org.apache.tomcat.util.bcel.classfile.Constant Maven / Gradle / Ivy
/*
* 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.tomcat.util.bcel.classfile;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.Serializable;
import org.apache.tomcat.util.bcel.Constants;
import org.apache.tomcat.util.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: Constant.java 992409 2010-09-03 18:35:59Z markt $
* @author M. Dahm
*/
public abstract class Constant implements Cloneable, Serializable {
private static final long serialVersionUID = 2827409182154809454L;
private static BCELComparator _cmp = new BCELComparator() {
@Override
public boolean equals( Object o1, Object o2 ) {
Constant THIS = (Constant) o1;
Constant THAT = (Constant) o2;
return THIS.toString().equals(THAT.toString());
}
@Override
public int hashCode( Object o ) {
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.
*/
protected byte tag;
Constant(byte tag) {
this.tag = tag;
}
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 Constants.CONSTANT_NAMES[tag] + "[" + tag + "]";
}
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
/**
* Read one constant from the given file, the type depends on a tag byte.
*
* @param file Input stream
* @return Constant object
*/
static final Constant readConstant( DataInputStream file ) throws IOException,
ClassFormatException {
byte b = file.readByte(); // Read tag byte
switch (b) {
case Constants.CONSTANT_Class:
return new ConstantClass(file);
case Constants.CONSTANT_Fieldref:
return new ConstantFieldref(file);
case Constants.CONSTANT_Methodref:
return new ConstantMethodref(file);
case Constants.CONSTANT_InterfaceMethodref:
return new ConstantInterfaceMethodref(file);
case Constants.CONSTANT_String:
return new ConstantString(file);
case Constants.CONSTANT_Integer:
return new ConstantInteger(file);
case Constants.CONSTANT_Float:
return new ConstantFloat(file);
case Constants.CONSTANT_Long:
return new ConstantLong(file);
case Constants.CONSTANT_Double:
return new ConstantDouble(file);
case Constants.CONSTANT_NameAndType:
return new ConstantNameAndType(file);
case Constants.CONSTANT_Utf8:
return new ConstantUtf8(file);
default:
throw new ClassFormatException("Invalid byte tag in constant pool: " + b);
}
}
/**
* 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( Object obj ) {
return _cmp.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 _cmp.hashCode(this);
}
}