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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> | |
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 | ||
14b94af0 ML |
108 | static __always_inline void |
109 | __rb_insert(struct rb_node *node, struct rb_root *root, | |
110 | void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) | |
1da177e4 | 111 | { |
5bc9188a | 112 | struct rb_node *parent = rb_red_parent(node), *gparent, *tmp; |
1da177e4 | 113 | |
6d58452d ML |
114 | while (true) { |
115 | /* | |
116 | * Loop invariant: node is red | |
117 | * | |
118 | * If there is a black parent, we are done. | |
119 | * Otherwise, take some corrective action as we don't | |
120 | * want a red root or two consecutive red nodes. | |
121 | */ | |
6d58452d | 122 | if (!parent) { |
5bc9188a | 123 | rb_set_parent_color(node, NULL, RB_BLACK); |
6d58452d ML |
124 | break; |
125 | } else if (rb_is_black(parent)) | |
126 | break; | |
127 | ||
5bc9188a ML |
128 | gparent = rb_red_parent(parent); |
129 | ||
59633abf ML |
130 | tmp = gparent->rb_right; |
131 | if (parent != tmp) { /* parent == gparent->rb_left */ | |
5bc9188a ML |
132 | if (tmp && rb_is_red(tmp)) { |
133 | /* | |
134 | * Case 1 - color flips | |
135 | * | |
136 | * G g | |
137 | * / \ / \ | |
138 | * p u --> P U | |
139 | * / / | |
140 | * n N | |
141 | * | |
142 | * However, since g's parent might be red, and | |
143 | * 4) does not allow this, we need to recurse | |
144 | * at g. | |
145 | */ | |
146 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
147 | rb_set_parent_color(parent, gparent, RB_BLACK); | |
148 | node = gparent; | |
149 | parent = rb_parent(node); | |
150 | rb_set_parent_color(node, parent, RB_RED); | |
151 | continue; | |
1da177e4 LT |
152 | } |
153 | ||
59633abf ML |
154 | tmp = parent->rb_right; |
155 | if (node == tmp) { | |
5bc9188a ML |
156 | /* |
157 | * Case 2 - left rotate at parent | |
158 | * | |
159 | * G G | |
160 | * / \ / \ | |
161 | * p U --> n U | |
162 | * \ / | |
163 | * n p | |
164 | * | |
165 | * This still leaves us in violation of 4), the | |
166 | * continuation into Case 3 will fix that. | |
167 | */ | |
168 | parent->rb_right = tmp = node->rb_left; | |
169 | node->rb_left = parent; | |
170 | if (tmp) | |
171 | rb_set_parent_color(tmp, parent, | |
172 | RB_BLACK); | |
173 | rb_set_parent_color(parent, node, RB_RED); | |
14b94af0 | 174 | augment_rotate(parent, node); |
1da177e4 | 175 | parent = node; |
59633abf | 176 | tmp = node->rb_right; |
1da177e4 LT |
177 | } |
178 | ||
5bc9188a ML |
179 | /* |
180 | * Case 3 - right rotate at gparent | |
181 | * | |
182 | * G P | |
183 | * / \ / \ | |
184 | * p U --> n g | |
185 | * / \ | |
186 | * n U | |
187 | */ | |
59633abf | 188 | gparent->rb_left = tmp; /* == parent->rb_right */ |
5bc9188a ML |
189 | parent->rb_right = gparent; |
190 | if (tmp) | |
191 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
192 | __rb_rotate_set_parents(gparent, parent, root, RB_RED); | |
14b94af0 | 193 | augment_rotate(gparent, parent); |
1f052865 | 194 | break; |
1da177e4 | 195 | } else { |
5bc9188a ML |
196 | tmp = gparent->rb_left; |
197 | if (tmp && rb_is_red(tmp)) { | |
198 | /* Case 1 - color flips */ | |
199 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
200 | rb_set_parent_color(parent, gparent, RB_BLACK); | |
201 | node = gparent; | |
202 | parent = rb_parent(node); | |
203 | rb_set_parent_color(node, parent, RB_RED); | |
204 | continue; | |
1da177e4 LT |
205 | } |
206 | ||
59633abf ML |
207 | tmp = parent->rb_left; |
208 | if (node == tmp) { | |
5bc9188a ML |
209 | /* Case 2 - right rotate at parent */ |
210 | parent->rb_left = tmp = node->rb_right; | |
211 | node->rb_right = parent; | |
212 | if (tmp) | |
213 | rb_set_parent_color(tmp, parent, | |
214 | RB_BLACK); | |
215 | rb_set_parent_color(parent, node, RB_RED); | |
14b94af0 | 216 | augment_rotate(parent, node); |
1da177e4 | 217 | parent = node; |
59633abf | 218 | tmp = node->rb_left; |
1da177e4 LT |
219 | } |
220 | ||
5bc9188a | 221 | /* Case 3 - left rotate at gparent */ |
59633abf | 222 | gparent->rb_right = tmp; /* == parent->rb_left */ |
5bc9188a ML |
223 | parent->rb_left = gparent; |
224 | if (tmp) | |
225 | rb_set_parent_color(tmp, gparent, RB_BLACK); | |
226 | __rb_rotate_set_parents(gparent, parent, root, RB_RED); | |
14b94af0 | 227 | augment_rotate(gparent, parent); |
1f052865 | 228 | break; |
1da177e4 LT |
229 | } |
230 | } | |
1da177e4 | 231 | } |
1da177e4 | 232 | |
14b94af0 ML |
233 | static __always_inline void |
234 | __rb_erase_color(struct rb_node *parent, struct rb_root *root, | |
235 | const struct rb_augment_callbacks *augment) | |
1da177e4 | 236 | { |
46b6135a | 237 | struct rb_node *node = NULL, *sibling, *tmp1, *tmp2; |
1da177e4 | 238 | |
d6ff1273 ML |
239 | while (true) { |
240 | /* | |
46b6135a ML |
241 | * Loop invariants: |
242 | * - node is black (or NULL on first iteration) | |
243 | * - node is not the root (parent is not NULL) | |
244 | * - All leaf paths going through parent and node have a | |
245 | * black node count that is 1 lower than other leaf paths. | |
d6ff1273 | 246 | */ |
59633abf ML |
247 | sibling = parent->rb_right; |
248 | if (node != sibling) { /* node == parent->rb_left */ | |
6280d235 ML |
249 | if (rb_is_red(sibling)) { |
250 | /* | |
251 | * Case 1 - left rotate at parent | |
252 | * | |
253 | * P S | |
254 | * / \ / \ | |
255 | * N s --> p Sr | |
256 | * / \ / \ | |
257 | * Sl Sr N Sl | |
258 | */ | |
259 | parent->rb_right = tmp1 = sibling->rb_left; | |
260 | sibling->rb_left = parent; | |
261 | rb_set_parent_color(tmp1, parent, RB_BLACK); | |
262 | __rb_rotate_set_parents(parent, sibling, root, | |
263 | RB_RED); | |
14b94af0 | 264 | augment->rotate(parent, sibling); |
6280d235 | 265 | sibling = tmp1; |
1da177e4 | 266 | } |
6280d235 ML |
267 | tmp1 = sibling->rb_right; |
268 | if (!tmp1 || rb_is_black(tmp1)) { | |
269 | tmp2 = sibling->rb_left; | |
270 | if (!tmp2 || rb_is_black(tmp2)) { | |
271 | /* | |
272 | * Case 2 - sibling color flip | |
273 | * (p could be either color here) | |
274 | * | |
275 | * (p) (p) | |
276 | * / \ / \ | |
277 | * N S --> N s | |
278 | * / \ / \ | |
279 | * Sl Sr Sl Sr | |
280 | * | |
46b6135a ML |
281 | * This leaves us violating 5) which |
282 | * can be fixed by flipping p to black | |
283 | * if it was red, or by recursing at p. | |
284 | * p is red when coming from Case 1. | |
6280d235 ML |
285 | */ |
286 | rb_set_parent_color(sibling, parent, | |
287 | RB_RED); | |
46b6135a ML |
288 | if (rb_is_red(parent)) |
289 | rb_set_black(parent); | |
290 | else { | |
291 | node = parent; | |
292 | parent = rb_parent(node); | |
293 | if (parent) | |
294 | continue; | |
295 | } | |
296 | break; | |
1da177e4 | 297 | } |
6280d235 ML |
298 | /* |
299 | * Case 3 - right rotate at sibling | |
300 | * (p could be either color here) | |
301 | * | |
302 | * (p) (p) | |
303 | * / \ / \ | |
304 | * N S --> N Sl | |
305 | * / \ \ | |
306 | * sl Sr s | |
307 | * \ | |
308 | * Sr | |
309 | */ | |
310 | sibling->rb_left = tmp1 = tmp2->rb_right; | |
311 | tmp2->rb_right = sibling; | |
312 | parent->rb_right = tmp2; | |
313 | if (tmp1) | |
314 | rb_set_parent_color(tmp1, sibling, | |
315 | RB_BLACK); | |
14b94af0 | 316 | augment->rotate(sibling, tmp2); |
6280d235 ML |
317 | tmp1 = sibling; |
318 | sibling = tmp2; | |
1da177e4 | 319 | } |
6280d235 ML |
320 | /* |
321 | * Case 4 - left rotate at parent + color flips | |
322 | * (p and sl could be either color here. | |
323 | * After rotation, p becomes black, s acquires | |
324 | * p's color, and sl keeps its color) | |
325 | * | |
326 | * (p) (s) | |
327 | * / \ / \ | |
328 | * N S --> P Sr | |
329 | * / \ / \ | |
330 | * (sl) sr N (sl) | |
331 | */ | |
332 | parent->rb_right = tmp2 = sibling->rb_left; | |
333 | sibling->rb_left = parent; | |
334 | rb_set_parent_color(tmp1, sibling, RB_BLACK); | |
335 | if (tmp2) | |
336 | rb_set_parent(tmp2, parent); | |
337 | __rb_rotate_set_parents(parent, sibling, root, | |
338 | RB_BLACK); | |
14b94af0 | 339 | augment->rotate(parent, sibling); |
e125d147 | 340 | break; |
d6ff1273 | 341 | } else { |
6280d235 ML |
342 | sibling = parent->rb_left; |
343 | if (rb_is_red(sibling)) { | |
344 | /* Case 1 - right rotate at parent */ | |
345 | parent->rb_left = tmp1 = sibling->rb_right; | |
346 | sibling->rb_right = parent; | |
347 | rb_set_parent_color(tmp1, parent, RB_BLACK); | |
348 | __rb_rotate_set_parents(parent, sibling, root, | |
349 | RB_RED); | |
14b94af0 | 350 | augment->rotate(parent, sibling); |
6280d235 | 351 | sibling = tmp1; |
1da177e4 | 352 | } |
6280d235 ML |
353 | tmp1 = sibling->rb_left; |
354 | if (!tmp1 || rb_is_black(tmp1)) { | |
355 | tmp2 = sibling->rb_right; | |
356 | if (!tmp2 || rb_is_black(tmp2)) { | |
357 | /* Case 2 - sibling color flip */ | |
358 | rb_set_parent_color(sibling, parent, | |
359 | RB_RED); | |
46b6135a ML |
360 | if (rb_is_red(parent)) |
361 | rb_set_black(parent); | |
362 | else { | |
363 | node = parent; | |
364 | parent = rb_parent(node); | |
365 | if (parent) | |
366 | continue; | |
367 | } | |
368 | break; | |
1da177e4 | 369 | } |
6280d235 ML |
370 | /* Case 3 - right rotate at sibling */ |
371 | sibling->rb_right = tmp1 = tmp2->rb_left; | |
372 | tmp2->rb_left = sibling; | |
373 | parent->rb_left = tmp2; | |
374 | if (tmp1) | |
375 | rb_set_parent_color(tmp1, sibling, | |
376 | RB_BLACK); | |
14b94af0 | 377 | augment->rotate(sibling, tmp2); |
6280d235 ML |
378 | tmp1 = sibling; |
379 | sibling = tmp2; | |
1da177e4 | 380 | } |
6280d235 ML |
381 | /* Case 4 - left rotate at parent + color flips */ |
382 | parent->rb_left = tmp2 = sibling->rb_right; | |
383 | sibling->rb_right = parent; | |
384 | rb_set_parent_color(tmp1, sibling, RB_BLACK); | |
385 | if (tmp2) | |
386 | rb_set_parent(tmp2, parent); | |
387 | __rb_rotate_set_parents(parent, sibling, root, | |
388 | RB_BLACK); | |
14b94af0 | 389 | augment->rotate(parent, sibling); |
e125d147 | 390 | break; |
1da177e4 LT |
391 | } |
392 | } | |
1da177e4 LT |
393 | } |
394 | ||
14b94af0 ML |
395 | static __always_inline void |
396 | __rb_erase(struct rb_node *node, struct rb_root *root, | |
397 | const struct rb_augment_callbacks *augment) | |
1da177e4 | 398 | { |
60670b80 | 399 | struct rb_node *child = node->rb_right, *tmp = node->rb_left; |
46b6135a | 400 | struct rb_node *parent, *rebalance; |
4f035ad6 | 401 | unsigned long pc; |
1da177e4 | 402 | |
60670b80 | 403 | if (!tmp) { |
46b6135a ML |
404 | /* |
405 | * Case 1: node to erase has no more than 1 child (easy!) | |
406 | * | |
407 | * Note that if there is one child it must be red due to 5) | |
408 | * and node must be black due to 4). We adjust colors locally | |
409 | * so as to bypass __rb_erase_color() later on. | |
410 | */ | |
4f035ad6 ML |
411 | pc = node->__rb_parent_color; |
412 | parent = __rb_parent(pc); | |
60670b80 | 413 | __rb_change_child(node, child, parent, root); |
46b6135a | 414 | if (child) { |
4f035ad6 | 415 | child->__rb_parent_color = pc; |
46b6135a | 416 | rebalance = NULL; |
4f035ad6 ML |
417 | } else |
418 | rebalance = __rb_is_black(pc) ? parent : NULL; | |
14b94af0 | 419 | tmp = parent; |
60670b80 ML |
420 | } else if (!child) { |
421 | /* Still case 1, but this time the child is node->rb_left */ | |
4f035ad6 ML |
422 | tmp->__rb_parent_color = pc = node->__rb_parent_color; |
423 | parent = __rb_parent(pc); | |
46b6135a | 424 | __rb_change_child(node, tmp, parent, root); |
46b6135a | 425 | rebalance = NULL; |
14b94af0 | 426 | tmp = parent; |
60670b80 | 427 | } else { |
4f035ad6 ML |
428 | struct rb_node *successor = child, *child2; |
429 | tmp = child->rb_left; | |
430 | if (!tmp) { | |
431 | /* | |
432 | * Case 2: node's successor is its right child | |
433 | * | |
434 | * (n) (s) | |
435 | * / \ / \ | |
436 | * (x) (s) -> (x) (c) | |
437 | * \ | |
438 | * (c) | |
439 | */ | |
14b94af0 ML |
440 | parent = successor; |
441 | child2 = successor->rb_right; | |
442 | augment->copy(node, successor); | |
4c601178 | 443 | } else { |
4f035ad6 ML |
444 | /* |
445 | * Case 3: node's successor is leftmost under | |
446 | * node's right child subtree | |
447 | * | |
448 | * (n) (s) | |
449 | * / \ / \ | |
450 | * (x) (y) -> (x) (y) | |
451 | * / / | |
452 | * (p) (p) | |
453 | * / / | |
454 | * (s) (c) | |
455 | * \ | |
456 | * (c) | |
457 | */ | |
458 | do { | |
459 | parent = successor; | |
460 | successor = tmp; | |
461 | tmp = tmp->rb_left; | |
462 | } while (tmp); | |
463 | parent->rb_left = child2 = successor->rb_right; | |
464 | successor->rb_right = child; | |
465 | rb_set_parent(child, successor); | |
14b94af0 ML |
466 | augment->copy(node, successor); |
467 | augment->propagate(parent, successor); | |
4c601178 | 468 | } |
1975e593 | 469 | |
4f035ad6 ML |
470 | successor->rb_left = tmp = node->rb_left; |
471 | rb_set_parent(tmp, successor); | |
472 | ||
473 | pc = node->__rb_parent_color; | |
474 | tmp = __rb_parent(pc); | |
475 | __rb_change_child(node, successor, tmp, root); | |
476 | if (child2) { | |
477 | successor->__rb_parent_color = pc; | |
478 | rb_set_parent_color(child2, parent, RB_BLACK); | |
46b6135a ML |
479 | rebalance = NULL; |
480 | } else { | |
4f035ad6 ML |
481 | unsigned long pc2 = successor->__rb_parent_color; |
482 | successor->__rb_parent_color = pc; | |
483 | rebalance = __rb_is_black(pc2) ? parent : NULL; | |
46b6135a | 484 | } |
14b94af0 | 485 | tmp = successor; |
1da177e4 LT |
486 | } |
487 | ||
14b94af0 | 488 | augment->propagate(tmp, NULL); |
46b6135a | 489 | if (rebalance) |
14b94af0 ML |
490 | __rb_erase_color(rebalance, root, augment); |
491 | } | |
492 | ||
493 | /* | |
494 | * Non-augmented rbtree manipulation functions. | |
495 | * | |
496 | * We use dummy augmented callbacks here, and have the compiler optimize them | |
497 | * out of the rb_insert_color() and rb_erase() function definitions. | |
498 | */ | |
499 | ||
500 | static inline void dummy_propagate(struct rb_node *node, struct rb_node *stop) {} | |
501 | static inline void dummy_copy(struct rb_node *old, struct rb_node *new) {} | |
502 | static inline void dummy_rotate(struct rb_node *old, struct rb_node *new) {} | |
503 | ||
504 | static const struct rb_augment_callbacks dummy_callbacks = { | |
505 | dummy_propagate, dummy_copy, dummy_rotate | |
506 | }; | |
507 | ||
508 | void rb_insert_color(struct rb_node *node, struct rb_root *root) | |
509 | { | |
510 | __rb_insert(node, root, dummy_rotate); | |
511 | } | |
512 | EXPORT_SYMBOL(rb_insert_color); | |
513 | ||
514 | void rb_erase(struct rb_node *node, struct rb_root *root) | |
515 | { | |
516 | __rb_erase(node, root, &dummy_callbacks); | |
1da177e4 LT |
517 | } |
518 | EXPORT_SYMBOL(rb_erase); | |
519 | ||
14b94af0 ML |
520 | /* |
521 | * Augmented rbtree manipulation functions. | |
522 | * | |
523 | * This instantiates the same __always_inline functions as in the non-augmented | |
524 | * case, but this time with user-defined callbacks. | |
525 | */ | |
526 | ||
527 | void __rb_insert_augmented(struct rb_node *node, struct rb_root *root, | |
528 | void (*augment_rotate)(struct rb_node *old, struct rb_node *new)) | |
529 | { | |
530 | __rb_insert(node, root, augment_rotate); | |
531 | } | |
532 | EXPORT_SYMBOL(__rb_insert_augmented); | |
533 | ||
534 | void rb_erase_augmented(struct rb_node *node, struct rb_root *root, | |
535 | const struct rb_augment_callbacks *augment) | |
536 | { | |
537 | __rb_erase(node, root, augment); | |
538 | } | |
539 | EXPORT_SYMBOL(rb_erase_augmented); | |
540 | ||
1da177e4 LT |
541 | /* |
542 | * This function returns the first node (in sort order) of the tree. | |
543 | */ | |
f4b477c4 | 544 | struct rb_node *rb_first(const struct rb_root *root) |
1da177e4 LT |
545 | { |
546 | struct rb_node *n; | |
547 | ||
548 | n = root->rb_node; | |
549 | if (!n) | |
550 | return NULL; | |
551 | while (n->rb_left) | |
552 | n = n->rb_left; | |
553 | return n; | |
554 | } | |
555 | EXPORT_SYMBOL(rb_first); | |
556 | ||
f4b477c4 | 557 | struct rb_node *rb_last(const struct rb_root *root) |
1da177e4 LT |
558 | { |
559 | struct rb_node *n; | |
560 | ||
561 | n = root->rb_node; | |
562 | if (!n) | |
563 | return NULL; | |
564 | while (n->rb_right) | |
565 | n = n->rb_right; | |
566 | return n; | |
567 | } | |
568 | EXPORT_SYMBOL(rb_last); | |
569 | ||
f4b477c4 | 570 | struct rb_node *rb_next(const struct rb_node *node) |
1da177e4 | 571 | { |
55a98102 DW |
572 | struct rb_node *parent; |
573 | ||
4c199a93 | 574 | if (RB_EMPTY_NODE(node)) |
10fd48f2 JA |
575 | return NULL; |
576 | ||
7ce6ff9e ML |
577 | /* |
578 | * If we have a right-hand child, go down and then left as far | |
579 | * as we can. | |
580 | */ | |
1da177e4 LT |
581 | if (node->rb_right) { |
582 | node = node->rb_right; | |
583 | while (node->rb_left) | |
584 | node=node->rb_left; | |
f4b477c4 | 585 | return (struct rb_node *)node; |
1da177e4 LT |
586 | } |
587 | ||
7ce6ff9e ML |
588 | /* |
589 | * No right-hand children. Everything down and left is smaller than us, | |
590 | * so any 'next' node must be in the general direction of our parent. | |
591 | * Go up the tree; any time the ancestor is a right-hand child of its | |
592 | * parent, keep going up. First time it's a left-hand child of its | |
593 | * parent, said parent is our 'next' node. | |
594 | */ | |
55a98102 DW |
595 | while ((parent = rb_parent(node)) && node == parent->rb_right) |
596 | node = parent; | |
1da177e4 | 597 | |
55a98102 | 598 | return parent; |
1da177e4 LT |
599 | } |
600 | EXPORT_SYMBOL(rb_next); | |
601 | ||
f4b477c4 | 602 | struct rb_node *rb_prev(const struct rb_node *node) |
1da177e4 | 603 | { |
55a98102 DW |
604 | struct rb_node *parent; |
605 | ||
4c199a93 | 606 | if (RB_EMPTY_NODE(node)) |
10fd48f2 JA |
607 | return NULL; |
608 | ||
7ce6ff9e ML |
609 | /* |
610 | * If we have a left-hand child, go down and then right as far | |
611 | * as we can. | |
612 | */ | |
1da177e4 LT |
613 | if (node->rb_left) { |
614 | node = node->rb_left; | |
615 | while (node->rb_right) | |
616 | node=node->rb_right; | |
f4b477c4 | 617 | return (struct rb_node *)node; |
1da177e4 LT |
618 | } |
619 | ||
7ce6ff9e ML |
620 | /* |
621 | * No left-hand children. Go up till we find an ancestor which | |
622 | * is a right-hand child of its parent. | |
623 | */ | |
55a98102 DW |
624 | while ((parent = rb_parent(node)) && node == parent->rb_left) |
625 | node = parent; | |
1da177e4 | 626 | |
55a98102 | 627 | return parent; |
1da177e4 LT |
628 | } |
629 | EXPORT_SYMBOL(rb_prev); | |
630 | ||
631 | void rb_replace_node(struct rb_node *victim, struct rb_node *new, | |
632 | struct rb_root *root) | |
633 | { | |
55a98102 | 634 | struct rb_node *parent = rb_parent(victim); |
1da177e4 LT |
635 | |
636 | /* Set the surrounding nodes to point to the replacement */ | |
7abc704a | 637 | __rb_change_child(victim, new, parent, root); |
1da177e4 | 638 | if (victim->rb_left) |
55a98102 | 639 | rb_set_parent(victim->rb_left, new); |
1da177e4 | 640 | if (victim->rb_right) |
55a98102 | 641 | rb_set_parent(victim->rb_right, new); |
1da177e4 LT |
642 | |
643 | /* Copy the pointers/colour from the victim to the replacement */ | |
644 | *new = *victim; | |
645 | } | |
646 | EXPORT_SYMBOL(rb_replace_node); |