mavibot/src/main/java/org/apache/directory/mavibot/btree/EmptyValueCursor.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 *
 */
package org.apache.directory.mavibot.btree;


import java.io.IOException;

import org.apache.directory.mavibot.btree.exception.EndOfFileExceededException;


/**
 * A Cursor which is used when we have no value to return
 * <p>
 *
 * @param <K> The type for the Key
 * @param <V> The type for the stored value
 *
 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
 */
public class EmptyValueCursor<V> implements ValueCursor<V>
{
    private long revision;
    private long creationDate;

    /**
     * Creates a new instance of Cursor, starting on a page at a given position.
     *
     * @param transaction The transaction this operation is protected by
     * @param stack The stack of parent's from root to this page
     */
    public EmptyValueCursor( long revision )
    {
        super();

        this.revision = revision;
        creationDate = System.currentTimeMillis();
    }


    /**
     * Change the position in the current cursor to set it after the last key
     */
    public void afterLast() throws IOException
    {
    }


    /**
     * Change the position in the current cursor before the first key
     */
    public void beforeFirst() throws IOException
    {
    }


    /**
     * Tells if the cursor can return a next element
     *
     * @return true if there are some more elements
     * @throws IOException
     * @throws EndOfFileExceededException
     */
    public boolean hasNext() throws EndOfFileExceededException, IOException
    {
        return false;
    }


    /**
     * Tells if the cursor can return a next key
     *
     * @return true if there are some more keys
     * @throws IOException
     * @throws EndOfFileExceededException
     */
    public boolean hasNextKey() throws EndOfFileExceededException, IOException
    {
        return false;
    }


    /**
     * Tells if the cursor can return a previous element
     *
     * @return true if there are some more elements
     * @throws IOException
     * @throws EndOfFileExceededException
     */
    public boolean hasPrev() throws EndOfFileExceededException, IOException
    {
        return false;
    }


    /**
     * Tells if the cursor can return a previous key
     *
     * @return true if there are some more keys
     * @throws IOException
     * @throws EndOfFileExceededException
     */
    public boolean hasPrevKey() throws EndOfFileExceededException, IOException
    {
        return false;
    }


    /**
     * {@inheritDoc}
     */
    @Override
    public V prev() throws EndOfFileExceededException, IOException
    {
        return null;
    }


    /**
     * {@inheritDoc}
     */
    @Override
    public V next() throws EndOfFileExceededException, IOException
    {
        return null;
    }


    /**
     * {@inheritDoc}
     */
    public void close()
    {
    }


    /**
     * Get the creation date
     * @return The creation date for this cursor
     */
    public long getCreationDate()
    {
        return creationDate;
    }


    /**
     * Get the current revision
     *
     * @return The revision this cursor is based on
     */
    public long getRevision()
    {
        return revision;
    }


    /**
     * {@inheritDoc}
     */
    @Override
    public int size()
    {
        return 0;
    }


    public String toString()
    {
        return "EmptyValueCursor";
    }
}