summaryrefslogtreecommitdiff
path: root/kern/rbtree_i.h
blob: 69dfb9d0d3e1eae16b182c1a43485559499ed792 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
/*
 * Copyright (c) 2010, 2011 Richard Braun.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef _KERN_RBTREE_I_H
#define _KERN_RBTREE_I_H

#include <kern/assert.h>

/*
 * Red-black node structure.
 *
 * To reduce the number of branches and the instruction cache footprint,
 * the left and right child pointers are stored in an array, and the symmetry
 * of most tree operations is exploited by using left/right variables when
 * referring to children.
 *
 * In addition, this implementation assumes that all nodes are 4-byte aligned,
 * so that the least significant bit of the parent member can be used to store
 * the color of the node. This is true for all modern 32 and 64 bits
 * architectures, as long as the nodes aren't embedded in structures with
 * special alignment constraints such as member packing.
 */
struct rbtree_node {
    unsigned long parent;
    struct rbtree_node *children[2];
};

/*
 * Red-black tree structure.
 */
struct rbtree {
    struct rbtree_node *root;
};

/*
 * Masks applied on the parent member of a node to obtain either the
 * color or the parent address.
 */
#define RBTREE_COLOR_MASK   0x1UL
#define RBTREE_PARENT_MASK  (~0x3UL)

/*
 * Node colors.
 */
#define RBTREE_COLOR_RED    0
#define RBTREE_COLOR_BLACK  1

/*
 * Masks applied on slots to obtain either the child index or the parent
 * address.
 */
#define RBTREE_SLOT_INDEX_MASK  0x1UL
#define RBTREE_SLOT_PARENT_MASK (~RBTREE_SLOT_INDEX_MASK)

/*
 * Return true if the given pointer is suitably aligned.
 */
static inline int rbtree_check_alignment(const struct rbtree_node *node)
{
    return ((unsigned long)node & (~RBTREE_PARENT_MASK)) == 0;
}

/*
 * Return true if the given index is a valid child index.
 */
static inline int rbtree_check_index(int index)
{
    return index == (index & 1);
}

/*
 * Convert the result of a comparison into an index in the children array
 * (0 or 1).
 *
 * This function is mostly used when looking up a node.
 */
static inline int rbtree_d2i(int diff)
{
    return !(diff <= 0);
}

/*
 * Return the parent of a node.
 */
static inline struct rbtree_node * rbtree_parent(const struct rbtree_node *node)
{
    return (struct rbtree_node *)(node->parent & RBTREE_PARENT_MASK);
}

/*
 * Translate an insertion point into a slot.
 */
static inline unsigned long rbtree_slot(struct rbtree_node *parent, int index)
{
    assert(rbtree_check_alignment(parent));
    assert(rbtree_check_index(index));
    return (unsigned long)parent | index;
}

/*
 * Extract the parent address from a slot.
 */
static inline struct rbtree_node * rbtree_slot_parent(unsigned long slot)
{
    return (struct rbtree_node *)(slot & RBTREE_SLOT_PARENT_MASK);
}

/*
 * Extract the index from a slot.
 */
static inline int rbtree_slot_index(unsigned long slot)
{
    return slot & RBTREE_SLOT_INDEX_MASK;
}

/*
 * Insert a node in a tree, rebalancing it if necessary.
 *
 * The index parameter is the index in the children array of the parent where
 * the new node is to be inserted. It is ignored if the parent is null.
 *
 * This function is intended to be used by the rbtree_insert() macro only.
 */
void rbtree_insert_rebalance(struct rbtree *tree, struct rbtree_node *parent,
                             int index, struct rbtree_node *node);

/*
 * Return the previous or next node relative to a location in a tree.
 *
 * The parent and index parameters define the location, which can be empty.
 * The direction parameter is either RBTREE_LEFT (to obtain the previous
 * node) or RBTREE_RIGHT (to obtain the next one).
 */
struct rbtree_node * rbtree_nearest(struct rbtree_node *parent, int index,
                                    int direction);

/*
 * Return the first or last node of a tree.
 *
 * The direction parameter is either RBTREE_LEFT (to obtain the first node)
 * or RBTREE_RIGHT (to obtain the last one).
 */
struct rbtree_node * rbtree_firstlast(const struct rbtree *tree, int direction);

/*
 * Return the node next to, or previous to the given node.
 *
 * The direction parameter is either RBTREE_LEFT (to obtain the previous node)
 * or RBTREE_RIGHT (to obtain the next one).
 */
struct rbtree_node * rbtree_walk(struct rbtree_node *node, int direction);

/*
 * Return the left-most deepest node of a tree, which is the starting point of
 * the postorder traversal performed by rbtree_for_each_remove().
 */
struct rbtree_node * rbtree_postwalk_deepest(const struct rbtree *tree);

/*
 * Unlink a node from its tree and return the next (right) node in postorder.
 */
struct rbtree_node * rbtree_postwalk_unlink(struct rbtree_node *node);

#endif /* _KERN_RBTREE_I_H */