usr/src/sys/ufs/lfs/lfs_cksum.c

/*-
 * Copyright (c) 1991 The Regents of the University of California.
 * All rights reserved.
 *
 * %sccs.include.redist.c%
 *
 *      @(#)lfs_cksum.c 5.2 (Berkeley) %G%
 */

#ifdef LOGFS
#include <sys/types.h>

/*
 * Simple, general purpose, fast checksum.  Data must be short-aligned.
 * Returns a u_long in case we ever want to do something more rigorous.
 */
u_long
cksum(str, len)
        register void *str;
        register size_t len;
{
        register u_long sum;

        len &= ~(sizeof(u_short) - 1);
        for (sum = 0; len; len -= sizeof(u_short))
                sum ^= *((u_short *)str)++;
        return (sum);
}
#endif /* LOGFS */