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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.DataOutputStream;
	import java.io.IOException;
	import java.util.Objects;

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

	/**
	* Abstract superclass for classes to represent the different constant types
	* in the constant pool of a class file. The classes keep closely to
	* the JVM specification.
	*
	* @LastModified: May 2021
	*/
	public abstract class Constant implements Cloneable, Node {

	private static BCELComparator bcelComparator = new BCELComparator() {

	@Override
	public boolean equals( final Object o1, final Object o2 ) {
	final Constant THIS = (Constant) o1;
	final Constant THAT = (Constant) o2;
	return Objects.equals(THIS.toString(), THAT.toString());
	}


	@Override
	public int hashCode( final Object o ) {
	final Constant THIS = (Constant) o;
	return THIS.toString().hashCode();
	}
	};

	/* In fact this tag is redundant since we can distinguish different
	* `Constant' objects by their type, i.e., via `instanceof'. In some
	* places we will use the tag for switch()es anyway.
	*
	* First, we want match the specification as closely as possible. Second we
	* need the tag as an index to select the corresponding class name from the
	* `CONSTANT_NAMES' array.
	*/
	private byte tag;

	Constant(final byte tag) {
	this.tag = tag;
	}

	/**
	* 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 );

	public abstract void dump( DataOutputStream file ) throws IOException;

	/**
	* @return Tag of constant, i.e., its type. No setTag() method to avoid
	* confusion.
	*/
	public final byte getTag() {
	return tag;
	}

	/**
	* @return String representation.
	*/
	@Override
	public String toString() {
	return Const.getConstantName(tag) + "[" + tag + "]";
	}

	/**
	* @return deep copy of this constant
	*/
	public Constant copy() {
	try {
	return (Constant) super.clone();
	} catch (final CloneNotSupportedException e) {
	// TODO should this throw?
	}
	return null;
	}

	@Override
	public Object clone() {
	try {
	return super.clone();
	} catch (final CloneNotSupportedException e) {
	throw new Error("Clone Not Supported"); // never happens
	}
	}

	/**
	* Reads one constant from the given input, the type depends on a tag byte.
	*
	* @param dataInput Input stream
	* @return Constant object
	* @throws IOException if an I/O error occurs reading from the given {@code dataInput}.
	* @throws ClassFormatException if the next byte is not recognized
	* @since 6.0 made public
	*/
	public static Constant readConstant(final DataInput dataInput) throws IOException, ClassFormatException {
	final byte b = dataInput.readByte(); // Read tag byte
	switch (b) {
	case Const.CONSTANT_Class:
	return new ConstantClass(dataInput);
	case Const.CONSTANT_Fieldref:
	return new ConstantFieldref(dataInput);
	case Const.CONSTANT_Methodref:
	return new ConstantMethodref(dataInput);
	case Const.CONSTANT_InterfaceMethodref:
	return new ConstantInterfaceMethodref(dataInput);
	case Const.CONSTANT_String:
	return new ConstantString(dataInput);
	case Const.CONSTANT_Integer:
	return new ConstantInteger(dataInput);
	case Const.CONSTANT_Float:
	return new ConstantFloat(dataInput);
	case Const.CONSTANT_Long:
	return new ConstantLong(dataInput);
	case Const.CONSTANT_Double:
	return new ConstantDouble(dataInput);
	case Const.CONSTANT_NameAndType:
	return new ConstantNameAndType(dataInput);
	case Const.CONSTANT_Utf8:
	return ConstantUtf8.getInstance(dataInput);
	case Const.CONSTANT_MethodHandle:
	return new ConstantMethodHandle(dataInput);
	case Const.CONSTANT_MethodType:
	return new ConstantMethodType(dataInput);
	case Const.CONSTANT_Dynamic:
	return new ConstantDynamic(dataInput);
	case Const.CONSTANT_InvokeDynamic:
	return new ConstantInvokeDynamic(dataInput);
	case Const.CONSTANT_Module:
	return new ConstantModule(dataInput);
	case Const.CONSTANT_Package:
	return new ConstantPackage(dataInput);
	default:
	throw new ClassFormatException("Invalid byte tag in constant pool: " + b);
	}
	}

	/**
	* @return Comparison strategy object
	*/
	public static BCELComparator getComparator() {
	return bcelComparator;
	}

	/**
	* @param comparator Comparison strategy object
	*/
	public static void setComparator( final BCELComparator comparator ) {
	bcelComparator = comparator;
	}

	/**
	* Returns value as defined by given BCELComparator strategy.
	* By default two Constant objects are said to be equal when
	* the result of toString() is equal.
	*
	* @see java.lang.Object#equals(java.lang.Object)
	*/
	@Override
	public boolean equals( final Object obj ) {
	return bcelComparator.equals(this, obj);
	}

	/**
	* Returns value as defined by given BCELComparator strategy.
	* By default return the hashcode of the result of toString().
	*
	* @see java.lang.Object#hashCode()
	*/
	@Override
	public int hashCode() {
	return bcelComparator.hashCode(this);
	}
	}

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