dxdiskhashiterator.java

Java的面向对象数据库系统的源代码

// You can redistribute this software and/or modify it under the terms of
// the Ozone Library License version 1 published by ozone-db.org.
//
// The original code and portions created by SMB are
// Copyright (C) 1997-@year@ by SMB GmbH. All rights reserved.
//
// $Id: DxDiskHashIterator.java,v 1.2 2002/06/08 00:49:38 mediumnet Exp $

package org.ozoneDB.DxLib;


/**
 * 
 * 
 * @author <a href="http://www.softwarebuero.de/">SMB</a>
 * @version $Revision: 1.2 $Date: 2002/06/08 00:49:38 $
 */
public final class DxDiskHashIterator extends DxAbstractIterator {
    
    final static long serialVersionUID = 1L;
    
    DxKeyData		current;
    
    DxDeque		stack;
    
    DxDiskHashMap	hm;
    
    
    public DxDiskHashIterator( DxDiskHashMap _hm ) {
        hm = _hm;
        reset();
    }
    
    
    public void reset() {
        current = new DxKeyData( null, null );
        
        stack = new DxArrayDeque();

        DxDiskSubTable rootTable = hm.rootTable();


        DxDiskHashNode[] rootTableTables = rootTable.table();

        for (int i = 0; i < rootTableTables.length; i++) {
            if (rootTableTables[i] != null) {
                stack.push( rootTableTables[i] );
            }
        }

//        DxDiskHashNodeBranch nodeBranch = hm.newNodeBranch();
//        nodeBranch.subTable = hm.rootTable();
//        stack.push( nodeBranch );

        nextEntry();
        
        atFirstObject = true;
        objectRemoved = false;
    } 
    
    
    public Object object() {
        return current.data;
    } 
    
    
    public Object key() {
        return current.key;
    } 
    
    
    public Object next() {
        Object obj = object();

        if (atFirstObject) {
            atFirstObject = false;
        } else {
            if (obj != null && !objectRemoved) {
                nextEntry();
                obj = object();
            } 
            objectRemoved = false;
        } 
        return obj;
    }
    
    
    public Object removeObject() {
        throw new UnsupportedOperationException( "removeObject()" );
//        Object obj = object();
//        if (obj != null && !objectRemoved) {
//            DxBBnode delNode = node;
//            if (node.re != null) {
//                node = leftMost( node.re );
//            } else {
//                node = firstRightParent( node );
//            } 
//            bbtree.removeForKey( delNode.key );
//            objectRemoved = true;
//        } 
//        return obj;
    } 


    /**
     * Depth first serach via the stack.
     */
    private void nextEntry() {
        try {
            DxDiskHashNode node = (DxDiskHashNode)stack.pop();
            
            if (node == null) {
                current.set( null, null );
            }
            else  if (node instanceof DxDiskHashNodeLeaf) {
                DxDiskHashNodeLeaf nodeLeaf = (DxDiskHashNodeLeaf)node;
                current.set( nodeLeaf.element().key, nodeLeaf.element().data );
            }
            else  if (node instanceof DxDiskHashNodeBranch) {
                DxDiskHashNodeBranch nodeBranch = (DxDiskHashNodeBranch)node;
                DxDiskHashNode[] table = nodeBranch.subTable.fetchedTable();
                
                for (int i=0; i<table.length; i++) {
                    if (table[i] != null) {
                        stack.push( table[i] );
                    }
                }
                nextEntry();
            }
            else {
                throw new RuntimeException( "Unknown node type: " + node );
            }
        }
        catch (Exception e) {
            throw new RuntimeException( e.toString() );
        }
    }
}