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 void *ff_realloc_static(void *ptr, unsigned int size)
  46 {
  47     return av_realloc(ptr, size);
  48 }
  49
  50 void align_put_bits(PutBitContext *s)
  51 {
  52 #ifdef ALT_BITSTREAM_WRITER
  53     put_bits(s,(  - s->index) & 7,0);
  54 #else
  55     put_bits(s,s->bit_left & 7,0);
  56 #endif
  57 }
  58
  59 void ff_put_string(PutBitContext * pbc, const char *s, int put_zero)
  60 {
  61     while(*s){
  62         put_bits(pbc, 8, *s);
  63         s++;
  64     }
  65     if(put_zero)
  66         put_bits(pbc, 8, 0);
  67 }
  68
  69 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
  70 {
  71     const uint16_t *srcw= (const uint16_t*)src;
  72     int words= length>>4;
  73     int bits= length&15;
  74     int i;
  75
  76     if(length==0) return;
  77
  78     if(ENABLE_SMALL || words < 16 || put_bits_count(pb)&7){
  79         for(i=0; i<words; i++) put_bits(pb, 16, be2me_16(srcw[i]));
  80     }else{
  81         for(i=0; put_bits_count(pb)&31; i++)
  82             put_bits(pb, 8, src[i]);
  83         flush_put_bits(pb);
  84         memcpy(pbBufPtr(pb), src+i, 2*words-i);
  85         skip_put_bytes(pb, 2*words-i);
  86     }
  87
  88     put_bits(pb, bits, be2me_16(srcw[words])>>(16-bits));
  89 }
  90
  91 /* VLC decoding */
  92
  93 //#define DEBUG_VLC
  94
  95 #define GET_DATA(v, table, i, wrap, size) \
  96 {\
  97     const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
  98     switch(size) {\
  99     case 1:\
 100         v = *(const uint8_t *)ptr;\
 101         break;\
 102     case 2:\
 103         v = *(const uint16_t *)ptr;\
 104         break;\
 105     default:\
 106         v = *(const uint32_t *)ptr;\
 107         break;\
 108     }\
 109 }
 110
 111
 112 static int alloc_table(VLC *vlc, int size, int use_static)
 113 {
 114     int index;
 115     index = vlc->table_size;
 116     vlc->table_size += size;
 117     if (vlc->table_size > vlc->table_allocated) {
 118         if(use_static>1)
 119             abort(); //cant do anything, init_vlc() is used with too little memory
 120         vlc->table_allocated += (1 << vlc->bits);
 121         if(use_static)
 122             vlc->table = ff_realloc_static(vlc->table,
 123                                            sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
 124         else
 125             vlc->table = av_realloc(vlc->table,
 126                                     sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
 127         if (!vlc->table)
 128             return -1;
 129     }
 130     return index;
 131 }
 132
 133 static int build_table(VLC *vlc, int table_nb_bits,
 134                        int nb_codes,
 135                        const void *bits, int bits_wrap, int bits_size,
 136                        const void *codes, int codes_wrap, int codes_size,
 137                        const void *symbols, int symbols_wrap, int symbols_size,
 138                        uint32_t code_prefix, int n_prefix, int flags)
 139 {
 140     int i, j, k, n, table_size, table_index, nb, n1, index, code_prefix2, symbol;
 141     uint32_t code;
 142     VLC_TYPE (*table)[2];
 143
 144     table_size = 1 << table_nb_bits;
 145     table_index = alloc_table(vlc, table_size, flags & (INIT_VLC_USE_STATIC|INIT_VLC_USE_NEW_STATIC));
 146 #ifdef DEBUG_VLC
 147     av_log(NULL,AV_LOG_DEBUG,"new table index=%d size=%d code_prefix=%x n=%d\n",
 148            table_index, table_size, code_prefix, n_prefix);
 149 #endif
 150     if (table_index < 0)
 151         return -1;
 152     table = &vlc->table[table_index];
 153
 154     for(i=0;i<table_size;i++) {
 155         table[i][1] = 0; //bits
 156         table[i][0] = -1; //codes
 157     }
 158
 159     /* first pass: map codes and compute auxillary table sizes */
 160     for(i=0;i<nb_codes;i++) {
 161         GET_DATA(n, bits, i, bits_wrap, bits_size);
 162         GET_DATA(code, codes, i, codes_wrap, codes_size);
 163         /* we accept tables with holes */
 164         if (n <= 0)
 165             continue;
 166         if (!symbols)
 167             symbol = i;
 168         else
 169             GET_DATA(symbol, symbols, i, symbols_wrap, symbols_size);
 170 #if defined(DEBUG_VLC) && 0
 171         av_log(NULL,AV_LOG_DEBUG,"i=%d n=%d code=0x%x\n", i, n, code);
 172 #endif
 173         /* if code matches the prefix, it is in the table */
 174         n -= n_prefix;
 175         if(flags & INIT_VLC_LE)
 176             code_prefix2= code & (n_prefix>=32 ? 0xffffffff : (1 << n_prefix)-1);
 177         else
 178             code_prefix2= code >> n;
 179         if (n > 0 && code_prefix2 == code_prefix) {
 180             if (n <= table_nb_bits) {
 181                 /* no need to add another table */
 182                 j = (code << (table_nb_bits - n)) & (table_size - 1);
 183                 nb = 1 << (table_nb_bits - n);
 184                 for(k=0;k<nb;k++) {
 185                     if(flags & INIT_VLC_LE)
 186                         j = (code >> n_prefix) + (k<<n);
 187 #ifdef DEBUG_VLC
 188                     av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n",
 189                            j, i, n);
 190 #endif
 191                     if (table[j][1] /*bits*/ != 0) {
 192                         av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
 193                         return -1;
 194                     }
 195                     table[j][1] = n; //bits
 196                     table[j][0] = symbol;
 197                     j++;
 198                 }
 199             } else {
 200                 n -= table_nb_bits;
 201                 j = (code >> ((flags & INIT_VLC_LE) ? n_prefix : n)) & ((1 << table_nb_bits) - 1);
 202 #ifdef DEBUG_VLC
 203                 av_log(NULL,AV_LOG_DEBUG,"%4x: n=%d (subtable)\n",
 204                        j, n);
 205 #endif
 206                 /* compute table size */
 207                 n1 = -table[j][1]; //bits
 208                 if (n > n1)
 209                     n1 = n;
 210                 table[j][1] = -n1; //bits
 211             }
 212         }
 213     }
 214
 215     /* second pass : fill auxillary tables recursively */
 216     for(i=0;i<table_size;i++) {
 217         n = table[i][1]; //bits
 218         if (n < 0) {
 219             n = -n;
 220             if (n > table_nb_bits) {
 221                 n = table_nb_bits;
 222                 table[i][1] = -n; //bits
 223             }
 224             index = build_table(vlc, n, nb_codes,
 225                                 bits, bits_wrap, bits_size,
 226                                 codes, codes_wrap, codes_size,
 227                                 symbols, symbols_wrap, symbols_size,
 228                                 (flags & INIT_VLC_LE) ? (code_prefix | (i << n_prefix)) : ((code_prefix << table_nb_bits) | i),
 229                                 n_prefix + table_nb_bits, flags);
 230             if (index < 0)
 231                 return -1;
 232             /* note: realloc has been done, so reload tables */
 233             table = &vlc->table[table_index];
 234             table[i][0] = index; //code
 235         }
 236     }
 237     return table_index;
 238 }
 239
 240
 241 /* Build VLC decoding tables suitable for use with get_vlc().
 242
 243    'nb_bits' set thee decoding table size (2^nb_bits) entries. The
 244    bigger it is, the faster is the decoding. But it should not be too
 245    big to save memory and L1 cache. '9' is a good compromise.
 246
 247    'nb_codes' : number of vlcs codes
 248
 249    'bits' : table which gives the size (in bits) of each vlc code.
 250
 251    'codes' : table which gives the bit pattern of of each vlc code.
 252
 253    'symbols' : table which gives the values to be returned from get_vlc().
 254
 255    'xxx_wrap' : give the number of bytes between each entry of the
 256    'bits' or 'codes' tables.
 257
 258    'xxx_size' : gives the number of bytes of each entry of the 'bits'
 259    or 'codes' tables.
 260
 261    'wrap' and 'size' allows to use any memory configuration and types
 262    (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
 263
 264    'use_static' should be set to 1 for tables, which should be freed
 265    with av_free_static(), 0 if free_vlc() will be used.
 266 */
 267 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
 268              const void *bits, int bits_wrap, int bits_size,
 269              const void *codes, int codes_wrap, int codes_size,
 270              const void *symbols, int symbols_wrap, int symbols_size,
 271              int flags)
 272 {
 273     vlc->bits = nb_bits;
 274     if(flags & INIT_VLC_USE_NEW_STATIC){
 275         if(vlc->table_size && vlc->table_size == vlc->table_allocated){
 276             return 0;
 277         }else if(vlc->table_size){
 278             abort(); // fatal error, we are called on a partially initialized table
 279         }
 280     }else if(!(flags & INIT_VLC_USE_STATIC)) {
 281         vlc->table = NULL;
 282         vlc->table_allocated = 0;
 283         vlc->table_size = 0;
 284     } else {
 285         /* Static tables are initially always NULL, return
 286            if vlc->table != NULL to avoid double allocation */
 287         if(vlc->table)
 288             return 0;
 289     }
 290
 291 #ifdef DEBUG_VLC
 292     av_log(NULL,AV_LOG_DEBUG,"build table nb_codes=%d\n", nb_codes);
 293 #endif
 294
 295     if (build_table(vlc, nb_bits, nb_codes,
 296                     bits, bits_wrap, bits_size,
 297                     codes, codes_wrap, codes_size,
 298                     symbols, symbols_wrap, symbols_size,
 299                     0, 0, flags) < 0) {
 300         av_freep(&vlc->table);
 301         return -1;
 302     }
 303     if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated)
 304         av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
 305     return 0;
 306 }
 307
 308
 309 void free_vlc(VLC *vlc)
 310 {
 311     av_freep(&vlc->table);
 312 }
 313