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