usr.bin/cksum/sum1.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * @(#)sum1.c   8.1 (Berkeley) 6/6/93
  30  * $FreeBSD: src/usr.bin/cksum/sum1.c,v 1.8 2003/03/13 23:32:28 robert Exp $
  31  * $DragonFly: src/usr.bin/cksum/sum1.c,v 1.4 2005/04/10 20:55:38 drhodus Exp $
  32  */
  33
  34 #include <sys/types.h>
  35
  36 #include <unistd.h>
  37 #include <stdint.h>
  38
  39 #include "extern.h"
  40
  41 int
  42 csum1(int fd, uint32_t *cval, off_t *clen)
  43 {
  44         int nr;
  45         u_int lcrc;
  46         off_t total;
  47         u_char *p;
  48         u_char buf[8192];
  49
  50         /*
  51          * 16-bit checksum, rotating right before each addition;
  52          * overflow is discarded.
  53          */
  54         lcrc = total = 0;
  55         while ((nr = read(fd, buf, sizeof(buf))) > 0)
  56                 for (total += nr, p = buf; nr--; ++p) {
  57                         if (lcrc & 1)
  58                                 lcrc |= 0x10000;
  59                         lcrc = ((lcrc >> 1) + *p) & 0xffff;
  60                 }
  61         if (nr < 0)
  62                 return (1);
  63
  64         *cval = lcrc;
  65         *clen = total;
  66         return (0);
  67 }