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AbstractSelectorOrderer.java
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AbstractSelectorOrderer.java
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/*
* Copyright (c) 2002-2016 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j 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, either version 3 of the License, or
* (at your option) any later version.
*
* 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, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.graphdb.impl.traversal;
import org.neo4j.graphdb.Direction;
import org.neo4j.graphdb.traversal.BranchSelector;
import org.neo4j.graphdb.traversal.SideSelector;
import org.neo4j.graphdb.traversal.TraversalBranch;
import org.neo4j.graphdb.traversal.TraversalContext;
public abstract class AbstractSelectorOrderer<T> implements SideSelector
{
private static final BranchSelector EMPTY_SELECTOR = metadata -> null;
private final BranchSelector[] selectors;
@SuppressWarnings( "unchecked" )
private final T[] states = (T[]) new Object[2];
private int selectorIndex;
public AbstractSelectorOrderer( BranchSelector startSelector, BranchSelector endSelector )
{
selectors = new BranchSelector[] { startSelector, endSelector };
states[0] = initialState();
states[1] = initialState();
}
protected T initialState()
{
return null;
}
protected void setStateForCurrentSelector( T state )
{
states[selectorIndex] = state;
}
protected T getStateForCurrentSelector()
{
return states[selectorIndex];
}
protected TraversalBranch nextBranchFromCurrentSelector( TraversalContext metadata,
boolean switchIfExhausted )
{
return nextBranchFromSelector( metadata, selectors[selectorIndex], switchIfExhausted );
}
protected TraversalBranch nextBranchFromNextSelector( TraversalContext metadata,
boolean switchIfExhausted )
{
return nextBranchFromSelector( metadata, nextSelector(), switchIfExhausted );
}
private TraversalBranch nextBranchFromSelector( TraversalContext metadata,
BranchSelector selector, boolean switchIfExhausted )
{
TraversalBranch result = selector.next( metadata );
if ( result == null )
{
selectors[selectorIndex] = EMPTY_SELECTOR;
if ( switchIfExhausted )
{
result = nextSelector().next( metadata );
if ( result == null )
{
selectors[selectorIndex] = EMPTY_SELECTOR;
}
}
}
return result;
}
protected BranchSelector nextSelector()
{
selectorIndex = (selectorIndex+1)%2;
return selectors[selectorIndex];
}
@Override
public Direction currentSide()
{
return selectorIndex == 0 ? Direction.OUTGOING : Direction.INCOMING;
}
}