |
202 | ||
59633abf ML |
203 | tmp = parent->rb_left; |
204 | if (node == tmp) { | |
5bc9188a ML |
205 | /* Case 2 - right rotate at parent */ |
206 | parent->rb_left = tmp = node->rb_right; | |
207 | node->rb_right = parent; | |
208 | if (tmp) | |
209 | rb_set_parent_color(tmp, parent, | |
210 | RB_BLACK); | |
211 | rb_set_parent_color(parent, node, RB_RED); | |
1da177e4 | 212 | parent = node; |
59633abf | 213 | tmp = node->rb_left; |
1da177e4 LT |
214 | } |
215 | ||
5bc9188a | 216 | /* Case 3 - left rotate at gparent */ |
59633abf | 217 | gparent->rb_right = tmp; /* == parent->rb_left */ |
5bc9188a ML |
218 | parent->rb_left = gparent; |
219 | if (tmp) | |
220 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
221 | __rb_rotate_set_parents(gparent, parent, root, RB_RED); | |
1f052865 | 222 | break; |
1da177e4 LT |
223 | } |
224 | } | |
1da177e4 LT |
225 | } |
226 | EXPORT_SYMBOL(rb_insert_color); | |
227 | ||
46b6135a | 228 | static void __rb_erase_color(struct rb_node *parent, struct rb_root *root) |
1da177e4 | 229 | { |
46b6135a | 230 | struct rb_node *node = NULL, *sibling, *tmp1, *tmp2; |
1da177e4 | 231 | |
d6ff1273 ML |
232 | while (true) { |
233 | /* | |
46b6135a ML |
234 | * Loop invariants: |
235 | * - node is black (or NULL on first iteration) | |
236 | * - node is not the root (parent is not NULL) | |
237 | * - All leaf paths going through parent and node have a | |
238 | * black node count that is 1 lower than other leaf paths. | |
d6ff1273 | 239 | */ |
59633abf ML |
240 | sibling = parent->rb_right; |
241 | if (node != sibling) { /* node == parent->rb_left */ | |
6280d235 ML |
242 | if (rb_is_red(sibling)) { |
243 | /* | |
244 | * Case 1 - left rotate at parent | |
245 | * | |
246 | * P S | |
247 | * / \ / \ | |
248 | * N s --> p Sr | |
249 | * / \ / \ | |
250 | * Sl Sr N Sl | |
251 | */ | |
252 | parent->rb_right = tmp1 = sibling->rb_left; | |
253 | sibling->rb_left = parent; | |
254 | rb_set_parent_color(tmp1, parent, RB_BLACK); | |
255 | __rb_rotate_set_parents(parent, sibling, root, | |
256 | RB_RED); | |
257 | sibling = tmp1; | |
1da177e4 | 258 | } |
6280d235 ML |
259 | tmp1 = sibling->rb_right; |
260 | if (!tmp1 || rb_is_black(tmp1)) { | |
261 | tmp2 = sibling->rb_left; | |
262 | if (!tmp2 || rb_is_black(tmp2)) { | |
263 | /* | |
264 | * Case 2 - sibling color flip | |
265 | * (p could be either color here) | |
266 | * | |
267 | * (p) (p) | |
268 | * / \ / \ | |
269 | * N S --> N s | |
270 | * / \ / \ | |
271 | * Sl Sr Sl Sr | |
272 | * | |
46b6135a ML |
273 | * This leaves us violating 5) which |
274 | * can be fixed by flipping p to black | |
275 | * if it was red, or by recursing at p. | |
276 | * p is red when coming from Case 1. | |
6280d235 ML |
277 | */ |
278 | rb_set_parent_color(sibling, parent, | |
279 | RB_RED); | |
46b6135a ML |
280 | if (rb_is_red(parent)) |
281 | rb_set_black(parent); | |
282 | else { | |
283 | node = parent; | |
284 | parent = rb_parent(node); | |
285 | if (parent) | |
286 | continue; | |
287 | } | |
288 | break; | |
1da177e4 | 289 | } |
6280d235 ML |
290 | /* |
291 | * Case 3 - right rotate at sibling | |
292 | * (p could be either color here) | |
293 | * | |
294 | * (p) (p) | |
295 | * / \ / \ | |
296 | * N S --> N Sl | |
297 | * / \ \ | |
298 | * sl Sr s | |
299 | * \ | |
300 | * Sr | |
301 | */ | |
302 | sibling->rb_left = tmp1 = tmp2->rb_right; | |
303 | tmp2->rb_right = sibling; | |
304 | parent->rb_right = tmp2; | |
305 | if (tmp1) | |
306 | rb_set_parent_color(tmp1, sibling, | |
307 | RB_BLACK); | |
308 | tmp1 = sibling; | |
309 | sibling = tmp2; | |
1da177e4 | 310 | } |
6280d235 ML |
311 | /* |
312 | * Case 4 - left rotate at parent + color flips | |
313 | * (p and sl could be either color here. | |
314 | * After rotation, p becomes black, s acquires | |
315 | * p's color, and sl keeps its color) | |
316 | * | |
317 | * (p) (s) | |
318 | * / \ / \ | |
319 | * N S --> P Sr | |
320 | * / \ / \ | |
321 | * (sl) sr N (sl) | |
322 | */ | |
323 | parent->rb_right = tmp2 = sibling->rb_left; | |
324 | sibling->rb_left = parent; | |
325 | rb_set_parent_color(tmp1, sibling, RB_BLACK); | |
326 | if (tmp2) | |
327 | rb_set_parent(tmp2, parent); | |
328 | __rb_rotate_set_parents(parent, sibling, root, | |
329 | RB_BLACK); | |
e125d147 | 330 | break; |
d6ff1273 | 331 | } else { |
6280d235 ML |
332 | sibling = parent->rb_left; |
333 | if (rb_is_red(sibling)) { | |
334 | /* Case 1 - right rotate at parent */ | |
335 | parent->rb_left = tmp1 = sibling->rb_right; | |
336 | sibling->rb_right = parent; | |
337 | rb_set_parent_color(tmp1, parent, RB_BLACK); | |
338 | __rb_rotate_set_parents(parent, sibling, root, | |
339 | RB_RED); | |
340 | sibling = tmp1; | |
1da177e4 | 341 | } |
6280d235 ML |
342 | tmp1 = sibling->rb_left; |
343 | if (!tmp1 || rb_is_black(tmp1)) { | |
344 | tmp2 = sibling->rb_right; | |
345 | if (!tmp2 || rb_is_black(tmp2)) { | |
346 | /* Case 2 - sibling color flip */ | |
347 | rb_set_parent_color(sibling, parent, | |
348 | RB_RED); | |
46b6135a ML |
349 | if (rb_is_red(parent)) |
350 | rb_set_black(parent); | |
351 | else { | |
352 | node = parent; | |
353 | parent = rb_parent(node); | |
354 | if (parent) | |
355 | continue; | |
356 | } | |
357 | break; | |
1da177e4 | 358 | } |
6280d235 ML |
359 | /* Case 3 - right rotate at sibling */ |
360 | sibling->rb_right = tmp1 = tmp2->rb_left; | |
361 | tmp2->rb_left = sibling; | |
362 | parent->rb_left = tmp2; | |
363 | if (tmp1) | |
364 | rb_set_parent_color(tmp1, sibling, | |
365 | RB_BLACK); | |
366 | tmp1 = sibling; | |
367 | sibling = tmp2; | |
1da177e4 | 368 | } |
6280d235 ML |
369 | /* Case 4 - left rotate at parent + color flips */ |
370 | parent->rb_left = tmp2 = sibling->rb_right; | |
371 | sibling->rb_right = parent; | |
372 | rb_set_parent_color(tmp1, sibling, RB_BLACK); | |
373 | if (tmp2) | |
374 | rb_set_parent(tmp2, parent); | |
375 | __rb_rotate_set_parents(parent, sibling, root, | |
376 | RB_BLACK); | |
e125d147 | 377 | break; |
1da177e4 LT |
378 | } |
379 | } | |
1da177e4 LT |
380 | } |
381 | ||
382 | void rb_erase(struct rb_node *node, struct rb_root *root) | |
383 | { | |
60670b80 | 384 | struct rb_node *child = node->rb_right, *tmp = node->rb_left; |
46b6135a | 385 | struct rb_node *parent, *rebalance; |
4f035ad6 | 386 | unsigned long pc; |
1da177e4 | 387 | |
60670b80 | 388 | if (!tmp) { |
46b6135a ML |
389 | /* |
390 | * Case 1: node to erase has no more than 1 child (easy!) | |
391 | * | |
392 | * Note that if there is one child it must be red due to 5) | |
393 | * and node must be black due to 4). We adjust colors locally | |
394 | * so as to bypass __rb_erase_color() later on. | |
395 | */ | |
4f035ad6 ML |
396 | pc = node->__rb_parent_color; |
397 | parent = __rb_parent(pc); | |
60670b80 | 398 | __rb_change_child(node, child, parent, root); |
46b6135a | 399 | if (child) { |
4f035ad6 | 400 | child->__rb_parent_color = pc; |
46b6135a | 401 | rebalance = NULL; |
4f035ad6 ML |
402 | } else |
403 | rebalance = __rb_is_black(pc) ? parent : NULL; | |
60670b80 ML |
404 | } else if (!child) { |
405 | /* Still case 1, but this time the child is node->rb_left */ | |
4f035ad6 ML |
406 | tmp->__rb_parent_color = pc = node->__rb_parent_color; |
407 | parent = __rb_parent(pc); | |
46b6135a | 408 | __rb_change_child(node, tmp, parent, root); |
46b6135a | 409 | rebalance = NULL; |
60670b80 | 410 | } else { |
4f035ad6 ML |
411 | struct rb_node *successor = child, *child2; |
412 | tmp = child->rb_left; | |
413 | if (!tmp) { | |
414 | /* | |
415 | * Case 2: node's successor is its right child | |
416 | * | |
417 | * (n) (s) | |
418 | * / \ / \ | |
419 | * (x) (s) -> (x) (c) | |
420 | * \ | |
421 | * (c) | |
422 | */ | |
423 | parent = child; | |
424 | child2 = child->rb_right; | |
4c601178 | 425 | } else { |
4f035ad6 ML |
426 | /* |
427 | * Case 3: node's successor is leftmost under | |
428 | * node's right child subtree | |
429 | * | |
430 | * (n) (s) | |
431 | * / \ / \ | |
432 | * (x) (y) -> (x) (y) | |
433 | * / / | |
434 | * (p) (p) | |
435 | * / / | |
436 | * (s) (c) | |
437 | * \ | |
438 | * (c) | |
439 | */ | |
440 | do { | |
441 | parent = successor; | |
442 | successor = tmp; | |
443 | tmp = tmp->rb_left; | |
444 | } while (tmp); | |
445 | parent->rb_left = child2 = successor->rb_right; | |
446 | successor->rb_right = child; | |
447 | rb_set_parent(child, successor); | |
4c601178 | 448 | } |
1975e593 | 449 | |
4f035ad6 ML |
450 | successor->rb_left = tmp = node->rb_left; |
451 | rb_set_parent(tmp, successor); | |
452 | ||
453 | pc = node->__rb_parent_color; | |
454 | tmp = __rb_parent(pc); | |
455 | __rb_change_child(node, successor, tmp, root); | |
456 | if (child2) { | |
457 | successor->__rb_parent_color = pc; | |
458 | rb_set_parent_color(child2, parent, RB_BLACK); | |
46b6135a ML |
459 | rebalance = NULL; |
460 | } else { | |
4f035ad6 ML |
461 | unsigned long pc2 = successor->__rb_parent_color; |
462 | successor->__rb_parent_color = pc; | |
463 | rebalance = __rb_is_black(pc2) ? parent : NULL; | |
46b6135a | 464 | } |
1da177e4 LT |
465 | } |
466 | ||
46b6135a ML |
467 | if (rebalance) |
468 | __rb_erase_color(rebalance, root); | |
1da177e4 LT |
469 | } |
470 | EXPORT_SYMBOL(rb_erase); | |
471 | ||
b945d6b2 PZ |
472 | static void rb_augment_path(struct rb_node *node, rb_augment_f func, void *data) |
473 | { | |
474 | struct rb_node *parent; | |
475 | ||
476 | up: | |
477 | func(node, data); | |
478 | parent = rb_parent(node); | |
479 | if (!parent) | |
480 | return; | |
481 | ||
482 | if (node == parent->rb_left && parent->rb_right) | |
483 | func(parent->rb_right, data); | |
484 | else if (parent->rb_left) | |
485 | func(parent->rb_left, data); | |
486 | ||
487 | node = parent; | |
488 | goto up; | |
489 | } | |
490 | ||
491 | /* | |
492 | * after inserting @node into the tree, update the tree to account for | |
493 | * both the new entry and any damage done by rebalance | |
494 | */ | |
495 | void rb_augment_insert(struct rb_node *node, rb_augment_f func, void *data) | |
496 | { | |
497 | if (node->rb_left) | |
498 | node = node->rb_left; | |
499 | else if (node->rb_right) | |
500 | node = node->rb_right; | |
501 | ||
502 | rb_augment_path(node, func, data); | |
503 | } | |
0b6bb66d | 504 | EXPORT_SYMBOL(rb_augment_insert); |
b945d6b2 PZ |
505 | |
506 | /* | |
507 | * before removing the node, find the deepest node on the rebalance path | |
508 | * that will still be there after @node gets removed | |
509 | */ | |
510 | struct rb_node *rb_augment_erase_begin(struct rb_node *node) | |
511 | { | |
512 | struct rb_node *deepest; | |
513 | ||
514 | if (!node->rb_right && !node->rb_left) | |
515 | deepest = rb_parent(node); | |
516 | else if (!node->rb_right) | |
517 | deepest = node->rb_left; | |
518 | else if (!node->rb_left) | |
519 | deepest = node->rb_right; | |
520 | else { | |
521 | deepest = rb_next(node); | |
522 | if (deepest->rb_right) | |
523 | deepest = deepest->rb_right; | |
524 | else if (rb_parent(deepest) != node) | |
525 | deepest = rb_parent(deepest); | |
526 | } | |
527 | ||
528 | return deepest; | |
529 | } | |
0b6bb66d | 530 | EXPORT_SYMBOL(rb_augment_erase_begin); |
b945d6b2 PZ |
531 | |
532 | /* | |
533 | * after removal, update the tree to account for the removed entry | |
534 | * and any rebalance damage. | |
535 | */ | |
536 | void rb_augment_erase_end(struct rb_node *node, rb_augment_f func, void *data) | |
537 | { | |
538 | if (node) | |
539 | rb_augment_path(node, func, data); | |
540 | } | |
0b6bb66d | 541 | EXPORT_SYMBOL(rb_augment_erase_end); |
b945d6b2 | 542 | |
1da177e4 LT |
543 | /* |
544 | * This function returns the first node (in sort order) of the tree. | |
545 | */ | |
f4b477c4 | 546 | struct rb_node *rb_first(const struct rb_root *root) |
1da177e4 LT |
547 | { |
548 | struct rb_node *n; | |
549 | ||
550 | n = root->rb_node; | |
551 | if (!n) | |
552 | return NULL; | |
553 | while (n->rb_left) | |
554 | n = n->rb_left; | |
555 | return n; | |
556 | } | |
557 | EXPORT_SYMBOL(rb_first); | |
558 | ||
f4b477c4 | 559 | struct rb_node *rb_last(const struct rb_root *root) |
1da177e4 LT |
560 | { |
561 | struct rb_node *n; | |
562 | ||
563 | n = root->rb_node; | |
564 | if (!n) | |
565 | return NULL; | |
566 | while (n->rb_right) | |
567 | n = n->rb_right; | |
568 | return n; | |
569 | } | |
570 | EXPORT_SYMBOL(rb_last); | |
571 | ||
f4b477c4 | 572 | struct rb_node *rb_next(const struct rb_node *node) |
1da177e4 | 573 | { |
55a98102 DW |
574 | struct rb_node *parent; |
575 | ||
4c199a93 | 576 | if (RB_EMPTY_NODE(node)) |
10fd48f2 JA |
577 | return NULL; |
578 | ||
7ce6ff9e ML |
579 | /* |
580 | * If we have a right-hand child, go down and then left as far | |
581 | * as we can. | |
582 | */ | |
1da177e4 LT |
583 | if (node->rb_right) { |
584 | node = node->rb_right; | |
585 | while (node->rb_left) | |
586 | node=node->rb_left; | |
f4b477c4 | 587 | return (struct rb_node *)node; |
1da177e4 LT |
588 | } |
589 | ||
7ce6ff9e ML |
590 | /* |
591 | * No right-hand children. Everything down and left is smaller than us, | |
592 | * so any 'next' node must be in the general direction of our parent. | |
593 | * Go up the tree; any time the ancestor is a right-hand child of its | |
594 | * parent, keep going up. First time it's a left-hand child of its | |
595 | * parent, said parent is our 'next' node. | |
596 | */ | |
55a98102 DW |
597 | while ((parent = rb_parent(node)) && node == parent->rb_right) |
598 | node = parent; | |
1da177e4 | 599 | |
55a98102 | 600 | return parent; |
1da177e4 LT |
601 | } |
602 | EXPORT_SYMBOL(rb_next); | |
603 | ||
f4b477c4 | 604 | struct rb_node *rb_prev(const struct rb_node *node) |
1da177e4 | 605 | { |
55a98102 DW |
606 | struct rb_node *parent; |
607 | ||
4c199a93 | 608 | if (RB_EMPTY_NODE(node)) |
10fd48f2 JA |
609 | return NULL; |
610 | ||
7ce6ff9e ML |
611 | /* |
612 | * If we have a left-hand child, go down and then right as far | |
613 | * as we can. | |
614 | */ | |
1da177e4 LT |
615 | if (node->rb_left) { |
616 | node = node->rb_left; | |
617 | while (node->rb_right) | |
618 | node=node->rb_right; | |
f4b477c4 | 619 | return (struct rb_node *)node; |
1da177e4 LT |
620 | } |
621 | ||
7ce6ff9e ML |
622 | /* |
623 | * No left-hand children. Go up till we find an ancestor which | |
624 | * is a right-hand child of its parent. | |
625 | */ | |
55a98102 DW |
626 | while ((parent = rb_parent(node)) && node == parent->rb_left) |
627 | node = parent; | |
1da177e4 | 628 | |
55a98102 | 629 | return parent; |
1da177e4 LT |
630 | } |
631 | EXPORT_SYMBOL(rb_prev); | |
632 | ||
633 | void rb_replace_node(struct rb_node *victim, struct rb_node *new, | |
634 | struct rb_root *root) | |
635 | { | |
55a98102 | 636 | struct rb_node *parent = rb_parent(victim); |
1da177e4 LT |
637 | |
638 | /* Set the surrounding nodes to point to the replacement */ | |
7abc704a | 639 | __rb_change_child(victim, new, parent, root); |
1da177e4 | 640 | if (victim->rb_left) |
55a98102 | 641 | rb_set_parent(victim->rb_left, new); |
1da177e4 | 642 | if (victim->rb_right) |
55a98102 | 643 | rb_set_parent(victim->rb_right, new); |
1da177e4 LT |
644 | |
645 | /* Copy the pointers/colour from the victim to the replacement */ | |
646 | *new = *victim; | |
647 | } | |
648 | EXPORT_SYMBOL(rb_replace_node); |