* This software is part of the Haiku distribution and is covered
* by the MIT License.
*
* Copyright (c) 2003 Tyler Dauwalder, tyler@dauwalder.net
*/
*
* Standalone program to generate the CRC table used for calculating
* UDF tag id CRC values.
*
* This code based off of crc code in UDF-2.50 specs, as permitted.
* See UDF-2.50 6.5 for more information.
*
* Reflected version by Jéme Duval
*/
#include "system_dependencies.h"
typedef unsigned int uint32 ;
uint32
reflect32 (uint32 b)
{
uint32 rw = 0;
for (int i = 0; i < 32; i++) {
if (b & 1)
rw |= 1 << (31 - i);
b >>= 1;
}
return rw;
}
int
main(int argc, char* argv[]) {
uint32 crc, poly;
if (argc != 2) {
fprintf(stderr, "USAGE: crc_table <octal polynomial=3667067501 for btrfs>\n");
return 0;
}
sscanf(argv[1], "%lo", &poly);
printf("//! CRC 0%o table, as generated by crc_table.cpp\n", poly);
printf("static uint32 kCrcTable[256] = {\n\t");
for (int n = 0; n < 256; n++) {
crc = reflect32(n);
for (int i = 0; i < 8; i++) {
if (crc & 0x80000000)
crc = (crc << 1) ^ poly;
else
crc <<= 1;
}
crc = reflect32(crc);
printf("0x%08x%s%s", crc, (n != 255 ? "," : ""), (n % 6 != 5 ? " " : ""));
if (n % 6 == 5)
printf("\n\t");
}
printf("\n};\n");
return 0;
}
