bitstream.c

   1 /*
   2  * Common bit I/O utils.
   3  *
   4  * Extracted 2009 from mplayer 2009-02-10 libavcodec/bitstream.c.
   5  *
   6  * Copyright (c) 2000, 2001 Fabrice Bellard
   7  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
   8  * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
   9  *
  10  * Licensed under the GNU Lesser General Public License.
  11  * For licencing details see COPYING.LIB.
  12  */
  13
  14 /**
  15  * \file bitstream.c Bitstream API.
  16  */
  17
  18 #include <stdlib.h>
  19 #include <inttypes.h>
  20 #include <stdio.h>
  21 #include <string.h>
  22 #include <regex.h>
  23
  24 #include "para.h"
  25 #include "error.h"
  26 #include "string.h"
  27 #include "wma.h"
  28 #include "bitstream.h"
  29
  30 #define GET_DATA(v, table, i, wrap, size) \
  31 {\
  32     const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
  33     switch(size) {\
  34     case 1:\
  35         v = *(const uint8_t *)ptr;\
  36         break;\
  37     case 2:\
  38         v = *(const uint16_t *)ptr;\
  39         break;\
  40     default:\
  41         v = *(const uint32_t *)ptr;\
  42         break;\
  43     }\
  44 }
  45
  46 static int alloc_table(struct vlc *vlc, int size)
  47 {
  48         int idx;
  49
  50         idx = vlc->table_size;
  51         vlc->table_size += size;
  52         if (vlc->table_size > vlc->table_allocated) {
  53                 vlc->table_allocated += (1 << vlc->bits);
  54                 vlc->table = realloc(vlc->table,
  55                         sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
  56                 if (!vlc->table)
  57                         return -E_TABLE_ALLOC;
  58         }
  59         return idx;
  60 }
  61
  62 static int build_table(struct vlc *vlc, int table_nb_bits,
  63                 int nb_codes, const void *bits, int bits_wrap, int bits_size,
  64                 const void *codes, int codes_wrap, int codes_size,
  65                 uint32_t code_prefix, int n_prefix)
  66 {
  67         int ret, i, j, k, n, table_size, table_index, nb, n1, idx, code_prefix2,
  68                 symbol;
  69         uint32_t code;
  70         VLC_TYPE(*table)[2];
  71
  72         table_size = 1 << table_nb_bits;
  73         ret = alloc_table(vlc, table_size);
  74         if (ret < 0)
  75                 return ret;
  76         table_index = ret;
  77         table = &vlc->table[table_index];
  78
  79         for (i = 0; i < table_size; i++) {
  80                 table[i][1] = 0;        //bits
  81                 table[i][0] = -1;       //codes
  82         }
  83
  84         /* first pass: map codes and compute auxillary table sizes */
  85         for (i = 0; i < nb_codes; i++) {
  86                 GET_DATA(n, bits, i, bits_wrap, bits_size);
  87                 GET_DATA(code, codes, i, codes_wrap, codes_size);
  88                 /* we accept tables with holes */
  89                 if (n <= 0)
  90                         continue;
  91                 symbol = i;
  92                 /* if code matches the prefix, it is in the table */
  93                 n -= n_prefix;
  94                 code_prefix2 = code >> n;
  95                 if (n > 0 && code_prefix2 == code_prefix) {
  96                         if (n <= table_nb_bits) {
  97                                 /* no need to add another table */
  98                                 j = (code << (table_nb_bits - n)) & (table_size - 1);
  99                                 nb = 1 << (table_nb_bits - n);
 100                                 for (k = 0; k < nb; k++) {
 101                                         if (table[j][1] /* bits */ != 0)
 102                                                 return -E_BAD_CODES;
 103                                         table[j][1] = n;        //bits
 104                                         table[j][0] = symbol;
 105                                         j++;
 106                                 }
 107                         } else {
 108                                 n -= table_nb_bits;
 109                                 j = (code >> n) & ((1 << table_nb_bits) - 1);
 110                                 /* compute table size */
 111                                 n1 = -table[j][1];      //bits
 112                                 if (n > n1)
 113                                         n1 = n;
 114                                 table[j][1] = -n1;      //bits
 115                         }
 116                 }
 117         }
 118
 119         /* second pass : fill auxillary tables recursively */
 120         for (i = 0; i < table_size; i++) {
 121                 n = table[i][1];        //bits
 122                 if (n < 0) {
 123                         n = -n;
 124                         if (n > table_nb_bits) {
 125                                 n = table_nb_bits;
 126                                 table[i][1] = -n;       //bits
 127                         }
 128                         ret = build_table(vlc, n, nb_codes,
 129                                 bits, bits_wrap, bits_size,
 130                                 codes, codes_wrap, codes_size,
 131                                 (code_prefix << table_nb_bits) | i,
 132                                 n_prefix + table_nb_bits);
 133                         if (ret < 0)
 134                                 return ret;
 135                         idx = ret;
 136                         /* note: realloc has been done, so reload tables */
 137                         table = &vlc->table[table_index];
 138                         table[i][0] = idx;      //code
 139                 }
 140         }
 141         return table_index;
 142 }
 143
 144 /**
 145  * Build VLC decoding tables suitable for use with get_vlc().
 146  *
 147  * \param nb_bits Set the decoding table size (2^nb_bits)
 148  * entries. The bigger it is, the faster is the decoding. But
 149  * it should not be too big to save memory and L1 cache. '9'
 150  * is a good compromise.
 151  *
 152  * \param nb_codes Number of vlcs codes.
 153  *
 154  * \param bits Table which gives the size (in bits) of each
 155  * vlc code.
 156  *
 157  * \param codes Table which gives the bit pattern of of each
 158  * vlc code.
 159  *
 160  * \param bits_wrap The number of bytes between each entry of the
 161  * 'bits' or 'codes' tables.
 162  *
 163  *
 164  * \param bits_size The number of bytes of each entry of the
 165  * 'bits' or 'codes' tables.
 166  *
 167  * \param codes_wrap Same as bits_wrap but uses the 'codes' table.
 168  * \param codes_size Same as bits_size but for the 'codes' table.
 169  *
 170  * The wrap and size parameters allow to use any memory configuration and
 171  * types (byte/word/long) to store the bits and codes tables.
 172  */
 173 int init_vlc(struct vlc *vlc, int nb_bits, int nb_codes,
 174                 const void *bits, int bits_wrap, int bits_size,
 175                 const void *codes, int codes_wrap, int codes_size)
 176 {
 177         int ret;
 178
 179         PARA_INFO_LOG("nb_codes=%d\n", nb_codes);
 180         vlc->bits = nb_bits;
 181         vlc->table = NULL;
 182         vlc->table_allocated = 0;
 183         vlc->table_size = 0;
 184         ret = build_table(vlc, nb_bits, nb_codes, bits, bits_wrap, bits_size,
 185                 codes, codes_wrap, codes_size, 0, 0);
 186         if (ret < 0)
 187                 freep(&vlc->table);
 188         return ret;
 189 }
 190
 191 void free_vlc(struct vlc *vlc)
 192 {
 193         freep(&vlc->table);
 194 }