    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}