[C] Conversion de 16 a 32 bits

 Este codigo no es de mi autoría. Procede del foro Hackxcrack.net

#include<stdio.h>
unsigned short CRC(unsigned char *s, int len, unsigned short crcval);
     
int main(){
unsigned char *test="\x01\x55\x00\x00";
printf("CRC: %u\n",CRC(test,4,0));
return 0;}
     
unsigned short CRC(unsigned char *s, int len, unsigned short crcval){
register unsigned c,q;
for (;len;len--){
c=*s++;q=(crcval^c)&017;

crcval=(crcval>>4)^(q*010201);
q=(crcval^(c>>4))&017;
crcval=(crcval>>4)^(q*010201);}
return (crcval);}

//010201 es octal
//017 tambien