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