#include <stdio.h>
unsigned long c,c2,p2,pol=0xEDB88320;
long n,k;
main()
{
        printf("CRC32 Adjuster (c) 2001 by RElf @ HHT/2\n");
        printf("Length of data: "); scanf("%ld",&n);
        printf("Offset to patch: "); scanf("%ld",&k);
        n = (n-k)< 3 ;
        printf("Current CRC32: 0x"); scanf("%x",&c);
        printf("Desired CRC32: 0x"); scanf("%x",&c2);
        c ^= c2;
        p2 = (pol <<  1 ) |  1 ;
        while(n--) if(c&0x80000000) c = (c<<1)^p2; else c<<=1;
        printf("XOR masks:%02X%02X%02X%02X\n",c&0xff,(c>> 8 )&0xff,(c>> 16 )&0xff, c>> 24 );
}