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Annotation of src/usr.bin/cvs/hash_func.c, Revision 1.1

1.1     ! joris       1: /*     $OpenBSD: hash_func.c,v 1.10 2005/08/05 13:03:00 espie Exp $    */
        !             2:
        !             3: /*-
        !             4:  * Copyright (c) 1990, 1993
        !             5:  *     The Regents of the University of California.  All rights reserved.
        !             6:  *
        !             7:  * This code is derived from software contributed to Berkeley by
        !             8:  * Margo Seltzer.
        !             9:  *
        !            10:  * Redistribution and use in source and binary forms, with or without
        !            11:  * modification, are permitted provided that the following conditions
        !            12:  * are met:
        !            13:  * 1. Redistributions of source code must retain the above copyright
        !            14:  *    notice, this list of conditions and the following disclaimer.
        !            15:  * 2. Redistributions in binary form must reproduce the above copyright
        !            16:  *    notice, this list of conditions and the following disclaimer in the
        !            17:  *    documentation and/or other materials provided with the distribution.
        !            18:  * 3. Neither the name of the University nor the names of its contributors
        !            19:  *    may be used to endorse or promote products derived from this software
        !            20:  *    without specific prior written permission.
        !            21:  *
        !            22:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            23:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            24:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            25:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            26:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            27:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            28:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            29:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            30:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            31:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            32:  * SUCH DAMAGE.
        !            33:  */
        !            34:
        !            35: #include <sys/types.h>
        !            36: #include <sys/queue.h>
        !            37:
        !            38: #include "hash.h"
        !            39:
        !            40: /* Chris Torek's hash function. */
        !            41: u_int32_t
        !            42: hash4(const char *key, size_t len)
        !            43: {
        !            44:        u_int32_t h, loop;
        !            45:        const char *k;
        !            46:
        !            47: #define HASH4   h = (h << 5) + h + *k++;
        !            48:
        !            49:        h = 0;
        !            50:        k = key;
        !            51:        if (len > 0) {
        !            52:                loop = (len + 8 - 1) >> 3;
        !            53:
        !            54:                switch (len & (8 - 1)) {
        !            55:                case 0:
        !            56:                        do {    /* All fall throughs */
        !            57:                                HASH4;
        !            58:                case 7:
        !            59:                                HASH4;
        !            60:                case 6:
        !            61:                                HASH4;
        !            62:                case 5:
        !            63:                                HASH4;
        !            64:                case 4:
        !            65:                                HASH4;
        !            66:                case 3:
        !            67:                                HASH4;
        !            68:                case 2:
        !            69:                                HASH4;
        !            70:                case 1:
        !            71:                                HASH4;
        !            72:                        } while (--loop);
        !            73:                }
        !            74:
        !            75:        }
        !            76:        return (h);
        !            77: }