apps/codecs/lib/ffmpeg_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 #include "ffmpeg_bitstream.h"
  26
  27 #ifdef ROCKBOX
  28 #undef DEBUGF
  29 #define DEBUGF(...)
  30 #endif
  31
  32 const uint8_t ff_log2_run[32]={
  33  0, 0, 0, 0, 1, 1, 1, 1,
  34  2, 2, 2, 2, 3, 3, 3, 3,
  35  4, 4, 5, 5, 6, 6, 7, 7,
  36  8, 9,10,11,12,13,14,15
  37 };
  38
  39 /**
  40  * Same as av_mallocz_static(), but does a realloc.
  41  *
  42  * @param[in] ptr The block of memory to reallocate.
  43  * @param[in] size The requested size.
  44  * @return Block of memory of requested size.
  45  * @deprecated. Code which uses ff_realloc_static is broken/misdesigned
  46  * and should correctly use static arrays
  47  */
  48
  49
  50 void ff_put_string(PutBitContext * pbc, const char *s, int put_zero)
  51 {
  52     while(*s){
  53         put_bits(pbc, 8, *s);
  54         s++;
  55     }
  56     if(put_zero)
  57         put_bits(pbc, 8, 0);
  58 }
  59
  60 /* VLC decoding */
  61
  62 //#define DEBUG_VLC
  63
  64 #define GET_DATA(v, table, i, wrap, size) \
  65 {\
  66     const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
  67     switch(size) {\
  68     case 1:\
  69         v = *(const uint8_t *)ptr;\
  70         break;\
  71     case 2:\
  72         v = *(const uint16_t *)ptr;\
  73         break;\
  74     default:\
  75         v = *(const uint32_t *)ptr;\
  76         break;\
  77     }\
  78 }
  79
  80
  81 static int alloc_table(VLC *vlc, int size, int use_static)
  82 {
  83     int index;
  84     index = vlc->table_size;
  85     vlc->table_size += size;
  86     if (vlc->table_size > vlc->table_allocated) {
  87         if(use_static>1){
  88             DEBUGF("init_vlc() used with too little memory : table_size > allocated_memory\n");
  89         }
  90
  91         if (!vlc->table)
  92             return -1;
  93     }
  94     return index;
  95 }
  96
  97 static int build_table(VLC *vlc, int table_nb_bits,
  98                        int nb_codes,
  99                        const void *bits, int bits_wrap, int bits_size,
 100                        const void *codes, int codes_wrap, int codes_size,
 101                        const void *symbols, int symbols_wrap, int symbols_size,
 102                        uint32_t code_prefix, int n_prefix, int flags)
 103 {
 104     int i, j, k, n, table_size, table_index, nb, n1, index, code_prefix2, symbol;
 105     uint32_t code;
 106     VLC_TYPE (*table)[2];
 107
 108     table_size = 1 << table_nb_bits;
 109     table_index = alloc_table(vlc, table_size, flags & (INIT_VLC_USE_STATIC|INIT_VLC_USE_NEW_STATIC));
 110 #ifdef DEBUG_VLC
 111     DEBUGF("new table index=%d size=%d code_prefix=%x n=%d\n",
 112            table_index, table_size, code_prefix, n_prefix);
 113 #endif
 114     if (table_index < 0)
 115         return -1;
 116     table = &vlc->table[table_index];
 117
 118     for(i=0;i<table_size;i++) {
 119         table[i][1] = 0; //bits
 120         table[i][0] = -1; //codes
 121     }
 122
 123     /* first pass: map codes and compute auxillary table sizes */
 124     for(i=0;i<nb_codes;i++) {
 125         GET_DATA(n, bits, i, bits_wrap, bits_size);
 126         GET_DATA(code, codes, i, codes_wrap, codes_size);
 127         /* we accept tables with holes */
 128         if (n <= 0)
 129             continue;
 130         if (!symbols)
 131             symbol = i;
 132         else
 133             GET_DATA(symbol, symbols, i, symbols_wrap, symbols_size);
 134 #if defined(DEBUG_VLC) && 0
 135         DEBUGF("i=%d n=%d code=0x%x\n", i, n, code);
 136 #endif
 137         /* if code matches the prefix, it is in the table */
 138         n -= n_prefix;
 139         if(flags & INIT_VLC_LE)
 140             code_prefix2= code & (n_prefix>=32 ? (int)0xffffffff : (1 << n_prefix)-1);
 141         else
 142             code_prefix2= code >> n;
 143         if (n > 0 && code_prefix2 == (int)code_prefix) {
 144             if (n <= table_nb_bits) {
 145                 /* no need to add another table */
 146                 j = (code << (table_nb_bits - n)) & (table_size - 1);
 147                 nb = 1 << (table_nb_bits - n);
 148                 for(k=0;k<nb;k++) {
 149                     if(flags & INIT_VLC_LE)
 150                         j = (code >> n_prefix) + (k<<n);
 151 #ifdef DEBUG_VLC
 152                     DEBUGF("%4x: code=%d n=%d\n",
 153                            j, i, n);
 154 #endif
 155                     if (table[j][1] /*bits*/ != 0) {
 156                         DEBUGF("incorrect codes\n");
 157                         return -1;
 158                     }
 159                     table[j][1] = n; //bits
 160                     table[j][0] = symbol;
 161                     j++;
 162                 }
 163             } else {
 164                 n -= table_nb_bits;
 165                 j = (code >> ((flags & INIT_VLC_LE) ? n_prefix : n)) & ((1 << table_nb_bits) - 1);
 166 #ifdef DEBUG_VLC
 167                 DEBUGF("%4x: n=%d (subtable)\n",
 168                        j, n);
 169 #endif
 170                 /* compute table size */
 171                 n1 = -table[j][1]; //bits
 172                 if (n > n1)
 173                     n1 = n;
 174                 table[j][1] = -n1; //bits
 175             }
 176         }
 177     }
 178
 179     /* second pass : fill auxillary tables recursively */
 180     for(i=0;i<table_size;i++) {
 181         n = table[i][1]; //bits
 182         if (n < 0) {
 183             n = -n;
 184             if (n > table_nb_bits) {
 185                 n = table_nb_bits;
 186                 table[i][1] = -n; //bits
 187             }
 188             index = build_table(vlc, n, nb_codes,
 189                                 bits, bits_wrap, bits_size,
 190                                 codes, codes_wrap, codes_size,
 191                                 symbols, symbols_wrap, symbols_size,
 192                                 (flags & INIT_VLC_LE) ? (code_prefix | (i << n_prefix)) : ((code_prefix << table_nb_bits) | i),
 193                                 n_prefix + table_nb_bits, flags);
 194             if (index < 0)
 195                 return -1;
 196             /* note: realloc has been done, so reload tables */
 197             table = &vlc->table[table_index];
 198             table[i][0] = index; //code
 199         }
 200     }
 201     return table_index;
 202 }
 203
 204
 205 /* Build VLC decoding tables suitable for use with get_vlc().
 206
 207    'nb_bits' set thee decoding table size (2^nb_bits) entries. The
 208    bigger it is, the faster is the decoding. But it should not be too
 209    big to save memory and L1 cache. '9' is a good compromise.
 210
 211    'nb_codes' : number of vlcs codes
 212
 213    'bits' : table which gives the size (in bits) of each vlc code.
 214
 215    'codes' : table which gives the bit pattern of of each vlc code.
 216
 217    'symbols' : table which gives the values to be returned from get_vlc().
 218
 219    'xxx_wrap' : give the number of bytes between each entry of the
 220    'bits' or 'codes' tables.
 221
 222    'xxx_size' : gives the number of bytes of each entry of the 'bits'
 223    or 'codes' tables.
 224
 225    'wrap' and 'size' allows to use any memory configuration and types
 226    (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
 227
 228    'use_static' should be set to 1 for tables, which should be freed
 229    with av_free_static(), 0 if free_vlc() will be used.
 230 */
 231 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
 232              const void *bits, int bits_wrap, int bits_size,
 233              const void *codes, int codes_wrap, int codes_size,
 234              const void *symbols, int symbols_wrap, int symbols_size,
 235              int flags)
 236 {
 237     vlc->bits = nb_bits;
 238     if(flags & INIT_VLC_USE_NEW_STATIC){
 239         if(vlc->table_size && vlc->table_size == vlc->table_allocated){
 240             return 0;
 241         }else if(vlc->table_size){
 242             return -1; // fatal error, we are called on a partially initialized table
 243         }
 244     }else if(!(flags & INIT_VLC_USE_STATIC)) {
 245         vlc->table = NULL;
 246         vlc->table_allocated = 0;
 247         vlc->table_size = 0;
 248     } else {
 249         /* Static tables are initially always NULL, return
 250            if vlc->table != NULL to avoid double allocation */
 251         if(vlc->table)
 252             return 0;
 253     }
 254
 255 #ifdef DEBUG_VLC
 256     DEBUGF("build table nb_codes=%d\n", nb_codes);
 257 #endif
 258
 259     if (build_table(vlc, nb_bits, nb_codes,
 260                     bits, bits_wrap, bits_size,
 261                     codes, codes_wrap, codes_size,
 262                     symbols, symbols_wrap, symbols_size,
 263                     0, 0, flags) < 0) {
 264         //free(&vlc->table);
 265         return -1;
 266     }
 267     /* Changed the following condition to be true if table_size > table_allocated. *
 268      * This would be more sensible for static tables since we want warnings for    *
 269      * memory shortages only.                                                      */
 270 #ifdef TEST
 271     if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size > vlc->table_allocated)
 272         DEBUGF("needed %d had %d\n", vlc->table_size, vlc->table_allocated);
 273 #endif
 274     return 0;
 275 }
 276