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ffmpeg / libavcodec / get_bits.h @ 990f213e

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/*
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 * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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/**
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 * @file
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 * bitstream reader API header.
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 */
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#ifndef AVCODEC_GET_BITS_H
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#define AVCODEC_GET_BITS_H
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#include <stdint.h>
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#include <stdlib.h>
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#include <assert.h>
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#include "libavutil/bswap.h"
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#include "libavutil/common.h"
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#include "libavutil/intreadwrite.h"
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#include "libavutil/log.h"
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#include "mathops.h"
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#if defined(ALT_BITSTREAM_READER_LE) && !defined(ALT_BITSTREAM_READER)
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#   define ALT_BITSTREAM_READER
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#endif
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#if !defined(A32_BITSTREAM_READER) && !defined(ALT_BITSTREAM_READER)
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#   if ARCH_ARM && !HAVE_FAST_UNALIGNED
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#       define A32_BITSTREAM_READER
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#   else
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#       define ALT_BITSTREAM_READER
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//#define A32_BITSTREAM_READER
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#   endif
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#endif
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/* bit input */
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/* buffer, buffer_end and size_in_bits must be present and used by every reader */
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typedef struct GetBitContext {
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    const uint8_t *buffer, *buffer_end;
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#ifdef ALT_BITSTREAM_READER
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    int index;
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#elif defined A32_BITSTREAM_READER
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    uint32_t *buffer_ptr;
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    uint32_t cache0;
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    uint32_t cache1;
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    int bit_count;
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#endif
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    int size_in_bits;
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} GetBitContext;
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#define VLC_TYPE int16_t
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typedef struct VLC {
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    int bits;
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    VLC_TYPE (*table)[2]; ///< code, bits
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    int table_size, table_allocated;
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} VLC;
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typedef struct RL_VLC_ELEM {
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    int16_t level;
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    int8_t len;
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    uint8_t run;
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} RL_VLC_ELEM;
79

    
80
/* Bitstream reader API docs:
81
name
82
    arbitrary name which is used as prefix for the internal variables
83

84
gb
85
    getbitcontext
86

87
OPEN_READER(name, gb)
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    loads gb into local variables
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90
CLOSE_READER(name, gb)
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    stores local vars in gb
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93
UPDATE_CACHE(name, gb)
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    refills the internal cache from the bitstream
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    after this call at least MIN_CACHE_BITS will be available,
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97
GET_CACHE(name, gb)
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    will output the contents of the internal cache, next bit is MSB of 32 or 64 bit (FIXME 64bit)
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100
SHOW_UBITS(name, gb, num)
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    will return the next num bits
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103
SHOW_SBITS(name, gb, num)
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    will return the next num bits and do sign extension
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106
SKIP_BITS(name, gb, num)
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    will skip over the next num bits
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    note, this is equivalent to SKIP_CACHE; SKIP_COUNTER
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110
SKIP_CACHE(name, gb, num)
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    will remove the next num bits from the cache (note SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER)
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113
SKIP_COUNTER(name, gb, num)
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    will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS)
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116
LAST_SKIP_CACHE(name, gb, num)
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    will remove the next num bits from the cache if it is needed for UPDATE_CACHE otherwise it will do nothing
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119
LAST_SKIP_BITS(name, gb, num)
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    is equivalent to LAST_SKIP_CACHE; SKIP_COUNTER
121

122
for examples see get_bits, show_bits, skip_bits, get_vlc
123
*/
124

    
125
#ifdef ALT_BITSTREAM_READER
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#   define MIN_CACHE_BITS 25
127

    
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#   define OPEN_READER(name, gb)\
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        unsigned int name##_index= (gb)->index;\
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        int name##_cache= 0;\
131

    
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#   define CLOSE_READER(name, gb)\
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        (gb)->index= name##_index;\
134

    
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# ifdef ALT_BITSTREAM_READER_LE
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#   define UPDATE_CACHE(name, gb)\
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        name##_cache= AV_RL32( ((const uint8_t *)(gb)->buffer)+(name##_index>>3) ) >> (name##_index&0x07);\
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#   define SKIP_CACHE(name, gb, num)\
140
        name##_cache >>= (num);
141
# else
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#   define UPDATE_CACHE(name, gb)\
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        name##_cache= AV_RB32( ((const uint8_t *)(gb)->buffer)+(name##_index>>3) ) << (name##_index&0x07);\
144

    
145
#   define SKIP_CACHE(name, gb, num)\
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        name##_cache <<= (num);
147
# endif
148

    
149
// FIXME name?
150
#   define SKIP_COUNTER(name, gb, num)\
151
        name##_index += (num);\
152

    
153
#   define SKIP_BITS(name, gb, num)\
154
        {\
155
            SKIP_CACHE(name, gb, num)\
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            SKIP_COUNTER(name, gb, num)\
157
        }\
158

    
159
#   define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
160
#   define LAST_SKIP_CACHE(name, gb, num) ;
161

    
162
# ifdef ALT_BITSTREAM_READER_LE
163
#   define SHOW_UBITS(name, gb, num)\
164
        zero_extend(name##_cache, num)
165

    
166
#   define SHOW_SBITS(name, gb, num)\
167
        sign_extend(name##_cache, num)
168
# else
169
#   define SHOW_UBITS(name, gb, num)\
170
        NEG_USR32(name##_cache, num)
171

    
172
#   define SHOW_SBITS(name, gb, num)\
173
        NEG_SSR32(name##_cache, num)
174
# endif
175

    
176
#   define GET_CACHE(name, gb)\
177
        ((uint32_t)name##_cache)
178

    
179
static inline int get_bits_count(const GetBitContext *s){
180
    return s->index;
181
}
182

    
183
static inline void skip_bits_long(GetBitContext *s, int n){
184
    s->index += n;
185
}
186

    
187
#elif defined A32_BITSTREAM_READER
188

    
189
#   define MIN_CACHE_BITS 32
190

    
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;\
196

    
197
#   define CLOSE_READER(name, gb)\
198
        (gb)->bit_count= name##_bit_count;\
199
        (gb)->cache0= name##_cache0;\
200
        (gb)->cache1= name##_cache1;\
201
        (gb)->buffer_ptr= name##_buffer_ptr;\
202

    
203
#   define UPDATE_CACHE(name, gb)\
204
    if(name##_bit_count > 0){\
205
        const uint32_t next= av_be2ne32( *name##_buffer_ptr );\
206
        name##_cache0 |= NEG_USR32(next,name##_bit_count);\
207
        name##_cache1 |= next<<name##_bit_count;\
208
        name##_buffer_ptr++;\
209
        name##_bit_count-= 32;\
210
    }\
211

    
212
#if ARCH_X86
213
#   define SKIP_CACHE(name, gb, num)\
214
        __asm__(\
215
            "shldl %2, %1, %0          \n\t"\
216
            "shll %2, %1               \n\t"\
217
            : "+r" (name##_cache0), "+r" (name##_cache1)\
218
            : "Ic" ((uint8_t)(num))\
219
           );
220
#else
221
#   define SKIP_CACHE(name, gb, num)\
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        name##_cache0 <<= (num);\
223
        name##_cache0 |= NEG_USR32(name##_cache1,num);\
224
        name##_cache1 <<= (num);
225
#endif
226

    
227
#   define SKIP_COUNTER(name, gb, num)\
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        name##_bit_count += (num);\
229

    
230
#   define SKIP_BITS(name, gb, num)\
231
        {\
232
            SKIP_CACHE(name, gb, num)\
233
            SKIP_COUNTER(name, gb, num)\
234
        }\
235

    
236
#   define LAST_SKIP_BITS(name, gb, num) SKIP_BITS(name, gb, num)
237
#   define LAST_SKIP_CACHE(name, gb, num) SKIP_CACHE(name, gb, num)
238

    
239
#   define SHOW_UBITS(name, gb, num)\
240
        NEG_USR32(name##_cache0, num)
241

    
242
#   define SHOW_SBITS(name, gb, num)\
243
        NEG_SSR32(name##_cache0, num)
244

    
245
#   define GET_CACHE(name, gb)\
246
        (name##_cache0)
247

    
248
static inline int get_bits_count(const GetBitContext *s){
249
    return ((uint8_t*)s->buffer_ptr - s->buffer)*8 - 32 + s->bit_count;
250
}
251

    
252
static inline void skip_bits_long(GetBitContext *s, int n){
253
    OPEN_READER(re, s)
254
    re_bit_count += n;
255
    re_buffer_ptr += re_bit_count>>5;
256
    re_bit_count &= 31;
257
    re_cache0 = av_be2ne32( re_buffer_ptr[-1] ) << re_bit_count;
258
    re_cache1 = 0;
259
    UPDATE_CACHE(re, s)
260
    CLOSE_READER(re, s)
261
}
262

    
263
#endif
264

    
265
/**
266
 * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
267
 * if MSB not set it is negative
268
 * @param n length in bits
269
 * @author BERO
270
 */
271
static inline int get_xbits(GetBitContext *s, int n){
272
    register int sign;
273
    register int32_t cache;
274
    OPEN_READER(re, s)
275
    UPDATE_CACHE(re, s)
276
    cache = GET_CACHE(re,s);
277
    sign=(~cache)>>31;
278
    LAST_SKIP_BITS(re, s, n)
279
    CLOSE_READER(re, s)
280
    return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
281
}
282

    
283
static inline int get_sbits(GetBitContext *s, int n){
284
    register int tmp;
285
    OPEN_READER(re, s)
286
    UPDATE_CACHE(re, s)
287
    tmp= SHOW_SBITS(re, s, n);
288
    LAST_SKIP_BITS(re, s, n)
289
    CLOSE_READER(re, s)
290
    return tmp;
291
}
292

    
293
/**
294
 * Read 1-25 bits.
295
 */
296
static inline unsigned int get_bits(GetBitContext *s, int n){
297
    register int tmp;
298
    OPEN_READER(re, s)
299
    UPDATE_CACHE(re, s)
300
    tmp= SHOW_UBITS(re, s, n);
301
    LAST_SKIP_BITS(re, s, n)
302
    CLOSE_READER(re, s)
303
    return tmp;
304
}
305

    
306
/**
307
 * Shows 1-25 bits.
308
 */
309
static inline unsigned int show_bits(GetBitContext *s, int n){
310
    register int tmp;
311
    OPEN_READER(re, s)
312
    UPDATE_CACHE(re, s)
313
    tmp= SHOW_UBITS(re, s, n);
314
//    CLOSE_READER(re, s)
315
    return tmp;
316
}
317

    
318
static inline void skip_bits(GetBitContext *s, int n){
319
 //Note gcc seems to optimize this to s->index+=n for the ALT_READER :))
320
    OPEN_READER(re, s)
321
    UPDATE_CACHE(re, s)
322
    LAST_SKIP_BITS(re, s, n)
323
    CLOSE_READER(re, s)
324
}
325

    
326
static inline unsigned int get_bits1(GetBitContext *s){
327
#ifdef ALT_BITSTREAM_READER
328
    unsigned int index= s->index;
329
    uint8_t result= s->buffer[ index>>3 ];
330
#ifdef ALT_BITSTREAM_READER_LE
331
    result>>= (index&0x07);
332
    result&= 1;
333
#else
334
    result<<= (index&0x07);
335
    result>>= 8 - 1;
336
#endif
337
    index++;
338
    s->index= index;
339

    
340
    return result;
341
#else
342
    return get_bits(s, 1);
343
#endif
344
}
345

    
346
static inline unsigned int show_bits1(GetBitContext *s){
347
    return show_bits(s, 1);
348
}
349

    
350
static inline void skip_bits1(GetBitContext *s){
351
    skip_bits(s, 1);
352
}
353

    
354
/**
355
 * reads 0-32 bits.
356
 */
357
static inline unsigned int get_bits_long(GetBitContext *s, int n){
358
    if(n<=MIN_CACHE_BITS) return get_bits(s, n);
359
    else{
360
#ifdef ALT_BITSTREAM_READER_LE
361
        int ret= get_bits(s, 16);
362
        return ret | (get_bits(s, n-16) << 16);
363
#else
364
        int ret= get_bits(s, 16) << (n-16);
365
        return ret | get_bits(s, n-16);
366
#endif
367
    }
368
}
369

    
370
/**
371
 * reads 0-32 bits as a signed integer.
372
 */
373
static inline int get_sbits_long(GetBitContext *s, int n) {
374
    return sign_extend(get_bits_long(s, n), n);
375
}
376

    
377
/**
378
 * shows 0-32 bits.
379
 */
380
static inline unsigned int show_bits_long(GetBitContext *s, int n){
381
    if(n<=MIN_CACHE_BITS) return show_bits(s, n);
382
    else{
383
        GetBitContext gb= *s;
384
        return get_bits_long(&gb, n);
385
    }
386
}
387

    
388
static inline int check_marker(GetBitContext *s, const char *msg)
389
{
390
    int bit= get_bits1(s);
391
    if(!bit)
392
        av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
393

    
394
    return bit;
395
}
396

    
397
/**
398
 * init GetBitContext.
399
 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
400
 * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
401
 * @param bit_size the size of the buffer in bits
402
 *
403
 * While GetBitContext stores the buffer size, for performance reasons you are
404
 * responsible for checking for the buffer end yourself (take advantage of the padding)!
405
 */
406
static inline void init_get_bits(GetBitContext *s,
407
                   const uint8_t *buffer, int bit_size)
408
{
409
    int buffer_size= (bit_size+7)>>3;
410
    if(buffer_size < 0 || bit_size < 0) {
411
        buffer_size = bit_size = 0;
412
        buffer = NULL;
413
    }
414

    
415
    s->buffer= buffer;
416
    s->size_in_bits= bit_size;
417
    s->buffer_end= buffer + buffer_size;
418
#ifdef ALT_BITSTREAM_READER
419
    s->index=0;
420
#elif defined A32_BITSTREAM_READER
421
    s->buffer_ptr = (uint32_t*)((intptr_t)buffer&(~3));
422
    s->bit_count = 32 + 8*((intptr_t)buffer&3);
423
    skip_bits_long(s, 0);
424
#endif
425
}
426

    
427
static inline void align_get_bits(GetBitContext *s)
428
{
429
    int n= (-get_bits_count(s)) & 7;
430
    if(n) skip_bits(s, n);
431
}
432

    
433
#define init_vlc(vlc, nb_bits, nb_codes,\
434
                 bits, bits_wrap, bits_size,\
435
                 codes, codes_wrap, codes_size,\
436
                 flags)\
437
        init_vlc_sparse(vlc, nb_bits, nb_codes,\
438
                 bits, bits_wrap, bits_size,\
439
                 codes, codes_wrap, codes_size,\
440
                 NULL, 0, 0, flags)
441

    
442
int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
443
             const void *bits, int bits_wrap, int bits_size,
444
             const void *codes, int codes_wrap, int codes_size,
445
             const void *symbols, int symbols_wrap, int symbols_size,
446
             int flags);
447
#define INIT_VLC_LE         2
448
#define INIT_VLC_USE_NEW_STATIC 4
449
void free_vlc(VLC *vlc);
450

    
451
#define INIT_VLC_STATIC(vlc, bits, a,b,c,d,e,f,g, static_size)\
452
{\
453
    static VLC_TYPE table[static_size][2];\
454
    (vlc)->table= table;\
455
    (vlc)->table_allocated= static_size;\
456
    init_vlc(vlc, bits, a,b,c,d,e,f,g, INIT_VLC_USE_NEW_STATIC);\
457
}
458

    
459

    
460
/**
461
 *
462
 * If the vlc code is invalid and max_depth=1, then no bits will be removed.
463
 * If the vlc code is invalid and max_depth>1, then the number of bits removed
464
 * is undefined.
465
 */
466
#define GET_VLC(code, name, gb, table, bits, max_depth)\
467
{\
468
    int n, nb_bits;\
469
    unsigned int index;\
470
\
471
    index= SHOW_UBITS(name, gb, bits);\
472
    code = table[index][0];\
473
    n    = table[index][1];\
474
\
475
    if(max_depth > 1 && n < 0){\
476
        LAST_SKIP_BITS(name, gb, bits)\
477
        UPDATE_CACHE(name, gb)\
478
\
479
        nb_bits = -n;\
480
\
481
        index= SHOW_UBITS(name, gb, nb_bits) + code;\
482
        code = table[index][0];\
483
        n    = table[index][1];\
484
        if(max_depth > 2 && n < 0){\
485
            LAST_SKIP_BITS(name, gb, nb_bits)\
486
            UPDATE_CACHE(name, gb)\
487
\
488
            nb_bits = -n;\
489
\
490
            index= SHOW_UBITS(name, gb, nb_bits) + code;\
491
            code = table[index][0];\
492
            n    = table[index][1];\
493
        }\
494
    }\
495
    SKIP_BITS(name, gb, n)\
496
}
497

    
498
#define GET_RL_VLC(level, run, name, gb, table, bits, max_depth, need_update)\
499
{\
500
    int n, nb_bits;\
501
    unsigned int index;\
502
\
503
    index= SHOW_UBITS(name, gb, bits);\
504
    level = table[index].level;\
505
    n     = table[index].len;\
506
\
507
    if(max_depth > 1 && n < 0){\
508
        SKIP_BITS(name, gb, bits)\
509
        if(need_update){\
510
            UPDATE_CACHE(name, gb)\
511
        }\
512
\
513
        nb_bits = -n;\
514
\
515
        index= SHOW_UBITS(name, gb, nb_bits) + level;\
516
        level = table[index].level;\
517
        n     = table[index].len;\
518
    }\
519
    run= table[index].run;\
520
    SKIP_BITS(name, gb, n)\
521
}
522

    
523

    
524
/**
525
 * parses a vlc code, faster then get_vlc()
526
 * @param bits is the number of bits which will be read at once, must be
527
 *             identical to nb_bits in init_vlc()
528
 * @param max_depth is the number of times bits bits must be read to completely
529
 *                  read the longest vlc code
530
 *                  = (max_vlc_length + bits - 1) / bits
531
 */
532
static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
533
                                  int bits, int max_depth)
534
{
535
    int code;
536

    
537
    OPEN_READER(re, s)
538
    UPDATE_CACHE(re, s)
539

    
540
    GET_VLC(code, re, s, table, bits, max_depth)
541

    
542
    CLOSE_READER(re, s)
543
    return code;
544
}
545

    
546
//#define TRACE
547

    
548
#ifdef TRACE
549
static inline void print_bin(int bits, int n){
550
    int i;
551

    
552
    for(i=n-1; i>=0; i--){
553
        av_log(NULL, AV_LOG_DEBUG, "%d", (bits>>i)&1);
554
    }
555
    for(i=n; i<24; i++)
556
        av_log(NULL, AV_LOG_DEBUG, " ");
557
}
558

    
559
static inline int get_bits_trace(GetBitContext *s, int n, char *file, const char *func, int line){
560
    int r= get_bits(s, n);
561

    
562
    print_bin(r, n);
563
    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);
564
    return r;
565
}
566
static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2], int bits, int max_depth, char *file, const char *func, int line){
567
    int show= show_bits(s, 24);
568
    int pos= get_bits_count(s);
569
    int r= get_vlc2(s, table, bits, max_depth);
570
    int len= get_bits_count(s) - pos;
571
    int bits2= show>>(24-len);
572

    
573
    print_bin(bits2, len);
574

    
575
    av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n", bits2, len, r, pos, file, func, line);
576
    return r;
577
}
578
static inline int get_xbits_trace(GetBitContext *s, int n, char *file, const char *func, int line){
579
    int show= show_bits(s, n);
580
    int r= get_xbits(s, n);
581

    
582
    print_bin(show, n);
583
    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);
584
    return r;
585
}
586

    
587
#define get_bits(s, n)  get_bits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
588
#define get_bits1(s)    get_bits_trace(s, 1, __FILE__, __PRETTY_FUNCTION__, __LINE__)
589
#define get_xbits(s, n) get_xbits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
590
#define get_vlc(s, vlc)            get_vlc_trace(s, (vlc)->table, (vlc)->bits, 3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
591
#define get_vlc2(s, tab, bits, max) get_vlc_trace(s, tab, bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)
592

    
593
#define tprintf(p, ...) av_log(p, AV_LOG_DEBUG, __VA_ARGS__)
594

    
595
#else //TRACE
596
#define tprintf(p, ...) {}
597
#endif
598

    
599
static inline int decode012(GetBitContext *gb){
600
    int n;
601
    n = get_bits1(gb);
602
    if (n == 0)
603
        return 0;
604
    else
605
        return get_bits1(gb) + 1;
606
}
607

    
608
static inline int decode210(GetBitContext *gb){
609
    if (get_bits1(gb))
610
        return 0;
611
    else
612
        return 2 - get_bits1(gb);
613
}
614

    
615
static inline int get_bits_left(GetBitContext *gb)
616
{
617
    return gb->size_in_bits - get_bits_count(gb);
618
}
619

    
620
#endif /* AVCODEC_GET_BITS_H */