Package com.hp.hpl.jena.sparql.algebra.table

Source Code of com.hp.hpl.jena.sparql.algebra.table.TableUnit

/*
* 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.algebra.table;

import java.util.ArrayList ;
import java.util.Iterator ;
import java.util.List ;

import org.apache.jena.atlas.iterator.Iter ;

import com.hp.hpl.jena.sparql.algebra.Table ;
import com.hp.hpl.jena.sparql.core.Var ;
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.engine.binding.BindingFactory ;
import com.hp.hpl.jena.sparql.engine.iterator.QueryIterSingleton ;
import com.hp.hpl.jena.sparql.expr.ExprList ;

public class TableUnit extends TableBase
{
    static public boolean isTableUnit(Table table)
    { return (table instanceof TableUnit) ; }
   
    public TableUnit() {}
   
    @Override
    public Iterator<Binding> rows() {
        Binding binding = BindingFactory.binding() ;
        return Iter.singleton(binding) ;
    }
   
    @Override
    public QueryIterator iterator(ExecutionContext execCxt)
    {
        // BindingRoot?
        Binding binding = BindingFactory.binding() ;
        return QueryIterSingleton.create(binding, execCxt) ;
    }

    @Override
    public QueryIterator matchRightLeft(Binding bindingLeft, boolean includeOnNoMatch,
                                        ExprList conditions,
                                        ExecutionContext execCxt)
    {
        // We are one row of no entries - joins with anything
        return QueryIterSingleton.create(bindingLeft, execCxt) ;
    }

    @Override
    public void closeTable()    { }

    @Override
    public int size()           { return 1 ; }
    @Override
    public boolean isEmpty()    { return false ; }

    @Override
    public List<String> getVarNames()   { return new ArrayList<String>() ; }

    @Override
    public List<Var> getVars()       { return new ArrayList<Var>() ; }
   
    @Override
    public String toString()    { return "TableUnit" ; }
}
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