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/*
* 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 org.apache.bcel.classfile;
import java.io.DataInput;
import java.io.DataOutputStream;
import java.io.IOException;
import org.apache.bcel.Const;
import org.apache.bcel.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.
*
* @version $Id$
*/
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 THIS.toString().equals(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.
*/
/**
* @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
*/
@java.lang.Deprecated
protected byte tag; // TODO should be private & final
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
}
}
/**
* Read one constant from the given input, the type depends on a tag byte.
*
* @param input Input stream
* @return Constant object
* @since 6.0 made public
*/
public static Constant readConstant( final DataInput input ) throws IOException,
ClassFormatException {
final byte b = input.readByte(); // Read tag byte
switch (b) {
case Const.CONSTANT_Class:
return new ConstantClass(input);
case Const.CONSTANT_Fieldref:
return new ConstantFieldref(input);
case Const.CONSTANT_Methodref:
return new ConstantMethodref(input);
case Const.CONSTANT_InterfaceMethodref:
return new ConstantInterfaceMethodref(input);
case Const.CONSTANT_String:
return new ConstantString(input);
case Const.CONSTANT_Integer:
return new ConstantInteger(input);
case Const.CONSTANT_Float:
return new ConstantFloat(input);
case Const.CONSTANT_Long:
return new ConstantLong(input);
case Const.CONSTANT_Double:
return new ConstantDouble(input);
case Const.CONSTANT_NameAndType:
return new ConstantNameAndType(input);
case Const.CONSTANT_Utf8:
return ConstantUtf8.getInstance(input);
case Const.CONSTANT_MethodHandle:
return new ConstantMethodHandle(input);
case Const.CONSTANT_MethodType:
return new ConstantMethodType(input);
case Const.CONSTANT_InvokeDynamic:
return new ConstantInvokeDynamic(input);
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;
}
/**
* Return 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);
}
/**
* Return 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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