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#include <stdlib.h>
31#include <assert.h>
32#include "libavutil/bswap.h"
33#include "libavutil/common.h"
34#include "libavutil/intreadwrite.h"
35#include "libavutil/log.h"
36#include "mathops.h"
37
38#if defined(ALT_BITSTREAM_READER_LE) && !defined(ALT_BITSTREAM_READER)
39#   define ALT_BITSTREAM_READER
40#endif
41
42#if !defined(LIBMPEG2_BITSTREAM_READER) && !defined(A32_BITSTREAM_READER) && !defined(ALT_BITSTREAM_READER)
43#   if ARCH_ARM && !HAVE_FAST_UNALIGNED
44#       define A32_BITSTREAM_READER
45#   else
46#       define ALT_BITSTREAM_READER
47//#define LIBMPEG2_BITSTREAM_READER
48//#define A32_BITSTREAM_READER
49#   endif
50#endif
51
52/* bit input */
53/* buffer, buffer_end and size_in_bits must be present and used by every reader */
54typedef struct GetBitContext {
55    const uint8_t *buffer, *buffer_end;
56#ifdef ALT_BITSTREAM_READER
57    int index;
58#elif defined LIBMPEG2_BITSTREAM_READER
59    uint8_t *buffer_ptr;
60    uint32_t cache;
61    int bit_count;
62#elif defined A32_BITSTREAM_READER
63    uint32_t *buffer_ptr;
64    uint32_t cache0;
65    uint32_t cache1;
66    int bit_count;
67#endif
68    int size_in_bits;
69} GetBitContext;
70
71#define VLC_TYPE int16_t
72
73typedef struct VLC {
74    int bits;
75    VLC_TYPE (*table)[2]; ///< code, bits
76    int table_size, table_allocated;
77} VLC;
78
79typedef struct RL_VLC_ELEM {
80    int16_t level;
81    int8_t len;
82    uint8_t run;
83} RL_VLC_ELEM;
84
85/* Bitstream reader API docs:
86name
87    arbitrary name which is used as prefix for the internal variables
88
89gb
90    getbitcontext
91
92OPEN_READER(name, gb)
93    loads gb into local variables
94
95CLOSE_READER(name, gb)
96    stores local vars in gb
97
98UPDATE_CACHE(name, gb)
99    refills the internal cache from the bitstream
100    after this call at least MIN_CACHE_BITS will be available,
101
102GET_CACHE(name, gb)
103    will output the contents of the internal cache, next bit is MSB of 32 or 64 bit (FIXME 64bit)
104
105SHOW_UBITS(name, gb, num)
106    will return the next num bits
107
108SHOW_SBITS(name, gb, num)
109    will return the next num bits and do sign extension
110
111SKIP_BITS(name, gb, num)
112    will skip over the next num bits
113    note, this is equivalent to SKIP_CACHE; SKIP_COUNTER
114
115SKIP_CACHE(name, gb, num)
116    will remove the next num bits from the cache (note SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER)
117
118SKIP_COUNTER(name, gb, num)
119    will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS)
120
121LAST_SKIP_CACHE(name, gb, num)
122    will remove the next num bits from the cache if it is needed for UPDATE_CACHE otherwise it will do nothing
123
124LAST_SKIP_BITS(name, gb, num)
125    is equivalent to LAST_SKIP_CACHE; SKIP_COUNTER
126
127for examples see get_bits, show_bits, skip_bits, get_vlc
128*/
129
130#ifdef ALT_BITSTREAM_READER
131#   define MIN_CACHE_BITS 25
132
133#   define OPEN_READER(name, gb)\
134        unsigned int name##_index= (gb)->index;\
135        int name##_cache= 0;\
136
137#   define CLOSE_READER(name, gb)\
138        (gb)->index= name##_index;\
139
140# ifdef ALT_BITSTREAM_READER_LE
141#   define UPDATE_CACHE(name, gb)\
142        name##_cache= AV_RL32( ((const uint8_t *)(gb)->buffer)+(name##_index>>3) ) >> (name##_index&0x07);\
143
144#   define SKIP_CACHE(name, gb, num)\
145        name##_cache >>= (num);
146# else
147#   define UPDATE_CACHE(name, gb)\
148        name##_cache= AV_RB32( ((const uint8_t *)(gb)->buffer)+(name##_index>>3) ) << (name##_index&0x07);\
149
150#   define SKIP_CACHE(name, gb, num)\
151        name##_cache <<= (num);
152# endif
153
154// FIXME name?
155#   define SKIP_COUNTER(name, gb, num)\
156        name##_index += (num);\
157
158#   define SKIP_BITS(name, gb, num)\
159        {\
160            SKIP_CACHE(name, gb, num)\
161            SKIP_COUNTER(name, gb, num)\
162        }\
163
164#   define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
165#   define LAST_SKIP_CACHE(name, gb, num) ;
166
167# ifdef ALT_BITSTREAM_READER_LE
168#   define SHOW_UBITS(name, gb, num)\
169        zero_extend(name##_cache, num)
170
171#   define SHOW_SBITS(name, gb, num)\
172        sign_extend(name##_cache, num)
173# else
174#   define SHOW_UBITS(name, gb, num)\
175        NEG_USR32(name##_cache, num)
176
177#   define SHOW_SBITS(name, gb, num)\
178        NEG_SSR32(name##_cache, num)
179# endif
180
181#   define GET_CACHE(name, gb)\
182        ((uint32_t)name##_cache)
183
184static inline int get_bits_count(const GetBitContext *s){
185    return s->index;
186}
187
188static inline void skip_bits_long(GetBitContext *s, int n){
189    s->index += n;
190}
191
192#elif defined LIBMPEG2_BITSTREAM_READER
193//libmpeg2 like reader
194
195#   define MIN_CACHE_BITS 17
196
197#   define OPEN_READER(name, gb)\
198        int name##_bit_count=(gb)->bit_count;\
199        int name##_cache= (gb)->cache;\
200        uint8_t * name##_buffer_ptr=(gb)->buffer_ptr;\
201
202#   define CLOSE_READER(name, gb)\
203        (gb)->bit_count= name##_bit_count;\
204        (gb)->cache= name##_cache;\
205        (gb)->buffer_ptr= name##_buffer_ptr;\
206
207#   define UPDATE_CACHE(name, gb)\
208    if(name##_bit_count >= 0){\
209        name##_cache+= AV_RB16(name##_buffer_ptr) << name##_bit_count; \
210        name##_buffer_ptr+=2;\
211        name##_bit_count-= 16;\
212    }\
213
214#   define SKIP_CACHE(name, gb, num)\
215        name##_cache <<= (num);\
216
217#   define SKIP_COUNTER(name, gb, num)\
218        name##_bit_count += (num);\
219
220#   define SKIP_BITS(name, gb, num)\
221        {\
222            SKIP_CACHE(name, gb, num)\
223            SKIP_COUNTER(name, gb, num)\
224        }\
225
226#   define LAST_SKIP_BITS(name, gb, num) SKIP_BITS(name, gb, num)
227#   define LAST_SKIP_CACHE(name, gb, num) SKIP_CACHE(name, gb, num)
228
229#   define SHOW_UBITS(name, gb, num)\
230        NEG_USR32(name##_cache, num)
231
232#   define SHOW_SBITS(name, gb, num)\
233        NEG_SSR32(name##_cache, num)
234
235#   define GET_CACHE(name, gb)\
236        ((uint32_t)name##_cache)
237
238static inline int get_bits_count(const GetBitContext *s){
239    return (s->buffer_ptr - s->buffer)*8 - 16 + s->bit_count;
240}
241
242static inline void skip_bits_long(GetBitContext *s, int n){
243    OPEN_READER(re, s)
244    re_bit_count += n;
245    re_buffer_ptr += 2*(re_bit_count>>4);
246    re_bit_count &= 15;
247    re_cache = ((re_buffer_ptr[-2]<<8) + re_buffer_ptr[-1]) << (16+re_bit_count);
248    UPDATE_CACHE(re, s)
249    CLOSE_READER(re, s)
250}
251
252#elif defined A32_BITSTREAM_READER
253
254#   define MIN_CACHE_BITS 32
255
256#   define OPEN_READER(name, gb)\
257        int name##_bit_count=(gb)->bit_count;\
258        uint32_t name##_cache0= (gb)->cache0;\
259        uint32_t name##_cache1= (gb)->cache1;\
260        uint32_t * name##_buffer_ptr=(gb)->buffer_ptr;\
261
262#   define CLOSE_READER(name, gb)\
263        (gb)->bit_count= name##_bit_count;\
264        (gb)->cache0= name##_cache0;\
265        (gb)->cache1= name##_cache1;\
266        (gb)->buffer_ptr= name##_buffer_ptr;\
267
268#   define UPDATE_CACHE(name, gb)\
269    if(name##_bit_count > 0){\
270        const uint32_t next= be2me_32( *name##_buffer_ptr );\
271        name##_cache0 |= NEG_USR32(next,name##_bit_count);\
272        name##_cache1 |= next<<name##_bit_count;\
273        name##_buffer_ptr++;\
274        name##_bit_count-= 32;\
275    }\
276
277#if ARCH_X86
278#   define SKIP_CACHE(name, gb, num)\
279        __asm__(\
280            "shldl %2, %1, %0          \n\t"\
281            "shll %2, %1               \n\t"\
282            : "+r" (name##_cache0), "+r" (name##_cache1)\
283            : "Ic" ((uint8_t)(num))\
284           );
285#else
286#   define SKIP_CACHE(name, gb, num)\
287        name##_cache0 <<= (num);\
288        name##_cache0 |= NEG_USR32(name##_cache1,num);\
289        name##_cache1 <<= (num);
290#endif
291
292#   define SKIP_COUNTER(name, gb, num)\
293        name##_bit_count += (num);\
294
295#   define SKIP_BITS(name, gb, num)\
296        {\
297            SKIP_CACHE(name, gb, num)\
298            SKIP_COUNTER(name, gb, num)\
299        }\
300
301#   define LAST_SKIP_BITS(name, gb, num) SKIP_BITS(name, gb, num)
302#   define LAST_SKIP_CACHE(name, gb, num) SKIP_CACHE(name, gb, num)
303
304#   define SHOW_UBITS(name, gb, num)\
305        NEG_USR32(name##_cache0, num)
306
307#   define SHOW_SBITS(name, gb, num)\
308        NEG_SSR32(name##_cache0, num)
309
310#   define GET_CACHE(name, gb)\
311        (name##_cache0)
312
313static inline int get_bits_count(const GetBitContext *s){
314    return ((uint8_t*)s->buffer_ptr - s->buffer)*8 - 32 + s->bit_count;
315}
316
317static inline void skip_bits_long(GetBitContext *s, int n){
318    OPEN_READER(re, s)
319    re_bit_count += n;
320    re_buffer_ptr += re_bit_count>>5;
321    re_bit_count &= 31;
322    re_cache0 = be2me_32( re_buffer_ptr[-1] ) << re_bit_count;
323    re_cache1 = 0;
324    UPDATE_CACHE(re, s)
325    CLOSE_READER(re, s)
326}
327
328#endif
329
330/**
331 * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
332 * if MSB not set it is negative
333 * @param n length in bits
334 * @author BERO
335 */
336static inline int get_xbits(GetBitContext *s, int n){
337    register int sign;
338    register int32_t cache;
339    OPEN_READER(re, s)
340    UPDATE_CACHE(re, s)
341    cache = GET_CACHE(re,s);
342    sign=(~cache)>>31;
343    LAST_SKIP_BITS(re, s, n)
344    CLOSE_READER(re, s)
345    return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
346}
347
348static inline int get_sbits(GetBitContext *s, int n){
349    register int tmp;
350    OPEN_READER(re, s)
351    UPDATE_CACHE(re, s)
352    tmp= SHOW_SBITS(re, s, n);
353    LAST_SKIP_BITS(re, s, n)
354    CLOSE_READER(re, s)
355    return tmp;
356}
357
358/**
359 * reads 1-17 bits.
360 * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
361 */
362static inline unsigned int get_bits(GetBitContext *s, int n){
363    register int tmp;
364    OPEN_READER(re, s)
365    UPDATE_CACHE(re, s)
366    tmp= SHOW_UBITS(re, s, n);
367    LAST_SKIP_BITS(re, s, n)
368    CLOSE_READER(re, s)
369    return tmp;
370}
371
372/**
373 * shows 1-17 bits.
374 * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
375 */
376static inline unsigned int show_bits(GetBitContext *s, int n){
377    register int tmp;
378    OPEN_READER(re, s)
379    UPDATE_CACHE(re, s)
380    tmp= SHOW_UBITS(re, s, n);
381//    CLOSE_READER(re, s)
382    return tmp;
383}
384
385static inline void skip_bits(GetBitContext *s, int n){
386 //Note gcc seems to optimize this to s->index+=n for the ALT_READER :))
387    OPEN_READER(re, s)
388    UPDATE_CACHE(re, s)
389    LAST_SKIP_BITS(re, s, n)
390    CLOSE_READER(re, s)
391}
392
393static inline unsigned int get_bits1(GetBitContext *s){
394#ifdef ALT_BITSTREAM_READER
395    unsigned int index= s->index;
396    uint8_t result= s->buffer[ index>>3 ];
397#ifdef ALT_BITSTREAM_READER_LE
398    result>>= (index&0x07);
399    result&= 1;
400#else
401    result<<= (index&0x07);
402    result>>= 8 - 1;
403#endif
404    index++;
405    s->index= index;
406
407    return result;
408#else
409    return get_bits(s, 1);
410#endif
411}
412
413static inline unsigned int show_bits1(GetBitContext *s){
414    return show_bits(s, 1);
415}
416
417static inline void skip_bits1(GetBitContext *s){
418    skip_bits(s, 1);
419}
420
421/**
422 * reads 0-32 bits.
423 */
424static inline unsigned int get_bits_long(GetBitContext *s, int n){
425    if(n<=MIN_CACHE_BITS) return get_bits(s, n);
426    else{
427#ifdef ALT_BITSTREAM_READER_LE
428        int ret= get_bits(s, 16);
429        return ret | (get_bits(s, n-16) << 16);
430#else
431        int ret= get_bits(s, 16) << (n-16);
432        return ret | get_bits(s, n-16);
433#endif
434    }
435}
436
437/**
438 * reads 0-32 bits as a signed integer.
439 */
440static inline int get_sbits_long(GetBitContext *s, int n) {
441    return sign_extend(get_bits_long(s, n), n);
442}
443
444/**
445 * shows 0-32 bits.
446 */
447static inline unsigned int show_bits_long(GetBitContext *s, int n){
448    if(n<=MIN_CACHE_BITS) return show_bits(s, n);
449    else{
450        GetBitContext gb= *s;
451        return get_bits_long(&gb, n);
452    }
453}
454
455static inline int check_marker(GetBitContext *s, const char *msg)
456{
457    int bit= get_bits1(s);
458    if(!bit)
459        av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
460
461    return bit;
462}
463
464/**
465 * init GetBitContext.
466 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
467 * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
468 * @param bit_size the size of the buffer in bits
469 *
470 * While GetBitContext stores the buffer size, for performance reasons you are
471 * responsible for checking for the buffer end yourself (take advantage of the padding)!
472 */
473static inline void init_get_bits(GetBitContext *s,
474                   const uint8_t *buffer, int bit_size)
475{
476    int buffer_size= (bit_size+7)>>3;
477    if(buffer_size < 0 || bit_size < 0) {
478        buffer_size = bit_size = 0;
479        buffer = NULL;
480    }
481
482    s->buffer= buffer;
483    s->size_in_bits= bit_size;
484    s->buffer_end= buffer + buffer_size;
485#ifdef ALT_BITSTREAM_READER
486    s->index=0;
487#elif defined LIBMPEG2_BITSTREAM_READER
488    s->buffer_ptr = (uint8_t*)((intptr_t)buffer&(~1));
489    s->bit_count = 16 + 8*((intptr_t)buffer&1);
490    skip_bits_long(s, 0);
491#elif defined A32_BITSTREAM_READER
492    s->buffer_ptr = (uint32_t*)((intptr_t)buffer&(~3));
493    s->bit_count = 32 + 8*((intptr_t)buffer&3);
494    skip_bits_long(s, 0);
495#endif
496}
497
498static inline void align_get_bits(GetBitContext *s)
499{
500    int n= (-get_bits_count(s)) & 7;
501    if(n) skip_bits(s, n);
502}
503
504#define init_vlc(vlc, nb_bits, nb_codes,\
505                 bits, bits_wrap, bits_size,\
506                 codes, codes_wrap, codes_size,\
507                 flags)\
508        init_vlc_sparse(vlc, nb_bits, nb_codes,\
509                 bits, bits_wrap, bits_size,\
510                 codes, codes_wrap, codes_size,\
511                 NULL, 0, 0, flags)
512
513int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
514             const void *bits, int bits_wrap, int bits_size,
515             const void *codes, int codes_wrap, int codes_size,
516             const void *symbols, int symbols_wrap, int symbols_size,
517             int flags);
518#define INIT_VLC_LE         2
519#define INIT_VLC_USE_NEW_STATIC 4
520void free_vlc(VLC *vlc);
521
522#define INIT_VLC_STATIC(vlc, bits, a,b,c,d,e,f,g, static_size)\
523{\
524    static VLC_TYPE table[static_size][2];\
525    (vlc)->table= table;\
526    (vlc)->table_allocated= static_size;\
527    init_vlc(vlc, bits, a,b,c,d,e,f,g, INIT_VLC_USE_NEW_STATIC);\
528}
529
530
531/**
532 *
533 * If the vlc code is invalid and max_depth=1, then no bits will be removed.
534 * If the vlc code is invalid and max_depth>1, then the number of bits removed
535 * is undefined.
536 */
537#define GET_VLC(code, name, gb, table, bits, max_depth)\
538{\
539    int n, nb_bits;\
540    unsigned int index;\
541\
542    index= SHOW_UBITS(name, gb, bits);\
543    code = table[index][0];\
544    n    = table[index][1];\
545\
546    if(max_depth > 1 && n < 0){\
547        LAST_SKIP_BITS(name, gb, bits)\
548        UPDATE_CACHE(name, gb)\
549\
550        nb_bits = -n;\
551\
552        index= SHOW_UBITS(name, gb, nb_bits) + code;\
553        code = table[index][0];\
554        n    = table[index][1];\
555        if(max_depth > 2 && n < 0){\
556            LAST_SKIP_BITS(name, gb, nb_bits)\
557            UPDATE_CACHE(name, gb)\
558\
559            nb_bits = -n;\
560\
561            index= SHOW_UBITS(name, gb, nb_bits) + code;\
562            code = table[index][0];\
563            n    = table[index][1];\
564        }\
565    }\
566    SKIP_BITS(name, gb, n)\
567}
568
569#define GET_RL_VLC(level, run, name, gb, table, bits, max_depth, need_update)\
570{\
571    int n, nb_bits;\
572    unsigned int index;\
573\
574    index= SHOW_UBITS(name, gb, bits);\
575    level = table[index].level;\
576    n     = table[index].len;\
577\
578    if(max_depth > 1 && n < 0){\
579        SKIP_BITS(name, gb, bits)\
580        if(need_update){\
581            UPDATE_CACHE(name, gb)\
582        }\
583\
584        nb_bits = -n;\
585\
586        index= SHOW_UBITS(name, gb, nb_bits) + level;\
587        level = table[index].level;\
588        n     = table[index].len;\
589    }\
590    run= table[index].run;\
591    SKIP_BITS(name, gb, n)\
592}
593
594
595/**
596 * parses a vlc code, faster then get_vlc()
597 * @param bits is the number of bits which will be read at once, must be
598 *             identical to nb_bits in init_vlc()
599 * @param max_depth is the number of times bits bits must be read to completely
600 *                  read the longest vlc code
601 *                  = (max_vlc_length + bits - 1) / bits
602 */
603static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
604                                  int bits, int max_depth)
605{
606    int code;
607
608    OPEN_READER(re, s)
609    UPDATE_CACHE(re, s)
610
611    GET_VLC(code, re, s, table, bits, max_depth)
612
613    CLOSE_READER(re, s)
614    return code;
615}
616
617//#define TRACE
618
619#ifdef TRACE
620static inline void print_bin(int bits, int n){
621    int i;
622
623    for(i=n-1; i>=0; i--){
624        av_log(NULL, AV_LOG_DEBUG, "%d", (bits>>i)&1);
625    }
626    for(i=n; i<24; i++)
627        av_log(NULL, AV_LOG_DEBUG, " ");
628}
629
630static inline int get_bits_trace(GetBitContext *s, int n, char *file, const char *func, int line){
631    int r= get_bits(s, n);
632
633    print_bin(r, n);
634    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);
635    return r;
636}
637static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2], int bits, int max_depth, char *file, const char *func, int line){
638    int show= show_bits(s, 24);
639    int pos= get_bits_count(s);
640    int r= get_vlc2(s, table, bits, max_depth);
641    int len= get_bits_count(s) - pos;
642    int bits2= show>>(24-len);
643
644    print_bin(bits2, len);
645
646    av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n", bits2, len, r, pos, file, func, line);
647    return r;
648}
649static inline int get_xbits_trace(GetBitContext *s, int n, char *file, const char *func, int line){
650    int show= show_bits(s, n);
651    int r= get_xbits(s, n);
652
653    print_bin(show, n);
654    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);
655    return r;
656}
657
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__)
661#define get_vlc(s, vlc)            get_vlc_trace(s, (vlc)->table, (vlc)->bits, 3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
662#define get_vlc2(s, tab, bits, max) get_vlc_trace(s, tab, bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)
663
664#define tprintf(p, ...) av_log(p, AV_LOG_DEBUG, __VA_ARGS__)
665
666#else //TRACE
667#define tprintf(p, ...) {}
668#endif
669
670static inline int decode012(GetBitContext *gb){
671    int n;
672    n = get_bits1(gb);
673    if (n == 0)
674        return 0;
675    else
676        return get_bits1(gb) + 1;
677}
678
679static inline int decode210(GetBitContext *gb){
680    if (get_bits1(gb))
681        return 0;
682    else
683        return 2 - get_bits1(gb);
684}
685
686static inline int get_bits_left(GetBitContext *gb)
687{
688    return gb->size_in_bits - get_bits_count(gb);
689}
690
691#endif /* AVCODEC_GET_BITS_H */
692