OpenBSD-4.6/usr.sbin/dhcpd/hash.c

/*	$OpenBSD: hash.c,v 1.3 2004/09/16 18:35:43 deraadt Exp $	*/

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

/*
 * 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 "dhcpd.h"

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

struct hash_table *
new_hash(void)
{
	struct hash_table *rv = new_hash_table(DEFAULT_HASH_SIZE, "new_hash");
	if (!rv)
		return (rv);
	memset(&rv->buckets[0], 0,
	    DEFAULT_HASH_SIZE * sizeof(struct hash_bucket *));
	return (rv);
}

static int
do_hash(unsigned char *name, int len, int size)
{
	int accum = 0;
	unsigned char *s = name;
	int 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, unsigned char *name, int len,
    unsigned char *pointer)
{
	int hashno;
	struct hash_bucket *bp;

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

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

	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
delete_hash_entry(struct hash_table *table, unsigned char *name, int len)
{
	int hashno;
	struct hash_bucket *bp, *pbp = NULL;

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

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

	/*
	 * Go through the list looking for an entry that matches; if we
	 * find it, delete it.
	 */
	for (bp = table->buckets[hashno]; bp; bp = bp->next) {
		if ((!bp->len &&
		    !strcmp((char *)bp->name, (char *)name)) ||
		    (bp->len == len && !memcmp(bp->name, name, len))) {
			if (pbp)
				pbp->next = bp->next;
			else
				table->buckets[hashno] = bp->next;
			free_hash_bucket(bp, "delete_hash_entry");
			break;
		}
		pbp = bp;	/* jwg, 9/6/96 - nice catch! */
	}
}

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

	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);
}