/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 1990 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
/*	  All Rights Reserved  	*/

#if defined(sun)
#pragma ident	"@(#)hash.c	1.9	05/09/13 SMI"
#endif

#include "defs.h"

/*
 * This file contains modifications Copyright 2008-2016 J. Schilling
 *
 * @(#)hash.c	1.14 16/06/10 2008-2016 J. Schilling
 */
#ifndef lint
static	UConst char sccsid[] =
	"@(#)hash.c	1.14 16/06/10 2008-2016 J. Schilling";
#endif

#include	"hash.h"

#define	STRCMP(A, B)	(cf(A, B) != 0)
#define	FACTOR		035761254233	/* Magic multiplication factor */
#define	TABLENGTH	64		/* must be multiple of 2 */
#define	LOG2LEN		6		/* log2 of TABLENGTH */

/*
 *  NOTE: The following algorithm only works on machines where
 *  the results of multiplying two integers is the least
 *  significant part of the double word integer required to hold
 *  the result.  It is adapted from Knuth, Volume 3, section 6.4.
 */

#define	hash(str)	(int)(((unsigned)(crunch(str) * FACTOR)) >> shift)

struct node
{
	ENTRY item;
	struct node *next;
};

static struct node	**last;			/* Ptr to begin of hash chain */
static struct node	*next;			/* next == *last */
static struct node	**table;		/* The hash table */

static unsigned int	bitsper;		/* Bits per byte */
static unsigned int	shift;			/* Bits per int - LOG2LEN */

	void	hcreate		__PR((void));
	void	hscan		__PR((void (*uscan)(ENTRY *)));
	ENTRY	*hfund		__PR((unsigned char *str));
	ENTRY	*henter		__PR((ENTRY item));
static unsigned int crunch	__PR((unsigned char *));

/*
 * Create the hash table and initialize parameters.
 */
void
hcreate()
{
	unsigned char c = (unsigned char)~0;	/* A byte full of 1's */
	int j;

	table = (struct node **)alloc(TABLENGTH * sizeof (struct node *));

	for (j = 0; j < TABLENGTH; ++j) {
		table[j] = 0;
	}

	bitsper = 0;

	while (c) {
		c = (unsigned int)c >> 1;
		bitsper++;
	}

	shift = (bitsper * sizeof (int)) - LOG2LEN;
}

/*
 * Scan hash table and call 'uscan' function for every entry.
 */
void
hscan(uscan)
	void	(*uscan) __PR((ENTRY *));
{
	struct node		*p, *nxt;
	int				j;

	for (j = 0; j < TABLENGTH; ++j) {
		p = table[j];
		while (p) {
			nxt = p->next;
			(*uscan)(&p->item);
			p = nxt;
		}
	}
}

/*
 * Find hash entry for 'str', return NULL if not found.
 */
ENTRY *
hfind(str)
	unsigned char	*str;
{
	struct node	*p;
	struct node	**q;
	unsigned int	i;
	int		res = 0;	/* Make GCC happy */

	i = hash(str);

	if (table[i] == 0) {
		last = &table[i];
		next = 0;
		return (0);
	} else {
		q = &table[i];
		p = table[i];
		while (p != 0 && (res = STRCMP(str, p->item.key))) {
			q = &(p->next);
			p = p->next;
		}

		if (p != 0 && res == 0)
			return (&(p->item));
		else {
			last = q;
			next = p;
			return (0);
		}
	}
}

/*
 * Enter new hash node at the place computed by hfind() before.
 */
ENTRY *
henter(item)
	ENTRY item;
{
	struct node	*p = (struct node *)alloc(sizeof (struct node));

	p->item = item;
	*last = p;
	p->next = next;
	return (&(p->item));
}

/*
 * The hash fuction
 */
static unsigned int
crunch(key)
	unsigned char	*key;
{
	unsigned int	sum = 0;
	int s;

	for (s = 0; *key; s++)			/* Simply add up the bytes */
		sum += *key++;

	return (sum + s);			/* Add strlen for quality */
}
