Line data Source code
1 : /*
2 : * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
3 : *
4 : * This file is part of FFmpeg.
5 : *
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.
10 : *
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.
15 : *
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
19 : */
20 :
21 : /**
22 : * @file
23 : * bitstream reader API header.
24 : */
25 :
26 : #ifndef AVCODEC_GET_BITS_H
27 : #define AVCODEC_GET_BITS_H
28 :
29 : #include <stdint.h>
30 :
31 : #include "libavutil/common.h"
32 : #include "libavutil/intreadwrite.h"
33 : #include "libavutil/log.h"
34 : #include "libavutil/avassert.h"
35 : #include "avcodec.h"
36 : #include "mathops.h"
37 : #include "vlc.h"
38 :
39 : /*
40 : * Safe bitstream reading:
41 : * optionally, the get_bits API can check to ensure that we
42 : * don't read past input buffer boundaries. This is protected
43 : * with CONFIG_SAFE_BITSTREAM_READER at the global level, and
44 : * then below that with UNCHECKED_BITSTREAM_READER at the per-
45 : * decoder level. This means that decoders that check internally
46 : * can "#define UNCHECKED_BITSTREAM_READER 1" to disable
47 : * overread checks.
48 : * Boundary checking causes a minor performance penalty so for
49 : * applications that won't want/need this, it can be disabled
50 : * globally using "#define CONFIG_SAFE_BITSTREAM_READER 0".
51 : */
52 : #ifndef UNCHECKED_BITSTREAM_READER
53 : #define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
54 : #endif
55 :
56 : typedef struct GetBitContext {
57 : const uint8_t *buffer, *buffer_end;
58 : int index;
59 : int size_in_bits;
60 : int size_in_bits_plus8;
61 : } GetBitContext;
62 :
63 : /* Bitstream reader API docs:
64 : * name
65 : * arbitrary name which is used as prefix for the internal variables
66 : *
67 : * gb
68 : * getbitcontext
69 : *
70 : * OPEN_READER(name, gb)
71 : * load gb into local variables
72 : *
73 : * CLOSE_READER(name, gb)
74 : * store local vars in gb
75 : *
76 : * UPDATE_CACHE(name, gb)
77 : * Refill the internal cache from the bitstream.
78 : * After this call at least MIN_CACHE_BITS will be available.
79 : *
80 : * GET_CACHE(name, gb)
81 : * Will output the contents of the internal cache,
82 : * next bit is MSB of 32 or 64 bits (FIXME 64 bits).
83 : *
84 : * SHOW_UBITS(name, gb, num)
85 : * Will return the next num bits.
86 : *
87 : * SHOW_SBITS(name, gb, num)
88 : * Will return the next num bits and do sign extension.
89 : *
90 : * SKIP_BITS(name, gb, num)
91 : * Will skip over the next num bits.
92 : * Note, this is equivalent to SKIP_CACHE; SKIP_COUNTER.
93 : *
94 : * SKIP_CACHE(name, gb, num)
95 : * Will remove the next num bits from the cache (note SKIP_COUNTER
96 : * MUST be called before UPDATE_CACHE / CLOSE_READER).
97 : *
98 : * SKIP_COUNTER(name, gb, num)
99 : * Will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS).
100 : *
101 : * LAST_SKIP_BITS(name, gb, num)
102 : * Like SKIP_BITS, to be used if next call is UPDATE_CACHE or CLOSE_READER.
103 : *
104 : * BITS_LEFT(name, gb)
105 : * Return the number of bits left
106 : *
107 : * For examples see get_bits, show_bits, skip_bits, get_vlc.
108 : */
109 :
110 : #ifdef LONG_BITSTREAM_READER
111 : # define MIN_CACHE_BITS 32
112 : #else
113 : # define MIN_CACHE_BITS 25
114 : #endif
115 :
116 : #define OPEN_READER_NOSIZE(name, gb) \
117 : unsigned int name ## _index = (gb)->index; \
118 : unsigned int av_unused name ## _cache
119 :
120 : #if UNCHECKED_BITSTREAM_READER
121 : #define OPEN_READER(name, gb) OPEN_READER_NOSIZE(name, gb)
122 :
123 : #define BITS_AVAILABLE(name, gb) 1
124 : #else
125 : #define OPEN_READER(name, gb) \
126 : OPEN_READER_NOSIZE(name, gb); \
127 : unsigned int name ## _size_plus8 = (gb)->size_in_bits_plus8
128 :
129 : #define BITS_AVAILABLE(name, gb) name ## _index < name ## _size_plus8
130 : #endif
131 :
132 : #define CLOSE_READER(name, gb) (gb)->index = name ## _index
133 :
134 : # ifdef LONG_BITSTREAM_READER
135 :
136 : # define UPDATE_CACHE_LE(name, gb) name ## _cache = \
137 : AV_RL64((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
138 :
139 : # define UPDATE_CACHE_BE(name, gb) name ## _cache = \
140 : AV_RB64((gb)->buffer + (name ## _index >> 3)) >> (32 - (name ## _index & 7))
141 :
142 : #else
143 :
144 : # define UPDATE_CACHE_LE(name, gb) name ## _cache = \
145 : AV_RL32((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
146 :
147 : # define UPDATE_CACHE_BE(name, gb) name ## _cache = \
148 : AV_RB32((gb)->buffer + (name ## _index >> 3)) << (name ## _index & 7)
149 :
150 : #endif
151 :
152 :
153 : #ifdef BITSTREAM_READER_LE
154 :
155 : # define UPDATE_CACHE(name, gb) UPDATE_CACHE_LE(name, gb)
156 :
157 : # define SKIP_CACHE(name, gb, num) name ## _cache >>= (num)
158 :
159 : #else
160 :
161 : # define UPDATE_CACHE(name, gb) UPDATE_CACHE_BE(name, gb)
162 :
163 : # define SKIP_CACHE(name, gb, num) name ## _cache <<= (num)
164 :
165 : #endif
166 :
167 : #if UNCHECKED_BITSTREAM_READER
168 : # define SKIP_COUNTER(name, gb, num) name ## _index += (num)
169 : #else
170 : # define SKIP_COUNTER(name, gb, num) \
171 : name ## _index = FFMIN(name ## _size_plus8, name ## _index + (num))
172 : #endif
173 :
174 : #define BITS_LEFT(name, gb) ((int)((gb)->size_in_bits - name ## _index))
175 :
176 : #define SKIP_BITS(name, gb, num) \
177 : do { \
178 : SKIP_CACHE(name, gb, num); \
179 : SKIP_COUNTER(name, gb, num); \
180 : } while (0)
181 :
182 : #define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
183 :
184 : #define SHOW_UBITS_LE(name, gb, num) zero_extend(name ## _cache, num)
185 : #define SHOW_SBITS_LE(name, gb, num) sign_extend(name ## _cache, num)
186 :
187 : #define SHOW_UBITS_BE(name, gb, num) NEG_USR32(name ## _cache, num)
188 : #define SHOW_SBITS_BE(name, gb, num) NEG_SSR32(name ## _cache, num)
189 :
190 : #ifdef BITSTREAM_READER_LE
191 : # define SHOW_UBITS(name, gb, num) SHOW_UBITS_LE(name, gb, num)
192 : # define SHOW_SBITS(name, gb, num) SHOW_SBITS_LE(name, gb, num)
193 : #else
194 : # define SHOW_UBITS(name, gb, num) SHOW_UBITS_BE(name, gb, num)
195 : # define SHOW_SBITS(name, gb, num) SHOW_SBITS_BE(name, gb, num)
196 : #endif
197 :
198 : #define GET_CACHE(name, gb) ((uint32_t) name ## _cache)
199 :
200 305304876 : static inline int get_bits_count(const GetBitContext *s)
201 : {
202 305304876 : return s->index;
203 : }
204 :
205 : /**
206 : * Skips the specified number of bits.
207 : * @param n the number of bits to skip,
208 : * For the UNCHECKED_BITSTREAM_READER this must not cause the distance
209 : * from the start to overflow int32_t. Staying within the bitstream + padding
210 : * is sufficient, too.
211 : */
212 3207671 : static inline void skip_bits_long(GetBitContext *s, int n)
213 : {
214 : #if UNCHECKED_BITSTREAM_READER
215 2599651 : s->index += n;
216 : #else
217 608020 : s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
218 : #endif
219 3207671 : }
220 :
221 : /**
222 : * Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB).
223 : * if MSB not set it is negative
224 : * @param n length in bits
225 : */
226 26544802 : static inline int get_xbits(GetBitContext *s, int n)
227 : {
228 : register int sign;
229 : register int32_t cache;
230 26544802 : OPEN_READER(re, s);
231 : av_assert2(n>0 && n<=25);
232 26544802 : UPDATE_CACHE(re, s);
233 26544802 : cache = GET_CACHE(re, s);
234 26544802 : sign = ~cache >> 31;
235 26544802 : LAST_SKIP_BITS(re, s, n);
236 26544802 : CLOSE_READER(re, s);
237 26544802 : return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
238 : }
239 :
240 336 : static inline int get_xbits_le(GetBitContext *s, int n)
241 : {
242 : register int sign;
243 : register int32_t cache;
244 336 : OPEN_READER(re, s);
245 : av_assert2(n>0 && n<=25);
246 336 : UPDATE_CACHE_LE(re, s);
247 336 : cache = GET_CACHE(re, s);
248 336 : sign = sign_extend(~cache, n) >> 31;
249 336 : LAST_SKIP_BITS(re, s, n);
250 336 : CLOSE_READER(re, s);
251 336 : return (zero_extend(sign ^ cache, n) ^ sign) - sign;
252 : }
253 :
254 15743816 : static inline int get_sbits(GetBitContext *s, int n)
255 : {
256 : register int tmp;
257 15743816 : OPEN_READER(re, s);
258 : av_assert2(n>0 && n<=25);
259 15743816 : UPDATE_CACHE(re, s);
260 15743816 : tmp = SHOW_SBITS(re, s, n);
261 15743816 : LAST_SKIP_BITS(re, s, n);
262 15743816 : CLOSE_READER(re, s);
263 15743816 : return tmp;
264 : }
265 :
266 : /**
267 : * Read 1-25 bits.
268 : */
269 267008679 : static inline unsigned int get_bits(GetBitContext *s, int n)
270 : {
271 : register int tmp;
272 267008679 : OPEN_READER(re, s);
273 : av_assert2(n>0 && n<=25);
274 267008679 : UPDATE_CACHE(re, s);
275 267008679 : tmp = SHOW_UBITS(re, s, n);
276 267008679 : LAST_SKIP_BITS(re, s, n);
277 267008679 : CLOSE_READER(re, s);
278 267008679 : return tmp;
279 : }
280 :
281 : /**
282 : * Read 0-25 bits.
283 : */
284 25594177 : static av_always_inline int get_bitsz(GetBitContext *s, int n)
285 : {
286 25594177 : return n ? get_bits(s, n) : 0;
287 : }
288 :
289 0 : static inline unsigned int get_bits_le(GetBitContext *s, int n)
290 : {
291 : register int tmp;
292 0 : OPEN_READER(re, s);
293 : av_assert2(n>0 && n<=25);
294 0 : UPDATE_CACHE_LE(re, s);
295 0 : tmp = SHOW_UBITS_LE(re, s, n);
296 0 : LAST_SKIP_BITS(re, s, n);
297 0 : CLOSE_READER(re, s);
298 0 : return tmp;
299 : }
300 :
301 : /**
302 : * Show 1-25 bits.
303 : */
304 110551308 : static inline unsigned int show_bits(GetBitContext *s, int n)
305 : {
306 : register int tmp;
307 110551308 : OPEN_READER_NOSIZE(re, s);
308 : av_assert2(n>0 && n<=25);
309 110551308 : UPDATE_CACHE(re, s);
310 110551308 : tmp = SHOW_UBITS(re, s, n);
311 110551308 : return tmp;
312 : }
313 :
314 108728485 : static inline void skip_bits(GetBitContext *s, int n)
315 : {
316 108728485 : OPEN_READER(re, s);
317 108728485 : LAST_SKIP_BITS(re, s, n);
318 108728485 : CLOSE_READER(re, s);
319 108728485 : }
320 :
321 406314738 : static inline unsigned int get_bits1(GetBitContext *s)
322 : {
323 406314738 : unsigned int index = s->index;
324 406314738 : uint8_t result = s->buffer[index >> 3];
325 : #ifdef BITSTREAM_READER_LE
326 260760525 : result >>= index & 7;
327 260760525 : result &= 1;
328 : #else
329 145554213 : result <<= index & 7;
330 145554213 : result >>= 8 - 1;
331 : #endif
332 : #if !UNCHECKED_BITSTREAM_READER
333 371207002 : if (s->index < s->size_in_bits_plus8)
334 : #endif
335 406299526 : index++;
336 406314738 : s->index = index;
337 :
338 406314738 : return result;
339 : }
340 :
341 513 : static inline unsigned int show_bits1(GetBitContext *s)
342 : {
343 513 : return show_bits(s, 1);
344 : }
345 :
346 226540 : static inline void skip_bits1(GetBitContext *s)
347 : {
348 226540 : skip_bits(s, 1);
349 226540 : }
350 :
351 : /**
352 : * Read 0-32 bits.
353 : */
354 25705691 : static inline unsigned int get_bits_long(GetBitContext *s, int n)
355 : {
356 : av_assert2(n>=0 && n<=32);
357 25705691 : if (!n) {
358 240222 : return 0;
359 25465469 : } else if (n <= MIN_CACHE_BITS) {
360 22490570 : return get_bits(s, n);
361 : } else {
362 : #ifdef BITSTREAM_READER_LE
363 2118 : unsigned ret = get_bits(s, 16);
364 2118 : return ret | (get_bits(s, n - 16) << 16);
365 : #else
366 2972781 : unsigned ret = get_bits(s, 16) << (n - 16);
367 2972781 : return ret | get_bits(s, n - 16);
368 : #endif
369 : }
370 : }
371 :
372 : /**
373 : * Read 0-64 bits.
374 : */
375 78 : static inline uint64_t get_bits64(GetBitContext *s, int n)
376 : {
377 78 : if (n <= 32) {
378 0 : return get_bits_long(s, n);
379 : } else {
380 : #ifdef BITSTREAM_READER_LE
381 23 : uint64_t ret = get_bits_long(s, 32);
382 23 : return ret | (uint64_t) get_bits_long(s, n - 32) << 32;
383 : #else
384 55 : uint64_t ret = (uint64_t) get_bits_long(s, n - 32) << 32;
385 55 : return ret | get_bits_long(s, 32);
386 : #endif
387 : }
388 : }
389 :
390 : /**
391 : * Read 0-32 bits as a signed integer.
392 : */
393 4743792 : static inline int get_sbits_long(GetBitContext *s, int n)
394 : {
395 : // sign_extend(x, 0) is undefined
396 4743792 : if (!n)
397 0 : return 0;
398 :
399 4743792 : return sign_extend(get_bits_long(s, n), n);
400 : }
401 :
402 : /**
403 : * Show 0-32 bits.
404 : */
405 2902240 : static inline unsigned int show_bits_long(GetBitContext *s, int n)
406 : {
407 2902240 : if (n <= MIN_CACHE_BITS) {
408 24639 : return show_bits(s, n);
409 : } else {
410 2877601 : GetBitContext gb = *s;
411 2877601 : return get_bits_long(&gb, n);
412 : }
413 : }
414 :
415 23452 : static inline int check_marker(void *logctx, GetBitContext *s, const char *msg)
416 : {
417 23452 : int bit = get_bits1(s);
418 23452 : if (!bit)
419 0 : av_log(logctx, AV_LOG_INFO, "Marker bit missing at %d of %d %s\n",
420 0 : get_bits_count(s) - 1, s->size_in_bits, msg);
421 :
422 23452 : return bit;
423 : }
424 :
425 : /**
426 : * Initialize GetBitContext.
427 : * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
428 : * larger than the actual read bits because some optimized bitstream
429 : * readers read 32 or 64 bit at once and could read over the end
430 : * @param bit_size the size of the buffer in bits
431 : * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
432 : */
433 10188320 : static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
434 : int bit_size)
435 : {
436 : int buffer_size;
437 10188320 : int ret = 0;
438 :
439 10188320 : if (bit_size >= INT_MAX - FFMAX(7, AV_INPUT_BUFFER_PADDING_SIZE*8) || bit_size < 0 || !buffer) {
440 12 : bit_size = 0;
441 12 : buffer = NULL;
442 12 : ret = AVERROR_INVALIDDATA;
443 : }
444 :
445 10188320 : buffer_size = (bit_size + 7) >> 3;
446 :
447 10188320 : s->buffer = buffer;
448 10188320 : s->size_in_bits = bit_size;
449 10188320 : s->size_in_bits_plus8 = bit_size + 8;
450 10188320 : s->buffer_end = buffer + buffer_size;
451 10188320 : s->index = 0;
452 :
453 10188320 : return ret;
454 : }
455 :
456 : /**
457 : * Initialize GetBitContext.
458 : * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes
459 : * larger than the actual read bits because some optimized bitstream
460 : * readers read 32 or 64 bit at once and could read over the end
461 : * @param byte_size the size of the buffer in bytes
462 : * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
463 : */
464 260782 : static inline int init_get_bits8(GetBitContext *s, const uint8_t *buffer,
465 : int byte_size)
466 : {
467 260782 : if (byte_size > INT_MAX / 8 || byte_size < 0)
468 0 : byte_size = -1;
469 260782 : return init_get_bits(s, buffer, byte_size * 8);
470 : }
471 :
472 234578 : static inline const uint8_t *align_get_bits(GetBitContext *s)
473 : {
474 234578 : int n = -get_bits_count(s) & 7;
475 234578 : if (n)
476 86754 : skip_bits(s, n);
477 234578 : return s->buffer + (s->index >> 3);
478 : }
479 :
480 : /**
481 : * If the vlc code is invalid and max_depth=1, then no bits will be removed.
482 : * If the vlc code is invalid and max_depth>1, then the number of bits removed
483 : * is undefined.
484 : */
485 : #define GET_VLC(code, name, gb, table, bits, max_depth) \
486 : do { \
487 : int n, nb_bits; \
488 : unsigned int index; \
489 : \
490 : index = SHOW_UBITS(name, gb, bits); \
491 : code = table[index][0]; \
492 : n = table[index][1]; \
493 : \
494 : if (max_depth > 1 && n < 0) { \
495 : LAST_SKIP_BITS(name, gb, bits); \
496 : UPDATE_CACHE(name, gb); \
497 : \
498 : nb_bits = -n; \
499 : \
500 : index = SHOW_UBITS(name, gb, nb_bits) + code; \
501 : code = table[index][0]; \
502 : n = table[index][1]; \
503 : if (max_depth > 2 && n < 0) { \
504 : LAST_SKIP_BITS(name, gb, nb_bits); \
505 : UPDATE_CACHE(name, gb); \
506 : \
507 : nb_bits = -n; \
508 : \
509 : index = SHOW_UBITS(name, gb, nb_bits) + code; \
510 : code = table[index][0]; \
511 : n = table[index][1]; \
512 : } \
513 : } \
514 : SKIP_BITS(name, gb, n); \
515 : } while (0)
516 :
517 : #define GET_RL_VLC(level, run, name, gb, table, bits, \
518 : max_depth, need_update) \
519 : do { \
520 : int n, nb_bits; \
521 : unsigned int index; \
522 : \
523 : index = SHOW_UBITS(name, gb, bits); \
524 : level = table[index].level; \
525 : n = table[index].len; \
526 : \
527 : if (max_depth > 1 && n < 0) { \
528 : SKIP_BITS(name, gb, bits); \
529 : if (need_update) { \
530 : UPDATE_CACHE(name, gb); \
531 : } \
532 : \
533 : nb_bits = -n; \
534 : \
535 : index = SHOW_UBITS(name, gb, nb_bits) + level; \
536 : level = table[index].level; \
537 : n = table[index].len; \
538 : if (max_depth > 2 && n < 0) { \
539 : LAST_SKIP_BITS(name, gb, nb_bits); \
540 : if (need_update) { \
541 : UPDATE_CACHE(name, gb); \
542 : } \
543 : nb_bits = -n; \
544 : \
545 : index = SHOW_UBITS(name, gb, nb_bits) + level; \
546 : level = table[index].level; \
547 : n = table[index].len; \
548 : } \
549 : } \
550 : run = table[index].run; \
551 : SKIP_BITS(name, gb, n); \
552 : } while (0)
553 :
554 : /**
555 : * Parse a vlc code.
556 : * @param bits is the number of bits which will be read at once, must be
557 : * identical to nb_bits in init_vlc()
558 : * @param max_depth is the number of times bits bits must be read to completely
559 : * read the longest vlc code
560 : * = (max_vlc_length + bits - 1) / bits
561 : * @returns the code parsed or -1 if no vlc matches
562 : */
563 350701301 : static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
564 : int bits, int max_depth)
565 : {
566 : int code;
567 :
568 350701301 : OPEN_READER(re, s);
569 350701301 : UPDATE_CACHE(re, s);
570 :
571 350701301 : GET_VLC(code, re, s, table, bits, max_depth);
572 :
573 350701301 : CLOSE_READER(re, s);
574 :
575 350701301 : return code;
576 : }
577 :
578 364269 : static inline int decode012(GetBitContext *gb)
579 : {
580 : int n;
581 364269 : n = get_bits1(gb);
582 364269 : if (n == 0)
583 257232 : return 0;
584 : else
585 107037 : return get_bits1(gb) + 1;
586 : }
587 :
588 170863 : static inline int decode210(GetBitContext *gb)
589 : {
590 170863 : if (get_bits1(gb))
591 126404 : return 0;
592 : else
593 44459 : return 2 - get_bits1(gb);
594 : }
595 :
596 271304234 : static inline int get_bits_left(GetBitContext *gb)
597 : {
598 271304234 : return gb->size_in_bits - get_bits_count(gb);
599 : }
600 :
601 117777 : static inline int skip_1stop_8data_bits(GetBitContext *gb)
602 : {
603 117777 : if (get_bits_left(gb) <= 0)
604 0 : return AVERROR_INVALIDDATA;
605 :
606 237111 : while (get_bits1(gb)) {
607 1557 : skip_bits(gb, 8);
608 1557 : if (get_bits_left(gb) <= 0)
609 0 : return AVERROR_INVALIDDATA;
610 : }
611 :
612 117777 : return 0;
613 : }
614 :
615 : #endif /* AVCODEC_GET_BITS_H */
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