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Annotation of src/usr.bin/cksum/sum1.c, Revision 1.4

1.4     ! millert     1: /*     $OpenBSD: sum1.c,v 1.3 2001/11/19 19:02:13 mpech Exp $  */
1.2       niklas      2: /*     $NetBSD: sum1.c,v 1.5 1996/02/27 21:17:27 cgd Exp $     */
1.1       deraadt     3:
                      4: /*-
                      5:  * Copyright (c) 1991, 1993
                      6:  *     The Regents of the University of California.  All rights reserved.
                      7:  *
                      8:  * Redistribution and use in source and binary forms, with or without
                      9:  * modification, are permitted provided that the following conditions
                     10:  * are met:
                     11:  * 1. Redistributions of source code must retain the above copyright
                     12:  *    notice, this list of conditions and the following disclaimer.
                     13:  * 2. Redistributions in binary form must reproduce the above copyright
                     14:  *    notice, this list of conditions and the following disclaimer in the
                     15:  *    documentation and/or other materials provided with the distribution.
1.4     ! millert    16:  * 3. Neither the name of the University nor the names of its contributors
1.1       deraadt    17:  *    may be used to endorse or promote products derived from this software
                     18:  *    without specific prior written permission.
                     19:  *
                     20:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
                     21:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     22:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     23:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
                     24:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     25:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     26:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     27:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     28:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     29:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     30:  * SUCH DAMAGE.
                     31:  */
                     32:
                     33: #ifndef lint
                     34: #if 0
                     35: static char sccsid[] = "@(#)sum1.c     8.1 (Berkeley) 6/6/93";
1.2       niklas     36: static char rcsid[] = "$NetBSD: sum1.c,v 1.5 1996/02/27 21:17:27 cgd Exp $";
1.1       deraadt    37: #else
1.4     ! millert    38: static char rcsid[] = "$OpenBSD: sum1.c,v 1.3 2001/11/19 19:02:13 mpech Exp $";
1.1       deraadt    39: #endif
                     40: #endif /* not lint */
                     41:
                     42: #include <sys/types.h>
                     43: #include <unistd.h>
                     44:
1.2       niklas     45: #include "extern.h"
                     46:
1.1       deraadt    47: int
                     48: csum1(fd, cval, clen)
1.3       mpech      49:        int fd;
1.2       niklas     50:        u_int32_t *cval, *clen;
1.1       deraadt    51: {
1.3       mpech      52:        u_int32_t total;
                     53:        int nr;
                     54:        u_int crc;
                     55:        u_char *p;
1.1       deraadt    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: }