/*
  * Range coder
  * Copyright (c) 2004 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

  */

 /**

  * @file

  * Range coder.
  * based upon
  *    "Range encoding: an algorithm for removing redundancy from a digitised
  *                     message.
  *     G. N. N. Martin                  Presented in March 1979 to the Video &
  *                                      Data Recording Conference,
  *     IBM UK Scientific Center         held in Southampton July 24-27 1979."
  *
  */
 
 #include <string.h>
 
 #include "avcodec.h"
 #include "rangecoder.h"

 #include "bytestream.h"

 
 
 void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size){

     c->bytestream_start=

     c->bytestream= buf;
     c->bytestream_end= buf + buf_size;
 
     c->low= 0;
     c->range= 0xFF00;
     c->outstanding_count= 0;
     c->outstanding_byte= -1;
 }
 
 void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size){

     /* cast to avoid compiler warning */
     ff_init_range_encoder(c, (uint8_t *) buf, buf_size);

     c->low = bytestream_get_be16(&c->bytestream);

 }
 
 void ff_build_rac_states(RangeCoder *c, int factor, int max_p){
     const int64_t one= 1LL<<32;
     int64_t p;

     int last_p8, p8, i;

 
     memset(c->zero_state, 0, sizeof(c->zero_state));
     memset(c-> one_state, 0, sizeof(c-> one_state));
 
     last_p8= 0;
     p= one/2;
     for(i=0; i<128; i++){
         p8= (256*p + one/2) >> 32; //FIXME try without the one
         if(p8 <= last_p8) p8= last_p8+1;
         if(last_p8 && last_p8<256 && p8<=max_p)
             c->one_state[last_p8]= p8;

         p+= ((one-p)*factor + one/2) >> 32;
         last_p8= p8;
     }

     for(i=256-max_p; i<=max_p; i++){

         if(c->one_state[i])

             continue;
 
         p= (i*one + 128) >> 8;
         p+= ((one-p)*factor + one/2) >> 32;
         p8= (256*p + one/2) >> 32; //FIXME try without the one
         if(p8 <= i) p8= i+1;
         if(p8 > max_p) p8= max_p;
         c->one_state[    i]=     p8;
     }

     for(i=1; i<255; i++)

         c->zero_state[i]= 256-c->one_state[256-i];
 }
 
 /**
  *
  * @return the number of bytes written
  */
 int ff_rac_terminate(RangeCoder *c){
     c->range=0xFF;
     c->low +=0xFF;
     renorm_encoder(c);
     c->range=0xFF;
     renorm_encoder(c);
 
     assert(c->low   == 0);
     assert(c->range >= 0x100);
 
     return c->bytestream - c->bytestream_start;
 }
 

 #ifdef TEST

 #define SIZE 10240

 
 #include "libavutil/lfg.h"
 

 int main(void){

     RangeCoder c;
     uint8_t b[9*SIZE];
     uint8_t r[9*SIZE];
     int i;
     uint8_t state[10]= {0};

     AVLFG prng;

     av_lfg_init(&prng, 1);

     ff_init_range_encoder(&c, b, SIZE);
     ff_build_rac_states(&c, 0.05*(1LL<<32), 128+64+32+16);

     memset(state, 128, sizeof(state));
 
     for(i=0; i<SIZE; i++){

         r[i] = av_lfg_get(&prng) % 7;

     }

     for(i=0; i<SIZE; i++){
 START_TIMER
         put_rac(&c, state, r[i]&1);
 STOP_TIMER("put_rac")
     }
 

     ff_rac_terminate(&c);

     ff_init_range_decoder(&c, b, SIZE);

     memset(state, 128, sizeof(state));

     for(i=0; i<SIZE; i++){
 START_TIMER
         if( (r[i]&1) != get_rac(&c, state) )
             av_log(NULL, AV_LOG_DEBUG, "rac failure at %d\n", i);
 STOP_TIMER("get_rac")
     }

     return 0;
 }

 #endif /* TEST */