/*
* 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.ArrayList ;
import java.util.Iterator ;
import java.util.List ;
import java.util.NoSuchElementException ;
import org.apache.jena.atlas.io.IndentedWriter ;
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 com.hp.hpl.jena.sparql.serializer.SerializationContext ;
import com.hp.hpl.jena.sparql.util.Utils ;
/**
* A query iterator that joins two or more iterators into a single iterator. */
public class QueryIterConcat extends QueryIter
{
boolean initialized = false ;
List<QueryIterator> iteratorList = new ArrayList<QueryIterator>() ;
Iterator<QueryIterator> iterator ;
QueryIterator currentQIter = null ;
Binding binding ;
boolean doneFirst = false ;
public QueryIterConcat(ExecutionContext context)
{
super(context) ;
}
private void init()
{
if ( ! initialized )
{
currentQIter = null ;
if ( iterator == null )
iterator = iteratorList.listIterator() ;
if ( iterator.hasNext() )
currentQIter = iterator.next() ;
initialized = true ;
}
}
public void add(QueryIterator qIter)
{
if ( qIter != null )
iteratorList.add(qIter) ;
}
@Override
protected boolean hasNextBinding()
{
if ( isFinished() )
return false ;
init() ;
if ( currentQIter == null )
return false ;
while ( ! currentQIter.hasNext() )
{
// End sub iterator
//currentQIter.close() ;
currentQIter = null ;
if ( iterator.hasNext() )
currentQIter = iterator.next() ;
if ( currentQIter == null )
{
// No more.
//close() ;
return false ;
}
}
return true ;
}
@Override
protected Binding moveToNextBinding()
{
if ( ! hasNextBinding() )
throw new NoSuchElementException(Utils.className(this)) ;
if ( currentQIter == null )
throw new NoSuchElementException(Utils.className(this)) ;
Binding binding = currentQIter.nextBinding() ;
return binding ;
}
@Override
protected void closeIterator()
{
for ( Iterator<QueryIterator> iter = iteratorList.iterator() ; iter.hasNext() ; )
{
QueryIterator qIter = iter.next() ;
performClose(qIter) ;
}
}
@Override
protected void requestCancel()
{
for ( Iterator<QueryIterator> iter = iteratorList.iterator() ; iter.hasNext() ; )
{
QueryIterator qIter = iter.next() ;
performRequestCancel(qIter) ;
}
}
@Override
public void output(IndentedWriter out, SerializationContext sCxt)
{
out.println(Utils.className(this)) ;
out.incIndent() ;
for ( Iterator<QueryIterator> iter = iteratorList.iterator() ; iter.hasNext() ; )
{
QueryIterator qIter = iter.next() ;
qIter.output(out, sCxt) ;
}
out.decIndent() ;
out.ensureStartOfLine() ;
}
}