/*
* reserved comment block
* DO NOT REMOVE OR ALTER!
*/
package com.sun.org.apache.bcel.internal.classfile;
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*
* This software consists of voluntary contributions made by many
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import com.sun.org.apache.bcel.internal.Constants;
import java.io.*;
/**
* 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,v 1.1.2.1 2005/07/31 23:46:35 jeffsuttor Exp $
* @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
*/
public abstract class Constant implements Cloneable, Node, Serializable {
/* 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; }
/**
* 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
*/
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.
*/
public String toString() {
return Constants.CONSTANT_NAMES[tag] + "[" + tag + "]";
}
/**
* @return deep copy of this constant
*/
public Constant copy() {
try {
return (Constant)super.clone();
} catch(CloneNotSupportedException e) {}
return null;
}
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);
}
}
}