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Lightweight analysis tool for detecting mutability in Java classes.

There is a newer version: 0.10.6

/*
 * Mutability Detector
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 *
 * Further licensing information for this project can be found in 
 * 		license/LICENSE.txt
 */

package org.mutabilitydetector.checkers;

import static java.util.Collections.unmodifiableList;

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

public class VarStack {

	private List indices = new ArrayList();
	private List snapshots = new ArrayList();
	private Iterator snapshotsIterator = snapshots.iterator();
	

	public void visitVarInsn(int opcode, int var) {
		indices.add(var);
	}

	public void takeSnapshotOfVarsAtPutfield() {
		snapshots.add(new VarStackSnapshot(indices));
		snapshotsIterator = snapshots.iterator();
	}
	
	public VarStackSnapshot next() {
		return snapshotsIterator.next();
	}

	public static class VarStackSnapshot {
		
		private final List indices;

		public VarStackSnapshot(List indices) {
			this.indices = unmodifiableList(new ArrayList(indices));
		}
		
		public boolean thisObjectWasAddedToStack() {
			// the "this" reference is at position 0 of the local variable table
			return indices.contains(0);
		}
		
		public int indexOfOwningObject() {
			int stackSpaceToLookBack = 1;
			return indices.get((indices.size() -1) - stackSpaceToLookBack);
		}

	}

}