/* @(#)hashtable.c	17.1.1.1 (ESO-IPG) 01/25/02 17:26:43 */
/*---------------------------------------------------------------------
 * $Date: 93/07/12 18:31:00 $             $Revision: 2.2.6.1 $
 *---------------------------------------------------------------------
 * 
 *
 *             Copyright (c) 1992, Visual Edge Software Ltd.
 *
 * ALL  RIGHTS  RESERVED.  Permission  to  use,  copy,  modify,  and
 * distribute  this  software  and its documentation for any purpose
 * and  without  fee  is  hereby  granted,  provided  that the above
 * copyright  notice  appear  in  all  copies  and  that  both  that
 * copyright  notice and this permission notice appear in supporting
 * documentation,  and that  the name of Visual Edge Software not be
 * used  in advertising  or publicity  pertaining to distribution of
 * the software without specific, written prior permission. The year
 * included in the notice is the year of the creation of the work.
 *-------------------------------------------------------------------*/
/*
 * Copyright 1990, 1991 GROUPE BULL
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose and without fee is hereby granted, provided
 * that the above copyright notice appear in all copies and that both that
 * copyright notice and this permission notice appear in supporting
 * documentation, and that the name of GROUPE BULL not be used in advertising
 * or publicity pertaining to distribution of the software without specific,
 * written prior permission.  GROUPE BULL makes no representations about the
 * suitability of this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 *
 * GROUPE BULL disclaims all warranties with regard to this software,
 * including all implied warranties of merchantability and fitness,
 * in no event shall GROUPE BULL be liable for any special,
 * indirect or consequential damages or any damages
 * whatsoever resulting from loss of use, data or profits,
 * whether in an action of contract, negligence or other tortious
 * action, arising out of or in connection with the use 
 * or performance of this software.
 *
 */

/*****************************************************************************\
* hashtable.c:                                                                *
*                                                                             *
*  XPM library                                                                *
*                                                                             *
*  Developed by Arnaud Le Hors                                                *
*  this originaly comes from Colas Nahaboo as a part of Wool                  *
*                                                                             *
\*****************************************************************************/

#include "xpmP.h"

LFUNC(AtomMake, xpmHashAtom, (char *name, void *data));
LFUNC(HashTableGrows, int, (xpmHashTable *table));

static xpmHashAtom
AtomMake(name, data)			/* makes an atom */
    char *name;				/* WARNING: is just pointed to */
    void *data;
{
    xpmHashAtom object = (xpmHashAtom) malloc(sizeof(struct _xpmHashAtom));
    if (object) {
	object->name = name;
	object->data = data;
    }
    return object;
}

/************************\
* 			 *
*  hash table routines 	 *
* 			 *
\************************/

/*
 * Hash function definition:
 * HASH_FUNCTION: hash function, hash = hashcode, hp = pointer on char,
 *				 hash2 = temporary for hashcode.
 * INITIAL_TABLE_SIZE in slots
 * HASH_TABLE_GROWS how hash table grows.
 */

/* Mock lisp function */
/*
#define HASH_FUNCTION 	  hash = (hash << 5) - hash + *hp++;
#define INITIAL_HASH_SIZE 2017
#define HASH_TABLE_GROWS  size = size * 2;
*/

/* aho-sethi-ullman's HPJ (sizes should be primes)*/

#define HASH_FUNCTION	hash <<= 4; hash += *hp++; \
    if(hash2 = hash & 0xf0000000) hash ^= (hash2 >> 24) ^ hash2;
/* #define INITIAL_HASH_SIZE 4095 */		/* should be 2^n - 1 */
#define INITIAL_HASH_SIZE 288		/* should be enough for colors */
#define HASH_TABLE_GROWS  size = size << 1 + 1;

/* GNU emacs function */
/*
#define HASH_FUNCTION 	  hash = (hash << 3) + (hash >> 28) + *hp++;
#define INITIAL_HASH_SIZE 2017
#define HASH_TABLE_GROWS  size = size * 2;
*/

/* end of hash functions */

/*
 * The hash table is used to store atoms via their NAME:
 *
 * NAME --hash--> ATOM |--name--> "foo"
 *		       |--data--> any value which has to be stored
 *
 */

/*
 * xpmHashSlot gives the slot (pointer to xpmHashAtom) of a name
 * (slot points to NULL if it is not defined)
 *
 */

xpmHashAtom *
xpmHashSlot(table, s)
    xpmHashTable *table;
    char *s;
{
    xpmHashAtom *atomTable = table->atomTable;
    unsigned int hash, hash2;
    xpmHashAtom *p;
    char *hp = s;
    char *ns;

    hash = 0;
    while (*hp) {			/* computes hash function */
	HASH_FUNCTION
    }
    p = atomTable + hash % table->size;
    while (*p) {
	ns = (*p)->name;
	if (ns[0] == s[0] && strcmp(ns, s) == 0)
	    break;
	p--;
	if (p < atomTable)
	    p = atomTable + table->size - 1;
    }
    return p;
}

static int
HashTableGrows(table)
    xpmHashTable *table;
{
    xpmHashAtom *atomTable = table->atomTable;
    int size = table->size;
    xpmHashAtom *t, *p;
    int i;
    int oldSize = size;

    t = atomTable;
    HASH_TABLE_GROWS
	table->size = size;
    table->limit = size / 3;
    atomTable = (xpmHashAtom *) malloc(size * sizeof(*atomTable));
    table->atomTable = atomTable;
    for (p = atomTable + size; p > atomTable;)
	*--p = NULL;
    for (i = 0, p = t; i < oldSize; i++, p++)
	if (*p) {
	    xpmHashAtom *ps = xpmHashSlot(table, (*p)->name);
	    *ps = *p;
	}
    free(t);
}

/*
 * xpmHashIntern(table, name, data)
 * return an xpmHashAtom, which is the one at the slot, if present,
 * or is created if name didn't exist, with the given data.
 */

xpmHashAtom
xpmHashIntern(table, tag, data)
    xpmHashTable *table;
    char *tag;
    void *data;
{
    xpmHashAtom *slot;

    if (!*(slot = xpmHashSlot(table, tag))) {
	/* undefined, make a new atom with the given data */
        *slot = AtomMake(tag, data);

	if (table->used >= table->limit) {
	    xpmHashAtom new = *slot;

	    HashTableGrows(table);
	    table->used++;
	    return new;
	}
	table->used++;
    }
    return *slot;
}

/*
 *  must be called before allocating any atom
 */

xpmHashTableInit(table)
    xpmHashTable *table;
{
    xpmHashAtom *p;
    xpmHashAtom *atomTable;

    table->size = INITIAL_HASH_SIZE;
    table->limit = table->size / 3;
    table->used = 0;
    atomTable = (xpmHashAtom *) malloc(table->size * sizeof(*atomTable));
    if (atomTable)
	for (p = atomTable + table->size; p > atomTable;)
	    *--p = NULL;
    table->atomTable = atomTable;
}

/*
 *   frees a hashtable and all the stored atoms
 */

xpmHashTableFree(table)
    xpmHashTable *table;
{
    xpmHashAtom *p;
    xpmHashAtom *atomTable = table->atomTable;
    for (p = atomTable + table->size; p > atomTable;)
	if (*--p)
	    free(*p);
    free(atomTable);
    table->atomTable = NULL;
}