libavcodec/bitstream.c

   1 /*
   2  * Common bit i/o utils
   3  * Copyright (c) 2000, 2001 Fabrice Bellard.
   4  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
   5  *
   6  * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
   7  *
   8  * This file is part of FFmpeg.
   9  *
  10  * FFmpeg is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU Lesser General Public
  12  * License as published by the Free Software Foundation; either
  13  * version 2.1 of the License, or (at your option) any later version.
  14  *
  15  * FFmpeg is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  * Lesser General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public
  21  * License along with FFmpeg; if not, write to the Free Software
  22  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  23  */
  24
  25 /**
  26  * @file bitstream.c
  27  * bitstream api.
  28  */
  29
  30 #include "avcodec.h"
  31 #include "bitstream.h"
  32
  33 /**
  34  * Same as av_mallocz_static(), but does a realloc.
  35  *
  36  * @param[in] ptr The block of memory to reallocate.
  37  * @param[in] size The requested size.
  38  * @return Block of memory of requested size.
  39  * @deprecated. Code which uses ff_realloc_static is broken/misdesigned
  40  * and should correctly use static arrays
  41  */
  42 attribute_deprecated av_alloc_size(2)
  43 static void *ff_realloc_static(void *ptr, unsigned int size);
  44
  45 static unsigned int last_static = 0;
  46 static unsigned int allocated_static = 0;
  47 static void** array_static = NULL;
  48
  49 static void *av_mallocz_static(unsigned int size)
  50 {
  51     void *ptr = av_mallocz(size);
  52
  53     if(ptr){
  54         array_static =av_fast_realloc(array_static, &allocated_static, sizeof(void*)*(last_static+1));
  55         if(!array_static)
  56             return NULL;
  57         array_static[last_static++] = ptr;
  58     }
  59
  60     return ptr;
  61 }
  62
  63 static void *ff_realloc_static(void *ptr, unsigned int size)
  64 {
  65     int i;
  66     if(!ptr)
  67       return av_mallocz_static(size);
  68     /* Look for the old ptr */
  69     for(i = 0; i < last_static; i++) {
  70         if(array_static[i] == ptr) {
  71             array_static[i] = av_realloc(array_static[i], size);
  72             return array_static[i];
  73         }
  74     }
  75     return NULL;
  76
  77 }
  78
  79 static void av_free_static(void)
  80 {
  81     while(last_static){
  82         av_freep(&array_static[--last_static]);
  83     }
  84     av_freep(&array_static);
  85 }
  86
  87 /**
  88  * Call av_free_static automatically before it's too late
  89  */
  90
  91 static void do_free(void) __attribute__ ((destructor));
  92
  93 static void do_free(void)
  94 {
  95     av_free_static();
  96 }
  97
  98
  99 void align_put_bits(PutBitContext *s)
 100 {
 101 #ifdef ALT_BITSTREAM_WRITER
 102     put_bits(s,(  - s->index) & 7,0);
 103 #else
 104     put_bits(s,s->bit_left & 7,0);
 105 #endif
 106 }
 107
 108 void ff_put_string(PutBitContext * pbc, const char *s, int put_zero)
 109 {
 110     while(*s){
 111         put_bits(pbc, 8, *s);
 112         s++;
 113     }
 114     if(put_zero)
 115         put_bits(pbc, 8, 0);
 116 }
 117
 118 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
 119 {
 120     const uint16_t *srcw= (const uint16_t*)src;
 121     int words= length>>4;
 122     int bits= length&15;
 123     int i;
 124
 125     if(length==0) return;
 126
 127     if(ENABLE_SMALL || words < 16 || put_bits_count(pb)&7){
 128         for(i=0; i<words; i++) put_bits(pb, 16, be2me_16(srcw[i]));
 129     }else{
 130         for(i=0; put_bits_count(pb)&31; i++)
 131             put_bits(pb, 8, src[i]);
 132         flush_put_bits(pb);
 133         memcpy(pbBufPtr(pb), src+i, 2*words-i);
 134         skip_put_bytes(pb, 2*words-i);
 135     }
 136
 137     put_bits(pb, bits, be2me_16(srcw[words])>>(16-bits));
 138 }
 139
 140 /* VLC decoding */
 141
 142 //#define DEBUG_VLC
 143
 144 #define GET_DATA(v, table, i, wrap, size) \
 145 {\
 146     const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
 147     switch(size) {\
 148     case 1:\
 149         v = *(const uint8_t *)ptr;\
 150         break;\
 151     case 2:\
 152         v = *(const uint16_t *)ptr;\
 153         break;\
 154     default:\
 155         v = *(const uint32_t *)ptr;\
 156         break;\
 157     }\
 158 }
 159
 160
 161 static int alloc_table(VLC *vlc, int size, int use_static)
 162 {
 163     int index;
 164     index = vlc->table_size;
 165     vlc->table_size += size;
 166     if (vlc->table_size > vlc->table_allocated) {
 167         if(use_static>1)
 168             abort(); //cant do anything, init_vlc() is used with too little memory
 169         vlc->table_allocated += (1 << vlc->bits);
 170         if(use_static)
 171             vlc->table = ff_realloc_static(vlc->table,
 172                                            sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
 173         else
 174             vlc->table = av_realloc(vlc->table,
 175                                     sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
 176         if (!vlc->table)
 177             return -1;
 178     }
 179     return index;
 180 }
 181
 182 static int build_table(VLC *vlc, int table_nb_bits,
 183                        int nb_codes,
 184                        const void *bits, int bits_wrap, int bits_size,
 185                        const void *codes, int codes_wrap, int codes_size,
 186                        const void *symbols, int symbols_wrap, int symbols_size,
 187                        uint32_t code_prefix, int n_prefix, int flags)
 188 {
 189     int i, j, k, n, table_size, table_index, nb, n1, index, code_prefix2, symbol;
 190     uint32_t code;
 191     VLC_TYPE (*table)[2];
 192
 193     table_size = 1 << table_nb_bits;
 194     table_index = alloc_table(vlc, table_size, flags & (INIT_VLC_USE_STATIC|INIT_VLC_USE_NEW_STATIC));
 195 #ifdef DEBUG_VLC
 196     av_log(NULL,AV_LOG_DEBUG,"new table index=%d size=%d code_prefix=%x n=%d\n",
 197            table_index, table_size, code_prefix, n_prefix);
 198 #endif
 199     if (table_index < 0)
 200         return -1;
 201     table = &vlc->table[table_index];
 202
 203     for(i=0;i<table_size;i++) {
 204         table[i][1] = 0; //bits
 205         table[i][0] = -1; //codes
 206     }
 207
 208     /* first pass: map codes and compute auxillary table sizes */
 209     for(i=0;i<nb_codes;i++) {
 210         GET_DATA(n, bits, i, bits_wrap, bits_size);
 211         GET_DATA(code, codes, i, codes_wrap, codes_size);
 212         /* we accept tables with holes */
 213         if (n <= 0)
 214             continue;
 215         if (!symbols)
 216             symbol = i;
 217         else
 218             GET_DATA(symbol, symbols, i, symbols_wrap, symbols_size);
 219 #if defined(DEBUG_VLC) && 0
 220         av_log(NULL,AV_LOG_DEBUG,"i=%d n=%d code=0x%x\n", i, n, code);
 221 #endif
 222         /* if code matches the prefix, it is in the table */
 223         n -= n_prefix;
 224         if(flags & INIT_VLC_LE)
 225             code_prefix2= code & (n_prefix>=32 ? 0xffffffff : (1 << n_prefix)-1);
 226         else
 227             code_prefix2= code >> n;
 228         if (n > 0 && code_prefix2 == code_prefix) {
 229             if (n <= table_nb_bits) {
 230                 /* no need to add another table */
 231                 j = (code << (table_nb_bits - n)) & (table_size - 1);
 232                 nb = 1 << (table_nb_bits - n);
 233                 for(k=0;k<nb;k++) {
 234                     if(flags & INIT_VLC_LE)
 235                         j = (code >> n_prefix) + (k<<n);
 236 #ifdef DEBUG_VLC
 237                     av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n",
 238                            j, i, n);
 239 #endif
 240                     if (table[j][1] /*bits*/ != 0) {
 241                         av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
 242                         return -1;
 243                     }
 244                     table[j][1] = n; //bits
 245                     table[j][0] = symbol;
 246                     j++;
 247                 }
 248             } else {
 249                 n -= table_nb_bits;
 250                 j = (code >> ((flags & INIT_VLC_LE) ? n_prefix : n)) & ((1 << table_nb_bits) - 1);
 251 #ifdef DEBUG_VLC
 252                 av_log(NULL,AV_LOG_DEBUG,"%4x: n=%d (subtable)\n",
 253                        j, n);
 254 #endif
 255                 /* compute table size */
 256                 n1 = -table[j][1]; //bits
 257                 if (n > n1)
 258                     n1 = n;
 259                 table[j][1] = -n1; //bits
 260             }
 261         }
 262     }
 263
 264     /* second pass : fill auxillary tables recursively */
 265     for(i=0;i<table_size;i++) {
 266         n = table[i][1]; //bits
 267         if (n < 0) {
 268             n = -n;
 269             if (n > table_nb_bits) {
 270                 n = table_nb_bits;
 271                 table[i][1] = -n; //bits
 272             }
 273             index = build_table(vlc, n, nb_codes,
 274                                 bits, bits_wrap, bits_size,
 275                                 codes, codes_wrap, codes_size,
 276                                 symbols, symbols_wrap, symbols_size,
 277                                 (flags & INIT_VLC_LE) ? (code_prefix | (i << n_prefix)) : ((code_prefix << table_nb_bits) | i),
 278                                 n_prefix + table_nb_bits, flags);
 279             if (index < 0)
 280                 return -1;
 281             /* note: realloc has been done, so reload tables */
 282             table = &vlc->table[table_index];
 283             table[i][0] = index; //code
 284         }
 285     }
 286     return table_index;
 287 }
 288
 289
 290 /* Build VLC decoding tables suitable for use with get_vlc().
 291
 292    'nb_bits' set thee decoding table size (2^nb_bits) entries. The
 293    bigger it is, the faster is the decoding. But it should not be too
 294    big to save memory and L1 cache. '9' is a good compromise.
 295
 296    'nb_codes' : number of vlcs codes
 297
 298    'bits' : table which gives the size (in bits) of each vlc code.
 299
 300    'codes' : table which gives the bit pattern of of each vlc code.
 301
 302    'symbols' : table which gives the values to be returned from get_vlc().
 303
 304    'xxx_wrap' : give the number of bytes between each entry of the
 305    'bits' or 'codes' tables.
 306
 307    'xxx_size' : gives the number of bytes of each entry of the 'bits'
 308    or 'codes' tables.
 309
 310    'wrap' and 'size' allows to use any memory configuration and types
 311    (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
 312
 313    'use_static' should be set to 1 for tables, which should be freed
 314    with av_free_static(), 0 if free_vlc() will be used.
 315 */
 316 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
 317              const void *bits, int bits_wrap, int bits_size,
 318              const void *codes, int codes_wrap, int codes_size,
 319              const void *symbols, int symbols_wrap, int symbols_size,
 320              int flags)
 321 {
 322     vlc->bits = nb_bits;
 323     if(flags & INIT_VLC_USE_NEW_STATIC){
 324         if(vlc->table_size && vlc->table_size == vlc->table_allocated){
 325             return 0;
 326         }else if(vlc->table_size){
 327             abort(); // fatal error, we are called on a partially initialized table
 328         }
 329     }else if(!(flags & INIT_VLC_USE_STATIC)) {
 330         vlc->table = NULL;
 331         vlc->table_allocated = 0;
 332         vlc->table_size = 0;
 333     } else {
 334         /* Static tables are initially always NULL, return
 335            if vlc->table != NULL to avoid double allocation */
 336         if(vlc->table)
 337             return 0;
 338     }
 339
 340 #ifdef DEBUG_VLC
 341     av_log(NULL,AV_LOG_DEBUG,"build table nb_codes=%d\n", nb_codes);
 342 #endif
 343
 344     if (build_table(vlc, nb_bits, nb_codes,
 345                     bits, bits_wrap, bits_size,
 346                     codes, codes_wrap, codes_size,
 347                     symbols, symbols_wrap, symbols_size,
 348                     0, 0, flags) < 0) {
 349         av_freep(&vlc->table);
 350         return -1;
 351     }
 352     if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated)
 353         av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
 354     return 0;
 355 }
 356
 357
 358 void free_vlc(VLC *vlc)
 359 {
 360     av_freep(&vlc->table);
 361 }
 362