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Annotation of 43BSDTahoe/etc/timed/cksum.m68000.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1983 Regents of the University of California.
                      3:  * All rights reserved.
                      4:  *
                      5:  * Redistribution and use in source and binary forms are permitted
                      6:  * provided that the above copyright notice and this paragraph are
                      7:  * duplicated in all such forms and that any documentation,
                      8:  * advertising materials, and other materials related to such
                      9:  * distribution and use acknowledge that the software was developed
                     10:  * by the University of California, Berkeley.  The name of the
                     11:  * University may not be used to endorse or promote products derived
                     12:  * from this software without specific prior written permission.
                     13:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
                     14:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
                     15:  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
                     16:  */
                     17: 
                     18: #ifndef lint
                     19: static char sccsid[] = "@(#)cksum.m68000.c     2.3 (Berkeley) 6/18/88";
                     20: #endif /* not lint */
                     21: 
                     22: #include "../globals.h"
                     23: #include <protocols/timed.h>
                     24: 
                     25: /* computes the checksum for ip packets for a Motorola 68000 base computer */
                     26: 
                     27: in_cksum(w, mlen)
                     28:        register u_short *w;
                     29:        register int mlen;
                     30: {
                     31:        register int sum = 0;
                     32: 
                     33:        if (mlen > 0) {
                     34:                if (((int)w & 1) == 0) {
                     35:                        sum = ocsum(w, mlen>>1);
                     36:                        w += mlen>>1;
                     37:                        if (mlen & 1) {
                     38:                                sum += *(u_char *)w << 8;
                     39:                                mlen = -1;
                     40:                        }
                     41:                } else {
                     42:                        u_short swsum;
                     43: 
                     44:                        sum = *(u_char *)w << 8;
                     45:                        mlen--;
                     46:                        w = (u_short *)(1 + (int)w);
                     47:                        swsum = ocsum(w, mlen>>1);
                     48:                        swab((char *)&swsum, (char *)&swsum, sizeof swsum);
                     49:                        sum += swsum;
                     50:                        w += mlen>>1;
                     51:                        if (mlen & 1)
                     52:                                sum += *(u_char *)w;
                     53:                }
                     54:        }
                     55:        sum = (sum & 0xFFFF) + (sum >> 16);
                     56:        sum = (sum & 0xFFFF) + (sum >> 16);
                     57:        sum = (~sum) & 0xFFFF;
                     58:        return (sum);
                     59: }

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