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sum1.c revision 1.10 
      1 /*	$NetBSD: sum1.c,v 1.10 2003/12/20 23:41:38 kleink 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 #include <sys/cdefs.h>
     33 #if defined(__RCSID) && !defined(lint)
     34 #if 0
     35 static char sccsid[] = "@(#)sum1.c	8.1 (Berkeley) 6/6/93";
     36 #else
     37 __RCSID("$NetBSD: sum1.c,v 1.10 2003/12/20 23:41:38 kleink Exp $");
     38 #endif
     39 #endif /* not lint */
     40 
     41 #include <sys/types.h>
     42 #include <unistd.h>
     43 
     44 #include "extern.h"
     45 
     46 int
     47 csum1(fd, cval, clen)
     48 	register int fd;
     49 	u_int32_t *cval;
     50 	off_t *clen;
     51 {
     52 	register off_t total;
     53 	register int nr;
     54 	register u_int thecrc;
     55 	register u_char *p;
     56 	u_char buf[8192];
     57 
     58 	/*
     59 	 * 16-bit checksum, rotating right before each addition;
     60 	 * overflow is discarded.
     61 	 */
     62 	thecrc = total = 0;
     63 	while ((nr = read(fd, buf, sizeof(buf))) > 0)
     64 		for (total += nr, p = buf; nr--; ++p) {
     65 			if (thecrc & 1)
     66 				thecrc |= 0x10000;
     67 			thecrc = ((thecrc >> 1) + *p) & 0xffff;
     68 		}
     69 	if (nr < 0)
     70 		return(1);
     71 
     72 	*cval = thecrc;
     73 	*clen = total;
     74 	return(0);
     75 }
     76