FFmpeg/libavutil/tree.c

/*
 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "common.h"
#include "log.h"
#include "tree.h"

typedef struct AVTreeNode{
    struct AVTreeNode *child[2];
    void *elem;
    int state;
}AVTreeNode;

const int av_tree_node_size = sizeof(AVTreeNode);

void *av_tree_find(const AVTreeNode *t, void *key, int (*cmp)(void *key, const void *b), void *next[2]){
    if(t){
        unsigned int v= cmp(key, t->elem);
        if(v){
            if(next) next[v>>31]= t->elem;
            return av_tree_find(t->child[(v>>31)^1], key, cmp, next);
        }else{
            if(next){
                av_tree_find(t->child[0], key, cmp, next);
                av_tree_find(t->child[1], key, cmp, next);
            }
            return t->elem;
        }
    }
    return NULL;
}

void *av_tree_insert(AVTreeNode **tp, void *key, int (*cmp)(void *key, const void *b), AVTreeNode **next){
    AVTreeNode *t= *tp;
    if(t){
        unsigned int v= cmp(t->elem, key);
        void *ret;
        if(!v){
            if(*next)
                return t->elem;
            else if(t->child[0]||t->child[1]){
                int i= !t->child[0];
                void *next_elem[2];
                av_tree_find(t->child[i], key, cmp, next_elem);
                key= t->elem= next_elem[i];
                v= -i;
            }else{
                *next= t;
                *tp=NULL;
                return NULL;
            }
        }
        ret= av_tree_insert(&t->child[v>>31], key, cmp, next);
        if(!ret){
            int i= (v>>31) ^ !!*next;
            AVTreeNode **child= &t->child[i];
            t->state += 2*i - 1;

            if(!(t->state&1)){
                if(t->state){
                    /* The following code is equivalent to
                    if((*child)->state*2 == -t->state)
                        rotate(child, i^1);
                    rotate(tp, i);

                    with rotate():
                    static void rotate(AVTreeNode **tp, int i){
                        AVTreeNode *t= *tp;

                        *tp= t->child[i];
                        t->child[i]= t->child[i]->child[i^1];
                        (*tp)->child[i^1]= t;
                        i= 4*t->state + 2*(*tp)->state + 12;
                          t  ->state=                     ((0x614586 >> i) & 3)-1;
                        (*tp)->state= ((*tp)->state>>1) + ((0x400EEA >> i) & 3)-1;
                    }
                    but such a rotate function is both bigger and slower
                    */
                    if((*child)->state*2 == -t->state){
                        *tp= (*child)->child[i^1];
                        (*child)->child[i^1]= (*tp)->child[i];
                        (*tp)->child[i]= *child;
                        *child= (*tp)->child[i^1];
                        (*tp)->child[i^1]= t;

                        (*tp)->child[0]->state= -((*tp)->state>0);
                        (*tp)->child[1]->state=   (*tp)->state<0 ;
                        (*tp)->state=0;
                    }else{
                        *tp= *child;
                        *child= (*child)->child[i^1];
                        (*tp)->child[i^1]= t;
                        if((*tp)->state) t->state  = 0;
                        else             t->state>>= 1;
                        (*tp)->state= -t->state;
                    }
                }
            }
            if(!(*tp)->state ^ !!*next)
                return key;
        }
        return ret;
    }else{
        *tp= *next; *next= NULL;
        if(*tp){
            (*tp)->elem= key;
            return NULL;
        }else
            return key;
    }
}

void av_tree_destroy(AVTreeNode *t){
    if(t){
        av_tree_destroy(t->child[0]);
        av_tree_destroy(t->child[1]);
        av_free(t);
    }
}

#if 0
void av_tree_enumerate(AVTreeNode *t, void *opaque, int (*f)(void *opaque, void *elem)){
    int v= f(opaque, t->elem);
    if(v>=0) av_tree_enumerate(t->child[0], opaque, f);
    if(v<=0) av_tree_enumerate(t->child[1], opaque, f);
}
#endif

#ifdef TEST

#include "lfg.h"

static int check(AVTreeNode *t){
    if(t){
        int left= check(t->child[0]);
        int right= check(t->child[1]);

        if(left>999 || right>999)
            return 1000;
        if(right - left != t->state)
            return 1000;
        if(t->state>1 || t->state<-1)
            return 1000;
        return FFMAX(left, right)+1;
    }
    return 0;
}

static void print(AVTreeNode *t, int depth){
    int i;
    for(i=0; i<depth*4; i++) av_log(NULL, AV_LOG_ERROR, " ");
    if(t){
        av_log(NULL, AV_LOG_ERROR, "Node %p %2d %p\n", t, t->state, t->elem);
        print(t->child[0], depth+1);
        print(t->child[1], depth+1);
    }else
        av_log(NULL, AV_LOG_ERROR, "NULL\n");
}

static int cmp(void *a, const void *b){
    return (uint8_t*)a-(const uint8_t*)b;
}

int main(void){
    int i;
    void *k;
    AVTreeNode *root= NULL, *node=NULL;
    AVLFG prng;

    av_lfg_init(&prng, 1);

    for(i=0; i<10000; i++){
        int j = av_lfg_get(&prng) % 86294;
        if(check(root) > 999){
            av_log(NULL, AV_LOG_ERROR, "FATAL error %d\n", i);
        print(root, 0);
            return -1;
        }
        av_log(NULL, AV_LOG_ERROR, "inserting %4d\n", j);
        if(!node)
            node= av_mallocz(av_tree_node_size);
        av_tree_insert(&root, (void*)(j+1), cmp, &node);

        j = av_lfg_get(&prng) % 86294;
        {
            AVTreeNode *node2=NULL;
            av_log(NULL, AV_LOG_ERROR, "removing %4d\n", j);
            av_tree_insert(&root, (void*)(j+1), cmp, &node2);
            k= av_tree_find(root, (void*)(j+1), cmp, NULL);
            if(k)
                av_log(NULL, AV_LOG_ERROR, "removal failure %d\n", i);
        }
    }
    return 0;
}
#endif