/*
* 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.reasoner.rulesys.impl;
import org.apache.jena.graph.* ;
import org.apache.jena.util.iterator.ExtendedIterator ;
/**
* Frame on the choice point stack used to represent the state of a direct
* graph triple match.
* <p>
* This is used in the inner loop of the interpreter and so is a pure data structure
* not an abstract data type and assumes privileged access to the interpreter state.
* </p>
*/
public class TripleMatchFrame extends GenericTripleMatchFrame {
/** An iterator over triples matching a goal */
ExtendedIterator<Triple> matchIterator;
/**
* Constructor.
* Initialize the triple match to preserve the current context of the given
* LPInterpreter and search for the match defined by the current argument registers
* @param interpreter the interpreter instance whose env, trail and arg values are to be preserved
*/
public TripleMatchFrame(LPInterpreter interpreter) {
init(interpreter);
}
/**
* Find the next result triple and bind the result vars appropriately.
* @param interpreter the calling interpreter whose trail should be used
* @return false if there are no more matches in the iterator.
*/
public boolean nextMatch(LPInterpreter interpreter) {
while (matchIterator.hasNext()) {
if (bindResult(matchIterator.next(), interpreter)) {
return true;
}
}
return false;
}
/**
* Initialize the triple match to preserve the current context of the given
* LPInterpreter and search for the match defined by the current argument registers
* @param interpreter the interpreter instance whose env, trail and arg values are to be preserved
*/
@Override public void init(LPInterpreter interpreter) {
super.init(interpreter);
this.matchIterator = interpreter.getEngine().getInfGraph().findDataMatches(goal);
}
/**
* Override close method to reclaim the iterator.
*/
@Override public void close() {
if (matchIterator != null) matchIterator.close();
super.close();
}
}