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/*
* exp golomb vlc stuff
* Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
* Copyright (c) 2004 Alex Beregszaszi
*
* This library 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 of the License, or (at your option) any later version.
*
* This library 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 this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <limits.h>
/* From libavutil/common.h */
extern const uint8_t ff_log2_tab[256];
static inline int av_log2(unsigned int v)
{
int n;
n = 0;
if (v & 0xffff0000) {
v >>= 16;
n += 16;
}
if (v & 0xff00) {
v >>= 8;
n += 8;
}
n += ff_log2_tab[v];
return n;
}
/**
* @file golomb.h
* @brief
* exp golomb vlc stuff
* @author Michael Niedermayer <michaelni@gmx.at> and Alex Beregszaszi
*/
/**
* read unsigned golomb rice code (jpegls).
*/
static inline int get_ur_golomb_jpegls(GetBitContext *gb, int k, int limit, int esc_len){
unsigned int buf;
int log;
OPEN_READER(re, gb);
UPDATE_CACHE(re, gb);
buf=GET_CACHE(re, gb);
log= av_log2(buf);
if(log > 31-11){
buf >>= log - k;
buf += (30-log)<<k;
LAST_SKIP_BITS(re, gb, 32 + k - log);
CLOSE_READER(re, gb);
return buf;
}else{
int i;
for(i=0; SHOW_UBITS(re, gb, 1) == 0; i++){
LAST_SKIP_BITS(re, gb, 1);
UPDATE_CACHE(re, gb);
}
SKIP_BITS(re, gb, 1);
if(i < limit - 1){
if(k){
buf = SHOW_UBITS(re, gb, k);
LAST_SKIP_BITS(re, gb, k);
}else{
buf=0;
}
CLOSE_READER(re, gb);
return buf + (i<<k);
}else if(i == limit - 1){
buf = SHOW_UBITS(re, gb, esc_len);
LAST_SKIP_BITS(re, gb, esc_len);
CLOSE_READER(re, gb);
return buf + 1;
}else
return -1;
}
}
/**
* read signed golomb rice code (flac).
*/
static inline int get_sr_golomb_flac(GetBitContext *gb, int k, int limit, int esc_len){
int v= get_ur_golomb_jpegls(gb, k, limit, esc_len);
return (v>>1) ^ -(v&1);
}
/**
* read unsigned golomb rice code (shorten).
*/
#define get_ur_golomb_shorten(gb, k) get_ur_golomb_jpegls(gb, k, INT_MAX, 0)
/*
static inline unsigned int get_ur_golomb_shorten(GetBitContext *gb, int k){
return get_ur_golomb_jpegls(gb, k, INT_MAX, 0);
}
*/
/**
* read signed golomb rice code (shorten).
*/
static inline int get_sr_golomb_shorten(GetBitContext* gb, int k)
{
int uvar = get_ur_golomb_jpegls(gb, k + 1, INT_MAX, 0);
if (uvar & 1)
return ~(uvar >> 1);
else
return uvar >> 1;
}
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