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ffmpeg/libavcodec/get_bits.h

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/*
* 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
* bitstream reader API header.
*/
#ifndef AVCODEC_GET_BITS_H
#define AVCODEC_GET_BITS_H
#include <stdint.h>
#include <stdlib.h>
#include <assert.h>
#include "libavutil/bswap.h"
#include "libavutil/common.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/log.h"
#include "mathops.h"
#if defined(ALT_BITSTREAM_READER_LE) && !defined(ALT_BITSTREAM_READER)
# define ALT_BITSTREAM_READER
#endif
#if !defined(LIBMPEG2_BITSTREAM_READER) && !defined(A32_BITSTREAM_READER) && !defined(ALT_BITSTREAM_READER)
# if ARCH_ARM && !HAVE_FAST_UNALIGNED
# define A32_BITSTREAM_READER
# else
# define ALT_BITSTREAM_READER
//#define LIBMPEG2_BITSTREAM_READER
//#define A32_BITSTREAM_READER
# endif
#endif
/* bit input */
/* buffer, buffer_end and size_in_bits must be present and used by every reader */
typedef struct GetBitContext {
const uint8_t *buffer, *buffer_end;
#ifdef ALT_BITSTREAM_READER
int index;
#elif defined LIBMPEG2_BITSTREAM_READER
uint8_t *buffer_ptr;
uint32_t cache;
int bit_count;
#elif defined A32_BITSTREAM_READER
uint32_t *buffer_ptr;
uint32_t cache0;
uint32_t cache1;
int bit_count;
#endif
int size_in_bits;
} GetBitContext;
#define VLC_TYPE int16_t
typedef struct VLC {
int bits;
VLC_TYPE (*table)[2]; ///< code, bits
int table_size, table_allocated;
} VLC;
typedef struct RL_VLC_ELEM {
int16_t level;
int8_t len;
uint8_t run;
} RL_VLC_ELEM;
/* Bitstream reader API docs:
name
arbitrary name which is used as prefix for the internal variables
gb
getbitcontext
OPEN_READER(name, gb)
loads gb into local variables
CLOSE_READER(name, gb)
stores local vars in gb
UPDATE_CACHE(name, gb)
refills the internal cache from the bitstream
after this call at least MIN_CACHE_BITS will be available,
GET_CACHE(name, gb)
will output the contents of the internal cache, next bit is MSB of 32 or 64 bit (FIXME 64bit)
SHOW_UBITS(name, gb, num)
will return the next num bits
SHOW_SBITS(name, gb, num)
will return the next num bits and do sign extension
SKIP_BITS(name, gb, num)
will skip over the next num bits
note, this is equivalent to SKIP_CACHE; SKIP_COUNTER
SKIP_CACHE(name, gb, num)
will remove the next num bits from the cache (note SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER)
SKIP_COUNTER(name, gb, num)
will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS)
LAST_SKIP_CACHE(name, gb, num)
will remove the next num bits from the cache if it is needed for UPDATE_CACHE otherwise it will do nothing
LAST_SKIP_BITS(name, gb, num)
is equivalent to LAST_SKIP_CACHE; SKIP_COUNTER
for examples see get_bits, show_bits, skip_bits, get_vlc
*/
#ifdef ALT_BITSTREAM_READER
# define MIN_CACHE_BITS 25
# define OPEN_READER(name, gb)\
unsigned int name##_index= (gb)->index;\
int name##_cache= 0;\
# define CLOSE_READER(name, gb)\
(gb)->index= name##_index;\
# ifdef ALT_BITSTREAM_READER_LE
# define UPDATE_CACHE(name, gb)\
name##_cache= AV_RL32( ((const uint8_t *)(gb)->buffer)+(name##_index>>3) ) >> (name##_index&0x07);\
# define SKIP_CACHE(name, gb, num)\
name##_cache >>= (num);
# else
# define UPDATE_CACHE(name, gb)\
name##_cache= AV_RB32( ((const uint8_t *)(gb)->buffer)+(name##_index>>3) ) << (name##_index&0x07);\
# define SKIP_CACHE(name, gb, num)\
name##_cache <<= (num);
# endif
// FIXME name?
# define SKIP_COUNTER(name, gb, num)\
name##_index += (num);\
# define SKIP_BITS(name, gb, num)\
{\
SKIP_CACHE(name, gb, num)\
SKIP_COUNTER(name, gb, num)\
}\
# define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
# define LAST_SKIP_CACHE(name, gb, num) ;
# ifdef ALT_BITSTREAM_READER_LE
# define SHOW_UBITS(name, gb, num)\
zero_extend(name##_cache, num)
# define SHOW_SBITS(name, gb, num)\
sign_extend(name##_cache, num)
# else
# define SHOW_UBITS(name, gb, num)\
NEG_USR32(name##_cache, num)
# define SHOW_SBITS(name, gb, num)\
NEG_SSR32(name##_cache, num)
# endif
# define GET_CACHE(name, gb)\
((uint32_t)name##_cache)
static inline int get_bits_count(const GetBitContext *s){
return s->index;
}
static inline void skip_bits_long(GetBitContext *s, int n){
s->index += n;
}
#elif defined LIBMPEG2_BITSTREAM_READER
//libmpeg2 like reader
# define MIN_CACHE_BITS 17
# define OPEN_READER(name, gb)\
int name##_bit_count=(gb)->bit_count;\
int name##_cache= (gb)->cache;\
uint8_t * name##_buffer_ptr=(gb)->buffer_ptr;\
# define CLOSE_READER(name, gb)\
(gb)->bit_count= name##_bit_count;\
(gb)->cache= name##_cache;\
(gb)->buffer_ptr= name##_buffer_ptr;\
# define UPDATE_CACHE(name, gb)\
if(name##_bit_count >= 0){\
name##_cache+= AV_RB16(name##_buffer_ptr) << name##_bit_count; \
name##_buffer_ptr+=2;\
name##_bit_count-= 16;\
}\
# define SKIP_CACHE(name, gb, num)\
name##_cache <<= (num);\
# define SKIP_COUNTER(name, gb, num)\
name##_bit_count += (num);\
# define SKIP_BITS(name, gb, num)\
{\
SKIP_CACHE(name, gb, num)\
SKIP_COUNTER(name, gb, num)\
}\
# define LAST_SKIP_BITS(name, gb, num) SKIP_BITS(name, gb, num)
# define LAST_SKIP_CACHE(name, gb, num) SKIP_CACHE(name, gb, num)
# define SHOW_UBITS(name, gb, num)\
NEG_USR32(name##_cache, num)
# define SHOW_SBITS(name, gb, num)\
NEG_SSR32(name##_cache, num)
# define GET_CACHE(name, gb)\
((uint32_t)name##_cache)
static inline int get_bits_count(const GetBitContext *s){
return (s->buffer_ptr - s->buffer)*8 - 16 + s->bit_count;
}
static inline void skip_bits_long(GetBitContext *s, int n){
OPEN_READER(re, s)
re_bit_count += n;
re_buffer_ptr += 2*(re_bit_count>>4);
re_bit_count &= 15;
re_cache = ((re_buffer_ptr[-2]<<8) + re_buffer_ptr[-1]) << (16+re_bit_count);
UPDATE_CACHE(re, s)
CLOSE_READER(re, s)
}
#elif defined A32_BITSTREAM_READER
# define MIN_CACHE_BITS 32
# define OPEN_READER(name, gb)\
int name##_bit_count=(gb)->bit_count;\
uint32_t name##_cache0= (gb)->cache0;\
uint32_t name##_cache1= (gb)->cache1;\
uint32_t * name##_buffer_ptr=(gb)->buffer_ptr;\
# define CLOSE_READER(name, gb)\
(gb)->bit_count= name##_bit_count;\
(gb)->cache0= name##_cache0;\
(gb)->cache1= name##_cache1;\
(gb)->buffer_ptr= name##_buffer_ptr;\
# define UPDATE_CACHE(name, gb)\
if(name##_bit_count > 0){\
const uint32_t next= av_be2ne32( *name##_buffer_ptr );\
name##_cache0 |= NEG_USR32(next,name##_bit_count);\
name##_cache1 |= next<<name##_bit_count;\
name##_buffer_ptr++;\
name##_bit_count-= 32;\
}\
#if ARCH_X86
# define SKIP_CACHE(name, gb, num)\
__asm__(\
"shldl %2, %1, %0 \n\t"\
"shll %2, %1 \n\t"\
: "+r" (name##_cache0), "+r" (name##_cache1)\
: "Ic" ((uint8_t)(num))\
);
#else
# define SKIP_CACHE(name, gb, num)\
name##_cache0 <<= (num);\
name##_cache0 |= NEG_USR32(name##_cache1,num);\
name##_cache1 <<= (num);
#endif
# define SKIP_COUNTER(name, gb, num)\
name##_bit_count += (num);\
# define SKIP_BITS(name, gb, num)\
{\
SKIP_CACHE(name, gb, num)\
SKIP_COUNTER(name, gb, num)\
}\
# define LAST_SKIP_BITS(name, gb, num) SKIP_BITS(name, gb, num)
# define LAST_SKIP_CACHE(name, gb, num) SKIP_CACHE(name, gb, num)
# define SHOW_UBITS(name, gb, num)\
NEG_USR32(name##_cache0, num)
# define SHOW_SBITS(name, gb, num)\
NEG_SSR32(name##_cache0, num)
# define GET_CACHE(name, gb)\
(name##_cache0)
static inline int get_bits_count(const GetBitContext *s){
return ((uint8_t*)s->buffer_ptr - s->buffer)*8 - 32 + s->bit_count;
}
static inline void skip_bits_long(GetBitContext *s, int n){
OPEN_READER(re, s)
re_bit_count += n;
re_buffer_ptr += re_bit_count>>5;
re_bit_count &= 31;
re_cache0 = av_be2ne32( re_buffer_ptr[-1] ) << re_bit_count;
re_cache1 = 0;
UPDATE_CACHE(re, s)
CLOSE_READER(re, s)
}
#endif
/**
* read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
* if MSB not set it is negative
* @param n length in bits
* @author BERO
*/
static inline int get_xbits(GetBitContext *s, int n){
register int sign;
register int32_t cache;
OPEN_READER(re, s)
UPDATE_CACHE(re, s)
cache = GET_CACHE(re,s);
sign=(~cache)>>31;
LAST_SKIP_BITS(re, s, n)
CLOSE_READER(re, s)
return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
}
static inline int get_sbits(GetBitContext *s, int n){
register int tmp;
OPEN_READER(re, s)
UPDATE_CACHE(re, s)
tmp= SHOW_SBITS(re, s, n);
LAST_SKIP_BITS(re, s, n)
CLOSE_READER(re, s)
return tmp;
}
/**
* reads 1-17 bits.
* Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
*/
static inline unsigned int get_bits(GetBitContext *s, int n){
register int tmp;
OPEN_READER(re, s)
UPDATE_CACHE(re, s)
tmp= SHOW_UBITS(re, s, n);
LAST_SKIP_BITS(re, s, n)
CLOSE_READER(re, s)
return tmp;
}
/**
* shows 1-17 bits.
* Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
*/
static inline unsigned int show_bits(GetBitContext *s, int n){
register int tmp;
OPEN_READER(re, s)
UPDATE_CACHE(re, s)
tmp= SHOW_UBITS(re, s, n);
// CLOSE_READER(re, s)
return tmp;
}
static inline void skip_bits(GetBitContext *s, int n){
//Note gcc seems to optimize this to s->index+=n for the ALT_READER :))
OPEN_READER(re, s)
UPDATE_CACHE(re, s)
LAST_SKIP_BITS(re, s, n)
CLOSE_READER(re, s)
}
static inline unsigned int get_bits1(GetBitContext *s){
#ifdef ALT_BITSTREAM_READER
unsigned int index= s->index;
uint8_t result= s->buffer[ index>>3 ];
#ifdef ALT_BITSTREAM_READER_LE
result>>= (index&0x07);
result&= 1;
#else
result<<= (index&0x07);
result>>= 8 - 1;
#endif
index++;
s->index= index;
return result;
#else
return get_bits(s, 1);
#endif
}
static inline unsigned int show_bits1(GetBitContext *s){
return show_bits(s, 1);
}
static inline void skip_bits1(GetBitContext *s){
skip_bits(s, 1);
}
/**
* reads 0-32 bits.
*/
static inline unsigned int get_bits_long(GetBitContext *s, int n){
if(n<=MIN_CACHE_BITS) return get_bits(s, n);
else{
#ifdef ALT_BITSTREAM_READER_LE
int ret= get_bits(s, 16);
return ret | (get_bits(s, n-16) << 16);
#else
int ret= get_bits(s, 16) << (n-16);
return ret | get_bits(s, n-16);
#endif
}
}
/**
* reads 0-32 bits as a signed integer.
*/
static inline int get_sbits_long(GetBitContext *s, int n) {
return sign_extend(get_bits_long(s, n), n);
}
/**
* shows 0-32 bits.
*/
static inline unsigned int show_bits_long(GetBitContext *s, int n){
if(n<=MIN_CACHE_BITS) return show_bits(s, n);
else{
GetBitContext gb= *s;
return get_bits_long(&gb, n);
}
}
static inline int check_marker(GetBitContext *s, const char *msg)
{
int bit= get_bits1(s);
if(!bit)
av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
return bit;
}
/**
* init GetBitContext.
* @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
* because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
* @param bit_size the size of the buffer in bits
*
* While GetBitContext stores the buffer size, for performance reasons you are
* responsible for checking for the buffer end yourself (take advantage of the padding)!
*/
static inline void init_get_bits(GetBitContext *s,
const uint8_t *buffer, int bit_size)
{
int buffer_size= (bit_size+7)>>3;
if(buffer_size < 0 || bit_size < 0) {
buffer_size = bit_size = 0;
buffer = NULL;
}
s->buffer= buffer;
s->size_in_bits= bit_size;
s->buffer_end= buffer + buffer_size;
#ifdef ALT_BITSTREAM_READER
s->index=0;
#elif defined LIBMPEG2_BITSTREAM_READER
s->buffer_ptr = (uint8_t*)((intptr_t)buffer&(~1));
s->bit_count = 16 + 8*((intptr_t)buffer&1);
skip_bits_long(s, 0);
#elif defined A32_BITSTREAM_READER
s->buffer_ptr = (uint32_t*)((intptr_t)buffer&(~3));
s->bit_count = 32 + 8*((intptr_t)buffer&3);
skip_bits_long(s, 0);
#endif
}
static inline void align_get_bits(GetBitContext *s)
{
int n= (-get_bits_count(s)) & 7;
if(n) skip_bits(s, n);
}
#define init_vlc(vlc, nb_bits, nb_codes,\
bits, bits_wrap, bits_size,\
codes, codes_wrap, codes_size,\
flags)\
init_vlc_sparse(vlc, nb_bits, nb_codes,\
bits, bits_wrap, bits_size,\
codes, codes_wrap, codes_size,\
NULL, 0, 0, flags)
int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
const void *bits, int bits_wrap, int bits_size,
const void *codes, int codes_wrap, int codes_size,
const void *symbols, int symbols_wrap, int symbols_size,
int flags);
#define INIT_VLC_LE 2
#define INIT_VLC_USE_NEW_STATIC 4
void free_vlc(VLC *vlc);
#define INIT_VLC_STATIC(vlc, bits, a,b,c,d,e,f,g, static_size)\
{\
static VLC_TYPE table[static_size][2];\
(vlc)->table= table;\
(vlc)->table_allocated= static_size;\
init_vlc(vlc, bits, a,b,c,d,e,f,g, INIT_VLC_USE_NEW_STATIC);\
}
/**
*
* If the vlc code is invalid and max_depth=1, then no bits will be removed.
* If the vlc code is invalid and max_depth>1, then the number of bits removed
* is undefined.
*/
#define GET_VLC(code, name, gb, table, bits, max_depth)\
{\
int n, nb_bits;\
unsigned int index;\
\
index= SHOW_UBITS(name, gb, bits);\
code = table[index][0];\
n = table[index][1];\
\
if(max_depth > 1 && n < 0){\
LAST_SKIP_BITS(name, gb, bits)\
UPDATE_CACHE(name, gb)\
\
nb_bits = -n;\
\
index= SHOW_UBITS(name, gb, nb_bits) + code;\
code = table[index][0];\
n = table[index][1];\
if(max_depth > 2 && n < 0){\
LAST_SKIP_BITS(name, gb, nb_bits)\
UPDATE_CACHE(name, gb)\
\
nb_bits = -n;\
\
index= SHOW_UBITS(name, gb, nb_bits) + code;\
code = table[index][0];\
n = table[index][1];\
}\
}\
SKIP_BITS(name, gb, n)\
}
#define GET_RL_VLC(level, run, name, gb, table, bits, max_depth, need_update)\
{\
int n, nb_bits;\
unsigned int index;\
\
index= SHOW_UBITS(name, gb, bits);\
level = table[index].level;\
n = table[index].len;\
\
if(max_depth > 1 && n < 0){\
SKIP_BITS(name, gb, bits)\
if(need_update){\
UPDATE_CACHE(name, gb)\
}\
\
nb_bits = -n;\
\
index= SHOW_UBITS(name, gb, nb_bits) + level;\
level = table[index].level;\
n = table[index].len;\
}\
run= table[index].run;\
SKIP_BITS(name, gb, n)\
}
/**
* parses a vlc code, faster then get_vlc()
* @param bits is the number of bits which will be read at once, must be
* identical to nb_bits in init_vlc()
* @param max_depth is the number of times bits bits must be read to completely
* read the longest vlc code
* = (max_vlc_length + bits - 1) / bits
*/
static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
int bits, int max_depth)
{
int code;
OPEN_READER(re, s)
UPDATE_CACHE(re, s)
GET_VLC(code, re, s, table, bits, max_depth)
CLOSE_READER(re, s)
return code;
}
//#define TRACE
#ifdef TRACE
static inline void print_bin(int bits, int n){
int i;
for(i=n-1; i>=0; i--){
av_log(NULL, AV_LOG_DEBUG, "%d", (bits>>i)&1);
}
for(i=n; i<24; i++)
av_log(NULL, AV_LOG_DEBUG, " ");
}
static inline int get_bits_trace(GetBitContext *s, int n, char *file, const char *func, int line){
int r= get_bits(s, n);
print_bin(r, n);
av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d bit @%5d in %s %s:%d\n", r, n, r, get_bits_count(s)-n, file, func, line);
return r;
}
static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2], int bits, int max_depth, char *file, const char *func, int line){
int show= show_bits(s, 24);
int pos= get_bits_count(s);
int r= get_vlc2(s, table, bits, max_depth);
int len= get_bits_count(s) - pos;
int bits2= show>>(24-len);
print_bin(bits2, len);
av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n", bits2, len, r, pos, file, func, line);
return r;
}
static inline int get_xbits_trace(GetBitContext *s, int n, char *file, const char *func, int line){
int show= show_bits(s, n);
int r= get_xbits(s, n);
print_bin(show, n);
av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d xbt @%5d in %s %s:%d\n", show, n, r, get_bits_count(s)-n, file, func, line);
return r;
}
#define get_bits(s, n) get_bits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define get_bits1(s) get_bits_trace(s, 1, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define get_xbits(s, n) get_xbits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define get_vlc(s, vlc) get_vlc_trace(s, (vlc)->table, (vlc)->bits, 3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define get_vlc2(s, tab, bits, max) get_vlc_trace(s, tab, bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define tprintf(p, ...) av_log(p, AV_LOG_DEBUG, __VA_ARGS__)
#else //TRACE
#define tprintf(p, ...) {}
#endif
static inline int decode012(GetBitContext *gb){
int n;
n = get_bits1(gb);
if (n == 0)
return 0;
else
return get_bits1(gb) + 1;
}
static inline int decode210(GetBitContext *gb){
if (get_bits1(gb))
return 0;
else
return 2 - get_bits1(gb);
}
static inline int get_bits_left(GetBitContext *gb)
{
return gb->size_in_bits - get_bits_count(gb);
}
#endif /* AVCODEC_GET_BITS_H */
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