src/add-ons/kernel/file_systems/udf/crc_table.cpp

   1 //----------------------------------------------------------------------
   2 //  This software is part of the OpenBeOS distribution and is covered
   3 //  by the OpenBeOS license.
   4 //
   5 //  Copyright (c) 2003 Tyler Dauwalder, tyler@dauwalder.net
   6 //---------------------------------------------------------------------
   7
   8 /*! \file crc_table.cpp
   9
  10         Standalone program to generate the CRC table used for calculating
  11         UDF tag id CRC values.
  12
  13         This code based off of crc code in UDF-2.50 specs, as permitted.
  14         See UDF-2.50 6.5 for more information.
  15 */
  16
  17 #include <stdio.h>
  18
  19 int
  20 main(int argc, char *argv[]) {
  21         ulong crc, poly;
  22
  23         if (argc != 2) {
  24                 fprintf(stderr, "USAGE: crc_table <octal polynomial=010041 for UDF>\n");
  25                 return 0;
  26         }
  27
  28         sscanf(argv[1], "%lo", &poly);
  29         if (poly & 0xffff0000) {
  30                 fprintf(stderr, "ERROR: polynomial is too large, sucka.\n");
  31                 return 0;
  32         }
  33
  34         printf("//! CRC 0%o table, as generated by crc_table.cpp\n", poly);
  35         printf("static uint16 crc_table[256] = { \n");
  36         for (int n = 0; n < 256; n++) {
  37                 if (n%8 == 0)
  38                         printf("    ");
  39                 crc = n << 8;
  40                 for (int i = 0; i < 8; i++) {
  41                         if (crc & 0x8000)
  42                                 crc = (crc << 1) ^ poly;
  43                         else
  44                                 crc <<= 1;
  45                         crc &= 0xffff;
  46                 }
  47                 printf("0x%04x%s ", crc, (n != 255 ? "," : ""));
  48                 if (n%8 == 7)
  49                         printf("\n");
  50         }
  51         printf("};\n");
  52         return 0;
  53 }