1 /* 2 * This software is part of the Haiku distribution and is covered 3 * by the MIT 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 * Reflected version by Jéme Duval 17 */ 18 19 20 21 #include "system_dependencies.h" 22 23 24 typedef unsigned int uint32 ; 25 26 27 uint32 28 reflect32 (uint32 b) 29 { 30 uint32 rw = 0; 31 32 for (int i = 0; i < 32; i++) { 33 if (b & 1) 34 rw |= 1 << (31 - i); 35 b >>= 1; 36 } 37 return rw; 38 } 39 40 41 int 42 main(int argc, char* argv[]) { 43 uint32 crc, poly; 44 45 if (argc != 2) { 46 fprintf(stderr, "USAGE: crc_table <octal polynomial=3667067501 for btrfs>\n"); 47 return 0; 48 } 49 sscanf(argv[1], "%lo", &poly); 50 printf("//! CRC 0%o table, as generated by crc_table.cpp\n", poly); 51 printf("static uint32 kCrcTable[256] = {\n\t"); 52 for (int n = 0; n < 256; n++) { 53 crc = reflect32(n); 54 for (int i = 0; i < 8; i++) { 55 if (crc & 0x80000000) 56 crc = (crc << 1) ^ poly; 57 else 58 crc <<= 1; 59 } 60 crc = reflect32(crc); 61 printf("0x%08x%s%s", crc, (n != 255 ? "," : ""), (n % 6 != 5 ? " " : "")); 62 if (n % 6 == 5) 63 printf("\n\t"); 64 } 65 printf("\n};\n"); 66 return 0; 67 } 68 69