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Merge tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/arm...
[linux-2.6.git] / lib / rbtree.c
blob65f4effd117f4350bb5dde964eab219f67caf701
1 /*
2 Red Black Trees
3 (C) 1999 Andrea Arcangeli <andrea@suse.de>
4 (C) 2002 David Woodhouse <dwmw2@infradead.org>
5 (C) 2012 Michel Lespinasse <walken@google.com>
6
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_augmented.h>
25 #include <linux/export.h>
26
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
43 * nodes will be lowercase. Unknown color nodes shall be drawn as red within
44 * parentheses and have some accompanying text comment.
45 */
46
47 static inline void rb_set_black(struct rb_node *rb)
48 {
49 rb->__rb_parent_color |= RB_BLACK;
50 }
51
52 static inline struct rb_node *rb_red_parent(struct rb_node *red)
53 {
54 return (struct rb_node *)red->__rb_parent_color;
55 }
56
57 /*
58 * Helper function for rotations:
59 * - old's parent and color get assigned to new
60 * - old gets assigned new as a parent and 'color' as a color.
61 */
62 static inline void
63 __rb_rotate_set_parents(struct rb_node *old, struct rb_node *new,
64 struct rb_root *root, int color)
65 {
66 struct rb_node *parent = rb_parent(old);
67 new->__rb_parent_color = old->__rb_parent_color;
68 rb_set_parent_color(old, new, color);
69 __rb_change_child(old, new, parent, root);
70 }
71
72 static __always_inline void
73 __rb_insert(struct rb_node *node, struct rb_root *root,
74 void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
75 {
76 struct rb_node *parent = rb_red_parent(node), *gparent, *tmp;
77
78 while (true) {
79 /*
80 * Loop invariant: node is red
81 *
82 * If there is a black parent, we are done.
83 * Otherwise, take some corrective action as we don't
84 * want a red root or two consecutive red nodes.
85 */
86 if (!parent) {
87 rb_set_parent_color(node, NULL, RB_BLACK);
88 break;
89 } else if (rb_is_black(parent))
90 break;
91
92 gparent = rb_red_parent(parent);
93
94 tmp = gparent->rb_right;
95 if (parent != tmp) { /* parent == gparent->rb_left */
96 if (tmp && rb_is_red(tmp)) {
97 /*
98 * Case 1 - color flips
99 *
100 * G g
101 * / \ / \
102 * p u --> P U
103 * / /
104 * n N
105 *
106 * However, since g's parent might be red, and
107 * 4) does not allow this, we need to recurse
108 * at g.
109 */
110 rb_set_parent_color(tmp, gparent, RB_BLACK);
111 rb_set_parent_color(parent, gparent, RB_BLACK);
112 node = gparent;
113 parent = rb_parent(node);
114 rb_set_parent_color(node, parent, RB_RED);
115 continue;
116 }
117
118 tmp = parent->rb_right;
119 if (node == tmp) {
120 /*
121 * Case 2 - left rotate at parent
122 *
123 * G G
124 * / \ / \
125 * p U --> n U
126 * \ /
127 * n p
128 *
129 * This still leaves us in violation of 4), the
130 * continuation into Case 3 will fix that.
131 */
132 parent->rb_right = tmp = node->rb_left;
133 node->rb_left = parent;
134 if (tmp)
135 rb_set_parent_color(tmp, parent,
136 RB_BLACK);
137 rb_set_parent_color(parent, node, RB_RED);
138 augment_rotate(parent, node);
139 parent = node;
140 tmp = node->rb_right;
141 }
142
143 /*
144 * Case 3 - right rotate at gparent
145 *
146 * G P
147 * / \ / \
148 * p U --> n g
149 * / \
150 * n U
151 */
152 gparent->rb_left = tmp; /* == parent->rb_right */
153 parent->rb_right = gparent;
154 if (tmp)
155 rb_set_parent_color(tmp, gparent, RB_BLACK);
156 __rb_rotate_set_parents(gparent, parent, root, RB_RED);
157 augment_rotate(gparent, parent);
158 break;
159 } else {
160 tmp = gparent->rb_left;
161 if (tmp && rb_is_red(tmp)) {
162 /* Case 1 - color flips */
163 rb_set_parent_color(tmp, gparent, RB_BLACK);
164 rb_set_parent_color(parent, gparent, RB_BLACK);
165 node = gparent;
166 parent = rb_parent(node);
167 rb_set_parent_color(node, parent, RB_RED);
168 continue;
169 }
170
171 tmp = parent->rb_left;
172 if (node == tmp) {
173 /* Case 2 - right rotate at parent */
174 parent->rb_left = tmp = node->rb_right;
175 node->rb_right = parent;
176 if (tmp)
177 rb_set_parent_color(tmp, parent,
178 RB_BLACK);
179 rb_set_parent_color(parent, node, RB_RED);
180 augment_rotate(parent, node);
181 parent = node;
182 tmp = node->rb_left;
183 }
184
185 /* Case 3 - left rotate at gparent */
186 gparent->rb_right = tmp; /* == parent->rb_left */
187 parent->rb_left = gparent;
188 if (tmp)
189 rb_set_parent_color(tmp, gparent, RB_BLACK);
190 __rb_rotate_set_parents(gparent, parent, root, RB_RED);
191 augment_rotate(gparent, parent);
192 break;
193 }
194 }
195 }
196
197 /*
198 * Inline version for rb_erase() use - we want to be able to inline
199 * and eliminate the dummy_rotate callback there
200 */
201 static __always_inline void
202 ____rb_erase_color(struct rb_node *parent, struct rb_root *root,
203 void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
204 {
205 struct rb_node *node = NULL, *sibling, *tmp1, *tmp2;
206
207 while (true) {
208 /*
209 * Loop invariants:
210 * - node is black (or NULL on first iteration)
211 * - node is not the root (parent is not NULL)
212 * - All leaf paths going through parent and node have a
213 * black node count that is 1 lower than other leaf paths.
214 */
215 sibling = parent->rb_right;
216 if (node != sibling) { /* node == parent->rb_left */
217 if (rb_is_red(sibling)) {
218 /*
219 * Case 1 - left rotate at parent
220 *
221 * P S
222 * / \ / \
223 * N s --> p Sr
224 * / \ / \
225 * Sl Sr N Sl
226 */
227 parent->rb_right = tmp1 = sibling->rb_left;
228 sibling->rb_left = parent;
229 rb_set_parent_color(tmp1, parent, RB_BLACK);
230 __rb_rotate_set_parents(parent, sibling, root,
231 RB_RED);
232 augment_rotate(parent, sibling);
233 sibling = tmp1;
234 }
235 tmp1 = sibling->rb_right;
236 if (!tmp1 || rb_is_black(tmp1)) {
237 tmp2 = sibling->rb_left;
238 if (!tmp2 || rb_is_black(tmp2)) {
239 /*
240 * Case 2 - sibling color flip
241 * (p could be either color here)
242 *
243 * (p) (p)
244 * / \ / \
245 * N S --> N s
246 * / \ / \
247 * Sl Sr Sl Sr
248 *
249 * This leaves us violating 5) which
250 * can be fixed by flipping p to black
251 * if it was red, or by recursing at p.
252 * p is red when coming from Case 1.
253 */
254 rb_set_parent_color(sibling, parent,
255 RB_RED);
256 if (rb_is_red(parent))
257 rb_set_black(parent);
258 else {
259 node = parent;
260 parent = rb_parent(node);
261 if (parent)
262 continue;
263 }
264 break;
265 }
266 /*
267 * Case 3 - right rotate at sibling
268 * (p could be either color here)
269 *
270 * (p) (p)
271 * / \ / \
272 * N S --> N Sl
273 * / \ \
274 * sl Sr s
275 * \
276 * Sr
277 */
278 sibling->rb_left = tmp1 = tmp2->rb_right;
279 tmp2->rb_right = sibling;
280 parent->rb_right = tmp2;
281 if (tmp1)
282 rb_set_parent_color(tmp1, sibling,
283 RB_BLACK);
284 augment_rotate(sibling, tmp2);
285 tmp1 = sibling;
286 sibling = tmp2;
287 }
288 /*
289 * Case 4 - left rotate at parent + color flips
290 * (p and sl could be either color here.
291 * After rotation, p becomes black, s acquires
292 * p's color, and sl keeps its color)
293 *
294 * (p) (s)
295 * / \ / \
296 * N S --> P Sr
297 * / \ / \
298 * (sl) sr N (sl)
299 */
300 parent->rb_right = tmp2 = sibling->rb_left;
301 sibling->rb_left = parent;
302 rb_set_parent_color(tmp1, sibling, RB_BLACK);
303 if (tmp2)
304 rb_set_parent(tmp2, parent);
305 __rb_rotate_set_parents(parent, sibling, root,
306 RB_BLACK);
307 augment_rotate(parent, sibling);
308 break;
309 } else {
310 sibling = parent->rb_left;
311 if (rb_is_red(sibling)) {
312 /* Case 1 - right rotate at parent */
313 parent->rb_left = tmp1 = sibling->rb_right;
314 sibling->rb_right = parent;
315 rb_set_parent_color(tmp1, parent, RB_BLACK);
316 __rb_rotate_set_parents(parent, sibling, root,
317 RB_RED);
318 augment_rotate(parent, sibling);
319 sibling = tmp1;
320 }
321 tmp1 = sibling->rb_left;
322 if (!tmp1 || rb_is_black(tmp1)) {
323 tmp2 = sibling->rb_right;
324 if (!tmp2 || rb_is_black(tmp2)) {
325 /* Case 2 - sibling color flip */
326 rb_set_parent_color(sibling, parent,
327 RB_RED);
328 if (rb_is_red(parent))
329 rb_set_black(parent);
330 else {
331 node = parent;
332 parent = rb_parent(node);
333 if (parent)
334 continue;
335 }
336 break;
337 }
338 /* Case 3 - right rotate at sibling */
339 sibling->rb_right = tmp1 = tmp2->rb_left;
340 tmp2->rb_left = sibling;
341 parent->rb_left = tmp2;
342 if (tmp1)
343 rb_set_parent_color(tmp1, sibling,
344 RB_BLACK);
345 augment_rotate(sibling, tmp2);
346 tmp1 = sibling;
347 sibling = tmp2;
348 }
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);
357 augment_rotate(parent, sibling);
358 break;
359 }
360 }
361 }
362
363 /* Non-inline version for rb_erase_augmented() use */
364 void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
365 void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
366 {
367 ____rb_erase_color(parent, root, augment_rotate);
368 }
369 EXPORT_SYMBOL(__rb_erase_color);
370
371 /*
372 * Non-augmented rbtree manipulation functions.
373 *
374 * We use dummy augmented callbacks here, and have the compiler optimize them
375 * out of the rb_insert_color() and rb_erase() function definitions.
376 */
377
378 static inline void dummy_propagate(struct rb_node *node, struct rb_node *stop) {}
379 static inline void dummy_copy(struct rb_node *old, struct rb_node *new) {}
380 static inline void dummy_rotate(struct rb_node *old, struct rb_node *new) {}
381
382 static const struct rb_augment_callbacks dummy_callbacks = {
383 dummy_propagate, dummy_copy, dummy_rotate
384 };
385
386 void rb_insert_color(struct rb_node *node, struct rb_root *root)
387 {
388 __rb_insert(node, root, dummy_rotate);
389 }
390 EXPORT_SYMBOL(rb_insert_color);
391
392 void rb_erase(struct rb_node *node, struct rb_root *root)
393 {
394 struct rb_node *rebalance;
395 rebalance = __rb_erase_augmented(node, root, &dummy_callbacks);
396 if (rebalance)
397 ____rb_erase_color(rebalance, root, dummy_rotate);
398 }
399 EXPORT_SYMBOL(rb_erase);
400
401 /*
402 * Augmented rbtree manipulation functions.
403 *
404 * This instantiates the same __always_inline functions as in the non-augmented
405 * case, but this time with user-defined callbacks.
406 */
407
408 void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
409 void (*augment_rotate)(struct rb_node *old, struct rb_node *new))
410 {
411 __rb_insert(node, root, augment_rotate);
412 }
413 EXPORT_SYMBOL(__rb_insert_augmented);
414
415 /*
416 * This function returns the first node (in sort order) of the tree.
417 */
418 struct rb_node *rb_first(const struct rb_root *root)
419 {
420 struct rb_node *n;
421
422 n = root->rb_node;
423 if (!n)
424 return NULL;
425 while (n->rb_left)
426 n = n->rb_left;
427 return n;
428 }
429 EXPORT_SYMBOL(rb_first);
430
431 struct rb_node *rb_last(const struct rb_root *root)
432 {
433 struct rb_node *n;
434
435 n = root->rb_node;
436 if (!n)
437 return NULL;
438 while (n->rb_right)
439 n = n->rb_right;
440 return n;
441 }
442 EXPORT_SYMBOL(rb_last);
443
444 struct rb_node *rb_next(const struct rb_node *node)
445 {
446 struct rb_node *parent;
447
448 if (RB_EMPTY_NODE(node))
449 return NULL;
450
451 /*
452 * If we have a right-hand child, go down and then left as far
453 * as we can.
454 */
455 if (node->rb_right) {
456 node = node->rb_right;
457 while (node->rb_left)
458 node=node->rb_left;
459 return (struct rb_node *)node;
460 }
461
462 /*
463 * No right-hand children. Everything down and left is smaller than us,
464 * so any 'next' node must be in the general direction of our parent.
465 * Go up the tree; any time the ancestor is a right-hand child of its
466 * parent, keep going up. First time it's a left-hand child of its
467 * parent, said parent is our 'next' node.
468 */
469 while ((parent = rb_parent(node)) && node == parent->rb_right)
470 node = parent;
471
472 return parent;
473 }
474 EXPORT_SYMBOL(rb_next);
475
476 struct rb_node *rb_prev(const struct rb_node *node)
477 {
478 struct rb_node *parent;
479
480 if (RB_EMPTY_NODE(node))
481 return NULL;
482
483 /*
484 * If we have a left-hand child, go down and then right as far
485 * as we can.
486 */
487 if (node->rb_left) {
488 node = node->rb_left;
489 while (node->rb_right)
490 node=node->rb_right;
491 return (struct rb_node *)node;
492 }
493
494 /*
495 * No left-hand children. Go up till we find an ancestor which
496 * is a right-hand child of its parent.
497 */
498 while ((parent = rb_parent(node)) && node == parent->rb_left)
499 node = parent;
500
501 return parent;
502 }
503 EXPORT_SYMBOL(rb_prev);
504
505 void rb_replace_node(struct rb_node *victim, struct rb_node *new,
506 struct rb_root *root)
507 {
508 struct rb_node *parent = rb_parent(victim);
509
510 /* Set the surrounding nodes to point to the replacement */
511 __rb_change_child(victim, new, parent, root);
512 if (victim->rb_left)
513 rb_set_parent(victim->rb_left, new);
514 if (victim->rb_right)
515 rb_set_parent(victim->rb_right, new);
516
517 /* Copy the pointers/colour from the victim to the replacement */
518 *new = *victim;
519 }
520 EXPORT_SYMBOL(rb_replace_node);
521
522 static struct rb_node *rb_left_deepest_node(const struct rb_node *node)
523 {
524 for (;;) {
525 if (node->rb_left)
526 node = node->rb_left;
527 else if (node->rb_right)
528 node = node->rb_right;
529 else
530 return (struct rb_node *)node;
531 }
532 }
533
534 struct rb_node *rb_next_postorder(const struct rb_node *node)
535 {
536 const struct rb_node *parent;
537 if (!node)
538 return NULL;
539 parent = rb_parent(node);
540
541 /* If we're sitting on node, we've already seen our children */
542 if (parent && node == parent->rb_left && parent->rb_right) {
543 /* If we are the parent's left node, go to the parent's right
544 * node then all the way down to the left */
545 return rb_left_deepest_node(parent->rb_right);
546 } else
547 /* Otherwise we are the parent's right node, and the parent
548 * should be next */
549 return (struct rb_node *)parent;
550 }
551 EXPORT_SYMBOL(rb_next_postorder);
552
553 struct rb_node *rb_first_postorder(const struct rb_root *root)
554 {
555 if (!root->rb_node)
556 return NULL;
557
558 return rb_left_deepest_node(root->rb_node);
559 }
560 EXPORT_SYMBOL(rb_first_postorder);
Linus' kernel tree