2 * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
4 * This file is part of Libav.
6 * Libav 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 * Libav 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 Libav; 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"
37 * Safe bitstream reading:
38 * optionally, the get_bits API can check to ensure that we
39 * don't read past input buffer boundaries. This is protected
40 * with CONFIG_SAFE_BITSTREAM_READER at the global level, and
41 * then below that with UNCHECKED_BITSTREAM_READER at the per-
42 * decoder level. This means that decoders that check internally
43 * can "#define UNCHECKED_BITSTREAM_READER 1" to disable
45 * Boundary checking causes a minor performance penalty so for
46 * applications that won't want/need this, it can be disabled
47 * globally using "#define CONFIG_SAFE_BITSTREAM_READER 0".
49 #ifndef UNCHECKED_BITSTREAM_READER
50 #define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
53 typedef struct GetBitContext {
54 const uint8_t *buffer, *buffer_end;
57 #if !UNCHECKED_BITSTREAM_READER
58 int size_in_bits_plus8;
62 #define VLC_TYPE int16_t
66 VLC_TYPE (*table)[2]; ///< code, bits
67 int table_size, table_allocated;
70 typedef struct RL_VLC_ELEM {
76 /* Bitstream reader API docs:
78 * arbitrary name which is used as prefix for the internal variables
83 * OPEN_READER(name, gb)
84 * load gb into local variables
86 * CLOSE_READER(name, gb)
87 * store local vars in gb
89 * UPDATE_CACHE(name, gb)
90 * Refill the internal cache from the bitstream.
91 * After this call at least MIN_CACHE_BITS will be available.
94 * Will output the contents of the internal cache,
95 * next bit is MSB of 32 or 64 bit (FIXME 64bit).
97 * SHOW_UBITS(name, gb, num)
98 * Will return the next num bits.
100 * SHOW_SBITS(name, gb, num)
101 * Will return the next num bits and do sign extension.
103 * SKIP_BITS(name, gb, num)
104 * Will skip over the next num bits.
105 * Note, this is equivalent to SKIP_CACHE; SKIP_COUNTER.
107 * SKIP_CACHE(name, gb, num)
108 * Will remove the next num bits from the cache (note SKIP_COUNTER
109 * MUST be called before UPDATE_CACHE / CLOSE_READER).
111 * SKIP_COUNTER(name, gb, num)
112 * Will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS).
114 * LAST_SKIP_BITS(name, gb, num)
115 * Like SKIP_BITS, to be used if next call is UPDATE_CACHE or CLOSE_READER.
117 * For examples see get_bits, show_bits, skip_bits, get_vlc.
120 #ifdef LONG_BITSTREAM_READER
121 # define MIN_CACHE_BITS 32
123 # define MIN_CACHE_BITS 25
126 #define OPEN_READER_NOSIZE(name, gb) \
127 unsigned int name ## _index = (gb)->index; \
128 unsigned int av_unused name ## _cache = 0
130 #if UNCHECKED_BITSTREAM_READER
131 #define OPEN_READER(name, gb) OPEN_READER_NOSIZE(name, gb)
133 #define BITS_AVAILABLE(name, gb) 1
135 #define OPEN_READER(name, gb) \
136 OPEN_READER_NOSIZE(name, gb); \
137 unsigned int name ## _size_plus8 = (gb)->size_in_bits_plus8
139 #define BITS_AVAILABLE(name, gb) name ## _index < name ## _size_plus8
142 #define CLOSE_READER(name, gb) (gb)->index = name ## _index
144 #ifdef BITSTREAM_READER_LE
146 # ifdef LONG_BITSTREAM_READER
147 # define UPDATE_CACHE(name, gb) name ## _cache = \
148 AV_RL64((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
150 # define UPDATE_CACHE(name, gb) name ## _cache = \
151 AV_RL32((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
154 # define SKIP_CACHE(name, gb, num) name ## _cache >>= (num)
158 # ifdef LONG_BITSTREAM_READER
159 # define UPDATE_CACHE(name, gb) name ## _cache = \
160 AV_RB64((gb)->buffer + (name ## _index >> 3)) >> (32 - (name ## _index & 7))
162 # define UPDATE_CACHE(name, gb) name ## _cache = \
163 AV_RB32((gb)->buffer + (name ## _index >> 3)) << (name ## _index & 7)
166 # define SKIP_CACHE(name, gb, num) name ## _cache <<= (num)
170 #if UNCHECKED_BITSTREAM_READER
171 # define SKIP_COUNTER(name, gb, num) name ## _index += (num)
173 # define SKIP_COUNTER(name, gb, num) \
174 name ## _index = FFMIN(name ## _size_plus8, name ## _index + (num))
177 #define SKIP_BITS(name, gb, num) \
179 SKIP_CACHE(name, gb, num); \
180 SKIP_COUNTER(name, gb, num); \
183 #define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
185 #ifdef BITSTREAM_READER_LE
186 # define SHOW_UBITS(name, gb, num) zero_extend(name ## _cache, num)
187 # define SHOW_SBITS(name, gb, num) sign_extend(name ## _cache, num)
189 # define SHOW_UBITS(name, gb, num) NEG_USR32(name ## _cache, num)
190 # define SHOW_SBITS(name, gb, num) NEG_SSR32(name ## _cache, num)
193 #define GET_CACHE(name, gb) ((uint32_t) name ## _cache)
195 static inline int get_bits_count(const GetBitContext *s)
200 static inline void skip_bits_long(GetBitContext *s, int n)
202 #if UNCHECKED_BITSTREAM_READER
205 s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
210 * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
211 * if MSB not set it is negative
212 * @param n length in bits
214 static inline int get_xbits(GetBitContext *s, int n)
217 register int32_t cache;
220 cache = GET_CACHE(re, s);
222 LAST_SKIP_BITS(re, s, n);
224 return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
227 static inline int get_sbits(GetBitContext *s, int n)
232 tmp = SHOW_SBITS(re, s, n);
233 LAST_SKIP_BITS(re, s, n);
241 static inline unsigned int get_bits(GetBitContext *s, int n)
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)
258 OPEN_READER_NOSIZE(re, s);
260 tmp = SHOW_UBITS(re, s, n);
264 static inline void skip_bits(GetBitContext *s, int n)
268 LAST_SKIP_BITS(re, s, n);
272 static inline unsigned int get_bits1(GetBitContext *s)
274 unsigned int index = s->index;
275 uint8_t result = s->buffer[index >> 3];
276 #ifdef BITSTREAM_READER_LE
277 result >>= index & 7;
280 result <<= index & 7;
283 #if !UNCHECKED_BITSTREAM_READER
284 if (s->index < s->size_in_bits_plus8)
292 static inline unsigned int show_bits1(GetBitContext *s)
294 return show_bits(s, 1);
297 static inline void skip_bits1(GetBitContext *s)
305 static inline unsigned int get_bits_long(GetBitContext *s, int n)
307 if (n <= MIN_CACHE_BITS) {
308 return get_bits(s, n);
310 #ifdef BITSTREAM_READER_LE
311 int ret = get_bits(s, 16);
312 return ret | (get_bits(s, n - 16) << 16);
314 int ret = get_bits(s, 16) << (n - 16);
315 return ret | get_bits(s, n - 16);
323 static inline uint64_t get_bits64(GetBitContext *s, int n)
326 return get_bits_long(s, n);
328 #ifdef BITSTREAM_READER_LE
329 uint64_t ret = get_bits_long(s, 32);
330 return ret | (uint64_t) get_bits_long(s, n - 32) << 32;
332 uint64_t ret = (uint64_t) get_bits_long(s, n - 32) << 32;
333 return ret | get_bits_long(s, 32);
339 * Read 0-32 bits as a signed integer.
341 static inline int get_sbits_long(GetBitContext *s, int n)
343 return sign_extend(get_bits_long(s, n), n);
349 static inline unsigned int show_bits_long(GetBitContext *s, int n)
351 if (n <= MIN_CACHE_BITS) {
352 return show_bits(s, n);
354 GetBitContext gb = *s;
355 return get_bits_long(&gb, n);
359 static inline int check_marker(GetBitContext *s, const char *msg)
361 int bit = get_bits1(s);
363 av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
369 * Initialize GetBitContext.
370 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes
371 * larger than the actual read bits because some optimized bitstream
372 * readers read 32 or 64 bit at once and could read over the end
373 * @param bit_size the size of the buffer in bits
374 * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
376 static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
382 if (bit_size > INT_MAX - 7 || bit_size < 0 || !buffer) {
385 ret = AVERROR_INVALIDDATA;
388 buffer_size = (bit_size + 7) >> 3;
391 s->size_in_bits = bit_size;
392 #if !UNCHECKED_BITSTREAM_READER
393 s->size_in_bits_plus8 = bit_size + 8;
395 s->buffer_end = buffer + buffer_size;
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 byte_size the size of the buffer in bytes
407 * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
409 static inline int init_get_bits8(GetBitContext *s, const uint8_t *buffer,
412 if (byte_size > INT_MAX / 8)
413 return AVERROR_INVALIDDATA;
414 return init_get_bits(s, buffer, byte_size * 8);
417 static inline const uint8_t *align_get_bits(GetBitContext *s)
419 int n = -get_bits_count(s) & 7;
422 return s->buffer + (s->index >> 3);
425 #define init_vlc(vlc, nb_bits, nb_codes, \
426 bits, bits_wrap, bits_size, \
427 codes, codes_wrap, codes_size, \
429 ff_init_vlc_sparse(vlc, nb_bits, nb_codes, \
430 bits, bits_wrap, bits_size, \
431 codes, codes_wrap, codes_size, \
434 int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
435 const void *bits, int bits_wrap, int bits_size,
436 const void *codes, int codes_wrap, int codes_size,
437 const void *symbols, int symbols_wrap, int symbols_size,
439 void ff_free_vlc(VLC *vlc);
441 #define INIT_VLC_LE 2
442 #define INIT_VLC_USE_NEW_STATIC 4
444 #define INIT_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size) \
446 static VLC_TYPE table[static_size][2]; \
447 (vlc)->table = table; \
448 (vlc)->table_allocated = static_size; \
449 init_vlc(vlc, bits, a, b, c, d, e, f, g, INIT_VLC_USE_NEW_STATIC); \
453 * If the vlc code is invalid and max_depth=1, then no bits will be removed.
454 * If the vlc code is invalid and max_depth>1, then the number of bits removed
457 #define GET_VLC(code, name, gb, table, bits, max_depth) \
460 unsigned int index; \
462 index = SHOW_UBITS(name, gb, bits); \
463 code = table[index][0]; \
464 n = table[index][1]; \
466 if (max_depth > 1 && n < 0) { \
467 LAST_SKIP_BITS(name, gb, bits); \
468 UPDATE_CACHE(name, gb); \
472 index = SHOW_UBITS(name, gb, nb_bits) + code; \
473 code = table[index][0]; \
474 n = table[index][1]; \
475 if (max_depth > 2 && n < 0) { \
476 LAST_SKIP_BITS(name, gb, nb_bits); \
477 UPDATE_CACHE(name, gb); \
481 index = SHOW_UBITS(name, gb, nb_bits) + code; \
482 code = table[index][0]; \
483 n = table[index][1]; \
486 SKIP_BITS(name, gb, n); \
489 #define GET_RL_VLC(level, run, name, gb, table, bits, \
490 max_depth, need_update) \
493 unsigned int index; \
495 index = SHOW_UBITS(name, gb, bits); \
496 level = table[index].level; \
497 n = table[index].len; \
499 if (max_depth > 1 && n < 0) { \
500 SKIP_BITS(name, gb, bits); \
502 UPDATE_CACHE(name, gb); \
507 index = SHOW_UBITS(name, gb, nb_bits) + level; \
508 level = table[index].level; \
509 n = table[index].len; \
511 run = table[index].run; \
512 SKIP_BITS(name, gb, n); \
517 * @param bits is the number of bits which will be read at once, must be
518 * identical to nb_bits in init_vlc()
519 * @param max_depth is the number of times bits bits must be read to completely
520 * read the longest vlc code
521 * = (max_vlc_length + bits - 1) / bits
523 static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
524 int bits, int max_depth)
531 GET_VLC(code, re, s, table, bits, max_depth);
538 static inline int decode012(GetBitContext *gb)
545 return get_bits1(gb) + 1;
548 static inline int decode210(GetBitContext *gb)
553 return 2 - get_bits1(gb);
556 static inline int get_bits_left(GetBitContext *gb)
558 return gb->size_in_bits - get_bits_count(gb);
564 static inline void print_bin(int bits, int n)
568 for (i = n - 1; i >= 0; i--)
569 av_log(NULL, AV_LOG_DEBUG, "%d", (bits >> i) & 1);
570 for (i = n; i < 24; i++)
571 av_log(NULL, AV_LOG_DEBUG, " ");
574 static inline int get_bits_trace(GetBitContext *s, int n, const char *file,
575 const char *func, int line)
577 int r = get_bits(s, n);
580 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d bit @%5d in %s %s:%d\n",
581 r, n, r, get_bits_count(s) - n, file, func, line);
586 static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2],
587 int bits, int max_depth, const char *file,
588 const char *func, int line)
590 int show = show_bits(s, 24);
591 int pos = get_bits_count(s);
592 int r = get_vlc2(s, table, bits, max_depth);
593 int len = get_bits_count(s) - pos;
594 int bits2 = show >> (24 - len);
596 print_bin(bits2, len);
598 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n",
599 bits2, len, r, pos, file, func, line);
604 static inline int get_xbits_trace(GetBitContext *s, int n, const char *file,
605 const char *func, int line)
607 int show = show_bits(s, n);
608 int r = get_xbits(s, n);
611 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d xbt @%5d in %s %s:%d\n",
612 show, n, r, get_bits_count(s) - n, file, func, line);
617 #define get_bits(s, n) get_bits_trace(s , n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
618 #define get_bits1(s) get_bits_trace(s, 1, __FILE__, __PRETTY_FUNCTION__, __LINE__)
619 #define get_xbits(s, n) get_xbits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
621 #define get_vlc(s, vlc) get_vlc_trace(s, (vlc)->table, (vlc)->bits, 3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
622 #define get_vlc2(s, tab, bits, max) get_vlc_trace(s, tab, bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)
625 #endif /* AVCODEC_GET_BITS_H */