/*
* 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 com.hp.hpl.jena.sparql.engine.iterator;
import java.util.NoSuchElementException ;
import com.hp.hpl.jena.sparql.engine.ExecutionContext ;
import com.hp.hpl.jena.sparql.engine.QueryIterator ;
import com.hp.hpl.jena.sparql.engine.binding.Binding ;
import org.apache.jena.atlas.logging.Log ;
import com.hp.hpl.jena.sparql.util.Utils ;
/** Repeatedly execute the subclass operation for each Binding in the input iterator. */
public abstract class QueryIterRepeatApply extends QueryIter1
{
int count = 0 ;
private QueryIterator currentStage ;
private volatile boolean cancelRequested = false; // [CANCEL] needed? super.cancelRequest?
public QueryIterRepeatApply( QueryIterator input ,
ExecutionContext context)
{
super(input, context) ;
this.currentStage = null ;
if ( input == null )
{
Log.fatal(this, "[QueryIterRepeatApply] Repeated application to null input iterator") ;
return ;
}
}
protected QueryIterator getCurrentStage()
{
return currentStage ;
}
protected abstract QueryIterator nextStage(Binding binding) ;
@Override
protected boolean hasNextBinding()
{
if ( isFinished() )
return false ;
for ( ;; )
{
if ( currentStage == null )
currentStage = makeNextStage() ;
if ( currentStage == null )
return false ;
if ( cancelRequested )
{
// This ensures we don't miss a change to cancelRequested
// In the middle of a cancel.
// XXX This repeatedly calls subcancel if the iterator is drained.
// But QueryItertaorBase turns that into a single call of requestCancel.
performRequestCancel(currentStage);
}
if ( currentStage.hasNext() )
return true ;
// finish this step
currentStage.close() ;
currentStage = null ;
// loop
}
// Unreachable
}
@Override
protected Binding moveToNextBinding()
{
if ( ! hasNextBinding() )
throw new NoSuchElementException(Utils.className(this)+".next()/finished") ;
return currentStage.nextBinding() ;
}
private QueryIterator makeNextStage()
{
count++ ;
if ( getInput() == null )
return null ;
if ( !getInput().hasNext() )
{
getInput().close() ;
return null ;
}
Binding binding = getInput().next() ;
QueryIterator iter = nextStage(binding) ;
return iter ;
}
@Override
protected void closeSubIterator()
{
if ( currentStage != null )
currentStage.close() ;
}
@Override
protected void requestSubCancel()
{
if ( currentStage != null )
currentStage.cancel() ; // [CANCEL]
cancelRequested = true;
}
}