xref: /freebsd/usr.bin/cksum/sum1.c (revision 380a989b3223d455375b4fae70fd0b9bdd43bafb)
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  * 3. All advertising materials mentioning features or use of this software
14  *    must display the following acknowledgement:
15  *	This product includes software developed by the University of
16  *	California, Berkeley and its contributors.
17  * 4. Neither the name of the University nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  */
33 
34 #ifndef lint
35 static const char sccsid[] = "@(#)sum1.c	8.1 (Berkeley) 6/6/93";
36 #endif /* not lint */
37 
38 #include <sys/types.h>
39 #include <unistd.h>
40 
41 int
42 csum1(fd, cval, clen)
43 	register int fd;
44 	u_int32_t *cval, *clen;
45 {
46 	register u_int32_t total;
47 	register int nr;
48 	register u_int crc;
49 	register u_char *p;
50 	u_char buf[8192];
51 
52 	/*
53 	 * 16-bit checksum, rotating right before each addition;
54 	 * overflow is discarded.
55 	 */
56 	crc = total = 0;
57 	while ((nr = read(fd, buf, sizeof(buf))) > 0)
58 		for (total += nr, p = buf; nr--; ++p) {
59 			if (crc & 1)
60 				crc |= 0x10000;
61 			crc = ((crc >> 1) + *p) & 0xffff;
62 		}
63 	if (nr < 0)
64 		return(1);
65 
66 	*cval = crc;
67 	*clen = total;
68 	return(0);
69 }
70