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. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#)sum1.c   8.1 (Berkeley) 6/6/93
  34  * $FreeBSD: src/usr.bin/cksum/sum1.c,v 1.4 1999/12/05 20:03:22 charnier Exp $
  35  * $DragonFly: src/usr.bin/cksum/sum1.c,v 1.4 2005/04/10 20:55:38 drhodus Exp $
  36  */
  37
  38 #include <sys/types.h>
  39 #include <unistd.h>
  40
  41 int
  42 csum1(int fd, u_int32_t *cval, u_int32_t *clen)
  43 {
  44         u_int32_t total;
  45         int nr;
  46         u_int crc;
  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         crc = total = 0;
  55         while ((nr = read(fd, buf, sizeof(buf))) > 0)
  56                 for (total += nr, p = buf; nr--; ++p) {
  57                         if (crc & 1)
  58                                 crc |= 0x10000;
  59                         crc = ((crc >> 1) + *p) & 0xffff;
  60                 }
  61         if (nr < 0)
  62                 return(1);
  63
  64         *cval = crc;
  65         *clen = total;
  66         return(0);
  67 }