[unix-history] / usr / src / sys / stand / disklabel.c

/*-
* Copyright (c) 1993 The Regents of the University of California.
* All rights reserved.
*
* %sccs.include.redist.c%
*
*      @(#)disklabel.c 7.1 (Berkeley) %G%
*/

#include <sys/param.h>
#include <sys/disklabel.h>

char *
getdisklabel(buf, lp)
       const char *buf;
       struct disklabel *lp;
{
       register struct buf *bp;
       struct disklabel *dlp, *elp;
       char *msg = (char *)0;

       elp = (struct disklabel *)(buf + DEV_BSIZE - sizeof(*dlp));
       for (dlp = (struct disklabel *)buf; dlp <= elp;
           dlp = (struct disklabel *)((char *)dlp + sizeof(long))) {
               if (dlp->d_magic != DISKMAGIC || dlp->d_magic2 != DISKMAGIC) {
                       if (msg == (char *)0)
                               msg = "no disk label";
               } else if (dlp->d_npartitions > MAXPARTITIONS ||
                          dkcksum(dlp) != 0)
                       msg = "disk label corrupted";
               else {
                       *lp = *dlp;
                       msg = (char *)0;
                       break;
               }
       }
       return (msg);
}

/*
* Compute checksum for disk label.
*/
dkcksum(lp)
       register struct disklabel *lp;
{
       register u_short *start, *end;
       register u_short sum = 0;

       start = (u_short *)lp;
       end = (u_short *)&lp->d_partitions[lp->d_npartitions];
       while (start < end)
               sum ^= *start++;
       return (sum);
}