/*
* 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 org.apache.jena.sparql.engine.iterator ;
import java.util.NoSuchElementException ;
import org.apache.jena.atlas.lib.Lib ;
import org.apache.jena.sparql.ARQInternalErrorException ;
import org.apache.jena.sparql.engine.ExecutionContext ;
import org.apache.jena.sparql.engine.QueryIterator ;
import org.apache.jena.sparql.engine.binding.Binding ;
/**
* An iterator that applies a condition. The condition may return a different
* binding.
*/
public abstract class QueryIterProcessBinding extends QueryIter1 {
/** Process the binding - return null for "not accept".
* Subclasses may return a different Binding to the argument and
* the result is the returned Binding.
*/
abstract public Binding accept(Binding binding) ;
private Binding nextBinding ;
public QueryIterProcessBinding(QueryIterator qIter, ExecutionContext context) {
super(qIter, context) ;
nextBinding = null ;
}
/**
* Are there any more acceptable objects.
*
* @return true if there is another acceptable object.
*/
@Override
protected boolean hasNextBinding() {
// Needs to be idempotent.?
if ( isFinished() )
return false ;
if ( nextBinding != null )
return true ;
// Null iterator.
if ( getInput() == null )
throw new ARQInternalErrorException(Lib.className(this) + ": Null iterator") ;
while (getInput().hasNext()) {
// Skip forward until a binding to return is found.
Binding input = getInput().nextBinding() ;
Binding output = accept(input) ;
if ( output != null ) {
nextBinding = output ;
return true ;
}
}
nextBinding = null ;
return false ;
}
/**
* The next acceptable object in the iterator.
*
* @return The next acceptable object.
*/
@Override
public Binding moveToNextBinding() {
if ( hasNext() ) {
Binding r = nextBinding ;
nextBinding = null ;
return r ;
}
throw new NoSuchElementException() ;
}
@Override
protected void closeSubIterator() {}
@Override
protected void requestSubCancel() {}
}