//----------------------------------------------------------------------
//  This software is part of the Haiku distribution and is covered
//  by the MIT License.
//
//  Copyright (c) 2003 Tyler Dauwalder, tyler@dauwalder.net
//---------------------------------------------------------------------

/*! \file crc_table.cpp

        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.  

        Reversed version by Jérôme Duval
*/

#include <stdio.h>
#include <sys/types.h>

int
main(int argc, char *argv[]) {
        ulong crc, poly;

        if (argc != 2) {
                fprintf(stderr, "USAGE: crc_table <octal polynomial=120001 for ext2>\n");
                return 0;
        }

        sscanf(argv[1], "%lo", &poly);
        if (poly & 0xffff0000) {
                fprintf(stderr, "ERROR: polynomial is too large, sucka.\n");
                return 0;
        }
        
        printf("//! CRC 0%o table, as generated by crc_table.cpp\n", poly);
        printf("static uint16 crc_table[256] = { \n");
        for (int n = 0; n < 256; n++) {
                if (n%8 == 0)
                        printf("    ");
                crc = n;
                for (int i = 0; i < 8; i++) {
                        if (crc & 0x0001)
                                crc = (crc >> 1) ^ poly;
                        else
                                crc >>= 1;
                }
                printf("0x%04x%s ", crc, (n != 255 ? "," : ""));
                if (n%8 == 7)
                        printf("\n");
        }
        printf("};\n");
        return 0;
}