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
32 #include "libavutil/bswap.h"
33 #include "libavutil/common.h"
34 #include "libavutil/intreadwrite.h"
35 #include "libavutil/log.h"
39 * Safe bitstream reading:
40 * optionally, the get_bits API can check to ensure that we
41 * don't read past input buffer boundaries. This is protected
42 * with CONFIG_SAFE_BITSTREAM_READER at the global level, and
43 * then below that with UNCHECKED_BITSTREAM_READER at the per-
44 * decoder level. This means that decoders that check internally
45 * can "#define UNCHECKED_BITSTREAM_READER 1" to disable
47 * Boundary checking causes a minor performance penalty so for
48 * applications that won't want/need this, it can be disabled
49 * globally using "#define CONFIG_SAFE_BITSTREAM_READER 0".
51 #ifndef UNCHECKED_BITSTREAM_READER
52 #define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
56 /* buffer, buffer_end and size_in_bits must be present and used by every reader */
57 typedef struct GetBitContext {
58 const uint8_t *buffer, *buffer_end;
61 #if !UNCHECKED_BITSTREAM_READER
62 int size_in_bits_plus8;
66 #define VLC_TYPE int16_t
70 VLC_TYPE (*table)[2]; ///< code, bits
71 int table_size, table_allocated;
74 typedef struct RL_VLC_ELEM {
80 /* Bitstream reader API docs:
82 arbitrary name which is used as prefix for the internal variables
88 load gb into local variables
90 CLOSE_READER(name, gb)
91 store local vars in gb
93 UPDATE_CACHE(name, gb)
94 refill the internal cache from the bitstream
95 after this call at least MIN_CACHE_BITS will be available,
98 will output the contents of the internal cache, next bit is MSB of 32 or 64 bit (FIXME 64bit)
100 SHOW_UBITS(name, gb, num)
101 will return the next num bits
103 SHOW_SBITS(name, gb, num)
104 will return the next num bits and do sign extension
106 SKIP_BITS(name, gb, num)
107 will skip over the next num bits
108 note, this is equivalent to SKIP_CACHE; SKIP_COUNTER
110 SKIP_CACHE(name, gb, num)
111 will remove the next num bits from the cache (note SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER)
113 SKIP_COUNTER(name, gb, num)
114 will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS)
116 LAST_SKIP_CACHE(name, gb, num)
117 will remove the next num bits from the cache if it is needed for UPDATE_CACHE otherwise it will do nothing
119 LAST_SKIP_BITS(name, gb, num)
120 is equivalent to LAST_SKIP_CACHE; SKIP_COUNTER
122 for examples see get_bits, show_bits, skip_bits, get_vlc
125 #ifdef LONG_BITSTREAM_READER
126 # define MIN_CACHE_BITS 32
128 # define MIN_CACHE_BITS 25
131 # define OPEN_READER(name, gb) \
132 unsigned int name##_index = (gb)->index; \
133 unsigned int av_unused name##_cache = 0
135 # define CLOSE_READER(name, gb) (gb)->index = name##_index
137 # ifdef ALT_BITSTREAM_READER_LE
138 # ifdef LONG_BITSTREAM_READER
139 # define UPDATE_CACHE(name, gb) \
140 name##_cache = AV_RL64((gb)->buffer+(name##_index>>3)) >> (name##_index&0x07)
142 # define UPDATE_CACHE(name, gb) \
143 name##_cache = AV_RL32((gb)->buffer+(name##_index>>3)) >> (name##_index&0x07)
146 # define SKIP_CACHE(name, gb, num) name##_cache >>= (num)
148 # ifdef LONG_BITSTREAM_READER
149 # define UPDATE_CACHE(name, gb) \
150 name##_cache = AV_RB64((gb)->buffer+(name##_index >> 3)) >> (32 - (name##_index & 0x07))
152 # define UPDATE_CACHE(name, gb) \
153 name##_cache = AV_RB32((gb)->buffer+(name##_index>>3)) << (name##_index&0x07)
156 # define SKIP_CACHE(name, gb, num) name##_cache <<= (num)
160 #if UNCHECKED_BITSTREAM_READER
161 # define SKIP_COUNTER(name, gb, num) name##_index += (num)
163 # define SKIP_COUNTER(name, gb, num) \
164 name##_index = FFMIN((gb)->size_in_bits_plus8, name##_index + (num))
167 # define SKIP_BITS(name, gb, num) do { \
168 SKIP_CACHE(name, gb, num); \
169 SKIP_COUNTER(name, gb, num); \
172 # define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
173 # define LAST_SKIP_CACHE(name, gb, num)
175 # ifdef ALT_BITSTREAM_READER_LE
176 # define SHOW_UBITS(name, gb, num) zero_extend(name##_cache, num)
178 # define SHOW_SBITS(name, gb, num) sign_extend(name##_cache, num)
180 # define SHOW_UBITS(name, gb, num) NEG_USR32(name##_cache, num)
182 # define SHOW_SBITS(name, gb, num) NEG_SSR32(name##_cache, num)
185 # define GET_CACHE(name, gb) ((uint32_t)name##_cache)
187 static inline int get_bits_count(const GetBitContext *s){
191 static inline void skip_bits_long(GetBitContext *s, int n){
192 #if UNCHECKED_BITSTREAM_READER
195 s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
200 * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
201 * if MSB not set it is negative
202 * @param n length in bits
205 static inline int get_xbits(GetBitContext *s, int n){
207 register int32_t cache;
210 cache = GET_CACHE(re, s);
212 LAST_SKIP_BITS(re, s, n);
214 return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
217 static inline int get_sbits(GetBitContext *s, int n){
221 tmp = SHOW_SBITS(re, s, n);
222 LAST_SKIP_BITS(re, s, n);
230 static inline unsigned int get_bits(GetBitContext *s, int n){
234 tmp = SHOW_UBITS(re, s, n);
235 LAST_SKIP_BITS(re, s, n);
243 static inline unsigned int show_bits(GetBitContext *s, int n){
247 tmp = SHOW_UBITS(re, s, n);
251 static inline void skip_bits(GetBitContext *s, int n){
252 //Note gcc seems to optimize this to s->index+=n for the ALT_READER :))
255 LAST_SKIP_BITS(re, s, n);
259 static inline unsigned int get_bits1(GetBitContext *s){
260 unsigned int index = s->index;
261 uint8_t result = s->buffer[index>>3];
262 #ifdef ALT_BITSTREAM_READER_LE
263 result >>= index & 7;
266 result <<= index & 7;
269 #if !UNCHECKED_BITSTREAM_READER
270 if (s->index < s->size_in_bits_plus8)
278 static inline unsigned int show_bits1(GetBitContext *s){
279 return show_bits(s, 1);
282 static inline void skip_bits1(GetBitContext *s){
289 static inline unsigned int get_bits_long(GetBitContext *s, int n){
290 if (n <= MIN_CACHE_BITS) return get_bits(s, n);
292 #ifdef ALT_BITSTREAM_READER_LE
293 int ret = get_bits(s, 16);
294 return ret | (get_bits(s, n-16) << 16);
296 int ret = get_bits(s, 16) << (n-16);
297 return ret | get_bits(s, n-16);
303 * Read 0-32 bits as a signed integer.
305 static inline int get_sbits_long(GetBitContext *s, int n) {
306 return sign_extend(get_bits_long(s, n), n);
312 static inline unsigned int show_bits_long(GetBitContext *s, int n){
313 if (n <= MIN_CACHE_BITS) return show_bits(s, n);
315 GetBitContext gb = *s;
316 return get_bits_long(&gb, n);
320 static inline int check_marker(GetBitContext *s, const char *msg)
322 int bit = get_bits1(s);
324 av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
330 * Inititalize GetBitContext.
331 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger than the actual read bits
332 * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
333 * @param bit_size the size of the buffer in bits
335 * While GetBitContext stores the buffer size, for performance reasons you are
336 * responsible for checking for the buffer end yourself (take advantage of the padding)!
338 static inline void init_get_bits(GetBitContext *s,
339 const uint8_t *buffer, int bit_size)
341 int buffer_size = (bit_size+7)>>3;
342 if (buffer_size < 0 || bit_size < 0) {
343 buffer_size = bit_size = 0;
348 s->size_in_bits = bit_size;
349 #if !UNCHECKED_BITSTREAM_READER
350 s->size_in_bits_plus8 = bit_size + 8;
352 s->buffer_end = buffer + buffer_size;
356 static inline void align_get_bits(GetBitContext *s)
358 int n = -get_bits_count(s) & 7;
359 if (n) skip_bits(s, n);
362 #define init_vlc(vlc, nb_bits, nb_codes, \
363 bits, bits_wrap, bits_size, \
364 codes, codes_wrap, codes_size, \
366 init_vlc_sparse(vlc, nb_bits, nb_codes, \
367 bits, bits_wrap, bits_size, \
368 codes, codes_wrap, codes_size, \
371 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
372 const void *bits, int bits_wrap, int bits_size,
373 const void *codes, int codes_wrap, int codes_size,
374 const void *symbols, int symbols_wrap, int symbols_size,
376 #define INIT_VLC_LE 2
377 #define INIT_VLC_USE_NEW_STATIC 4
378 void free_vlc(VLC *vlc);
380 #define INIT_VLC_STATIC(vlc, bits, a,b,c,d,e,f,g, static_size) do { \
381 static VLC_TYPE table[static_size][2]; \
382 (vlc)->table = table; \
383 (vlc)->table_allocated = static_size; \
384 init_vlc(vlc, bits, a,b,c,d,e,f,g, INIT_VLC_USE_NEW_STATIC); \
389 * If the vlc code is invalid and max_depth=1, then no bits will be removed.
390 * If the vlc code is invalid and max_depth>1, then the number of bits removed
393 #define GET_VLC(code, name, gb, table, bits, max_depth) do { \
395 unsigned int index; \
397 index = SHOW_UBITS(name, gb, bits); \
398 code = table[index][0]; \
399 n = table[index][1]; \
401 if (max_depth > 1 && n < 0) { \
402 LAST_SKIP_BITS(name, gb, bits); \
403 UPDATE_CACHE(name, gb); \
407 index = SHOW_UBITS(name, gb, nb_bits) + code; \
408 code = table[index][0]; \
409 n = table[index][1]; \
410 if (max_depth > 2 && n < 0) { \
411 LAST_SKIP_BITS(name, gb, nb_bits); \
412 UPDATE_CACHE(name, gb); \
416 index = SHOW_UBITS(name, gb, nb_bits) + code; \
417 code = table[index][0]; \
418 n = table[index][1]; \
421 SKIP_BITS(name, gb, n); \
424 #define GET_RL_VLC(level, run, name, gb, table, bits, max_depth, need_update) do { \
426 unsigned int index; \
428 index = SHOW_UBITS(name, gb, bits); \
429 level = table[index].level; \
430 n = table[index].len; \
432 if (max_depth > 1 && n < 0) { \
433 SKIP_BITS(name, gb, bits); \
435 UPDATE_CACHE(name, gb); \
440 index = SHOW_UBITS(name, gb, nb_bits) + level; \
441 level = table[index].level; \
442 n = table[index].len; \
444 run = table[index].run; \
445 SKIP_BITS(name, gb, n); \
450 * Parse a vlc code, faster than get_vlc().
451 * @param bits is the number of bits which will be read at once, must be
452 * identical to nb_bits in init_vlc()
453 * @param max_depth is the number of times bits bits must be read to completely
454 * read the longest vlc code
455 * = (max_vlc_length + bits - 1) / bits
457 static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
458 int bits, int max_depth)
465 GET_VLC(code, re, s, table, bits, max_depth);
471 static inline int decode012(GetBitContext *gb){
477 return get_bits1(gb) + 1;
480 static inline int decode210(GetBitContext *gb){
484 return 2 - get_bits1(gb);
487 static inline int get_bits_left(GetBitContext *gb)
489 return gb->size_in_bits - get_bits_count(gb);
495 static inline void print_bin(int bits, int n){
498 for (i = n-1; i >= 0; i--) {
499 av_log(NULL, AV_LOG_DEBUG, "%d", (bits>>i)&1);
501 for (i = n; i < 24; i++)
502 av_log(NULL, AV_LOG_DEBUG, " ");
505 static inline int get_bits_trace(GetBitContext *s, int n, char *file,
506 const char *func, int line){
507 int r = get_bits(s, n);
510 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d bit @%5d in %s %s:%d\n",
511 r, n, r, get_bits_count(s)-n, file, func, line);
514 static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2],
515 int bits, int max_depth, char *file,
516 const char *func, int line){
517 int show = show_bits(s, 24);
518 int pos = get_bits_count(s);
519 int r = get_vlc2(s, table, bits, max_depth);
520 int len = get_bits_count(s) - pos;
521 int bits2 = show >> (24-len);
523 print_bin(bits2, len);
525 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n",
526 bits2, len, r, pos, file, func, line);
529 static inline int get_xbits_trace(GetBitContext *s, int n, char *file,
530 const char *func, int line){
531 int show = show_bits(s, n);
532 int r = get_xbits(s, n);
535 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d xbt @%5d in %s %s:%d\n",
536 show, n, r, get_bits_count(s)-n, file, func, line);
540 #define get_bits(s, n) get_bits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
541 #define get_bits1(s) get_bits_trace(s, 1, __FILE__, __PRETTY_FUNCTION__, __LINE__)
542 #define get_xbits(s, n) get_xbits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
543 #define get_vlc(s, vlc) get_vlc_trace(s, (vlc)->table, (vlc)->bits, 3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
544 #define get_vlc2(s, tab, bits, max) get_vlc_trace(s, tab, bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)
546 #define tprintf(p, ...) av_log(p, AV_LOG_DEBUG, __VA_ARGS__)
549 #define tprintf(p, ...) {}
552 #endif /* AVCODEC_GET_BITS_H */