/*
* 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.jdbm;
import org.apache.directory.server.i18n.I18n;
import org.apache.directory.server.xdbm.Tuple;
import org.apache.directory.server.xdbm.AbstractTupleCursor;
import org.apache.directory.shared.ldap.cursor.InvalidCursorPositionException;
import java.util.Comparator;
import jdbm.helper.TupleBrowser;
import jdbm.btree.BTree;
/**
* Cursor over a set of values for the same key which are store in another
* BTree. This Cursor is limited to the same key and it's tuples will always
* return the same key.
*
* @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
* @version $Rev$, $Date$
*/
public class KeyTupleBTreeCursor<K,V> extends AbstractTupleCursor<K,V>
{
private final Comparator<V> comparator;
private final BTree btree;
private final K key;
private jdbm.helper.Tuple valueTuple = new jdbm.helper.Tuple();
private Tuple<K,V> returnedTuple = new Tuple<K,V>();
private TupleBrowser browser;
private boolean valueAvailable;
/**
* Creates a Cursor over the tuples of a JDBM BTree.
*
* @param btree the JDBM BTree to build a Cursor over
* @param key the constant key for which values are returned
* @param comparator the Comparator used to determine <b>key</b> ordering
* @throws Exception of there are problems accessing the BTree
*/
public KeyTupleBTreeCursor( BTree btree, K key, Comparator<V> comparator ) throws Exception
{
this.key = key;
this.btree = btree;
this.comparator = comparator;
this.browser = btree.browse();
}
private void clearValue()
{
returnedTuple.setKey( key );
returnedTuple.setValue( null );
valueAvailable = false;
}
public boolean available()
{
return valueAvailable;
}
public void beforeKey( K key ) throws Exception
{
throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
}
public void afterKey( K key ) throws Exception
{
throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
}
public void beforeValue( K key, V value ) throws Exception
{
checkNotClosed( "beforeValue()" );
if ( key != null && ! key.equals( this.key ) )
{
throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
}
browser = btree.browse( value );
clearValue();
}
@SuppressWarnings("unchecked")
public void afterValue( K key, V value ) throws Exception
{
if ( key != null && ! key.equals( this.key ) )
{
throw new UnsupportedOperationException( I18n.err( I18n.ERR_446 ) );
}
browser = btree.browse( value );
/*
* While the next value is less than or equal to the element keep
* advancing forward to the next item. If we cannot advance any
* further then stop and return. If we find a value greater than
* the element then we stop, backup, and return so subsequent calls
* to getNext() will return a value greater than the element.
*/
while ( browser.getNext( valueTuple ) )
{
checkNotClosed( "afterValue" );
V next = ( V ) valueTuple.getKey();
int nextCompared = comparator.compare( next, value );
if ( nextCompared <= 0 )
{
// just continue
}
else if ( nextCompared > 0 )
{
/*
* If we just have values greater than the element argument
* then we are before the first element and cannot backup, and
* the call below to getPrevious() will fail. In this special
* case we just reset the Cursor's browser and return.
*/
if ( browser.getPrevious( valueTuple ) )
{
}
else
{
browser = btree.browse( this.key );
}
clearValue();
return;
}
}
clearValue();
}
/**
* Positions this Cursor over the same keys before the value of the
* supplied valueTuple. The supplied element Tuple's key is not considered at
* all.
*
* @param element the valueTuple who's value is used to position this Cursor
* @throws Exception if there are failures to position the Cursor
*/
public void before( Tuple<K,V> element ) throws Exception
{
checkNotClosed( "before()" );
browser = btree.browse( element.getValue() );
clearValue();
}
public void after( Tuple<K,V> element ) throws Exception
{
afterValue( key, element.getValue() );
}
public void beforeFirst() throws Exception
{
checkNotClosed( "beforeFirst()" );
browser = btree.browse();
clearValue();
}
public void afterLast() throws Exception
{
checkNotClosed( "afterLast()" );
browser = btree.browse( null );
}
public boolean first() throws Exception
{
beforeFirst();
return next();
}
public boolean last() throws Exception
{
afterLast();
return previous();
}
@SuppressWarnings("unchecked")
public boolean previous() throws Exception
{
checkNotClosed( "previous()" );
if ( browser.getPrevious( valueTuple ) )
{
// work around to fix direction change problem with jdbm browser
if ( returnedTuple.getValue() != null &&
comparator.compare( ( V ) valueTuple.getKey(), returnedTuple.getValue() ) == 0 )
{
browser.getPrevious( valueTuple ) ;
}
returnedTuple.setKey( key );
returnedTuple.setValue( ( V ) valueTuple.getKey() );
return valueAvailable = true;
}
else
{
clearValue();
return false;
}
}
@SuppressWarnings("unchecked")
public boolean next() throws Exception
{
checkNotClosed( "next()" );
if ( browser.getNext( valueTuple ) )
{
// work around to fix direction change problem with jdbm browser
if ( returnedTuple.getValue() != null &&
comparator.compare( ( V ) valueTuple.getKey(), returnedTuple.getValue() ) == 0 )
{
browser.getNext( valueTuple ) ;
}
returnedTuple.setKey( key );
returnedTuple.setValue( ( V ) valueTuple.getKey() );
return valueAvailable = true;
}
else
{
clearValue();
return false;
}
}
public Tuple<K,V> get() throws Exception
{
checkNotClosed( "get()" );
if ( valueAvailable )
{
return returnedTuple;
}
throw new InvalidCursorPositionException();
}
public boolean isElementReused()
{
return true;
}
}