usr.bin/cksum/sum2.c

/*-
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static char sccsid[] = "@(#)sum2.c      8.1 (Berkeley) 6/6/93";
#endif /* not lint */

#include <sys/types.h>
#include <unistd.h>

int
csum2(fd, cval, clen)
        register int fd;
        u_long *cval, *clen;
{
        register u_long crc, total;
        register int nr;
        register u_char *p;
        u_char buf[8192];

        /*
         * Draft 8 POSIX 1003.2:
         *
         *   s = sum of all bytes
         *   r = s % 2^16 + (s % 2^32) / 2^16
         * crc = (r % 2^16) + r / 2^16
         */
        crc = total = 0;
        while ((nr = read(fd, buf, sizeof(buf))) > 0)
                for (total += nr, p = buf; nr--; ++p)
                        crc += *p;
        if (nr < 0)
                return(1);

        crc = (crc & 0xffff) + (crc >> 16);
        crc = (crc & 0xffff) + (crc >> 16);

        *cval = crc;
        *clen = total;
        return(0);
}