/*
 * $Copyright:	$
 * Copyright (c) 1984, 1985, 1986, 1987, 1988, 1989, 1990 
 * Sequent Computer Systems, Inc.   All rights reserved.
 *  
 * This software is furnished under a license and may be used
 * only in accordance with the terms of that license and with the
 * inclusion of the above copyright notice.   This software may not
 * be provided or otherwise made available to, or used by, any
 * other person.  No title to or ownership of the software is
 * hereby transferred.
 *
 */

/*	Copyright (c) 1984 AT&T	*/
/*	  All Rights Reserved  	*/

/*	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF AT&T	*/
/*	The copyright notice above does not evidence any   	*/
/*	actual or intended publication of such source code.	*/

#ident	"$Header: hash.c 1.4 89/10/10 $@(#)sh:hash.c	1.3"

#include	"hash.h"
#include	"defs.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;
static struct node	*next;
static struct node 	**table;

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

static unsigned int crunch();

hcreate()
{
	unsigned char c = ~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 >>= 1;
		bitsper++;
	}

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


void hscan(uscan)	
	void	(*uscan)();
{
	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;
		}
	}
}



ENTRY *
hfind(str)
	unsigned char	*str;
{
	struct node 	*p;
	struct node 	**q;
	unsigned int 	i;
	int 			res;		

	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);
		}
	}
}

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));
}


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);
}

