    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 *
    017 */
    018package org.apache.bcel.verifier.structurals;
    019
    020
    021import org.apache.bcel.generic.ReferenceType;
    022import org.apache.bcel.generic.Type;
    023import org.apache.bcel.verifier.exc.AssertionViolatedException;
    024import org.apache.bcel.verifier.exc.StructuralCodeConstraintException;
    025
    026/**
    027 * This class implements an array of local variables used for symbolic JVM
    028 * simulation.
    029 *
    030 * @version $Id$
    031 */
    032public class LocalVariables implements Cloneable {
    033    /** The Type[] containing the local variable slots. */
    034    private final Type[] locals;
    035
    036    /**
    037     * Creates a new LocalVariables object.
    038     */
    039    public LocalVariables(final int maxLocals) {
    040        locals = new Type[maxLocals];
    041        for (int i=0; i<maxLocals; i++) {
    042            locals[i] = Type.UNKNOWN;
    043        }
    044    }
    045
    046    /**
    047     * Returns a deep copy of this object; i.e. the clone
    048     * operates on a new local variable array.
    049     * However, the Type objects in the array are shared.
    050     */
    051    @Override
    052    public Object clone() {
    053        final LocalVariables lvs = new LocalVariables(locals.length);
    054        for (int i=0; i<locals.length; i++) {
    055            lvs.locals[i] = this.locals[i];
    056        }
    057        return lvs;
    058    }
    059
    060    /**
    061     * Returns the type of the local variable slot i.
    062     */
    063    public Type get(final int i) {
    064        return locals[i];
    065    }
    066
    067    /**
    068     * Returns a (correctly typed) clone of this object.
    069     * This is equivalent to ((LocalVariables) this.clone()).
    070     */
    071    public LocalVariables getClone() {
    072        return (LocalVariables) this.clone();
    073    }
    074
    075    /**
    076     * Returns the number of local variable slots this
    077     * LocalVariables instance has.
    078     */
    079    public int maxLocals() {
    080        return locals.length;
    081    }
    082
    083    /**
    084     * Sets a new Type for the given local variable slot.
    085     */
    086    public void set(final int i, final Type type) { // TODO could be package-protected?
    087        if (type == Type.BYTE || type == Type.SHORT || type == Type.BOOLEAN || type == Type.CHAR) {
    088            throw new AssertionViolatedException("LocalVariables do not know about '"+type+"'. Use Type.INT instead.");
    089        }
    090        locals[i] = type;
    091    }
    092
    093    /** @return a hash code value for the object.
    094     */
    095    @Override
    096    public int hashCode() { return locals.length; }
    097
    098    /*
    099     * Fulfills the general contract of Object.equals().
    100     */
    101    @Override
    102    public boolean equals(final Object o) {
    103        if (!(o instanceof LocalVariables)) {
    104            return false;
    105        }
    106        final LocalVariables lv = (LocalVariables) o;
    107        if (this.locals.length != lv.locals.length) {
    108            return false;
    109        }
    110        for (int i=0; i<this.locals.length; i++) {
    111            if (!this.locals[i].equals(lv.locals[i])) {
    112                //System.out.println(this.locals[i]+" is not "+lv.locals[i]);
    113                return false;
    114            }
    115        }
    116        return true;
    117    }
    118
    119    /**
    120     * Merges two local variables sets as described in the Java Virtual Machine Specification,
    121     * Second Edition, section 4.9.2, page 146.
    122     */
    123    public void merge(final LocalVariables lv) {
    124
    125        if (this.locals.length != lv.locals.length) {
    126            throw new AssertionViolatedException("Merging LocalVariables of different size?!? From different methods or what?!?");
    127        }
    128
    129        for (int i=0; i<locals.length; i++) {
    130            merge(lv, i);
    131        }
    132    }
    133
    134    /**
    135     * Merges a single local variable.
    136     *
    137     * @see #merge(LocalVariables)
    138     */
    139    private void merge(final LocalVariables lv, final int i) {
    140        try {
    141
    142        // We won't accept an unitialized object if we know it was initialized;
    143        // compare vmspec2, 4.9.4, last paragraph.
    144        if ( (!(locals[i] instanceof UninitializedObjectType)) && (lv.locals[i] instanceof UninitializedObjectType) ) {
    145            throw new StructuralCodeConstraintException(
    146                "Backwards branch with an uninitialized object in the local variables detected.");
    147        }
    148        // Even harder, what about _different_ uninitialized object types?!
    149        if ( (!(locals[i].equals(lv.locals[i]))) && (locals[i] instanceof UninitializedObjectType) &&
    150                (lv.locals[i] instanceof UninitializedObjectType) ) {
    151            throw new StructuralCodeConstraintException(
    152                "Backwards branch with an uninitialized object in the local variables detected.");
    153        }
    154        // If we just didn't know that it was initialized, we have now learned.
    155        if (locals[i] instanceof UninitializedObjectType) {
    156            if (! (lv.locals[i] instanceof UninitializedObjectType)) {
    157                locals[i] = ((UninitializedObjectType) locals[i]).getInitialized();
    158            }
    159        }
    160        if ((locals[i] instanceof ReferenceType) && (lv.locals[i] instanceof ReferenceType)) {
    161            if (! locals[i].equals(lv.locals[i])) { // needed in case of two UninitializedObjectType instances
    162                final Type sup = ((ReferenceType) locals[i]).getFirstCommonSuperclass((ReferenceType) (lv.locals[i]));
    163
    164                if (sup != null) {
    165                    locals[i] = sup;
    166                }
    167                else{
    168                    // We should have checked this in Pass2!
    169                    throw new AssertionViolatedException(
    170                        "Could not load all the super classes of '"+locals[i]+"' and '"+lv.locals[i]+"'.");
    171                }
    172            }
    173        }
    174        else{
    175            if (! (locals[i].equals(lv.locals[i])) ) {
    176/*TODO
    177                if ((locals[i] instanceof org.apache.bcel.generic.ReturnaddressType) &&
    178                    (lv.locals[i] instanceof org.apache.bcel.generic.ReturnaddressType)) {
    179                    //System.err.println("merging "+locals[i]+" and "+lv.locals[i]);
    180                    throw new AssertionViolatedException("Merging different ReturnAddresses: '"+locals[i]+"' and '"+lv.locals[i]+"'.");
    181                }
    182*/
    183                locals[i] = Type.UNKNOWN;
    184            }
    185        }
    186        } catch (final ClassNotFoundException e) {
    187        // FIXME: maybe not the best way to handle this
    188        throw new AssertionViolatedException("Missing class: " + e, e);
    189        }
    190    }
    191
    192    /**
    193     * Returns a String representation of this object.
    194     */
    195    @Override
    196    public String toString() {
    197        final StringBuilder sb = new StringBuilder();
    198        for (int i=0; i<locals.length; i++) {
    199            sb.append(Integer.toString(i));
    200            sb.append(": ");
    201            sb.append(locals[i]);
    202            sb.append("\n");
    203        }
    204        return sb.toString();
    205    }
    206
    207    /**
    208     * Replaces all occurences of u in this local variables set
    209     * with an "initialized" ObjectType.
    210     */
    211    public void initializeObject(final UninitializedObjectType u) {
    212        for (int i=0; i<locals.length; i++) {
    213            if (locals[i] == u) {
    214                locals[i] = u.getInitialized();
    215            }
    216        }
    217    }
    218}