mavibot-partition/src/main/java/org/apache/directory/server/core/partition/impl/btree/mavibot/ValueTreeCursor.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.server.core.partition.impl.btree.mavibot;

import java.io.IOException;

import org.apache.directory.api.ldap.model.cursor.AbstractCursor;
import org.apache.directory.api.ldap.model.cursor.CursorException;
import org.apache.directory.api.ldap.model.exception.LdapException;
import org.apache.directory.server.i18n.I18n;
import org.apache.mavibot.btree.BTree;

/**
 * TODO ValueTreeCursor.
 *
 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
 */
public class ValueTreeCursor<V> extends AbstractCursor<V>
{

    private org.apache.mavibot.btree.Cursor<V, V> wrapped;
    
    private V available;

    // marker to detect the availability (cause Mavibot supports null values also)
    private V NOT_AVAILABLE = ( V ) new Object();
    
    public ValueTreeCursor( BTree<V,V> dupsTree )
    {
        try
        {
            this.wrapped = dupsTree.browse();
        }
        catch( IOException e )
        {
            throw new RuntimeException( e );
        }
    }
    
    @Override
    public boolean available()
    {
        return ( available != NOT_AVAILABLE );
    }

    @Override
    public void before( V element ) throws LdapException, CursorException, IOException
    {
        throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
    }

    @Override
    public void after( V element ) throws LdapException, CursorException, IOException
    {
        throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );        
    }

    @Override
    public void beforeFirst() throws LdapException, CursorException, IOException
    {
    }

    @Override
    public void afterLast() throws LdapException, CursorException, IOException
    {
        throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );        
    }

    @Override
    public boolean first() throws LdapException, CursorException, IOException
    {
        throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
    }

    @Override
    public boolean last() throws LdapException, CursorException, IOException
    {
        throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
    }

    @Override
    public boolean previous() throws LdapException, CursorException, IOException
    {
        if( wrapped.hasPrev() )
        {
            available = wrapped.prev().getKey();
            return true;
        }
        else
        {
            available = NOT_AVAILABLE;
            return false;
        }
    }

    @Override
    public boolean next() throws LdapException, CursorException, IOException
    {
        if( wrapped.hasNext() )
        {
            available = wrapped.next().getKey();
            return true;
        }
        else
        {
            available = NOT_AVAILABLE;
            return false;
        }
    }

    @Override
    public V get() throws CursorException, IOException
    {
        return available;
    }

}