1 /*	$NetBSD: btree.c,v 1.1.1.1 2008/12/22 00:17:54 haad Exp $	*/
2 
3 /*
4  * Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
5  * Copyright (C) 2004-2007 Red Hat, Inc. All rights reserved.
6  *
7  * This file is part of LVM2.
8  *
9  * This copyrighted material is made available to anyone wishing to use,
10  * modify, copy, or redistribute it subject to the terms and conditions
11  * of the GNU Lesser General Public License v.2.1.
12  *
13  * You should have received a copy of the GNU Lesser General Public License
14  * along with this program; if not, write to the Free Software Foundation,
15  * Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
16  */
17 
18 #include "lib.h"
19 #include "btree.h"
20 
21 struct node {
22 	uint32_t key;
23 	struct node *l, *r, *p;
24 
25 	void *data;
26 };
27 
28 struct btree {
29 	struct dm_pool *mem;
30 	struct node *root;
31 };
32 
33 struct btree *btree_create(struct dm_pool *mem)
34 {
35 	struct btree *t = dm_pool_alloc(mem, sizeof(*t));
36 
37 	if (t) {
38 		t->mem = mem;
39 		t->root = NULL;
40 	}
41 
42 	return t;
43 }
44 
45 /*
46  * Shuffle the bits in a key, to try and remove
47  * any ordering.
48  */
49 static uint32_t _shuffle(uint32_t k)
50 {
51 #if 1
52 	return ((k & 0xff) << 24 |
53 		(k & 0xff00) << 8 |
54 		(k & 0xff0000) >> 8 | (k & 0xff000000) >> 24);
55 #else
56 	return k;
57 #endif
58 }
59 
60 static struct node **_lookup(struct node *const *c, uint32_t key,
61 			     struct node **p)
62 {
63 	*p = NULL;
64 	while (*c) {
65 		*p = *c;
66 		if ((*c)->key == key)
67 			break;
68 
69 		if (key < (*c)->key)
70 			c = &(*c)->l;
71 
72 		else
73 			c = &(*c)->r;
74 	}
75 
76 	return (struct node **)c;
77 }
78 
79 void *btree_lookup(const struct btree *t, uint32_t k)
80 {
81 	uint32_t key = _shuffle(k);
82 	struct node *p, **c = _lookup(&t->root, key, &p);
83 	return (*c) ? (*c)->data : NULL;
84 }
85 
86 int btree_insert(struct btree *t, uint32_t k, void *data)
87 {
88 	uint32_t key = _shuffle(k);
89 	struct node *p, **c = _lookup(&t->root, key, &p), *n;
90 
91 	if (!*c) {
92 		if (!(n = dm_pool_alloc(t->mem, sizeof(*n))))
93 			return_0;
94 
95 		n->key = key;
96 		n->data = data;
97 		n->l = n->r = NULL;
98 		n->p = p;
99 
100 		*c = n;
101 	}
102 
103 	return 1;
104 }
105 
106 void *btree_get_data(const struct btree_iter *it)
107 {
108 	return ((struct node *) it)->data;
109 }
110 
111 static struct node *_left(struct node *n)
112 {
113 	while (n->l)
114 		n = n->l;
115 	return n;
116 }
117 
118 struct btree_iter *btree_first(const struct btree *t)
119 {
120 	if (!t->root)
121 		return NULL;
122 
123 	return (struct btree_iter *) _left(t->root);
124 }
125 
126 struct btree_iter *btree_next(const struct btree_iter *it)
127 {
128 	struct node *n = (struct node *) it;
129 	uint32_t k = n->key;
130 
131 	if (n->r)
132 		return (struct btree_iter *) _left(n->r);
133 
134 	do
135 		n = n->p;
136 	while (n && k > n->key);
137 
138 	return (struct btree_iter *) n;
139 }
140