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/*
* Copyright (c) 2016 Alexandra Hájková
*
* 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_BITSTREAM_H
#define AVCODEC_BITSTREAM_H
#include <stdint.h>
#include "config.h"
#include "libavutil/common.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/log.h"
#include "mathops.h"
#include "vlc.h"
#ifndef UNCHECKED_BITSTREAM_READER
#define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
#endif
typedef struct BitstreamContext {
uint64_t bits; // stores bits read from the buffer
const uint8_t *buffer, *buffer_end;
const uint8_t *ptr; // pointer to the position inside a buffer
unsigned bits_left; // number of bits left in bits field
unsigned size_in_bits;
} BitstreamContext;
/**
* Return number of bits already read.
*/
static inline int bitstream_tell(const BitstreamContext *bc)
{
return (bc->ptr - bc->buffer) * 8 - bc->bits_left;
}
/**
* Return buffer size in bits.
*/
static inline int bitstream_tell_size(const BitstreamContext *bc)
{
return bc->size_in_bits;
}
/**
* Return the number of the bits left in a buffer.
*/
static inline int bitstream_bits_left(const BitstreamContext *bc)
{
return (bc->buffer - bc->ptr) * 8 + bc->size_in_bits + bc->bits_left;
}
/* Unwind the cache so a refill_32 can fill it again. */
static inline void bitstream_unwind(BitstreamContext *bc)
{
int unwind = 4;
int unwind_bits = unwind * 8;
if (bc->bits_left < unwind_bits)
return;
bc->bits >>= unwind_bits;
bc->bits <<= unwind_bits;
bc->bits_left -= unwind_bits;
bc->ptr -= unwind;
}
/* Unget up to 32 bits. */
static inline void bitstream_unget(BitstreamContext *bc, uint64_t value,
size_t amount)
{
size_t cache_size = sizeof(bc->bits) * 8;
if (bc->bits_left + amount > cache_size)
bitstream_unwind(bc);
bc->bits = (bc->bits >> amount) | (value << (cache_size - amount));
bc->bits_left += amount;
}
#define BITSTREAM_LE
#include "bitstream_template.h"
#undef BITSTREAM_LE
#include "bitstream_template.h"
#define bitstream_init bitstream_init_be
#define bitstream_init8 bitstream_init8_be
#define bitstream_read_bit bitstream_read_bit_be
#define bitstream_read_63 bitstream_read_63_be
#define bitstream_read bitstream_read_be
#define bitstream_read_signed bitstream_read_signed_be
#define bitstream_peek bitstream_peek_be
#define bitstream_peek_signed bitstream_peek_signed_be
#define bitstream_skip bitstream_skip_be
#define bitstream_seek bitstream_seek_be
#define bitstream_align bitstream_align_be
#define bitstream_read_xbits bitstream_read_xbits_be
#define bitstream_decode012 bitstream_decode012_be
#define bitstream_decode210 bitstream_decode210_be
#define bitstream_apply_sign bitstream_apply_sign_be
#define bitstream_read_vlc bitstream_read_vlc_be
#define BITSTREAM_RL_VLC(level, run, bc, table, bits, max_depth) \
do { \
int n, nb_bits; \
unsigned int index = bitstream_peek(bc, bits); \
level = table[index].level; \
n = table[index].len; \
\
if (max_depth > 1 && n < 0) { \
bitstream_skip(bc, bits); \
\
nb_bits = -n; \
\
index = bitstream_peek(bc, nb_bits) + level; \
level = table[index].level; \
n = table[index].len; \
if (max_depth > 2 && n < 0) { \
bitstream_skip(bc, nb_bits); \
nb_bits = -n; \
\
index = bitstream_peek(bc, nb_bits) + level; \
level = table[index].level; \
n = table[index].len; \
} \
} \
run = table[index].run; \
bitstream_skip(bc, n); \
} while (0)
#endif /* AVCODEC_BITSTREAM_H */
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