Commit | Line | Data |
---|---|---|
1da177e4 LT |
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 <linux/rbtree.h> | |
8bc3bcc9 | 24 | #include <linux/export.h> |
1da177e4 | 25 | |
5bc9188a ML |
26 | /* |
27 | * red-black trees properties: http://en.wikipedia.org/wiki/Rbtree | |
28 | * | |
29 | * 1) A node is either red or black | |
30 | * 2) The root is black | |
31 | * 3) All leaves (NULL) are black | |
32 | * 4) Both children of every red node are black | |
33 | * 5) Every simple path from root to leaves contains the same number | |
34 | * of black nodes. | |
35 | * | |
36 | * 4 and 5 give the O(log n) guarantee, since 4 implies you cannot have two | |
37 | * consecutive red nodes in a path and every red node is therefore followed by | |
38 | * a black. So if B is the number of black nodes on every simple path (as per | |
39 | * 5), then the longest possible path due to 4 is 2B. | |
40 | * | |
41 | * We shall indicate color with case, where black nodes are uppercase and red | |
6280d235 ML |
42 | * nodes will be lowercase. Unknown color nodes shall be drawn as red within |
43 | * parentheses and have some accompanying text comment. | |
5bc9188a ML |
44 | */ |
45 | ||
bf7ad8ee ML |
46 | #define RB_RED 0 |
47 | #define RB_BLACK 1 | |
48 | ||
49 | #define rb_color(r) ((r)->__rb_parent_color & 1) | |
50 | #define rb_is_red(r) (!rb_color(r)) | |
51 | #define rb_is_black(r) rb_color(r) | |
bf7ad8ee ML |
52 | |
53 | static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p) | |
54 | { | |
55 | rb->__rb_parent_color = rb_color(rb) | (unsigned long)p; | |
56 | } | |
bf7ad8ee | 57 | |
5bc9188a ML |
58 | static inline void rb_set_parent_color(struct rb_node *rb, |
59 | struct rb_node *p, int color) | |
60 | { | |
61 | rb->__rb_parent_color = (unsigned long)p | color; | |
62 | } | |
63 | ||
64 | static inline struct rb_node *rb_red_parent(struct rb_node *red) | |
65 | { | |
66 | return (struct rb_node *)red->__rb_parent_color; | |
67 | } | |
68 | ||
5bc9188a ML |
69 | /* |
70 | * Helper function for rotations: | |
71 | * - old's parent and color get assigned to new | |
72 | * - old gets assigned new as a parent and 'color' as a color. | |
73 | */ | |
74 | static inline void | |
75 | __rb_rotate_set_parents(struct rb_node *old, struct rb_node *new, | |
76 | struct rb_root *root, int color) | |
77 | { | |
78 | struct rb_node *parent = rb_parent(old); | |
79 | new->__rb_parent_color = old->__rb_parent_color; | |
80 | rb_set_parent_color(old, new, color); | |
81 | if (parent) { | |
82 | if (parent->rb_left == old) | |
83 | parent->rb_left = new; | |
84 | else | |
85 | parent->rb_right = new; | |
86 | } else | |
87 | root->rb_node = new; | |
88 | } | |
89 | ||
1da177e4 LT |
90 | void rb_insert_color(struct rb_node *node, struct rb_root *root) |
91 | { | |
5bc9188a | 92 | struct rb_node *parent = rb_red_parent(node), *gparent, *tmp; |
1da177e4 | 93 | |
6d58452d ML |
94 | while (true) { |
95 | /* | |
96 | * Loop invariant: node is red | |
97 | * | |
98 | * If there is a black parent, we are done. | |
99 | * Otherwise, take some corrective action as we don't | |
100 | * want a red root or two consecutive red nodes. | |
101 | */ | |
6d58452d | 102 | if (!parent) { |
5bc9188a | 103 | rb_set_parent_color(node, NULL, RB_BLACK); |
6d58452d ML |
104 | break; |
105 | } else if (rb_is_black(parent)) | |
106 | break; | |
107 | ||
5bc9188a ML |
108 | gparent = rb_red_parent(parent); |
109 | ||
59633abf ML |
110 | tmp = gparent->rb_right; |
111 | if (parent != tmp) { /* parent == gparent->rb_left */ | |
5bc9188a ML |
112 | if (tmp && rb_is_red(tmp)) { |
113 | /* | |
114 | * Case 1 - color flips | |
115 | * | |
116 | * G g | |
117 | * / \ / \ | |
118 | * p u --> P U | |
119 | * / / | |
120 | * n N | |
121 | * | |
122 | * However, since g's parent might be red, and | |
123 | * 4) does not allow this, we need to recurse | |
124 | * at g. | |
125 | */ | |
126 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
127 | rb_set_parent_color(parent, gparent, RB_BLACK); | |
128 | node = gparent; | |
129 | parent = rb_parent(node); | |
130 | rb_set_parent_color(node, parent, RB_RED); | |
131 | continue; | |
1da177e4 LT |
132 | } |
133 | ||
59633abf ML |
134 | tmp = parent->rb_right; |
135 | if (node == tmp) { | |
5bc9188a ML |
136 | /* |
137 | * Case 2 - left rotate at parent | |
138 | * | |
139 | * G G | |
140 | * / \ / \ | |
141 | * p U --> n U | |
142 | * \ / | |
143 | * n p | |
144 | * | |
145 | * This still leaves us in violation of 4), the | |
146 | * continuation into Case 3 will fix that. | |
147 | */ | |
148 | parent->rb_right = tmp = node->rb_left; | |
149 | node->rb_left = parent; | |
150 | if (tmp) | |
151 | rb_set_parent_color(tmp, parent, | |
152 | RB_BLACK); | |
153 | rb_set_parent_color(parent, node, RB_RED); | |
1da177e4 | 154 | parent = node; |
59633abf | 155 | tmp = node->rb_right; |
1da177e4 LT |
156 | } |
157 | ||
5bc9188a ML |
158 | /* |
159 | * Case 3 - right rotate at gparent | |
160 | * | |
161 | * G P | |
162 | * / \ / \ | |
163 | * p U --> n g | |
164 | * / \ | |
165 | * n U | |
166 | */ | |
59633abf | 167 | gparent->rb_left = tmp; /* == parent->rb_right */ |
5bc9188a ML |
168 | parent->rb_right = gparent; |
169 | if (tmp) | |
170 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
171 | __rb_rotate_set_parents(gparent, parent, root, RB_RED); | |
1f052865 | 172 | break; |
1da177e4 | 173 | } else { |
5bc9188a ML |
174 | tmp = gparent->rb_left; |
175 | if (tmp && rb_is_red(tmp)) { | |
176 | /* Case 1 - color flips */ | |
177 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
178 | rb_set_parent_color(parent, gparent, RB_BLACK); | |
179 | node = gparent; | |
180 | parent = rb_parent(node); | |
181 | rb_set_parent_color(node, parent, RB_RED); | |
182 | continue; | |
1da177e4 LT |
183 | } |
184 | ||
59633abf ML |
185 | tmp = parent->rb_left; |
186 | if (node == tmp) { | |
5bc9188a ML |
187 | /* Case 2 - right rotate at parent */ |
188 | parent->rb_left = tmp = node->rb_right; | |
189 | node->rb_right = parent; | |
190 | if (tmp) | |
191 | rb_set_parent_color(tmp, parent, | |
192 | RB_BLACK); | |
193 | rb_set_parent_color(parent, node, RB_RED); | |
1da177e4 | 194 | parent = node; |
59633abf | 195 | tmp = node->rb_left; |
1da177e4 LT |
196 | } |
197 | ||
5bc9188a | 198 | /* Case 3 - left rotate at gparent */ |
59633abf | 199 | gparent->rb_right = tmp; /* == parent->rb_left */ |
5bc9188a ML |
200 | parent->rb_left = gparent; |
201 | if (tmp) | |
202 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
203 | __rb_rotate_set_parents(gparent, parent, root, RB_RED); | |
1f052865 | 204 | break; |
1da177e4 LT |
205 | } |
206 | } | |
1da177e4 LT |
207 | } |
208 | EXPORT_SYMBOL(rb_insert_color); | |
209 | ||
210 | static void __rb_erase_color(struct rb_node *node, struct rb_node *parent, | |
211 | struct rb_root *root) | |
212 | { | |
6280d235 | 213 | struct rb_node *sibling, *tmp1, *tmp2; |
1da177e4 | 214 | |
d6ff1273 ML |
215 | while (true) { |
216 | /* | |
217 | * Loop invariant: all leaf paths going through node have a | |
218 | * black node count that is 1 lower than other leaf paths. | |
219 | * | |
220 | * If node is red, we can flip it to black to adjust. | |
221 | * If node is the root, all leaf paths go through it. | |
222 | * Otherwise, we need to adjust the tree through color flips | |
223 | * and tree rotations as per one of the 4 cases below. | |
224 | */ | |
225 | if (node && rb_is_red(node)) { | |
6280d235 | 226 | rb_set_parent_color(node, parent, RB_BLACK); |
d6ff1273 ML |
227 | break; |
228 | } else if (!parent) { | |
229 | break; | |
59633abf ML |
230 | } |
231 | sibling = parent->rb_right; | |
232 | if (node != sibling) { /* node == parent->rb_left */ | |
6280d235 ML |
233 | if (rb_is_red(sibling)) { |
234 | /* | |
235 | * Case 1 - left rotate at parent | |
236 | * | |
237 | * P S | |
238 | * / \ / \ | |
239 | * N s --> p Sr | |
240 | * / \ / \ | |
241 | * Sl Sr N Sl | |
242 | */ | |
243 | parent->rb_right = tmp1 = sibling->rb_left; | |
244 | sibling->rb_left = parent; | |
245 | rb_set_parent_color(tmp1, parent, RB_BLACK); | |
246 | __rb_rotate_set_parents(parent, sibling, root, | |
247 | RB_RED); | |
248 | sibling = tmp1; | |
1da177e4 | 249 | } |
6280d235 ML |
250 | tmp1 = sibling->rb_right; |
251 | if (!tmp1 || rb_is_black(tmp1)) { | |
252 | tmp2 = sibling->rb_left; | |
253 | if (!tmp2 || rb_is_black(tmp2)) { | |
254 | /* | |
255 | * Case 2 - sibling color flip | |
256 | * (p could be either color here) | |
257 | * | |
258 | * (p) (p) | |
259 | * / \ / \ | |
260 | * N S --> N s | |
261 | * / \ / \ | |
262 | * Sl Sr Sl Sr | |
263 | * | |
264 | * This leaves us violating 5), so | |
265 | * recurse at p. If p is red, the | |
266 | * recursion will just flip it to black | |
267 | * and exit. If coming from Case 1, | |
268 | * p is known to be red. | |
269 | */ | |
270 | rb_set_parent_color(sibling, parent, | |
271 | RB_RED); | |
e125d147 ML |
272 | node = parent; |
273 | parent = rb_parent(node); | |
274 | continue; | |
1da177e4 | 275 | } |
6280d235 ML |
276 | /* |
277 | * Case 3 - right rotate at sibling | |
278 | * (p could be either color here) | |
279 | * | |
280 | * (p) (p) | |
281 | * / \ / \ | |
282 | * N S --> N Sl | |
283 | * / \ \ | |
284 | * sl Sr s | |
285 | * \ | |
286 | * Sr | |
287 | */ | |
288 | sibling->rb_left = tmp1 = tmp2->rb_right; | |
289 | tmp2->rb_right = sibling; | |
290 | parent->rb_right = tmp2; | |
291 | if (tmp1) | |
292 | rb_set_parent_color(tmp1, sibling, | |
293 | RB_BLACK); | |
294 | tmp1 = sibling; | |
295 | sibling = tmp2; | |
1da177e4 | 296 | } |
6280d235 ML |
297 | /* |
298 | * Case 4 - left rotate at parent + color flips | |
299 | * (p and sl could be either color here. | |
300 | * After rotation, p becomes black, s acquires | |
301 | * p's color, and sl keeps its color) | |
302 | * | |
303 | * (p) (s) | |
304 | * / \ / \ | |
305 | * N S --> P Sr | |
306 | * / \ / \ | |
307 | * (sl) sr N (sl) | |
308 | */ | |
309 | parent->rb_right = tmp2 = sibling->rb_left; | |
310 | sibling->rb_left = parent; | |
311 | rb_set_parent_color(tmp1, sibling, RB_BLACK); | |
312 | if (tmp2) | |
313 | rb_set_parent(tmp2, parent); | |
314 | __rb_rotate_set_parents(parent, sibling, root, | |
315 | RB_BLACK); | |
e125d147 | 316 | break; |
d6ff1273 | 317 | } else { |
6280d235 ML |
318 | sibling = parent->rb_left; |
319 | if (rb_is_red(sibling)) { | |
320 | /* Case 1 - right rotate at parent */ | |
321 | parent->rb_left = tmp1 = sibling->rb_right; | |
322 | sibling->rb_right = parent; | |
323 | rb_set_parent_color(tmp1, parent, RB_BLACK); | |
324 | __rb_rotate_set_parents(parent, sibling, root, | |
325 | RB_RED); | |
326 | sibling = tmp1; | |
1da177e4 | 327 | } |
6280d235 ML |
328 | tmp1 = sibling->rb_left; |
329 | if (!tmp1 || rb_is_black(tmp1)) { | |
330 | tmp2 = sibling->rb_right; | |
331 | if (!tmp2 || rb_is_black(tmp2)) { | |
332 | /* Case 2 - sibling color flip */ | |
333 | rb_set_parent_color(sibling, parent, | |
334 | RB_RED); | |
e125d147 ML |
335 | node = parent; |
336 | parent = rb_parent(node); | |
337 | continue; | |
1da177e4 | 338 | } |
6280d235 ML |
339 | /* Case 3 - right rotate at sibling */ |
340 | sibling->rb_right = tmp1 = tmp2->rb_left; | |
341 | tmp2->rb_left = sibling; | |
342 | parent->rb_left = tmp2; | |
343 | if (tmp1) | |
344 | rb_set_parent_color(tmp1, sibling, | |
345 | RB_BLACK); | |
346 | tmp1 = sibling; | |
347 | sibling = tmp2; | |
1da177e4 | 348 | } |
6280d235 ML |
349 | /* Case 4 - left rotate at parent + color flips */ |
350 | parent->rb_left = tmp2 = sibling->rb_right; | |
351 | sibling->rb_right = parent; | |
352 | rb_set_parent_color(tmp1, sibling, RB_BLACK); | |
353 | if (tmp2) | |
354 | rb_set_parent(tmp2, parent); | |
355 | __rb_rotate_set_parents(parent, sibling, root, | |
356 | RB_BLACK); | |
e125d147 | 357 | break; |
1da177e4 LT |
358 | } |
359 | } | |
1da177e4 LT |
360 | } |
361 | ||
362 | void rb_erase(struct rb_node *node, struct rb_root *root) | |
363 | { | |
364 | struct rb_node *child, *parent; | |
365 | int color; | |
366 | ||
367 | if (!node->rb_left) | |
368 | child = node->rb_right; | |
369 | else if (!node->rb_right) | |
370 | child = node->rb_left; | |
7ce6ff9e | 371 | else { |
1da177e4 LT |
372 | struct rb_node *old = node, *left; |
373 | ||
374 | node = node->rb_right; | |
375 | while ((left = node->rb_left) != NULL) | |
376 | node = left; | |
16c047ad WS |
377 | |
378 | if (rb_parent(old)) { | |
379 | if (rb_parent(old)->rb_left == old) | |
380 | rb_parent(old)->rb_left = node; | |
381 | else | |
382 | rb_parent(old)->rb_right = node; | |
383 | } else | |
384 | root->rb_node = node; | |
385 | ||
1da177e4 | 386 | child = node->rb_right; |
55a98102 | 387 | parent = rb_parent(node); |
2f3243ae | 388 | color = rb_color(node); |
1da177e4 | 389 | |
55a98102 | 390 | if (parent == old) { |
1da177e4 | 391 | parent = node; |
4c601178 WS |
392 | } else { |
393 | if (child) | |
394 | rb_set_parent(child, parent); | |
1975e593 | 395 | parent->rb_left = child; |
4b324126 WS |
396 | |
397 | node->rb_right = old->rb_right; | |
398 | rb_set_parent(old->rb_right, node); | |
4c601178 | 399 | } |
1975e593 | 400 | |
bf7ad8ee | 401 | node->__rb_parent_color = old->__rb_parent_color; |
1da177e4 | 402 | node->rb_left = old->rb_left; |
55a98102 | 403 | rb_set_parent(old->rb_left, node); |
4b324126 | 404 | |
1da177e4 LT |
405 | goto color; |
406 | } | |
407 | ||
55a98102 | 408 | parent = rb_parent(node); |
2f3243ae | 409 | color = rb_color(node); |
1da177e4 LT |
410 | |
411 | if (child) | |
55a98102 | 412 | rb_set_parent(child, parent); |
7ce6ff9e | 413 | if (parent) { |
1da177e4 LT |
414 | if (parent->rb_left == node) |
415 | parent->rb_left = child; | |
416 | else | |
417 | parent->rb_right = child; | |
7ce6ff9e | 418 | } else |
b945d6b2 | 419 | root->rb_node = child; |
1da177e4 | 420 | |
7ce6ff9e | 421 | color: |
1da177e4 LT |
422 | if (color == RB_BLACK) |
423 | __rb_erase_color(child, parent, root); | |
424 | } | |
425 | EXPORT_SYMBOL(rb_erase); | |
426 | ||
b945d6b2 PZ |
427 | static void rb_augment_path(struct rb_node *node, rb_augment_f func, void *data) |
428 | { | |
429 | struct rb_node *parent; | |
430 | ||
431 | up: | |
432 | func(node, data); | |
433 | parent = rb_parent(node); | |
434 | if (!parent) | |
435 | return; | |
436 | ||
437 | if (node == parent->rb_left && parent->rb_right) | |
438 | func(parent->rb_right, data); | |
439 | else if (parent->rb_left) | |
440 | func(parent->rb_left, data); | |
441 | ||
442 | node = parent; | |
443 | goto up; | |
444 | } | |
445 | ||
446 | /* | |
447 | * after inserting @node into the tree, update the tree to account for | |
448 | * both the new entry and any damage done by rebalance | |
449 | */ | |
450 | void rb_augment_insert(struct rb_node *node, rb_augment_f func, void *data) | |
451 | { | |
452 | if (node->rb_left) | |
453 | node = node->rb_left; | |
454 | else if (node->rb_right) | |
455 | node = node->rb_right; | |
456 | ||
457 | rb_augment_path(node, func, data); | |
458 | } | |
0b6bb66d | 459 | EXPORT_SYMBOL(rb_augment_insert); |
b945d6b2 PZ |
460 | |
461 | /* | |
462 | * before removing the node, find the deepest node on the rebalance path | |
463 | * that will still be there after @node gets removed | |
464 | */ | |
465 | struct rb_node *rb_augment_erase_begin(struct rb_node *node) | |
466 | { | |
467 | struct rb_node *deepest; | |
468 | ||
469 | if (!node->rb_right && !node->rb_left) | |
470 | deepest = rb_parent(node); | |
471 | else if (!node->rb_right) | |
472 | deepest = node->rb_left; | |
473 | else if (!node->rb_left) | |
474 | deepest = node->rb_right; | |
475 | else { | |
476 | deepest = rb_next(node); | |
477 | if (deepest->rb_right) | |
478 | deepest = deepest->rb_right; | |
479 | else if (rb_parent(deepest) != node) | |
480 | deepest = rb_parent(deepest); | |
481 | } | |
482 | ||
483 | return deepest; | |
484 | } | |
0b6bb66d | 485 | EXPORT_SYMBOL(rb_augment_erase_begin); |
b945d6b2 PZ |
486 | |
487 | /* | |
488 | * after removal, update the tree to account for the removed entry | |
489 | * and any rebalance damage. | |
490 | */ | |
491 | void rb_augment_erase_end(struct rb_node *node, rb_augment_f func, void *data) | |
492 | { | |
493 | if (node) | |
494 | rb_augment_path(node, func, data); | |
495 | } | |
0b6bb66d | 496 | EXPORT_SYMBOL(rb_augment_erase_end); |
b945d6b2 | 497 | |
1da177e4 LT |
498 | /* |
499 | * This function returns the first node (in sort order) of the tree. | |
500 | */ | |
f4b477c4 | 501 | struct rb_node *rb_first(const struct rb_root *root) |
1da177e4 LT |
502 | { |
503 | struct rb_node *n; | |
504 | ||
505 | n = root->rb_node; | |
506 | if (!n) | |
507 | return NULL; | |
508 | while (n->rb_left) | |
509 | n = n->rb_left; | |
510 | return n; | |
511 | } | |
512 | EXPORT_SYMBOL(rb_first); | |
513 | ||
f4b477c4 | 514 | struct rb_node *rb_last(const struct rb_root *root) |
1da177e4 LT |
515 | { |
516 | struct rb_node *n; | |
517 | ||
518 | n = root->rb_node; | |
519 | if (!n) | |
520 | return NULL; | |
521 | while (n->rb_right) | |
522 | n = n->rb_right; | |
523 | return n; | |
524 | } | |
525 | EXPORT_SYMBOL(rb_last); | |
526 | ||
f4b477c4 | 527 | struct rb_node *rb_next(const struct rb_node *node) |
1da177e4 | 528 | { |
55a98102 DW |
529 | struct rb_node *parent; |
530 | ||
4c199a93 | 531 | if (RB_EMPTY_NODE(node)) |
10fd48f2 JA |
532 | return NULL; |
533 | ||
7ce6ff9e ML |
534 | /* |
535 | * If we have a right-hand child, go down and then left as far | |
536 | * as we can. | |
537 | */ | |
1da177e4 LT |
538 | if (node->rb_right) { |
539 | node = node->rb_right; | |
540 | while (node->rb_left) | |
541 | node=node->rb_left; | |
f4b477c4 | 542 | return (struct rb_node *)node; |
1da177e4 LT |
543 | } |
544 | ||
7ce6ff9e ML |
545 | /* |
546 | * No right-hand children. Everything down and left is smaller than us, | |
547 | * so any 'next' node must be in the general direction of our parent. | |
548 | * Go up the tree; any time the ancestor is a right-hand child of its | |
549 | * parent, keep going up. First time it's a left-hand child of its | |
550 | * parent, said parent is our 'next' node. | |
551 | */ | |
55a98102 DW |
552 | while ((parent = rb_parent(node)) && node == parent->rb_right) |
553 | node = parent; | |
1da177e4 | 554 | |
55a98102 | 555 | return parent; |
1da177e4 LT |
556 | } |
557 | EXPORT_SYMBOL(rb_next); | |
558 | ||
f4b477c4 | 559 | struct rb_node *rb_prev(const struct rb_node *node) |
1da177e4 | 560 | { |
55a98102 DW |
561 | struct rb_node *parent; |
562 | ||
4c199a93 | 563 | if (RB_EMPTY_NODE(node)) |
10fd48f2 JA |
564 | return NULL; |
565 | ||
7ce6ff9e ML |
566 | /* |
567 | * If we have a left-hand child, go down and then right as far | |
568 | * as we can. | |
569 | */ | |
1da177e4 LT |
570 | if (node->rb_left) { |
571 | node = node->rb_left; | |
572 | while (node->rb_right) | |
573 | node=node->rb_right; | |
f4b477c4 | 574 | return (struct rb_node *)node; |
1da177e4 LT |
575 | } |
576 | ||
7ce6ff9e ML |
577 | /* |
578 | * No left-hand children. Go up till we find an ancestor which | |
579 | * is a right-hand child of its parent. | |
580 | */ | |
55a98102 DW |
581 | while ((parent = rb_parent(node)) && node == parent->rb_left) |
582 | node = parent; | |
1da177e4 | 583 | |
55a98102 | 584 | return parent; |
1da177e4 LT |
585 | } |
586 | EXPORT_SYMBOL(rb_prev); | |
587 | ||
588 | void rb_replace_node(struct rb_node *victim, struct rb_node *new, | |
589 | struct rb_root *root) | |
590 | { | |
55a98102 | 591 | struct rb_node *parent = rb_parent(victim); |
1da177e4 LT |
592 | |
593 | /* Set the surrounding nodes to point to the replacement */ | |
594 | if (parent) { | |
595 | if (victim == parent->rb_left) | |
596 | parent->rb_left = new; | |
597 | else | |
598 | parent->rb_right = new; | |
599 | } else { | |
600 | root->rb_node = new; | |
601 | } | |
602 | if (victim->rb_left) | |
55a98102 | 603 | rb_set_parent(victim->rb_left, new); |
1da177e4 | 604 | if (victim->rb_right) |
55a98102 | 605 | rb_set_parent(victim->rb_right, new); |
1da177e4 LT |
606 | |
607 | /* Copy the pointers/colour from the victim to the replacement */ | |
608 | *new = *victim; | |
609 | } | |
610 | EXPORT_SYMBOL(rb_replace_node); |