quicktime/ffmpeg/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  * This library 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 of the License, or (at your option) any later version.
  10  *
  11  * This library 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 this library; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  *
  20  * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
  21  */
  22
  23 /**
  24  * @file bitstream.c
  25  * bitstream api.
  26  */
  27
  28 #include "avcodec.h"
  29 #include "bitstream.h"
  30
  31 void align_put_bits(PutBitContext *s)
  32 {
  33 #ifdef ALT_BITSTREAM_WRITER
  34     put_bits(s,(  - s->index) & 7,0);
  35 #else
  36     put_bits(s,s->bit_left & 7,0);
  37 #endif
  38 }
  39
  40 void put_string(PutBitContext * pbc, char *s, int put_zero)
  41 {
  42     while(*s){
  43         put_bits(pbc, 8, *s);
  44         s++;
  45     }
  46     if(put_zero)
  47         put_bits(pbc, 8, 0);
  48 }
  49
  50 /* bit input functions */
  51
  52 /**
  53  * reads 0-32 bits.
  54  */
  55 unsigned int get_bits_long(GetBitContext *s, int n){
  56     if(n<=17) return get_bits(s, n);
  57     else{
  58         int ret= get_bits(s, 16) << (n-16);
  59         return ret | get_bits(s, n-16);
  60     }
  61 }
  62
  63 /**
  64  * shows 0-32 bits.
  65  */
  66 unsigned int show_bits_long(GetBitContext *s, int n){
  67     if(n<=17) return show_bits(s, n);
  68     else{
  69         GetBitContext gb= *s;
  70         int ret= get_bits_long(s, n);
  71         *s= gb;
  72         return ret;
  73     }
  74 }
  75
  76 void align_get_bits(GetBitContext *s)
  77 {
  78     int n= (-get_bits_count(s)) & 7;
  79     if(n) skip_bits(s, n);
  80 }
  81
  82 int check_marker(GetBitContext *s, const char *msg)
  83 {
  84     int bit= get_bits1(s);
  85     if(!bit)
  86             av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
  87
  88     return bit;
  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         vlc->table_allocated += (1 << vlc->bits);
 119         if(use_static)
 120             vlc->table = av_realloc_static(vlc->table,
 121                                            sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
 122         else
 123             vlc->table = av_realloc(vlc->table,
 124                                     sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
 125         if (!vlc->table)
 126             return -1;
 127     }
 128     return index;
 129 }
 130
 131 static int build_table(VLC *vlc, int table_nb_bits,
 132                        int nb_codes,
 133                        const void *bits, int bits_wrap, int bits_size,
 134                        const void *codes, int codes_wrap, int codes_size,
 135                        uint32_t code_prefix, int n_prefix, int flags)
 136 {
 137     int i, j, k, n, table_size, table_index, nb, n1, index, code_prefix2;
 138     uint32_t code;
 139     VLC_TYPE (*table)[2];
 140
 141     table_size = 1 << table_nb_bits;
 142     table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_STATIC);
 143 #ifdef DEBUG_VLC
 144     printf("new table index=%d size=%d code_prefix=%x n=%d\n",
 145            table_index, table_size, code_prefix, n_prefix);
 146 #endif
 147     if (table_index < 0)
 148         return -1;
 149     table = &vlc->table[table_index];
 150
 151     for(i=0;i<table_size;i++) {
 152         table[i][1] = 0; //bits
 153         table[i][0] = -1; //codes
 154     }
 155
 156     /* first pass: map codes and compute auxillary table sizes */
 157     for(i=0;i<nb_codes;i++) {
 158         GET_DATA(n, bits, i, bits_wrap, bits_size);
 159         GET_DATA(code, codes, i, codes_wrap, codes_size);
 160         /* we accept tables with holes */
 161         if (n <= 0)
 162             continue;
 163 #if defined(DEBUG_VLC) && 0
 164         printf("i=%d n=%d code=0x%x\n", i, n, code);
 165 #endif
 166         /* if code matches the prefix, it is in the table */
 167         n -= n_prefix;
 168         if(flags & INIT_VLC_LE)
 169             code_prefix2= code & (n_prefix>=32 ? 0xffffffff : (1 << n_prefix)-1);
 170         else
 171             code_prefix2= code >> n;
 172         if (n > 0 && code_prefix2 == code_prefix) {
 173             if (n <= table_nb_bits) {
 174                 /* no need to add another table */
 175                 j = (code << (table_nb_bits - n)) & (table_size - 1);
 176                 nb = 1 << (table_nb_bits - n);
 177                 for(k=0;k<nb;k++) {
 178                     if(flags & INIT_VLC_LE)
 179                         j = (code >> n_prefix) + (k<<n);
 180 #ifdef DEBUG_VLC
 181                     av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n",
 182                            j, i, n);
 183 #endif
 184                     if (table[j][1] /*bits*/ != 0) {
 185                         av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
 186                         return -1;
 187                     }
 188                     table[j][1] = n; //bits
 189                     table[j][0] = i; //code
 190                     j++;
 191                 }
 192             } else {
 193                 n -= table_nb_bits;
 194                 j = (code >> ((flags & INIT_VLC_LE) ? n_prefix : n)) & ((1 << table_nb_bits) - 1);
 195 #ifdef DEBUG_VLC
 196                 printf("%4x: n=%d (subtable)\n",
 197                        j, n);
 198 #endif
 199                 /* compute table size */
 200                 n1 = -table[j][1]; //bits
 201                 if (n > n1)
 202                     n1 = n;
 203                 table[j][1] = -n1; //bits
 204             }
 205         }
 206     }
 207
 208     /* second pass : fill auxillary tables recursively */
 209     for(i=0;i<table_size;i++) {
 210         n = table[i][1]; //bits
 211         if (n < 0) {
 212             n = -n;
 213             if (n > table_nb_bits) {
 214                 n = table_nb_bits;
 215                 table[i][1] = -n; //bits
 216             }
 217             index = build_table(vlc, n, nb_codes,
 218                                 bits, bits_wrap, bits_size,
 219                                 codes, codes_wrap, codes_size,
 220                                 (flags & INIT_VLC_LE) ? (code_prefix | (i << n_prefix)) : ((code_prefix << table_nb_bits) | i),
 221                                 n_prefix + table_nb_bits, flags);
 222             if (index < 0)
 223                 return -1;
 224             /* note: realloc has been done, so reload tables */
 225             table = &vlc->table[table_index];
 226             table[i][0] = index; //code
 227         }
 228     }
 229     return table_index;
 230 }
 231
 232
 233 /* Build VLC decoding tables suitable for use with get_vlc().
 234
 235    'nb_bits' set thee decoding table size (2^nb_bits) entries. The
 236    bigger it is, the faster is the decoding. But it should not be too
 237    big to save memory and L1 cache. '9' is a good compromise.
 238
 239    'nb_codes' : number of vlcs codes
 240
 241    'bits' : table which gives the size (in bits) of each vlc code.
 242
 243    'codes' : table which gives the bit pattern of of each vlc code.
 244
 245    'xxx_wrap' : give the number of bytes between each entry of the
 246    'bits' or 'codes' tables.
 247
 248    'xxx_size' : gives the number of bytes of each entry of the 'bits'
 249    or 'codes' tables.
 250
 251    'wrap' and 'size' allows to use any memory configuration and types
 252    (byte/word/long) to store the 'bits' and 'codes' tables.
 253
 254    'use_static' should be set to 1 for tables, which should be freed
 255    with av_free_static(), 0 if free_vlc() will be used.
 256 */
 257 int init_vlc(VLC *vlc, int nb_bits, int nb_codes,
 258              const void *bits, int bits_wrap, int bits_size,
 259              const void *codes, int codes_wrap, int codes_size,
 260              int use_static)
 261 {
 262     vlc->bits = nb_bits;
 263     if(!use_static) {
 264         vlc->table = NULL;
 265         vlc->table_allocated = 0;
 266         vlc->table_size = 0;
 267     } else {
 268         /* Static tables are initially always NULL, return
 269            if vlc->table != NULL to avoid double allocation */
 270         if(vlc->table)
 271             return 0;
 272     }
 273
 274 #ifdef DEBUG_VLC
 275     printf("build table nb_codes=%d\n", nb_codes);
 276 #endif
 277
 278     if (build_table(vlc, nb_bits, nb_codes,
 279                     bits, bits_wrap, bits_size,
 280                     codes, codes_wrap, codes_size,
 281                     0, 0, use_static) < 0) {
 282         av_free(vlc->table);
 283         return -1;
 284     }
 285     return 0;
 286 }
 287
 288
 289 void free_vlc(VLC *vlc)
 290 {
 291     av_free(vlc->table);
 292 }
 293