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sum1.c revision 1.7 
      1 /*	$NetBSD: sum1.c,v 1.7 2001/03/21 03:16:38 atatat 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. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *	This product includes software developed by the University of
     18  *	California, Berkeley and its contributors.
     19  * 4. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  */
     35 
     36 #include <sys/cdefs.h>
     37 #ifndef lint
     38 #if 0
     39 static char sccsid[] = "@(#)sum1.c	8.1 (Berkeley) 6/6/93";
     40 #else
     41 __RCSID("$NetBSD: sum1.c,v 1.7 2001/03/21 03:16:38 atatat 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(fd, cval, clen)
     52 	register int fd;
     53 	u_int32_t *cval, *clen;
     54 {
     55 	register u_int32_t total;
     56 	register int nr;
     57 	register u_int thecrc;
     58 	register u_char *p;
     59 	u_char buf[8192];
     60 
     61 	/*
     62 	 * 16-bit checksum, rotating right before each addition;
     63 	 * overflow is discarded.
     64 	 */
     65 	thecrc = total = 0;
     66 	while ((nr = read(fd, buf, sizeof(buf))) > 0)
     67 		for (total += nr, p = buf; nr--; ++p) {
     68 			if (thecrc & 1)
     69 				thecrc |= 0x10000;
     70 			thecrc = ((thecrc >> 1) + *p) & 0xffff;
     71 		}
     72 	if (nr < 0)
     73 		return(1);
     74 
     75 	*cval = thecrc;
     76 	*clen = total;
     77 	return(0);
     78 }
     79