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 */
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.bcel.util.Args;
026import org.apache.commons.lang3.ArrayUtils;
027
028/**
029 * This class represents a chunk of Java byte code contained in a method. It is instantiated by the
030 * <em>Attribute.readAttribute()</em> method. A <em>Code</em> attribute contains informations about operand stack, local
031 * variables, byte code and the exceptions handled within this method.
032 *
033 * This attribute has attributes itself, namely <em>LineNumberTable</em> which is used for debugging purposes and
034 * <em>LocalVariableTable</em> which contains information about the local variables.
035 *
036 * <pre>
037 * Code_attribute {
038 *   u2 attribute_name_index;
039 *   u4 attribute_length;
040 *   u2 max_stack;
041 *   u2 max_locals;
042 *   u4 code_length;
043 *   u1 code[code_length];
044 *   u2 exception_table_length;
045 *   {
046 *     u2 start_pc;
047 *     u2 end_pc;
048 *     u2 handler_pc;
049 *     u2 catch_type;
050 *   } exception_table[exception_table_length];
051 *   u2 attributes_count;
052 *   attribute_info attributes[attributes_count];
053 * }
054 * </pre>
055 * @see Attribute
056 * @see CodeException
057 * @see LineNumberTable
058 * @see LocalVariableTable
059 */
060public final class Code extends Attribute {
061
062    private int maxStack; // Maximum size of stack used by this method // TODO this could be made final (setter is not used)
063    private int maxLocals; // Number of local variables // TODO this could be made final (setter is not used)
064    private byte[] code; // Actual byte code
065    private CodeException[] exceptionTable; // Table of handled exceptions
066    private Attribute[] attributes; // or LocalVariable
067
068    /**
069     * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
070     * physical copy.
071     *
072     * @param code The source Code.
073     */
074    public Code(final Code code) {
075        this(code.getNameIndex(), code.getLength(), code.getMaxStack(), code.getMaxLocals(), code.getCode(), code.getExceptionTable(), code.getAttributes(),
076                code.getConstantPool());
077    }
078
079    /**
080     * @param nameIndex Index pointing to the name <em>Code</em>
081     * @param length Content length in bytes
082     * @param file Input stream
083     * @param constantPool Array of constants
084     */
085    Code(final int nameIndex, final int length, final DataInput file, final ConstantPool constantPool) throws IOException {
086        // Initialize with some default values which will be overwritten later
087        this(nameIndex, length, file.readUnsignedShort(), file.readUnsignedShort(), (byte[]) null, (CodeException[]) null, (Attribute[]) null, constantPool);
088        final int codeLength = Args.requireU4(file.readInt(), 1, "Code length attribute");
089        code = new byte[codeLength]; // Read byte code
090        file.readFully(code);
091        /*
092         * Read exception table that contains all regions where an exception handler is active, i.e., a try { ... } catch ()
093         * block.
094         */
095        final int exceptionTableLength = file.readUnsignedShort();
096        exceptionTable = new CodeException[exceptionTableLength];
097        for (int i = 0; i < exceptionTableLength; i++) {
098            exceptionTable[i] = new CodeException(file);
099        }
100        /*
101         * Read all attributes, currently 'LineNumberTable' and 'LocalVariableTable'
102         */
103        final int attributesCount = file.readUnsignedShort();
104        attributes = new Attribute[attributesCount];
105        for (int i = 0; i < attributesCount; i++) {
106            attributes[i] = Attribute.readAttribute(file, constantPool);
107        }
108        /*
109         * Adjust length, because of setAttributes in this(), s.b. length is incorrect, because it didn't take the internal
110         * attributes into account yet! Very subtle bug, fixed in 3.1.1.
111         */
112        super.setLength(length);
113    }
114
115    /**
116     * @param nameIndex Index pointing to the name <em>Code</em>
117     * @param length Content length in bytes
118     * @param maxStack Maximum size of stack
119     * @param maxLocals Number of local variables
120     * @param code Actual byte code
121     * @param exceptionTable of handled exceptions
122     * @param attributes Attributes of code: LineNumber or LocalVariable
123     * @param constantPool Array of constants
124     */
125    public Code(final int nameIndex, final int length, final int maxStack, final int maxLocals, final byte[] code, final CodeException[] exceptionTable,
126        final Attribute[] attributes, final ConstantPool constantPool) {
127        super(Const.ATTR_CODE, nameIndex, length, constantPool);
128        this.maxStack = Args.requireU2(maxStack, "maxStack");
129        this.maxLocals = Args.requireU2(maxLocals, "maxLocals");
130        this.code = code != null ? code : ArrayUtils.EMPTY_BYTE_ARRAY;
131        this.exceptionTable = exceptionTable != null ? exceptionTable : CodeException.EMPTY_CODE_EXCEPTION_ARRAY;
132        Args.requireU2(this.exceptionTable.length, "exceptionTable.length");
133        this.attributes = attributes != null ? attributes : EMPTY_ARRAY;
134        super.setLength(calculateLength()); // Adjust length
135    }
136
137    /**
138     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
139     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
140     *
141     * @param v Visitor object
142     */
143    @Override
144    public void accept(final Visitor v) {
145        v.visitCode(this);
146    }
147
148    /**
149     * @return the full size of this code attribute, minus its first 6 bytes, including the size of all its contained
150     *         attributes
151     */
152    private int calculateLength() {
153        int len = 0;
154        if (attributes != null) {
155            for (final Attribute attribute : attributes) {
156                len += attribute.getLength() + 6 /* attribute header size */;
157            }
158        }
159        return len + getInternalLength();
160    }
161
162    /**
163     * @return deep copy of this attribute
164     *
165     * @param constantPool the constant pool to duplicate
166     */
167    @Override
168    public Attribute copy(final ConstantPool constantPool) {
169        final Code c = (Code) clone();
170        if (code != null) {
171            c.code = code.clone();
172        }
173        c.setConstantPool(constantPool);
174        c.exceptionTable = new CodeException[exceptionTable.length];
175        Arrays.setAll(c.exceptionTable, i -> exceptionTable[i].copy());
176        c.attributes = new Attribute[attributes.length];
177        Arrays.setAll(c.attributes, i -> attributes[i].copy(constantPool));
178        return c;
179    }
180
181    /**
182     * Dump code attribute to file stream in binary format.
183     *
184     * @param file Output file stream
185     * @throws IOException if an I/O error occurs.
186     */
187    @Override
188    public void dump(final DataOutputStream file) throws IOException {
189        super.dump(file);
190        file.writeShort(maxStack);
191        file.writeShort(maxLocals);
192        file.writeInt(code.length);
193        file.write(code, 0, code.length);
194        file.writeShort(exceptionTable.length);
195        for (final CodeException exception : exceptionTable) {
196            exception.dump(file);
197        }
198        file.writeShort(attributes.length);
199        for (final Attribute attribute : attributes) {
200            attribute.dump(file);
201        }
202    }
203
204    /**
205     * @return Collection of code attributes.
206     * @see Attribute
207     */
208    public Attribute[] getAttributes() {
209        return attributes;
210    }
211
212    /**
213     * @return Actual byte code of the method.
214     */
215    public byte[] getCode() {
216        return code;
217    }
218
219    /**
220     * @return Table of handled exceptions.
221     * @see CodeException
222     */
223    public CodeException[] getExceptionTable() {
224        return exceptionTable;
225    }
226
227    /**
228     * @return the internal length of this code attribute (minus the first 6 bytes) and excluding all its attributes
229     */
230    private int getInternalLength() {
231        return 2 /* maxStack */ + 2 /* maxLocals */ + 4 /* code length */
232            + code.length /* byte-code */
233            + 2 /* exception-table length */
234            + 8 * (exceptionTable == null ? 0 : exceptionTable.length) /* exception table */
235            + 2 /* attributes count */;
236    }
237
238    /**
239     * @return LineNumberTable of Code, if it has one
240     */
241    public LineNumberTable getLineNumberTable() {
242        for (final Attribute attribute : attributes) {
243            if (attribute instanceof LineNumberTable) {
244                return (LineNumberTable) attribute;
245            }
246        }
247        return null;
248    }
249
250    /**
251     * @return LocalVariableTable of Code, if it has one
252     */
253    public LocalVariableTable getLocalVariableTable() {
254        for (final Attribute attribute : attributes) {
255            if (attribute instanceof LocalVariableTable) {
256                return (LocalVariableTable) attribute;
257            }
258        }
259        return null;
260    }
261
262    /**
263     * @return Number of local variables.
264     */
265    public int getMaxLocals() {
266        return maxLocals;
267    }
268
269    /**
270     * @return Maximum size of stack used by this method.
271     */
272    public int getMaxStack() {
273        return maxStack;
274    }
275
276    /**
277     * Finds the attribute of {@link StackMap} instance.
278     * @return StackMap of Code, if it has one, else null.
279     * @since 6.8.0
280     */
281    public StackMap getStackMap() {
282        for (final Attribute attribute : attributes) {
283            if (attribute instanceof StackMap) {
284                return (StackMap) attribute;
285            }
286        }
287        return null;
288    }
289
290    /**
291     * @param attributes the attributes to set for this Code
292     */
293    public void setAttributes(final Attribute[] attributes) {
294        this.attributes = attributes != null ? attributes : EMPTY_ARRAY;
295        super.setLength(calculateLength()); // Adjust length
296    }
297
298    /**
299     * @param code byte code
300     */
301    public void setCode(final byte[] code) {
302        this.code = code != null ? code : ArrayUtils.EMPTY_BYTE_ARRAY;
303        super.setLength(calculateLength()); // Adjust length
304    }
305
306    /**
307     * @param exceptionTable exception table
308     */
309    public void setExceptionTable(final CodeException[] exceptionTable) {
310        this.exceptionTable = exceptionTable != null ? exceptionTable : CodeException.EMPTY_CODE_EXCEPTION_ARRAY;
311        super.setLength(calculateLength()); // Adjust length
312    }
313
314    /**
315     * @param maxLocals maximum number of local variables
316     */
317    public void setMaxLocals(final int maxLocals) {
318        this.maxLocals = maxLocals;
319    }
320
321    /**
322     * @param maxStack maximum stack size
323     */
324    public void setMaxStack(final int maxStack) {
325        this.maxStack = maxStack;
326    }
327
328    /**
329     * @return String representation of code chunk.
330     */
331    @Override
332    public String toString() {
333        return toString(true);
334    }
335
336    /**
337     * Converts this object to a String.
338     *
339     * @param verbose Provides verbose output when true.
340     * @return String representation of code chunk.
341     */
342    public String toString(final boolean verbose) {
343        final StringBuilder buf = new StringBuilder(100); // CHECKSTYLE IGNORE MagicNumber
344        buf.append("Code(maxStack = ").append(maxStack).append(", maxLocals = ").append(maxLocals).append(", code_length = ").append(code.length).append(")\n")
345            .append(Utility.codeToString(code, super.getConstantPool(), 0, -1, verbose));
346        if (exceptionTable.length > 0) {
347            buf.append("\nException handler(s) = \n").append("From\tTo\tHandler\tType\n");
348            for (final CodeException exception : exceptionTable) {
349                buf.append(exception.toString(super.getConstantPool(), verbose)).append("\n");
350            }
351        }
352        if (attributes.length > 0) {
353            buf.append("\nAttribute(s) = ");
354            for (final Attribute attribute : attributes) {
355                buf.append("\n").append(attribute.getName()).append(":");
356                buf.append("\n").append(attribute);
357            }
358        }
359        return buf.toString();
360    }
361}