76 lines
2.4 KiB
C
76 lines
2.4 KiB
C
/* $NetBSD: sum1.c,v 1.13 2005/02/05 00:13:34 simonb Exp $ */
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/*-
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* Copyright (c) 1991, 1993
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* The Regents of the University of California. 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 University 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 REGENTS 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 REGENTS 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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#if HAVE_NBTOOL_CONFIG_H
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#include "nbtool_config.h"
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#endif
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#include <sys/cdefs.h>
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#if defined(__RCSID) && !defined(lint)
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#if 0
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static char sccsid[] = "@(#)sum1.c 8.1 (Berkeley) 6/6/93";
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#else
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__RCSID("$NetBSD: sum1.c,v 1.13 2005/02/05 00:13:34 simonb Exp $");
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#endif
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#endif /* not lint */
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#include <sys/types.h>
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#include <unistd.h>
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#include "extern.h"
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int
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csum1(int fd, u_int32_t *cval, off_t *clen)
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{
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off_t total;
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int nr;
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u_int thecrc;
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u_char *p;
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u_char buf[8192];
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/*
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* 16-bit checksum, rotating right before each addition;
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* overflow is discarded.
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*/
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thecrc = total = 0;
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while ((nr = read(fd, buf, sizeof(buf))) > 0)
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for (total += nr, p = buf; nr--; ++p) {
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if (thecrc & 1)
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thecrc |= 0x10000;
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thecrc = ((thecrc >> 1) + *p) & 0xffff;
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}
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if (nr < 0)
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return 1;
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*cval = thecrc;
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*clen = total;
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return 0;
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}
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