/*
* 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.binding ;
import java.util.ArrayList ;
import java.util.Iterator ;
import java.util.List ;
import org.apache.jena.graph.Node ;
import org.apache.jena.sparql.core.Var ;
/** Common framework for projection;
* the projection policy is provided by
* abstract method {@link #accept(Var)}
*/
public abstract class BindingProjectBase extends BindingBase {
private List<Var> actualVars = null ;
private final Binding binding ;
public BindingProjectBase(Binding bind) {
super(null) ;
binding = bind ;
}
protected abstract boolean accept(Var var) ;
@Override
protected boolean contains1(Var var) {
return accept(var) && binding.contains(var) ;
}
@Override
protected Node get1(Var var) {
if ( !accept(var) )
return null ;
return binding.get(var) ;
}
@Override
protected Iterator<Var> vars1() {
return actualVars().iterator() ;
}
private List<Var> actualVars() {
if ( actualVars == null ) {
actualVars = new ArrayList<>() ;
Iterator<Var> iter = binding.vars() ;
for ( ; iter.hasNext() ; ) {
Var v = iter.next() ;
if ( accept(v) )
actualVars.add(v) ;
}
}
return actualVars ;
}
@Override
protected int size1() {
return actualVars().size() ;
}
// NB is the projection and the binding don't overlap it is also empty.
@Override
protected boolean isEmpty1() {
if ( binding.isEmpty() )
return true ;
if ( size1() == 0 )
return true ;
return false ;
}
}