git.oblomov.eu Git - linux-2.6/blob - fs/udf/crc.c

   1 /*
   2  * crc.c
   3  *
   4  * PURPOSE
   5  *      Routines to generate, calculate, and test a 16-bit CRC.
   6  *
   7  * DESCRIPTION
   8  *      The CRC code was devised by Don P. Mitchell of AT&T Bell Laboratories
   9  *      and Ned W. Rhodes of Software Systems Group. It has been published in
  10  *      "Design and Validation of Computer Protocols", Prentice Hall,
  11  *      Englewood Cliffs, NJ, 1991, Chapter 3, ISBN 0-13-539925-4.
  12  *
  13  *      Copyright is held by AT&T.
  14  *
  15  *      AT&T gives permission for the free use of the CRC source code.
  16  *
  17  * COPYRIGHT
  18  *      This file is distributed under the terms of the GNU General Public
  19  *      License (GPL). Copies of the GPL can be obtained from:
  20  *              ftp://prep.ai.mit.edu/pub/gnu/GPL
  21  *      Each contributing author retains all rights to their own work.
  22  */
  23
  24 #include "udfdecl.h"
  25
  26 static uint16_t crc_table[256] = {
  27         0x0000U, 0x1021U, 0x2042U, 0x3063U, 0x4084U, 0x50a5U, 0x60c6U, 0x70e7U,
  28         0x8108U, 0x9129U, 0xa14aU, 0xb16bU, 0xc18cU, 0xd1adU, 0xe1ceU, 0xf1efU,
  29         0x1231U, 0x0210U, 0x3273U, 0x2252U, 0x52b5U, 0x4294U, 0x72f7U, 0x62d6U,
  30         0x9339U, 0x8318U, 0xb37bU, 0xa35aU, 0xd3bdU, 0xc39cU, 0xf3ffU, 0xe3deU,
  31         0x2462U, 0x3443U, 0x0420U, 0x1401U, 0x64e6U, 0x74c7U, 0x44a4U, 0x5485U,
  32         0xa56aU, 0xb54bU, 0x8528U, 0x9509U, 0xe5eeU, 0xf5cfU, 0xc5acU, 0xd58dU,
  33         0x3653U, 0x2672U, 0x1611U, 0x0630U, 0x76d7U, 0x66f6U, 0x5695U, 0x46b4U,
  34         0xb75bU, 0xa77aU, 0x9719U, 0x8738U, 0xf7dfU, 0xe7feU, 0xd79dU, 0xc7bcU,
  35         0x48c4U, 0x58e5U, 0x6886U, 0x78a7U, 0x0840U, 0x1861U, 0x2802U, 0x3823U,
  36         0xc9ccU, 0xd9edU, 0xe98eU, 0xf9afU, 0x8948U, 0x9969U, 0xa90aU, 0xb92bU,
  37         0x5af5U, 0x4ad4U, 0x7ab7U, 0x6a96U, 0x1a71U, 0x0a50U, 0x3a33U, 0x2a12U,
  38         0xdbfdU, 0xcbdcU, 0xfbbfU, 0xeb9eU, 0x9b79U, 0x8b58U, 0xbb3bU, 0xab1aU,
  39         0x6ca6U, 0x7c87U, 0x4ce4U, 0x5cc5U, 0x2c22U, 0x3c03U, 0x0c60U, 0x1c41U,
  40         0xedaeU, 0xfd8fU, 0xcdecU, 0xddcdU, 0xad2aU, 0xbd0bU, 0x8d68U, 0x9d49U,
  41         0x7e97U, 0x6eb6U, 0x5ed5U, 0x4ef4U, 0x3e13U, 0x2e32U, 0x1e51U, 0x0e70U,
  42         0xff9fU, 0xefbeU, 0xdfddU, 0xcffcU, 0xbf1bU, 0xaf3aU, 0x9f59U, 0x8f78U,
  43         0x9188U, 0x81a9U, 0xb1caU, 0xa1ebU, 0xd10cU, 0xc12dU, 0xf14eU, 0xe16fU,
  44         0x1080U, 0x00a1U, 0x30c2U, 0x20e3U, 0x5004U, 0x4025U, 0x7046U, 0x6067U,
  45         0x83b9U, 0x9398U, 0xa3fbU, 0xb3daU, 0xc33dU, 0xd31cU, 0xe37fU, 0xf35eU,
  46         0x02b1U, 0x1290U, 0x22f3U, 0x32d2U, 0x4235U, 0x5214U, 0x6277U, 0x7256U,
  47         0xb5eaU, 0xa5cbU, 0x95a8U, 0x8589U, 0xf56eU, 0xe54fU, 0xd52cU, 0xc50dU,
  48         0x34e2U, 0x24c3U, 0x14a0U, 0x0481U, 0x7466U, 0x6447U, 0x5424U, 0x4405U,
  49         0xa7dbU, 0xb7faU, 0x8799U, 0x97b8U, 0xe75fU, 0xf77eU, 0xc71dU, 0xd73cU,
  50         0x26d3U, 0x36f2U, 0x0691U, 0x16b0U, 0x6657U, 0x7676U, 0x4615U, 0x5634U,
  51         0xd94cU, 0xc96dU, 0xf90eU, 0xe92fU, 0x99c8U, 0x89e9U, 0xb98aU, 0xa9abU,
  52         0x5844U, 0x4865U, 0x7806U, 0x6827U, 0x18c0U, 0x08e1U, 0x3882U, 0x28a3U,
  53         0xcb7dU, 0xdb5cU, 0xeb3fU, 0xfb1eU, 0x8bf9U, 0x9bd8U, 0xabbbU, 0xbb9aU,
  54         0x4a75U, 0x5a54U, 0x6a37U, 0x7a16U, 0x0af1U, 0x1ad0U, 0x2ab3U, 0x3a92U,
  55         0xfd2eU, 0xed0fU, 0xdd6cU, 0xcd4dU, 0xbdaaU, 0xad8bU, 0x9de8U, 0x8dc9U,
  56         0x7c26U, 0x6c07U, 0x5c64U, 0x4c45U, 0x3ca2U, 0x2c83U, 0x1ce0U, 0x0cc1U,
  57         0xef1fU, 0xff3eU, 0xcf5dU, 0xdf7cU, 0xaf9bU, 0xbfbaU, 0x8fd9U, 0x9ff8U,
  58         0x6e17U, 0x7e36U, 0x4e55U, 0x5e74U, 0x2e93U, 0x3eb2U, 0x0ed1U, 0x1ef0U
  59 };
  60
  61 /*
  62  * udf_crc
  63  *
  64  * PURPOSE
  65  *      Calculate a 16-bit CRC checksum using ITU-T V.41 polynomial.
  66  *
  67  * DESCRIPTION
  68  *      The OSTA-UDF(tm) 1.50 standard states that using CRCs is mandatory.
  69  *      The polynomial used is: x^16 + x^12 + x^15 + 1
  70  *
  71  * PRE-CONDITIONS
  72  *      data            Pointer to the data block.
  73  *      size            Size of the data block.
  74  *
  75  * POST-CONDITIONS
  76  *      <return>        CRC of the data block.
  77  *
  78  * HISTORY
  79  *      July 21, 1997 - Andrew E. Mileski
  80  *      Adapted from OSTA-UDF(tm) 1.50 standard.
  81  */
  82 uint16_t udf_crc(uint8_t * data, uint32_t size, uint16_t crc)
  83 {
  84         while (size--)
  85                 crc = crc_table[(crc >> 8 ^ *(data++)) & 0xffU] ^ (crc << 8);
  86
  87         return crc;
  88 }
  89
  90 /****************************************************************************/
  91 #if defined(TEST)
  92
  93 /*
  94  * PURPOSE
  95  *      Test udf_crc()
  96  *
  97  * HISTORY
  98  *      July 21, 1997 - Andrew E. Mileski
  99  *      Adapted from OSTA-UDF(tm) 1.50 standard.
 100  */
 101
 102 unsigned char bytes[] = { 0x70U, 0x6AU, 0x77U };
 103
 104 int main(void)
 105 {
 106         unsigned short x;
 107
 108         x = udf_crc(bytes, sizeof bytes);
 109         printf("udf_crc: calculated = %4.4x, correct = %4.4x\n", x, 0x3299U);
 110
 111         return 0;
 112 }
 113
 114 #endif /* defined(TEST) */
 115
 116 /****************************************************************************/
 117 #if defined(GENERATE)
 118
 119 /*
 120  * PURPOSE
 121  *      Generate a table for fast 16-bit CRC calculations (any polynomial).
 122  *
 123  * DESCRIPTION
 124  *      The ITU-T V.41 polynomial is 010041.
 125  *
 126  * HISTORY
 127  *      July 21, 1997 - Andrew E. Mileski
 128  *      Adapted from OSTA-UDF(tm) 1.50 standard.
 129  */
 130
 131 #include <stdio.h>
 132
 133 int main(int argc, char **argv)
 134 {
 135         unsigned long crc, poly;
 136         int n, i;
 137
 138         /* Get the polynomial */
 139         sscanf(argv[1], "%lo", &poly);
 140         if (poly & 0xffff0000U) {
 141                 fprintf(stderr, "polynomial is too large\en");
 142                 exit(1);
 143         }
 144
 145         printf("/* CRC 0%o */\n", poly);
 146
 147         /* Create a table */
 148         printf("static unsigned short crc_table[256] = {\n");
 149         for (n = 0; n < 256; n++) {
 150                 if (n % 8 == 0)
 151                         printf("\t");
 152                 crc = n << 8;
 153                 for (i = 0; i < 8; i++) {
 154                         if (crc & 0x8000U)
 155                                 crc = (crc << 1) ^ poly;
 156                         else
 157                                 crc <<= 1;
 158                         crc &= 0xFFFFU;
 159                 }
 160                 if (n == 255)
 161                         printf("0x%04xU ", crc);
 162                 else
 163                         printf("0x%04xU, ", crc);
 164                 if (n % 8 == 7)
 165                         printf("\n");
 166         }
 167         printf("};\n");
 168
 169         return 0;
 170 }
 171
 172 #endif /* defined(GENERATE) */