Source code

    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.classfile;
    019
    020import java.io.DataInput;
    021import java.io.DataOutputStream;
    022import java.io.IOException;
    023
    024import org.apache.bcel.Const;
    025import org.apache.bcel.Constants;
    026
    027/**
    028 * This class represents a local variable within a method. It contains its
    029 * scope, name, signature and index on the method's frame.  It is used both
    030 * to represent an element of the LocalVariableTable as well as an element
    031 * of the LocalVariableTypeTable.  The nomenclature used here may be a bit confusing;
    032 * while the two items have the same layout in a class file, a LocalVariableTable
    033 * attribute contains a descriptor_index, not a signature_index.  The
    034 * LocalVariableTypeTable attribute does have a signature_index.
    035 * @see org.apache.bcel.classfile.Utility for more details on the difference.
    036 *
    037 * @see     LocalVariableTable
    038 * @see     LocalVariableTypeTable
    039 */
    040public final class LocalVariable implements Cloneable, Node, Constants {
    041
    042    private int start_pc; // Range in which the variable is valid
    043    private int length;
    044    private int name_index; // Index in constant pool of variable name
    045    // Technically, a decscriptor_index for a local variable table entry
    046    // and a signature_index for a local variable type table entry.
    047    private int signature_index; // Index of variable signature
    048    private int index; /* Variable is index'th local variable on
    049     * this method's frame.
    050     */
    051    private ConstantPool constant_pool;
    052    private int orig_index; // never changes; used to match up with LocalVariableTypeTable entries
    053
    054
    055    /**
    056     * Initializes from another LocalVariable. Note that both objects use the same
    057     * references (shallow copy). Use copy() for a physical copy.
    058     *
    059     * @param localVariable Another LocalVariable.
    060     */
    061    public LocalVariable(final LocalVariable localVariable) {
    062        this(localVariable.getStartPC(), localVariable.getLength(), localVariable.getNameIndex(),
    063                localVariable.getSignatureIndex(), localVariable.getIndex(), localVariable.getConstantPool());
    064        this.orig_index = localVariable.getOrigIndex();
    065    }
    066
    067    /**
    068     * Constructs object from file stream.
    069     * @param file Input stream
    070     * @throws IOException
    071     */
    072    LocalVariable(final DataInput file, final ConstantPool constant_pool) throws IOException {
    073        this(file.readUnsignedShort(), file.readUnsignedShort(), file.readUnsignedShort(), file
    074                .readUnsignedShort(), file.readUnsignedShort(), constant_pool);
    075    }
    076
    077
    078    /**
    079     * @param start_pc Range in which the variable
    080     * @param length ... is valid
    081     * @param name_index Index in constant pool of variable name
    082     * @param signature_index Index of variable's signature
    083     * @param index Variable is `index'th local variable on the method's frame
    084     * @param constant_pool Array of constants
    085     */
    086    public LocalVariable(final int start_pc, final int length, final int name_index, final int signature_index, final int index,
    087            final ConstantPool constant_pool) {
    088        this.start_pc = start_pc;
    089        this.length = length;
    090        this.name_index = name_index;
    091        this.signature_index = signature_index;
    092        this.index = index;
    093        this.constant_pool = constant_pool;
    094        this.orig_index = index;
    095    }
    096
    097
    098    /**
    099     * @param start_pc Range in which the variable
    100     * @param length ... is valid
    101     * @param name_index Index in constant pool of variable name
    102     * @param signature_index Index of variable's signature
    103     * @param index Variable is `index'th local variable on the method's frame
    104     * @param constant_pool Array of constants
    105     * @param orig_index Variable is `index'th local variable on the method's frame prior to any changes
    106     */
    107    public LocalVariable(final int start_pc, final int length, final int name_index, final int signature_index, final int index,
    108            final ConstantPool constant_pool, final int orig_index) {
    109        this.start_pc = start_pc;
    110        this.length = length;
    111        this.name_index = name_index;
    112        this.signature_index = signature_index;
    113        this.index = index;
    114        this.constant_pool = constant_pool;
    115        this.orig_index = orig_index;
    116    }
    117
    118
    119    /**
    120     * Called by objects that are traversing the nodes of the tree implicitely
    121     * defined by the contents of a Java class. I.e., the hierarchy of methods,
    122     * fields, attributes, etc. spawns a tree of objects.
    123     *
    124     * @param v Visitor object
    125     */
    126    @Override
    127    public void accept( final Visitor v ) {
    128        v.visitLocalVariable(this);
    129    }
    130
    131
    132    /**
    133     * Dumps local variable to file stream in binary format.
    134     *
    135     * @param dataOutputStream Output file stream
    136     * @exception IOException if an I/O error occurs.
    137     * @see java.io.FilterOutputStream#out
    138     */
    139    public void dump(final DataOutputStream dataOutputStream) throws IOException {
    140        dataOutputStream.writeShort(start_pc);
    141        dataOutputStream.writeShort(length);
    142        dataOutputStream.writeShort(name_index);
    143        dataOutputStream.writeShort(signature_index);
    144        dataOutputStream.writeShort(index);
    145    }
    146
    147    /**
    148     * @return Constant pool used by this object.
    149     */
    150    public ConstantPool getConstantPool() {
    151        return constant_pool;
    152    }
    153
    154
    155    /**
    156     * @return Variable is valid within getStartPC() .. getStartPC()+getLength()
    157     */
    158    public int getLength() {
    159        return length;
    160    }
    161
    162
    163    /**
    164     * @return Variable name.
    165     */
    166    public String getName() {
    167        ConstantUtf8 c;
    168        c = (ConstantUtf8) constant_pool.getConstant(name_index, Const.CONSTANT_Utf8);
    169        return c.getBytes();
    170    }
    171
    172
    173    /**
    174     * @return Index in constant pool of variable name.
    175     */
    176    public int getNameIndex() {
    177        return name_index;
    178    }
    179
    180
    181    /**
    182     * @return Signature.
    183     */
    184    public String getSignature() {
    185        ConstantUtf8 c;
    186        c = (ConstantUtf8) constant_pool.getConstant(signature_index, Const.CONSTANT_Utf8);
    187        return c.getBytes();
    188    }
    189
    190
    191    /**
    192     * @return Index in constant pool of variable signature.
    193     */
    194    public int getSignatureIndex() {
    195        return signature_index;
    196    }
    197
    198
    199    /**
    200     * @return index of register where variable is stored
    201     */
    202    public int getIndex() {
    203        return index;
    204    }
    205
    206
    207    /**
    208     * @return index of register where variable was originally stored
    209     */
    210    public int getOrigIndex() {
    211        return orig_index;
    212    }
    213
    214
    215    /**
    216     * @return Start of range where the variable is valid
    217     */
    218    public int getStartPC() {
    219        return start_pc;
    220    }
    221
    222
    223    /*
    224     * Helper method shared with LocalVariableTypeTable
    225     */
    226    String toStringShared( final boolean typeTable ) {
    227        final String name = getName();
    228        final String signature = Utility.signatureToString(getSignature(), false);
    229        final String label = "LocalVariable" + (typeTable ? "Types" : "" );
    230        return label + "(start_pc = " + start_pc + ", length = " + length + ", index = "
    231                + index + ":" + signature + " " + name + ")";
    232    }
    233
    234
    235    /**
    236     * @param constant_pool Constant pool to be used for this object.
    237     */
    238    public void setConstantPool( final ConstantPool constant_pool ) {
    239        this.constant_pool = constant_pool;
    240    }
    241
    242
    243    /**
    244     * @param length the length of this local variable
    245     */
    246    public void setLength( final int length ) {
    247        this.length = length;
    248    }
    249
    250
    251    /**
    252     * @param name_index the index into the constant pool for the name of this variable
    253     */
    254    public void setNameIndex( final int name_index ) { // TODO unused
    255        this.name_index = name_index;
    256    }
    257
    258
    259    /**
    260     * @param signature_index the index into the constant pool for the signature of this variable
    261     */
    262    public void setSignatureIndex( final int signature_index ) { // TODO unused
    263        this.signature_index = signature_index;
    264    }
    265
    266
    267    /**
    268     * @param index the index in the local variable table of this variable
    269     */
    270    public void setIndex( final int index ) { // TODO unused
    271        this.index = index;
    272    }
    273
    274
    275    /**
    276     * @param start_pc Specify range where the local variable is valid.
    277     */
    278    public void setStartPC( final int start_pc ) { // TODO unused
    279        this.start_pc = start_pc;
    280    }
    281
    282
    283    /**
    284     * @return string representation.
    285     */
    286    @Override
    287    public String toString() {
    288        return toStringShared(false);
    289    }
    290
    291
    292    /**
    293     * @return deep copy of this object
    294     */
    295    public LocalVariable copy() {
    296        try {
    297            return (LocalVariable) clone();
    298        } catch (final CloneNotSupportedException e) {
    299            // TODO should this throw?
    300        }
    301        return null;
    302    }
    303}