/*

  * Copyright (c) 1999, 2010, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  */

 package org.apidesign.bck2brwsr.emul.reflect;

 import java.io.ByteArrayOutputStream;

 import java.io.DataOutputStream;

 import java.io.IOException;

 import java.io.OutputStream;

 import java.lang.ref.Reference;

 import java.lang.ref.WeakReference;

 import java.lang.reflect.Array;

 import java.lang.reflect.Constructor;

 import java.lang.reflect.InvocationHandler;

 import java.lang.reflect.InvocationTargetException;

 import java.lang.reflect.Method;

 import java.lang.reflect.Modifier;

 import java.util.ArrayList;

 import java.util.Arrays;

 import java.util.Collections;

 import java.util.HashMap;

 import java.util.HashSet;

 import java.util.LinkedList;

 import java.util.Map;

 import java.util.Set;

 import java.util.List;

 import java.util.ListIterator;

 import java.util.WeakHashMap;

 import org.apidesign.bck2brwsr.core.Exported;

 import org.apidesign.bck2brwsr.core.JavaScriptBody;

 import org.apidesign.bck2brwsr.emul.reflect.MethodImpl;

 /**

  * {@code Proxy} provides static methods for creating dynamic proxy

  * classes and instances, and it is also the superclass of all

  * dynamic proxy classes created by those methods.

  *

  * <p>To create a proxy for some interface {@code Foo}:

  * <pre>

  *     InvocationHandler handler = new MyInvocationHandler(...);

  *     Class proxyClass = Proxy.getProxyClass(

  *         Foo.class.getClassLoader(), new Class[] { Foo.class });

  *     Foo f = (Foo) proxyClass.

  *         getConstructor(new Class[] { InvocationHandler.class }).

  *         newInstance(new Object[] { handler });

  * </pre>

  * or more simply:

  * <pre>

  *     Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(),

  *                                          new Class[] { Foo.class },

  *                                          handler);

  * </pre>

  *

  * <p>A <i>dynamic proxy class</i> (simply referred to as a <i>proxy

  * class</i> below) is a class that implements a list of interfaces

  * specified at runtime when the class is created, with behavior as

  * described below.

  *

  * A <i>proxy interface</i> is such an interface that is implemented

  * by a proxy class.

  *

  * A <i>proxy instance</i> is an instance of a proxy class.

  *

  * Each proxy instance has an associated <i>invocation handler</i>

  * object, which implements the interface {@link InvocationHandler}.

  * A method invocation on a proxy instance through one of its proxy

  * interfaces will be dispatched to the {@link InvocationHandler#invoke

  * invoke} method of the instance's invocation handler, passing the proxy

  * instance, a {@code java.lang.reflect.Method} object identifying

  * the method that was invoked, and an array of type {@code Object}

  * containing the arguments.  The invocation handler processes the

  * encoded method invocation as appropriate and the result that it

  * returns will be returned as the result of the method invocation on

  * the proxy instance.

  *

  * <p>A proxy class has the following properties:

  *

  * <ul>

  * <li>Proxy classes are public, final, and not abstract.

  *

  * <li>The unqualified name of a proxy class is unspecified.  The space

  * of class names that begin with the string {@code "$Proxy"}

  * should be, however, reserved for proxy classes.

  *

  * <li>A proxy class extends {@code java.lang.reflect.Proxy}.

  *

  * <li>A proxy class implements exactly the interfaces specified at its

  * creation, in the same order.

  *

  * <li>If a proxy class implements a non-public interface, then it will

  * be defined in the same package as that interface.  Otherwise, the

  * package of a proxy class is also unspecified.  Note that package

  * sealing will not prevent a proxy class from being successfully defined

  * in a particular package at runtime, and neither will classes already

  * defined by the same class loader and the same package with particular

  * signers.

  *

  * <li>Since a proxy class implements all of the interfaces specified at

  * its creation, invoking {@code getInterfaces} on its

  * {@code Class} object will return an array containing the same

  * list of interfaces (in the order specified at its creation), invoking

  * {@code getMethods} on its {@code Class} object will return

  * an array of {@code Method} objects that include all of the

  * methods in those interfaces, and invoking {@code getMethod} will

  * find methods in the proxy interfaces as would be expected.

  *

  * <li>The {@link Proxy#isProxyClass Proxy.isProxyClass} method will

  * return true if it is passed a proxy class-- a class returned by

  * {@code Proxy.getProxyClass} or the class of an object returned by

  * {@code Proxy.newProxyInstance}-- and false otherwise.

  *

  * <li>The {@code java.security.ProtectionDomain} of a proxy class

  * is the same as that of system classes loaded by the bootstrap class

  * loader, such as {@code java.lang.Object}, because the code for a

  * proxy class is generated by trusted system code.  This protection

  * domain will typically be granted

  * {@code java.security.AllPermission}.

  *

  * <li>Each proxy class has one public constructor that takes one argument,

  * an implementation of the interface {@link InvocationHandler}, to set

  * the invocation handler for a proxy instance.  Rather than having to use

  * the reflection API to access the public constructor, a proxy instance

  * can be also be created by calling the {@link Proxy#newProxyInstance

  * Proxy.newProxyInstance} method, which combines the actions of calling

  * {@link Proxy#getProxyClass Proxy.getProxyClass} with invoking the

  * constructor with an invocation handler.

  * </ul>

  *

  * <p>A proxy instance has the following properties:

  *

  * <ul>

  * <li>Given a proxy instance {@code proxy} and one of the

  * interfaces implemented by its proxy class {@code Foo}, the

  * following expression will return true:

  * <pre>

  *     {@code proxy instanceof Foo}

  * </pre>

  * and the following cast operation will succeed (rather than throwing

  * a {@code ClassCastException}):

  * <pre>

  *     {@code (Foo) proxy}

  * </pre>

  *

  * <li>Each proxy instance has an associated invocation handler, the one

  * that was passed to its constructor.  The static

  * {@link Proxy#getInvocationHandler Proxy.getInvocationHandler} method

  * will return the invocation handler associated with the proxy instance

  * passed as its argument.

  *

  * <li>An interface method invocation on a proxy instance will be

  * encoded and dispatched to the invocation handler's {@link

  * InvocationHandler#invoke invoke} method as described in the

  * documentation for that method.

  *

  * <li>An invocation of the {@code hashCode},

  * {@code equals}, or {@code toString} methods declared in

  * {@code java.lang.Object} on a proxy instance will be encoded and

  * dispatched to the invocation handler's {@code invoke} method in

  * the same manner as interface method invocations are encoded and

  * dispatched, as described above.  The declaring class of the

  * {@code Method} object passed to {@code invoke} will be

  * {@code java.lang.Object}.  Other public methods of a proxy

  * instance inherited from {@code java.lang.Object} are not

  * overridden by a proxy class, so invocations of those methods behave

  * like they do for instances of {@code java.lang.Object}.

  * </ul>

  *

  * <h3>Methods Duplicated in Multiple Proxy Interfaces</h3>

  *

  * <p>When two or more interfaces of a proxy class contain a method with

  * the same name and parameter signature, the order of the proxy class's

  * interfaces becomes significant.  When such a <i>duplicate method</i>

  * is invoked on a proxy instance, the {@code Method} object passed

  * to the invocation handler will not necessarily be the one whose

  * declaring class is assignable from the reference type of the interface

  * that the proxy's method was invoked through.  This limitation exists

  * because the corresponding method implementation in the generated proxy

  * class cannot determine which interface it was invoked through.

  * Therefore, when a duplicate method is invoked on a proxy instance,

  * the {@code Method} object for the method in the foremost interface

  * that contains the method (either directly or inherited through a

  * superinterface) in the proxy class's list of interfaces is passed to

  * the invocation handler's {@code invoke} method, regardless of the

  * reference type through which the method invocation occurred.

  *

  * <p>If a proxy interface contains a method with the same name and

  * parameter signature as the {@code hashCode}, {@code equals},

  * or {@code toString} methods of {@code java.lang.Object},

  * when such a method is invoked on a proxy instance, the

  * {@code Method} object passed to the invocation handler will have

  * {@code java.lang.Object} as its declaring class.  In other words,

  * the public, non-final methods of {@code java.lang.Object}

  * logically precede all of the proxy interfaces for the determination of

  * which {@code Method} object to pass to the invocation handler.

  *

  * <p>Note also that when a duplicate method is dispatched to an

  * invocation handler, the {@code invoke} method may only throw

  * checked exception types that are assignable to one of the exception

  * types in the {@code throws} clause of the method in <i>all</i> of

  * the proxy interfaces that it can be invoked through.  If the

  * {@code invoke} method throws a checked exception that is not

  * assignable to any of the exception types declared by the method in one

  * of the proxy interfaces that it can be invoked through, then an

  * unchecked {@code UndeclaredThrowableException} will be thrown by

  * the invocation on the proxy instance.  This restriction means that not

  * all of the exception types returned by invoking

  * {@code getExceptionTypes} on the {@code Method} object

  * passed to the {@code invoke} method can necessarily be thrown

  * successfully by the {@code invoke} method.

  *

  * @author      Peter Jones

  * @see         InvocationHandler

  * @since       1.3

  */

 @Exported

 public final class ProxyImpl implements java.io.Serializable {

     private static final long serialVersionUID = -2222568056686623797L;

     /** prefix for all proxy class names */

     private final static String proxyClassNamePrefix = "$Proxy";

     /** parameter types of a proxy class constructor */

     private final static Class[] constructorParams =

         { InvocationHandler.class };

     /** maps a class loader to the proxy class cache for that loader */

     private static Map<ClassLoader, Map<List<String>, Object>> loaderToCache

         = new WeakHashMap<>();

     /** marks that a particular proxy class is currently being generated */

     private static Object pendingGenerationMarker = new Object();

     /** next number to use for generation of unique proxy class names */

     private static long nextUniqueNumber = 0;

     private static Object nextUniqueNumberLock = new Object();

     /** set of all generated proxy classes, for isProxyClass implementation */

     private static Map<Class<?>, Void> proxyClasses =

         Collections.synchronizedMap(new WeakHashMap<Class<?>, Void>());

     /**

      * the invocation handler for this proxy instance.

      * @serial

      */

     protected InvocationHandler h;

     /**

      * Prohibits instantiation.

      */

     private ProxyImpl() {

     }

     /**

      * Constructs a new {@code Proxy} instance from a subclass

      * (typically, a dynamic proxy class) with the specified value

      * for its invocation handler.

      *

      * @param   h the invocation handler for this proxy instance

      */

     protected ProxyImpl(InvocationHandler h) {

         this.h = h;

     }

     /**

      * Returns the {@code java.lang.Class} object for a proxy class

      * given a class loader and an array of interfaces.  The proxy class

      * will be defined by the specified class loader and will implement

      * all of the supplied interfaces.  If a proxy class for the same

      * permutation of interfaces has already been defined by the class

      * loader, then the existing proxy class will be returned; otherwise,

      * a proxy class for those interfaces will be generated dynamically

      * and defined by the class loader.

      *

      * <p>There are several restrictions on the parameters that may be

      * passed to {@code Proxy.getProxyClass}:

      *

      * <ul>

      * <li>All of the {@code Class} objects in the

      * {@code interfaces} array must represent interfaces, not

      * classes or primitive types.

      *

      * <li>No two elements in the {@code interfaces} array may

      * refer to identical {@code Class} objects.

      *

      * <li>All of the interface types must be visible by name through the

      * specified class loader.  In other words, for class loader

      * {@code cl} and every interface {@code i}, the following

      * expression must be true:

      * <pre>

      *     Class.forName(i.getName(), false, cl) == i

      * </pre>

      *

      * <li>All non-public interfaces must be in the same package;

      * otherwise, it would not be possible for the proxy class to

      * implement all of the interfaces, regardless of what package it is

      * defined in.

      *

      * <li>For any set of member methods of the specified interfaces

      * that have the same signature:

      * <ul>

      * <li>If the return type of any of the methods is a primitive

      * type or void, then all of the methods must have that same

      * return type.

      * <li>Otherwise, one of the methods must have a return type that

      * is assignable to all of the return types of the rest of the

      * methods.

      * </ul>

      *

      * <li>The resulting proxy class must not exceed any limits imposed

      * on classes by the virtual machine.  For example, the VM may limit

      * the number of interfaces that a class may implement to 65535; in

      * that case, the size of the {@code interfaces} array must not

      * exceed 65535.

      * </ul>

      *

      * <p>If any of these restrictions are violated,

      * {@code Proxy.getProxyClass} will throw an

      * {@code IllegalArgumentException}.  If the {@code interfaces}

      * array argument or any of its elements are {@code null}, a

      * {@code NullPointerException} will be thrown.

      *

      * <p>Note that the order of the specified proxy interfaces is

      * significant: two requests for a proxy class with the same combination

      * of interfaces but in a different order will result in two distinct

      * proxy classes.

      *

      * @param   loader the class loader to define the proxy class

      * @param   interfaces the list of interfaces for the proxy class

      *          to implement

      * @return  a proxy class that is defined in the specified class loader

      *          and that implements the specified interfaces

      * @throws  IllegalArgumentException if any of the restrictions on the

      *          parameters that may be passed to {@code getProxyClass}

      *          are violated

      * @throws  NullPointerException if the {@code interfaces} array

      *          argument or any of its elements are {@code null}

      */

     public static Class<?> getProxyClass(ClassLoader loader,

                                          Class<?>... interfaces)

         throws IllegalArgumentException

     {

         if (interfaces.length > 65535) {

             throw new IllegalArgumentException("interface limit exceeded");

         }

         Class<?> proxyClass = null;

         /* collect interface names to use as key for proxy class cache */

         String[] interfaceNames = new String[interfaces.length];

         // for detecting duplicates

         Set<Class<?>> interfaceSet = new HashSet<>();

         for (int i = 0; i < interfaces.length; i++) {

             /*

              * Verify that the class loader resolves the name of this

              * interface to the same Class object.

              */

             String interfaceName = interfaces[i].getName();

             Class<?> interfaceClass = null;

             try {

                 interfaceClass = Class.forName(interfaceName, false, loader);

             } catch (ClassNotFoundException e) {

             }

             if (interfaceClass != interfaces[i]) {

                 throw new IllegalArgumentException(

                     interfaces[i] + " is not visible from class loader");

             }

             /*

              * Verify that the Class object actually represents an

              * interface.

              */

             if (!interfaceClass.isInterface()) {

                 throw new IllegalArgumentException(

                     interfaceClass.getName() + " is not an interface");

             }

             /*

              * Verify that this interface is not a duplicate.

              */

             if (interfaceSet.contains(interfaceClass)) {

                 throw new IllegalArgumentException(

                     "repeated interface: " + interfaceClass.getName());

             }

             interfaceSet.add(interfaceClass);

             interfaceNames[i] = interfaceName;

         }

         /*

          * Using string representations of the proxy interfaces as

          * keys in the proxy class cache (instead of their Class

          * objects) is sufficient because we require the proxy

          * interfaces to be resolvable by name through the supplied

          * class loader, and it has the advantage that using a string

          * representation of a class makes for an implicit weak

          * reference to the class.

          */

         List<String> key = Arrays.asList(interfaceNames);

         /*

          * Find or create the proxy class cache for the class loader.

          */

         Map<List<String>, Object> cache;

         synchronized (loaderToCache) {

             cache = loaderToCache.get(loader);

             if (cache == null) {

                 cache = new HashMap<>();

                 loaderToCache.put(loader, cache);

             }

             /*

              * This mapping will remain valid for the duration of this

              * method, without further synchronization, because the mapping

              * will only be removed if the class loader becomes unreachable.

              */

         }

         /*

          * Look up the list of interfaces in the proxy class cache using

          * the key.  This lookup will result in one of three possible

          * kinds of values:

          *     null, if there is currently no proxy class for the list of

          *         interfaces in the class loader,

          *     the pendingGenerationMarker object, if a proxy class for the

          *         list of interfaces is currently being generated,

          *     or a weak reference to a Class object, if a proxy class for

          *         the list of interfaces has already been generated.

          */

         synchronized (cache) {

             /*

              * Note that we need not worry about reaping the cache for

              * entries with cleared weak references because if a proxy class

              * has been garbage collected, its class loader will have been

              * garbage collected as well, so the entire cache will be reaped

              * from the loaderToCache map.

              */

             do {

                 Object value = cache.get(key);

                 if (value instanceof Reference) {

                     proxyClass = (Class<?>) ((Reference) value).get();

                 }

                 if (proxyClass != null) {

                     // proxy class already generated: return it

                     return proxyClass;

                 } else if (value == pendingGenerationMarker) {

                     // proxy class being generated: wait for it

                     try {

                         cache.wait();

                     } catch (InterruptedException e) {

                         /*

                          * The class generation that we are waiting for should

                          * take a small, bounded time, so we can safely ignore

                          * thread interrupts here.

                          */

                     }

                     continue;

                 } else {

                     /*

                      * No proxy class for this list of interfaces has been

                      * generated or is being generated, so we will go and

                      * generate it now.  Mark it as pending generation.

                      */

                     cache.put(key, pendingGenerationMarker);

                     break;

                 }

             } while (true);

         }

         try {

             String proxyPkg = null;     // package to define proxy class in

             /*

              * Record the package of a non-public proxy interface so that the

              * proxy class will be defined in the same package.  Verify that

              * all non-public proxy interfaces are in the same package.

              */

             for (int i = 0; i < interfaces.length; i++) {

                 int flags = interfaces[i].getModifiers();

                 if (!Modifier.isPublic(flags)) {

                     String name = interfaces[i].getName();

                     int n = name.lastIndexOf('.');

                     String pkg = ((n == -1) ? "" : name.substring(0, n + 1));

                     if (proxyPkg == null) {

                         proxyPkg = pkg;

                     } else if (!pkg.equals(proxyPkg)) {

                         throw new IllegalArgumentException(

                             "non-public interfaces from different packages");

                     }

                 }

             }

             if (proxyPkg == null) {     // if no non-public proxy interfaces,

                 proxyPkg = "";          // use the unnamed package

             }

             {

                 /*

                  * Choose a name for the proxy class to generate.

                  */

                 long num;

                 synchronized (nextUniqueNumberLock) {

                     num = nextUniqueNumber++;

                 }

                 String proxyName = proxyPkg + proxyClassNamePrefix + num;

                 /*

                  * Verify that the class loader hasn't already

                  * defined a class with the chosen name.

                  */

                 /*

                  * Generate the specified proxy class.

                  */

                 Generator gen = new Generator(proxyName, interfaces);

                 final byte[] proxyClassFile = gen.generateClassFile();

                 try {

                     proxyClass = defineClass0(loader, proxyName,

                         proxyClassFile);

                 } catch (ClassFormatError e) {

                     /*

                      * A ClassFormatError here means that (barring bugs in the

                      * proxy class generation code) there was some other

                      * invalid aspect of the arguments supplied to the proxy

                      * class creation (such as virtual machine limitations

                      * exceeded).

                      */

                     throw new IllegalArgumentException(e.toString());

                 }

                 gen.fillInMethods(proxyClass);

             }

             // add to set of all generated proxy classes, for isProxyClass

             proxyClasses.put(proxyClass, null);

         } finally {

             /*

              * We must clean up the "pending generation" state of the proxy

              * class cache entry somehow.  If a proxy class was successfully

              * generated, store it in the cache (with a weak reference);

              * otherwise, remove the reserved entry.  In all cases, notify

              * all waiters on reserved entries in this cache.

              */

             synchronized (cache) {

                 if (proxyClass != null) {

                     cache.put(key, new WeakReference<Class<?>>(proxyClass));

                 } else {

                     cache.remove(key);

                 }

                 cache.notifyAll();

             }

         }

         return proxyClass;

     }

     /**

      * Returns an instance of a proxy class for the specified interfaces

      * that dispatches method invocations to the specified invocation

      * handler.  This method is equivalent to:

      * <pre>

      *     Proxy.getProxyClass(loader, interfaces).

      *         getConstructor(new Class[] { InvocationHandler.class }).

      *         newInstance(new Object[] { handler });

      * </pre>

      *

      * <p>{@code Proxy.newProxyInstance} throws

      * {@code IllegalArgumentException} for the same reasons that

      * {@code Proxy.getProxyClass} does.

      *

      * @param   loader the class loader to define the proxy class

      * @param   interfaces the list of interfaces for the proxy class

      *          to implement

      * @param   h the invocation handler to dispatch method invocations to

      * @return  a proxy instance with the specified invocation handler of a

      *          proxy class that is defined by the specified class loader

      *          and that implements the specified interfaces

      * @throws  IllegalArgumentException if any of the restrictions on the

      *          parameters that may be passed to {@code getProxyClass}

      *          are violated

      * @throws  NullPointerException if the {@code interfaces} array

      *          argument or any of its elements are {@code null}, or

      *          if the invocation handler, {@code h}, is

      *          {@code null}

      */

     public static Object newProxyInstance(ClassLoader loader,

                                           Class<?>[] interfaces,

                                           InvocationHandler h)

         throws IllegalArgumentException

     {

         if (h == null) {

             throw new NullPointerException();

         }

         /*

          * Look up or generate the designated proxy class.

          */

         Class<?> cl = getProxyClass(loader, interfaces);

         /*

          * Invoke its constructor with the designated invocation handler.

          */

         try {

             Constructor cons = cl.getConstructor(constructorParams);

             return cons.newInstance(new Object[] { h });

         } catch (NoSuchMethodException e) {

             throw new InternalError(e.toString());

         } catch (IllegalAccessException e) {

             throw new InternalError(e.toString());

         } catch (InstantiationException e) {

             throw new InternalError(e.toString());

         } catch (InvocationTargetException e) {

             throw new InternalError(e.toString());

         }

     }

     /**

      * Returns true if and only if the specified class was dynamically

      * generated to be a proxy class using the {@code getProxyClass}

      * method or the {@code newProxyInstance} method.

      *

      * <p>The reliability of this method is important for the ability

      * to use it to make security decisions, so its implementation should

      * not just test if the class in question extends {@code Proxy}.

      *

      * @param   cl the class to test

      * @return  {@code true} if the class is a proxy class and

      *          {@code false} otherwise

      * @throws  NullPointerException if {@code cl} is {@code null}

      */

     public static boolean isProxyClass(Class<?> cl) {

         if (cl == null) {

             throw new NullPointerException();

         }

         return proxyClasses.containsKey(cl);

     }

     /**

      * Returns the invocation handler for the specified proxy instance.

      *

      * @param   proxy the proxy instance to return the invocation handler for

      * @return  the invocation handler for the proxy instance

      * @throws  IllegalArgumentException if the argument is not a

      *          proxy instance

      */

     public static InvocationHandler getInvocationHandler(Object proxy)

         throws IllegalArgumentException

     {

         /*

          * Verify that the object is actually a proxy instance.

          */

         if (!isProxyClass(proxy.getClass())) {

             throw new IllegalArgumentException("not a proxy instance");

         }

         ProxyImpl p = (ProxyImpl) proxy;

         return p.h;

     }

     @JavaScriptBody(args = { "ignore", "name", "byteCode" }, 

         body = 

             "var r = vm['_reload'];"

           + "if (!r) r = exports['_reload'];"

           + "return r(name, byteCode).constructor.$class;"

     )

     private static native Class defineClass0(

         ClassLoader loader, String name, byte[] b

     );

     private static class Generator {

         /*

          * In the comments below, "JVMS" refers to The Java Virtual Machine

          * Specification Second Edition and "JLS" refers to the original

          * version of The Java Language Specification, unless otherwise

          * specified.

          */

         /* need 1.6 bytecode */

         private static final int CLASSFILE_MAJOR_VERSION = 50;

         private static final int CLASSFILE_MINOR_VERSION = 0;

         /*

          * beginning of constants copied from

          * sun.tools.java.RuntimeConstants (which no longer exists):

          */

         /* constant pool tags */

         private static final int CONSTANT_UTF8 = 1;

         private static final int CONSTANT_UNICODE = 2;

         private static final int CONSTANT_INTEGER = 3;

         private static final int CONSTANT_FLOAT = 4;

         private static final int CONSTANT_LONG = 5;

         private static final int CONSTANT_DOUBLE = 6;

         private static final int CONSTANT_CLASS = 7;

         private static final int CONSTANT_STRING = 8;

         private static final int CONSTANT_FIELD = 9;

         private static final int CONSTANT_METHOD = 10;

         private static final int CONSTANT_INTERFACEMETHOD = 11;

         private static final int CONSTANT_NAMEANDTYPE = 12;

         /* access and modifier flags */

         private static final int ACC_PUBLIC = 0x00000001;

         private static final int ACC_FINAL = 0x00000010;

         private static final int ACC_SUPER = 0x00000020;

     // end of constants copied from sun.tools.java.RuntimeConstants

         /**

          * name of the superclass of proxy classes

          */

         private final static String superclassName = "java/lang/reflect/Proxy";

         /**

          * name of field for storing a proxy instance's invocation handler

          */

         private final static String handlerFieldName = "h";

         /* preloaded Method objects for methods in java.lang.Object */

         private static Method hashCodeMethod;

         private static Method equalsMethod;

         private static Method toStringMethod;

         static {

             try {

                 hashCodeMethod = Object.class.getMethod("hashCode");

                 equalsMethod

                     = Object.class.getMethod("equals", new Class[]{Object.class});

                 toStringMethod = Object.class.getMethod("toString");

             } catch (NoSuchMethodException e) {

                 throw new IllegalStateException(e.getMessage());

             }

         }

         /**

          * name of proxy class

          */

         private String className;

         /**

          * proxy interfaces

          */

         private Class[] interfaces;

         /**

          * constant pool of class being generated

          */

         private ConstantPool cp = new ConstantPool();

         /**

          * maps method signature string to list of ProxyMethod objects for proxy

          * methods with that signature

          */

         private Map<String, List<ProxyMethod>> proxyMethods

             = new HashMap<String, List<ProxyMethod>>();

         /**

          * count of ProxyMethod objects added to proxyMethods

          */

         private int proxyMethodCount = 0;

         /**

          * Construct a ProxyGenerator to generate a proxy class with the

          * specified name and for the given interfaces.

          *

          * A ProxyGenerator object contains the state for the ongoing generation

          * of a particular proxy class.

          */

         private Generator(String className, Class[] interfaces) {

             this.className = className;

             this.interfaces = interfaces;

         }

         /**

          * Generate a class file for the proxy class. This method drives the

          * class file generation process.

          */

         private byte[] generateClassFile() {

             /* ============================================================

              * Step 1: Assemble ProxyMethod objects for all methods to

              * generate proxy dispatching code for.

              */

             /*

              * Record that proxy methods are needed for the hashCode, equals,

              * and toString methods of java.lang.Object.  This is done before

              * the methods from the proxy interfaces so that the methods from

              * java.lang.Object take precedence over duplicate methods in the

              * proxy interfaces.

              */

             addProxyMethod(hashCodeMethod, Object.class);

             addProxyMethod(equalsMethod, Object.class);

             addProxyMethod(toStringMethod, Object.class);

             /*

              * Now record all of the methods from the proxy interfaces, giving

              * earlier interfaces precedence over later ones with duplicate

              * methods.

              */

             for (int i = 0; i < interfaces.length; i++) {

                 Method[] methods = interfaces[i].getMethods();

                 for (int j = 0; j < methods.length; j++) {

                     addProxyMethod(methods[j], interfaces[i]);

                 }

             }

             /*

              * For each set of proxy methods with the same signature,

              * verify that the methods' return types are compatible.

              */

             for (List<ProxyMethod> sigmethods : proxyMethods.values()) {

                 checkReturnTypes(sigmethods);

             }

             /* ============================================================

              * Step 2: Assemble FieldInfo and MethodInfo structs for all of

              * fields and methods in the class we are generating.

              */

             // will be done in fillInMethods

             /* ============================================================

              * Step 3: Write the final class file.

              */

             /*

              * Make sure that constant pool indexes are reserved for the

              * following items before starting to write the final class file.

              */

             cp.getClass(dotToSlash(className));

             cp.getClass(superclassName);

             for (int i = 0; i < interfaces.length; i++) {

                 cp.getClass(dotToSlash(interfaces[i].getName()));

             }

             /*

              * Disallow new constant pool additions beyond this point, since

              * we are about to write the final constant pool table.

              */

             cp.setReadOnly();

             ByteArrayOutputStream bout = new ByteArrayOutputStream();

             DataOutputStream dout = new DataOutputStream(bout);

             try {

                 /*

                  * Write all the items of the "ClassFile" structure.

                  * See JVMS section 4.1.

                  */

                 // u4 magic;

                 dout.writeInt(0xCAFEBABE);

                 // u2 minor_version;

                 dout.writeShort(CLASSFILE_MINOR_VERSION);

                 // u2 major_version;

                 dout.writeShort(CLASSFILE_MAJOR_VERSION);

                 cp.write(dout);             // (write constant pool)

                 // u2 access_flags;

                 dout.writeShort(ACC_PUBLIC | ACC_FINAL | ACC_SUPER);

                 // u2 this_class;

                 dout.writeShort(cp.getClass(dotToSlash(className)));

                 // u2 super_class;

                 dout.writeShort(cp.getClass(superclassName));

                 // u2 interfaces_count;

                 dout.writeShort(interfaces.length);

                 // u2 interfaces[interfaces_count];

                 for (int i = 0; i < interfaces.length; i++) {

                     dout.writeShort(cp.getClass(

                         dotToSlash(interfaces[i].getName())));

                 }

                 // u2 fields_count;

                 dout.writeShort(0);

                 // u2 methods_count;

                 dout.writeShort(0);

                 // u2 attributes_count;

                 dout.writeShort(0); // (no ClassFile attributes for proxy classes)

             } catch (IOException e) {

                 throw new InternalError("unexpected I/O Exception");

             }

             return bout.toByteArray();

         }

         @JavaScriptBody(args = { "c", "sig", "method", "primitive" }, body = 

             "var p = c.cnstr.prototype;\n" +

             "p[sig] = function() {\n" +

             "  var h = this['_h']();\n" +

             "  var res = h['invoke__Ljava_lang_Object_2Ljava_lang_Object_2Ljava_lang_reflect_Method_2_3Ljava_lang_Object_2'](this, method, arguments);\n" +

             "  \n" +

             "  \n" +

             "  return res;\n" +

             "};"

         )

         private static native void defineMethod(Class<?> proxyClass, String sig, Method method, boolean primitive);

         @JavaScriptBody(args = "c", body = 

               "var h = c.cnstr['cons__VLjava_lang_reflect_InvocationHandler_2'] = function(h) {\n"

             + "  c.superclass.cnstr['cons__VLjava_lang_reflect_InvocationHandler_2'].call(this, h);\n"

             + "}\n"

             + "h.cls = c.cnstr;\n"

         )

         private static native void defineConstructor(Class<?> proxyClass);

         final void fillInMethods(Class<?> proxyClass) {

             for (List<ProxyMethod> sigmethods : proxyMethods.values()) {

                 for (ProxyMethod pm : sigmethods) {

                     String sig = MethodImpl.toSignature(pm.method);

                     defineMethod(proxyClass, sig, pm.method, pm.method.getReturnType().isPrimitive());

                 }

             }

             defineConstructor(proxyClass);

         }

         /**

          * Add another method to be proxied, either by creating a new

          * ProxyMethod object or augmenting an old one for a duplicate method.

          *

          * "fromClass" indicates the proxy interface that the method was found

          * through, which may be different from (a subinterface of) the method's

          * "declaring class". Note that the first Method object passed for a

          * given name and descriptor identifies the Method object (and thus the

          * declaring class) that will be passed to the invocation handler's

          * "invoke" method for a given set of duplicate methods.

          */

         private void addProxyMethod(Method m, Class fromClass) {

             String name = m.getName();

             Class[] parameterTypes = m.getParameterTypes();

             Class returnType = m.getReturnType();

             Class[] exceptionTypes = m.getExceptionTypes();

             String sig = MethodImpl.toSignature(m);

             List<ProxyMethod> sigmethods = proxyMethods.get(sig);

             if (sigmethods != null) {

                 for (ProxyMethod pm : sigmethods) {

                     if (returnType == pm.returnType) {

                         /*

                          * Found a match: reduce exception types to the

                          * greatest set of exceptions that can thrown

                          * compatibly with the throws clauses of both

                          * overridden methods.

                          */

                         List<Class<?>> legalExceptions = new ArrayList<Class<?>>();

                         collectCompatibleTypes(

                             exceptionTypes, pm.exceptionTypes, legalExceptions);

                         collectCompatibleTypes(

                             pm.exceptionTypes, exceptionTypes, legalExceptions);

                         pm.exceptionTypes = new Class[legalExceptions.size()];

                         pm.exceptionTypes

                             = legalExceptions.toArray(pm.exceptionTypes);

                         return;

                     }

                 }

             } else {

                 sigmethods = new ArrayList<ProxyMethod>(3);

                 proxyMethods.put(sig, sigmethods);

             }

             sigmethods.add(new ProxyMethod(m, name, parameterTypes, returnType,

                 exceptionTypes, fromClass));

         }

         /**

          * For a given set of proxy methods with the same signature, check that

          * their return types are compatible according to the Proxy

          * specification.

          *

          * Specifically, if there is more than one such method, then all of the

          * return types must be reference types, and there must be one return

          * type that is assignable to each of the rest of them.

          */

         private static void checkReturnTypes(List<ProxyMethod> methods) {

             /*

              * If there is only one method with a given signature, there

              * cannot be a conflict.  This is the only case in which a

              * primitive (or void) return type is allowed.

              */

             if (methods.size() < 2) {

                 return;

             }

             /*

              * List of return types that are not yet known to be

              * assignable from ("covered" by) any of the others.

              */

             LinkedList<Class<?>> uncoveredReturnTypes = new LinkedList<Class<?>>();

             nextNewReturnType:

             for (ProxyMethod pm : methods) {

                 Class<?> newReturnType = pm.returnType;

                 if (newReturnType.isPrimitive()) {

                     throw new IllegalArgumentException(

                         "methods with same signature "

                         + getFriendlyMethodSignature(pm.methodName,

                             pm.parameterTypes)

                         + " but incompatible return types: "

                         + newReturnType.getName() + " and others");

                 }

                 boolean added = false;

                 /*

                  * Compare the new return type to the existing uncovered

                  * return types.

                  */

                 ListIterator<Class<?>> liter = uncoveredReturnTypes.listIterator();

                 while (liter.hasNext()) {

                     Class<?> uncoveredReturnType = liter.next();

                     /*

                      * If an existing uncovered return type is assignable

                      * to this new one, then we can forget the new one.

                      */

                     if (newReturnType.isAssignableFrom(uncoveredReturnType)) {

                         assert !added;

                         continue nextNewReturnType;

                     }

                     /*

                      * If the new return type is assignable to an existing

                      * uncovered one, then should replace the existing one

                      * with the new one (or just forget the existing one,

                      * if the new one has already be put in the list).

                      */

                     if (uncoveredReturnType.isAssignableFrom(newReturnType)) {

                         // (we can assume that each return type is unique)

                         if (!added) {

                             liter.set(newReturnType);

                             added = true;

                         } else {

                             liter.remove();

                         }

                     }

                 }

                 /*

                  * If we got through the list of existing uncovered return

                  * types without an assignability relationship, then add

                  * the new return type to the list of uncovered ones.

                  */

                 if (!added) {

                     uncoveredReturnTypes.add(newReturnType);

                 }

             }

             /*

              * We shouldn't end up with more than one return type that is

              * not assignable from any of the others.

              */

             if (uncoveredReturnTypes.size() > 1) {

                 ProxyMethod pm = methods.get(0);

                 throw new IllegalArgumentException(

                     "methods with same signature "

                     + getFriendlyMethodSignature(pm.methodName, pm.parameterTypes)

                     + " but incompatible return types: " + uncoveredReturnTypes);

             }

         }

         /**

          * A ProxyMethod object represents a proxy method in the proxy class

          * being generated: a method whose implementation will encode and

          * dispatch invocations to the proxy instance's invocation handler.

          */

         private class ProxyMethod {

             private final Method method;

             public String methodName;

             public Class[] parameterTypes;

             public Class returnType;

             public Class[] exceptionTypes;

             public Class fromClass;

             public String methodFieldName;

             private ProxyMethod(Method m, 

                 String methodName, Class[] parameterTypes, 

                 Class returnType, Class[] exceptionTypes, 

                 Class fromClass

             ) {

                 this.method = m;

                 this.methodName = methodName;

                 this.parameterTypes = parameterTypes;

                 this.returnType = returnType;

                 this.exceptionTypes = exceptionTypes;

                 this.fromClass = fromClass;

                 this.methodFieldName = "m" + proxyMethodCount++;

             }

         }

         /*

          * ==================== General Utility Methods ====================

          */

         /**

          * Convert a fully qualified class name that uses '.' as the package

          * separator, the external representation used by the Java language and

          * APIs, to a fully qualified class name that uses '/' as the package

          * separator, the representation used in the class file format (see JVMS

          * section 4.2).

          */

         private static String dotToSlash(String name) {

             return name.replace('.', '/');

         }

         /**

          * Return the list of "parameter descriptor" strings enclosed in

          * parentheses corresponding to the given parameter types (in other

          * words, a method descriptor without a return descriptor). This string

          * is useful for constructing string keys for methods without regard to

          * their return type.

          */

         private static String getParameterDescriptors(Class[] parameterTypes) {

             StringBuilder desc = new StringBuilder("(");

             for (int i = 0; i < parameterTypes.length; i++) {

                 desc.append(getFieldType(parameterTypes[i]));

             }

             desc.append(')');

             return desc.toString();

         }

         /**

          * Return the "field type" string for the given type, appropriate for a

          * field descriptor, a parameter descriptor, or a return descriptor

          * other than "void". See JVMS section 4.3.2.

          */

         private static String getFieldType(Class type) {

             if (type.isPrimitive()) {

                 return PrimitiveTypeInfo.get(type).baseTypeString;

             } else if (type.isArray()) {

                 /*

                  * According to JLS 20.3.2, the getName() method on Class does

                  * return the VM type descriptor format for array classes (only);

                  * using that should be quicker than the otherwise obvious code:

                  *

                  *     return "[" + getTypeDescriptor(type.getComponentType());

                  */

                 return type.getName().replace('.', '/');

             } else {

                 return "L" + dotToSlash(type.getName()) + ";";

             }

         }

         /**

          * Returns a human-readable string representing the signature of a

          * method with the given name and parameter types.

          */

         private static String getFriendlyMethodSignature(String name,

             Class[] parameterTypes) {

             StringBuilder sig = new StringBuilder(name);

             sig.append('(');

             for (int i = 0; i < parameterTypes.length; i++) {

                 if (i > 0) {

                     sig.append(',');

                 }

                 Class parameterType = parameterTypes[i];

                 int dimensions = 0;

                 while (parameterType.isArray()) {

                     parameterType = parameterType.getComponentType();

                     dimensions++;

                 }

                 sig.append(parameterType.getName());

                 while (dimensions-- > 0) {

                     sig.append("[]");

                 }

             }

             sig.append(')');

             return sig.toString();

         }

         /**

          * Add to the given list all of the types in the "from" array that are

          * not already contained in the list and are assignable to at least one

          * of the types in the "with" array.

          *

          * This method is useful for computing the greatest common set of

          * declared exceptions from duplicate methods inherited from different

          * interfaces.

          */

         private static void collectCompatibleTypes(Class<?>[] from,

             Class<?>[] with,

             List<Class<?>> list) {

             for (int i = 0; i < from.length; i++) {

                 if (!list.contains(from[i])) {

                     for (int j = 0; j < with.length; j++) {

                         if (with[j].isAssignableFrom(from[i])) {

                             list.add(from[i]);

                             break;

                         }

                     }

                 }

             }

         }

         /**

          * A PrimitiveTypeInfo object contains assorted information about a

          * primitive type in its public fields. The struct for a particular

          * primitive type can be obtained using the static "get" method.

          */

         private static class PrimitiveTypeInfo {

             /**

              * "base type" used in various descriptors (see JVMS section 4.3.2)

              */

             public String baseTypeString;

             /**

              * name of corresponding wrapper class

              */

             public String wrapperClassName;

             /**

              * method descriptor for wrapper class "valueOf" factory method

              */

             public String wrapperValueOfDesc;

             /**

              * name of wrapper class method for retrieving primitive value

              */

             public String unwrapMethodName;

             /**

              * descriptor of same method

              */

             public String unwrapMethodDesc;

             private static Map<Class, PrimitiveTypeInfo> table

                 = new HashMap<Class, PrimitiveTypeInfo>();

             static {

                 add(byte.class, Byte.class);

                 add(char.class, Character.class);

                 add(double.class, Double.class);

                 add(float.class, Float.class);

                 add(int.class, Integer.class);

                 add(long.class, Long.class);

                 add(short.class, Short.class);

                 add(boolean.class, Boolean.class);

             }

             private static void add(Class primitiveClass, Class wrapperClass) {

                 table.put(primitiveClass,

                     new PrimitiveTypeInfo(primitiveClass, wrapperClass));

             }

             private PrimitiveTypeInfo(Class primitiveClass, Class wrapperClass) {

                 assert primitiveClass.isPrimitive();

                 baseTypeString

                     = Array.newInstance(primitiveClass, 0)

                     .getClass().getName().substring(1);

                 wrapperClassName = dotToSlash(wrapperClass.getName());

                 wrapperValueOfDesc

                     = "(" + baseTypeString + ")L" + wrapperClassName + ";";

                 unwrapMethodName = primitiveClass.getName() + "Value";

                 unwrapMethodDesc = "()" + baseTypeString;

             }

             public static PrimitiveTypeInfo get(Class cl) {

                 return table.get(cl);

             }

         }

         /**

          * A ConstantPool object represents the constant pool of a class file

          * being generated. This representation of a constant pool is designed

          * specifically for use by ProxyGenerator; in particular, it assumes

          * that constant pool entries will not need to be resorted (for example,

          * by their type, as the Java compiler does), so that the final index

          * value can be assigned and used when an entry is first created.

          *

          * Note that new entries cannot be created after the constant pool has

          * been written to a class file. To prevent such logic errors, a

          * ConstantPool instance can be marked "read only", so that further

          * attempts to add new entries will fail with a runtime exception.

          *

          * See JVMS section 4.4 for more information about the constant pool of

          * a class file.

          */

         private static class ConstantPool {

             /**

              * list of constant pool entries, in constant pool index order.

              *

              * This list is used when writing the constant pool to a stream and

              * for assigning the next index value. Note that element 0 of this

              * list corresponds to constant pool index 1.

              */

             private List<Entry> pool = new ArrayList<Entry>(32);

             /**

              * maps constant pool data of all types to constant pool indexes.

              *

              * This map is used to look up the index of an existing entry for

              * values of all types.

              */

             private Map<Object, Short> map = new HashMap<Object, Short>(16);

             /**

              * true if no new constant pool entries may be added

              */

             private boolean readOnly = false;

             /**

              * Get or assign the index for a CONSTANT_Utf8 entry.

              */

             public short getUtf8(String s) {

                 if (s == null) {

                     throw new NullPointerException();

                 }

                 return getValue(s);

             }

             /**

              * Get or assign the index for a CONSTANT_Integer entry.

              */

             public short getInteger(int i) {

                 return getValue(new Integer(i));

             }

             /**

              * Get or assign the index for a CONSTANT_Float entry.

              */

             public short getFloat(float f) {

                 return getValue(new Float(f));

             }

             /**

              * Get or assign the index for a CONSTANT_Class entry.

              */

             public short getClass(String name) {

                 short utf8Index = getUtf8(name);

                 return getIndirect(new IndirectEntry(

                     CONSTANT_CLASS, utf8Index));

             }

             /**

              * Get or assign the index for a CONSTANT_String entry.

              */

             public short getString(String s) {

                 short utf8Index = getUtf8(s);

                 return getIndirect(new IndirectEntry(

                     CONSTANT_STRING, utf8Index));

             }

             /**

              * Get or assign the index for a CONSTANT_FieldRef entry.

              */

             public short getFieldRef(String className,

                 String name, String descriptor) {

                 short classIndex = getClass(className);

                 short nameAndTypeIndex = getNameAndType(name, descriptor);

                 return getIndirect(new IndirectEntry(

                     CONSTANT_FIELD, classIndex, nameAndTypeIndex));

             }

             /**

              * Get or assign the index for a CONSTANT_MethodRef entry.

              */

             public short getMethodRef(String className,

                 String name, String descriptor) {

                 short classIndex = getClass(className);

                 short nameAndTypeIndex = getNameAndType(name, descriptor);

                 return getIndirect(new IndirectEntry(

                     CONSTANT_METHOD, classIndex, nameAndTypeIndex));

             }

             /**

              * Get or assign the index for a CONSTANT_InterfaceMethodRef entry.

              */

             public short getInterfaceMethodRef(String className, String name,

                 String descriptor) {

                 short classIndex = getClass(className);

                 short nameAndTypeIndex = getNameAndType(name, descriptor);

                 return getIndirect(new IndirectEntry(

                     CONSTANT_INTERFACEMETHOD, classIndex, nameAndTypeIndex));

             }

             /**

              * Get or assign the index for a CONSTANT_NameAndType entry.

              */

             public short getNameAndType(String name, String descriptor) {

                 short nameIndex = getUtf8(name);

                 short descriptorIndex = getUtf8(descriptor);

                 return getIndirect(new IndirectEntry(

                     CONSTANT_NAMEANDTYPE, nameIndex, descriptorIndex));

             }

             /**

              * Set this ConstantPool instance to be "read only".

              *

              * After this method has been called, further requests to get an

              * index for a non-existent entry will cause an InternalError to be

              * thrown instead of creating of the entry.

              */

             public void setReadOnly() {

                 readOnly = true;

             }

             /**

              * Write this constant pool to a stream as part of the class file

              * format.

              *

              * This consists of writing the "constant_pool_count" and

              * "constant_pool[]" items of the "ClassFile" structure, as

              * described in JVMS section 4.1.

              */

             public void write(OutputStream out) throws IOException {

                 DataOutputStream dataOut = new DataOutputStream(out);

                 // constant_pool_count: number of entries plus one

                 dataOut.writeShort(pool.size() + 1);

                 for (Entry e : pool) {

                     e.write(dataOut);

                 }

             }

             /**

              * Add a new constant pool entry and return its index.

              */

             private short addEntry(Entry entry) {

                 pool.add(entry);

                 /*

                  * Note that this way of determining the index of the

                  * added entry is wrong if this pool supports

                  * CONSTANT_Long or CONSTANT_Double entries.

                  */

                 if (pool.size() >= 65535) {

                     throw new IllegalArgumentException(

                         "constant pool size limit exceeded");

                 }

                 return (short) pool.size();

             }

             /**

              * Get or assign the index for an entry of a type that contains a

              * direct value. The type of the given object determines the type of

              * the desired entry as follows:

              *

              * java.lang.String CONSTANT_Utf8 java.lang.Integer CONSTANT_Integer

              * java.lang.Float CONSTANT_Float java.lang.Long CONSTANT_Long

              * java.lang.Double CONSTANT_DOUBLE

              */

             private short getValue(Object key) {

                 Short index = map.get(key);

                 if (index != null) {

                     return index.shortValue();

                 } else {

                     if (readOnly) {

                         throw new InternalError(

                             "late constant pool addition: " + key);

                     }

                     short i = addEntry(new ValueEntry(key));

                     map.put(key, new Short(i));

                     return i;

                 }

             }

             /**

              * Get or assign the index for an entry of a type that contains

              * references to other constant pool entries.

              */

             private short getIndirect(IndirectEntry e) {

                 Short index = map.get(e);

                 if (index != null) {

                     return index.shortValue();

                 } else {

                     if (readOnly) {

                         throw new InternalError("late constant pool addition");

                     }

                     short i = addEntry(e);

                     map.put(e, new Short(i));

                     return i;

                 }

             }

             /**

              * Entry is the abstact superclass of all constant pool entry types

              * that can be stored in the "pool" list; its purpose is to define a

              * common method for writing constant pool entries to a class file.

              */

             private static abstract class Entry {

                 public abstract void write(DataOutputStream out)

                     throws IOException;

             }

             /**

              * ValueEntry represents a constant pool entry of a type that

              * contains a direct value (see the comments for the "getValue"

              * method for a list of such types).

              *

              * ValueEntry objects are not used as keys for their entries in the

              * Map "map", so no useful hashCode or equals methods are defined.

              */

             private static class ValueEntry extends Entry {

                 private Object value;

                 public ValueEntry(Object value) {

                     this.value = value;

                 }

                 public void write(DataOutputStream out) throws IOException {

                     if (value instanceof String) {

                         out.writeByte(CONSTANT_UTF8);

                         out.writeUTF((String) value);

                     } else if (value instanceof Integer) {

                         out.writeByte(CONSTANT_INTEGER);

                         out.writeInt(((Integer) value).intValue());

                     } else if (value instanceof Float) {

                         out.writeByte(CONSTANT_FLOAT);

                         out.writeFloat(((Float) value).floatValue());

                     } else if (value instanceof Long) {

                         out.writeByte(CONSTANT_LONG);

                         out.writeLong(((Long) value).longValue());

                     } else if (value instanceof Double) {

                         out.writeDouble(CONSTANT_DOUBLE);

                         out.writeDouble(((Double) value).doubleValue());

                     } else {

                         throw new InternalError("bogus value entry: " + value);

                     }

                 }

             }

             /**

              * IndirectEntry represents a constant pool entry of a type that

              * references other constant pool entries, i.e., the following

              * types:

              *

              * CONSTANT_Class, CONSTANT_String, CONSTANT_Fieldref,

              * CONSTANT_Methodref, CONSTANT_InterfaceMethodref, and

              * CONSTANT_NameAndType.

              *

              * Each of these entry types contains either one or two indexes of

              * other constant pool entries.

              *

              * IndirectEntry objects are used as the keys for their entries in

              * the Map "map", so the hashCode and equals methods are overridden

              * to allow matching.

              */

             private static class IndirectEntry extends Entry {

                 private int tag;

                 private short index0;

                 private short index1;

                 /**

                  * Construct an IndirectEntry for a constant pool entry type

                  * that contains one index of another entry.

                  */

                 public IndirectEntry(int tag, short index) {

                     this.tag = tag;

                     this.index0 = index;

                     this.index1 = 0;

                 }

                 /**

                  * Construct an IndirectEntry for a constant pool entry type

                  * that contains two indexes for other entries.

                  */

                 public IndirectEntry(int tag, short index0, short index1) {

                     this.tag = tag;

                     this.index0 = index0;

                     this.index1 = index1;

                 }

                 public void write(DataOutputStream out) throws IOException {

                     out.writeByte(tag);

                     out.writeShort(index0);

                     /*

                      * If this entry type contains two indexes, write

                      * out the second, too.

                      */

                     if (tag == CONSTANT_FIELD

                         || tag == CONSTANT_METHOD

                         || tag == CONSTANT_INTERFACEMETHOD

                         || tag == CONSTANT_NAMEANDTYPE) {

                         out.writeShort(index1);

                     }

                 }

                 public int hashCode() {

                     return tag + index0 + index1;

                 }

                 public boolean equals(Object obj) {

                     if (obj instanceof IndirectEntry) {

                         IndirectEntry other = (IndirectEntry) obj;

                         if (tag == other.tag

                             && index0 == other.index0 && index1 == other.index1) {

                             return true;

                         }

                     }

                     return false;

                 }

             }

         }

     }

 }