/* * 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/log.h" #include "libavutil/avassert.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 typedef struct GetBitContext { const uint8_t *buffer, *buffer_end; int index; int size_in_bits; int size_in_bits_plus8; } GetBitContext; /* 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. */ #ifdef 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 # ifdef LONG_BITSTREAM_READER # define UPDATE_CACHE_LE(name, gb) name ## _cache = \ AV_RL64((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7) # define UPDATE_CACHE_BE(name, gb) name ## _cache = \ AV_RB64((gb)->buffer + (name ## _index >> 3)) >> (32 - (name ## _index & 7)) #else # define UPDATE_CACHE_LE(name, gb) name ## _cache = \ AV_RL32((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7) # define UPDATE_CACHE_BE(name, gb) name ## _cache = \ AV_RB32((gb)->buffer + (name ## _index >> 3)) << (name ## _index & 7) #endif #ifdef BITSTREAM_READER_LE # define UPDATE_CACHE(name, gb) UPDATE_CACHE_LE(name, gb) # define SKIP_CACHE(name, gb, num) name ## _cache >>= (num) #else # define UPDATE_CACHE(name, gb) UPDATE_CACHE_BE(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; } 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 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); 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 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 (n <= MIN_CACHE_BITS) { return get_bits(s, n); } 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 } } /** * 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); } /** * 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); } } static inline int check_marker(void *logctx, GetBitContext *s, const char *msg) { int bit = get_bits1(s); if (!bit) av_log(logctx, AV_LOG_INFO, "Marker bit missing at %d of %d %s\n", get_bits_count(s) - 1, s->size_in_bits, msg); return bit; } /** * 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 - 7 || 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 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][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); \ } 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 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 * @returns the code parsed or -1 if no vlc matches */ 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; } 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 /* AVCODEC_GET_BITS_H */