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