    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.classfile;
    018
    019import java.io.DataInput;
    020import java.io.DataOutputStream;
    021import java.io.IOException;
    022
    023import org.apache.bcel.Constants;
    024import org.apache.bcel.util.Args;
    025
    026/**
    027 * This class represents a local variable within a method. It contains its scope, name, signature and index on the
    028 * method's frame. It is used both to represent an element of the LocalVariableTable as well as an element of the
    029 * LocalVariableTypeTable. The nomenclature used here may be a bit confusing; while the two items have the same layout
    030 * in a class file, a LocalVariableTable attribute contains a descriptor_index, not a signatureIndex. The
    031 * LocalVariableTypeTable attribute does have a signatureIndex.
    032 *
    033 * @see org.apache.bcel.classfile.Utility for more details on the difference.
    034 *
    035 * @see LocalVariableTable
    036 * @see LocalVariableTypeTable
    037 */
    038public final class LocalVariable implements Cloneable, Node, Constants {
    039
    040    static final LocalVariable[] EMPTY_ARRAY = {};
    041
    042    /** Range in which the variable is valid. */
    043    private int startPc;
    044
    045    private int length;
    046
    047    /** Index in constant pool of variable name. */
    048    private int nameIndex;
    049
    050    /**
    051     * Technically, a decscriptor_index for a local variable table entry and a signatureIndex for a local variable type table entry. Index of variable signature
    052     */
    053    private int signatureIndex;
    054
    055    /*
    056     * Variable is index'th local variable on this method's frame.
    057     */
    058    private int index;
    059
    060    private ConstantPool constantPool;
    061
    062    /** Never changes; used to match up with LocalVariableTypeTable entries. */
    063    private final int origIndex;
    064
    065    /**
    066     * Constructs object from file stream.
    067     *
    068     * @param file Input stream
    069     * @throws IOException if an I/O error occurs.
    070     */
    071    LocalVariable(final DataInput file, final ConstantPool constantPool) throws IOException {
    072        this(file.readUnsignedShort(), file.readUnsignedShort(), file.readUnsignedShort(), file.readUnsignedShort(), file.readUnsignedShort(), constantPool);
    073    }
    074
    075    /**
    076     * @param startPc Range in which the variable
    077     * @param length ... is valid
    078     * @param nameIndex Index in constant pool of variable name
    079     * @param signatureIndex Index of variable's signature
    080     * @param index Variable is 'index'th local variable on the method's frame
    081     * @param constantPool Array of constants
    082     */
    083    public LocalVariable(final int startPc, final int length, final int nameIndex, final int signatureIndex, final int index, final ConstantPool constantPool) {
    084        this(startPc, length, nameIndex, signatureIndex, index, constantPool, index);
    085    }
    086
    087    /**
    088     * @param startPc Range in which the variable
    089     * @param length ... is valid
    090     * @param nameIndex Index in constant pool of variable name
    091     * @param signatureIndex Index of variable's signature
    092     * @param index Variable is 'index'th local variable on the method's frame
    093     * @param constantPool Array of constants
    094     * @param origIndex Variable is 'index'th local variable on the method's frame prior to any changes
    095     */
    096    public LocalVariable(final int startPc, final int length, final int nameIndex, final int signatureIndex, final int index, final ConstantPool constantPool,
    097        final int origIndex) {
    098        this.startPc = Args.requireU2(startPc, "startPc");
    099        this.length = Args.requireU2(length, "length");
    100        this.nameIndex = Args.requireU2(nameIndex, "nameIndex");
    101        this.signatureIndex = Args.requireU2(signatureIndex, "signatureIndex");
    102        this.index = Args.requireU2(index, "index");
    103        this.origIndex = Args.requireU2(origIndex, "origIndex");
    104        this.constantPool = constantPool;
    105    }
    106
    107    /**
    108     * Initializes from another LocalVariable. Note that both objects use the same references (shallow copy). Use copy() for
    109     * a physical copy.
    110     *
    111     * @param localVariable Another LocalVariable.
    112     */
    113    public LocalVariable(final LocalVariable localVariable) {
    114        this(localVariable.getStartPC(), localVariable.getLength(), localVariable.getNameIndex(), localVariable.getSignatureIndex(), localVariable.getIndex(),
    115            localVariable.getConstantPool());
    116    }
    117
    118    /**
    119     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    120     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    121     *
    122     * @param v Visitor object
    123     */
    124    @Override
    125    public void accept(final Visitor v) {
    126        v.visitLocalVariable(this);
    127    }
    128
    129    /**
    130     * @return deep copy of this object
    131     */
    132    public LocalVariable copy() {
    133        try {
    134            return (LocalVariable) clone();
    135        } catch (final CloneNotSupportedException e) {
    136            // TODO should this throw?
    137        }
    138        return null;
    139    }
    140
    141    /**
    142     * Dumps local variable to file stream in binary format.
    143     *
    144     * @param dataOutputStream Output file stream
    145     * @throws IOException if an I/O error occurs.
    146     * @see java.io.FilterOutputStream#out
    147     */
    148    public void dump(final DataOutputStream dataOutputStream) throws IOException {
    149        dataOutputStream.writeShort(startPc);
    150        dataOutputStream.writeShort(length);
    151        dataOutputStream.writeShort(nameIndex);
    152        dataOutputStream.writeShort(signatureIndex);
    153        dataOutputStream.writeShort(index);
    154    }
    155
    156    /**
    157     * @return Constant pool used by this object.
    158     */
    159    public ConstantPool getConstantPool() {
    160        return constantPool;
    161    }
    162
    163    /**
    164     * @return index of register where variable is stored
    165     */
    166    public int getIndex() {
    167        return index;
    168    }
    169
    170    /**
    171     * @return Variable is valid within getStartPC() .. getStartPC()+getLength()
    172     */
    173    public int getLength() {
    174        return length;
    175    }
    176
    177    /**
    178     * @return Variable name.
    179     */
    180    public String getName() {
    181        return constantPool.getConstantUtf8(nameIndex).getBytes();
    182    }
    183
    184    /**
    185     * @return Index in constant pool of variable name.
    186     */
    187    public int getNameIndex() {
    188        return nameIndex;
    189    }
    190
    191    /**
    192     * @return index of register where variable was originally stored
    193     */
    194    public int getOrigIndex() {
    195        return origIndex;
    196    }
    197
    198    /**
    199     * @return Signature.
    200     */
    201    public String getSignature() {
    202        return constantPool.getConstantUtf8(signatureIndex).getBytes();
    203    }
    204
    205    /**
    206     * @return Index in constant pool of variable signature.
    207     */
    208    public int getSignatureIndex() {
    209        return signatureIndex;
    210    }
    211
    212    /**
    213     * @return Start of range where the variable is valid
    214     */
    215    public int getStartPC() {
    216        return startPc;
    217    }
    218
    219    /**
    220     * @param constantPool Constant pool to be used for this object.
    221     */
    222    public void setConstantPool(final ConstantPool constantPool) {
    223        this.constantPool = constantPool;
    224    }
    225
    226    /**
    227     * @param index the index in the local variable table of this variable
    228     */
    229    public void setIndex(final int index) { // TODO unused
    230        this.index = index;
    231    }
    232
    233    /**
    234     * @param length the length of this local variable
    235     */
    236    public void setLength(final int length) {
    237        this.length = length;
    238    }
    239
    240    /**
    241     * @param nameIndex the index into the constant pool for the name of this variable
    242     */
    243    public void setNameIndex(final int nameIndex) { // TODO unused
    244        this.nameIndex = nameIndex;
    245    }
    246
    247    /**
    248     * @param signatureIndex the index into the constant pool for the signature of this variable
    249     */
    250    public void setSignatureIndex(final int signatureIndex) { // TODO unused
    251        this.signatureIndex = signatureIndex;
    252    }
    253
    254    /**
    255     * @param startPc Specify range where the local variable is valid.
    256     */
    257    public void setStartPC(final int startPc) { // TODO unused
    258        this.startPc = startPc;
    259    }
    260
    261    /**
    262     * @return string representation.
    263     */
    264    @Override
    265    public String toString() {
    266        return toStringShared(false);
    267    }
    268
    269    /*
    270     * Helper method shared with LocalVariableTypeTable
    271     */
    272    String toStringShared(final boolean typeTable) {
    273        final String name = getName();
    274        final String signature = Utility.signatureToString(getSignature(), false);
    275        final String label = "LocalVariable" + (typeTable ? "Types" : "");
    276        return label + "(startPc = " + startPc + ", length = " + length + ", index = " + index + ":" + signature + " " + name + ")";
    277    }
    278}