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>
24 #include <linux/module.h>
25
26 static void __rb_rotate_left(struct rb_node *node, struct rb_root *root)
27 {
28 struct rb_node *right = node->rb_right;
29 struct rb_node *parent = rb_parent(node);
30
31 if ((node->rb_right = right->rb_left))
32 rb_set_parent(right->rb_left, node);
33 right->rb_left = node;
34
35 rb_set_parent(right, parent);
36
37 if (parent)
38 {
39 if (node == parent->rb_left)
40 parent->rb_left = right;
41 else
42 parent->rb_right = right;
43 }
44 else
45 root->rb_node = right;
46 rb_set_parent(node, right);
47 }
48
49 static void __rb_rotate_right(struct rb_node *node, struct rb_root *root)
50 {
51 struct rb_node *left = node->rb_left;
52 struct rb_node *parent = rb_parent(node);
53
54 if ((node->rb_left = left->rb_right))
55 rb_set_parent(left->rb_right, node);
56 left->rb_right = node;
57
58 rb_set_parent(left, parent);
59
60 if (parent)
61 {
62 if (node == parent->rb_right)
63 parent->rb_right = left;
64 else
65 parent->rb_left = left;
66 }
67 else
68 root->rb_node = left;
69 rb_set_parent(node, left);
70 }
71
72 void rb_insert_color(struct rb_node *node, struct rb_root *root)
73 {
74 struct rb_node *parent, *gparent;
75
76 while ((parent = rb_parent(node)) && rb_is_red(parent))
77 {
78 gparent = rb_parent(parent);
79
80 if (parent == gparent->rb_left)
81 {
82 {
83 register struct rb_node *uncle = gparent->rb_right;
84 if (uncle && rb_is_red(uncle))
85 {
86 rb_set_black(uncle);
87 rb_set_black(parent);
88 rb_set_red(gparent);
89 node = gparent;
90 continue;
91 }
92 }
93
94 if (parent->rb_right == node)
95 {
96 register struct rb_node *tmp;
97 __rb_rotate_left(parent, root);
98 tmp = parent;
99 parent = node;
100 node = tmp;
101 }
102
103 rb_set_black(parent);
104 rb_set_red(gparent);
105 __rb_rotate_right(gparent, root);
106 } else {
107 {
108 register struct rb_node *uncle = gparent->rb_left;
109 if (uncle && rb_is_red(uncle))
110 {
111 rb_set_black(uncle);
112 rb_set_black(parent);
113 rb_set_red(gparent);
114 node = gparent;
115 continue;
116 }
117 }
118
119 if (parent->rb_left == node)
120 {
121 register struct rb_node *tmp;
122 __rb_rotate_right(parent, root);
123 tmp = parent;
124 parent = node;
125 node = tmp;
126 }
127
128 rb_set_black(parent);
129 rb_set_red(gparent);
130 __rb_rotate_left(gparent, root);
131 }
132 }
133
134 rb_set_black(root->rb_node);
135 }
136 EXPORT_SYMBOL(rb_insert_color);
137
138 static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
139 struct rb_root *root)
140 {
141 struct rb_node *other;
142
143 while ((!node || rb_is_black(node)) && node != root->rb_node)
144 {
145 if (parent->rb_left == node)
146 {
147 other = parent->rb_right;
148 if (rb_is_red(other))
149 {
150 rb_set_black(other);
151 rb_set_red(parent);
152 __rb_rotate_left(parent, root);
153 other = parent->rb_right;
154 }
155 if ((!other->rb_left || rb_is_black(other->rb_left)) &&
156 (!other->rb_right || rb_is_black(other->rb_right)))
157 {
158 rb_set_red(other);
159 node = parent;
160 parent = rb_parent(node);
161 }
162 else
163 {
164 if (!other->rb_right || rb_is_black(other->rb_right))
165 {
166 struct rb_node *o_left;
167 if ((o_left = other->rb_left))
168 rb_set_black(o_left);
169 rb_set_red(other);
170 __rb_rotate_right(other, root);
171 other = parent->rb_right;
172 }
173 rb_set_color(other, rb_color(parent));
174 rb_set_black(parent);
175 if (other->rb_right)
176 rb_set_black(other->rb_right);
177 __rb_rotate_left(parent, root);
178 node = root->rb_node;
179 break;
180 }
181 }
182 else
183 {
184 other = parent->rb_left;
185 if (rb_is_red(other))
186 {
187 rb_set_black(other);
188 rb_set_red(parent);
189 __rb_rotate_right(parent, root);
190 other = parent->rb_left;
191 }
192 if ((!other->rb_left || rb_is_black(other->rb_left)) &&
193 (!other->rb_right || rb_is_black(other->rb_right)))
194 {
195 rb_set_red(other);
196 node = parent;
197 parent = rb_parent(node);
198 }
199 else
200 {
201 if (!other->rb_left || rb_is_black(other->rb_left))
202 {
203 register struct rb_node *o_right;
204 if ((o_right = other->rb_right))
205 rb_set_black(o_right);
206 rb_set_red(other);
207 __rb_rotate_left(other, root);
208 other = parent->rb_left;
209 }
210 rb_set_color(other, rb_color(parent));
211 rb_set_black(parent);
212 if (other->rb_left)
213 rb_set_black(other->rb_left);
214 __rb_rotate_right(parent, root);
215 node = root->rb_node;
216 break;
217 }
218 }
219 }
220 if (node)
221 rb_set_black(node);
222 }
223
224 void rb_erase(struct rb_node *node, struct rb_root *root)
225 {
226 struct rb_node *child, *parent;
227 int color;
228
229 if (!node->rb_left)
230 child = node->rb_right;
231 else if (!node->rb_right)
232 child = node->rb_left;
233 else
234 {
235 struct rb_node *old = node, *left;
236
237 node = node->rb_right;
238 while ((left = node->rb_left) != NULL)
239 node = left;
240 child = node->rb_right;
241 parent = rb_parent(node);
242 color = rb_color(node);
243
244 if (child)
245 rb_set_parent(child, parent);
246 if (parent == old) {
247 parent->rb_right = child;
248 parent = node;
249 } else
250 parent->rb_left = child;
251
252 node->rb_parent_color = old->rb_parent_color;
253 node->rb_right = old->rb_right;
254 node->rb_left = old->rb_left;
255
256 if (rb_parent(old))
257 {
258 if (rb_parent(old)->rb_left == old)
259 rb_parent(old)->rb_left = node;
260 else
261 rb_parent(old)->rb_right = node;
262 } else
263 root->rb_node = node;
264
265 rb_set_parent(old->rb_left, node);
266 if (old->rb_right)
267 rb_set_parent(old->rb_right, node);
268 goto color;
269 }
270
271 parent = rb_parent(node);
272 color = rb_color(node);
273
274 if (child)
275 rb_set_parent(child, parent);
276 if (parent)
277 {
278 if (parent->rb_left == node)
279 parent->rb_left = child;
280 else
281 parent->rb_right = child;
282 }
283 else
284 root->rb_node = child;
285
286 color:
287 if (color == RB_BLACK)
288 __rb_erase_color(child, parent, root);
289 }
290 EXPORT_SYMBOL(rb_erase);
291
292 /*
293 * This function returns the first node (in sort order) of the tree.
294 */
295 struct rb_node *rb_first(struct rb_root *root)
296 {
297 struct rb_node *n;
298
299 n = root->rb_node;
300 if (!n)
301 return NULL;
302 while (n->rb_left)
303 n = n->rb_left;
304 return n;
305 }
306 EXPORT_SYMBOL(rb_first);
307
308 struct rb_node *rb_last(struct rb_root *root)
309 {
310 struct rb_node *n;
311
312 n = root->rb_node;
313 if (!n)
314 return NULL;
315 while (n->rb_right)
316 n = n->rb_right;
317 return n;
318 }
319 EXPORT_SYMBOL(rb_last);
320
321 struct rb_node *rb_next(struct rb_node *node)
322 {
323 struct rb_node *parent;
324
325 if (rb_parent(node) == node)
326 return NULL;
327
328 /* If we have a right-hand child, go down and then left as far
329 as we can. */
330 if (node->rb_right) {
331 node = node->rb_right;
332 while (node->rb_left)
333 node=node->rb_left;
334 return node;
335 }
336
337 /* No right-hand children. Everything down and left is
338 smaller than us, so any 'next' node must be in the general
339 direction of our parent. Go up the tree; any time the
340 ancestor is a right-hand child of its parent, keep going
341 up. First time it's a left-hand child of its parent, said
342 parent is our 'next' node. */
343 while ((parent = rb_parent(node)) && node == parent->rb_right)
344 node = parent;
345
346 return parent;
347 }
348 EXPORT_SYMBOL(rb_next);
349
350 struct rb_node *rb_prev(struct rb_node *node)
351 {
352 struct rb_node *parent;
353
354 if (rb_parent(node) == node)
355 return NULL;
356
357 /* If we have a left-hand child, go down and then right as far
358 as we can. */
359 if (node->rb_left) {
360 node = node->rb_left;
361 while (node->rb_right)
362 node=node->rb_right;
363 return node;
364 }
365
366 /* No left-hand children. Go up till we find an ancestor which
367 is a right-hand child of its parent */
368 while ((parent = rb_parent(node)) && node == parent->rb_left)
369 node = parent;
370
371 return parent;
372 }
373 EXPORT_SYMBOL(rb_prev);
374
375 void rb_replace_node(struct rb_node *victim, struct rb_node *new,
376 struct rb_root *root)
377 {
378 struct rb_node *parent = rb_parent(victim);
379
380 /* Set the surrounding nodes to point to the replacement */
381 if (parent) {
382 if (victim == parent->rb_left)
383 parent->rb_left = new;
384 else
385 parent->rb_right = new;
386 } else {
387 root->rb_node = new;
388 }
389 if (victim->rb_left)
390 rb_set_parent(victim->rb_left, new);
391 if (victim->rb_right)
392 rb_set_parent(victim->rb_right, new);
393
394 /* Copy the pointers/colour from the victim to the replacement */
395 *new = *victim;
396 }
397 EXPORT_SYMBOL(rb_replace_node);
398
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