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