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/usr.bin/cksum/sum2.c

https://bitbucket.org/freebsd/freebsd-head/
C | 74 lines | 31 code | 8 blank | 35 comment | 3 complexity | 61a0421d4df6672a1d19a5791987f01c 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[] = "@(#)sum2.c	8.1 (Berkeley) 6/6/93";
33#endif
34#endif /* not lint */
35#include <sys/cdefs.h>
36__FBSDID("$FreeBSD$");
37
38#include <sys/types.h>
39
40#include <unistd.h>
41#include <stdint.h>
42
43#include "extern.h"
44
45int
46csum2(int fd, uint32_t *cval, off_t *clen)
47{
48	uint32_t lcrc;
49	int nr;
50	off_t total;
51	u_char *p;
52	u_char buf[8192];
53
54	/*
55	 * Draft 8 POSIX 1003.2:
56	 *
57	 *   s = sum of all bytes
58	 *   r = s % 2^16 + (s % 2^32) / 2^16
59	 * lcrc = (r % 2^16) + r / 2^16
60	 */
61	lcrc = total = 0;
62	while ((nr = read(fd, buf, sizeof(buf))) > 0)
63		for (total += nr, p = buf; nr--; ++p)
64			lcrc += *p;
65	if (nr < 0)
66		return (1);
67
68	lcrc = (lcrc & 0xffff) + (lcrc >> 16);
69	lcrc = (lcrc & 0xffff) + (lcrc >> 16);
70
71	*cval = lcrc;
72	*clen = total;
73	return (0);
74}