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Annotation of XNU/bsd/ufs/lfs/lfs_cksum.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
                      3:  *
                      4:  * @APPLE_LICENSE_HEADER_START@
                      5:  * 
                      6:  * The contents of this file constitute Original Code as defined in and
                      7:  * are subject to the Apple Public Source License Version 1.1 (the
                      8:  * "License").  You may not use this file except in compliance with the
                      9:  * License.  Please obtain a copy of the License at
                     10:  * http://www.apple.com/publicsource and read it before using this file.
                     11:  * 
                     12:  * This Original Code and all software distributed under the License are
                     13:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
                     14:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
                     15:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
                     16:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
                     17:  * License for the specific language governing rights and limitations
                     18:  * under the License.
                     19:  * 
                     20:  * @APPLE_LICENSE_HEADER_END@
                     21:  */
                     22: /*     $NetBSD: lfs_cksum.c,v 1.4 1994/12/14 13:03:46 mycroft Exp $    */
                     23: 
                     24: /*-
                     25:  * Copyright (c) 1991, 1993
                     26:  *     The Regents of the University of California.  All rights reserved.
                     27:  *
                     28:  * Redistribution and use in source and binary forms, with or without
                     29:  * modification, are permitted provided that the following conditions
                     30:  * are met:
                     31:  * 1. Redistributions of source code must retain the above copyright
                     32:  *    notice, this list of conditions and the following disclaimer.
                     33:  * 2. Redistributions in binary form must reproduce the above copyright
                     34:  *    notice, this list of conditions and the following disclaimer in the
                     35:  *    documentation and/or other materials provided with the distribution.
                     36:  * 3. All advertising materials mentioning features or use of this software
                     37:  *    must display the following acknowledgement:
                     38:  *     This product includes software developed by the University of
                     39:  *     California, Berkeley and its contributors.
                     40:  * 4. Neither the name of the University nor the names of its contributors
                     41:  *    may be used to endorse or promote products derived from this software
                     42:  *    without specific prior written permission.
                     43:  *
                     44:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
                     45:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     46:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     47:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
                     48:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     49:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     50:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     51:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     52:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     53:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     54:  * SUCH DAMAGE.
                     55:  *
                     56:  *     @(#)lfs_cksum.c 8.2 (Berkeley) 10/9/94
                     57:  */
                     58: 
                     59: #include <sys/types.h>
                     60: 
                     61: /*
                     62:  * Simple, general purpose, fast checksum.  Data must be short-aligned.
                     63:  * Returns a u_long in case we ever want to do something more rigorous.
                     64:  *
                     65:  * XXX
                     66:  * Use the TCP/IP checksum instead.
                     67:  */
                     68: u_long
                     69: cksum(str, len)
                     70:        register void *str;
                     71:        register size_t len;
                     72: {
                     73:        register u_long sum;
                     74:        
                     75:        len &= ~(sizeof(u_short) - 1);
                     76:        for (sum = 0; len; len -= sizeof(u_short)) {
                     77:                sum ^= *(u_short *)str;
                     78:                str = (void *)((u_short *)str + 1);
                     79:        }
                     80:        return (sum);
                     81: }

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