/*
  * 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 "libavutil/attributes.h"

 #include "libavutil/avassert.h"

 #include "libavutil/intreadwrite.h"
 

 #include "avcodec.h"
 #include "rangecoder.h"
 

 av_cold 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;

 }
 

 av_cold 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         = AV_RB16(c->bytestream);

     c->bytestream += 2;

     c->overread    = 0;

     if (c->low >= 0xFF00) {
         c->low = 0xFF00;

         c->bytestream_end = 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);
 

     av_assert1(c->low   == 0);
     av_assert1(c->range >= 0x100);

 
     return c->bytestream - c->bytestream_start;
 }