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 * For examples see get_bits, show_bits, skip_bits, get_vlc.
119 #ifdef LONG_BITSTREAM_READER
120 # define MIN_CACHE_BITS 32
122 # define MIN_CACHE_BITS 25
125 #if UNCHECKED_BITSTREAM_READER
126 #define OPEN_READER(name, gb) \
127 unsigned int name ## _index = (gb)->index; \
128 unsigned int av_unused name ## _cache
130 #define HAVE_BITS_REMAINING(name, gb) 1
132 #define OPEN_READER(name, gb) \
133 unsigned int name ## _index = (gb)->index; \
134 unsigned int av_unused name ## _cache = 0; \
135 unsigned int av_unused name ## _size_plus8 = (gb)->size_in_bits_plus8
137 #define HAVE_BITS_REMAINING(name, gb) name ## _index < name ## _size_plus8
140 #define CLOSE_READER(name, gb) (gb)->index = name ## _index
142 #ifdef BITSTREAM_READER_LE
144 # ifdef LONG_BITSTREAM_READER
145 # define UPDATE_CACHE(name, gb) name ## _cache = \
146 AV_RL64((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
148 # define UPDATE_CACHE(name, gb) name ## _cache = \
149 AV_RL32((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
152 # define SKIP_CACHE(name, gb, num) name ## _cache >>= (num)
156 # ifdef LONG_BITSTREAM_READER
157 # define UPDATE_CACHE(name, gb) name ## _cache = \
158 AV_RB64((gb)->buffer + (name ## _index >> 3)) >> (32 - (name ## _index & 7))
160 # define UPDATE_CACHE(name, gb) name ## _cache = \
161 AV_RB32((gb)->buffer + (name ## _index >> 3)) << (name ## _index & 7)
164 # define SKIP_CACHE(name, gb, num) name ## _cache <<= (num)
168 #if UNCHECKED_BITSTREAM_READER
169 # define SKIP_COUNTER(name, gb, num) name ## _index += (num)
171 # define SKIP_COUNTER(name, gb, num) \
172 name ## _index = FFMIN(name ## _size_plus8, name ## _index + (num))
175 #define SKIP_BITS(name, gb, num) \
177 SKIP_CACHE(name, gb, num); \
178 SKIP_COUNTER(name, gb, num); \
181 #define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
183 #ifdef BITSTREAM_READER_LE
184 # define SHOW_UBITS(name, gb, num) zero_extend(name ## _cache, num)
185 # define SHOW_SBITS(name, gb, num) sign_extend(name ## _cache, num)
187 # define SHOW_UBITS(name, gb, num) NEG_USR32(name ## _cache, num)
188 # define SHOW_SBITS(name, gb, num) NEG_SSR32(name ## _cache, num)
191 #define GET_CACHE(name, gb) ((uint32_t) name ## _cache)
193 static inline int get_bits_count(const GetBitContext *s)
198 static inline void skip_bits_long(GetBitContext *s, int n)
200 #if UNCHECKED_BITSTREAM_READER
203 s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
208 * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
209 * if MSB not set it is negative
210 * @param n length in bits
212 static inline int get_xbits(GetBitContext *s, int n)
215 register int32_t cache;
218 cache = GET_CACHE(re, s);
220 LAST_SKIP_BITS(re, s, n);
222 return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
225 static inline int get_sbits(GetBitContext *s, int n)
229 av_assert2(n>0 && n<=25);
231 tmp = SHOW_SBITS(re, s, n);
232 LAST_SKIP_BITS(re, s, n);
240 static inline unsigned int get_bits(GetBitContext *s, int n)
244 av_assert2(n>0 && n<=25);
246 tmp = SHOW_UBITS(re, s, n);
247 LAST_SKIP_BITS(re, s, n);
255 static inline unsigned int show_bits(GetBitContext *s, int n)
259 av_assert2(n>0 && n<=25);
261 tmp = SHOW_UBITS(re, s, n);
265 static inline void skip_bits(GetBitContext *s, int n)
269 LAST_SKIP_BITS(re, s, n);
273 static inline unsigned int get_bits1(GetBitContext *s)
275 unsigned int index = s->index;
276 uint8_t result = s->buffer[index >> 3];
277 #ifdef BITSTREAM_READER_LE
278 result >>= index & 7;
281 result <<= index & 7;
284 #if !UNCHECKED_BITSTREAM_READER
285 if (s->index < s->size_in_bits_plus8)
293 static inline unsigned int show_bits1(GetBitContext *s)
295 return show_bits(s, 1);
298 static inline void skip_bits1(GetBitContext *s)
306 static inline unsigned int get_bits_long(GetBitContext *s, int n)
310 } else if (n <= MIN_CACHE_BITS) {
311 return get_bits(s, n);
313 #ifdef BITSTREAM_READER_LE
314 unsigned ret = get_bits(s, 16);
315 return ret | (get_bits(s, n - 16) << 16);
317 unsigned ret = get_bits(s, 16) << (n - 16);
318 return ret | get_bits(s, n - 16);
326 static inline uint64_t get_bits64(GetBitContext *s, int n)
329 return get_bits_long(s, n);
331 #ifdef BITSTREAM_READER_LE
332 uint64_t ret = get_bits_long(s, 32);
333 return ret | (uint64_t) get_bits_long(s, n - 32) << 32;
335 uint64_t ret = (uint64_t) get_bits_long(s, n - 32) << 32;
336 return ret | get_bits_long(s, 32);
342 * Read 0-32 bits as a signed integer.
344 static inline int get_sbits_long(GetBitContext *s, int n)
346 return sign_extend(get_bits_long(s, n), n);
352 static inline unsigned int show_bits_long(GetBitContext *s, int n)
354 if (n <= MIN_CACHE_BITS) {
355 return show_bits(s, n);
357 GetBitContext gb = *s;
358 return get_bits_long(&gb, n);
362 static inline int check_marker(GetBitContext *s, const char *msg)
364 int bit = get_bits1(s);
366 av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
372 * Initialize GetBitContext.
373 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes
374 * larger than the actual read bits because some optimized bitstream
375 * readers read 32 or 64 bit at once and could read over the end
376 * @param bit_size the size of the buffer in bits
377 * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
379 static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
385 if (bit_size >= INT_MAX - 7 || bit_size < 0 || !buffer) {
386 buffer_size = bit_size = 0;
388 ret = AVERROR_INVALIDDATA;
391 buffer_size = (bit_size + 7) >> 3;
394 s->size_in_bits = bit_size;
395 s->size_in_bits_plus8 = bit_size + 8;
396 s->buffer_end = buffer + buffer_size;
403 * Initialize GetBitContext.
404 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes
405 * larger than the actual read bits because some optimized bitstream
406 * readers read 32 or 64 bit at once and could read over the end
407 * @param byte_size the size of the buffer in bytes
408 * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
410 static inline int init_get_bits8(GetBitContext *s, const uint8_t *buffer,
413 if (byte_size > INT_MAX / 8 || byte_size < 0)
415 return init_get_bits(s, buffer, byte_size * 8);
418 static inline const uint8_t *align_get_bits(GetBitContext *s)
420 int n = -get_bits_count(s) & 7;
423 return s->buffer + (s->index >> 3);
426 #define init_vlc(vlc, nb_bits, nb_codes, \
427 bits, bits_wrap, bits_size, \
428 codes, codes_wrap, codes_size, \
430 ff_init_vlc_sparse(vlc, nb_bits, nb_codes, \
431 bits, bits_wrap, bits_size, \
432 codes, codes_wrap, codes_size, \
435 int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
436 const void *bits, int bits_wrap, int bits_size,
437 const void *codes, int codes_wrap, int codes_size,
438 const void *symbols, int symbols_wrap, int symbols_size,
440 void ff_free_vlc(VLC *vlc);
442 #define INIT_VLC_LE 2
443 #define INIT_VLC_USE_NEW_STATIC 4
445 #define INIT_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size) \
447 static VLC_TYPE table[static_size][2]; \
448 (vlc)->table = table; \
449 (vlc)->table_allocated = static_size; \
450 init_vlc(vlc, bits, a, b, c, d, e, f, g, INIT_VLC_USE_NEW_STATIC); \
454 * If the vlc code is invalid and max_depth=1, then no bits will be removed.
455 * If the vlc code is invalid and max_depth>1, then the number of bits removed
458 #define GET_VLC(code, name, gb, table, bits, max_depth) \
461 unsigned int index; \
463 index = SHOW_UBITS(name, gb, bits); \
464 code = table[index][0]; \
465 n = table[index][1]; \
467 if (max_depth > 1 && n < 0) { \
468 LAST_SKIP_BITS(name, gb, bits); \
469 UPDATE_CACHE(name, gb); \
473 index = SHOW_UBITS(name, gb, nb_bits) + code; \
474 code = table[index][0]; \
475 n = table[index][1]; \
476 if (max_depth > 2 && n < 0) { \
477 LAST_SKIP_BITS(name, gb, nb_bits); \
478 UPDATE_CACHE(name, gb); \
482 index = SHOW_UBITS(name, gb, nb_bits) + code; \
483 code = table[index][0]; \
484 n = table[index][1]; \
487 SKIP_BITS(name, gb, n); \
490 #define GET_RL_VLC(level, run, name, gb, table, bits, \
491 max_depth, need_update) \
494 unsigned int index; \
496 index = SHOW_UBITS(name, gb, bits); \
497 level = table[index].level; \
498 n = table[index].len; \
500 if (max_depth > 1 && n < 0) { \
501 SKIP_BITS(name, gb, bits); \
503 UPDATE_CACHE(name, gb); \
508 index = SHOW_UBITS(name, gb, nb_bits) + level; \
509 level = table[index].level; \
510 n = table[index].len; \
512 run = table[index].run; \
513 SKIP_BITS(name, gb, n); \
518 * @param bits is the number of bits which will be read at once, must be
519 * identical to nb_bits in init_vlc()
520 * @param max_depth is the number of times bits bits must be read to completely
521 * read the longest vlc code
522 * = (max_vlc_length + bits - 1) / bits
524 static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
525 int bits, int max_depth)
532 GET_VLC(code, re, s, table, bits, max_depth);
539 static inline int decode012(GetBitContext *gb)
546 return get_bits1(gb) + 1;
549 static inline int decode210(GetBitContext *gb)
554 return 2 - get_bits1(gb);
557 static inline int get_bits_left(GetBitContext *gb)
559 return gb->size_in_bits - get_bits_count(gb);
565 static inline void print_bin(int bits, int n)
569 for (i = n - 1; i >= 0; i--)
570 av_log(NULL, AV_LOG_DEBUG, "%d", (bits >> i) & 1);
571 for (i = n; i < 24; i++)
572 av_log(NULL, AV_LOG_DEBUG, " ");
575 static inline int get_bits_trace(GetBitContext *s, int n, const char *file,
576 const char *func, int line)
578 int r = get_bits(s, n);
581 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d bit @%5d in %s %s:%d\n",
582 r, n, r, get_bits_count(s) - n, file, func, line);
587 static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2],
588 int bits, int max_depth, const char *file,
589 const char *func, int line)
591 int show = show_bits(s, 24);
592 int pos = get_bits_count(s);
593 int r = get_vlc2(s, table, bits, max_depth);
594 int len = get_bits_count(s) - pos;
595 int bits2 = show >> (24 - len);
597 print_bin(bits2, len);
599 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n",
600 bits2, len, r, pos, file, func, line);
605 static inline int get_xbits_trace(GetBitContext *s, int n, const char *file,
606 const char *func, int line)
608 int show = show_bits(s, n);
609 int r = get_xbits(s, n);
612 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d xbt @%5d in %s %s:%d\n",
613 show, n, r, get_bits_count(s) - n, file, func, line);
618 #define get_bits(s, n) get_bits_trace(s , n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
619 #define get_bits1(s) get_bits_trace(s, 1, __FILE__, __PRETTY_FUNCTION__, __LINE__)
620 #define get_xbits(s, n) get_xbits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
622 #define get_vlc(s, vlc) get_vlc_trace(s, (vlc)->table, (vlc)->bits, 3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
623 #define get_vlc2(s, tab, bits, max) get_vlc_trace(s, tab, bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)
625 #define tprintf(p, ...) av_log(p, AV_LOG_DEBUG, __VA_ARGS__)
628 #define tprintf(p, ...) { }
631 #endif /* AVCODEC_GET_BITS_H */