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/*
* 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;
int overread;
#define MAX_OVERREAD 2
} 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);
/**
* Terminates the range coder
* @param version version 0 requires the decoder to know the data size in bytes
* version 1 needs about 1 bit more space but does not need to
* carry the size from encoder to decoder
*/
int ff_rac_terminate(RangeCoder *c, int version);
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++;
} else
c->overread ++;
}
}
static inline int get_rac(RangeCoder *c, uint8_t *const state)
{
int range1 = (c->range * (*state)) >> 8;
c->range -= range1;
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;
}
}
#endif /* AVCODEC_RANGECODER_H */
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