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	/*
	* Copyright (c) 2017, 2021, Oracle and/or its affiliates. All rights reserved.
	*/
	/*
	* Licensed to the Apache Software Foundation (ASF) under one or more
	* contributor license agreements. See the NOTICE file distributed with
	* this work for additional information regarding copyright ownership.
	* The ASF licenses this file to You under the Apache License, Version 2.0
	* (the "License"); you may not use this file except in compliance with
	* the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	package com.sun.org.apache.bcel.internal.classfile;

	import java.io.DataInput;
	import java.io.DataInputStream;
	import java.io.DataOutputStream;
	import java.io.IOException;
	import java.util.HashMap;
	import java.util.Map;

	import com.sun.org.apache.bcel.internal.Const;

	/**
	* Abstract super class for <em>Attribute</em> objects. Currently the
	* <em>ConstantValue</em>, <em>SourceFile</em>, <em>Code</em>,
	* <em>Exceptiontable</em>, <em>LineNumberTable</em>,
	* <em>LocalVariableTable</em>, <em>InnerClasses</em> and
	* <em>Synthetic</em> attributes are supported. The <em>Unknown</em>
	* attribute stands for non-standard-attributes.
	*
	* @see ConstantValue
	* @see SourceFile
	* @see Code
	* @see Unknown
	* @see ExceptionTable
	* @see LineNumberTable
	* @see LocalVariableTable
	* @see InnerClasses
	* @see Synthetic
	* @see Deprecated
	* @see Signature
	* @LastModified: May 2021
	*/
	public abstract class Attribute implements Cloneable, Node {
	private static final boolean debug = false;
	private int name_index; // Points to attribute name in constant pool
	private int length; // Content length of attribute field
	private final byte tag; // Tag to distinguish subclasses
	private ConstantPool constant_pool;

	private static final Map<String, Object> readers = new HashMap<>();

	/**
	* Add an Attribute reader capable of parsing (user-defined) attributes
	* named "name". You should not add readers for the standard attributes such
	* as "LineNumberTable", because those are handled internally.
	*
	* @param name the name of the attribute as stored in the class file
	* @param r the reader object
	*/
	public static void addAttributeReader(final String name, final UnknownAttributeReader r)
	{
	readers.put(name, r);
	}

	protected static void println(final String msg) {
	if (debug) {
	System.err.println(msg);
	}
	}

	/**
	* Class method reads one attribute from the input data stream. This method
	* must not be accessible from the outside. It is called by the Field and
	* Method constructor methods.
	*
	* @see Field
	* @see Method
	*
	* @param file Input stream
	* @param constant_pool Array of constants
	* @return Attribute
	* @throws IOException
	* @throws ClassFormatException
	* @since 6.0
	*/
	public static Attribute readAttribute(final DataInput file, final ConstantPool constant_pool)
	throws IOException, ClassFormatException
	{
	byte tag = Const.ATTR_UNKNOWN; // Unknown attribute
	// Get class name from constant pool via `name_index' indirection
	final int name_index = file.readUnsignedShort();
	final ConstantUtf8 c = (ConstantUtf8) constant_pool.getConstant(name_index, Const.CONSTANT_Utf8);
	final String name = c.getBytes();

	// Length of data in bytes
	final int length = file.readInt();

	// Compare strings to find known attribute
	for (byte i = 0; i < Const.KNOWN_ATTRIBUTES; i++)
	{
	if (name.equals(Const.getAttributeName(i)))
	{
	tag = i; // found!
	break;
	}
	}

	// Call proper constructor, depending on `tag'
	switch (tag)
	{
	case Const.ATTR_UNKNOWN:
	final Object r = readers.get(name);
	if (r instanceof UnknownAttributeReader)
	{
	return ((UnknownAttributeReader) r).createAttribute(name_index, length, file, constant_pool);
	}
	return new Unknown(name_index, length, file, constant_pool);
	case Const.ATTR_CONSTANT_VALUE:
	return new ConstantValue(name_index, length, file, constant_pool);
	case Const.ATTR_SOURCE_FILE:
	return new SourceFile(name_index, length, file, constant_pool);
	case Const.ATTR_CODE:
	return new Code(name_index, length, file, constant_pool);
	case Const.ATTR_EXCEPTIONS:
	return new ExceptionTable(name_index, length, file, constant_pool);
	case Const.ATTR_LINE_NUMBER_TABLE:
	return new LineNumberTable(name_index, length, file, constant_pool);
	case Const.ATTR_LOCAL_VARIABLE_TABLE:
	return new LocalVariableTable(name_index, length, file, constant_pool);
	case Const.ATTR_INNER_CLASSES:
	return new InnerClasses(name_index, length, file, constant_pool);
	case Const.ATTR_SYNTHETIC:
	return new Synthetic(name_index, length, file, constant_pool);
	case Const.ATTR_DEPRECATED:
	return new Deprecated(name_index, length, file, constant_pool);
	case Const.ATTR_PMG:
	return new PMGClass(name_index, length, file, constant_pool);
	case Const.ATTR_SIGNATURE:
	return new Signature(name_index, length, file, constant_pool);
	case Const.ATTR_STACK_MAP:
	// old style stack map: unneeded for JDK5 and below;
	// illegal(?) for JDK6 and above. So just delete with a warning.
	println("Warning: Obsolete StackMap attribute ignored.");
	return new Unknown(name_index, length, file, constant_pool);
	case Const.ATTR_RUNTIME_VISIBLE_ANNOTATIONS:
	return new RuntimeVisibleAnnotations(name_index, length, file, constant_pool);
	case Const.ATTR_RUNTIME_INVISIBLE_ANNOTATIONS:
	return new RuntimeInvisibleAnnotations(name_index, length, file, constant_pool);
	case Const.ATTR_RUNTIME_VISIBLE_PARAMETER_ANNOTATIONS:
	return new RuntimeVisibleParameterAnnotations(name_index, length, file, constant_pool);
	case Const.ATTR_RUNTIME_INVISIBLE_PARAMETER_ANNOTATIONS:
	return new RuntimeInvisibleParameterAnnotations(name_index, length, file, constant_pool);
	case Const.ATTR_ANNOTATION_DEFAULT:
	return new AnnotationDefault(name_index, length, file, constant_pool);
	case Const.ATTR_LOCAL_VARIABLE_TYPE_TABLE:
	return new LocalVariableTypeTable(name_index, length, file, constant_pool);
	case Const.ATTR_ENCLOSING_METHOD:
	return new EnclosingMethod(name_index, length, file, constant_pool);
	case Const.ATTR_STACK_MAP_TABLE:
	// read new style stack map: StackMapTable. The rest of the code
	// calls this a StackMap for historical reasons.
	return new StackMap(name_index, length, file, constant_pool);
	case Const.ATTR_BOOTSTRAP_METHODS:
	return new BootstrapMethods(name_index, length, file, constant_pool);
	case Const.ATTR_METHOD_PARAMETERS:
	return new MethodParameters(name_index, length, file, constant_pool);
	case Const.ATTR_MODULE:
	return new Module(name_index, length, file, constant_pool);
	case Const.ATTR_MODULE_PACKAGES:
	return new ModulePackages(name_index, length, file, constant_pool);
	case Const.ATTR_MODULE_MAIN_CLASS:
	return new ModuleMainClass(name_index, length, file, constant_pool);
	case Const.ATTR_NEST_HOST:
	return new NestHost(name_index, length, file, constant_pool);
	case Const.ATTR_NEST_MEMBERS:
	return new NestMembers(name_index, length, file, constant_pool);
	default:
	// Never reached
	throw new IllegalStateException("Unrecognized attribute type tag parsed: " + tag);
	}
	}

	/**
	* Class method reads one attribute from the input data stream. This method
	* must not be accessible from the outside. It is called by the Field and
	* Method constructor methods.
	*
	* @see Field
	* @see Method
	*
	* @param file Input stream
	* @param constant_pool Array of constants
	* @return Attribute
	* @throws IOException
	* @throws ClassFormatException
	*/
	public static Attribute readAttribute(final DataInputStream file, final ConstantPool constant_pool)
	throws IOException, ClassFormatException
	{
	return readAttribute((DataInput) file, constant_pool);
	}

	/**
	* Remove attribute reader
	*
	* @param name the name of the attribute as stored in the class file
	*/
	public static void removeAttributeReader(final String name)
	{
	readers.remove(name);
	}

	protected Attribute(final byte tag, final int name_index, final int length, final ConstantPool constant_pool)
	{
	this.tag = tag;
	this.name_index = name_index;
	this.length = length;
	this.constant_pool = constant_pool;
	}

	/**
	* Called by objects that are traversing the nodes of the tree implicitely
	* defined by the contents of a Java class. I.e., the hierarchy of methods,
	* fields, attributes, etc. spawns a tree of objects.
	*
	* @param v
	* Visitor object
	*/
	@Override
	public abstract void accept(Visitor v);

	/**
	* Use copy() if you want to have a deep copy(), i.e., with all references
	* copied correctly.
	*
	* @return shallow copy of this attribute
	*/
	@Override
	public Object clone()
	{
	Attribute attr = null;
	try
	{
	attr = (Attribute) super.clone();
	}
	catch (final CloneNotSupportedException e)
	{
	throw new Error("Clone Not Supported"); // never happens
	}
	return attr;
	}

	/**
	* @return deep copy of this attribute
	*/
	public abstract Attribute copy(ConstantPool _constant_pool);

	/**
	* Dump attribute to file stream in binary format.
	*
	* @param file
	* Output file stream
	* @throws IOException
	*/
	public void dump(final DataOutputStream file) throws IOException
	{
	file.writeShort(name_index);
	file.writeInt(length);
	}

	/**
	* @return Constant pool used by this object.
	* @see ConstantPool
	*/
	public final ConstantPool getConstantPool()
	{
	return constant_pool;
	}

	/**
	* @return Length of attribute field in bytes.
	*/
	public final int getLength()
	{
	return length;
	}

	/**
	* @return Name of attribute
	* @since 6.0
	*/
	public String getName()
	{
	final ConstantUtf8 c = (ConstantUtf8) constant_pool.getConstant(name_index, Const.CONSTANT_Utf8);
	return c.getBytes();
	}

	/**
	* @return Name index in constant pool of attribute name.
	*/
	public final int getNameIndex()
	{
	return name_index;
	}

	/**
	* @return Tag of attribute, i.e., its type. Value may not be altered, thus there is no setTag() method.
	*/
	public final byte getTag()
	{
	return tag;
	}

	/**
	* @param constant_pool Constant pool to be used for this object.
	* @see ConstantPool
	*/
	public final void setConstantPool(final ConstantPool constant_pool)
	{
	this.constant_pool = constant_pool;
	}

	/**
	* @param length length in bytes.
	*/
	public final void setLength(final int length)
	{
	this.length = length;
	}

	/**
	* @param name_index of attribute.
	*/
	public final void setNameIndex(final int name_index)
	{
	this.name_index = name_index;
	}

	/**
	* @return attribute name.
	*/
	@Override
	public String toString()
	{
	return Const.getAttributeName(tag);
	}
	}

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