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Annotation of src/usr.bin/cksum/sum1.c, Revision 1.1

1.1     ! deraadt     1: /*     $NetBSD: sum1.c,v 1.4 1995/03/26 05:15:23 glass 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. All advertising materials mentioning features or use of this software
        !            16:  *    must display the following acknowledgement:
        !            17:  *     This product includes software developed by the University of
        !            18:  *     California, Berkeley and its contributors.
        !            19:  * 4. Neither the name of the University nor the names of its contributors
        !            20:  *    may be used to endorse or promote products derived from this software
        !            21:  *    without specific prior written permission.
        !            22:  *
        !            23:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            24:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            25:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            26:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            27:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            28:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            29:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            30:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            31:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            32:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            33:  * SUCH DAMAGE.
        !            34:  */
        !            35:
        !            36: #ifndef lint
        !            37: #if 0
        !            38: static char sccsid[] = "@(#)sum1.c     8.1 (Berkeley) 6/6/93";
        !            39: #else
        !            40: static char rcsid[] = "$NetBSD: sum1.c,v 1.4 1995/03/26 05:15:23 glass Exp $";
        !            41: #endif
        !            42: #endif /* not lint */
        !            43:
        !            44: #include <sys/types.h>
        !            45: #include <unistd.h>
        !            46:
        !            47: int
        !            48: csum1(fd, cval, clen)
        !            49:        register int fd;
        !            50:        u_long *cval, *clen;
        !            51: {
        !            52:        register u_long total;
        !            53:        register int nr;
        !            54:        register u_int crc;
        !            55:        register u_char *p;
        !            56:        u_char buf[8192];
        !            57:
        !            58:        /*
        !            59:         * 16-bit checksum, rotating right before each addition;
        !            60:         * overflow is discarded.
        !            61:         */
        !            62:        crc = total = 0;
        !            63:        while ((nr = read(fd, buf, sizeof(buf))) > 0)
        !            64:                for (total += nr, p = buf; nr--; ++p) {
        !            65:                        if (crc & 1)
        !            66:                                crc |= 0x10000;
        !            67:                        crc = ((crc >> 1) + *p) & 0xffff;
        !            68:                }
        !            69:        if (nr < 0)
        !            70:                return(1);
        !            71:
        !            72:        *cval = crc;
        !            73:        *clen = total;
        !            74:        return(0);
        !            75: }