BSD 3 development

[unix-history] / usr / src / cmd / uucp / chksum.c

main()
{
       int i, j;
       char buf[300];

       for (i = 0; i < 300; i++)
               buf[i] = i;
       printf("%o\n", chksum(buf, 300));
}

chksum(s,n)
register char *s;
register n;
{
       register short sum;
       register unsigned t;
       register x;

       sum = -1;
       x = 0;

       do {
               if (sum<0) {
                       sum <<= 1;
                       sum++;
               } else
                       sum <<= 1;
               t = sum;
               sum += (unsigned)*s++;
               x += sum^n;
               if ((unsigned)sum <= t) {
                       sum ^= x;
               }
       } while (--n > 0);

       return(sum);
}