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 Libav.
   5  *
   6  * Libav 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  * Libav 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 Libav; 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 "mem.h"
  23 #include "tree.h"
  24
  25 typedef struct AVTreeNode {
  26     struct AVTreeNode *child[2];
  27     void *elem;
  28     int state;
  29 } AVTreeNode;
  30
  31 struct AVTreeNode *av_tree_node_alloc(void)
  32 {
  33     return av_mallocz(sizeof(struct AVTreeNode));
  34 }
  35
  36 void *av_tree_find(const AVTreeNode *t, void *key,
  37                    int (*cmp)(void *key, const void *b), void *next[2])
  38 {
  39     if (t) {
  40         unsigned int v = cmp(key, t->elem);
  41         if (v) {
  42             if (next)
  43                 next[v >> 31] = t->elem;
  44             return av_tree_find(t->child[(v >> 31) ^ 1], key, cmp, next);
  45         } else {
  46             if (next) {
  47                 av_tree_find(t->child[0], key, cmp, next);
  48                 av_tree_find(t->child[1], key, cmp, next);
  49             }
  50             return t->elem;
  51         }
  52     }
  53     return NULL;
  54 }
  55
  56 void *av_tree_insert(AVTreeNode **tp, void *key,
  57                      int (*cmp)(void *key, const void *b), AVTreeNode **next)
  58 {
  59     AVTreeNode *t = *tp;
  60     if (t) {
  61         unsigned int v = cmp(t->elem, key);
  62         void *ret;
  63         if (!v) {
  64             if (*next)
  65                 return t->elem;
  66             else if (t->child[0] || t->child[1]) {
  67                 int i = !t->child[0];
  68                 void *next_elem[2];
  69                 av_tree_find(t->child[i], key, cmp, next_elem);
  70                 key = t->elem = next_elem[i];
  71                 v   = -i;
  72             } else {
  73                 *next = t;
  74                 *tp   = NULL;
  75                 return NULL;
  76             }
  77         }
  78         ret = av_tree_insert(&t->child[v >> 31], key, cmp, next);
  79         if (!ret) {
  80             int i              = (v >> 31) ^ !!*next;
  81             AVTreeNode **child = &t->child[i];
  82             t->state += 2 * i - 1;
  83
  84             if (!(t->state & 1)) {
  85                 if (t->state) {
  86                     /* The following code is equivalent to
  87                      * if ((*child)->state * 2 == -t->state)
  88                      *     rotate(child, i ^ 1);
  89                      * rotate(tp, i);
  90                      *
  91                      * with rotate():
  92                      * static void rotate(AVTreeNode **tp, int i)
  93                      * {
  94                      *     AVTreeNode *t= *tp;
  95                      *
  96                      *     *tp = t->child[i];
  97                      *     t->child[i] = t->child[i]->child[i ^ 1];
  98                      *     (*tp)->child[i ^ 1] = t;
  99                      *     i = 4 * t->state + 2 * (*tp)->state + 12;
 100                      *     t->state     = ((0x614586 >> i) & 3) - 1;
 101                      *     (*tp)->state = ((0x400EEA >> i) & 3) - 1 +
 102                      *                    ((*tp)->state >> 1);
 103                      * }
 104                      * but such a rotate function is both bigger and slower
 105                      */
 106                     if ((*child)->state * 2 == -t->state) {
 107                         *tp                    = (*child)->child[i ^ 1];
 108                         (*child)->child[i ^ 1] = (*tp)->child[i];
 109                         (*tp)->child[i]        = *child;
 110                         *child                 = (*tp)->child[i ^ 1];
 111                         (*tp)->child[i ^ 1]    = t;
 112
 113                         (*tp)->child[0]->state = -((*tp)->state > 0);
 114                         (*tp)->child[1]->state = (*tp)->state < 0;
 115                         (*tp)->state           = 0;
 116                     } else {
 117                         *tp                 = *child;
 118                         *child              = (*child)->child[i ^ 1];
 119                         (*tp)->child[i ^ 1] = t;
 120                         if ((*tp)->state)
 121                             t->state = 0;
 122                         else
 123                             t->state >>= 1;
 124                         (*tp)->state = -t->state;
 125                     }
 126                 }
 127             }
 128             if (!(*tp)->state ^ !!*next)
 129                 return key;
 130         }
 131         return ret;
 132     } else {
 133         *tp   = *next;
 134         *next = NULL;
 135         if (*tp) {
 136             (*tp)->elem = key;
 137             return NULL;
 138         } else
 139             return key;
 140     }
 141 }
 142
 143 void av_tree_destroy(AVTreeNode *t)
 144 {
 145     if (t) {
 146         av_tree_destroy(t->child[0]);
 147         av_tree_destroy(t->child[1]);
 148         av_free(t);
 149     }
 150 }
 151
 152 void av_tree_enumerate(AVTreeNode *t, void *opaque,
 153                        int (*cmp)(void *opaque, void *elem),
 154                        int (*enu)(void *opaque, void *elem))
 155 {
 156     if (t) {
 157         int v = cmp ? cmp(opaque, t->elem) : 0;
 158         if (v >= 0)
 159             av_tree_enumerate(t->child[0], opaque, cmp, enu);
 160         if (v == 0)
 161             enu(opaque, t->elem);
 162         if (v <= 0)
 163             av_tree_enumerate(t->child[1], opaque, cmp, enu);
 164     }
 165 }