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;
67 void * volatile init_state;
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 #if UNCHECKED_BITSTREAM_READER
127 #define OPEN_READER(name, gb) \
128 unsigned int name ## _index = (gb)->index; \
129 unsigned int av_unused name ## _cache
131 #define HAVE_BITS_REMAINING(name, gb) 1
133 #define OPEN_READER(name, gb) \
134 unsigned int name ## _index = (gb)->index; \
135 unsigned int av_unused name ## _cache = 0; \
136 unsigned int av_unused name ## _size_plus8 = (gb)->size_in_bits_plus8
138 #define HAVE_BITS_REMAINING(name, gb) name ## _index < name ## _size_plus8
141 #define CLOSE_READER(name, gb) (gb)->index = name ## _index
143 # ifdef LONG_BITSTREAM_READER
145 # define UPDATE_CACHE_LE(name, gb) name ## _cache = \
146 AV_RL64((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
148 # define UPDATE_CACHE_BE(name, gb) name ## _cache = \
149 AV_RB64((gb)->buffer + (name ## _index >> 3)) >> (32 - (name ## _index & 7))
153 # define UPDATE_CACHE_LE(name, gb) name ## _cache = \
154 AV_RL32((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
156 # define UPDATE_CACHE_BE(name, gb) name ## _cache = \
157 AV_RB32((gb)->buffer + (name ## _index >> 3)) << (name ## _index & 7)
162 #ifdef BITSTREAM_READER_LE
164 # define UPDATE_CACHE(name, gb) UPDATE_CACHE_LE(name, gb)
166 # define SKIP_CACHE(name, gb, num) name ## _cache >>= (num)
170 # define UPDATE_CACHE(name, gb) UPDATE_CACHE_BE(name, gb)
172 # define SKIP_CACHE(name, gb, num) name ## _cache <<= (num)
176 #if UNCHECKED_BITSTREAM_READER
177 # define SKIP_COUNTER(name, gb, num) name ## _index += (num)
179 # define SKIP_COUNTER(name, gb, num) \
180 name ## _index = FFMIN(name ## _size_plus8, name ## _index + (num))
183 #define SKIP_BITS(name, gb, num) \
185 SKIP_CACHE(name, gb, num); \
186 SKIP_COUNTER(name, gb, num); \
189 #define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
191 #define SHOW_UBITS_LE(name, gb, num) zero_extend(name ## _cache, num)
192 #define SHOW_SBITS_LE(name, gb, num) sign_extend(name ## _cache, num)
194 #define SHOW_UBITS_BE(name, gb, num) NEG_USR32(name ## _cache, num)
195 #define SHOW_SBITS_BE(name, gb, num) NEG_SSR32(name ## _cache, num)
197 #ifdef BITSTREAM_READER_LE
198 # define SHOW_UBITS(name, gb, num) SHOW_UBITS_LE(name, gb, num)
199 # define SHOW_SBITS(name, gb, num) SHOW_SBITS_LE(name, gb, num)
201 # define SHOW_UBITS(name, gb, num) SHOW_UBITS_BE(name, gb, num)
202 # define SHOW_SBITS(name, gb, num) SHOW_SBITS_BE(name, gb, num)
205 #define GET_CACHE(name, gb) ((uint32_t) name ## _cache)
207 static inline int get_bits_count(const GetBitContext *s)
212 static inline void skip_bits_long(GetBitContext *s, int n)
214 #if UNCHECKED_BITSTREAM_READER
217 s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
222 * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
223 * if MSB not set it is negative
224 * @param n length in bits
226 static inline int get_xbits(GetBitContext *s, int n)
229 register int32_t cache;
231 av_assert2(n>0 && n<=25);
233 cache = GET_CACHE(re, s);
235 LAST_SKIP_BITS(re, s, n);
237 return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
240 static inline int get_sbits(GetBitContext *s, int n)
244 av_assert2(n>0 && n<=25);
246 tmp = SHOW_SBITS(re, s, n);
247 LAST_SKIP_BITS(re, s, n);
255 static inline unsigned int get_bits(GetBitContext *s, int n)
259 av_assert2(n>0 && n<=25);
261 tmp = SHOW_UBITS(re, s, n);
262 LAST_SKIP_BITS(re, s, n);
267 static inline unsigned int get_bits_le(GetBitContext *s, int n)
271 av_assert2(n>0 && n<=25);
272 UPDATE_CACHE_LE(re, s);
273 tmp = SHOW_UBITS_LE(re, s, n);
274 LAST_SKIP_BITS(re, s, n);
282 static inline unsigned int show_bits(GetBitContext *s, int n)
286 av_assert2(n>0 && n<=25);
288 tmp = SHOW_UBITS(re, s, n);
292 static inline void skip_bits(GetBitContext *s, int n)
295 LAST_SKIP_BITS(re, s, n);
299 static inline unsigned int get_bits1(GetBitContext *s)
301 unsigned int index = s->index;
302 uint8_t result = s->buffer[index >> 3];
303 #ifdef BITSTREAM_READER_LE
304 result >>= index & 7;
307 result <<= index & 7;
310 #if !UNCHECKED_BITSTREAM_READER
311 if (s->index < s->size_in_bits_plus8)
319 static inline unsigned int show_bits1(GetBitContext *s)
321 return show_bits(s, 1);
324 static inline void skip_bits1(GetBitContext *s)
332 static inline unsigned int get_bits_long(GetBitContext *s, int n)
336 } else if (n <= MIN_CACHE_BITS) {
337 return get_bits(s, n);
339 #ifdef BITSTREAM_READER_LE
340 unsigned ret = get_bits(s, 16);
341 return ret | (get_bits(s, n - 16) << 16);
343 unsigned ret = get_bits(s, 16) << (n - 16);
344 return ret | get_bits(s, n - 16);
352 static inline uint64_t get_bits64(GetBitContext *s, int n)
355 return get_bits_long(s, n);
357 #ifdef BITSTREAM_READER_LE
358 uint64_t ret = get_bits_long(s, 32);
359 return ret | (uint64_t) get_bits_long(s, n - 32) << 32;
361 uint64_t ret = (uint64_t) get_bits_long(s, n - 32) << 32;
362 return ret | get_bits_long(s, 32);
368 * Read 0-32 bits as a signed integer.
370 static inline int get_sbits_long(GetBitContext *s, int n)
372 return sign_extend(get_bits_long(s, n), n);
378 static inline unsigned int show_bits_long(GetBitContext *s, int n)
380 if (n <= MIN_CACHE_BITS) {
381 return show_bits(s, n);
383 GetBitContext gb = *s;
384 return get_bits_long(&gb, n);
388 static inline int check_marker(GetBitContext *s, const char *msg)
390 int bit = get_bits1(s);
392 av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
398 * Initialize GetBitContext.
399 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes
400 * larger than the actual read bits because some optimized bitstream
401 * readers read 32 or 64 bit at once and could read over the end
402 * @param bit_size the size of the buffer in bits
403 * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
405 static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
411 if (bit_size >= INT_MAX - 7 || bit_size < 0 || !buffer) {
412 buffer_size = bit_size = 0;
414 ret = AVERROR_INVALIDDATA;
417 buffer_size = (bit_size + 7) >> 3;
420 s->size_in_bits = bit_size;
421 s->size_in_bits_plus8 = bit_size + 8;
422 s->buffer_end = buffer + buffer_size;
429 * Initialize GetBitContext.
430 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes
431 * larger than the actual read bits because some optimized bitstream
432 * readers read 32 or 64 bit at once and could read over the end
433 * @param byte_size the size of the buffer in bytes
434 * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
436 static inline int init_get_bits8(GetBitContext *s, const uint8_t *buffer,
439 if (byte_size > INT_MAX / 8 || byte_size < 0)
441 return init_get_bits(s, buffer, byte_size * 8);
444 static inline const uint8_t *align_get_bits(GetBitContext *s)
446 int n = -get_bits_count(s) & 7;
449 return s->buffer + (s->index >> 3);
452 #define init_vlc(vlc, nb_bits, nb_codes, \
453 bits, bits_wrap, bits_size, \
454 codes, codes_wrap, codes_size, \
456 ff_init_vlc_sparse(vlc, nb_bits, nb_codes, \
457 bits, bits_wrap, bits_size, \
458 codes, codes_wrap, codes_size, \
461 int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
462 const void *bits, int bits_wrap, int bits_size,
463 const void *codes, int codes_wrap, int codes_size,
464 const void *symbols, int symbols_wrap, int symbols_size,
466 void ff_free_vlc(VLC *vlc);
468 #define INIT_VLC_LE 2
469 #define INIT_VLC_USE_NEW_STATIC 4
471 #define INIT_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size) \
473 static VLC_TYPE table[static_size][2]; \
474 (vlc)->table = table; \
475 (vlc)->table_allocated = static_size; \
476 init_vlc(vlc, bits, a, b, c, d, e, f, g, INIT_VLC_USE_NEW_STATIC); \
480 * If the vlc code is invalid and max_depth=1, then no bits will be removed.
481 * If the vlc code is invalid and max_depth>1, then the number of bits removed
484 #define GET_VLC(code, name, gb, table, bits, max_depth) \
487 unsigned int index; \
489 index = SHOW_UBITS(name, gb, bits); \
490 code = table[index][0]; \
491 n = table[index][1]; \
493 if (max_depth > 1 && n < 0) { \
494 LAST_SKIP_BITS(name, gb, bits); \
495 UPDATE_CACHE(name, gb); \
499 index = SHOW_UBITS(name, gb, nb_bits) + code; \
500 code = table[index][0]; \
501 n = table[index][1]; \
502 if (max_depth > 2 && n < 0) { \
503 LAST_SKIP_BITS(name, gb, nb_bits); \
504 UPDATE_CACHE(name, gb); \
508 index = SHOW_UBITS(name, gb, nb_bits) + code; \
509 code = table[index][0]; \
510 n = table[index][1]; \
513 SKIP_BITS(name, gb, n); \
516 #define GET_RL_VLC(level, run, name, gb, table, bits, \
517 max_depth, need_update) \
520 unsigned int index; \
522 index = SHOW_UBITS(name, gb, bits); \
523 level = table[index].level; \
524 n = table[index].len; \
526 if (max_depth > 1 && n < 0) { \
527 SKIP_BITS(name, gb, bits); \
529 UPDATE_CACHE(name, gb); \
534 index = SHOW_UBITS(name, gb, nb_bits) + level; \
535 level = table[index].level; \
536 n = table[index].len; \
538 run = table[index].run; \
539 SKIP_BITS(name, gb, n); \
544 * @param bits is the number of bits which will be read at once, must be
545 * identical to nb_bits in init_vlc()
546 * @param max_depth is the number of times bits bits must be read to completely
547 * read the longest vlc code
548 * = (max_vlc_length + bits - 1) / bits
550 static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
551 int bits, int max_depth)
558 GET_VLC(code, re, s, table, bits, max_depth);
565 static inline int decode012(GetBitContext *gb)
572 return get_bits1(gb) + 1;
575 static inline int decode210(GetBitContext *gb)
580 return 2 - get_bits1(gb);
583 static inline int get_bits_left(GetBitContext *gb)
585 return gb->size_in_bits - get_bits_count(gb);
588 static inline int skip_1stop_8data_bits(GetBitContext *gb)
590 if (get_bits_left(gb) <= 0)
591 return AVERROR_INVALIDDATA;
593 while (get_bits1(gb)) {
595 if (get_bits_left(gb) <= 0)
596 return AVERROR_INVALIDDATA;
605 static inline void print_bin(int bits, int n)
609 for (i = n - 1; i >= 0; i--)
610 av_log(NULL, AV_LOG_DEBUG, "%d", (bits >> i) & 1);
611 for (i = n; i < 24; i++)
612 av_log(NULL, AV_LOG_DEBUG, " ");
615 static inline int get_bits_trace(GetBitContext *s, int n, const char *file,
616 const char *func, int line)
618 int r = get_bits(s, n);
621 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d bit @%5d in %s %s:%d\n",
622 r, n, r, get_bits_count(s) - n, file, func, line);
627 static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2],
628 int bits, int max_depth, const char *file,
629 const char *func, int line)
631 int show = show_bits(s, 24);
632 int pos = get_bits_count(s);
633 int r = get_vlc2(s, table, bits, max_depth);
634 int len = get_bits_count(s) - pos;
635 int bits2 = show >> (24 - len);
637 print_bin(bits2, len);
639 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n",
640 bits2, len, r, pos, file, func, line);
645 static inline int get_xbits_trace(GetBitContext *s, int n, const char *file,
646 const char *func, int line)
648 int show = show_bits(s, n);
649 int r = get_xbits(s, n);
652 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d xbt @%5d in %s %s:%d\n",
653 show, n, r, get_bits_count(s) - n, file, func, line);
658 #define get_bits(s, n) get_bits_trace(s , n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
659 #define get_bits1(s) get_bits_trace(s, 1, __FILE__, __PRETTY_FUNCTION__, __LINE__)
660 #define get_xbits(s, n) get_xbits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
662 #define get_vlc(s, vlc) get_vlc_trace(s, (vlc)->table, (vlc)->bits, 3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
663 #define get_vlc2(s, tab, bits, max) get_vlc_trace(s, tab, bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)
665 #define tprintf(p, ...) av_log(p, AV_LOG_DEBUG, __VA_ARGS__)
668 #define tprintf(p, ...) { }
671 #endif /* AVCODEC_GET_BITS_H */