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/*-

 * Copyright (c) 1990, 1993

 *      The Regents of the University of California.  All rights reserved.

 *

 * This code is derived from software contributed to Berkeley by

 * Margo Seltzer.

 *

 * 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.

 */

#if defined(LIBC_SCCS) && !defined(lint)

static char sccsid[] = "@(#)hash_func.c 8.2 (Berkeley) 2/21/94";

#endif /* LIBC_SCCS and not lint */

#include <sys/cdefs.h>

#include <sys/types.h>

#include "db_local.h"

#include "hash.h"

#include "page.h"

#include "extern.h"

#if 0

static __uint32_t hash1(const void *, size_t);

static __uint32_t hash2(const void *, size_t);

static __uint32_t hash3(const void *, size_t);

#endif

static __uint32_t hash4(const void *, size_t);

/* Global default hash function */

__uint32_t (*__default_hash)(const void *, size_t) = hash4;

/*

 * HASH FUNCTIONS

 *

 * Assume that we've already split the bucket to which this key hashes,

 * calculate that bucket, and check that in fact we did already split it.

 *

 * This came from ejb's hsearch.

 */

#define PRIME1          37

#define PRIME2          1048583

#if 0

static __uint32_t

hash1(keyarg, len)

        const void *keyarg;

        size_t len;

{

        const u_char *key;

        __uint32_t h;

        /* Convert string to integer */

        for (key = keyarg, h = 0; len--;)

                h = h * PRIME1 ^ (*key++ - ' ');

        h %= PRIME2;

        return (h);

}

#endif

/*

 * Phong's linear congruential hash

 */

#define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))

#if 0

static __uint32_t

hash2(keyarg, len)

        const void *keyarg;

        size_t len;

{

        const u_char *e, *key;

        __uint32_t h;

        u_char c;

        key = keyarg;

        e = key + len;

        for (h = 0; key != e;) {

                c = *key++;

                if (!c && key > e)

                        break;

                dcharhash(h, c);

        }

        return (h);

}

#endif

/*

 * This is INCREDIBLY ugly, but fast.  We break the string up into 8 byte

 * units.  On the first time through the loop we get the "leftover bytes"

 * (strlen % 8).  On every other iteration, we perform 8 HASHC's so we handle

 * all 8 bytes.  Essentially, this saves us 7 cmp & branch instructions.  If

 * this routine is heavily used enough, it's worth the ugly coding.

 *

 * OZ's original sdbm hash

 */

#if 0

static __uint32_t

hash3(keyarg, len)

        const void *keyarg;

        size_t len;

{

        const u_char *key;

        size_t loop;

        __uint32_t h;

#define HASHC   h = *key++ + 65599 * h

        h = 0;

        key = keyarg;

        if (len > 0) {

                loop = (len + 8 - 1) >> 3;

                switch (len & (8 - 1)) {

                case 0:

                        do {

                                HASHC;

                                /* FALLTHROUGH */

                case 7:

                                HASHC;

                                /* FALLTHROUGH */

                case 6:

                                HASHC;

                                /* FALLTHROUGH */

                case 5:

                                HASHC;

                                /* FALLTHROUGH */

                case 4:

                                HASHC;

                                /* FALLTHROUGH */

                case 3:

                                HASHC;

                                /* FALLTHROUGH */

                case 2:

                                HASHC;

                                /* FALLTHROUGH */

                case 1:

                                HASHC;

                        } while (--loop);

                }

        }

        return (h);

}

#endif

/* Hash function from Chris Torek. */

static __uint32_t

hash4(keyarg, len)

        const void *keyarg;

        size_t len;

{

        const u_char *key;

        size_t loop;

        __uint32_t h;

#define HASH4a   h = (h << 5) - h + *key++;

#define HASH4b   h = (h << 5) + h + *key++;

#define HASH4 HASH4b

        h = 0;

        key = keyarg;

        if (len > 0) {

                loop = (len + 8 - 1) >> 3;

                switch (len & (8 - 1)) {

                case 0:

                        do {

                                HASH4;

                                /* FALLTHROUGH */

                case 7:

                                HASH4;

                                /* FALLTHROUGH */

                case 6:

                                HASH4;

                                /* FALLTHROUGH */

                case 5:

                                HASH4;

                                /* FALLTHROUGH */

                case 4:

                                HASH4;

                                /* FALLTHROUGH */

                case 3:

                                HASH4;

                                /* FALLTHROUGH */

                case 2:

                                HASH4;

                                /* FALLTHROUGH */

                case 1:

                                HASH4;

                        } while (--loop);

                }

        }

        return (h);

}