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532 lines
16 KiB
C
532 lines
16 KiB
C
/*
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* copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* bitstream reader API header.
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*/
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#ifndef AVCODEC_GET_BITS_H
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#define AVCODEC_GET_BITS_H
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#include <stdint.h>
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#include "libavutil/common.h"
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#include "libavutil/intreadwrite.h"
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#include "libavutil/log.h"
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#include "mathops.h"
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#include "vlc.h"
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/*
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* Safe bitstream reading:
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* optionally, the get_bits API can check to ensure that we
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* don't read past input buffer boundaries. This is protected
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* with CONFIG_SAFE_BITSTREAM_READER at the global level, and
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* then below that with UNCHECKED_BITSTREAM_READER at the per-
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* decoder level. This means that decoders that check internally
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* can "#define UNCHECKED_BITSTREAM_READER 1" to disable
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* overread checks.
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* Boundary checking causes a minor performance penalty so for
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* applications that won't want/need this, it can be disabled
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* globally using "#define CONFIG_SAFE_BITSTREAM_READER 0".
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*/
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#ifndef UNCHECKED_BITSTREAM_READER
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#define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
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#endif
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typedef struct GetBitContext {
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const uint8_t *buffer, *buffer_end;
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int index;
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int size_in_bits;
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#if !UNCHECKED_BITSTREAM_READER
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int size_in_bits_plus8;
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#endif
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} GetBitContext;
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/* Bitstream reader API docs:
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* name
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* arbitrary name which is used as prefix for the internal variables
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*
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* gb
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* getbitcontext
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*
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* OPEN_READER(name, gb)
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* load gb into local variables
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*
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* CLOSE_READER(name, gb)
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* store local vars in gb
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*
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* UPDATE_CACHE(name, gb)
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* Refill the internal cache from the bitstream.
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* After this call at least MIN_CACHE_BITS will be available.
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*
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* GET_CACHE(name, gb)
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* Will output the contents of the internal cache,
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* next bit is MSB of 32 or 64 bits (FIXME 64 bits).
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*
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* SHOW_UBITS(name, gb, num)
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* Will return the next num bits.
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*
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* SHOW_SBITS(name, gb, num)
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* Will return the next num bits and do sign extension.
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*
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* SKIP_BITS(name, gb, num)
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* Will skip over the next num bits.
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* Note, this is equivalent to SKIP_CACHE; SKIP_COUNTER.
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*
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* SKIP_CACHE(name, gb, num)
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* Will remove the next num bits from the cache (note SKIP_COUNTER
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* MUST be called before UPDATE_CACHE / CLOSE_READER).
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*
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* SKIP_COUNTER(name, gb, num)
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* Will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS).
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*
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* LAST_SKIP_BITS(name, gb, num)
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* Like SKIP_BITS, to be used if next call is UPDATE_CACHE or CLOSE_READER.
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*
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* For examples see get_bits, show_bits, skip_bits, get_vlc.
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*/
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#ifdef LONG_BITSTREAM_READER
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# define MIN_CACHE_BITS 32
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#else
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# define MIN_CACHE_BITS 25
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#endif
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#define OPEN_READER_NOSIZE(name, gb) \
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unsigned int name ## _index = (gb)->index; \
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unsigned int av_unused name ## _cache = 0
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#if UNCHECKED_BITSTREAM_READER
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#define OPEN_READER(name, gb) OPEN_READER_NOSIZE(name, gb)
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#define BITS_AVAILABLE(name, gb) 1
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#else
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#define OPEN_READER(name, gb) \
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OPEN_READER_NOSIZE(name, gb); \
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unsigned int name ## _size_plus8 = (gb)->size_in_bits_plus8
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#define BITS_AVAILABLE(name, gb) name ## _index < name ## _size_plus8
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#endif
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#define CLOSE_READER(name, gb) (gb)->index = name ## _index
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#ifdef BITSTREAM_READER_LE
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# ifdef LONG_BITSTREAM_READER
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# define UPDATE_CACHE(name, gb) name ## _cache = \
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AV_RL64((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
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# else
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# define UPDATE_CACHE(name, gb) name ## _cache = \
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AV_RL32((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
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# endif
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# define SKIP_CACHE(name, gb, num) name ## _cache >>= (num)
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#else
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# ifdef LONG_BITSTREAM_READER
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# define UPDATE_CACHE(name, gb) name ## _cache = \
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AV_RB64((gb)->buffer + (name ## _index >> 3)) >> (32 - (name ## _index & 7))
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# else
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# define UPDATE_CACHE(name, gb) name ## _cache = \
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AV_RB32((gb)->buffer + (name ## _index >> 3)) << (name ## _index & 7)
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# endif
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# define SKIP_CACHE(name, gb, num) name ## _cache <<= (num)
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#endif
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#if UNCHECKED_BITSTREAM_READER
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# define SKIP_COUNTER(name, gb, num) name ## _index += (num)
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#else
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# define SKIP_COUNTER(name, gb, num) \
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name ## _index = FFMIN(name ## _size_plus8, name ## _index + (num))
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#endif
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#define SKIP_BITS(name, gb, num) \
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do { \
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SKIP_CACHE(name, gb, num); \
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SKIP_COUNTER(name, gb, num); \
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} while (0)
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#define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
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#ifdef BITSTREAM_READER_LE
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# define SHOW_UBITS(name, gb, num) zero_extend(name ## _cache, num)
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# define SHOW_SBITS(name, gb, num) sign_extend(name ## _cache, num)
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#else
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# define SHOW_UBITS(name, gb, num) NEG_USR32(name ## _cache, num)
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# define SHOW_SBITS(name, gb, num) NEG_SSR32(name ## _cache, num)
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#endif
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#define GET_CACHE(name, gb) ((uint32_t) name ## _cache)
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static inline int get_bits_count(const GetBitContext *s)
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{
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return s->index;
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}
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static inline void skip_bits_long(GetBitContext *s, int n)
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{
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#if UNCHECKED_BITSTREAM_READER
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s->index += n;
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#else
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s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
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#endif
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}
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/**
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* Read MPEG-1 dc-style VLC (sign bit + mantisse with no MSB).
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* if MSB not set it is negative
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* @param n length in bits
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*/
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static inline int get_xbits(GetBitContext *s, int n)
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{
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register int sign;
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register int32_t cache;
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OPEN_READER(re, s);
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UPDATE_CACHE(re, s);
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cache = GET_CACHE(re, s);
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sign = ~cache >> 31;
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LAST_SKIP_BITS(re, s, n);
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CLOSE_READER(re, s);
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return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
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}
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static inline int get_sbits(GetBitContext *s, int n)
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{
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register int tmp;
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OPEN_READER(re, s);
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UPDATE_CACHE(re, s);
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tmp = SHOW_SBITS(re, s, n);
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LAST_SKIP_BITS(re, s, n);
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CLOSE_READER(re, s);
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return tmp;
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}
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/**
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* Read 1-25 bits.
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*/
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static inline unsigned int get_bits(GetBitContext *s, int n)
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{
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register int tmp;
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OPEN_READER(re, s);
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UPDATE_CACHE(re, s);
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tmp = SHOW_UBITS(re, s, n);
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LAST_SKIP_BITS(re, s, n);
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CLOSE_READER(re, s);
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return tmp;
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}
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/**
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* Read 0-25 bits.
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*/
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static av_always_inline int get_bitsz(GetBitContext *s, int n)
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{
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return n ? get_bits(s, n) : 0;
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}
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/**
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* Show 1-25 bits.
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*/
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static inline unsigned int show_bits(GetBitContext *s, int n)
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{
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register int tmp;
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OPEN_READER_NOSIZE(re, s);
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UPDATE_CACHE(re, s);
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tmp = SHOW_UBITS(re, s, n);
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return tmp;
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}
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static inline void skip_bits(GetBitContext *s, int n)
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{
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OPEN_READER(re, s);
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UPDATE_CACHE(re, s);
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LAST_SKIP_BITS(re, s, n);
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CLOSE_READER(re, s);
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}
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static inline unsigned int get_bits1(GetBitContext *s)
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{
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unsigned int index = s->index;
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uint8_t result = s->buffer[index >> 3];
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#ifdef BITSTREAM_READER_LE
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result >>= index & 7;
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result &= 1;
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#else
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result <<= index & 7;
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result >>= 8 - 1;
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#endif
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#if !UNCHECKED_BITSTREAM_READER
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if (s->index < s->size_in_bits_plus8)
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#endif
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index++;
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s->index = index;
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return result;
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}
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static inline unsigned int show_bits1(GetBitContext *s)
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{
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return show_bits(s, 1);
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}
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static inline void skip_bits1(GetBitContext *s)
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{
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skip_bits(s, 1);
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}
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/**
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* Read 0-32 bits.
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*/
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static inline unsigned int get_bits_long(GetBitContext *s, int n)
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{
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if (n <= MIN_CACHE_BITS) {
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return get_bits(s, n);
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} else {
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#ifdef BITSTREAM_READER_LE
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int ret = get_bits(s, 16);
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return ret | (get_bits(s, n - 16) << 16);
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#else
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int ret = get_bits(s, 16) << (n - 16);
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return ret | get_bits(s, n - 16);
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#endif
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}
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}
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/*
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* Read 0-64 bits.
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*/
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static inline uint64_t get_bits64(GetBitContext *s, int n)
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{
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if (n <= 32) {
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return get_bits_long(s, n);
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} else {
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#ifdef BITSTREAM_READER_LE
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uint64_t ret = get_bits_long(s, 32);
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return ret | (uint64_t) get_bits_long(s, n - 32) << 32;
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#else
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uint64_t ret = (uint64_t) get_bits_long(s, n - 32) << 32;
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return ret | get_bits_long(s, 32);
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#endif
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}
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}
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/**
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* Read 0-32 bits as a signed integer.
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*/
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static inline int get_sbits_long(GetBitContext *s, int n)
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{
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return sign_extend(get_bits_long(s, n), n);
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}
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/**
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* Show 0-32 bits.
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*/
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static inline unsigned int show_bits_long(GetBitContext *s, int n)
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{
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if (n <= MIN_CACHE_BITS) {
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return show_bits(s, n);
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} else {
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GetBitContext gb = *s;
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return get_bits_long(&gb, n);
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}
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}
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/**
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* Initialize GetBitContext.
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* @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
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* larger than the actual read bits because some optimized bitstream
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* readers read 32 or 64 bit at once and could read over the end
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* @param bit_size the size of the buffer in bits
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* @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
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*/
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static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
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int bit_size)
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{
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int buffer_size;
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int ret = 0;
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if (bit_size > INT_MAX - 7 || bit_size < 0 || !buffer) {
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bit_size = 0;
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buffer = NULL;
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ret = AVERROR_INVALIDDATA;
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}
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buffer_size = (bit_size + 7) >> 3;
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s->buffer = buffer;
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s->size_in_bits = bit_size;
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#if !UNCHECKED_BITSTREAM_READER
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s->size_in_bits_plus8 = bit_size + 8;
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#endif
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s->buffer_end = buffer + buffer_size;
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s->index = 0;
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return ret;
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}
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/**
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* Initialize GetBitContext.
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* @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
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* larger than the actual read bits because some optimized bitstream
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* readers read 32 or 64 bit at once and could read over the end
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* @param byte_size the size of the buffer in bytes
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* @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
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*/
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static inline int init_get_bits8(GetBitContext *s, const uint8_t *buffer,
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int byte_size)
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{
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if (byte_size > INT_MAX / 8)
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return AVERROR_INVALIDDATA;
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return init_get_bits(s, buffer, byte_size * 8);
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}
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static inline const uint8_t *align_get_bits(GetBitContext *s)
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{
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int n = -get_bits_count(s) & 7;
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if (n)
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skip_bits(s, n);
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return s->buffer + (s->index >> 3);
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}
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/**
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* If the vlc code is invalid and max_depth=1, then no bits will be removed.
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* If the vlc code is invalid and max_depth>1, then the number of bits removed
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* is undefined.
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*/
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#define GET_VLC(code, name, gb, table, bits, max_depth) \
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do { \
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int n, nb_bits; \
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unsigned int index; \
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\
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index = SHOW_UBITS(name, gb, bits); \
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code = table[index][0]; \
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n = table[index][1]; \
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\
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if (max_depth > 1 && n < 0) { \
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LAST_SKIP_BITS(name, gb, bits); \
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UPDATE_CACHE(name, gb); \
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\
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nb_bits = -n; \
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\
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index = SHOW_UBITS(name, gb, nb_bits) + code; \
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code = table[index][0]; \
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n = table[index][1]; \
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if (max_depth > 2 && n < 0) { \
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LAST_SKIP_BITS(name, gb, nb_bits); \
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UPDATE_CACHE(name, gb); \
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\
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nb_bits = -n; \
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\
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index = SHOW_UBITS(name, gb, nb_bits) + code; \
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code = table[index][0]; \
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n = table[index][1]; \
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} \
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} \
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SKIP_BITS(name, gb, n); \
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} while (0)
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#define GET_RL_VLC(level, run, name, gb, table, bits, \
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max_depth, need_update) \
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do { \
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int n, nb_bits; \
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unsigned int index; \
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\
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index = SHOW_UBITS(name, gb, bits); \
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level = table[index].level; \
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n = table[index].len; \
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\
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if (max_depth > 1 && n < 0) { \
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SKIP_BITS(name, gb, bits); \
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if (need_update) { \
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UPDATE_CACHE(name, gb); \
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} \
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\
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nb_bits = -n; \
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\
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index = SHOW_UBITS(name, gb, nb_bits) + level; \
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level = table[index].level; \
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n = table[index].len; \
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if (max_depth > 2 && n < 0) { \
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LAST_SKIP_BITS(name, gb, nb_bits); \
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if (need_update) { \
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UPDATE_CACHE(name, gb); \
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} \
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nb_bits = -n; \
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\
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index = SHOW_UBITS(name, gb, nb_bits) + level; \
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level = table[index].level; \
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n = table[index].len; \
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} \
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} \
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run = table[index].run; \
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SKIP_BITS(name, gb, n); \
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} while (0)
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/**
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* Parse a vlc code.
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* @param bits is the number of bits which will be read at once, must be
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* identical to nb_bits in init_vlc()
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* @param max_depth is the number of times bits bits must be read to completely
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* read the longest vlc code
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* = (max_vlc_length + bits - 1) / bits
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*/
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static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
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int bits, int max_depth)
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{
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int code;
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OPEN_READER(re, s);
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UPDATE_CACHE(re, s);
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GET_VLC(code, re, s, table, bits, max_depth);
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CLOSE_READER(re, s);
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return code;
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}
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static inline int decode012(GetBitContext *gb)
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{
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int n;
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n = get_bits1(gb);
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if (n == 0)
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return 0;
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else
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return get_bits1(gb) + 1;
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}
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static inline int decode210(GetBitContext *gb)
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|
{
|
|
if (get_bits1(gb))
|
|
return 0;
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else
|
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return 2 - get_bits1(gb);
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|
}
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static inline int get_bits_left(GetBitContext *gb)
|
|
{
|
|
return gb->size_in_bits - get_bits_count(gb);
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|
}
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#endif /* AVCODEC_GET_BITS_H */
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