/*
* 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.xdbm.search.impl;
import org.apache.directory.server.xdbm.Index;
import org.apache.directory.server.xdbm.IndexEntry;
import org.apache.directory.server.xdbm.Store;
import org.apache.directory.server.xdbm.AbstractIndexCursor;
import org.apache.directory.server.xdbm.IndexCursor;
import org.apache.directory.server.core.entry.ServerEntry;
import org.apache.directory.server.i18n.I18n;
import org.apache.directory.shared.ldap.cursor.InvalidCursorPositionException;
import org.apache.directory.shared.ldap.entry.Value;
/**
* A Cursor over entry candidates matching an approximate assertion filter.
* This Cursor really is a copy of EqualityCursor for now but later on
* approximate matching can be implemented and this can change. It operates
* in two modes. The first is when an index exists for the attribute the
* approximate assertion is built on. The second is when the user index for
* the assertion attribute does not exist. Different Cursors are used in each
* of these cases where the other remains null.
*
* @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
* @version $$Rev$$
*/
public class ApproximateCursor<V, ID> extends AbstractIndexCursor<V, ServerEntry, ID>
{
private static final String UNSUPPORTED_MSG = "ApproximateCursors only support positioning by element when a user index exists on the asserted attribute.";
/** An approximate evaluator for candidates */
private final ApproximateEvaluator<V, ID> approximateEvaluator;
/** Cursor over attribute entry matching filter: set when index present */
private final IndexCursor<V, ServerEntry, ID> userIdxCursor;
/** NDN Cursor on all entries in (set when no index on user attribute) */
private final IndexCursor<String, ServerEntry, ID> ndnIdxCursor;
/** used only when ndnIdxCursor is used (no index on attribute) */
private boolean available = false;
@SuppressWarnings("unchecked")
public ApproximateCursor( Store<ServerEntry, ID> db, ApproximateEvaluator<V, ID> approximateEvaluator ) throws Exception
{
this.approximateEvaluator = approximateEvaluator;
String attribute = approximateEvaluator.getExpression().getAttribute();
Value<V> value = approximateEvaluator.getExpression().getValue();
if ( db.hasIndexOn( attribute ) )
{
Index<V, ServerEntry, ID> index = ( Index<V, ServerEntry, ID> ) db.getIndex( attribute );
userIdxCursor = index.forwardCursor( value.get() );
ndnIdxCursor = null;
}
else
{
ndnIdxCursor = db.getNdnIndex().forwardCursor();
userIdxCursor = null;
}
}
public boolean available()
{
if ( userIdxCursor != null )
{
return userIdxCursor.available();
}
return available;
}
public void beforeValue( ID id, V value ) throws Exception
{
checkNotClosed( "beforeValue()" );
if ( userIdxCursor != null )
{
userIdxCursor.beforeValue( id, value );
}
else
{
throw new UnsupportedOperationException( UNSUPPORTED_MSG );
}
}
public void afterValue( ID id, V value ) throws Exception
{
checkNotClosed( "afterValue()" );
if ( userIdxCursor != null )
{
userIdxCursor.afterValue( id, value );
}
else
{
throw new UnsupportedOperationException( UNSUPPORTED_MSG );
}
}
public void before( IndexEntry<V, ServerEntry, ID> element ) throws Exception
{
checkNotClosed( "before()" );
if ( userIdxCursor != null )
{
userIdxCursor.before( element );
}
else
{
throw new UnsupportedOperationException( UNSUPPORTED_MSG );
}
}
public void after( IndexEntry<V, ServerEntry, ID> element ) throws Exception
{
checkNotClosed( "after()" );
if ( userIdxCursor != null )
{
userIdxCursor.after( element );
}
else
{
throw new UnsupportedOperationException( UNSUPPORTED_MSG );
}
}
public void beforeFirst() throws Exception
{
checkNotClosed( "beforeFirst()" );
if ( userIdxCursor != null )
{
userIdxCursor.beforeFirst();
}
else
{
ndnIdxCursor.beforeFirst();
available = false;
}
}
public void afterLast() throws Exception
{
checkNotClosed( "afterLast()" );
if ( userIdxCursor != null )
{
userIdxCursor.afterLast();
}
else
{
ndnIdxCursor.afterLast();
available = false;
}
}
public boolean first() throws Exception
{
beforeFirst();
return next();
}
public boolean last() throws Exception
{
afterLast();
return previous();
}
public boolean previous() throws Exception
{
if ( userIdxCursor != null )
{
return userIdxCursor.previous();
}
while ( ndnIdxCursor.previous() )
{
checkNotClosed( "previous()" );
IndexEntry<?, ServerEntry, ID> candidate = ndnIdxCursor.get();
if ( approximateEvaluator.evaluate( candidate ) )
{
return available = true;
}
}
return available = false;
}
public boolean next() throws Exception
{
if ( userIdxCursor != null )
{
return userIdxCursor.next();
}
while ( ndnIdxCursor.next() )
{
checkNotClosed( "next()" );
IndexEntry<?, ServerEntry, ID> candidate = ndnIdxCursor.get();
if ( approximateEvaluator.evaluate( candidate ) )
{
return available = true;
}
}
return available = false;
}
@SuppressWarnings("unchecked")
public IndexEntry<V, ServerEntry, ID> get() throws Exception
{
checkNotClosed( "get()" );
if ( userIdxCursor != null )
{
return userIdxCursor.get();
}
if ( available )
{
return ( IndexEntry<V, ServerEntry, ID> ) ndnIdxCursor.get();
}
throw new InvalidCursorPositionException( I18n.err( I18n.ERR_708 ) );
}
public boolean isElementReused()
{
if ( userIdxCursor != null )
{
return userIdxCursor.isElementReused();
}
return ndnIdxCursor.isElementReused();
}
public void close() throws Exception
{
super.close();
if ( userIdxCursor != null )
{
userIdxCursor.close();
}
else
{
ndnIdxCursor.close();
}
}
}