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;
022import java.util.Arrays;
023
024import org.apache.bcel.Const;
025import org.apache.commons.lang3.ArrayUtils;
026
027/**
028 * This class represents a chunk of Java byte code contained in a method. It is instantiated by the
029 * <em>Attribute.readAttribute()</em> method. A <em>Code</em> attribute contains informations about operand stack, local
030 * variables, byte code and the exceptions handled within this method.
031 *
032 * This attribute has attributes itself, namely <em>LineNumberTable</em> which is used for debugging purposes and
033 * <em>LocalVariableTable</em> which contains information about the local variables.
034 *
035 * @see Attribute
036 * @see CodeException
037 * @see LineNumberTable
038 * @see LocalVariableTable
039 */
040public final class Code extends Attribute {
041
042    private int maxStack; // Maximum size of stack used by this method // TODO this could be made final (setter is not used)
043    private int maxLocals; // Number of local variables // TODO this could be made final (setter is not used)
044    private byte[] code; // Actual byte code
045    private CodeException[] exceptionTable; // Table of handled exceptions
046    private Attribute[] attributes; // or LocalVariable
047
048    /**
049     * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
050     * physical copy.
051     */
052    public Code(final Code c) {
053        this(c.getNameIndex(), c.getLength(), c.getMaxStack(), c.getMaxLocals(), c.getCode(), c.getExceptionTable(), c.getAttributes(), c.getConstantPool());
054    }
055
056    /**
057     * @param nameIndex Index pointing to the name <em>Code</em>
058     * @param length Content length in bytes
059     * @param file Input stream
060     * @param constantPool Array of constants
061     */
062    Code(final int nameIndex, final int length, final DataInput file, final ConstantPool constantPool) throws IOException {
063        // Initialize with some default values which will be overwritten later
064        this(nameIndex, length, file.readUnsignedShort(), file.readUnsignedShort(), (byte[]) null, (CodeException[]) null, (Attribute[]) null, constantPool);
065        final int codeLength = file.readInt();
066        code = new byte[codeLength]; // Read byte code
067        file.readFully(code);
068        /*
069         * Read exception table that contains all regions where an exception handler is active, i.e., a try { ... } catch()
070         * block.
071         */
072        final int exceptionTableLength = file.readUnsignedShort();
073        exceptionTable = new CodeException[exceptionTableLength];
074        for (int i = 0; i < exceptionTableLength; i++) {
075            exceptionTable[i] = new CodeException(file);
076        }
077        /*
078         * Read all attributes, currently `LineNumberTable' and `LocalVariableTable'
079         */
080        final int attributesCount = file.readUnsignedShort();
081        attributes = new Attribute[attributesCount];
082        for (int i = 0; i < attributesCount; i++) {
083            attributes[i] = Attribute.readAttribute(file, constantPool);
084        }
085        /*
086         * Adjust length, because of setAttributes in this(), s.b. length is incorrect, because it didn't take the internal
087         * attributes into account yet! Very subtle bug, fixed in 3.1.1.
088         */
089        super.setLength(length);
090    }
091
092    /**
093     * @param nameIndex Index pointing to the name <em>Code</em>
094     * @param length Content length in bytes
095     * @param maxStack Maximum size of stack
096     * @param maxLocals Number of local variables
097     * @param code Actual byte code
098     * @param exceptionTable of handled exceptions
099     * @param attributes Attributes of code: LineNumber or LocalVariable
100     * @param constantPool Array of constants
101     */
102    public Code(final int nameIndex, final int length, final int maxStack, final int maxLocals, final byte[] code, final CodeException[] exceptionTable,
103        final Attribute[] attributes, final ConstantPool constantPool) {
104        super(Const.ATTR_CODE, nameIndex, length, constantPool);
105        this.maxStack = maxStack;
106        this.maxLocals = maxLocals;
107        this.code = code != null ? code : ArrayUtils.EMPTY_BYTE_ARRAY;
108        this.exceptionTable = exceptionTable != null ? exceptionTable : CodeException.EMPTY_CODE_EXCEPTION_ARRAY;
109        this.attributes = attributes != null ? attributes : EMPTY_ARRAY;
110        super.setLength(calculateLength()); // Adjust length
111    }
112
113    /**
114     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
115     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
116     *
117     * @param v Visitor object
118     */
119    @Override
120    public void accept(final Visitor v) {
121        v.visitCode(this);
122    }
123
124    /**
125     * @return the full size of this code attribute, minus its first 6 bytes, including the size of all its contained
126     *         attributes
127     */
128    private int calculateLength() {
129        int len = 0;
130        if (attributes != null) {
131            for (final Attribute attribute : attributes) {
132                len += attribute.getLength() + 6 /* attribute header size */;
133            }
134        }
135        return len + getInternalLength();
136    }
137
138    /**
139     * @return deep copy of this attribute
140     *
141     * @param constantPool the constant pool to duplicate
142     */
143    @Override
144    public Attribute copy(final ConstantPool constantPool) {
145        final Code c = (Code) clone();
146        if (code != null) {
147            c.code = code.clone();
148        }
149        c.setConstantPool(constantPool);
150        c.exceptionTable = new CodeException[exceptionTable.length];
151        Arrays.setAll(c.exceptionTable, i -> exceptionTable[i].copy());
152        c.attributes = new Attribute[attributes.length];
153        Arrays.setAll(c.attributes, i -> attributes[i].copy(constantPool));
154        return c;
155    }
156
157    /**
158     * Dump code attribute to file stream in binary format.
159     *
160     * @param file Output file stream
161     * @throws IOException if an I/O error occurs.
162     */
163    @Override
164    public void dump(final DataOutputStream file) throws IOException {
165        super.dump(file);
166        file.writeShort(maxStack);
167        file.writeShort(maxLocals);
168        file.writeInt(code.length);
169        file.write(code, 0, code.length);
170        file.writeShort(exceptionTable.length);
171        for (final CodeException exception : exceptionTable) {
172            exception.dump(file);
173        }
174        file.writeShort(attributes.length);
175        for (final Attribute attribute : attributes) {
176            attribute.dump(file);
177        }
178    }
179
180    /**
181     * @return Collection of code attributes.
182     * @see Attribute
183     */
184    public Attribute[] getAttributes() {
185        return attributes;
186    }
187
188    /**
189     * @return Actual byte code of the method.
190     */
191    public byte[] getCode() {
192        return code;
193    }
194
195    /**
196     * @return Table of handled exceptions.
197     * @see CodeException
198     */
199    public CodeException[] getExceptionTable() {
200        return exceptionTable;
201    }
202
203    /**
204     * @return the internal length of this code attribute (minus the first 6 bytes) and excluding all its attributes
205     */
206    private int getInternalLength() {
207        return 2 /* maxStack */ + 2 /* maxLocals */ + 4 /* code length */
208            + code.length /* byte-code */
209            + 2 /* exception-table length */
210            + 8 * (exceptionTable == null ? 0 : exceptionTable.length) /* exception table */
211            + 2 /* attributes count */;
212    }
213
214    /**
215     * @return LineNumberTable of Code, if it has one
216     */
217    public LineNumberTable getLineNumberTable() {
218        for (final Attribute attribute : attributes) {
219            if (attribute instanceof LineNumberTable) {
220                return (LineNumberTable) attribute;
221            }
222        }
223        return null;
224    }
225
226    /**
227     * @return LocalVariableTable of Code, if it has one
228     */
229    public LocalVariableTable getLocalVariableTable() {
230        for (final Attribute attribute : attributes) {
231            if (attribute instanceof LocalVariableTable) {
232                return (LocalVariableTable) attribute;
233            }
234        }
235        return null;
236    }
237
238    /**
239     * @return Number of local variables.
240     */
241    public int getMaxLocals() {
242        return maxLocals;
243    }
244
245    /**
246     * @return Maximum size of stack used by this method.
247     */
248    public int getMaxStack() {
249        return maxStack;
250    }
251
252    /**
253     * @param attributes the attributes to set for this Code
254     */
255    public void setAttributes(final Attribute[] attributes) {
256        this.attributes = attributes != null ? attributes : EMPTY_ARRAY;
257        super.setLength(calculateLength()); // Adjust length
258    }
259
260    /**
261     * @param code byte code
262     */
263    public void setCode(final byte[] code) {
264        this.code = code != null ? code : ArrayUtils.EMPTY_BYTE_ARRAY;
265        super.setLength(calculateLength()); // Adjust length
266    }
267
268    /**
269     * @param exceptionTable exception table
270     */
271    public void setExceptionTable(final CodeException[] exceptionTable) {
272        this.exceptionTable = exceptionTable != null ? exceptionTable : CodeException.EMPTY_CODE_EXCEPTION_ARRAY;
273        super.setLength(calculateLength()); // Adjust length
274    }
275
276    /**
277     * @param maxLocals maximum number of local variables
278     */
279    public void setMaxLocals(final int maxLocals) {
280        this.maxLocals = maxLocals;
281    }
282
283    /**
284     * @param maxStack maximum stack size
285     */
286    public void setMaxStack(final int maxStack) {
287        this.maxStack = maxStack;
288    }
289
290    /**
291     * @return String representation of code chunk.
292     */
293    @Override
294    public String toString() {
295        return toString(true);
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(maxLocals).append(", code_length = ").append(code.length).append(")\n")
304            .append(Utility.codeToString(code, super.getConstantPool(), 0, -1, verbose));
305        if (exceptionTable.length > 0) {
306            buf.append("\nException handler(s) = \n").append("From\tTo\tHandler\tType\n");
307            for (final CodeException exception : exceptionTable) {
308                buf.append(exception.toString(super.getConstantPool(), verbose)).append("\n");
309            }
310        }
311        if (attributes.length > 0) {
312            buf.append("\nAttribute(s) = ");
313            for (final Attribute attribute : attributes) {
314                buf.append("\n").append(attribute.getName()).append(":");
315                buf.append("\n").append(attribute);
316            }
317        }
318        return buf.toString();
319    }
320}