apps/codecs/libmad/bit.c

   1 /*
   2  * libmad - MPEG audio decoder library
   3  * Copyright (C) 2000-2004 Underbit Technologies, Inc.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18  *
  19  * $Id$
  20  */
  21
  22 # ifdef HAVE_CONFIG_H
  23 #  include "config.h"
  24 # endif
  25
  26 # include "global.h"
  27
  28 # ifdef HAVE_LIMITS_H
  29 #  include <limits.h>
  30 # else
  31 #  undef  CHAR_BIT
  32 #  define CHAR_BIT  8
  33 # endif
  34
  35 # include "bit.h"
  36
  37 /*
  38  * This is the lookup table for computing the CRC-check word.
  39  * As described in section 2.4.3.1 and depicted in Figure A.9
  40  * of ISO/IEC 11172-3, the generator polynomial is:
  41  *
  42  * G(X) = X^16 + X^15 + X^2 + 1
  43  */
  44 static
  45 unsigned short const crc_table[256] = {
  46   0x0000, 0x8005, 0x800f, 0x000a, 0x801b, 0x001e, 0x0014, 0x8011,
  47   0x8033, 0x0036, 0x003c, 0x8039, 0x0028, 0x802d, 0x8027, 0x0022,
  48   0x8063, 0x0066, 0x006c, 0x8069, 0x0078, 0x807d, 0x8077, 0x0072,
  49   0x0050, 0x8055, 0x805f, 0x005a, 0x804b, 0x004e, 0x0044, 0x8041,
  50   0x80c3, 0x00c6, 0x00cc, 0x80c9, 0x00d8, 0x80dd, 0x80d7, 0x00d2,
  51   0x00f0, 0x80f5, 0x80ff, 0x00fa, 0x80eb, 0x00ee, 0x00e4, 0x80e1,
  52   0x00a0, 0x80a5, 0x80af, 0x00aa, 0x80bb, 0x00be, 0x00b4, 0x80b1,
  53   0x8093, 0x0096, 0x009c, 0x8099, 0x0088, 0x808d, 0x8087, 0x0082,
  54
  55   0x8183, 0x0186, 0x018c, 0x8189, 0x0198, 0x819d, 0x8197, 0x0192,
  56   0x01b0, 0x81b5, 0x81bf, 0x01ba, 0x81ab, 0x01ae, 0x01a4, 0x81a1,
  57   0x01e0, 0x81e5, 0x81ef, 0x01ea, 0x81fb, 0x01fe, 0x01f4, 0x81f1,
  58   0x81d3, 0x01d6, 0x01dc, 0x81d9, 0x01c8, 0x81cd, 0x81c7, 0x01c2,
  59   0x0140, 0x8145, 0x814f, 0x014a, 0x815b, 0x015e, 0x0154, 0x8151,
  60   0x8173, 0x0176, 0x017c, 0x8179, 0x0168, 0x816d, 0x8167, 0x0162,
  61   0x8123, 0x0126, 0x012c, 0x8129, 0x0138, 0x813d, 0x8137, 0x0132,
  62   0x0110, 0x8115, 0x811f, 0x011a, 0x810b, 0x010e, 0x0104, 0x8101,
  63
  64   0x8303, 0x0306, 0x030c, 0x8309, 0x0318, 0x831d, 0x8317, 0x0312,
  65   0x0330, 0x8335, 0x833f, 0x033a, 0x832b, 0x032e, 0x0324, 0x8321,
  66   0x0360, 0x8365, 0x836f, 0x036a, 0x837b, 0x037e, 0x0374, 0x8371,
  67   0x8353, 0x0356, 0x035c, 0x8359, 0x0348, 0x834d, 0x8347, 0x0342,
  68   0x03c0, 0x83c5, 0x83cf, 0x03ca, 0x83db, 0x03de, 0x03d4, 0x83d1,
  69   0x83f3, 0x03f6, 0x03fc, 0x83f9, 0x03e8, 0x83ed, 0x83e7, 0x03e2,
  70   0x83a3, 0x03a6, 0x03ac, 0x83a9, 0x03b8, 0x83bd, 0x83b7, 0x03b2,
  71   0x0390, 0x8395, 0x839f, 0x039a, 0x838b, 0x038e, 0x0384, 0x8381,
  72
  73   0x0280, 0x8285, 0x828f, 0x028a, 0x829b, 0x029e, 0x0294, 0x8291,
  74   0x82b3, 0x02b6, 0x02bc, 0x82b9, 0x02a8, 0x82ad, 0x82a7, 0x02a2,
  75   0x82e3, 0x02e6, 0x02ec, 0x82e9, 0x02f8, 0x82fd, 0x82f7, 0x02f2,
  76   0x02d0, 0x82d5, 0x82df, 0x02da, 0x82cb, 0x02ce, 0x02c4, 0x82c1,
  77   0x8243, 0x0246, 0x024c, 0x8249, 0x0258, 0x825d, 0x8257, 0x0252,
  78   0x0270, 0x8275, 0x827f, 0x027a, 0x826b, 0x026e, 0x0264, 0x8261,
  79   0x0220, 0x8225, 0x822f, 0x022a, 0x823b, 0x023e, 0x0234, 0x8231,
  80   0x8213, 0x0216, 0x021c, 0x8219, 0x0208, 0x820d, 0x8207, 0x0202
  81 };
  82
  83 # define CRC_POLY  0x8005
  84
  85 #if INT_MAX != 0x7fffffff
  86 #warning current libmad bit handling is optimized for architectures using 32 bit integers
  87 #endif
  88
  89 /*
  90  * NAME:        bit->init()
  91  * DESCRIPTION: initialize bit pointer struct
  92  */
  93 void mad_bit_init(struct mad_bitptr *bitptr, unsigned char const *byte)
  94 {
  95   bitptr->ptr     = (uint32_t*)((uintptr_t)byte & ~3);
  96   bitptr->readbit = ((uintptr_t)byte & 3) << 3;
  97 }
  98
  99 /*
 100  * NAME:        bit->length()
 101  * DESCRIPTION: return number of bits between start and end points
 102  */
 103 unsigned int mad_bit_length(struct mad_bitptr const *begin,
 104                             struct mad_bitptr const *end)
 105 {
 106   return end->readbit - begin->readbit;
 107 }
 108
 109 /* rockbox: not used
 110 unsigned char mad_bit_bitsleft(struct mad_bitptr const *bitptr)
 111 {
 112   return 8 - (bitptr->readbit & 7);
 113 }
 114 */
 115
 116 /*
 117  * NAME:        bit->nextbyte()
 118  * DESCRIPTION: return pointer to next unprocessed byte
 119  */
 120 unsigned char const *mad_bit_nextbyte(struct mad_bitptr const *bitptr)
 121 {
 122   return (unsigned char const*)bitptr->ptr + ((bitptr->readbit + 7) >> 3);
 123 }
 124
 125 /*
 126  * NAME:        bit->skip()
 127  * DESCRIPTION: advance bit pointer
 128  */
 129 void mad_bit_skip(struct mad_bitptr *bitptr, unsigned int len)
 130 {
 131   bitptr->readbit += len;
 132 }
 133
 134 /*
 135  * NAME:        bit->read()
 136  * DESCRIPTION: read an arbitrary number of bits and return their UIMSBF value
 137  */
 138
 139 uint32_t mad_bit_read(struct mad_bitptr *bitptr, unsigned int len) ICODE_ATTR;
 140 uint32_t mad_bit_read(struct mad_bitptr *bitptr, unsigned int len)
 141 {
 142   uint32_t *curr = &bitptr->ptr[bitptr->readbit>>5];
 143
 144   if(len)
 145   {
 146     uint32_t r = betoh32(curr[0]) << (bitptr->readbit & 31);
 147
 148     if((bitptr->readbit & 31) + len > 32)
 149       r += betoh32(curr[1]) >> (-bitptr->readbit & 31);
 150
 151     bitptr->readbit += len;
 152     return r >> (32 - len);
 153   }
 154
 155   return 0;
 156 }
 157
 158 # if 0 /* rockbox: not used */
 159 /*
 160  * NAME:        bit->write()
 161  * DESCRIPTION: write an arbitrary number of bits
 162  */
 163 void mad_bit_write(struct mad_bitptr *bitptr, unsigned int len,
 164                    uint32_t value)
 165 {
 166   unsigned char *ptr;
 167
 168   ptr = (unsigned char *) bitptr->byte;
 169
 170   /* ... */
 171 }
 172 # endif
 173
 174 /*
 175  * NAME:        bit->crc()
 176  * DESCRIPTION: compute CRC-check word
 177  */
 178 unsigned short mad_bit_crc(struct mad_bitptr bitptr, unsigned int len,
 179                            unsigned short init)
 180 {
 181   register unsigned int crc;
 182
 183   for (crc = init; len >= 32; len -= 32) {
 184     register uint32_t data;
 185
 186     data = mad_bit_read(&bitptr, 32);
 187
 188     crc = (crc << 8) ^ crc_table[((crc >> 8) ^ (data >> 24)) & 0xff];
 189     crc = (crc << 8) ^ crc_table[((crc >> 8) ^ (data >> 16)) & 0xff];
 190     crc = (crc << 8) ^ crc_table[((crc >> 8) ^ (data >>  8)) & 0xff];
 191     crc = (crc << 8) ^ crc_table[((crc >> 8) ^ (data >>  0)) & 0xff];
 192   }
 193
 194   switch (len / 8) {
 195   case 3: crc = (crc << 8) ^
 196             crc_table[((crc >> 8) ^ mad_bit_read(&bitptr, 8)) & 0xff];
 197   case 2: crc = (crc << 8) ^
 198             crc_table[((crc >> 8) ^ mad_bit_read(&bitptr, 8)) & 0xff];
 199   case 1: crc = (crc << 8) ^
 200             crc_table[((crc >> 8) ^ mad_bit_read(&bitptr, 8)) & 0xff];
 201
 202   len %= 8;
 203
 204   case 0: break;
 205   }
 206
 207   while (len--) {
 208     register unsigned int msb;
 209
 210     msb = mad_bit_read(&bitptr, 1) ^ (crc >> 15);
 211
 212     crc <<= 1;
 213     if (msb & 1)
 214       crc ^= CRC_POLY;
 215   }
 216
 217   return crc & 0xffff;
 218 }