/*
  * 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.
  */
 

 #ifndef AVCODEC_RANGECODER_H
 #define AVCODEC_RANGECODER_H

 #include <stdint.h>

 #include "libavutil/common.h"

 #include "libavutil/avassert.h"

 typedef struct RangeCoder {

     int low;
     int range;
     int outstanding_count;
     int outstanding_byte;
     uint8_t zero_state[256];

     uint8_t one_state[256];

     uint8_t *bytestream_start;
     uint8_t *bytestream;
     uint8_t *bytestream_end;

 } RangeCoder;

 
 void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size);
 void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size);
 int ff_rac_terminate(RangeCoder *c);
 void ff_build_rac_states(RangeCoder *c, int factor, int max_p);
 

 static inline void renorm_encoder(RangeCoder *c)
 {
     // FIXME: optimize
     while (c->range < 0x100) {
         if (c->outstanding_byte < 0) {
             c->outstanding_byte = c->low >> 8;
         } else if (c->low <= 0xFF00) {

             *c->bytestream++ = c->outstanding_byte;

             for (; c->outstanding_count; c->outstanding_count--)

                 *c->bytestream++ = 0xFF;

             c->outstanding_byte = c->low >> 8;
         } else if (c->low >= 0x10000) {

             *c->bytestream++ = c->outstanding_byte + 1;

             for (; c->outstanding_count; c->outstanding_count--)

                 *c->bytestream++ = 0x00;

             c->outstanding_byte = (c->low >> 8) & 0xFF;
         } else {

             c->outstanding_count++;
         }

         c->low     = (c->low & 0xFF) << 8;

         c->range <<= 8;
     }
 }
 

 static inline int get_rac_count(RangeCoder *c)
 {
     int x = c->bytestream - c->bytestream_start + c->outstanding_count;
     if (c->outstanding_byte >= 0)

         x++;

     return 8 * x - av_log2(c->range);

 }
 

 static inline void put_rac(RangeCoder *c, uint8_t *const state, int bit)
 {
     int range1 = (c->range * (*state)) >> 8;

     av_assert2(*state);
     av_assert2(range1 < c->range);
     av_assert2(range1 > 0);

     if (!bit) {

         c->range -= range1;

         *state    = c->zero_state[*state];
     } else {
         c->low  += c->range - range1;

         c->range = range1;

         *state   = c->one_state[*state];

     }

     renorm_encoder(c);
 }
 

 static inline void refill(RangeCoder *c)
 {
     if (c->range < 0x100) {

         c->range <<= 8;

         c->low   <<= 8;
         if (c->bytestream < c->bytestream_end)
             c->low += c->bytestream[0];

         c->bytestream++;
     }
 }
 

 static inline int get_rac(RangeCoder *c, uint8_t *const state)
 {
     int range1 = (c->range * (*state)) >> 8;

     int av_unused one_mask;

     c->range -= range1;
 #if 1

     if (c->low < c->range) {
         *state = c->zero_state[*state];

         refill(c);
         return 0;

     } else {
         c->low  -= c->range;
         *state   = c->one_state[*state];

         c->range = range1;
         refill(c);
         return 1;
     }
 #else

     one_mask = (c->range - c->low - 1) >> 31;

     c->low   -= c->range & one_mask;

     c->range += (range1 - c->range) & one_mask;

     *state = c->zero_state[(*state) + (256 & one_mask)];

     refill(c);
 

     return one_mask & 1;

 #endif
 }
 

 #endif /* AVCODEC_RANGECODER_H */