/**

  * @file

  * huffman tree builder and VLC generator
  * Copyright (c) 2006 Konstantin Shishkov
  *
  * 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 "avcodec.h"

 #include "get_bits.h"

 #include "huffman.h"
 
 /* symbol for Huffman tree node */
 #define HNODE -1
 
 

 static void get_tree_codes(uint32_t *bits, int16_t *lens, uint8_t *xlat, Node *nodes, int node, uint32_t pfx, int pl, int *pos, int no_zero_count)

 {
     int s;
 
     s = nodes[node].sym;

     if(s != HNODE || (no_zero_count && !nodes[node].count)){

         bits[*pos] = pfx;
         lens[*pos] = pl;
         xlat[*pos] = s;
         (*pos)++;
     }else{
         pfx <<= 1;
         pl++;

         get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0, pfx, pl, pos,
                        no_zero_count);

         pfx |= 1;

         get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0+1, pfx, pl, pos,
                        no_zero_count);

     }
 }
 

 static int build_huff_tree(VLC *vlc, Node *nodes, int head, int flags)

 {

     int no_zero_count = !(flags & FF_HUFFMAN_FLAG_ZERO_COUNT);

     uint32_t bits[256];
     int16_t lens[256];
     uint8_t xlat[256];
     int pos = 0;
 

     get_tree_codes(bits, lens, xlat, nodes, head, 0, 0, &pos, no_zero_count);

     return init_vlc_sparse(vlc, 9, pos, lens, 2, 2, bits, 4, 4, xlat, 1, 1, 0);
 }
 
 
 /**

  * nodes size must be 2*nb_codes

  * first nb_codes nodes.count must be set
  */
 int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int nb_codes,

                        Node *nodes, HuffCmp cmp, int flags)

 {
     int i, j;
     int cur_node;
     int64_t sum = 0;
 
     for(i = 0; i < nb_codes; i++){
         nodes[i].sym = i;
         nodes[i].n0 = -2;
         sum += nodes[i].count;
     }
 
     if(sum >> 31) {
         av_log(avctx, AV_LOG_ERROR, "Too high symbol frequencies. Tree construction is not possible\n");
         return -1;
     }
     qsort(nodes, nb_codes, sizeof(Node), cmp);
     cur_node = nb_codes;

     nodes[nb_codes*2-1].count = 0;

     for(i = 0; i < nb_codes*2-1; i += 2){
         nodes[cur_node].sym = HNODE;
         nodes[cur_node].count = nodes[i].count + nodes[i+1].count;
         nodes[cur_node].n0 = i;
         for(j = cur_node; j > 0; j--){
             if(nodes[j].count > nodes[j-1].count ||
                (nodes[j].count == nodes[j-1].count &&

                 (!(flags & FF_HUFFMAN_FLAG_HNODE_FIRST) ||
                  nodes[j].n0==j-1 || nodes[j].n0==j-2 ||

                  (nodes[j].sym!=HNODE && nodes[j-1].sym!=HNODE))))
                 break;
             FFSWAP(Node, nodes[j], nodes[j-1]);
         }
         cur_node++;
     }

     if(build_huff_tree(vlc, nodes, nb_codes*2-2, flags) < 0){

         av_log(avctx, AV_LOG_ERROR, "Error building tree\n");
         return -1;
     }
     return 0;
 }