lazyrowrowiterator.java

开源的axion的数据库代码

/*
 * $Id: LazyRowRowIterator.java,v 1.7 2003/05/15 17:25:40 rwald Exp $
 * =======================================================================
 * Copyright (c) 2002-2003 Axion Development Team.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above
 *    copyright notice, this list of conditions and the following
 *    disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The names "Tigris", "Axion", nor the names of its contributors may
 *    not be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * 4. Products derived from this software may not be called "Axion", nor
 *    may "Tigris" or "Axion" appear in their names without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * =======================================================================
 */

package org.axiondb.engine.rowiterators;

import java.util.ListIterator;
import java.util.NoSuchElementException;

import org.apache.commons.collections.primitives.IntListIterator;
import org.apache.commons.collections.primitives.adapters.ListIteratorIntListIterator;
import org.axiondb.Row;
import org.axiondb.RowSource;
import org.axiondb.engine.LazyRow;

/**
 * A {@link org.axiondb.RowIterator} that creates
 * {@link LazyRow}s based upon a list of {@link Row} identifiers.
 * 
 * @version $Revision: 1.7 $ $Date: 2003/05/15 17:25:40 $
 * @author Rodney Waldhoff
 */
public class LazyRowRowIterator extends BaseRowIterator {

    public LazyRowRowIterator(RowSource source, IntListIterator rowIdIter) {
        this(source,rowIdIter,-1,null);
    }

    /** @deprecated use {@link LazyRowRowIteratorLazyRowRowIterator(RowSource,IntListIterator,int,valueIter)} instead. */
    public LazyRowRowIterator(RowSource source, ListIterator rowIdIter, int knownColumn, ListIterator valueIter) {
        this(source,ListIteratorIntListIterator.wrap(rowIdIter),knownColumn,valueIter);
    }

    public LazyRowRowIterator(RowSource source, IntListIterator rowIdIter, int knownColumn, ListIterator valueIter) {
        _source = source;
        _rowIdIter = rowIdIter;
        _knownColumnIndex = knownColumn;
        _valueIter = valueIter;
    }

    public Row current() {
        if(hasCurrent()) {
            return _currentRow;
        } else {
            throw new NoSuchElementException("No current row has been set.");
        }
    }

    public boolean hasCurrent() {
        return (null == _currentRow);
    }

    public void add(Row row) {
        throw new UnsupportedOperationException("Not supported");
    }

    public boolean hasNext() {
        return _rowIdIter.hasNext();
    }

    public boolean hasPrevious() {
        return _rowIdIter.hasPrevious();
    }

    public Row next() {
        _currentIndex = _rowIdIter.nextIndex();
        setCurrentRow(_rowIdIter.next(),(null == _valueIter ? null : _valueIter.next()));
        return _currentRow;
    }

    public Row previous() {
        setCurrentRow(_rowIdIter.previous(),(null == _valueIter ? null : _valueIter.previous()));
        _currentIndex = _rowIdIter.nextIndex();
        return _currentRow;
    }

    public int currentIndex() {
        return _currentIndex;
    }

    public int nextIndex() {
        return _rowIdIter.nextIndex();
    }

    public int previousIndex() {
        return _rowIdIter.previousIndex();
    }

    public void remove() {
        throw new UnsupportedOperationException("Not supported");
    }

    public void set(Row row) {
        throw new UnsupportedOperationException("Not supported");
    }

    public void reset() {
        while(_rowIdIter.hasPrevious()) {
            _rowIdIter.previous();
            if(null != _valueIter) {
                _valueIter.previous();
            }
        }
        _currentRow = null;
        _currentIndex = -1;
    }

    private final void setCurrentRow(int rowid, Object value) {
        _currentRow = new LazyRow(_source,rowid,_knownColumnIndex,value);
    }

    private RowSource _source = null;
    private IntListIterator _rowIdIter = null;
    private ListIterator _valueIter = null;
    private Row _currentRow = null;
    private int _currentIndex = -1;
    private int _knownColumnIndex = -1;
}