/*
 * $Header: /home/barad-dur/vision/forsyth/schenney/sced-0.94/c/RCS/hash.c,v 1.0 1997/05/06 20:30:22 schenney Exp $
 *
 * $Log: hash.c,v $
 * Revision 1.0  1997/05/06 20:30:22  schenney
 * Initial revision
 *
 */
#define PATCHLEVEL 0
/*
**    ScEd: A Constraint Based Scene Editor.
**    Copyright (C) 1994-1998  Stephen Chenney (schenney@cs.berkeley.edu)
**
**    This program is free software; you can redistribute it and/or modify
**    it under the terms of the GNU General Public License as published by
**    the Free Software Foundation; either version 2 of the License, or
**    (at your option) any later version.
**
**    This program is distributed in the hope that it will be useful,
**    but WITHOUT ANY WARRANTY; without even the implied warranty of
**    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
**    GNU General Public License for more details.
**
**    You should have received a copy of the GNU General Public License
**    along with this program; if not, write to the Free Software
**    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/*
**  sced: A Constraint Based Object Scene Editor
**
**  hash.c: Hash table functions for storing pointer mappings.
*/

#include <sced.h>
#include <hash.h>


#define HASH_PRIME 197
#define HASH_SIZE ( 197 / 2 + 1 )
#define HASH_INDEX ( ( key % HASH_PRIME ) >> 1 )

HashTable
Hash_New_Table()
{
    HashTable   new_hash = New(HashEntryPtr, HASH_SIZE);
    int i;

    for ( i = 0 ; i < HASH_SIZE ; i++ )
        new_hash[i] = NULL;
    return new_hash;
}


void
Hash_Insert(HashTable table, unsigned long key, void *value)
{
    int             index = HASH_INDEX;
    HashEntryPtr    entry = table[index];
    HashEntryPtr    new_entry;

    while ( entry )
    {
        if ( entry->key == key )
            return;
        entry = entry->next;
    }
    new_entry = New(HashEntry, 1);
    new_entry->next = table[index];
    new_entry->key = key;
    new_entry->value = value;
    table[index] = new_entry;
}


void*
Hash_Get_Value(HashTable table, unsigned long key)
{
    HashEntryPtr    entry = table[HASH_INDEX];

    while ( entry && entry->key != key )
        entry = entry->next;
    if ( entry )
        return entry->value;
    else
        return (void*)-1;
}


void
Hash_Free_List(HashEntryPtr victim)
{
    if ( victim )
    {
        Hash_Free_List(victim->next);
        free(victim);
    }
}


void
Hash_Clear(HashTable table)
{
    int i;

    for ( i = 0 ; i < HASH_SIZE ; i++ )
        if ( table[i] ) Hash_Free_List(table[i]);
}

void
Hash_Free(HashTable table)
{
    Hash_Clear(table);
    free(table);
}


void*
Hash_Delete(HashTable table, unsigned long key)
{
    HashEntryPtr    entry = table[HASH_INDEX];
    void            *val;

    if ( ! entry )
        return NULL;

    if ( entry->key == key )
    {
        table[HASH_INDEX] = entry->next;
        val = entry->value;
        free(entry);
        return val;
    }

    while ( entry->next && entry->next->key != key )
        entry = entry->next;

    if ( entry->next && entry->next->key == key )
    {
        HashEntryPtr    temp = entry->next;

        val = entry->next->value;
        entry->next = entry->next->next;
        free(temp);
        return val;
    }

    return NULL;
}


void*
Hash_Traverse(HashTable table, Boolean starting)
{
    static HashEntryPtr next;
    static int          index;
    void                *result;

    if ( starting )
    {
        for ( index = 0 ; index < HASH_SIZE && ! table[index] ; index++ );
        if ( index < HASH_SIZE )
            next = table[index];
        else
            next = NULL;
    }

    result = next ? next->value : NULL;

    if ( next && next->next )
        next = next->next;
    else
    {
        for ( index++ ; index < HASH_SIZE && ! table[index] ; index++ );
        if ( index < HASH_SIZE )
            next = table[index];
        else
            next = NULL;
    }

    return result;
}