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
26static 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
49static 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
72void 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}
136EXPORT_SYMBOL(rb_insert_color);
137
138static 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					rb_set_black(other->rb_left);
167					rb_set_red(other);
168					__rb_rotate_right(other, root);
169					other = parent->rb_right;
170				}
171				rb_set_color(other, rb_color(parent));
172				rb_set_black(parent);
173				rb_set_black(other->rb_right);
174				__rb_rotate_left(parent, root);
175				node = root->rb_node;
176				break;
177			}
178		}
179		else
180		{
181			other = parent->rb_left;
182			if (rb_is_red(other))
183			{
184				rb_set_black(other);
185				rb_set_red(parent);
186				__rb_rotate_right(parent, root);
187				other = parent->rb_left;
188			}
189			if ((!other->rb_left || rb_is_black(other->rb_left)) &&
190			    (!other->rb_right || rb_is_black(other->rb_right)))
191			{
192				rb_set_red(other);
193				node = parent;
194				parent = rb_parent(node);
195			}
196			else
197			{
198				if (!other->rb_left || rb_is_black(other->rb_left))
199				{
200					rb_set_black(other->rb_right);
201					rb_set_red(other);
202					__rb_rotate_left(other, root);
203					other = parent->rb_left;
204				}
205				rb_set_color(other, rb_color(parent));
206				rb_set_black(parent);
207				rb_set_black(other->rb_left);
208				__rb_rotate_right(parent, root);
209				node = root->rb_node;
210				break;
211			}
212		}
213	}
214	if (node)
215		rb_set_black(node);
216}
217
218void rb_erase(struct rb_node *node, struct rb_root *root)
219{
220	struct rb_node *child, *parent;
221	int color;
222
223	if (!node->rb_left)
224		child = node->rb_right;
225	else if (!node->rb_right)
226		child = node->rb_left;
227	else
228	{
229		struct rb_node *old = node, *left;
230
231		node = node->rb_right;
232		while ((left = node->rb_left) != NULL)
233			node = left;
234
235		if (rb_parent(old)) {
236			if (rb_parent(old)->rb_left == old)
237				rb_parent(old)->rb_left = node;
238			else
239				rb_parent(old)->rb_right = node;
240		} else
241			root->rb_node = node;
242
243		child = node->rb_right;
244		parent = rb_parent(node);
245		color = rb_color(node);
246
247		if (parent == old) {
248			parent = node;
249		} else {
250			if (child)
251				rb_set_parent(child, parent);
252			parent->rb_left = child;
253
254			node->rb_right = old->rb_right;
255			rb_set_parent(old->rb_right, node);
256		}
257
258		node->rb_parent_color = old->rb_parent_color;
259		node->rb_left = old->rb_left;
260		rb_set_parent(old->rb_left, node);
261
262		goto color;
263	}
264
265	parent = rb_parent(node);
266	color = rb_color(node);
267
268	if (child)
269		rb_set_parent(child, parent);
270	if (parent)
271	{
272		if (parent->rb_left == node)
273			parent->rb_left = child;
274		else
275			parent->rb_right = child;
276	}
277	else
278		root->rb_node = child;
279
280 color:
281	if (color == RB_BLACK)
282		__rb_erase_color(child, parent, root);
283}
284EXPORT_SYMBOL(rb_erase);
285
286static void rb_augment_path(struct rb_node *node, rb_augment_f func, void *data)
287{
288	struct rb_node *parent;
289
290up:
291	func(node, data);
292	parent = rb_parent(node);
293	if (!parent)
294		return;
295
296	if (node == parent->rb_left && parent->rb_right)
297		func(parent->rb_right, data);
298	else if (parent->rb_left)
299		func(parent->rb_left, data);
300
301	node = parent;
302	goto up;
303}
304
305/*
306 * after inserting @node into the tree, update the tree to account for
307 * both the new entry and any damage done by rebalance
308 */
309void rb_augment_insert(struct rb_node *node, rb_augment_f func, void *data)
310{
311	if (node->rb_left)
312		node = node->rb_left;
313	else if (node->rb_right)
314		node = node->rb_right;
315
316	rb_augment_path(node, func, data);
317}
318
319/*
320 * before removing the node, find the deepest node on the rebalance path
321 * that will still be there after @node gets removed
322 */
323struct rb_node *rb_augment_erase_begin(struct rb_node *node)
324{
325	struct rb_node *deepest;
326
327	if (!node->rb_right && !node->rb_left)
328		deepest = rb_parent(node);
329	else if (!node->rb_right)
330		deepest = node->rb_left;
331	else if (!node->rb_left)
332		deepest = node->rb_right;
333	else {
334		deepest = rb_next(node);
335		if (deepest->rb_right)
336			deepest = deepest->rb_right;
337		else if (rb_parent(deepest) != node)
338			deepest = rb_parent(deepest);
339	}
340
341	return deepest;
342}
343
344/*
345 * after removal, update the tree to account for the removed entry
346 * and any rebalance damage.
347 */
348void rb_augment_erase_end(struct rb_node *node, rb_augment_f func, void *data)
349{
350	if (node)
351		rb_augment_path(node, func, data);
352}
353
354/*
355 * This function returns the first node (in sort order) of the tree.
356 */
357struct rb_node *rb_first(const struct rb_root *root)
358{
359	struct rb_node	*n;
360
361	n = root->rb_node;
362	if (!n)
363		return NULL;
364	while (n->rb_left)
365		n = n->rb_left;
366	return n;
367}
368EXPORT_SYMBOL(rb_first);
369
370struct rb_node *rb_last(const struct rb_root *root)
371{
372	struct rb_node	*n;
373
374	n = root->rb_node;
375	if (!n)
376		return NULL;
377	while (n->rb_right)
378		n = n->rb_right;
379	return n;
380}
381EXPORT_SYMBOL(rb_last);
382
383struct rb_node *rb_next(const struct rb_node *node)
384{
385	struct rb_node *parent;
386
387	if (rb_parent(node) == node)
388		return NULL;
389
390	/* If we have a right-hand child, go down and then left as far
391	   as we can. */
392	if (node->rb_right) {
393		node = node->rb_right;
394		while (node->rb_left)
395			node=node->rb_left;
396		return (struct rb_node *)node;
397	}
398
399	/* No right-hand children.  Everything down and left is
400	   smaller than us, so any 'next' node must be in the general
401	   direction of our parent. Go up the tree; any time the
402	   ancestor is a right-hand child of its parent, keep going
403	   up. First time it's a left-hand child of its parent, said
404	   parent is our 'next' node. */
405	while ((parent = rb_parent(node)) && node == parent->rb_right)
406		node = parent;
407
408	return parent;
409}
410EXPORT_SYMBOL(rb_next);
411
412struct rb_node *rb_prev(const struct rb_node *node)
413{
414	struct rb_node *parent;
415
416	if (rb_parent(node) == node)
417		return NULL;
418
419	/* If we have a left-hand child, go down and then right as far
420	   as we can. */
421	if (node->rb_left) {
422		node = node->rb_left;
423		while (node->rb_right)
424			node=node->rb_right;
425		return (struct rb_node *)node;
426	}
427
428	/* No left-hand children. Go up till we find an ancestor which
429	   is a right-hand child of its parent */
430	while ((parent = rb_parent(node)) && node == parent->rb_left)
431		node = parent;
432
433	return parent;
434}
435EXPORT_SYMBOL(rb_prev);
436
437void rb_replace_node(struct rb_node *victim, struct rb_node *new,
438		     struct rb_root *root)
439{
440	struct rb_node *parent = rb_parent(victim);
441
442	/* Set the surrounding nodes to point to the replacement */
443	if (parent) {
444		if (victim == parent->rb_left)
445			parent->rb_left = new;
446		else
447			parent->rb_right = new;
448	} else {
449		root->rb_node = new;
450	}
451	if (victim->rb_left)
452		rb_set_parent(victim->rb_left, new);
453	if (victim->rb_right)
454		rb_set_parent(victim->rb_right, new);
455
456	/* Copy the pointers/colour from the victim to the replacement */
457	*new = *victim;
458}
459EXPORT_SYMBOL(rb_replace_node);
460