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sum2.c revision 1.13 
      1 /*	$NetBSD: sum2.c,v 1.13 2005/02/05 00:13:34 simonb 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[] = "@(#)sum2.c	8.1 (Berkeley) 6/6/93";
     40 #else
     41 __RCSID("$NetBSD: sum2.c,v 1.13 2005/02/05 00:13:34 simonb 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 csum2(int fd, u_int32_t *cval, off_t *clen)
     52 {
     53 	u_int32_t thecrc;
     54 	off_t total;
     55 	int nr;
     56 	u_char *p;
     57 	u_char buf[8192];
     58 
     59 	/*
     60 	 * Draft 8 POSIX 1003.2:
     61 	 *
     62 	 *      s = sum of all bytes
     63 	 *      r = s % 2^16 + (s % 2^32) / 2^16
     64 	 * thecrc = (r % 2^16) + r / 2^16
     65 	 */
     66 	thecrc = 0;
     67 	total = 0;
     68 	while ((nr = read(fd, buf, sizeof(buf))) > 0)
     69 		for (total += nr, p = buf; nr--; ++p)
     70 			thecrc += *p;
     71 	if (nr < 0)
     72 		return 1;
     73 
     74 	thecrc = (thecrc & 0xffff) + (thecrc >> 16);
     75 	thecrc = (thecrc & 0xffff) + (thecrc >> 16);
     76 
     77 	*cval = thecrc;
     78 	*clen = total;
     79 	return 0;
     80 }
     81