2 * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
4 * This file is part of FFmpeg.
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 * bitstream reader API header.
26 #ifndef AVCODEC_GET_BITS_H
27 #define AVCODEC_GET_BITS_H
31 #include "libavutil/common.h"
32 #include "libavutil/intreadwrite.h"
33 #include "libavutil/log.h"
34 #include "libavutil/avassert.h"
38 * Safe bitstream reading:
39 * optionally, the get_bits API can check to ensure that we
40 * don't read past input buffer boundaries. This is protected
41 * with CONFIG_SAFE_BITSTREAM_READER at the global level, and
42 * then below that with UNCHECKED_BITSTREAM_READER at the per-
43 * decoder level. This means that decoders that check internally
44 * can "#define UNCHECKED_BITSTREAM_READER 1" to disable
46 * Boundary checking causes a minor performance penalty so for
47 * applications that won't want/need this, it can be disabled
48 * globally using "#define CONFIG_SAFE_BITSTREAM_READER 0".
50 #ifndef UNCHECKED_BITSTREAM_READER
51 #define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
54 typedef struct GetBitContext {
55 const uint8_t *buffer, *buffer_end;
58 int size_in_bits_plus8;
61 #define VLC_TYPE int16_t
65 VLC_TYPE (*table)[2]; ///< code, bits
66 int table_size, table_allocated;
69 typedef struct RL_VLC_ELEM {
75 /* Bitstream reader API docs:
77 * arbitrary name which is used as prefix for the internal variables
82 * OPEN_READER(name, gb)
83 * load gb into local variables
85 * CLOSE_READER(name, gb)
86 * store local vars in gb
88 * UPDATE_CACHE(name, gb)
89 * Refill the internal cache from the bitstream.
90 * After this call at least MIN_CACHE_BITS will be available.
93 * Will output the contents of the internal cache,
94 * next bit is MSB of 32 or 64 bit (FIXME 64bit).
96 * SHOW_UBITS(name, gb, num)
97 * Will return the next num bits.
99 * SHOW_SBITS(name, gb, num)
100 * Will return the next num bits and do sign extension.
102 * SKIP_BITS(name, gb, num)
103 * Will skip over the next num bits.
104 * Note, this is equivalent to SKIP_CACHE; SKIP_COUNTER.
106 * SKIP_CACHE(name, gb, num)
107 * Will remove the next num bits from the cache (note SKIP_COUNTER
108 * MUST be called before UPDATE_CACHE / CLOSE_READER).
110 * SKIP_COUNTER(name, gb, num)
111 * Will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS).
113 * LAST_SKIP_BITS(name, gb, num)
114 * Like SKIP_BITS, to be used if next call is UPDATE_CACHE or CLOSE_READER.
116 * BITS_LEFT(name, gb)
117 * Return the number of bits left
119 * For examples see get_bits, show_bits, skip_bits, get_vlc.
122 #ifdef LONG_BITSTREAM_READER
123 # define MIN_CACHE_BITS 32
125 # define MIN_CACHE_BITS 25
128 #if UNCHECKED_BITSTREAM_READER
129 #define OPEN_READER(name, gb) \
130 unsigned int name ## _index = (gb)->index; \
131 unsigned int av_unused name ## _cache
133 #define HAVE_BITS_REMAINING(name, gb) 1
135 #define OPEN_READER(name, gb) \
136 unsigned int name ## _index = (gb)->index; \
137 unsigned int av_unused name ## _cache = 0; \
138 unsigned int av_unused name ## _size_plus8 = (gb)->size_in_bits_plus8
140 #define HAVE_BITS_REMAINING(name, gb) name ## _index < name ## _size_plus8
143 #define CLOSE_READER(name, gb) (gb)->index = name ## _index
145 # ifdef LONG_BITSTREAM_READER
147 # define UPDATE_CACHE_LE(name, gb) name ## _cache = \
148 AV_RL64((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
150 # define UPDATE_CACHE_BE(name, gb) name ## _cache = \
151 AV_RB64((gb)->buffer + (name ## _index >> 3)) >> (32 - (name ## _index & 7))
155 # define UPDATE_CACHE_LE(name, gb) name ## _cache = \
156 AV_RL32((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
158 # define UPDATE_CACHE_BE(name, gb) name ## _cache = \
159 AV_RB32((gb)->buffer + (name ## _index >> 3)) << (name ## _index & 7)
164 #ifdef BITSTREAM_READER_LE
166 # define UPDATE_CACHE(name, gb) UPDATE_CACHE_LE(name, gb)
168 # define SKIP_CACHE(name, gb, num) name ## _cache >>= (num)
172 # define UPDATE_CACHE(name, gb) UPDATE_CACHE_BE(name, gb)
174 # define SKIP_CACHE(name, gb, num) name ## _cache <<= (num)
178 #if UNCHECKED_BITSTREAM_READER
179 # define SKIP_COUNTER(name, gb, num) name ## _index += (num)
181 # define SKIP_COUNTER(name, gb, num) \
182 name ## _index = FFMIN(name ## _size_plus8, name ## _index + (num))
185 #define BITS_LEFT(name, gb) ((int)((gb)->size_in_bits - name ## _index))
187 #define SKIP_BITS(name, gb, num) \
189 SKIP_CACHE(name, gb, num); \
190 SKIP_COUNTER(name, gb, num); \
193 #define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
195 #define SHOW_UBITS_LE(name, gb, num) zero_extend(name ## _cache, num)
196 #define SHOW_SBITS_LE(name, gb, num) sign_extend(name ## _cache, num)
198 #define SHOW_UBITS_BE(name, gb, num) NEG_USR32(name ## _cache, num)
199 #define SHOW_SBITS_BE(name, gb, num) NEG_SSR32(name ## _cache, num)
201 #ifdef BITSTREAM_READER_LE
202 # define SHOW_UBITS(name, gb, num) SHOW_UBITS_LE(name, gb, num)
203 # define SHOW_SBITS(name, gb, num) SHOW_SBITS_LE(name, gb, num)
205 # define SHOW_UBITS(name, gb, num) SHOW_UBITS_BE(name, gb, num)
206 # define SHOW_SBITS(name, gb, num) SHOW_SBITS_BE(name, gb, num)
209 #define GET_CACHE(name, gb) ((uint32_t) name ## _cache)
211 static inline int get_bits_count(const GetBitContext *s)
216 static inline void skip_bits_long(GetBitContext *s, int n)
218 #if UNCHECKED_BITSTREAM_READER
221 s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
226 * read mpeg1 dc style vlc (sign bit + mantissa with no MSB).
227 * if MSB not set it is negative
228 * @param n length in bits
230 static inline int get_xbits(GetBitContext *s, int n)
233 register int32_t cache;
235 av_assert2(n>0 && n<=25);
237 cache = GET_CACHE(re, s);
239 LAST_SKIP_BITS(re, s, n);
241 return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
244 static inline int get_sbits(GetBitContext *s, int n)
248 av_assert2(n>0 && n<=25);
250 tmp = SHOW_SBITS(re, s, n);
251 LAST_SKIP_BITS(re, s, n);
259 static inline unsigned int get_bits(GetBitContext *s, int n)
263 av_assert2(n>0 && n<=25);
265 tmp = SHOW_UBITS(re, s, n);
266 LAST_SKIP_BITS(re, s, n);
271 static inline unsigned int get_bits_le(GetBitContext *s, int n)
275 av_assert2(n>0 && n<=25);
276 UPDATE_CACHE_LE(re, s);
277 tmp = SHOW_UBITS_LE(re, s, n);
278 LAST_SKIP_BITS(re, s, n);
286 static inline unsigned int show_bits(GetBitContext *s, int n)
290 av_assert2(n>0 && n<=25);
292 tmp = SHOW_UBITS(re, s, n);
296 static inline void skip_bits(GetBitContext *s, int n)
299 LAST_SKIP_BITS(re, s, n);
303 static inline unsigned int get_bits1(GetBitContext *s)
305 unsigned int index = s->index;
306 uint8_t result = s->buffer[index >> 3];
307 #ifdef BITSTREAM_READER_LE
308 result >>= index & 7;
311 result <<= index & 7;
314 #if !UNCHECKED_BITSTREAM_READER
315 if (s->index < s->size_in_bits_plus8)
323 static inline unsigned int show_bits1(GetBitContext *s)
325 return show_bits(s, 1);
328 static inline void skip_bits1(GetBitContext *s)
336 static inline unsigned int get_bits_long(GetBitContext *s, int n)
340 } else if (n <= MIN_CACHE_BITS) {
341 return get_bits(s, n);
343 #ifdef BITSTREAM_READER_LE
344 unsigned ret = get_bits(s, 16);
345 return ret | (get_bits(s, n - 16) << 16);
347 unsigned ret = get_bits(s, 16) << (n - 16);
348 return ret | get_bits(s, n - 16);
356 static inline uint64_t get_bits64(GetBitContext *s, int n)
359 return get_bits_long(s, n);
361 #ifdef BITSTREAM_READER_LE
362 uint64_t ret = get_bits_long(s, 32);
363 return ret | (uint64_t) get_bits_long(s, n - 32) << 32;
365 uint64_t ret = (uint64_t) get_bits_long(s, n - 32) << 32;
366 return ret | get_bits_long(s, 32);
372 * Read 0-32 bits as a signed integer.
374 static inline int get_sbits_long(GetBitContext *s, int n)
376 return sign_extend(get_bits_long(s, n), n);
382 static inline unsigned int show_bits_long(GetBitContext *s, int n)
384 if (n <= MIN_CACHE_BITS) {
385 return show_bits(s, n);
387 GetBitContext gb = *s;
388 return get_bits_long(&gb, n);
392 static inline int check_marker(GetBitContext *s, const char *msg)
394 int bit = get_bits1(s);
396 av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
402 * Initialize GetBitContext.
403 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes
404 * larger than the actual read bits because some optimized bitstream
405 * readers read 32 or 64 bit at once and could read over the end
406 * @param bit_size the size of the buffer in bits
407 * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
409 static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
415 if (bit_size >= INT_MAX - 7 || bit_size < 0 || !buffer) {
418 ret = AVERROR_INVALIDDATA;
421 buffer_size = (bit_size + 7) >> 3;
424 s->size_in_bits = bit_size;
425 s->size_in_bits_plus8 = bit_size + 8;
426 s->buffer_end = buffer + buffer_size;
433 * Initialize GetBitContext.
434 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes
435 * larger than the actual read bits because some optimized bitstream
436 * readers read 32 or 64 bit at once and could read over the end
437 * @param byte_size the size of the buffer in bytes
438 * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
440 static inline int init_get_bits8(GetBitContext *s, const uint8_t *buffer,
443 if (byte_size > INT_MAX / 8 || byte_size < 0)
445 return init_get_bits(s, buffer, byte_size * 8);
448 static inline const uint8_t *align_get_bits(GetBitContext *s)
450 int n = -get_bits_count(s) & 7;
453 return s->buffer + (s->index >> 3);
456 #define init_vlc(vlc, nb_bits, nb_codes, \
457 bits, bits_wrap, bits_size, \
458 codes, codes_wrap, codes_size, \
460 ff_init_vlc_sparse(vlc, nb_bits, nb_codes, \
461 bits, bits_wrap, bits_size, \
462 codes, codes_wrap, codes_size, \
465 int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
466 const void *bits, int bits_wrap, int bits_size,
467 const void *codes, int codes_wrap, int codes_size,
468 const void *symbols, int symbols_wrap, int symbols_size,
470 void ff_free_vlc(VLC *vlc);
472 #define INIT_VLC_LE 2
473 #define INIT_VLC_USE_NEW_STATIC 4
475 #define INIT_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size) \
477 static VLC_TYPE table[static_size][2]; \
478 (vlc)->table = table; \
479 (vlc)->table_allocated = static_size; \
480 init_vlc(vlc, bits, a, b, c, d, e, f, g, INIT_VLC_USE_NEW_STATIC); \
484 * If the vlc code is invalid and max_depth=1, then no bits will be removed.
485 * If the vlc code is invalid and max_depth>1, then the number of bits removed
488 #define GET_VLC(code, name, gb, table, bits, max_depth) \
491 unsigned int index; \
493 index = SHOW_UBITS(name, gb, bits); \
494 code = table[index][0]; \
495 n = table[index][1]; \
497 if (max_depth > 1 && n < 0) { \
498 LAST_SKIP_BITS(name, gb, bits); \
499 UPDATE_CACHE(name, gb); \
503 index = SHOW_UBITS(name, gb, nb_bits) + code; \
504 code = table[index][0]; \
505 n = table[index][1]; \
506 if (max_depth > 2 && n < 0) { \
507 LAST_SKIP_BITS(name, gb, nb_bits); \
508 UPDATE_CACHE(name, gb); \
512 index = SHOW_UBITS(name, gb, nb_bits) + code; \
513 code = table[index][0]; \
514 n = table[index][1]; \
517 SKIP_BITS(name, gb, n); \
520 #define GET_RL_VLC_INTERNAL(level, run, name, gb, table, bits, \
521 max_depth, need_update) \
524 unsigned int index; \
526 index = SHOW_UBITS(name, gb, bits); \
527 level = table[index].level; \
528 n = table[index].len; \
530 if (max_depth > 1 && n < 0) { \
531 SKIP_BITS(name, gb, bits); \
533 UPDATE_CACHE(name, gb); \
538 index = SHOW_UBITS(name, gb, nb_bits) + level; \
539 level = table[index].level; \
540 n = table[index].len; \
542 run = table[index].run; \
543 SKIP_BITS(name, gb, n); \
548 * @param bits is the number of bits which will be read at once, must be
549 * identical to nb_bits in init_vlc()
550 * @param max_depth is the number of times bits bits must be read to completely
551 * read the longest vlc code
552 * = (max_vlc_length + bits - 1) / bits
554 static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
555 int bits, int max_depth)
562 GET_VLC(code, re, s, table, bits, max_depth);
569 static inline int decode012(GetBitContext *gb)
576 return get_bits1(gb) + 1;
579 static inline int decode210(GetBitContext *gb)
584 return 2 - get_bits1(gb);
587 static inline int get_bits_left(GetBitContext *gb)
589 return gb->size_in_bits - get_bits_count(gb);
592 static inline int skip_1stop_8data_bits(GetBitContext *gb)
594 if (get_bits_left(gb) <= 0)
595 return AVERROR_INVALIDDATA;
597 while (get_bits1(gb)) {
599 if (get_bits_left(gb) <= 0)
600 return AVERROR_INVALIDDATA;
609 static inline void print_bin(int bits, int n)
613 for (i = n - 1; i >= 0; i--)
614 av_log(NULL, AV_LOG_DEBUG, "%d", (bits >> i) & 1);
615 for (i = n; i < 24; i++)
616 av_log(NULL, AV_LOG_DEBUG, " ");
619 static inline int get_bits_trace(GetBitContext *s, int n, const char *file,
620 const char *func, int line)
622 int r = get_bits(s, n);
625 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d bit @%5d in %s %s:%d\n",
626 r, n, r, get_bits_count(s) - n, file, func, line);
631 static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2],
632 int bits, int max_depth, const char *file,
633 const char *func, int line)
635 int show = show_bits(s, 24);
636 int pos = get_bits_count(s);
637 int r = get_vlc2(s, table, bits, max_depth);
638 int len = get_bits_count(s) - pos;
639 int bits2 = show >> (24 - len);
641 print_bin(bits2, len);
643 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n",
644 bits2, len, r, pos, file, func, line);
649 #define GET_RL_VLC(level, run, name, gb, table, bits, \
650 max_depth, need_update) \
652 int show = SHOW_UBITS(name, gb, 24); \
654 int pos = name ## _index; \
656 GET_RL_VLC_INTERNAL(level, run, name, gb, table, bits,max_depth, need_update); \
658 len = name ## _index - pos + 1; \
659 show = show >> (24 - len); \
661 print_bin(show, len); \
663 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d/%-3d rlv @%5d in %s %s:%d\n",\
664 show, len, run-1, level, pos, __FILE__, __PRETTY_FUNCTION__, __LINE__);\
668 static inline int get_xbits_trace(GetBitContext *s, int n, const char *file,
669 const char *func, int line)
671 int show = show_bits(s, n);
672 int r = get_xbits(s, n);
675 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d xbt @%5d in %s %s:%d\n",
676 show, n, r, get_bits_count(s) - n, file, func, line);
681 #define get_bits(s, n) get_bits_trace(s , n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
682 #define get_bits1(s) get_bits_trace(s, 1, __FILE__, __PRETTY_FUNCTION__, __LINE__)
683 #define get_xbits(s, n) get_xbits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
685 #define get_vlc(s, vlc) get_vlc_trace(s, (vlc)->table, (vlc)->bits, 3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
686 #define get_vlc2(s, tab, bits, max) get_vlc_trace(s, tab, bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)
688 #define tprintf(p, ...) av_log(p, AV_LOG_DEBUG, __VA_ARGS__)
691 #define tprintf(p, ...) { }
692 #define GET_RL_VLC GET_RL_VLC_INTERNAL
695 #endif /* AVCODEC_GET_BITS_H */