/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Aug 19, 2010
*/
package com.bigdata.striterator;
import com.bigdata.bop.IElement;
import com.bigdata.bop.IPredicate;
import com.bigdata.bop.IVariableOrConstant;
import com.bigdata.btree.DefaultTupleSerializer;
import com.bigdata.btree.ITupleSerializer;
import com.bigdata.btree.keys.IKeyBuilder;
import com.bigdata.btree.keys.SuccessorUtil;
/**
* Abstract base class provides default behavior for generating keys for a given
* index order.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
*/
abstract public class AbstractKeyOrder<E> implements IKeyOrder<E> {
/**
* {@inheritDoc}
*
* FIXME This needs to be reconciled with
* {@link ITupleSerializer#serializeKey(Object)}. For example, this
* does not play well with the {@link DefaultTupleSerializer}.
*/
@Override
public byte[] getKey(final IKeyBuilder keyBuilder, final E element) {
keyBuilder.reset();
final int keyArity = getKeyArity(); // use the key's "arity".
for (int i = 0; i < keyArity; i++) {
/*
* Note: If you need to override the default IKeyBuilder behavior do
* it in the invoked method.
*/
appendKeyComponent(keyBuilder, i, ((IElement) element)
.get(getKeyOrder(i)));
}
return keyBuilder.getKey();
}
@Override
public byte[] getFromKey(final IKeyBuilder keyBuilder,
final IPredicate<E> predicate) {
keyBuilder.reset();
final int keyArity = getKeyArity(); // use the key's "arity".
boolean noneBound = true;
for (int i = 0; i < keyArity; i++) {
final IVariableOrConstant<?> term = predicate.get(getKeyOrder(i));
// Note: term MAY be null for the context position.
if (term == null || term.isVar())
break;
/*
* Note: If you need to override the default IKeyBuilder behavior do
* it in the invoked method.
*/
appendKeyComponent(keyBuilder, i, term.get());
noneBound = false;
}
final byte[] key = noneBound ? null : keyBuilder.getKey();
return key;
}
@Override
public byte[] getToKey(final IKeyBuilder keyBuilder,
final IPredicate<E> predicate) {
keyBuilder.reset();
final int keyArity = getKeyArity(); // use the key's "arity".
boolean noneBound = true;
for (int i = 0; i < keyArity; i++) {
final IVariableOrConstant<?> term = predicate.get(getKeyOrder(i));
// Note: term MAY be null for the context position.
if (term == null || term.isVar())
break;
/*
* Note: If you need to override the default IKeyBuilder behavior do
* it in the invoked method.
*/
appendKeyComponent(keyBuilder, i, term.get());
noneBound = false;
}
final byte[] key = noneBound ? null : keyBuilder.getKey();
return key == null ? null : SuccessorUtil.successor(key);
}
/**
* Encodes an value into the key. This implementation uses the default
* behavior of {@link IKeyBuilder}. If you need to specialize how a value
* gets encoded into the key then you can override this method.
*/
protected void appendKeyComponent(final IKeyBuilder keyBuilder,
final int index, final Object keyComponent) {
keyBuilder.append(keyComponent);
}
}