usr.bin/cksum/sum1.c

   1 /*      $NetBSD: sum1.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[] = "@(#)sum1.c      8.1 (Berkeley) 6/6/93";
  40 #else
  41 __RCSID("$NetBSD: sum1.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 csum1(int fd, u_int32_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 }