105 lines
3.4 KiB
C
105 lines
3.4 KiB
C
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/* $NetBSD: crc.c,v 1.1 2000/01/28 19:32:47 itojun Exp $ */
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/*
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* Copyright (C) 1999 LSIIT Laboratory.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the project nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* Questions concerning this software should be directed to
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* Mickael Hoerdt (hoerdt@clarinet.u-strasbg.fr) LSIIT Strasbourg.
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*
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*/
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/*
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* This program has been derived from pimd.
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* The pimd program is covered by the license in the accompanying file
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* named "LICENSE.pimd".
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*
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*/
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/* CRC implantation : stolen from RFC 2083 section 15.*/
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#include <sys/cdefs.h>
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#include "crc.h"
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/* Table of CRCs of all 8-bit messages. */
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unsigned long crc_table[256];
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/* Flag: has the table been computed? Initially false. */
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int crc_table_computed = 0;
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/* Make the table for a fast CRC. */
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static void make_crc_table __P((void));
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static unsigned long update_crc __P((unsigned long, unsigned char *, int));
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static void make_crc_table(void)
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{
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unsigned long c;
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int n, k;
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for (n = 0; n < 256; n++)
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{
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c = (unsigned long) n;
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for (k = 0; k < 8; k++)
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{
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if (c & 1)
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c = 0xedb88320L ^ (c >> 1);
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else
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c = c >> 1;
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}
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crc_table[n] = c;
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}
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crc_table_computed = 1;
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}
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/* Update a running CRC with the bytes buf[0..len-1]--the CRC
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should be initialized to all 1's, and the transmitted value
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is the 1's complement of the final running CRC (see the
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crc() routine below)). */
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static unsigned long update_crc(unsigned long crc, unsigned char *buf,
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int len)
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{
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unsigned long c = crc;
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int n;
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if (!crc_table_computed)
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make_crc_table();
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for (n = 0; n < len; n++)
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{
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c = crc_table[(c ^ buf[n]) & 0xff] ^ (c >> 8);
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}
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return c;
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}
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/* Return the CRC of the bytes buf[0..len-1]. */
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unsigned long crc(unsigned char *buf, int len)
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{
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return update_crc(0xffffffffL, buf, len) ^ 0xffffffffL;
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}
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