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;
025
026/**
027 * This class represents a chunk of Java byte code contained in a
028 * method. It is instantiated by the
029 * <em>Attribute.readAttribute()</em> method. A <em>Code</em>
030 * attribute contains informations about operand stack, local
031 * variables, byte code and the exceptions handled within this
032 * method.
033 *
034 * This attribute has attributes itself, namely <em>LineNumberTable</em> which
035 * is used for debugging purposes and <em>LocalVariableTable</em> which
036 * contains information about the local variables.
037 *
038 * @see     Attribute
039 * @see     CodeException
040 * @see     LineNumberTable
041 * @see LocalVariableTable
042 */
043public final class Code extends Attribute {
044
045    private int maxStack; // Maximum size of stack used by this method  // TODO this could be made final (setter is not used)
046    private int maxLocals; // Number of local variables  // TODO this could be made final (setter is not used)
047    private byte[] code; // Actual byte code
048    private CodeException[] exceptionTable; // Table of handled exceptions
049    private Attribute[] attributes; // or LocalVariable
050
051
052    /**
053     * Initialize from another object. Note that both objects use the same
054     * references (shallow copy). Use copy() for a physical copy.
055     */
056    public Code(final Code c) {
057        this(c.getNameIndex(), c.getLength(), c.getMaxStack(), c.getMaxLocals(), c.getCode(), c
058                .getExceptionTable(), c.getAttributes(), c.getConstantPool());
059    }
060
061
062    /**
063     * @param name_index Index pointing to the name <em>Code</em>
064     * @param length Content length in bytes
065     * @param file Input stream
066     * @param constant_pool Array of constants
067     */
068    Code(final int name_index, final int length, final DataInput file, final ConstantPool constant_pool)
069            throws IOException {
070        // Initialize with some default values which will be overwritten later
071        this(name_index, length, file.readUnsignedShort(), file.readUnsignedShort(), (byte[]) null,
072                (CodeException[]) null, (Attribute[]) null, constant_pool);
073        final int code_length = file.readInt();
074        code = new byte[code_length]; // Read byte code
075        file.readFully(code);
076        /* Read exception table that contains all regions where an exception
077         * handler is active, i.e., a try { ... } catch() block.
078         */
079        final int exception_table_length = file.readUnsignedShort();
080        exceptionTable = new CodeException[exception_table_length];
081        for (int i = 0; i < exception_table_length; i++) {
082            exceptionTable[i] = new CodeException(file);
083        }
084        /* Read all attributes, currently `LineNumberTable' and
085         * `LocalVariableTable'
086         */
087        final int attributes_count = file.readUnsignedShort();
088        attributes = new Attribute[attributes_count];
089        for (int i = 0; i < attributes_count; i++) {
090            attributes[i] = Attribute.readAttribute(file, constant_pool);
091        }
092        /* Adjust length, because of setAttributes in this(), s.b.  length
093         * is incorrect, because it didn't take the internal attributes
094         * into account yet! Very subtle bug, fixed in 3.1.1.
095         */
096        super.setLength(length);
097    }
098
099
100    /**
101     * @param name_index Index pointing to the name <em>Code</em>
102     * @param length Content length in bytes
103     * @param maxStack Maximum size of stack
104     * @param maxLocals Number of local variables
105     * @param code Actual byte code
106     * @param exceptionTable of handled exceptions
107     * @param attributes Attributes of code: LineNumber or LocalVariable
108     * @param constant_pool Array of constants
109     */
110    public Code(final int name_index, final int length, final int maxStack, final int maxLocals, final byte[] code,
111            final CodeException[] exceptionTable, final Attribute[] attributes, final ConstantPool constant_pool) {
112        super(Const.ATTR_CODE, name_index, length, constant_pool);
113        this.maxStack = maxStack;
114        this.maxLocals = maxLocals;
115        this.code = code != null ? code : new byte[0];
116        this.exceptionTable = exceptionTable != null ? exceptionTable : new CodeException[0];
117        this.attributes = attributes != null ? attributes : new Attribute[0];
118        super.setLength(calculateLength()); // Adjust length
119    }
120
121
122    /**
123     * Called by objects that are traversing the nodes of the tree implicitely
124     * defined by the contents of a Java class. I.e., the hierarchy of methods,
125     * fields, attributes, etc. spawns a tree of objects.
126     *
127     * @param v Visitor object
128     */
129    @Override
130    public void accept( final Visitor v ) {
131        v.visitCode(this);
132    }
133
134
135    /**
136     * Dump code attribute to file stream in binary format.
137     *
138     * @param file Output file stream
139     * @throws IOException
140     */
141    @Override
142    public void dump( final DataOutputStream file ) throws IOException {
143        super.dump(file);
144        file.writeShort(maxStack);
145        file.writeShort(maxLocals);
146        file.writeInt(code.length);
147        file.write(code, 0, code.length);
148        file.writeShort(exceptionTable.length);
149        for (final CodeException exception : exceptionTable) {
150            exception.dump(file);
151        }
152        file.writeShort(attributes.length);
153        for (final Attribute attribute : attributes) {
154            attribute.dump(file);
155        }
156    }
157
158
159    /**
160     * @return Collection of code attributes.
161     * @see Attribute
162     */
163    public Attribute[] getAttributes() {
164        return attributes;
165    }
166
167
168    /**
169     * @return LineNumberTable of Code, if it has one
170     */
171    public LineNumberTable getLineNumberTable() {
172        for (final Attribute attribute : attributes) {
173            if (attribute instanceof LineNumberTable) {
174                return (LineNumberTable) attribute;
175            }
176        }
177        return null;
178    }
179
180
181    /**
182     * @return LocalVariableTable of Code, if it has one
183     */
184    public LocalVariableTable getLocalVariableTable() {
185        for (final Attribute attribute : attributes) {
186            if (attribute instanceof LocalVariableTable) {
187                return (LocalVariableTable) attribute;
188            }
189        }
190        return null;
191    }
192
193
194    /**
195     * @return Actual byte code of the method.
196     */
197    public byte[] getCode() {
198        return code;
199    }
200
201
202    /**
203     * @return Table of handled exceptions.
204     * @see CodeException
205     */
206    public CodeException[] getExceptionTable() {
207        return exceptionTable;
208    }
209
210
211    /**
212     * @return Number of local variables.
213     */
214    public int getMaxLocals() {
215        return maxLocals;
216    }
217
218
219    /**
220     * @return Maximum size of stack used by this method.
221     */
222    public int getMaxStack() {
223        return maxStack;
224    }
225
226
227    /**
228     * @return the internal length of this code attribute (minus the first 6 bytes)
229     * and excluding all its attributes
230     */
231    private int getInternalLength() {
232        return 2 /*maxStack*/+ 2 /*maxLocals*/+ 4 /*code length*/
233                + code.length /*byte-code*/
234                + 2 /*exception-table length*/
235                + 8 * (exceptionTable == null ? 0 : exceptionTable.length) /* exception table */
236                + 2 /* attributes count */;
237    }
238
239
240    /**
241     * @return the full size of this code attribute, minus its first 6 bytes,
242     * including the size of all its contained attributes
243     */
244    private int calculateLength() {
245        int len = 0;
246        if (attributes != null) {
247            for (final Attribute attribute : attributes) {
248                len += attribute.getLength() + 6 /*attribute header size*/;
249            }
250        }
251        return len + getInternalLength();
252    }
253
254
255    /**
256     * @param attributes the attributes to set for this Code
257     */
258    public void setAttributes( final Attribute[] attributes ) {
259        this.attributes = attributes != null ? attributes : new Attribute[0];
260        super.setLength(calculateLength()); // Adjust length
261    }
262
263
264    /**
265     * @param code byte code
266     */
267    public void setCode( final byte[] code ) {
268        this.code = code != null ? code : new byte[0];
269        super.setLength(calculateLength()); // Adjust length
270    }
271
272
273    /**
274     * @param exceptionTable exception table
275     */
276    public void setExceptionTable( final CodeException[] exceptionTable ) {
277        this.exceptionTable = exceptionTable != null ? exceptionTable : new CodeException[0];
278        super.setLength(calculateLength()); // Adjust length
279    }
280
281
282    /**
283     * @param maxLocals maximum number of local variables
284     */
285    public void setMaxLocals( final int maxLocals ) {
286        this.maxLocals = maxLocals;
287    }
288
289
290    /**
291     * @param maxStack maximum stack size
292     */
293    public void setMaxStack( final int maxStack ) {
294        this.maxStack = maxStack;
295    }
296
297
298    /**
299     * @return String representation of code chunk.
300     */
301    public String toString( final boolean verbose ) {
302        final StringBuilder buf = new StringBuilder(100); // CHECKSTYLE IGNORE MagicNumber
303        buf.append("Code(maxStack = ").append(maxStack).append(", maxLocals = ").append(
304                maxLocals).append(", code_length = ").append(code.length).append(")\n").append(
305                Utility.codeToString(code, super.getConstantPool(), 0, -1, verbose));
306        if (exceptionTable.length > 0) {
307            buf.append("\nException handler(s) = \n").append("From\tTo\tHandler\tType\n");
308            for (final CodeException exception : exceptionTable) {
309                buf.append(exception.toString(super.getConstantPool(), verbose)).append("\n");
310            }
311        }
312        if (attributes.length > 0) {
313            buf.append("\nAttribute(s) = ");
314            for (final Attribute attribute : attributes) {
315                buf.append("\n").append(attribute.getName()).append(":");
316                buf.append("\n").append(attribute);
317            }
318        }
319        return buf.toString();
320    }
321
322
323    /**
324     * @return String representation of code chunk.
325     */
326    @Override
327    public String toString() {
328        return toString(true);
329    }
330
331
332    /**
333     * @return deep copy of this attribute
334     *
335     * @param _constant_pool the constant pool to duplicate
336     */
337    @Override
338    public Attribute copy( final ConstantPool _constant_pool ) {
339        final Code c = (Code) clone();
340        if (code != null) {
341            c.code = new byte[code.length];
342            System.arraycopy(code, 0, c.code, 0, code.length);
343        }
344        c.setConstantPool(_constant_pool);
345        c.exceptionTable = new CodeException[exceptionTable.length];
346        for (int i = 0; i < exceptionTable.length; i++) {
347            c.exceptionTable[i] = exceptionTable[i].copy();
348        }
349        c.attributes = new Attribute[attributes.length];
350        for (int i = 0; i < attributes.length; i++) {
351            c.attributes[i] = attributes[i].copy(_constant_pool);
352        }
353        return c;
354    }
355}