/*      $OpenBSD: hash.c,v 1.9 2004/05/10 15:30:47 deraadt Exp $        */

/* Routines for manipulating hash tables... */

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1995, 1996, 1997, 1998 The Internet Software Consortium.
 * 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. Neither the name of The Internet Software Consortium 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 INTERNET SOFTWARE CONSORTIUM 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 INTERNET SOFTWARE CONSORTIUM 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.
 *
 * This software has been written for the Internet Software Consortium
 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
 * Enterprises.  To learn more about the Internet Software Consortium,
 * see ``http://www.vix.com/isc''.  To learn more about Vixie
 * Enterprises, see ``http://www.vix.com''.
 */

#include <sys/cdefs.h>
#include "dhcpd.h"

static int do_hash(const unsigned char *, int, int);

struct hash_table *
new_hash(void)
{
        struct hash_table *rv = new_hash_table(DEFAULT_HASH_SIZE);

        if (!rv)
                return (rv);
        memset(&rv->buckets[0], 0,
            DEFAULT_HASH_SIZE * sizeof(struct hash_bucket *));
        return (rv);
}

static int
do_hash(const unsigned char *name, int len, int size)
{
        const unsigned char *s = name;
        int accum = 0, i = len;

        while (i--) {
                /* Add the character in... */
                accum += *s++;
                /* Add carry back in... */
                while (accum > 255)
                        accum = (accum & 255) + (accum >> 8);
        }
        return (accum % size);
}

void add_hash(struct hash_table *table, const unsigned char *name, int len,
    unsigned char *pointer)
{
        struct hash_bucket *bp;
        int hashno;

        if (!table)
                return;
        if (!len)
                len = strlen((const char *)name);

        hashno = do_hash(name, len, table->hash_count);
        bp = new_hash_bucket();

        if (!bp) {
                warning("Can't add %s to hash table.", name);
                return;
        }
        bp->name = name;
        bp->value = pointer;
        bp->next = table->buckets[hashno];
        bp->len = len;
        table->buckets[hashno] = bp;
}

void *
hash_lookup(struct hash_table *table, unsigned char *name, int len)
{
        struct hash_bucket *bp;
        int hashno;

        if (!table)
                return (NULL);

        if (!len)
                len = strlen((char *)name);

        hashno = do_hash(name, len, table->hash_count);

        for (bp = table->buckets[hashno]; bp; bp = bp->next)
                if (len == bp->len && !memcmp(bp->name, name, len))
                        return (bp->value);

        return (NULL);
}