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 = para_realloc(vlc->table,
  55                         sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
  56         }
  57         return idx;
  58 }
  59
  60 static int build_table(struct vlc *vlc, int table_nb_bits,
  61                 int nb_codes, const void *bits, int bits_wrap, int bits_size,
  62                 const void *codes, int codes_wrap, int codes_size,
  63                 uint32_t code_prefix, int n_prefix)
  64 {
  65         int ret, i, j, k, n, table_size, table_index, nb, n1, idx, code_prefix2,
  66                 symbol;
  67         uint32_t code;
  68         VLC_TYPE(*table)[2];
  69
  70         table_size = 1 << table_nb_bits;
  71         ret = alloc_table(vlc, table_size);
  72         if (ret < 0)
  73                 return ret;
  74         table_index = ret;
  75         table = &vlc->table[table_index];
  76
  77         for (i = 0; i < table_size; i++) {
  78                 table[i][1] = 0;        //bits
  79                 table[i][0] = -1;       //codes
  80         }
  81
  82         /* first pass: map codes and compute auxillary table sizes */
  83         for (i = 0; i < nb_codes; i++) {
  84                 GET_DATA(n, bits, i, bits_wrap, bits_size);
  85                 GET_DATA(code, codes, i, codes_wrap, codes_size);
  86                 /* we accept tables with holes */
  87                 if (n <= 0)
  88                         continue;
  89                 symbol = i;
  90                 /* if code matches the prefix, it is in the table */
  91                 n -= n_prefix;
  92                 code_prefix2 = code >> n;
  93                 if (n > 0 && code_prefix2 == code_prefix) {
  94                         if (n <= table_nb_bits) {
  95                                 /* no need to add another table */
  96                                 j = (code << (table_nb_bits - n)) & (table_size - 1);
  97                                 nb = 1 << (table_nb_bits - n);
  98                                 for (k = 0; k < nb; k++) {
  99                                         if (table[j][1] /* bits */ != 0)
 100                                                 return -E_BAD_CODES;
 101                                         table[j][1] = n;        //bits
 102                                         table[j][0] = symbol;
 103                                         j++;
 104                                 }
 105                         } else {
 106                                 n -= table_nb_bits;
 107                                 j = (code >> n) & ((1 << table_nb_bits) - 1);
 108                                 /* compute table size */
 109                                 n1 = -table[j][1];      //bits
 110                                 if (n > n1)
 111                                         n1 = n;
 112                                 table[j][1] = -n1;      //bits
 113                         }
 114                 }
 115         }
 116
 117         /* second pass : fill auxillary tables recursively */
 118         for (i = 0; i < table_size; i++) {
 119                 n = table[i][1];        //bits
 120                 if (n < 0) {
 121                         n = -n;
 122                         if (n > table_nb_bits) {
 123                                 n = table_nb_bits;
 124                                 table[i][1] = -n;       //bits
 125                         }
 126                         ret = build_table(vlc, n, nb_codes,
 127                                 bits, bits_wrap, bits_size,
 128                                 codes, codes_wrap, codes_size,
 129                                 (code_prefix << table_nb_bits) | i,
 130                                 n_prefix + table_nb_bits);
 131                         if (ret < 0)
 132                                 return ret;
 133                         idx = ret;
 134                         /* note: realloc has been done, so reload tables */
 135                         table = &vlc->table[table_index];
 136                         table[i][0] = idx;      //code
 137                 }
 138         }
 139         return table_index;
 140 }
 141
 142 /**
 143  * Build VLC decoding tables suitable for use with get_vlc().
 144  *
 145  * \param nb_bits Set the decoding table size (2^nb_bits)
 146  * entries. The bigger it is, the faster is the decoding. But
 147  * it should not be too big to save memory and L1 cache. '9'
 148  * is a good compromise.
 149  *
 150  * \param nb_codes Number of vlcs codes.
 151  *
 152  * \param bits Table which gives the size (in bits) of each
 153  * vlc code.
 154  *
 155  * \param codes Table which gives the bit pattern of of each
 156  * vlc code.
 157  *
 158  * \param bits_wrap The number of bytes between each entry of the
 159  * 'bits' or 'codes' tables.
 160  *
 161  * \param bits_size The number of bytes of each entry of the
 162  * 'bits' or 'codes' tables.
 163  *
 164  * \param codes_wrap Same as bits_wrap but uses the 'codes' table.
 165  *
 166  * \param codes_size Same as bits_size but for the 'codes' table.
 167  *
 168  * The wrap and size parameters allow to use any memory configuration and
 169  * types (byte/word/long) to store the bits and codes tables.
 170  */
 171 int init_vlc(struct vlc *vlc, int nb_bits, int nb_codes,
 172                 const void *bits, int bits_wrap, int bits_size,
 173                 const void *codes, int codes_wrap, int codes_size)
 174 {
 175         int ret;
 176
 177         PARA_INFO_LOG("nb_codes=%d\n", nb_codes);
 178         vlc->bits = nb_bits;
 179         vlc->table = NULL;
 180         vlc->table_allocated = 0;
 181         vlc->table_size = 0;
 182         ret = build_table(vlc, nb_bits, nb_codes, bits, bits_wrap, bits_size,
 183                 codes, codes_wrap, codes_size, 0, 0);
 184         if (ret < 0)
 185                 freep(&vlc->table);
 186         return ret;
 187 }
 188
 189 void free_vlc(struct vlc *vlc)
 190 {
 191         freep(&vlc->table);
 192 }