/*
* 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.op;
import org.apache.jena.atlas.io.IndentedWriter ;
import com.hp.hpl.jena.sparql.ARQNotImplemented ;
import com.hp.hpl.jena.sparql.algebra.Op ;
import com.hp.hpl.jena.sparql.algebra.OpVisitor ;
import com.hp.hpl.jena.sparql.algebra.Transform ;
import com.hp.hpl.jena.sparql.engine.ExecutionContext ;
import com.hp.hpl.jena.sparql.engine.QueryIterator ;
import com.hp.hpl.jena.sparql.serializer.SerializationContext ;
import com.hp.hpl.jena.sparql.sse.Tags ;
import com.hp.hpl.jena.sparql.sse.writers.WriterLib ;
/** Marker for extension points
* Execution will be per-engine specific */
public abstract class OpExt extends OpBase
{
protected final String tag ;
public OpExt(String name) { tag = name ; }
/** Return an op that will used by query processing algorithms such as
* optimization. This method returns a non-extension Op expression that
* is the equivalent SPARQL expression. For example, this is the Op replaced
* by this extension node.
*/
public abstract Op effectiveOp() ;
/** Evaluate the op, given a stream of bindings as input
* Throw UnsupportedOperationException if this OpExt is not executeable.
*/
public abstract QueryIterator eval(QueryIterator input, ExecutionContext execCxt) ;
@Override
public final String getName() { return tag ; }
@Override
public final void visit(OpVisitor opVisitor)
{ opVisitor.visit(this) ; }
@Override
public void output(IndentedWriter out, SerializationContext sCxt)
{
int line = out.getRow() ;
if ( false )
{
// Write in (ext NAME ...) form.
WriterLib.start(out, Tags.tagExt, WriterLib.NoNL) ;
out.print(getName()) ;
out.print(" ") ;
outputArgs(out, sCxt) ;
WriterLib.finish(out, Tags.tagExt) ;
}
else
{
// Write in (NAME ...) form.
WriterLib.start(out, tag, WriterLib.NoNL) ;
outputArgs(out, sCxt) ;
WriterLib.finish(out, tag) ;
}
if ( line != out.getRow() )
out.ensureStartOfLine() ;
}
public Op apply(Transform transform) { throw new ARQNotImplemented("OpExt.appy(Transform)") ; }
// /** Return the sub tag - must match the builder */
// public abstract String getSubTag() ;
/** Output the arguments in legal SSE format. Multiple items, whitespace separated */
public abstract void outputArgs(IndentedWriter out, SerializationContext sCxt) ;
}