    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 *  Unless required by applicable law or agreed to in writing, software
    012 *  distributed under the License is distributed on an "AS IS" BASIS,
    013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 *  See the License for the specific language governing permissions and
    015 *  limitations under the License.
    016 */
    017package org.apache.bcel.verifier.structurals;
    018
    019/**
    020 * This class represents a JVM execution frame; that means, a local variable array and an operand stack.
    021 */
    022
    023public class Frame {
    024
    025    /**
    026     * For instance initialization methods, it is important to remember which instance it is that is not initialized yet. It
    027     * will be initialized invoking another constructor later. NULL means the instance already *is* initialized.
    028     *
    029     * @deprecated Use the getter/setter to access the field as it may be made private in a later release
    030     */
    031    @Deprecated
    032    protected static UninitializedObjectType _this;
    033
    034    /**
    035     * @return the _this
    036     * @since 6.0
    037     */
    038    public static UninitializedObjectType getThis() {
    039        return _this;
    040    }
    041
    042    /**
    043     * @param _this the _this to set
    044     * @since 6.0
    045     */
    046    public static void setThis(final UninitializedObjectType _this) {
    047        Frame._this = _this;
    048    }
    049
    050    /**
    051     */
    052    private final LocalVariables locals;
    053
    054    /**
    055     */
    056    private final OperandStack stack;
    057
    058    /**
    059     */
    060    public Frame(final int maxLocals, final int maxStack) {
    061        locals = new LocalVariables(maxLocals);
    062        stack = new OperandStack(maxStack);
    063    }
    064
    065    /**
    066     */
    067    public Frame(final LocalVariables locals, final OperandStack stack) {
    068        this.locals = locals;
    069        this.stack = stack;
    070    }
    071
    072    /**
    073     */
    074    @Override
    075    protected Object clone() {
    076        return new Frame(locals.getClone(), stack.getClone());
    077    }
    078
    079    /**
    080     */
    081    @Override
    082    public boolean equals(final Object o) {
    083        if (!(o instanceof Frame)) {
    084            return false; // implies "null" is non-equal.
    085        }
    086        final Frame f = (Frame) o;
    087        return this.stack.equals(f.stack) && this.locals.equals(f.locals);
    088    }
    089
    090    /**
    091     */
    092    public Frame getClone() {
    093        return (Frame) clone();
    094    }
    095
    096    /**
    097     */
    098    public LocalVariables getLocals() {
    099        return locals;
    100    }
    101
    102    /**
    103     */
    104    public OperandStack getStack() {
    105        return stack;
    106    }
    107
    108    /**
    109     * @return a hash code value for the object.
    110     */
    111    @Override
    112    public int hashCode() {
    113        return stack.hashCode() ^ locals.hashCode();
    114    }
    115
    116    /**
    117     * Returns a String representation of the Frame instance.
    118     */
    119    @Override
    120    public String toString() {
    121        final StringBuilder s = new StringBuilder("Local Variables:\n");
    122        s.append(locals);
    123        s.append("OperandStack:\n");
    124        s.append(stack);
    125        return s.toString();
    126    }
    127}