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/usr.bin/cksum/sum1.c

https://bitbucket.org/freebsd/freebsd-head/
C | 72 lines | 32 code | 8 blank | 32 comment | 4 complexity | 17fa95b660e191cb5331849562361410 MD5 | raw file
 1/*-
 2 * Copyright (c) 1991, 1993
 3 *	The Regents of the University of California.  All rights reserved.
 4 *
 5 * Redistribution and use in source and binary forms, with or without
 6 * modification, are permitted provided that the following conditions
 7 * are met:
 8 * 1. Redistributions of source code must retain the above copyright
 9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30#ifndef lint
31#if 0
32static char sccsid[] = "@(#)sum1.c	8.1 (Berkeley) 6/6/93";
33#endif
34#endif /* not lint */
35
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD$");
38
39#include <sys/types.h>
40
41#include <unistd.h>
42#include <stdint.h>
43
44#include "extern.h"
45
46int
47csum1(int fd, uint32_t *cval, off_t *clen)
48{
49	int nr;
50	u_int lcrc;
51	off_t total;
52	u_char *p;
53	u_char buf[8192];
54
55	/*
56	 * 16-bit checksum, rotating right before each addition;
57	 * overflow is discarded.
58	 */
59	lcrc = total = 0;
60	while ((nr = read(fd, buf, sizeof(buf))) > 0)
61		for (total += nr, p = buf; nr--; ++p) {
62			if (lcrc & 1)
63				lcrc |= 0x10000;
64			lcrc = ((lcrc >> 1) + *p) & 0xffff;
65		}
66	if (nr < 0)
67		return (1);
68
69	*cval = lcrc;
70	*clen = total;
71	return (0);
72}