/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
package org.mozilla.javascript;
import java.io.Serializable;
/**
* Class instances represent serializable tags to mark special Object values.
* <p>
* Compatibility note: under jdk 1.1 use
* org.mozilla.javascript.serialize.ScriptableInputStream to read serialized
* instances of UniqueTag as under this JDK version the default
* ObjectInputStream would not restore them correctly as it lacks support
* for readResolve method
*/
public final class UniqueTag implements Serializable
{
static final long serialVersionUID = -4320556826714577259L;
private static final int ID_NOT_FOUND = 1;
private static final int ID_NULL_VALUE = 2;
private static final int ID_DOUBLE_MARK = 3;
/**
* Tag to mark non-existing values.
*/
public static final UniqueTag
NOT_FOUND = new UniqueTag(ID_NOT_FOUND);
/**
* Tag to distinguish between uninitialized and null values.
*/
public static final UniqueTag
NULL_VALUE = new UniqueTag(ID_NULL_VALUE);
/**
* Tag to indicate that a object represents "double" with the real value
* stored somewhere else.
*/
public static final UniqueTag
DOUBLE_MARK = new UniqueTag(ID_DOUBLE_MARK);
private final int tagId;
private UniqueTag(int tagId)
{
this.tagId = tagId;
}
public Object readResolve()
{
switch (tagId) {
case ID_NOT_FOUND:
return NOT_FOUND;
case ID_NULL_VALUE:
return NULL_VALUE;
case ID_DOUBLE_MARK:
return DOUBLE_MARK;
}
throw new IllegalStateException(String.valueOf(tagId));
}
// Overridden for better debug printouts
@Override
public String toString()
{
String name;
switch (tagId) {
case ID_NOT_FOUND:
name = "NOT_FOUND";
break;
case ID_NULL_VALUE:
name = "NULL_VALUE";
break;
case ID_DOUBLE_MARK:
name = "DOUBLE_MARK";
break;
default:
throw Kit.codeBug();
}
return super.toString()+": "+name;
}
}