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805e021f CE |
1 | /* |
2 | * Copyright (c) 2008 - 2010 Jason Evans <jasone@FreeBSD.org> | |
3 | * Copyright (c) 2011 Your File System Inc. | |
4 | * All rights reserved. | |
5 | * | |
6 | * Redistribution and use in source and binary forms, with or without | |
7 | * modification, are permitted provided that the following conditions | |
8 | * are met: | |
9 | * 1. Redistributions of source code must retain the above copyright | |
10 | * notice, this list of conditions and the following disclaimer. | |
11 | * 2. Redistributions in binary form must reproduce the above copyright | |
12 | * notice, this list of conditions and the following disclaimer in the | |
13 | * documentation and/or other materials provided with the distribution. | |
14 | * | |
15 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR | |
16 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
17 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
18 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
19 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
20 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
21 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
22 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
23 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
24 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
25 | */ | |
26 | ||
27 | /* Left-leaning rbtree implementation. Originally derived from the FreeBSD | |
28 | * CPP macro definitions by Jason Evans, but extensively modified to | |
29 | * *) Be function, rather than macro based | |
30 | * *) Use parent pointers, rather than calling an embeded comparison fn | |
31 | * *) Use 'NULL' to represent empty nodes, rather than a magic pointer | |
32 | */ | |
33 | ||
34 | #include <afsconfig.h> | |
35 | #include <afs/param.h> | |
36 | ||
37 | #ifdef KERNEL | |
38 | # include "afs/sysincludes.h" | |
39 | # include "afsincludes.h" | |
40 | #else | |
41 | # include <roken.h> | |
42 | #endif | |
43 | ||
44 | #include "rbtree.h" | |
45 | ||
46 | struct { | |
47 | struct opr_rbtree_node *left; | |
48 | struct opr_rbtree_node *right; | |
49 | struct opr_rbtree_node *parent; | |
50 | int red; | |
51 | } opr_rbtree_node; | |
52 | ||
53 | struct { | |
54 | struct opr_rbtree_node *root; | |
55 | } opr_rbtree; | |
56 | ||
57 | /* Update the parent pointers for a node which is being replaced. | |
58 | * | |
59 | * If the original node had no parent, then it was the root of the tree, | |
60 | * and the replacement is too. | |
61 | * Otherwise, the original node must have been either the left or right | |
62 | * child of its parent, so update the left (or right) pointer to point | |
63 | * to the replacement as appropriate. | |
64 | */ | |
65 | ||
66 | static_inline void | |
67 | update_parent_ptr(struct opr_rbtree *head, struct opr_rbtree_node *old, | |
68 | struct opr_rbtree_node *replacement) | |
69 | { | |
70 | if (old->parent) { | |
71 | if (old->parent->left == old) | |
72 | old->parent->left = replacement; | |
73 | else | |
74 | old->parent->right = replacement; | |
75 | } else | |
76 | head->root = replacement; | |
77 | } | |
78 | ||
79 | void | |
80 | opr_rbtree_init(struct opr_rbtree *head) | |
81 | { | |
82 | head->root = NULL; | |
83 | } | |
84 | ||
85 | struct opr_rbtree_node * | |
86 | opr_rbtree_first(struct opr_rbtree *head) | |
87 | { | |
88 | struct opr_rbtree_node *node; | |
89 | ||
90 | node = head->root; | |
91 | if (node == NULL) | |
92 | return node; | |
93 | ||
94 | while (node->left != NULL) | |
95 | node = node->left; | |
96 | ||
97 | return node; | |
98 | } | |
99 | ||
100 | struct opr_rbtree_node * | |
101 | opr_rbtree_last(struct opr_rbtree *head) | |
102 | { | |
103 | struct opr_rbtree_node *node; | |
104 | ||
105 | node = head->root; | |
106 | ||
107 | if (node == NULL) | |
108 | return node; | |
109 | ||
110 | while (node->right != NULL) | |
111 | node = node->right; | |
112 | ||
113 | return node; | |
114 | } | |
115 | ||
116 | ||
117 | struct opr_rbtree_node * | |
118 | opr_rbtree_next(struct opr_rbtree_node *node) | |
119 | { | |
120 | struct opr_rbtree_node *parent; | |
121 | ||
122 | /* Where there is a right child, the next node is to the right, then | |
123 | * left as far as we can go */ | |
124 | if (node->right != NULL) { | |
125 | node = node->right; | |
126 | while (node->left != NULL) | |
127 | node = node->left; | |
128 | ||
129 | return node; | |
130 | } | |
131 | ||
132 | /* If there is no right hand child, then the next node is above us. | |
133 | * Whenever our ancestor is a right-hand child, the next node is | |
134 | * further up. When it is a left-hand child, it is our next node | |
135 | */ | |
136 | while ((parent = node->parent) != NULL && node == parent->right) | |
137 | node = parent; | |
138 | ||
139 | return parent; | |
140 | } | |
141 | ||
142 | struct opr_rbtree_node * | |
143 | opr_rbtree_prev(struct opr_rbtree_node *node) | |
144 | { | |
145 | struct opr_rbtree_node *parent; | |
146 | ||
147 | if (node->left != NULL) { | |
148 | node = node->left; | |
149 | while (node->right != NULL) | |
150 | node = node->right; | |
151 | ||
152 | return node; | |
153 | } | |
154 | ||
155 | /* Same ancestor logic as for 'next', but in reverse */ | |
156 | while ((parent = node->parent) != NULL && node == parent->left) | |
157 | node = parent; | |
158 | ||
159 | return parent; | |
160 | } | |
161 | ||
162 | static_inline void | |
163 | rotateright(struct opr_rbtree *head, struct opr_rbtree_node *node) | |
164 | { | |
165 | struct opr_rbtree_node *left = node->left; | |
166 | ||
167 | node->left = left->right; | |
168 | if (left->right) | |
169 | left->right->parent = node; | |
170 | ||
171 | left->right = node; | |
172 | left->parent = node->parent; | |
173 | ||
174 | update_parent_ptr(head, node, left); | |
175 | ||
176 | node->parent = left; | |
177 | } | |
178 | ||
179 | static_inline void | |
180 | rotateleft(struct opr_rbtree *head, struct opr_rbtree_node *node) | |
181 | { | |
182 | struct opr_rbtree_node *right = node->right; | |
183 | ||
184 | node->right = right->left; | |
185 | if (right->left) | |
186 | right->left->parent = node; | |
187 | ||
188 | right->left = node; | |
189 | right->parent = node->parent; | |
190 | ||
191 | update_parent_ptr(head, node, right); | |
192 | ||
193 | node->parent = right; | |
194 | } | |
195 | ||
196 | static_inline void | |
197 | swapnode(struct opr_rbtree_node **a, struct opr_rbtree_node **b) | |
198 | { | |
199 | struct opr_rbtree_node *tmp; | |
200 | ||
201 | tmp = *a; | |
202 | *a = *b; | |
203 | *b = tmp; | |
204 | } | |
205 | ||
206 | static void | |
207 | insert_recolour(struct opr_rbtree *head, struct opr_rbtree_node *node) | |
208 | { | |
209 | struct opr_rbtree_node *parent, *gramps; | |
210 | ||
211 | while ((parent = node->parent) && parent->red) { | |
212 | gramps = parent->parent; | |
213 | ||
214 | if (parent == gramps->left) { | |
215 | struct opr_rbtree_node *uncle = gramps->right; | |
216 | ||
217 | if (uncle && uncle->red) { | |
218 | uncle->red = 0; | |
219 | parent->red = 0; | |
220 | gramps->red = 1; | |
221 | node = gramps; | |
222 | continue; | |
223 | } | |
224 | ||
225 | if (parent->right == node) { | |
226 | rotateleft(head, parent); | |
227 | swapnode(&parent, &node); | |
228 | } | |
229 | ||
230 | parent->red = 0; | |
231 | gramps->red = 1; | |
232 | rotateright(head, gramps); | |
233 | } else { | |
234 | struct opr_rbtree_node *uncle = gramps->left; | |
235 | ||
236 | if (uncle && uncle->red) { | |
237 | uncle->red = 0; | |
238 | parent->red = 0; | |
239 | gramps->red = 1; | |
240 | node = gramps; | |
241 | continue; | |
242 | } | |
243 | ||
244 | if (parent->left == node) { | |
245 | rotateright(head, parent); | |
246 | swapnode(&parent, &node); | |
247 | } | |
248 | ||
249 | parent->red = 0; | |
250 | gramps->red = 1; | |
251 | rotateleft(head, gramps); | |
252 | } | |
253 | } | |
254 | ||
255 | head->root->red = 0; | |
256 | } | |
257 | ||
258 | void | |
259 | opr_rbtree_insert(struct opr_rbtree *head, | |
260 | struct opr_rbtree_node *parent, | |
261 | struct opr_rbtree_node **childptr, | |
262 | struct opr_rbtree_node *node) | |
263 | { | |
264 | /* Link node 'node' into the tree at position 'parent', using either the | |
265 | * left or right pointers */ | |
266 | ||
267 | node->parent = parent; | |
268 | node->left = node->right = NULL; | |
269 | node->red = 1; | |
270 | *childptr = node; | |
271 | ||
272 | /* Rebalance the tree for the newly inserted node */ | |
273 | insert_recolour(head, node); | |
274 | } | |
275 | ||
276 | static void | |
277 | remove_recolour(struct opr_rbtree *head, struct opr_rbtree_node *parent, | |
278 | struct opr_rbtree_node *node) | |
279 | { | |
280 | struct opr_rbtree_node *other; | |
281 | ||
282 | while ((node == NULL || !node->red) && node != head->root) { | |
283 | if (parent->left == node) { | |
284 | other = parent->right; | |
285 | if (other->red) { | |
286 | other->red = 0; | |
287 | parent->red = 1; | |
288 | rotateleft(head, parent); | |
289 | other = parent->right; | |
290 | } | |
291 | if ((other->left == NULL || !other->left->red) && | |
292 | (other->right == NULL || !other->right->red)) { | |
293 | other->red = 1; | |
294 | node = parent; | |
295 | parent = node->parent; | |
296 | } else { | |
297 | if (other->right == NULL || !other->right->red) { | |
298 | other->left->red = 0; | |
299 | other->red = 1; | |
300 | rotateright(head, other); | |
301 | other = parent->right; | |
302 | } | |
303 | other->red = parent->red; | |
304 | parent->red = 0; | |
305 | other->right->red = 0; | |
306 | rotateleft(head, parent); | |
307 | node = head->root; | |
308 | break; | |
309 | } | |
310 | } else { | |
311 | other = parent->left; | |
312 | if (other->red) { | |
313 | other->red = 0; | |
314 | parent->red = 1; | |
315 | rotateright(head, parent); | |
316 | other = parent->left; | |
317 | } | |
318 | if ((other->left == NULL || !other->left->red) && | |
319 | (other->right == NULL || !other->right->red)) { | |
320 | other->red = 1; | |
321 | node = parent; | |
322 | parent = node->parent; | |
323 | } else { | |
324 | if (other->left == NULL || !other->left->red) { | |
325 | other->right->red = 0; | |
326 | other->red = 1; | |
327 | rotateleft(head, other); | |
328 | other = parent->left; | |
329 | } | |
330 | other->red = parent->red; | |
331 | parent->red = 0; | |
332 | other->left->red = 0; | |
333 | rotateright(head, parent); | |
334 | node = head->root; | |
335 | break; | |
336 | } | |
337 | } | |
338 | } | |
339 | if (node) | |
340 | node->red = 0; | |
341 | } | |
342 | ||
343 | void | |
344 | opr_rbtree_remove(struct opr_rbtree *head, struct opr_rbtree_node *node) | |
345 | { | |
346 | struct opr_rbtree_node *child, *parent; | |
347 | int red; | |
348 | ||
349 | ||
350 | if (node->left == NULL && node->right == NULL) { | |
351 | /* A node with no non-leaf children */ | |
352 | update_parent_ptr(head, node, NULL); | |
353 | ||
354 | if (!node->red) | |
355 | remove_recolour(head, node->parent, NULL); | |
356 | ||
357 | return; | |
358 | } | |
359 | ||
360 | if (node->left != NULL && node->right != NULL) { | |
361 | /* A node with two children. | |
362 | * | |
363 | * Move the next node in the tree (which will be a leaf node) | |
364 | * onto our tree current position, then rebalance as required | |
365 | */ | |
366 | struct opr_rbtree_node *old, *left; | |
367 | ||
368 | old = node; | |
369 | ||
370 | /* Set node to the next node in the tree from the current | |
371 | * position, where the next node is the left-most leaf node | |
372 | * in our right child */ | |
373 | node = node->right; | |
374 | while ((left = node->left) != NULL) | |
375 | node = left; | |
376 | ||
377 | /* Move 'node' into the position occupied by 'old', which is being | |
378 | * removed */ | |
379 | ||
380 | update_parent_ptr(head, old, node); | |
381 | ||
382 | child = node->right; | |
383 | parent = node->parent; | |
384 | red = node->red; | |
385 | ||
386 | /* As we're logically just copying the value, must preserve the | |
387 | * old node's colour */ | |
388 | node->red = old->red; | |
389 | ||
390 | /* ... and the old node's linkage */ | |
391 | if (parent == old) | |
392 | parent = node; | |
393 | else { | |
394 | if (child) | |
395 | child->parent = parent; | |
396 | parent->left = child; | |
397 | ||
398 | node->right = old->right; | |
399 | old->right->parent = node; | |
400 | } | |
401 | ||
402 | node->parent = old->parent; | |
403 | node->left = old->left; | |
404 | old->left->parent = node; | |
405 | ||
406 | /* If the node being removed was black, then we must recolour the | |
407 | * tree to maintain balance */ | |
408 | if (!red) | |
409 | remove_recolour(head, parent, child); | |
410 | ||
411 | return; | |
412 | } | |
413 | ||
414 | /* Only remaining option - node with a single child */ | |
415 | ||
416 | if (node->left == NULL) | |
417 | child = node->right; | |
418 | else | |
419 | child = node->left; | |
420 | ||
421 | child->parent = node->parent; | |
422 | ||
423 | update_parent_ptr(head, node, child); | |
424 | ||
425 | if (!node->red) | |
426 | remove_recolour(head, node->parent, child); | |
427 | } | |
428 | ||
429 | void | |
430 | opr_rbtree_replace(struct opr_rbtree *head, | |
431 | struct opr_rbtree_node *old, | |
432 | struct opr_rbtree_node *replacement) | |
433 | { | |
434 | /* Update our parent's pointer to us */ | |
435 | update_parent_ptr(head, old, replacement); | |
436 | ||
437 | /* And our children's pointers to us */ | |
438 | if (old->left) | |
439 | old->left->parent = replacement; | |
440 | if (old->right) | |
441 | old->right->parent = replacement; | |
442 | ||
443 | /* Copy over parent, left, right and colour */ | |
444 | *replacement = *old; | |
445 | } |