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 void alloc_table(struct vlc *vlc, int size)
  47 {
  48         vlc->table_size += size;
  49         if (vlc->table_size > vlc->table_allocated) {
  50                 vlc->table_allocated += (1 << vlc->bits);
  51                 vlc->table = para_realloc(vlc->table,
  52                         sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
  53         }
  54 }
  55
  56 static int build_table(struct vlc *vlc, int table_nb_bits, int nb_codes,
  57                 const void *bits, const void *codes, int codes_wrap,
  58                 int codes_size, uint32_t code_prefix, int n_prefix)
  59 {
  60         int ret, i, j, k, n, table_size, table_index, nb, n1, idx, code_prefix2,
  61                 symbol;
  62         uint32_t code;
  63         VLC_TYPE(*table)[2];
  64
  65         table_size = 1 << table_nb_bits;
  66         table_index = vlc->table_size;
  67         alloc_table(vlc, table_size);
  68         table = &vlc->table[table_index];
  69
  70         for (i = 0; i < table_size; i++) {
  71                 table[i][1] = 0;        //bits
  72                 table[i][0] = -1;       //codes
  73         }
  74
  75         /* first pass: map codes and compute auxillary table sizes */
  76         for (i = 0; i < nb_codes; i++) {
  77                 GET_DATA(n, bits, i, 1, 1);
  78                 GET_DATA(code, codes, i, codes_wrap, codes_size);
  79                 /* we accept tables with holes */
  80                 if (n <= 0)
  81                         continue;
  82                 symbol = i;
  83                 /* if code matches the prefix, it is in the table */
  84                 n -= n_prefix;
  85                 code_prefix2 = code >> n;
  86                 if (n > 0 && code_prefix2 == code_prefix) {
  87                         if (n <= table_nb_bits) {
  88                                 /* no need to add another table */
  89                                 j = (code << (table_nb_bits - n)) & (table_size - 1);
  90                                 nb = 1 << (table_nb_bits - n);
  91                                 for (k = 0; k < nb; k++) {
  92                                         if (table[j][1] /* bits */ != 0)
  93                                                 return -E_BAD_CODES;
  94                                         table[j][1] = n;        //bits
  95                                         table[j][0] = symbol;
  96                                         j++;
  97                                 }
  98                         } else {
  99                                 n -= table_nb_bits;
 100                                 j = (code >> n) & ((1 << table_nb_bits) - 1);
 101                                 /* compute table size */
 102                                 n1 = -table[j][1];      //bits
 103                                 if (n > n1)
 104                                         n1 = n;
 105                                 table[j][1] = -n1;      //bits
 106                         }
 107                 }
 108         }
 109
 110         /* second pass : fill auxillary tables recursively */
 111         for (i = 0; i < table_size; i++) {
 112                 n = table[i][1];        //bits
 113                 if (n < 0) {
 114                         n = -n;
 115                         if (n > table_nb_bits) {
 116                                 n = table_nb_bits;
 117                                 table[i][1] = -n;       //bits
 118                         }
 119                         ret = build_table(vlc, n, nb_codes,
 120                                 bits, codes, codes_wrap, codes_size,
 121                                 (code_prefix << table_nb_bits) | i,
 122                                 n_prefix + table_nb_bits);
 123                         if (ret < 0)
 124                                 return ret;
 125                         idx = ret;
 126                         /* note: realloc has been done, so reload tables */
 127                         table = &vlc->table[table_index];
 128                         table[i][0] = idx;      //code
 129                 }
 130         }
 131         return table_index;
 132 }
 133
 134 /**
 135  * Build VLC decoding tables suitable for use with get_vlc().
 136  *
 137  * \param nb_bits Set the decoding table size (2^nb_bits)
 138  * entries. The bigger it is, the faster is the decoding. But
 139  * it should not be too big to save memory and L1 cache. '9'
 140  * is a good compromise.
 141  *
 142  * \param nb_codes Number of vlcs codes.
 143  *
 144  * \param bits Table which gives the size (in bits) of each
 145  * vlc code.
 146  *
 147  * \param codes Table which gives the bit pattern of of each
 148  * vlc code.
 149  *
 150  * \param codes_wrap The number of bytes between each entry of the
 151  * 'codes' tables.
 152  *
 153  * \param codes_size The number of bytes of each entry of the
 154  * 'codes' tables.
 155  *
 156  * The wrap and size parameters allow to use any memory configuration and
 157  * types (byte/word/long) to store the bits and codes tables.
 158  */
 159 int init_vlc(struct vlc *vlc, int nb_bits, int nb_codes,
 160                 const void *bits, const void *codes, int codes_wrap,
 161                 int codes_size)
 162 {
 163         int ret;
 164
 165         PARA_INFO_LOG("nb_codes=%d\n", nb_codes);
 166         vlc->bits = nb_bits;
 167         vlc->table = NULL;
 168         vlc->table_allocated = 0;
 169         vlc->table_size = 0;
 170         ret = build_table(vlc, nb_bits, nb_codes, bits,
 171                 codes, codes_wrap, codes_size, 0, 0);
 172         if (ret < 0)
 173                 freep(&vlc->table);
 174         return ret;
 175 }
 176
 177 void free_vlc(struct vlc *vlc)
 178 {
 179         freep(&vlc->table);
 180 }