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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 | ||
50 | #define rb_color(r) ((r)->__rb_parent_color & 1) | |
51 | #define rb_is_red(r) (!rb_color(r)) | |
52 | #define rb_is_black(r) rb_color(r) | |
bf7ad8ee | 53 | |
46b6135a ML |
54 | static inline void rb_set_black(struct rb_node *rb) |
55 | { | |
56 | rb->__rb_parent_color |= RB_BLACK; | |
57 | } | |
58 | ||
bf7ad8ee ML |
59 | static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p) |
60 | { | |
61 | rb->__rb_parent_color = rb_color(rb) | (unsigned long)p; | |
62 | } | |
bf7ad8ee | 63 | |
5bc9188a ML |
64 | static inline void rb_set_parent_color(struct rb_node *rb, |
65 | struct rb_node *p, int color) | |
66 | { | |
67 | rb->__rb_parent_color = (unsigned long)p | color; | |
68 | } | |
69 | ||
70 | static inline struct rb_node *rb_red_parent(struct rb_node *red) | |
71 | { | |
72 | return (struct rb_node *)red->__rb_parent_color; | |
73 | } | |
74 | ||
7abc704a ML |
75 | static inline void |
76 | __rb_change_child(struct rb_node *old, struct rb_node *new, | |
77 | struct rb_node *parent, struct rb_root *root) | |
78 | { | |
79 | if (parent) { | |
80 | if (parent->rb_left == old) | |
81 | parent->rb_left = new; | |
82 | else | |
83 | parent->rb_right = new; | |
84 | } else | |
85 | root->rb_node = new; | |
86 | } | |
87 | ||
5bc9188a ML |
88 | /* |
89 | * Helper function for rotations: | |
90 | * - old's parent and color get assigned to new | |
91 | * - old gets assigned new as a parent and 'color' as a color. | |
92 | */ | |
93 | static inline void | |
94 | __rb_rotate_set_parents(struct rb_node *old, struct rb_node *new, | |
95 | struct rb_root *root, int color) | |
96 | { | |
97 | struct rb_node *parent = rb_parent(old); | |
98 | new->__rb_parent_color = old->__rb_parent_color; | |
99 | rb_set_parent_color(old, new, color); | |
7abc704a | 100 | __rb_change_child(old, new, parent, root); |
5bc9188a ML |
101 | } |
102 | ||
1da177e4 LT |
103 | void rb_insert_color(struct rb_node *node, struct rb_root *root) |
104 | { | |
5bc9188a | 105 | struct rb_node *parent = rb_red_parent(node), *gparent, *tmp; |
1da177e4 | 106 | |
6d58452d ML |
107 | while (true) { |
108 | /* | |
109 | * Loop invariant: node is red | |
110 | * | |
111 | * If there is a black parent, we are done. | |
112 | * Otherwise, take some corrective action as we don't | |
113 | * want a red root or two consecutive red nodes. | |
114 | */ | |
6d58452d | 115 | if (!parent) { |
5bc9188a | 116 | rb_set_parent_color(node, NULL, RB_BLACK); |
6d58452d ML |
117 | break; |
118 | } else if (rb_is_black(parent)) | |
119 | break; | |
120 | ||
5bc9188a ML |
121 | gparent = rb_red_parent(parent); |
122 | ||
59633abf ML |
123 | tmp = gparent->rb_right; |
124 | if (parent != tmp) { /* parent == gparent->rb_left */ | |
5bc9188a ML |
125 | if (tmp && rb_is_red(tmp)) { |
126 | /* | |
127 | * Case 1 - color flips | |
128 | * | |
129 | * G g | |
130 | * / \ / \ | |
131 | * p u --> P U | |
132 | * / / | |
133 | * n N | |
134 | * | |
135 | * However, since g's parent might be red, and | |
136 | * 4) does not allow this, we need to recurse | |
137 | * at g. | |
138 | */ | |
139 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
140 | rb_set_parent_color(parent, gparent, RB_BLACK); | |
141 | node = gparent; | |
142 | parent = rb_parent(node); | |
143 | rb_set_parent_color(node, parent, RB_RED); | |
144 | continue; | |
1da177e4 LT |
145 | } |
146 | ||
59633abf ML |
147 | tmp = parent->rb_right; |
148 | if (node == tmp) { | |
5bc9188a ML |
149 | /* |
150 | * Case 2 - left rotate at parent | |
151 | * | |
152 | * G G | |
153 | * / \ / \ | |
154 | * p U --> n U | |
155 | * \ / | |
156 | * n p | |
157 | * | |
158 | * This still leaves us in violation of 4), the | |
159 | * continuation into Case 3 will fix that. | |
160 | */ | |
161 | parent->rb_right = tmp = node->rb_left; | |
162 | node->rb_left = parent; | |
163 | if (tmp) | |
164 | rb_set_parent_color(tmp, parent, | |
165 | RB_BLACK); | |
166 | rb_set_parent_color(parent, node, RB_RED); | |
1da177e4 | 167 | parent = node; |
59633abf | 168 | tmp = node->rb_right; |
1da177e4 LT |
169 | } |
170 | ||
5bc9188a ML |
171 | /* |
172 | * Case 3 - right rotate at gparent | |
173 | * | |
174 | * G P | |
175 | * / \ / \ | |
176 | * p U --> n g | |
177 | * / \ | |
178 | * n U | |
179 | */ | |
59633abf | 180 | gparent->rb_left = tmp; /* == parent->rb_right */ |
5bc9188a ML |
181 | parent->rb_right = gparent; |
182 | if (tmp) | |
183 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
184 | __rb_rotate_set_parents(gparent, parent, root, RB_RED); | |
1f052865 | 185 | break; |
1da177e4 | 186 | } else { |
5bc9188a ML |
187 | tmp = gparent->rb_left; |
188 | if (tmp && rb_is_red(tmp)) { | |
189 | /* Case 1 - color flips */ | |
190 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
191 | rb_set_parent_color(parent, gparent, RB_BLACK); | |
192 | node = gparent; | |
193 | parent = rb_parent(node); | |
194 | rb_set_parent_color(node, parent, RB_RED); | |
195 | continue; | |
1da177e4 LT |
196 | } |
197 | ||
59633abf ML |
198 | tmp = parent->rb_left; |
199 | if (node == tmp) { | |
5bc9188a ML |
200 | /* Case 2 - right rotate at parent */ |
201 | parent->rb_left = tmp = node->rb_right; | |
202 | node->rb_right = parent; | |
203 | if (tmp) | |
204 | rb_set_parent_color(tmp, parent, | |
205 | RB_BLACK); | |
206 | rb_set_parent_color(parent, node, RB_RED); | |
1da177e4 | 207 | parent = node; |
59633abf | 208 | tmp = node->rb_left; |
1da177e4 LT |
209 | } |
210 | ||
5bc9188a | 211 | /* Case 3 - left rotate at gparent */ |
59633abf | 212 | gparent->rb_right = tmp; /* == parent->rb_left */ |
5bc9188a ML |
213 | parent->rb_left = gparent; |
214 | if (tmp) | |
215 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
216 | __rb_rotate_set_parents(gparent, parent, root, RB_RED); | |
1f052865 | 217 | break; |
1da177e4 LT |
218 | } |
219 | } | |
1da177e4 LT |
220 | } |
221 | EXPORT_SYMBOL(rb_insert_color); | |
222 | ||
46b6135a | 223 | static void __rb_erase_color(struct rb_node *parent, struct rb_root *root) |
1da177e4 | 224 | { |
46b6135a | 225 | struct rb_node *node = NULL, *sibling, *tmp1, *tmp2; |
1da177e4 | 226 | |
d6ff1273 ML |
227 | while (true) { |
228 | /* | |
46b6135a ML |
229 | * Loop invariants: |
230 | * - node is black (or NULL on first iteration) | |
231 | * - node is not the root (parent is not NULL) | |
232 | * - All leaf paths going through parent and node have a | |
233 | * black node count that is 1 lower than other leaf paths. | |
d6ff1273 | 234 | */ |
59633abf ML |
235 | sibling = parent->rb_right; |
236 | if (node != sibling) { /* node == parent->rb_left */ | |
6280d235 ML |
237 | if (rb_is_red(sibling)) { |
238 | /* | |
239 | * Case 1 - left rotate at parent | |
240 | * | |
241 | * P S | |
242 | * / \ / \ | |
243 | * N s --> p Sr | |
244 | * / \ / \ | |
245 | * Sl Sr N Sl | |
246 | */ | |
247 | parent->rb_right = tmp1 = sibling->rb_left; | |
248 | sibling->rb_left = parent; | |
249 | rb_set_parent_color(tmp1, parent, RB_BLACK); | |
250 | __rb_rotate_set_parents(parent, sibling, root, | |
251 | RB_RED); | |
252 | sibling = tmp1; | |
1da177e4 | 253 | } |
6280d235 ML |
254 | tmp1 = sibling->rb_right; |
255 | if (!tmp1 || rb_is_black(tmp1)) { | |
256 | tmp2 = sibling->rb_left; | |
257 | if (!tmp2 || rb_is_black(tmp2)) { | |
258 | /* | |
259 | * Case 2 - sibling color flip | |
260 | * (p could be either color here) | |
261 | * | |
262 | * (p) (p) | |
263 | * / \ / \ | |
264 | * N S --> N s | |
265 | * / \ / \ | |
266 | * Sl Sr Sl Sr | |
267 | * | |
46b6135a ML |
268 | * This leaves us violating 5) which |
269 | * can be fixed by flipping p to black | |
270 | * if it was red, or by recursing at p. | |
271 | * p is red when coming from Case 1. | |
6280d235 ML |
272 | */ |
273 | rb_set_parent_color(sibling, parent, | |
274 | RB_RED); | |
46b6135a ML |
275 | if (rb_is_red(parent)) |
276 | rb_set_black(parent); | |
277 | else { | |
278 | node = parent; | |
279 | parent = rb_parent(node); | |
280 | if (parent) | |
281 | continue; | |
282 | } | |
283 | break; | |
1da177e4 | 284 | } |
6280d235 ML |
285 | /* |
286 | * Case 3 - right rotate at sibling | |
287 | * (p could be either color here) | |
288 | * | |
289 | * (p) (p) | |
290 | * / \ / \ | |
291 | * N S --> N Sl | |
292 | * / \ \ | |
293 | * sl Sr s | |
294 | * \ | |
295 | * Sr | |
296 | */ | |
297 | sibling->rb_left = tmp1 = tmp2->rb_right; | |
298 | tmp2->rb_right = sibling; | |
299 | parent->rb_right = tmp2; | |
300 | if (tmp1) | |
301 | rb_set_parent_color(tmp1, sibling, | |
302 | RB_BLACK); | |
303 | tmp1 = sibling; | |
304 | sibling = tmp2; | |
1da177e4 | 305 | } |
6280d235 ML |
306 | /* |
307 | * Case 4 - left rotate at parent + color flips | |
308 | * (p and sl could be either color here. | |
309 | * After rotation, p becomes black, s acquires | |
310 | * p's color, and sl keeps its color) | |
311 | * | |
312 | * (p) (s) | |
313 | * / \ / \ | |
314 | * N S --> P Sr | |
315 | * / \ / \ | |
316 | * (sl) sr N (sl) | |
317 | */ | |
318 | parent->rb_right = tmp2 = sibling->rb_left; | |
319 | sibling->rb_left = parent; | |
320 | rb_set_parent_color(tmp1, sibling, RB_BLACK); | |
321 | if (tmp2) | |
322 | rb_set_parent(tmp2, parent); | |
323 | __rb_rotate_set_parents(parent, sibling, root, | |
324 | RB_BLACK); | |
e125d147 | 325 | break; |
d6ff1273 | 326 | } else { |
6280d235 ML |
327 | sibling = parent->rb_left; |
328 | if (rb_is_red(sibling)) { | |
329 | /* Case 1 - right rotate at parent */ | |
330 | parent->rb_left = tmp1 = sibling->rb_right; | |
331 | sibling->rb_right = parent; | |
332 | rb_set_parent_color(tmp1, parent, RB_BLACK); | |
333 | __rb_rotate_set_parents(parent, sibling, root, | |
334 | RB_RED); | |
335 | sibling = tmp1; | |
1da177e4 | 336 | } |
6280d235 ML |
337 | tmp1 = sibling->rb_left; |
338 | if (!tmp1 || rb_is_black(tmp1)) { | |
339 | tmp2 = sibling->rb_right; | |
340 | if (!tmp2 || rb_is_black(tmp2)) { | |
341 | /* Case 2 - sibling color flip */ | |
342 | rb_set_parent_color(sibling, parent, | |
343 | RB_RED); | |
46b6135a ML |
344 | if (rb_is_red(parent)) |
345 | rb_set_black(parent); | |
346 | else { | |
347 | node = parent; | |
348 | parent = rb_parent(node); | |
349 | if (parent) | |
350 | continue; | |
351 | } | |
352 | break; | |
1da177e4 | 353 | } |
6280d235 ML |
354 | /* Case 3 - right rotate at sibling */ |
355 | sibling->rb_right = tmp1 = tmp2->rb_left; | |
356 | tmp2->rb_left = sibling; | |
357 | parent->rb_left = tmp2; | |
358 | if (tmp1) | |
359 | rb_set_parent_color(tmp1, sibling, | |
360 | RB_BLACK); | |
361 | tmp1 = sibling; | |
362 | sibling = tmp2; | |
1da177e4 | 363 | } |
6280d235 ML |
364 | /* Case 4 - left rotate at parent + color flips */ |
365 | parent->rb_left = tmp2 = sibling->rb_right; | |
366 | sibling->rb_right = parent; | |
367 | rb_set_parent_color(tmp1, sibling, RB_BLACK); | |
368 | if (tmp2) | |
369 | rb_set_parent(tmp2, parent); | |
370 | __rb_rotate_set_parents(parent, sibling, root, | |
371 | RB_BLACK); | |
e125d147 | 372 | break; |
1da177e4 LT |
373 | } |
374 | } | |
1da177e4 LT |
375 | } |
376 | ||
377 | void rb_erase(struct rb_node *node, struct rb_root *root) | |
378 | { | |
60670b80 | 379 | struct rb_node *child = node->rb_right, *tmp = node->rb_left; |
46b6135a | 380 | struct rb_node *parent, *rebalance; |
1da177e4 | 381 | |
60670b80 | 382 | if (!tmp) { |
46b6135a ML |
383 | /* |
384 | * Case 1: node to erase has no more than 1 child (easy!) | |
385 | * | |
386 | * Note that if there is one child it must be red due to 5) | |
387 | * and node must be black due to 4). We adjust colors locally | |
388 | * so as to bypass __rb_erase_color() later on. | |
389 | */ | |
60670b80 ML |
390 | |
391 | parent = rb_parent(node); | |
60670b80 | 392 | __rb_change_child(node, child, parent, root); |
46b6135a ML |
393 | if (child) { |
394 | rb_set_parent_color(child, parent, RB_BLACK); | |
395 | rebalance = NULL; | |
396 | } else { | |
397 | rebalance = rb_is_black(node) ? parent : NULL; | |
398 | } | |
60670b80 ML |
399 | } else if (!child) { |
400 | /* Still case 1, but this time the child is node->rb_left */ | |
46b6135a ML |
401 | parent = rb_parent(node); |
402 | __rb_change_child(node, tmp, parent, root); | |
403 | rb_set_parent_color(tmp, parent, RB_BLACK); | |
404 | rebalance = NULL; | |
60670b80 | 405 | } else { |
1da177e4 LT |
406 | struct rb_node *old = node, *left; |
407 | ||
60670b80 | 408 | node = child; |
1da177e4 LT |
409 | while ((left = node->rb_left) != NULL) |
410 | node = left; | |
16c047ad | 411 | |
7abc704a | 412 | __rb_change_child(old, node, rb_parent(old), root); |
16c047ad | 413 | |
1da177e4 | 414 | child = node->rb_right; |
55a98102 | 415 | parent = rb_parent(node); |
1da177e4 | 416 | |
55a98102 | 417 | if (parent == old) { |
1da177e4 | 418 | parent = node; |
4c601178 | 419 | } else { |
1975e593 | 420 | parent->rb_left = child; |
4b324126 WS |
421 | |
422 | node->rb_right = old->rb_right; | |
423 | rb_set_parent(old->rb_right, node); | |
4c601178 | 424 | } |
1975e593 | 425 | |
46b6135a ML |
426 | if (child) { |
427 | rb_set_parent_color(child, parent, RB_BLACK); | |
428 | rebalance = NULL; | |
429 | } else { | |
430 | rebalance = rb_is_black(node) ? parent : NULL; | |
431 | } | |
bf7ad8ee | 432 | node->__rb_parent_color = old->__rb_parent_color; |
1da177e4 | 433 | node->rb_left = old->rb_left; |
55a98102 | 434 | rb_set_parent(old->rb_left, node); |
1da177e4 LT |
435 | } |
436 | ||
46b6135a ML |
437 | if (rebalance) |
438 | __rb_erase_color(rebalance, root); | |
1da177e4 LT |
439 | } |
440 | EXPORT_SYMBOL(rb_erase); | |
441 | ||
b945d6b2 PZ |
442 | static void rb_augment_path(struct rb_node *node, rb_augment_f func, void *data) |
443 | { | |
444 | struct rb_node *parent; | |
445 | ||
446 | up: | |
447 | func(node, data); | |
448 | parent = rb_parent(node); | |
449 | if (!parent) | |
450 | return; | |
451 | ||
452 | if (node == parent->rb_left && parent->rb_right) | |
453 | func(parent->rb_right, data); | |
454 | else if (parent->rb_left) | |
455 | func(parent->rb_left, data); | |
456 | ||
457 | node = parent; | |
458 | goto up; | |
459 | } | |
460 | ||
461 | /* | |
462 | * after inserting @node into the tree, update the tree to account for | |
463 | * both the new entry and any damage done by rebalance | |
464 | */ | |
465 | void rb_augment_insert(struct rb_node *node, rb_augment_f func, void *data) | |
466 | { | |
467 | if (node->rb_left) | |
468 | node = node->rb_left; | |
469 | else if (node->rb_right) | |
470 | node = node->rb_right; | |
471 | ||
472 | rb_augment_path(node, func, data); | |
473 | } | |
0b6bb66d | 474 | EXPORT_SYMBOL(rb_augment_insert); |
b945d6b2 PZ |
475 | |
476 | /* | |
477 | * before removing the node, find the deepest node on the rebalance path | |
478 | * that will still be there after @node gets removed | |
479 | */ | |
480 | struct rb_node *rb_augment_erase_begin(struct rb_node *node) | |
481 | { | |
482 | struct rb_node *deepest; | |
483 | ||
484 | if (!node->rb_right && !node->rb_left) | |
485 | deepest = rb_parent(node); | |
486 | else if (!node->rb_right) | |
487 | deepest = node->rb_left; | |
488 | else if (!node->rb_left) | |
489 | deepest = node->rb_right; | |
490 | else { | |
491 | deepest = rb_next(node); | |
492 | if (deepest->rb_right) | |
493 | deepest = deepest->rb_right; | |
494 | else if (rb_parent(deepest) != node) | |
495 | deepest = rb_parent(deepest); | |
496 | } | |
497 | ||
498 | return deepest; | |
499 | } | |
0b6bb66d | 500 | EXPORT_SYMBOL(rb_augment_erase_begin); |
b945d6b2 PZ |
501 | |
502 | /* | |
503 | * after removal, update the tree to account for the removed entry | |
504 | * and any rebalance damage. | |
505 | */ | |
506 | void rb_augment_erase_end(struct rb_node *node, rb_augment_f func, void *data) | |
507 | { | |
508 | if (node) | |
509 | rb_augment_path(node, func, data); | |
510 | } | |
0b6bb66d | 511 | EXPORT_SYMBOL(rb_augment_erase_end); |
b945d6b2 | 512 | |
1da177e4 LT |
513 | /* |
514 | * This function returns the first node (in sort order) of the tree. | |
515 | */ | |
f4b477c4 | 516 | struct rb_node *rb_first(const struct rb_root *root) |
1da177e4 LT |
517 | { |
518 | struct rb_node *n; | |
519 | ||
520 | n = root->rb_node; | |
521 | if (!n) | |
522 | return NULL; | |
523 | while (n->rb_left) | |
524 | n = n->rb_left; | |
525 | return n; | |
526 | } | |
527 | EXPORT_SYMBOL(rb_first); | |
528 | ||
f4b477c4 | 529 | struct rb_node *rb_last(const struct rb_root *root) |
1da177e4 LT |
530 | { |
531 | struct rb_node *n; | |
532 | ||
533 | n = root->rb_node; | |
534 | if (!n) | |
535 | return NULL; | |
536 | while (n->rb_right) | |
537 | n = n->rb_right; | |
538 | return n; | |
539 | } | |
540 | EXPORT_SYMBOL(rb_last); | |
541 | ||
f4b477c4 | 542 | struct rb_node *rb_next(const struct rb_node *node) |
1da177e4 | 543 | { |
55a98102 DW |
544 | struct rb_node *parent; |
545 | ||
4c199a93 | 546 | if (RB_EMPTY_NODE(node)) |
10fd48f2 JA |
547 | return NULL; |
548 | ||
7ce6ff9e ML |
549 | /* |
550 | * If we have a right-hand child, go down and then left as far | |
551 | * as we can. | |
552 | */ | |
1da177e4 LT |
553 | if (node->rb_right) { |
554 | node = node->rb_right; | |
555 | while (node->rb_left) | |
556 | node=node->rb_left; | |
f4b477c4 | 557 | return (struct rb_node *)node; |
1da177e4 LT |
558 | } |
559 | ||
7ce6ff9e ML |
560 | /* |
561 | * No right-hand children. Everything down and left is smaller than us, | |
562 | * so any 'next' node must be in the general direction of our parent. | |
563 | * Go up the tree; any time the ancestor is a right-hand child of its | |
564 | * parent, keep going up. First time it's a left-hand child of its | |
565 | * parent, said parent is our 'next' node. | |
566 | */ | |
55a98102 DW |
567 | while ((parent = rb_parent(node)) && node == parent->rb_right) |
568 | node = parent; | |
1da177e4 | 569 | |
55a98102 | 570 | return parent; |
1da177e4 LT |
571 | } |
572 | EXPORT_SYMBOL(rb_next); | |
573 | ||
f4b477c4 | 574 | struct rb_node *rb_prev(const struct rb_node *node) |
1da177e4 | 575 | { |
55a98102 DW |
576 | struct rb_node *parent; |
577 | ||
4c199a93 | 578 | if (RB_EMPTY_NODE(node)) |
10fd48f2 JA |
579 | return NULL; |
580 | ||
7ce6ff9e ML |
581 | /* |
582 | * If we have a left-hand child, go down and then right as far | |
583 | * as we can. | |
584 | */ | |
1da177e4 LT |
585 | if (node->rb_left) { |
586 | node = node->rb_left; | |
587 | while (node->rb_right) | |
588 | node=node->rb_right; | |
f4b477c4 | 589 | return (struct rb_node *)node; |
1da177e4 LT |
590 | } |
591 | ||
7ce6ff9e ML |
592 | /* |
593 | * No left-hand children. Go up till we find an ancestor which | |
594 | * is a right-hand child of its parent. | |
595 | */ | |
55a98102 DW |
596 | while ((parent = rb_parent(node)) && node == parent->rb_left) |
597 | node = parent; | |
1da177e4 | 598 | |
55a98102 | 599 | return parent; |
1da177e4 LT |
600 | } |
601 | EXPORT_SYMBOL(rb_prev); | |
602 | ||
603 | void rb_replace_node(struct rb_node *victim, struct rb_node *new, | |
604 | struct rb_root *root) | |
605 | { | |
55a98102 | 606 | struct rb_node *parent = rb_parent(victim); |
1da177e4 LT |
607 | |
608 | /* Set the surrounding nodes to point to the replacement */ | |
7abc704a | 609 | __rb_change_child(victim, new, parent, root); |
1da177e4 | 610 | if (victim->rb_left) |
55a98102 | 611 | rb_set_parent(victim->rb_left, new); |
1da177e4 | 612 | if (victim->rb_right) |
55a98102 | 613 | rb_set_parent(victim->rb_right, new); |
1da177e4 LT |
614 | |
615 | /* Copy the pointers/colour from the victim to the replacement */ | |
616 | *new = *victim; | |
617 | } | |
618 | EXPORT_SYMBOL(rb_replace_node); |