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FFmpeg/libavcodec/get_bits.h
Andreas Rheinhardt 4ab82d2fb6 avcodec/vlc, bitstream: Fix multi VLC with uint8_t syms on BE 
VLC_MULTI_ELEM contains an uint8_t array that is supposed
to be treated as an array of uint16_t when the used symbols
have a size of two; otherwise it should be treated as just
an array of uint8_t, but it was not always treated that way:

vlc_multi_gen() initialized the first entry of the array
by writing the symbol via AV_WN16; on big endian systems,
the intended value was instead written into the second entry
of the array (where it would likely be overwritten lateron
during initialization).

read_vlc_multi() also treated this case incorrectly: In case
the code is so long that it needs a classical multi-stage lookup,
the symbol has been written to the destination as if via AV_WN16.
On little endian systems, this sets the correct first symbol and
clobbers (zeroes) the next one, but the next one will be overwritten
lateron anyway, so it won't be recognized. But on big-endian systems,
the first symbol will be set to zero and the actually read symbol
will be put into the slot for the next one (where it will be overwritten
lateron).

This commit fixes this; this fixes the magicyuv and utvideo FATE-tests
on big endian arches.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
2024-04-02 00:21:59 +02:00

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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 "libavutil/common.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/avassert.h"
#include "defs.h"
#include "mathops.h"
#include "vlc.h"
/*
* Safe bitstream reading:
* optionally, the get_bits API can check to ensure that we
* don't read past input buffer boundaries. This is protected
* with CONFIG_SAFE_BITSTREAM_READER at the global level, and
* then below that with UNCHECKED_BITSTREAM_READER at the per-
* decoder level. This means that decoders that check internally
* can "#define UNCHECKED_BITSTREAM_READER 1" to disable
* overread checks.
* Boundary checking causes a minor performance penalty so for
* applications that won't want/need this, it can be disabled
* globally using "#define CONFIG_SAFE_BITSTREAM_READER 0".
*/
#ifndef UNCHECKED_BITSTREAM_READER
#define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
#endif
#ifndef CACHED_BITSTREAM_READER
#define CACHED_BITSTREAM_READER 0
#endif
#if CACHED_BITSTREAM_READER
// we always want the LE implementation, to provide get_bits_le()
#define BITSTREAM_LE
#ifndef BITSTREAM_READER_LE
# define BITSTREAM_BE
# define BITSTREAM_DEFAULT_BE
#endif
#include "bitstream.h"
#undef BITSTREAM_LE
#undef BITSTREAM_BE
#undef BITSTREAM_DEFAULT_BE
typedef BitstreamContext GetBitContext;
#define get_bits_count bits_tell
#define get_bits_left bits_left
#define skip_bits_long bits_skip
#define skip_bits bits_skip
#define get_bits bits_read_nz
#define get_bitsz bits_read
#define get_bits_long bits_read
#define get_bits1 bits_read_bit
#define get_bits64 bits_read_64
#define get_xbits bits_read_xbits
#define get_sbits bits_read_signed_nz
#define get_sbits_long bits_read_signed
#define show_bits bits_peek
#define show_bits_long bits_peek
#define init_get_bits bits_init
#define init_get_bits8 bits_init8
#define align_get_bits bits_align
#define get_vlc2 bits_read_vlc
#define get_vlc_multi bits_read_vlc_multi
#define init_get_bits8_le(s, buffer, byte_size) bits_init8_le((BitstreamContextLE*)s, buffer, byte_size)
#define get_bits_le(s, n) bits_read_le((BitstreamContextLE*)s, n)
#define show_bits1(s) bits_peek(s, 1)
#define skip_bits1(s) bits_skip(s, 1)
#define skip_1stop_8data_bits bits_skip_1stop_8data
#else // CACHED_BITSTREAM_READER
typedef struct GetBitContext {
const uint8_t *buffer, *buffer_end;
int index;
int size_in_bits;
int size_in_bits_plus8;
} GetBitContext;
static inline unsigned int get_bits(GetBitContext *s, int n);
static inline void skip_bits(GetBitContext *s, int n);
static inline unsigned int show_bits(GetBitContext *s, int n);
/* Bitstream reader API docs:
* name
* arbitrary name which is used as prefix for the internal variables
*
* gb
* getbitcontext
*
* OPEN_READER(name, gb)
* load gb into local variables
*
* CLOSE_READER(name, gb)
* store local vars in gb
*
* UPDATE_CACHE(name, gb)
* Refill 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 bits (FIXME 64 bits).
*
* 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_BITS(name, gb, num)
* Like SKIP_BITS, to be used if next call is UPDATE_CACHE or CLOSE_READER.
*
* BITS_LEFT(name, gb)
* Return the number of bits left
*
* For examples see get_bits, show_bits, skip_bits, get_vlc.
*/
#if defined LONG_BITSTREAM_READER
# define MIN_CACHE_BITS 32
#else
# define MIN_CACHE_BITS 25
#endif
#define OPEN_READER_NOSIZE(name, gb) \
unsigned int name ## _index = (gb)->index; \
unsigned int av_unused name ## _cache
#if UNCHECKED_BITSTREAM_READER
#define OPEN_READER(name, gb) OPEN_READER_NOSIZE(name, gb)
#define BITS_AVAILABLE(name, gb) 1
#else
#define OPEN_READER(name, gb) \
OPEN_READER_NOSIZE(name, gb); \
unsigned int name ## _size_plus8 = (gb)->size_in_bits_plus8
#define BITS_AVAILABLE(name, gb) name ## _index < name ## _size_plus8
#endif
#define CLOSE_READER(name, gb) (gb)->index = name ## _index
#define UPDATE_CACHE_BE_EXT(name, gb, bits, dst_bits) name ## _cache = \
AV_RB ## bits((gb)->buffer + (name ## _index >> 3)) << (name ## _index & 7) >> (bits - dst_bits)
#define UPDATE_CACHE_LE_EXT(name, gb, bits, dst_bits) name ## _cache = \
(uint ## dst_bits ## _t)(AV_RL ## bits((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7))
/* Using these two macros ensures that 32 bits are available. */
# define UPDATE_CACHE_LE_32(name, gb) UPDATE_CACHE_LE_EXT(name, (gb), 64, 32)
# define UPDATE_CACHE_BE_32(name, gb) UPDATE_CACHE_BE_EXT(name, (gb), 64, 32)
# ifdef LONG_BITSTREAM_READER
# define UPDATE_CACHE_LE(name, gb) UPDATE_CACHE_LE_32(name, (gb))
# define UPDATE_CACHE_BE(name, gb) UPDATE_CACHE_BE_32(name, (gb))
#else
# define UPDATE_CACHE_LE(name, gb) UPDATE_CACHE_LE_EXT(name, (gb), 32, 32)
# define UPDATE_CACHE_BE(name, gb) UPDATE_CACHE_BE_EXT(name, (gb), 32, 32)
#endif
#ifdef BITSTREAM_READER_LE
# define UPDATE_CACHE(name, gb) UPDATE_CACHE_LE(name, gb)
# define UPDATE_CACHE_32(name, gb) UPDATE_CACHE_LE_32(name, (gb))
# define SKIP_CACHE(name, gb, num) name ## _cache >>= (num)
#else
# define UPDATE_CACHE(name, gb) UPDATE_CACHE_BE(name, gb)
# define UPDATE_CACHE_32(name, gb) UPDATE_CACHE_BE_32(name, (gb))
# define SKIP_CACHE(name, gb, num) name ## _cache <<= (num)
#endif
#if UNCHECKED_BITSTREAM_READER
# define SKIP_COUNTER(name, gb, num) name ## _index += (num)
#else
# define SKIP_COUNTER(name, gb, num) \
name ## _index = FFMIN(name ## _size_plus8, name ## _index + (num))
#endif
#define BITS_LEFT(name, gb) ((int)((gb)->size_in_bits - name ## _index))
#define SKIP_BITS(name, gb, num) \
do { \
SKIP_CACHE(name, gb, num); \
SKIP_COUNTER(name, gb, num); \
} while (0)
#define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
#define SHOW_UBITS_LE(name, gb, num) zero_extend(name ## _cache, num)
#define SHOW_SBITS_LE(name, gb, num) sign_extend(name ## _cache, num)
#define SHOW_UBITS_BE(name, gb, num) NEG_USR32(name ## _cache, num)
#define SHOW_SBITS_BE(name, gb, num) NEG_SSR32(name ## _cache, num)
#ifdef BITSTREAM_READER_LE
# define SHOW_UBITS(name, gb, num) SHOW_UBITS_LE(name, gb, num)
# define SHOW_SBITS(name, gb, num) SHOW_SBITS_LE(name, gb, num)
#else
# define SHOW_UBITS(name, gb, num) SHOW_UBITS_BE(name, gb, num)
# define SHOW_SBITS(name, gb, num) SHOW_SBITS_BE(name, gb, num)
#endif
#define GET_CACHE(name, gb) ((uint32_t) name ## _cache)
static inline int get_bits_count(const GetBitContext *s)
{
return s->index;
}
/**
* Skips the specified number of bits.
* @param n the number of bits to skip,
* For the UNCHECKED_BITSTREAM_READER this must not cause the distance
* from the start to overflow int32_t. Staying within the bitstream + padding
* is sufficient, too.
*/
static inline void skip_bits_long(GetBitContext *s, int n)
{
#if UNCHECKED_BITSTREAM_READER
s->index += n;
#else
s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
#endif
}
/**
* Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB).
* if MSB not set it is negative
* @param n length in bits
*/
static inline int get_xbits(GetBitContext *s, int n)
{
register int sign;
register int32_t cache;
OPEN_READER(re, s);
av_assert2(n>0 && n<=25);
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_xbits_le(GetBitContext *s, int n)
{
register int sign;
register int32_t cache;
OPEN_READER(re, s);
av_assert2(n>0 && n<=25);
UPDATE_CACHE_LE(re, s);
cache = GET_CACHE(re, s);
sign = sign_extend(~cache, n) >> 31;
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
return (zero_extend(sign ^ cache, n) ^ sign) - sign;
}
static inline int get_sbits(GetBitContext *s, int n)
{
register int tmp;
OPEN_READER(re, s);
av_assert2(n>0 && n<=25);
UPDATE_CACHE(re, s);
tmp = SHOW_SBITS(re, s, n);
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
return tmp;
}
/**
* Read 1-25 bits.
*/
static inline unsigned int get_bits(GetBitContext *s, int n)
{
register unsigned int tmp;
OPEN_READER(re, s);
av_assert2(n>0 && n<=25);
UPDATE_CACHE(re, s);
tmp = SHOW_UBITS(re, s, n);
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
av_assert2(tmp < UINT64_C(1) << n);
return tmp;
}
/**
* Read 0-25 bits.
*/
static av_always_inline int get_bitsz(GetBitContext *s, int n)
{
return n ? get_bits(s, n) : 0;
}
static inline unsigned int get_bits_le(GetBitContext *s, int n)
{
register int tmp;
OPEN_READER(re, s);
av_assert2(n>0 && n<=25);
UPDATE_CACHE_LE(re, s);
tmp = SHOW_UBITS_LE(re, s, n);
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
return tmp;
}
/**
* Show 1-25 bits.
*/
static inline unsigned int show_bits(GetBitContext *s, int n)
{
register unsigned int tmp;
OPEN_READER_NOSIZE(re, s);
av_assert2(n>0 && n<=25);
UPDATE_CACHE(re, s);
tmp = SHOW_UBITS(re, s, n);
return tmp;
}
static inline void skip_bits(GetBitContext *s, int n)
{
OPEN_READER(re, s);
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
}
static inline unsigned int get_bits1(GetBitContext *s)
{
unsigned int index = s->index;
uint8_t result = s->buffer[index >> 3];
#ifdef BITSTREAM_READER_LE
result >>= index & 7;
result &= 1;
#else
result <<= index & 7;
result >>= 8 - 1;
#endif
#if !UNCHECKED_BITSTREAM_READER
if (s->index < s->size_in_bits_plus8)
#endif
index++;
s->index = index;
return result;
}
static inline unsigned int show_bits1(GetBitContext *s)
{
return show_bits(s, 1);
}
static inline void skip_bits1(GetBitContext *s)
{
skip_bits(s, 1);
}
/**
* Read 0-32 bits.
*/
static inline unsigned int get_bits_long(GetBitContext *s, int n)
{
av_assert2(n>=0 && n<=32);
if (!n) {
return 0;
} else if ((!HAVE_FAST_64BIT || av_builtin_constant_p(n <= MIN_CACHE_BITS))
&& n <= MIN_CACHE_BITS) {
return get_bits(s, n);
} else {
#if HAVE_FAST_64BIT
unsigned tmp;
OPEN_READER(re, s);
UPDATE_CACHE_32(re, s);
tmp = SHOW_UBITS(re, s, n);
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
return tmp;
#else
#ifdef BITSTREAM_READER_LE
unsigned ret = get_bits(s, 16);
return ret | (get_bits(s, n - 16) << 16);
#else
unsigned ret = get_bits(s, 16) << (n - 16);
return ret | get_bits(s, n - 16);
#endif
#endif
}
}
/**
* Read 0-64 bits.
*/
static inline uint64_t get_bits64(GetBitContext *s, int n)
{
if (n <= 32) {
return get_bits_long(s, n);
} else {
#ifdef BITSTREAM_READER_LE
uint64_t ret = get_bits_long(s, 32);
return ret | (uint64_t) get_bits_long(s, n - 32) << 32;
#else
uint64_t ret = (uint64_t) get_bits_long(s, n - 32) << 32;
return ret | get_bits_long(s, 32);
#endif
}
}
/**
* Read 0-32 bits as a signed integer.
*/
static inline int get_sbits_long(GetBitContext *s, int n)
{
// sign_extend(x, 0) is undefined
if (!n)
return 0;
return sign_extend(get_bits_long(s, n), n);
}
/**
* Read 0-64 bits as a signed integer.
*/
static inline int64_t get_sbits64(GetBitContext *s, int n)
{
// sign_extend(x, 0) is undefined
if (!n)
return 0;
return sign_extend64(get_bits64(s, n), n);
}
/**
* Show 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);
}
}
/**
* Initialize GetBitContext.
* @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
* larger than 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
* @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
*/
static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
int bit_size)
{
int buffer_size;
int ret = 0;
if (bit_size >= INT_MAX - FFMAX(7, AV_INPUT_BUFFER_PADDING_SIZE*8) || bit_size < 0 || !buffer) {
bit_size = 0;
buffer = NULL;
ret = AVERROR_INVALIDDATA;
}
buffer_size = (bit_size + 7) >> 3;
s->buffer = buffer;
s->size_in_bits = bit_size;
s->size_in_bits_plus8 = bit_size + 8;
s->buffer_end = buffer + buffer_size;
s->index = 0;
return ret;
}
/**
* Initialize GetBitContext.
* @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
* larger than the actual read bits because some optimized bitstream
* readers read 32 or 64 bit at once and could read over the end
* @param byte_size the size of the buffer in bytes
* @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
*/
static inline int init_get_bits8(GetBitContext *s, const uint8_t *buffer,
int byte_size)
{
if (byte_size > INT_MAX / 8 || byte_size < 0)
byte_size = -1;
return init_get_bits(s, buffer, byte_size * 8);
}
static inline int init_get_bits8_le(GetBitContext *s, const uint8_t *buffer,
int byte_size)
{
if (byte_size > INT_MAX / 8 || byte_size < 0)
byte_size = -1;
return init_get_bits(s, buffer, byte_size * 8);
}
static inline const uint8_t *align_get_bits(GetBitContext *s)
{
int n = -get_bits_count(s) & 7;
if (n)
skip_bits(s, n);
return s->buffer + (s->index >> 3);
}
/**
* 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) \
do { \
int n, nb_bits; \
unsigned int index; \
\
index = SHOW_UBITS(name, gb, bits); \
code = table[index].sym; \
n = table[index].len; \
\
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].sym; \
n = table[index].len; \
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].sym; \
n = table[index].len; \
} \
} \
SKIP_BITS(name, gb, n); \
} while (0)
#define GET_RL_VLC(level, run, name, gb, table, bits, \
max_depth, need_update) \
do { \
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; \
if (max_depth > 2 && n < 0) { \
LAST_SKIP_BITS(name, gb, nb_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); \
} while (0)
/**
* Parse a vlc code.
* @param bits is the number of bits which will be read at once, must be
* identical to nb_bits in vlc_init()
* @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
* @returns the code parsed or -1 if no vlc matches
*/
static av_always_inline int get_vlc2(GetBitContext *s, const VLCElem *table,
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;
}
static inline int get_vlc_multi(GetBitContext *s, uint8_t *dst,
const VLC_MULTI_ELEM *const Jtable,
const VLCElem *const table,
const int bits, const int max_depth,
const int symbols_size)
{
dst[0] = get_vlc2(s, table, bits, max_depth);
return 1;
}
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);
}
static inline int skip_1stop_8data_bits(GetBitContext *gb)
{
if (get_bits_left(gb) <= 0)
return AVERROR_INVALIDDATA;
while (get_bits1(gb)) {
skip_bits(gb, 8);
if (get_bits_left(gb) <= 0)
return AVERROR_INVALIDDATA;
}
return 0;
}
#endif // CACHED_BITSTREAM_READER
#endif /* AVCODEC_GET_BITS_H */
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