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.DataInputStream;
021import java.io.DataOutputStream;
022import java.io.IOException;
023import java.util.HashMap;
024import java.util.Map;
025
026import org.apache.bcel.Const;
027import org.apache.bcel.util.Args;
028
029/**
030 * Abstract super class for <em>Attribute</em> objects. Currently the <em>ConstantValue</em>, <em>SourceFile</em>, <em>Code</em>, <em>Exceptiontable</em>,
031 * <em>LineNumberTable</em>, <em>LocalVariableTable</em>, <em>InnerClasses</em> and <em>Synthetic</em> attributes are supported. The <em>Unknown</em> attribute
032 * stands for non-standard-attributes.
033 *
034 * <pre>
035 * attribute_info {
036 *   u2 attribute_name_index;
037 *   u4 attribute_length;
038 *   u1 info[attribute_length];
039 * }
040 * </pre>
041 *
042 * @see ConstantValue
043 * @see SourceFile
044 * @see Code
045 * @see Unknown
046 * @see ExceptionTable
047 * @see LineNumberTable
048 * @see LocalVariableTable
049 * @see InnerClasses
050 * @see Synthetic
051 * @see Deprecated
052 * @see Signature
053 */
054public abstract class Attribute implements Cloneable, Node {
055
056    private static final boolean debug = Boolean.getBoolean(Attribute.class.getCanonicalName() + ".debug"); // Debugging on/off
057
058    private static final Map<String, Object> READERS = new HashMap<>();
059
060    /**
061     * Empty array.
062     *
063     * @since 6.6.0
064     */
065    public static final Attribute[] EMPTY_ARRAY = {};
066
067    /**
068     * Add an Attribute reader capable of parsing (user-defined) attributes named "name". You should not add readers for the
069     * standard attributes such as "LineNumberTable", because those are handled internally.
070     *
071     * @param name the name of the attribute as stored in the class file
072     * @param attributeReader the reader object
073     * @deprecated (6.0) Use {@link #addAttributeReader(String, UnknownAttributeReader)} instead
074     */
075    @java.lang.Deprecated
076    public static void addAttributeReader(final String name, final AttributeReader attributeReader) {
077        READERS.put(name, attributeReader);
078    }
079
080    /**
081     * Add an Attribute reader capable of parsing (user-defined) attributes named "name". You should not add readers for the
082     * standard attributes such as "LineNumberTable", because those are handled internally.
083     *
084     * @param name the name of the attribute as stored in the class file
085     * @param unknownAttributeReader the reader object
086     */
087    public static void addAttributeReader(final String name, final UnknownAttributeReader unknownAttributeReader) {
088        READERS.put(name, unknownAttributeReader);
089    }
090
091    protected static void println(final String msg) {
092        if (debug) {
093            System.err.println(msg);
094        }
095    }
096
097    /**
098     * Class method reads one attribute from the input data stream. This method must not be accessible from the outside. It
099     * is called by the Field and Method constructor methods.
100     *
101     * @see Field
102     * @see Method
103     *
104     * @param dataInput Input stream
105     * @param constantPool Array of constants
106     * @return Attribute
107     * @throws IOException if an I/O error occurs.
108     * @since 6.0
109     */
110    public static Attribute readAttribute(final DataInput dataInput, final ConstantPool constantPool) throws IOException {
111        byte tag = Const.ATTR_UNKNOWN; // Unknown attribute
112        // Get class name from constant pool via 'name_index' indirection
113        final int nameIndex = dataInput.readUnsignedShort();
114        final String name = constantPool.getConstantUtf8(nameIndex).getBytes();
115
116        // Length of data in bytes
117        final int length = dataInput.readInt();
118
119        // Compare strings to find known attribute
120        for (byte i = 0; i < Const.KNOWN_ATTRIBUTES; i++) {
121            if (name.equals(Const.getAttributeName(i))) {
122                tag = i; // found!
123                break;
124            }
125        }
126
127        // Call proper constructor, depending on 'tag'
128        switch (tag) {
129        case Const.ATTR_UNKNOWN:
130            final Object r = READERS.get(name);
131            if (r instanceof UnknownAttributeReader) {
132                return ((UnknownAttributeReader) r).createAttribute(nameIndex, length, dataInput, constantPool);
133            }
134            return new Unknown(nameIndex, length, dataInput, constantPool);
135        case Const.ATTR_CONSTANT_VALUE:
136            return new ConstantValue(nameIndex, length, dataInput, constantPool);
137        case Const.ATTR_SOURCE_FILE:
138            return new SourceFile(nameIndex, length, dataInput, constantPool);
139        case Const.ATTR_CODE:
140            return new Code(nameIndex, length, dataInput, constantPool);
141        case Const.ATTR_EXCEPTIONS:
142            return new ExceptionTable(nameIndex, length, dataInput, constantPool);
143        case Const.ATTR_LINE_NUMBER_TABLE:
144            return new LineNumberTable(nameIndex, length, dataInput, constantPool);
145        case Const.ATTR_LOCAL_VARIABLE_TABLE:
146            return new LocalVariableTable(nameIndex, length, dataInput, constantPool);
147        case Const.ATTR_INNER_CLASSES:
148            return new InnerClasses(nameIndex, length, dataInput, constantPool);
149        case Const.ATTR_SYNTHETIC:
150            return new Synthetic(nameIndex, length, dataInput, constantPool);
151        case Const.ATTR_DEPRECATED:
152            return new Deprecated(nameIndex, length, dataInput, constantPool);
153        case Const.ATTR_PMG:
154            return new PMGClass(nameIndex, length, dataInput, constantPool);
155        case Const.ATTR_SIGNATURE:
156            return new Signature(nameIndex, length, dataInput, constantPool);
157        case Const.ATTR_STACK_MAP:
158            // old style stack map: unneeded for JDK5 and below;
159            // illegal(?) for JDK6 and above. So just delete with a warning.
160            println("Warning: Obsolete StackMap attribute ignored.");
161            return new Unknown(nameIndex, length, dataInput, constantPool);
162        case Const.ATTR_RUNTIME_VISIBLE_ANNOTATIONS:
163            return new RuntimeVisibleAnnotations(nameIndex, length, dataInput, constantPool);
164        case Const.ATTR_RUNTIME_INVISIBLE_ANNOTATIONS:
165            return new RuntimeInvisibleAnnotations(nameIndex, length, dataInput, constantPool);
166        case Const.ATTR_RUNTIME_VISIBLE_PARAMETER_ANNOTATIONS:
167            return new RuntimeVisibleParameterAnnotations(nameIndex, length, dataInput, constantPool);
168        case Const.ATTR_RUNTIME_INVISIBLE_PARAMETER_ANNOTATIONS:
169            return new RuntimeInvisibleParameterAnnotations(nameIndex, length, dataInput, constantPool);
170        case Const.ATTR_ANNOTATION_DEFAULT:
171            return new AnnotationDefault(nameIndex, length, dataInput, constantPool);
172        case Const.ATTR_LOCAL_VARIABLE_TYPE_TABLE:
173            return new LocalVariableTypeTable(nameIndex, length, dataInput, constantPool);
174        case Const.ATTR_ENCLOSING_METHOD:
175            return new EnclosingMethod(nameIndex, length, dataInput, constantPool);
176        case Const.ATTR_STACK_MAP_TABLE:
177            // read new style stack map: StackMapTable. The rest of the code
178            // calls this a StackMap for historical reasons.
179            return new StackMap(nameIndex, length, dataInput, constantPool);
180        case Const.ATTR_BOOTSTRAP_METHODS:
181            return new BootstrapMethods(nameIndex, length, dataInput, constantPool);
182        case Const.ATTR_METHOD_PARAMETERS:
183            return new MethodParameters(nameIndex, length, dataInput, constantPool);
184        case Const.ATTR_MODULE:
185            return new Module(nameIndex, length, dataInput, constantPool);
186        case Const.ATTR_MODULE_PACKAGES:
187            return new ModulePackages(nameIndex, length, dataInput, constantPool);
188        case Const.ATTR_MODULE_MAIN_CLASS:
189            return new ModuleMainClass(nameIndex, length, dataInput, constantPool);
190        case Const.ATTR_NEST_HOST:
191            return new NestHost(nameIndex, length, dataInput, constantPool);
192        case Const.ATTR_NEST_MEMBERS:
193            return new NestMembers(nameIndex, length, dataInput, constantPool);
194        default:
195            // Never reached
196            throw new IllegalStateException("Unrecognized attribute type tag parsed: " + tag);
197        }
198    }
199
200    /**
201     * Class method reads one attribute from the input data stream. This method must not be accessible from the outside. It
202     * is called by the Field and Method constructor methods.
203     *
204     * @see Field
205     * @see Method
206     *
207     * @param dataInputStream Input stream
208     * @param constantPool Array of constants
209     * @return Attribute
210     * @throws IOException if an I/O error occurs.
211     */
212    public static Attribute readAttribute(final DataInputStream dataInputStream, final ConstantPool constantPool) throws IOException {
213        return readAttribute((DataInput) dataInputStream, constantPool);
214    }
215
216    /**
217     * Remove attribute reader
218     *
219     * @param name the name of the attribute as stored in the class file
220     */
221    public static void removeAttributeReader(final String name) {
222        READERS.remove(name);
223    }
224
225    /**
226     * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
227     */
228    @java.lang.Deprecated
229    protected int name_index; // Points to attribute name in constant pool TODO make private (has getter & setter)
230
231    /**
232     * @deprecated (since 6.0) (since 6.0) will be made private; do not access directly, use getter/setter
233     */
234    @java.lang.Deprecated
235    protected int length; // Content length of attribute field TODO make private (has getter & setter)
236
237    /**
238     * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
239     */
240    @java.lang.Deprecated
241    protected byte tag; // Tag to distinguish subclasses TODO make private & final; supposed to be immutable
242
243    /**
244     * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
245     */
246    @java.lang.Deprecated
247    protected ConstantPool constant_pool; // TODO make private (has getter & setter)
248
249    /**
250     * Constructs an instance.
251     *
252     * <pre>
253     * attribute_info {
254     *   u2 attribute_name_index;
255     *   u4 attribute_length;
256     *   u1 info[attribute_length];
257     * }
258     * </pre>
259     *
260     * @param tag tag.
261     * @param nameIndex u2 name index.
262     * @param length u4 length.
263     * @param constantPool constant pool.
264     */
265    protected Attribute(final byte tag, final int nameIndex, final int length, final ConstantPool constantPool) {
266        this.tag = tag;
267        this.name_index = Args.requireU2(nameIndex, 0, constantPool.getLength(), getClass().getSimpleName() + " name index");
268        this.length = Args.requireU4(length, getClass().getSimpleName() + " attribute length");
269        this.constant_pool = constantPool;
270    }
271
272    /**
273     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
274     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
275     *
276     * @param v Visitor object
277     */
278    @Override
279    public abstract void accept(Visitor v);
280
281    /**
282     * Use copy() if you want to have a deep copy(), i.e., with all references copied correctly.
283     *
284     * @return shallow copy of this attribute
285     */
286    @Override
287    public Object clone() {
288        Attribute attr = null;
289        try {
290            attr = (Attribute) super.clone();
291        } catch (final CloneNotSupportedException e) {
292            throw new UnsupportedOperationException("Clone Not Supported", e); // never happens
293        }
294        return attr;
295    }
296
297    /**
298     * @param constantPool constant pool to save.
299     * @return deep copy of this attribute.
300     */
301    public abstract Attribute copy(ConstantPool constantPool);
302
303    /**
304     * Dumps attribute to file stream in binary format.
305     *
306     * @param file Output file stream
307     * @throws IOException if an I/O error occurs.
308     */
309    public void dump(final DataOutputStream file) throws IOException {
310        file.writeShort(name_index);
311        file.writeInt(length);
312    }
313
314    /**
315     * @return Constant pool used by this object.
316     * @see ConstantPool
317     */
318    public final ConstantPool getConstantPool() {
319        return constant_pool;
320    }
321
322    /**
323     * @return Length of attribute field in bytes.
324     */
325    public final int getLength() {
326        return length;
327    }
328
329    /**
330     * @return Name of attribute
331     * @since 6.0
332     */
333    public String getName() {
334        return constant_pool.getConstantUtf8(name_index).getBytes();
335    }
336
337    /**
338     * @return Name index in constant pool of attribute name.
339     */
340    public final int getNameIndex() {
341        return name_index;
342    }
343
344    /**
345     * @return Tag of attribute, i.e., its type. Value may not be altered, thus there is no setTag() method.
346     */
347    public final byte getTag() {
348        return tag;
349    }
350
351    /**
352     * @param constantPool Constant pool to be used for this object.
353     * @see ConstantPool
354     */
355    public final void setConstantPool(final ConstantPool constantPool) {
356        this.constant_pool = constantPool;
357    }
358
359    /**
360     * @param length length in bytes.
361     */
362    public final void setLength(final int length) {
363        this.length = length;
364    }
365
366    /**
367     * @param nameIndex of attribute.
368     */
369    public final void setNameIndex(final int nameIndex) {
370        this.name_index = nameIndex;
371    }
372
373    /**
374     * @return attribute name.
375     */
376    @Override
377    public String toString() {
378        return Const.getAttributeName(tag);
379    }
380}