xref: /third_party/ffmpeg/libavutil/tree.c (revision cabdff1a) 
1/*
2 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
3 *
4 * This file is part of FFmpeg.
5 *
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * FFmpeg 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 GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21#include "error.h"
22#include "log.h"
23#include "mem.h"
24#include "tree.h"
25
26typedef struct AVTreeNode {
27    struct AVTreeNode *child[2];
28    void *elem;
29    int state;
30} AVTreeNode;
31
32const int av_tree_node_size = sizeof(AVTreeNode);
33
34struct AVTreeNode *av_tree_node_alloc(void)
35{
36    return av_mallocz(sizeof(struct AVTreeNode));
37}
38
39void *av_tree_find(const AVTreeNode *t, void *key,
40                   int (*cmp)(const void *key, const void *b), void *next[2])
41{
42    if (t) {
43        unsigned int v = cmp(key, t->elem);
44        if (v) {
45            if (next)
46                next[v >> 31] = t->elem;
47            return av_tree_find(t->child[(v >> 31) ^ 1], key, cmp, next);
48        } else {
49            if (next) {
50                av_tree_find(t->child[0], key, cmp, next);
51                av_tree_find(t->child[1], key, cmp, next);
52            }
53            return t->elem;
54        }
55    }
56    return NULL;
57}
58
59void *av_tree_insert(AVTreeNode **tp, void *key,
60                     int (*cmp)(const void *key, const void *b), AVTreeNode **next)
61{
62    AVTreeNode *t = *tp;
63    if (t) {
64        unsigned int v = cmp(t->elem, key);
65        void *ret;
66        if (!v) {
67            if (*next)
68                return t->elem;
69            else if (t->child[0] || t->child[1]) {
70                int i = !t->child[0];
71                void *next_elem[2];
72                av_tree_find(t->child[i], key, cmp, next_elem);
73                key = t->elem = next_elem[i];
74                v   = -i;
75            } else {
76                *next = t;
77                *tp   = NULL;
78                return NULL;
79            }
80        }
81        ret = av_tree_insert(&t->child[v >> 31], key, cmp, next);
82        if (!ret) {
83            int i              = (v >> 31) ^ !!*next;
84            AVTreeNode **child = &t->child[i];
85            t->state += 2 * i - 1;
86
87            if (!(t->state & 1)) {
88                if (t->state) {
89                    /* The following code is equivalent to
90                     * if ((*child)->state * 2 == -t->state)
91                     *     rotate(child, i ^ 1);
92                     * rotate(tp, i);
93                     *
94                     * with rotate():
95                     * static void rotate(AVTreeNode **tp, int i)
96                     * {
97                     *     AVTreeNode *t= *tp;
98                     *
99                     *     *tp = t->child[i];
100                     *     t->child[i] = t->child[i]->child[i ^ 1];
101                     *     (*tp)->child[i ^ 1] = t;
102                     *     i = 4 * t->state + 2 * (*tp)->state + 12;
103                     *     t->state     = ((0x614586 >> i) & 3) - 1;
104                     *     (*tp)->state = ((0x400EEA >> i) & 3) - 1 +
105                     *                    ((*tp)->state >> 1);
106                     * }
107                     * but such a rotate function is both bigger and slower
108                     */
109                    if ((*child)->state * 2 == -t->state) {
110                        *tp                    = (*child)->child[i ^ 1];
111                        (*child)->child[i ^ 1] = (*tp)->child[i];
112                        (*tp)->child[i]        = *child;
113                        *child                 = (*tp)->child[i ^ 1];
114                        (*tp)->child[i ^ 1]    = t;
115
116                        (*tp)->child[0]->state = -((*tp)->state > 0);
117                        (*tp)->child[1]->state = (*tp)->state < 0;
118                        (*tp)->state           = 0;
119                    } else {
120                        *tp                 = *child;
121                        *child              = (*child)->child[i ^ 1];
122                        (*tp)->child[i ^ 1] = t;
123                        if ((*tp)->state)
124                            t->state = 0;
125                        else
126                            t->state >>= 1;
127                        (*tp)->state = -t->state;
128                    }
129                }
130            }
131            if (!(*tp)->state ^ !!*next)
132                return key;
133        }
134        return ret;
135    } else {
136        *tp   = *next;
137        *next = NULL;
138        if (*tp) {
139            (*tp)->elem = key;
140            return NULL;
141        } else
142            return key;
143    }
144}
145
146void av_tree_destroy(AVTreeNode *t)
147{
148    if (t) {
149        av_tree_destroy(t->child[0]);
150        av_tree_destroy(t->child[1]);
151        av_free(t);
152    }
153}
154
155void av_tree_enumerate(AVTreeNode *t, void *opaque,
156                       int (*cmp)(void *opaque, void *elem),
157                       int (*enu)(void *opaque, void *elem))
158{
159    if (t) {
160        int v = cmp ? cmp(opaque, t->elem) : 0;
161        if (v >= 0)
162            av_tree_enumerate(t->child[0], opaque, cmp, enu);
163        if (v == 0)
164            enu(opaque, t->elem);
165        if (v <= 0)
166            av_tree_enumerate(t->child[1], opaque, cmp, enu);
167    }
168}
169