dxbbiterator.java

用Java写的面相对象的数据库管理系统

// 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) 1997-2000 by SMB GmbH. All rights reserved.
//
// $Id: DxBBIterator.java,v 1.5 2000/10/28 16:55:14 daniela Exp $

package org.ozoneDB.DxLib;

/**
 * 
 * 
 * @author <a href="http://www.softwarebuero.de/">SMB</a>
 * @version $Revision: 1.5 $Date: 2000/10/28 16:55:14 $
 */
public final class DxBBIterator extends DxAbstractIterator {
    
    final static long serialVersionUID = 1L;
    
    DxBBTree bbtree;
    DxBBnode node;
    
    
    /**
     */
    public DxBBIterator( DxTreeCollection _coll ) {
        bbtree = _coll.internalTree();
        reset();
    }
    
    
    /**
     */
    public Object object() {
        return node != null ? node.data : null;
    } 
    
    
    /**
     */
    public Object key() {
        return node != null ? node.key : null;
    } 
    
    
    /**
     */
    public Object next() {
        Object obj = object();
        if (atFirstObject) {
            atFirstObject = false;
        } else {
            if (obj != null && !objectRemoved) {
                if (node.re != null) {
                    node = leftMost( node.re );
                } else {
                    node = firstRightParent( node );
                } 
                obj = object();
            } 
            objectRemoved = false;
        } 
        return obj;
    } 
    
    
    /**
     */
    public void reset() {
        node = leftMost( bbtree.root() );
        atFirstObject = true;
        objectRemoved = false;
    } 
    
    
    /**
     */
    public Object 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;
    } 
    
    
    /**
     */
    private DxBBnode leftMost( DxBBnode node ) {
        if (node != null && node.li != null) {
            return leftMost( node.li );
        } 
        return node;
    } 
    
    
    /**
     */
    private DxBBnode firstRightParent( DxBBnode node ) {
        if (node == bbtree.quietRoot) {
            return null;
        } 
        if (node.isRight) {
            return firstRightParent( node.pa );
        } 
        return node.pa;
    } 
}