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      1 /*	$NetBSD: sum1.c,v 1.14 2021/03/18 18:12:35 cheusov Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1991, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. Neither the name of the University nor the names of its contributors
     16  *    may be used to endorse or promote products derived from this software
     17  *    without specific prior written permission.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     29  * SUCH DAMAGE.
     30  */
     31 
     32 #if HAVE_NBTOOL_CONFIG_H
     33 #include "nbtool_config.h"
     34 #endif
     35 
     36 #include <sys/cdefs.h>
     37 #if defined(__RCSID) && !defined(lint)
     38 #if 0
     39 static char sccsid[] = "@(#)sum1.c	8.1 (Berkeley) 6/6/93";
     40 #else
     41 __RCSID("$NetBSD: sum1.c,v 1.14 2021/03/18 18:12:35 cheusov Exp $");
     42 #endif
     43 #endif /* not lint */
     44 
     45 #include <sys/types.h>
     46 #include <unistd.h>
     47 
     48 #include "extern.h"
     49 
     50 int
     51 csum1(int fd, uint32_t *cval, off_t *clen)
     52 {
     53 	off_t total;
     54 	int nr;
     55 	u_int thecrc;
     56 	u_char *p;
     57 	u_char buf[8192];
     58 
     59 	/*
     60 	 * 16-bit checksum, rotating right before each addition;
     61 	 * overflow is discarded.
     62 	 */
     63 	thecrc = total = 0;
     64 	while ((nr = read(fd, buf, sizeof(buf))) > 0)
     65 		for (total += nr, p = buf; nr--; ++p) {
     66 			if (thecrc & 1)
     67 				thecrc |= 0x10000;
     68 			thecrc = ((thecrc >> 1) + *p) & 0xffff;
     69 		}
     70 	if (nr < 0)
     71 		return 1;
     72 
     73 	*cval = thecrc;
     74 	*clen = total;
     75 	return 0;
     76 }
     77