/*
* 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;
/**
* Core properties of choice frames used use to represent the OR state of
* the backtracking search. Specific variants of this need to preserve additional
* choice state.
* <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 GenericChoiceFrame extends FrameObject {
/** The environment frame describing the state of the AND tree at this choice point */
EnvironmentFrame envFrame;
/** The top of the trail stack at the time of the call */
int trailIndex;
/** The continuation program counter offet in the parent clause's byte code */
int cpc;
/** The continuation argument counter offset in the parent clause's arg stream */
int cac;
/**
* Initialize a choice point to preserve the current context of the given intepreter
* and then call the given set of predicates.
* @param interpreter the LPInterpreter whose state is to be preserved
*/
public void init(LPInterpreter interpreter) {
envFrame = interpreter.envFrame;
trailIndex = interpreter.trail.size();
}
/**
* Set the continuation point for this frame.
*/
public void setContinuation(int pc, int ac) {
cpc = pc;
cac = ac;
}
}