Source code

001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   https://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.bcel.classfile;
020
021import java.io.DataInput;
022import java.io.DataInputStream;
023import java.io.DataOutputStream;
024import java.io.IOException;
025import java.util.HashMap;
026import java.util.Map;
027
028import org.apache.bcel.Const;
029import org.apache.bcel.util.Args;
030
031/**
032 * Abstract super class for <em>Attribute</em> objects. Currently the <em>ConstantValue</em>, <em>SourceFile</em>, <em>Code</em>, <em>Exceptiontable</em>,
033 * <em>LineNumberTable</em>, <em>LocalVariableTable</em>, <em>InnerClasses</em> and <em>Synthetic</em> attributes are supported. The <em>Unknown</em> attribute
034 * stands for non-standard-attributes.
035 *
036 * <pre>
037 * attribute_info {
038 *   u2 attribute_name_index;
039 *   u4 attribute_length;
040 *   u1 info[attribute_length];
041 * }
042 * </pre>
043 *
044 * @see ConstantValue
045 * @see SourceFile
046 * @see Code
047 * @see Unknown
048 * @see ExceptionTable
049 * @see LineNumberTable
050 * @see LocalVariableTable
051 * @see InnerClasses
052 * @see Synthetic
053 * @see Deprecated
054 * @see Signature
055 */
056public abstract class Attribute implements Cloneable, Node {
057
058    private static final boolean debug = Boolean.getBoolean(Attribute.class.getCanonicalName() + ".debug"); // Debugging on/off
059
060    private static final Map<String, Object> READERS = new HashMap<>();
061
062    /**
063     * Empty array.
064     *
065     * @since 6.6.0
066     */
067    public static final Attribute[] EMPTY_ARRAY = {};
068
069    /**
070     * Add an Attribute reader capable of parsing (user-defined) attributes named "name". You should not add readers for the
071     * standard attributes such as "LineNumberTable", because those are handled internally.
072     *
073     * @param name the name of the attribute as stored in the class file
074     * @param attributeReader the reader object
075     * @deprecated (6.0) Use {@link #addAttributeReader(String, UnknownAttributeReader)} instead
076     */
077    @java.lang.Deprecated
078    public static void addAttributeReader(final String name, final AttributeReader attributeReader) {
079        READERS.put(name, attributeReader);
080    }
081
082    /**
083     * Add an Attribute reader capable of parsing (user-defined) attributes named "name". You should not add readers for the
084     * standard attributes such as "LineNumberTable", because those are handled internally.
085     *
086     * @param name the name of the attribute as stored in the class file
087     * @param unknownAttributeReader the reader object
088     */
089    public static void addAttributeReader(final String name, final UnknownAttributeReader unknownAttributeReader) {
090        READERS.put(name, unknownAttributeReader);
091    }
092
093    protected static void println(final String msg) {
094        if (debug) {
095            System.err.println(msg);
096        }
097    }
098
099    /**
100     * Class method reads one attribute from the input data stream. This method must not be accessible from the outside. It
101     * is called by the Field and Method constructor methods.
102     *
103     * @see Field
104     * @see Method
105     * @param dataInput Input stream
106     * @param constantPool Array of constants
107     * @return Attribute
108     * @throws IOException if an I/O error occurs.
109     * @since 6.0
110     */
111    public static Attribute readAttribute(final DataInput dataInput, final ConstantPool constantPool) throws IOException {
112        byte tag = Const.ATTR_UNKNOWN; // Unknown attribute
113        // Get class name from constant pool via 'name_index' indirection
114        final int nameIndex = dataInput.readUnsignedShort();
115        final String name = constantPool.getConstantUtf8(nameIndex).getBytes();
116
117        // Length of data in bytes
118        final int length = dataInput.readInt();
119
120        // Compare strings to find known attribute
121        for (byte i = 0; i < Const.KNOWN_ATTRIBUTES; i++) {
122            if (name.equals(Const.getAttributeName(i))) {
123                tag = i; // found!
124                break;
125            }
126        }
127
128        // Call proper constructor, depending on 'tag'
129        switch (tag) {
130        case Const.ATTR_UNKNOWN:
131            final Object r = READERS.get(name);
132            if (r instanceof UnknownAttributeReader) {
133                return ((UnknownAttributeReader) r).createAttribute(nameIndex, length, dataInput, constantPool);
134            }
135            return new Unknown(nameIndex, length, dataInput, constantPool);
136        case Const.ATTR_CONSTANT_VALUE:
137            return new ConstantValue(nameIndex, length, dataInput, constantPool);
138        case Const.ATTR_SOURCE_FILE:
139            return new SourceFile(nameIndex, length, dataInput, constantPool);
140        case Const.ATTR_CODE:
141            return new Code(nameIndex, length, dataInput, constantPool);
142        case Const.ATTR_EXCEPTIONS:
143            return new ExceptionTable(nameIndex, length, dataInput, constantPool);
144        case Const.ATTR_LINE_NUMBER_TABLE:
145            return new LineNumberTable(nameIndex, length, dataInput, constantPool);
146        case Const.ATTR_LOCAL_VARIABLE_TABLE:
147            return new LocalVariableTable(nameIndex, length, dataInput, constantPool);
148        case Const.ATTR_INNER_CLASSES:
149            return new InnerClasses(nameIndex, length, dataInput, constantPool);
150        case Const.ATTR_SYNTHETIC:
151            return new Synthetic(nameIndex, length, dataInput, constantPool);
152        case Const.ATTR_DEPRECATED:
153            return new Deprecated(nameIndex, length, dataInput, constantPool);
154        case Const.ATTR_PMG:
155            return new PMGClass(nameIndex, length, dataInput, constantPool);
156        case Const.ATTR_SIGNATURE:
157            return new Signature(nameIndex, length, dataInput, constantPool);
158        case Const.ATTR_STACK_MAP:
159            // old style stack map: unneeded for JDK5 and below;
160            // illegal(?) for JDK6 and above. So just delete with a warning.
161            println("Warning: Obsolete StackMap attribute ignored.");
162            return new Unknown(nameIndex, length, dataInput, constantPool);
163        case Const.ATTR_RUNTIME_VISIBLE_ANNOTATIONS:
164            return new RuntimeVisibleAnnotations(nameIndex, length, dataInput, constantPool);
165        case Const.ATTR_RUNTIME_INVISIBLE_ANNOTATIONS:
166            return new RuntimeInvisibleAnnotations(nameIndex, length, dataInput, constantPool);
167        case Const.ATTR_RUNTIME_VISIBLE_PARAMETER_ANNOTATIONS:
168            return new RuntimeVisibleParameterAnnotations(nameIndex, length, dataInput, constantPool);
169        case Const.ATTR_RUNTIME_INVISIBLE_PARAMETER_ANNOTATIONS:
170            return new RuntimeInvisibleParameterAnnotations(nameIndex, length, dataInput, constantPool);
171        case Const.ATTR_ANNOTATION_DEFAULT:
172            return new AnnotationDefault(nameIndex, length, dataInput, constantPool);
173        case Const.ATTR_LOCAL_VARIABLE_TYPE_TABLE:
174            return new LocalVariableTypeTable(nameIndex, length, dataInput, constantPool);
175        case Const.ATTR_ENCLOSING_METHOD:
176            return new EnclosingMethod(nameIndex, length, dataInput, constantPool);
177        case Const.ATTR_STACK_MAP_TABLE:
178            // read new style stack map: StackMapTable. The rest of the code
179            // calls this a StackMap for historical reasons.
180            return new StackMap(nameIndex, length, dataInput, constantPool);
181        case Const.ATTR_BOOTSTRAP_METHODS:
182            return new BootstrapMethods(nameIndex, length, dataInput, constantPool);
183        case Const.ATTR_METHOD_PARAMETERS:
184            return new MethodParameters(nameIndex, length, dataInput, constantPool);
185        case Const.ATTR_MODULE:
186            return new Module(nameIndex, length, dataInput, constantPool);
187        case Const.ATTR_MODULE_PACKAGES:
188            return new ModulePackages(nameIndex, length, dataInput, constantPool);
189        case Const.ATTR_MODULE_MAIN_CLASS:
190            return new ModuleMainClass(nameIndex, length, dataInput, constantPool);
191        case Const.ATTR_NEST_HOST:
192            return new NestHost(nameIndex, length, dataInput, constantPool);
193        case Const.ATTR_NEST_MEMBERS:
194            return new NestMembers(nameIndex, length, dataInput, constantPool);
195        case Const.ATTR_RECORD:
196            return new Record(nameIndex, length, dataInput, constantPool);
197        default:
198            // Never reached
199            throw new IllegalStateException("Unrecognized attribute type tag parsed: " + tag);
200        }
201    }
202
203    /**
204     * Class method reads one attribute from the input data stream. This method must not be accessible from the outside. It
205     * is called by the Field and Method constructor methods.
206     *
207     * @see Field
208     * @see Method
209     * @param dataInputStream Input stream
210     * @param constantPool Array of constants
211     * @return Attribute
212     * @throws IOException if an I/O error occurs.
213     */
214    public static Attribute readAttribute(final DataInputStream dataInputStream, final ConstantPool constantPool) throws IOException {
215        return readAttribute((DataInput) dataInputStream, constantPool);
216    }
217
218    /**
219     * Remove attribute reader
220     *
221     * @param name the name of the attribute as stored in the class file
222     */
223    public static void removeAttributeReader(final String name) {
224        READERS.remove(name);
225    }
226
227    /**
228     * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
229     */
230    @java.lang.Deprecated
231    protected int name_index; // Points to attribute name in constant pool TODO make private (has getter & setter)
232
233    /**
234     * @deprecated (since 6.0) (since 6.0) will be made private; do not access directly, use getter/setter
235     */
236    @java.lang.Deprecated
237    protected int length; // Content length of attribute field TODO make private (has getter & setter)
238
239    /**
240     * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
241     */
242    @java.lang.Deprecated
243    protected byte tag; // Tag to distinguish subclasses TODO make private & final; supposed to be immutable
244
245    /**
246     * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
247     */
248    @java.lang.Deprecated
249    protected ConstantPool constant_pool; // TODO make private (has getter & setter)
250
251    /**
252     * Constructs an instance.
253     *
254     * <pre>
255     * attribute_info {
256     *   u2 attribute_name_index;
257     *   u4 attribute_length;
258     *   u1 info[attribute_length];
259     * }
260     * </pre>
261     *
262     * @param tag tag.
263     * @param nameIndex u2 name index.
264     * @param length u4 length.
265     * @param constantPool constant pool.
266     */
267    protected Attribute(final byte tag, final int nameIndex, final int length, final ConstantPool constantPool) {
268        this.tag = tag;
269        this.name_index = Args.requireU2(nameIndex, 0, constantPool.getLength(), getClass().getSimpleName() + " name index");
270        this.length = Args.requireU4(length, getClass().getSimpleName() + " attribute length");
271        this.constant_pool = constantPool;
272    }
273
274    /**
275     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
276     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
277     *
278     * @param v Visitor object
279     */
280    @Override
281    public abstract void accept(Visitor v);
282
283    /**
284     * Use copy() if you want to have a deep copy(), i.e., with all references copied correctly.
285     *
286     * @return shallow copy of this attribute
287     */
288    @Override
289    public Object clone() {
290        Attribute attr = null;
291        try {
292            attr = (Attribute) super.clone();
293        } catch (final CloneNotSupportedException e) {
294            throw new UnsupportedOperationException("Clone Not Supported", e); // never happens
295        }
296        return attr;
297    }
298
299    /**
300     * @param constantPool constant pool to save.
301     * @return deep copy of this attribute.
302     */
303    public abstract Attribute copy(ConstantPool constantPool);
304
305    /**
306     * Dumps attribute to file stream in binary format.
307     *
308     * @param file Output file stream
309     * @throws IOException if an I/O error occurs.
310     */
311    public void dump(final DataOutputStream file) throws IOException {
312        file.writeShort(name_index);
313        file.writeInt(length);
314    }
315
316    /**
317     * @return Constant pool used by this object.
318     * @see ConstantPool
319     */
320    public final ConstantPool getConstantPool() {
321        return constant_pool;
322    }
323
324    /**
325     * @return Length of attribute field in bytes.
326     */
327    public final int getLength() {
328        return length;
329    }
330
331    /**
332     * @return Name of attribute
333     * @since 6.0
334     */
335    public String getName() {
336        return constant_pool.getConstantUtf8(name_index).getBytes();
337    }
338
339    /**
340     * @return Name index in constant pool of attribute name.
341     */
342    public final int getNameIndex() {
343        return name_index;
344    }
345
346    /**
347     * @return Tag of attribute, i.e., its type. Value may not be altered, thus there is no setTag() method.
348     */
349    public final byte getTag() {
350        return tag;
351    }
352
353    /**
354     * @param constantPool Constant pool to be used for this object.
355     * @see ConstantPool
356     */
357    public final void setConstantPool(final ConstantPool constantPool) {
358        this.constant_pool = constantPool;
359    }
360
361    /**
362     * @param length length in bytes.
363     */
364    public final void setLength(final int length) {
365        this.length = length;
366    }
367
368    /**
369     * @param nameIndex of attribute.
370     */
371    public final void setNameIndex(final int nameIndex) {
372        this.name_index = nameIndex;
373    }
374
375    /**
376     * @return attribute name.
377     */
378    @Override
379    public String toString() {
380        return Const.getAttributeName(tag);
381    }
382}