git.sesse.net Git - ffmpeg/blob - libavutil/tree.c

   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
  26 typedef struct AVTreeNode {
  27     struct AVTreeNode *child[2];
  28     void *elem;
  29     int state;
  30 } AVTreeNode;
  31
  32 const int av_tree_node_size = sizeof(AVTreeNode);
  33
  34 struct AVTreeNode *av_tree_node_alloc(void)
  35 {
  36     return av_mallocz(sizeof(struct AVTreeNode));
  37 }
  38
  39 void *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
  59 void *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
 146 void 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
 155 void 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 }