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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 rangecoder.h
* Range coder.
*/
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;
assert(*state);
assert(range1 < c->range);
assert(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
}
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