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
32 #include "libavutil/bswap.h"
33 #include "libavutil/common.h"
34 #include "libavutil/intreadwrite.h"
35 #include "libavutil/log.h"
38 #if defined(ALT_BITSTREAM_READER_LE) && !defined(ALT_BITSTREAM_READER)
39 # define ALT_BITSTREAM_READER
42 #if !defined(A32_BITSTREAM_READER) && !defined(ALT_BITSTREAM_READER)
43 # if ARCH_ARM && !HAVE_FAST_UNALIGNED
44 # define A32_BITSTREAM_READER
46 # define ALT_BITSTREAM_READER
47 //#define A32_BITSTREAM_READER
52 /* buffer, buffer_end and size_in_bits must be present and used by every reader */
53 typedef struct GetBitContext {
54 const uint8_t *buffer, *buffer_end;
55 #ifdef ALT_BITSTREAM_READER
57 #elif defined A32_BITSTREAM_READER
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 loads gb into local variables
90 CLOSE_READER(name, gb)
91 stores local vars in gb
93 UPDATE_CACHE(name, gb)
94 refills 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 ALT_BITSTREAM_READER
126 # define MIN_CACHE_BITS 25
128 # define OPEN_READER(name, gb)\
129 unsigned int name##_index= (gb)->index;\
132 # define CLOSE_READER(name, gb)\
133 (gb)->index= name##_index
135 # ifdef ALT_BITSTREAM_READER_LE
136 # define UPDATE_CACHE(name, gb)\
137 name##_cache= AV_RL32( ((const uint8_t *)(gb)->buffer)+(name##_index>>3) ) >> (name##_index&0x07)
139 # define SKIP_CACHE(name, gb, num)\
140 name##_cache >>= (num)
142 # define UPDATE_CACHE(name, gb)\
143 name##_cache= AV_RB32( ((const uint8_t *)(gb)->buffer)+(name##_index>>3) ) << (name##_index&0x07)
145 # define SKIP_CACHE(name, gb, num)\
146 name##_cache <<= (num)
150 # define SKIP_COUNTER(name, gb, num)\
151 name##_index += (num)
153 # define SKIP_BITS(name, gb, num)\
155 SKIP_CACHE(name, gb, num);\
156 SKIP_COUNTER(name, gb, num);\
159 # define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
160 # define LAST_SKIP_CACHE(name, gb, num)
162 # ifdef ALT_BITSTREAM_READER_LE
163 # define SHOW_UBITS(name, gb, num)\
164 zero_extend(name##_cache, num)
166 # define SHOW_SBITS(name, gb, num)\
167 sign_extend(name##_cache, num)
169 # define SHOW_UBITS(name, gb, num)\
170 NEG_USR32(name##_cache, num)
172 # define SHOW_SBITS(name, gb, num)\
173 NEG_SSR32(name##_cache, num)
176 # define GET_CACHE(name, gb)\
177 ((uint32_t)name##_cache)
179 static inline int get_bits_count(const GetBitContext *s){
183 static inline void skip_bits_long(GetBitContext *s, int n){
187 #elif defined A32_BITSTREAM_READER
189 # define MIN_CACHE_BITS 32
191 # define OPEN_READER(name, gb)\
192 int name##_bit_count=(gb)->bit_count;\
193 uint32_t name##_cache0= (gb)->cache0;\
194 uint32_t name##_cache1= (gb)->cache1;\
195 uint32_t * name##_buffer_ptr=(gb)->buffer_ptr
197 # define CLOSE_READER(name, gb) do {\
198 (gb)->bit_count= name##_bit_count;\
199 (gb)->cache0= name##_cache0;\
200 (gb)->cache1= name##_cache1;\
201 (gb)->buffer_ptr= name##_buffer_ptr;\
204 # define UPDATE_CACHE(name, gb) do {\
205 if(name##_bit_count > 0){\
206 const uint32_t next= av_be2ne32( *name##_buffer_ptr );\
207 name##_cache0 |= NEG_USR32(next,name##_bit_count);\
208 name##_cache1 |= next<<name##_bit_count;\
209 name##_buffer_ptr++;\
210 name##_bit_count-= 32;\
215 # define SKIP_CACHE(name, gb, num)\
217 "shldl %2, %1, %0 \n\t"\
219 : "+r" (name##_cache0), "+r" (name##_cache1)\
220 : "Ic" ((uint8_t)(num))\
223 # define SKIP_CACHE(name, gb, num) do {\
224 name##_cache0 <<= (num);\
225 name##_cache0 |= NEG_USR32(name##_cache1,num);\
226 name##_cache1 <<= (num);\
230 # define SKIP_COUNTER(name, gb, num)\
231 name##_bit_count += (num)
233 # define SKIP_BITS(name, gb, num)\
235 SKIP_CACHE(name, gb, num);\
236 SKIP_COUNTER(name, gb, num);\
239 # define LAST_SKIP_BITS(name, gb, num) SKIP_BITS(name, gb, num)
240 # define LAST_SKIP_CACHE(name, gb, num) SKIP_CACHE(name, gb, num)
242 # define SHOW_UBITS(name, gb, num)\
243 NEG_USR32(name##_cache0, num)
245 # define SHOW_SBITS(name, gb, num)\
246 NEG_SSR32(name##_cache0, num)
248 # define GET_CACHE(name, gb)\
251 static inline int get_bits_count(const GetBitContext *s){
252 return ((uint8_t*)s->buffer_ptr - s->buffer)*8 - 32 + s->bit_count;
255 static inline void skip_bits_long(GetBitContext *s, int n){
258 re_buffer_ptr += re_bit_count>>5;
260 re_cache0 = av_be2ne32( re_buffer_ptr[-1] ) << re_bit_count;
269 * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
270 * if MSB not set it is negative
271 * @param n length in bits
274 static inline int get_xbits(GetBitContext *s, int n){
276 register int32_t cache;
279 cache = GET_CACHE(re,s);
281 LAST_SKIP_BITS(re, s, n);
283 return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
286 static inline int get_sbits(GetBitContext *s, int n){
290 tmp= SHOW_SBITS(re, s, n);
291 LAST_SKIP_BITS(re, s, n);
299 static inline unsigned int get_bits(GetBitContext *s, int n){
303 tmp= SHOW_UBITS(re, s, n);
304 LAST_SKIP_BITS(re, s, n);
312 static inline unsigned int show_bits(GetBitContext *s, int n){
316 tmp= SHOW_UBITS(re, s, n);
317 // CLOSE_READER(re, s)
321 static inline void skip_bits(GetBitContext *s, int n){
322 //Note gcc seems to optimize this to s->index+=n for the ALT_READER :))
325 LAST_SKIP_BITS(re, s, n);
329 static inline unsigned int get_bits1(GetBitContext *s){
330 #ifdef ALT_BITSTREAM_READER
331 unsigned int index= s->index;
332 uint8_t result= s->buffer[ index>>3 ];
333 #ifdef ALT_BITSTREAM_READER_LE
334 result>>= (index&0x07);
337 result<<= (index&0x07);
345 return get_bits(s, 1);
349 static inline unsigned int show_bits1(GetBitContext *s){
350 return show_bits(s, 1);
353 static inline void skip_bits1(GetBitContext *s){
360 static inline unsigned int get_bits_long(GetBitContext *s, int n){
361 if(n<=MIN_CACHE_BITS) return get_bits(s, n);
363 #ifdef ALT_BITSTREAM_READER_LE
364 int ret= get_bits(s, 16);
365 return ret | (get_bits(s, n-16) << 16);
367 int ret= get_bits(s, 16) << (n-16);
368 return ret | get_bits(s, n-16);
374 * reads 0-32 bits as a signed integer.
376 static inline int get_sbits_long(GetBitContext *s, int n) {
377 return sign_extend(get_bits_long(s, n), n);
383 static inline unsigned int show_bits_long(GetBitContext *s, int n){
384 if(n<=MIN_CACHE_BITS) return show_bits(s, n);
386 GetBitContext gb= *s;
387 return get_bits_long(&gb, n);
391 static inline int check_marker(GetBitContext *s, const char *msg)
393 int bit= get_bits1(s);
395 av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
401 * init GetBitContext.
402 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
403 * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
404 * @param bit_size the size of the buffer in bits
406 * While GetBitContext stores the buffer size, for performance reasons you are
407 * responsible for checking for the buffer end yourself (take advantage of the padding)!
409 static inline void init_get_bits(GetBitContext *s,
410 const uint8_t *buffer, int bit_size)
412 int buffer_size= (bit_size+7)>>3;
413 if(buffer_size < 0 || bit_size < 0) {
414 buffer_size = bit_size = 0;
419 s->size_in_bits= bit_size;
420 s->buffer_end= buffer + buffer_size;
421 #ifdef ALT_BITSTREAM_READER
423 #elif defined A32_BITSTREAM_READER
424 s->buffer_ptr = (uint32_t*)((intptr_t)buffer&(~3));
425 s->bit_count = 32 + 8*((intptr_t)buffer&3);
426 skip_bits_long(s, 0);
430 static inline void align_get_bits(GetBitContext *s)
432 int n= (-get_bits_count(s)) & 7;
433 if(n) skip_bits(s, n);
436 #define init_vlc(vlc, nb_bits, nb_codes,\
437 bits, bits_wrap, bits_size,\
438 codes, codes_wrap, codes_size,\
440 init_vlc_sparse(vlc, nb_bits, nb_codes,\
441 bits, bits_wrap, bits_size,\
442 codes, codes_wrap, codes_size,\
445 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
446 const void *bits, int bits_wrap, int bits_size,
447 const void *codes, int codes_wrap, int codes_size,
448 const void *symbols, int symbols_wrap, int symbols_size,
450 #define INIT_VLC_LE 2
451 #define INIT_VLC_USE_NEW_STATIC 4
452 void free_vlc(VLC *vlc);
454 #define INIT_VLC_STATIC(vlc, bits, a,b,c,d,e,f,g, static_size)\
456 static VLC_TYPE table[static_size][2];\
457 (vlc)->table= table;\
458 (vlc)->table_allocated= static_size;\
459 init_vlc(vlc, bits, a,b,c,d,e,f,g, INIT_VLC_USE_NEW_STATIC);\
465 * If the vlc code is invalid and max_depth=1, then no bits will be removed.
466 * If the vlc code is invalid and max_depth>1, then the number of bits removed
469 #define GET_VLC(code, name, gb, table, bits, max_depth)\
474 index= SHOW_UBITS(name, gb, bits);\
475 code = table[index][0];\
476 n = table[index][1];\
478 if(max_depth > 1 && n < 0){\
479 LAST_SKIP_BITS(name, gb, bits);\
480 UPDATE_CACHE(name, gb);\
484 index= SHOW_UBITS(name, gb, nb_bits) + code;\
485 code = table[index][0];\
486 n = table[index][1];\
487 if(max_depth > 2 && n < 0){\
488 LAST_SKIP_BITS(name, gb, nb_bits);\
489 UPDATE_CACHE(name, gb);\
493 index= SHOW_UBITS(name, gb, nb_bits) + code;\
494 code = table[index][0];\
495 n = table[index][1];\
498 SKIP_BITS(name, gb, n);\
501 #define GET_RL_VLC(level, run, name, gb, table, bits, max_depth, need_update)\
506 index= SHOW_UBITS(name, gb, bits);\
507 level = table[index].level;\
508 n = table[index].len;\
510 if(max_depth > 1 && n < 0){\
511 SKIP_BITS(name, gb, bits);\
513 UPDATE_CACHE(name, gb);\
518 index= SHOW_UBITS(name, gb, nb_bits) + level;\
519 level = table[index].level;\
520 n = table[index].len;\
522 run= table[index].run;\
523 SKIP_BITS(name, gb, n);\
528 * parses a vlc code, faster then get_vlc()
529 * @param bits is the number of bits which will be read at once, must be
530 * identical to nb_bits in init_vlc()
531 * @param max_depth is the number of times bits bits must be read to completely
532 * read the longest vlc code
533 * = (max_vlc_length + bits - 1) / bits
535 static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
536 int bits, int max_depth)
543 GET_VLC(code, re, s, table, bits, max_depth);
552 static inline void print_bin(int bits, int n){
555 for(i=n-1; i>=0; i--){
556 av_log(NULL, AV_LOG_DEBUG, "%d", (bits>>i)&1);
559 av_log(NULL, AV_LOG_DEBUG, " ");
562 static inline int get_bits_trace(GetBitContext *s, int n, char *file, const char *func, int line){
563 int r= get_bits(s, n);
566 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d bit @%5d in %s %s:%d\n", r, n, r, get_bits_count(s)-n, file, func, line);
569 static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2], int bits, int max_depth, char *file, const char *func, int line){
570 int show= show_bits(s, 24);
571 int pos= get_bits_count(s);
572 int r= get_vlc2(s, table, bits, max_depth);
573 int len= get_bits_count(s) - pos;
574 int bits2= show>>(24-len);
576 print_bin(bits2, len);
578 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n", bits2, len, r, pos, file, func, line);
581 static inline int get_xbits_trace(GetBitContext *s, int n, char *file, const char *func, int line){
582 int show= show_bits(s, n);
583 int r= get_xbits(s, n);
586 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d xbt @%5d in %s %s:%d\n", show, n, r, get_bits_count(s)-n, file, func, line);
590 #define get_bits(s, n) get_bits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
591 #define get_bits1(s) get_bits_trace(s, 1, __FILE__, __PRETTY_FUNCTION__, __LINE__)
592 #define get_xbits(s, n) get_xbits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
593 #define get_vlc(s, vlc) get_vlc_trace(s, (vlc)->table, (vlc)->bits, 3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
594 #define get_vlc2(s, tab, bits, max) get_vlc_trace(s, tab, bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)
596 #define tprintf(p, ...) av_log(p, AV_LOG_DEBUG, __VA_ARGS__)
599 #define tprintf(p, ...) {}
602 static inline int decode012(GetBitContext *gb){
608 return get_bits1(gb) + 1;
611 static inline int decode210(GetBitContext *gb){
615 return 2 - get_bits1(gb);
618 static inline int get_bits_left(GetBitContext *gb)
620 return gb->size_in_bits - get_bits_count(gb);
623 #endif /* AVCODEC_GET_BITS_H */