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IteratorBatcherStep.java
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IteratorBatcherStep.java
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/*
* Copyright (c) 2002-2017 "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.unsafe.impl.batchimport.staging;
import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Iterator;
import java.util.function.Predicate;
import org.neo4j.unsafe.impl.batchimport.Configuration;
/**
* Takes an Iterator and chops it up into array batches downstream.
*/
public abstract class IteratorBatcherStep<T> extends PullingProducerStep
{
private final Iterator<T> data;
private final Class<T> itemClass;
private final Predicate<T> filter;
protected long cursor;
private T[] batch;
private int batchCursor;
private int skipped;
public IteratorBatcherStep( StageControl control, Configuration config, Iterator<T> data, Class<T> itemClass,
Predicate<T> filter )
{
super( control, config );
this.data = data;
this.itemClass = itemClass;
this.filter = filter;
newBatch();
}
@SuppressWarnings( "unchecked" )
private void newBatch()
{
batchCursor = 0;
batch = (T[]) Array.newInstance( itemClass, batchSize );
}
@Override
protected Object nextBatchOrNull( long ticket, int batchSize )
{
while ( data.hasNext() )
{
T candidate = data.next();
if ( filter.test( candidate ) )
{
batch[batchCursor++] = candidate;
cursor++;
if ( batchCursor == batchSize )
{
T[] result = batch;
newBatch();
return result;
}
}
else
{
if ( ++skipped == batchSize )
{
skipped = 0;
return Array.newInstance( itemClass, 0 );
}
}
}
if ( batchCursor == 0 )
{
return null; // marks the end
}
try
{
return batchCursor == batchSize ? batch : Arrays.copyOf( batch, batchCursor );
}
finally
{
batchCursor = 0;
}
}
}