/*

  * Copyright (c) 1996, 2011, 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 java.io;

 import java.lang.ref.Reference;

 import java.lang.ref.ReferenceQueue;

 import java.lang.ref.SoftReference;

 import java.lang.ref.WeakReference;

 import java.lang.reflect.Constructor;

 import java.lang.reflect.Field;

 import java.lang.reflect.InvocationTargetException;

 import java.lang.reflect.Member;

 import java.lang.reflect.Method;

 import java.lang.reflect.Modifier;

 import java.lang.reflect.Proxy;

 import java.util.ArrayList;

 import java.util.Arrays;

 import java.util.Collections;

 import java.util.Comparator;

 import java.util.HashSet;

 import java.util.Set;

 /**

  * Serialization's descriptor for classes.  It contains the name and

  * serialVersionUID of the class.  The ObjectStreamClass for a specific class

  * loaded in this Java VM can be found/created using the lookup method.

  *

  * <p>The algorithm to compute the SerialVersionUID is described in

  * <a href="../../../platform/serialization/spec/class.html#4100">Object

  * Serialization Specification, Section 4.6, Stream Unique Identifiers</a>.

  *

  * @author      Mike Warres

  * @author      Roger Riggs

  * @see ObjectStreamField

  * @see <a href="../../../platform/serialization/spec/class.html">Object Serialization Specification, Section 4, Class Descriptors</a>

  * @since   JDK1.1

  */

 public class ObjectStreamClass implements Serializable {

     /** serialPersistentFields value indicating no serializable fields */

     public static final ObjectStreamField[] NO_FIELDS =

         new ObjectStreamField[0];

     private static final long serialVersionUID = -6120832682080437368L;

     private static final ObjectStreamField[] serialPersistentFields =

         NO_FIELDS;

     /** class associated with this descriptor (if any) */

     private Class<?> cl;

     /** name of class represented by this descriptor */

     private String name;

     /** serialVersionUID of represented class (null if not computed yet) */

     private volatile Long suid;

     /** true if represents dynamic proxy class */

     private boolean isProxy;

     /** true if represents enum type */

     private boolean isEnum;

     /** true if represented class implements Serializable */

     private boolean serializable;

     /** true if represented class implements Externalizable */

     private boolean externalizable;

     /** true if desc has data written by class-defined writeObject method */

     private boolean hasWriteObjectData;

     /**

      * true if desc has externalizable data written in block data format; this

      * must be true by default to accommodate ObjectInputStream subclasses which

      * override readClassDescriptor() to return class descriptors obtained from

      * ObjectStreamClass.lookup() (see 4461737)

      */

     private boolean hasBlockExternalData = true;

     /** exception (if any) thrown while attempting to resolve class */

     private ClassNotFoundException resolveEx;

     /** exception (if any) to throw if non-enum deserialization attempted */

     private InvalidClassException deserializeEx;

     /** exception (if any) to throw if non-enum serialization attempted */

     private InvalidClassException serializeEx;

     /** exception (if any) to throw if default serialization attempted */

     private InvalidClassException defaultSerializeEx;

     /** serializable fields */

     private ObjectStreamField[] fields;

     /** aggregate marshalled size of primitive fields */

     private int primDataSize;

     /** number of non-primitive fields */

     private int numObjFields;

     /** reflector for setting/getting serializable field values */

 //    private FieldReflector fieldRefl;

     /** data layout of serialized objects described by this class desc */

     private volatile ClassDataSlot[] dataLayout;

     /** serialization-appropriate constructor, or null if none */

     private Constructor cons;

     /** class-defined writeObject method, or null if none */

     private Method writeObjectMethod;

     /** class-defined readObject method, or null if none */

     private Method readObjectMethod;

     /** class-defined readObjectNoData method, or null if none */

     private Method readObjectNoDataMethod;

     /** class-defined writeReplace method, or null if none */

     private Method writeReplaceMethod;

     /** class-defined readResolve method, or null if none */

     private Method readResolveMethod;

     /** local class descriptor for represented class (may point to self) */

     private ObjectStreamClass localDesc;

     /** superclass descriptor appearing in stream */

     private ObjectStreamClass superDesc;

     /**

      * Initializes native code.

      */

     private static native void initNative();

     static {

         initNative();

     }

     /**

      * Find the descriptor for a class that can be serialized.  Creates an

      * ObjectStreamClass instance if one does not exist yet for class. Null is

      * returned if the specified class does not implement java.io.Serializable

      * or java.io.Externalizable.

      *

      * @param   cl class for which to get the descriptor

      * @return  the class descriptor for the specified class

      */

     public static ObjectStreamClass lookup(Class<?> cl) {

         return lookup(cl, false);

     }

     /**

      * Returns the descriptor for any class, regardless of whether it

      * implements {@link Serializable}.

      *

      * @param        cl class for which to get the descriptor

      * @return       the class descriptor for the specified class

      * @since 1.6

      */

     public static ObjectStreamClass lookupAny(Class<?> cl) {

         return lookup(cl, true);

     }

     /**

      * Returns the name of the class described by this descriptor.

      * This method returns the name of the class in the format that

      * is used by the {@link Class#getName} method.

      *

      * @return a string representing the name of the class

      */

     public String getName() {

         return name;

     }

     /**

      * Return the serialVersionUID for this class.  The serialVersionUID

      * defines a set of classes all with the same name that have evolved from a

      * common root class and agree to be serialized and deserialized using a

      * common format.  NonSerializable classes have a serialVersionUID of 0L.

      *

      * @return  the SUID of the class described by this descriptor

      */

     public long getSerialVersionUID() {

         // REMIND: synchronize instead of relying on volatile?

         if (suid == null) {

             return computeDefaultSUID(cl);

         }

         return suid.longValue();

     }

     /**

      * Return the class in the local VM that this version is mapped to.  Null

      * is returned if there is no corresponding local class.

      *

      * @return  the <code>Class</code> instance that this descriptor represents

      */

     public Class<?> forClass() {

         return cl;

     }

     /**

      * Return an array of the fields of this serializable class.

      *

      * @return  an array containing an element for each persistent field of

      *          this class. Returns an array of length zero if there are no

      *          fields.

      * @since 1.2

      */

     public ObjectStreamField[] getFields() {

         return getFields(true);

     }

     /**

      * Get the field of this class by name.

      *

      * @param   name the name of the data field to look for

      * @return  The ObjectStreamField object of the named field or null if

      *          there is no such named field.

      */

     public ObjectStreamField getField(String name) {

         return getField(name, null);

     }

     /**

      * Return a string describing this ObjectStreamClass.

      */

     public String toString() {

         return name + ": static final long serialVersionUID = " +

             getSerialVersionUID() + "L;";

     }

     /**

      * Looks up and returns class descriptor for given class, or null if class

      * is non-serializable and "all" is set to false.

      *

      * @param   cl class to look up

      * @param   all if true, return descriptors for all classes; if false, only

      *          return descriptors for serializable classes

      */

     static ObjectStreamClass lookup(Class<?> cl, boolean all) {

         if (!(all || Serializable.class.isAssignableFrom(cl))) {

             return null;

         }

         Object entry = null;

         EntryFuture future = null;

         if (entry == null) {

             EntryFuture newEntry = new EntryFuture();

             Reference<?> newRef = new SoftReference<>(newEntry);

             if (entry == null) {

                 future = newEntry;

             }

         }

         if (entry instanceof ObjectStreamClass) {  // check common case first

             return (ObjectStreamClass) entry;

         }

         if (entry instanceof EntryFuture) {

             future = (EntryFuture) entry;

             if (true) {

                 /*

                  * Handle nested call situation described by 4803747: waiting

                  * for future value to be set by a lookup() call further up the

                  * stack will result in deadlock, so calculate and set the

                  * future value here instead.

                  */

                 entry = null;

             } else {

                 entry = future.get();

             }

         }

         if (entry == null) {

             try {

                 entry = new ObjectStreamClass(cl);

             } catch (Throwable th) {

                 entry = th;

             }

             // nested lookup call already set future

             entry = future.get();

         }

         if (entry instanceof ObjectStreamClass) {

             return (ObjectStreamClass) entry;

         } else if (entry instanceof RuntimeException) {

             throw (RuntimeException) entry;

         } else if (entry instanceof Error) {

             throw (Error) entry;

         } else {

             throw new InternalError("unexpected entry: " + entry);

         }

     }

     /**

      * Placeholder used in class descriptor and field reflector lookup tables

      * for an entry in the process of being initialized.  (Internal) callers

      * which receive an EntryFuture belonging to another thread as the result

      * of a lookup should call the get() method of the EntryFuture; this will

      * return the actual entry once it is ready for use and has been set().  To

      * conserve objects, EntryFutures synchronize on themselves.

      */

     private static class EntryFuture {

         private static final Object unset = new Object();

         private Object entry = unset;

         /**

          * Attempts to set the value contained by this EntryFuture.  If the

          * EntryFuture's value has not been set already, then the value is

          * saved, any callers blocked in the get() method are notified, and

          * true is returned.  If the value has already been set, then no saving

          * or notification occurs, and false is returned.

          */

         synchronized boolean set(Object entry) {

             if (this.entry != unset) {

                 return false;

             }

             this.entry = entry;

             notifyAll();

             return true;

         }

         /**

          * Returns the value contained by this EntryFuture, blocking if

          * necessary until a value is set.

          */

         synchronized Object get() {

             boolean interrupted = false;

             while (entry == unset) {

                 try {

                     wait();

                 } catch (InterruptedException ex) {

                     interrupted = true;

                 }

             }

             return entry;

         }

     }

     /**

      * Creates local class descriptor representing given class.

      */

     private ObjectStreamClass(final Class<?> cl) {

         this.cl = cl;

         name = cl.getName();

         isProxy = Proxy.isProxyClass(cl);

         isEnum = Enum.class.isAssignableFrom(cl);

         serializable = Serializable.class.isAssignableFrom(cl);

         externalizable = Externalizable.class.isAssignableFrom(cl);

         Class<?> superCl = cl.getSuperclass();

         superDesc = (superCl != null) ? lookup(superCl, false) : null;

         localDesc = this;

         suid = Long.valueOf(0);

         fields = NO_FIELDS;

         if (deserializeEx == null) {

             if (isEnum) {

                 deserializeEx = new InvalidClassException(name, "enum type");

             } else if (cons == null) {

                 deserializeEx = new InvalidClassException(

                     name, "no valid constructor");

             }

         }

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

             if (fields[i].getField() == null) {

                 defaultSerializeEx = new InvalidClassException(

                     name, "unmatched serializable field(s) declared");

             }

         }

     }

     /**

      * Creates blank class descriptor which should be initialized via a

      * subsequent call to initProxy(), initNonProxy() or readNonProxy().

      */

     ObjectStreamClass() {

     }

     /**

      * Initializes class descriptor representing a proxy class.

      */

     void initProxy(Class<?> cl,

                    ClassNotFoundException resolveEx,

                    ObjectStreamClass superDesc)

         throws InvalidClassException

     {

         this.cl = cl;

         this.resolveEx = resolveEx;

         this.superDesc = superDesc;

         isProxy = true;

         serializable = true;

         suid = Long.valueOf(0);

         fields = NO_FIELDS;

         if (cl != null) {

             localDesc = lookup(cl, true);

             if (!localDesc.isProxy) {

                 throw new InvalidClassException(

                     "cannot bind proxy descriptor to a non-proxy class");

             }

             name = localDesc.name;

             externalizable = localDesc.externalizable;

             cons = localDesc.cons;

             writeReplaceMethod = localDesc.writeReplaceMethod;

             readResolveMethod = localDesc.readResolveMethod;

             deserializeEx = localDesc.deserializeEx;

         }

     }

     /**

      * Initializes class descriptor representing a non-proxy class.

      */

     void initNonProxy(ObjectStreamClass model,

                       Class<?> cl,

                       ClassNotFoundException resolveEx,

                       ObjectStreamClass superDesc)

         throws InvalidClassException

     {

         this.cl = cl;

         this.resolveEx = resolveEx;

         this.superDesc = superDesc;

         name = model.name;

         suid = Long.valueOf(model.getSerialVersionUID());

         isProxy = false;

         isEnum = model.isEnum;

         serializable = model.serializable;

         externalizable = model.externalizable;

         hasBlockExternalData = model.hasBlockExternalData;

         hasWriteObjectData = model.hasWriteObjectData;

         fields = model.fields;

         primDataSize = model.primDataSize;

         numObjFields = model.numObjFields;

         if (cl != null) {

             localDesc = lookup(cl, true);

             if (localDesc.isProxy) {

                 throw new InvalidClassException(

                     "cannot bind non-proxy descriptor to a proxy class");

             }

             if (isEnum != localDesc.isEnum) {

                 throw new InvalidClassException(isEnum ?

                     "cannot bind enum descriptor to a non-enum class" :

                     "cannot bind non-enum descriptor to an enum class");

             }

             if (serializable == localDesc.serializable &&

                 !cl.isArray() &&

                 suid.longValue() != localDesc.getSerialVersionUID())

             {

                 throw new InvalidClassException(localDesc.name,

                     "local class incompatible: " +

                     "stream classdesc serialVersionUID = " + suid +

                     ", local class serialVersionUID = " +

                     localDesc.getSerialVersionUID());

             }

             if (!classNamesEqual(name, localDesc.name)) {

                 throw new InvalidClassException(localDesc.name,

                     "local class name incompatible with stream class " +

                     "name \"" + name + "\"");

             }

             if (!isEnum) {

                 if ((serializable == localDesc.serializable) &&

                     (externalizable != localDesc.externalizable))

                 {

                     throw new InvalidClassException(localDesc.name,

                         "Serializable incompatible with Externalizable");

                 }

                 if ((serializable != localDesc.serializable) ||

                     (externalizable != localDesc.externalizable) ||

                     !(serializable || externalizable))

                 {

                     deserializeEx = new InvalidClassException(localDesc.name,

                         "class invalid for deserialization");

                 }

             }

             cons = localDesc.cons;

             writeObjectMethod = localDesc.writeObjectMethod;

             readObjectMethod = localDesc.readObjectMethod;

             readObjectNoDataMethod = localDesc.readObjectNoDataMethod;

             writeReplaceMethod = localDesc.writeReplaceMethod;

             readResolveMethod = localDesc.readResolveMethod;

             if (deserializeEx == null) {

                 deserializeEx = localDesc.deserializeEx;

             }

         }

         // reassign to matched fields so as to reflect local unshared settings

         fields = null;

     }

     /**

      * Reads non-proxy class descriptor information from given input stream.

      * The resulting class descriptor is not fully functional; it can only be

      * used as input to the ObjectInputStream.resolveClass() and

      * ObjectStreamClass.initNonProxy() methods.

      */

     void readNonProxy(ObjectInputStream in)

         throws IOException, ClassNotFoundException

     {

         name = in.readUTF();

         suid = Long.valueOf(in.readLong());

         isProxy = false;

         byte flags = in.readByte();

         hasWriteObjectData =

             ((flags & ObjectStreamConstants.SC_WRITE_METHOD) != 0);

         hasBlockExternalData =

             ((flags & ObjectStreamConstants.SC_BLOCK_DATA) != 0);

         externalizable =

             ((flags & ObjectStreamConstants.SC_EXTERNALIZABLE) != 0);

         boolean sflag =

             ((flags & ObjectStreamConstants.SC_SERIALIZABLE) != 0);

         if (externalizable && sflag) {

             throw new InvalidClassException(

                 name, "serializable and externalizable flags conflict");

         }

         serializable = externalizable || sflag;

         isEnum = ((flags & ObjectStreamConstants.SC_ENUM) != 0);

         if (isEnum && suid.longValue() != 0L) {

             throw new InvalidClassException(name,

                 "enum descriptor has non-zero serialVersionUID: " + suid);

         }

         int numFields = in.readShort();

         if (isEnum && numFields != 0) {

             throw new InvalidClassException(name,

                 "enum descriptor has non-zero field count: " + numFields);

         }

         fields = (numFields > 0) ?

             new ObjectStreamField[numFields] : NO_FIELDS;

         for (int i = 0; i < numFields; i++) {

             char tcode = (char) in.readByte();

             String fname = in.readUTF();

             String signature = ((tcode == 'L') || (tcode == '[')) ?

                 in.readTypeString() : new String(new char[] { tcode });

             try {

                 fields[i] = new ObjectStreamField(fname, signature, false);

             } catch (RuntimeException e) {

                 throw (IOException) new InvalidClassException(name,

                     "invalid descriptor for field " + fname).initCause(e);

             }

         }

         computeFieldOffsets();

     }

     /**

      * Writes non-proxy class descriptor information to given output stream.

      */

     void writeNonProxy(ObjectOutputStream out) throws IOException {

         out.writeUTF(name);

         out.writeLong(getSerialVersionUID());

         byte flags = 0;

         if (externalizable) {

             flags |= ObjectStreamConstants.SC_EXTERNALIZABLE;

             int protocol = out.getProtocolVersion();

             if (protocol != ObjectStreamConstants.PROTOCOL_VERSION_1) {

                 flags |= ObjectStreamConstants.SC_BLOCK_DATA;

             }

         } else if (serializable) {

             flags |= ObjectStreamConstants.SC_SERIALIZABLE;

         }

         if (hasWriteObjectData) {

             flags |= ObjectStreamConstants.SC_WRITE_METHOD;

         }

         if (isEnum) {

             flags |= ObjectStreamConstants.SC_ENUM;

         }

         out.writeByte(flags);

         out.writeShort(fields.length);

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

             ObjectStreamField f = fields[i];

             out.writeByte(f.getTypeCode());

             out.writeUTF(f.getName());

             if (!f.isPrimitive()) {

                 out.writeTypeString(f.getTypeString());

             }

         }

     }

     /**

      * Returns ClassNotFoundException (if any) thrown while attempting to

      * resolve local class corresponding to this class descriptor.

      */

     ClassNotFoundException getResolveException() {

         return resolveEx;

     }

     /**

      * Throws an InvalidClassException if object instances referencing this

      * class descriptor should not be allowed to deserialize.  This method does

      * not apply to deserialization of enum constants.

      */

     void checkDeserialize() throws InvalidClassException {

         if (deserializeEx != null) {

             InvalidClassException ice =

                 new InvalidClassException(deserializeEx.classname,

                                           deserializeEx.getMessage());

             ice.initCause(deserializeEx);

             throw ice;

         }

     }

     /**

      * Throws an InvalidClassException if objects whose class is represented by

      * this descriptor should not be allowed to serialize.  This method does

      * not apply to serialization of enum constants.

      */

     void checkSerialize() throws InvalidClassException {

         if (serializeEx != null) {

             InvalidClassException ice =

                 new InvalidClassException(serializeEx.classname,

                                           serializeEx.getMessage());

             ice.initCause(serializeEx);

             throw ice;

         }

     }

     /**

      * Throws an InvalidClassException if objects whose class is represented by

      * this descriptor should not be permitted to use default serialization

      * (e.g., if the class declares serializable fields that do not correspond

      * to actual fields, and hence must use the GetField API).  This method

      * does not apply to deserialization of enum constants.

      */

     void checkDefaultSerialize() throws InvalidClassException {

         if (defaultSerializeEx != null) {

             InvalidClassException ice =

                 new InvalidClassException(defaultSerializeEx.classname,

                                           defaultSerializeEx.getMessage());

             ice.initCause(defaultSerializeEx);

             throw ice;

         }

     }

     /**

      * Returns superclass descriptor.  Note that on the receiving side, the

      * superclass descriptor may be bound to a class that is not a superclass

      * of the subclass descriptor's bound class.

      */

     ObjectStreamClass getSuperDesc() {

         return superDesc;

     }

     /**

      * Returns the "local" class descriptor for the class associated with this

      * class descriptor (i.e., the result of

      * ObjectStreamClass.lookup(this.forClass())) or null if there is no class

      * associated with this descriptor.

      */

     ObjectStreamClass getLocalDesc() {

         return localDesc;

     }

     /**

      * Returns arrays of ObjectStreamFields representing the serializable

      * fields of the represented class.  If copy is true, a clone of this class

      * descriptor's field array is returned, otherwise the array itself is

      * returned.

      */

     ObjectStreamField[] getFields(boolean copy) {

         return copy ? fields.clone() : fields;

     }

     /**

      * Looks up a serializable field of the represented class by name and type.

      * A specified type of null matches all types, Object.class matches all

      * non-primitive types, and any other non-null type matches assignable

      * types only.  Returns matching field, or null if no match found.

      */

     ObjectStreamField getField(String name, Class<?> type) {

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

             ObjectStreamField f = fields[i];

             if (f.getName().equals(name)) {

                 if (type == null ||

                     (type == Object.class && !f.isPrimitive()))

                 {

                     return f;

                 }

                 Class<?> ftype = f.getType();

                 if (ftype != null && type.isAssignableFrom(ftype)) {

                     return f;

                 }

             }

         }

         return null;

     }

     /**

      * Returns true if class descriptor represents a dynamic proxy class, false

      * otherwise.

      */

     boolean isProxy() {

         return isProxy;

     }

     /**

      * Returns true if class descriptor represents an enum type, false

      * otherwise.

      */

     boolean isEnum() {

         return isEnum;

     }

     /**

      * Returns true if represented class implements Externalizable, false

      * otherwise.

      */

     boolean isExternalizable() {

         return externalizable;

     }

     /**

      * Returns true if represented class implements Serializable, false

      * otherwise.

      */

     boolean isSerializable() {

         return serializable;

     }

     /**

      * Returns true if class descriptor represents externalizable class that

      * has written its data in 1.2 (block data) format, false otherwise.

      */

     boolean hasBlockExternalData() {

         return hasBlockExternalData;

     }

     /**

      * Returns true if class descriptor represents serializable (but not

      * externalizable) class which has written its data via a custom

      * writeObject() method, false otherwise.

      */

     boolean hasWriteObjectData() {

         return hasWriteObjectData;

     }

     /**

      * Returns true if represented class is serializable/externalizable and can

      * be instantiated by the serialization runtime--i.e., if it is

      * externalizable and defines a public no-arg constructor, or if it is

      * non-externalizable and its first non-serializable superclass defines an

      * accessible no-arg constructor.  Otherwise, returns false.

      */

     boolean isInstantiable() {

         return (cons != null);

     }

     /**

      * Returns true if represented class is serializable (but not

      * externalizable) and defines a conformant writeObject method.  Otherwise,

      * returns false.

      */

     boolean hasWriteObjectMethod() {

         return (writeObjectMethod != null);

     }

     /**

      * Returns true if represented class is serializable (but not

      * externalizable) and defines a conformant readObject method.  Otherwise,

      * returns false.

      */

     boolean hasReadObjectMethod() {

         return (readObjectMethod != null);

     }

     /**

      * Returns true if represented class is serializable (but not

      * externalizable) and defines a conformant readObjectNoData method.

      * Otherwise, returns false.

      */

     boolean hasReadObjectNoDataMethod() {

         return (readObjectNoDataMethod != null);

     }

     /**

      * Returns true if represented class is serializable or externalizable and

      * defines a conformant writeReplace method.  Otherwise, returns false.

      */

     boolean hasWriteReplaceMethod() {

         return (writeReplaceMethod != null);

     }

     /**

      * Returns true if represented class is serializable or externalizable and

      * defines a conformant readResolve method.  Otherwise, returns false.

      */

     boolean hasReadResolveMethod() {

         return (readResolveMethod != null);

     }

     /**

      * Creates a new instance of the represented class.  If the class is

      * externalizable, invokes its public no-arg constructor; otherwise, if the

      * class is serializable, invokes the no-arg constructor of the first

      * non-serializable superclass.  Throws UnsupportedOperationException if

      * this class descriptor is not associated with a class, if the associated

      * class is non-serializable or if the appropriate no-arg constructor is

      * inaccessible/unavailable.

      */

     Object newInstance()

         throws InstantiationException, InvocationTargetException,

                UnsupportedOperationException

     {

         if (cons != null) {

             try {

                 return cons.newInstance();

             } catch (IllegalAccessException ex) {

                 // should not occur, as access checks have been suppressed

                 throw new InternalError();

             }

         } else {

             throw new UnsupportedOperationException();

         }

     }

     /**

      * Invokes the writeObject method of the represented serializable class.

      * Throws UnsupportedOperationException if this class descriptor is not

      * associated with a class, or if the class is externalizable,

      * non-serializable or does not define writeObject.

      */

     void invokeWriteObject(Object obj, ObjectOutputStream out)

         throws IOException, UnsupportedOperationException

     {

         if (writeObjectMethod != null) {

             try {

                 writeObjectMethod.invoke(obj, new Object[]{ out });

             } catch (InvocationTargetException ex) {

                 Throwable th = ex.getTargetException();

                 if (th instanceof IOException) {

                     throw (IOException) th;

                 } else {

                     throwMiscException(th);

                 }

             } catch (IllegalAccessException ex) {

                 // should not occur, as access checks have been suppressed

                 throw new InternalError();

             }

         } else {

             throw new UnsupportedOperationException();

         }

     }

     /**

      * Invokes the readObject method of the represented serializable class.

      * Throws UnsupportedOperationException if this class descriptor is not

      * associated with a class, or if the class is externalizable,

      * non-serializable or does not define readObject.

      */

     void invokeReadObject(Object obj, ObjectInputStream in)

         throws ClassNotFoundException, IOException,

                UnsupportedOperationException

     {

         if (readObjectMethod != null) {

             try {

                 readObjectMethod.invoke(obj, new Object[]{ in });

             } catch (InvocationTargetException ex) {

                 Throwable th = ex.getTargetException();

                 if (th instanceof ClassNotFoundException) {

                     throw (ClassNotFoundException) th;

                 } else if (th instanceof IOException) {

                     throw (IOException) th;

                 } else {

                     throwMiscException(th);

                 }

             } catch (IllegalAccessException ex) {

                 // should not occur, as access checks have been suppressed

                 throw new InternalError();

             }

         } else {

             throw new UnsupportedOperationException();

         }

     }

     /**

      * Invokes the readObjectNoData method of the represented serializable

      * class.  Throws UnsupportedOperationException if this class descriptor is

      * not associated with a class, or if the class is externalizable,

      * non-serializable or does not define readObjectNoData.

      */

     void invokeReadObjectNoData(Object obj)

         throws IOException, UnsupportedOperationException

     {

         if (readObjectNoDataMethod != null) {

             try {

                 readObjectNoDataMethod.invoke(obj, (Object[]) null);

             } catch (InvocationTargetException ex) {

                 Throwable th = ex.getTargetException();

                 if (th instanceof ObjectStreamException) {

                     throw (ObjectStreamException) th;

                 } else {

                     throwMiscException(th);

                 }

             } catch (IllegalAccessException ex) {

                 // should not occur, as access checks have been suppressed

                 throw new InternalError();

             }

         } else {

             throw new UnsupportedOperationException();

         }

     }

     /**

      * Invokes the writeReplace method of the represented serializable class and

      * returns the result.  Throws UnsupportedOperationException if this class

      * descriptor is not associated with a class, or if the class is

      * non-serializable or does not define writeReplace.

      */

     Object invokeWriteReplace(Object obj)

         throws IOException, UnsupportedOperationException

     {

         if (writeReplaceMethod != null) {

             try {

                 return writeReplaceMethod.invoke(obj, (Object[]) null);

             } catch (InvocationTargetException ex) {

                 Throwable th = ex.getTargetException();

                 if (th instanceof ObjectStreamException) {

                     throw (ObjectStreamException) th;

                 } else {

                     throwMiscException(th);

                     throw new InternalError();  // never reached

                 }

             } catch (IllegalAccessException ex) {

                 // should not occur, as access checks have been suppressed

                 throw new InternalError();

             }

         } else {

             throw new UnsupportedOperationException();

         }

     }

     /**

      * Invokes the readResolve method of the represented serializable class and

      * returns the result.  Throws UnsupportedOperationException if this class

      * descriptor is not associated with a class, or if the class is

      * non-serializable or does not define readResolve.

      */

     Object invokeReadResolve(Object obj)

         throws IOException, UnsupportedOperationException

     {

         if (readResolveMethod != null) {

             try {

                 return readResolveMethod.invoke(obj, (Object[]) null);

             } catch (InvocationTargetException ex) {

                 Throwable th = ex.getTargetException();

                 if (th instanceof ObjectStreamException) {

                     throw (ObjectStreamException) th;

                 } else {

                     throwMiscException(th);

                     throw new InternalError();  // never reached

                 }

             } catch (IllegalAccessException ex) {

                 // should not occur, as access checks have been suppressed

                 throw new InternalError();

             }

         } else {

             throw new UnsupportedOperationException();

         }

     }

     /**

      * Class representing the portion of an object's serialized form allotted

      * to data described by a given class descriptor.  If "hasData" is false,

      * the object's serialized form does not contain data associated with the

      * class descriptor.

      */

     static class ClassDataSlot {

         /** class descriptor "occupying" this slot */

         final ObjectStreamClass desc;

         /** true if serialized form includes data for this slot's descriptor */

         final boolean hasData;

         ClassDataSlot(ObjectStreamClass desc, boolean hasData) {

             this.desc = desc;

             this.hasData = hasData;

         }

     }

     /**

      * Returns array of ClassDataSlot instances representing the data layout

      * (including superclass data) for serialized objects described by this

      * class descriptor.  ClassDataSlots are ordered by inheritance with those

      * containing "higher" superclasses appearing first.  The final

      * ClassDataSlot contains a reference to this descriptor.

      */

     ClassDataSlot[] getClassDataLayout() throws InvalidClassException {

         // REMIND: synchronize instead of relying on volatile?

         if (dataLayout == null) {

             dataLayout = getClassDataLayout0();

         }

         return dataLayout;

     }

     private ClassDataSlot[] getClassDataLayout0()

         throws InvalidClassException

     {

         ArrayList<ClassDataSlot> slots = new ArrayList<>();

         Class<?> start = cl, end = cl;

         // locate closest non-serializable superclass

         while (end != null && Serializable.class.isAssignableFrom(end)) {

             end = end.getSuperclass();

         }

         for (ObjectStreamClass d = this; d != null; d = d.superDesc) {

             // search up inheritance hierarchy for class with matching name

             String searchName = (d.cl != null) ? d.cl.getName() : d.name;

             Class<?> match = null;

             for (Class<?> c = start; c != end; c = c.getSuperclass()) {

                 if (searchName.equals(c.getName())) {

                     match = c;

                     break;

                 }

             }

             // add "no data" slot for each unmatched class below match

             if (match != null) {

                 for (Class<?> c = start; c != match; c = c.getSuperclass()) {

                     slots.add(new ClassDataSlot(

                         ObjectStreamClass.lookup(c, true), false));

                 }

                 start = match.getSuperclass();

             }

             // record descriptor/class pairing

             slots.add(new ClassDataSlot(d.getVariantFor(match), true));

         }

         // add "no data" slot for any leftover unmatched classes

         for (Class<?> c = start; c != end; c = c.getSuperclass()) {

             slots.add(new ClassDataSlot(

                 ObjectStreamClass.lookup(c, true), false));

         }

         // order slots from superclass -> subclass

         Collections.reverse(slots);

         return slots.toArray(new ClassDataSlot[slots.size()]);

     }

     /**

      * Returns aggregate size (in bytes) of marshalled primitive field values

      * for represented class.

      */

     int getPrimDataSize() {

         return primDataSize;

     }

     /**

      * Returns number of non-primitive serializable fields of represented

      * class.

      */

     int getNumObjFields() {

         return numObjFields;

     }

     /**

      * Fetches the serializable primitive field values of object obj and

      * marshals them into byte array buf starting at offset 0.  It is the

      * responsibility of the caller to ensure that obj is of the proper type if

      * non-null.

      */

     void getPrimFieldValues(Object obj, byte[] buf) {

     }

     /**

      * Sets the serializable primitive fields of object obj using values

      * unmarshalled from byte array buf starting at offset 0.  It is the

      * responsibility of the caller to ensure that obj is of the proper type if

      * non-null.

      */

     void setPrimFieldValues(Object obj, byte[] buf) {

     }

     /**

      * Fetches the serializable object field values of object obj and stores

      * them in array vals starting at offset 0.  It is the responsibility of

      * the caller to ensure that obj is of the proper type if non-null.

      */

     void getObjFieldValues(Object obj, Object[] vals) {

     }

     /**

      * Sets the serializable object fields of object obj using values from

      * array vals starting at offset 0.  It is the responsibility of the caller

      * to ensure that obj is of the proper type if non-null.

      */

     void setObjFieldValues(Object obj, Object[] vals) {

     }

     /**

      * Calculates and sets serializable field offsets, as well as primitive

      * data size and object field count totals.  Throws InvalidClassException

      * if fields are illegally ordered.

      */

     private void computeFieldOffsets() throws InvalidClassException {

         primDataSize = 0;

         numObjFields = 0;

         int firstObjIndex = -1;

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

             ObjectStreamField f = fields[i];

             switch (f.getTypeCode()) {

                 case 'Z':

                 case 'B':

                     f.setOffset(primDataSize++);

                     break;

                 case 'C':

                 case 'S':

                     f.setOffset(primDataSize);

                     primDataSize += 2;

                     break;

                 case 'I':

                 case 'F':

                     f.setOffset(primDataSize);

                     primDataSize += 4;

                     break;

                 case 'J':

                 case 'D':

                     f.setOffset(primDataSize);

                     primDataSize += 8;

                     break;

                 case '[':

                 case 'L':

                     f.setOffset(numObjFields++);

                     if (firstObjIndex == -1) {

                         firstObjIndex = i;

                     }

                     break;

                 default:

                     throw new InternalError();

             }

         }

         if (firstObjIndex != -1 &&

             firstObjIndex + numObjFields != fields.length)

         {

             throw new InvalidClassException(name, "illegal field order");

         }

     }

     /**

      * If given class is the same as the class associated with this class

      * descriptor, returns reference to this class descriptor.  Otherwise,

      * returns variant of this class descriptor bound to given class.

      */

     private ObjectStreamClass getVariantFor(Class<?> cl)

         throws InvalidClassException

     {

         if (this.cl == cl) {

             return this;

         }

         ObjectStreamClass desc = new ObjectStreamClass();

         if (isProxy) {

             desc.initProxy(cl, null, superDesc);

         } else {

             desc.initNonProxy(this, cl, null, superDesc);

         }

         return desc;

     }

     /**

      * Returns public no-arg constructor of given class, or null if none found.

      * Access checks are disabled on the returned constructor (if any), since

      * the defining class may still be non-public.

      */

     private static Constructor getExternalizableConstructor(Class<?> cl) {

         throw new SecurityException();

     }

     /**

      * Returns subclass-accessible no-arg constructor of first non-serializable

      * superclass, or null if none found.  Access checks are disabled on the

      * returned constructor (if any).

      */

     private static Constructor getSerializableConstructor(Class<?> cl) {

         Class<?> initCl = cl;

         while (Serializable.class.isAssignableFrom(initCl)) {

             if ((initCl = initCl.getSuperclass()) == null) {

                 return null;

             }

         }

         throw new SecurityException();

     }

     /**

      * Returns non-static, non-abstract method with given signature provided it

      * is defined by or accessible (via inheritance) by the given class, or

      * null if no match found.  Access checks are disabled on the returned

      * method (if any).

      */

     private static Method getInheritableMethod(Class<?> cl, String name,

                                                Class<?>[] argTypes,

                                                Class<?> returnType)

     {

         throw new SecurityException();

     }

     /**

      * Returns non-static private method with given signature defined by given

      * class, or null if none found.  Access checks are disabled on the

      * returned method (if any).

      */

     private static Method getPrivateMethod(Class<?> cl, String name,

                                            Class<?>[] argTypes,

                                            Class<?> returnType)

     {

         throw new SecurityException();

     }

     /**

      * Returns true if classes are defined in the same runtime package, false

      * otherwise.

      */

     private static boolean packageEquals(Class<?> cl1, Class<?> cl2) {

         return (cl1.getClassLoader() == cl2.getClassLoader() &&

                 getPackageName(cl1).equals(getPackageName(cl2)));

     }

     /**

      * Returns package name of given class.

      */

     private static String getPackageName(Class<?> cl) {

         String s = cl.getName();

         int i = s.lastIndexOf('[');

         if (i >= 0) {

             s = s.substring(i + 2);

         }

         i = s.lastIndexOf('.');

         return (i >= 0) ? s.substring(0, i) : "";

     }

     /**

      * Compares class names for equality, ignoring package names.  Returns true

      * if class names equal, false otherwise.

      */

     private static boolean classNamesEqual(String name1, String name2) {

         name1 = name1.substring(name1.lastIndexOf('.') + 1);

         name2 = name2.substring(name2.lastIndexOf('.') + 1);

         return name1.equals(name2);

     }

     /**

      * Returns JVM type signature for given class.

      */

     private static String getClassSignature(Class<?> cl) {

         StringBuilder sbuf = new StringBuilder();

         while (cl.isArray()) {

             sbuf.append('[');

             cl = cl.getComponentType();

         }

         if (cl.isPrimitive()) {

             if (cl == Integer.TYPE) {

                 sbuf.append('I');

             } else if (cl == Byte.TYPE) {

                 sbuf.append('B');

             } else if (cl == Long.TYPE) {

                 sbuf.append('J');

             } else if (cl == Float.TYPE) {

                 sbuf.append('F');

             } else if (cl == Double.TYPE) {

                 sbuf.append('D');

             } else if (cl == Short.TYPE) {

                 sbuf.append('S');

             } else if (cl == Character.TYPE) {

                 sbuf.append('C');

             } else if (cl == Boolean.TYPE) {

                 sbuf.append('Z');

             } else if (cl == Void.TYPE) {

                 sbuf.append('V');

             } else {

                 throw new InternalError();

             }

         } else {

             sbuf.append('L' + cl.getName().replace('.', '/') + ';');

         }

         return sbuf.toString();

     }

     /**

      * Returns JVM type signature for given list of parameters and return type.

      */

     private static String getMethodSignature(Class<?>[] paramTypes,

                                              Class<?> retType)

     {

         StringBuilder sbuf = new StringBuilder();

         sbuf.append('(');

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

             sbuf.append(getClassSignature(paramTypes[i]));

         }

         sbuf.append(')');

         sbuf.append(getClassSignature(retType));

         return sbuf.toString();

     }

     /**

      * Convenience method for throwing an exception that is either a

      * RuntimeException, Error, or of some unexpected type (in which case it is

      * wrapped inside an IOException).

      */

     private static void throwMiscException(Throwable th) throws IOException {

         if (th instanceof RuntimeException) {

             throw (RuntimeException) th;

         } else if (th instanceof Error) {

             throw (Error) th;

         } else {

             IOException ex = new IOException("unexpected exception type");

             ex.initCause(th);

             throw ex;

         }

     }

     /**

      * Returns ObjectStreamField array describing the serializable fields of

      * the given class.  Serializable fields backed by an actual field of the

      * class are represented by ObjectStreamFields with corresponding non-null

      * Field objects.  Throws InvalidClassException if the (explicitly

      * declared) serializable fields are invalid.

      */

     private static ObjectStreamField[] getSerialFields(Class<?> cl)

         throws InvalidClassException

     {

         ObjectStreamField[] fields;

         if (Serializable.class.isAssignableFrom(cl) &&

             !Externalizable.class.isAssignableFrom(cl) &&

             !Proxy.isProxyClass(cl) &&

             !cl.isInterface())

         {

             if ((fields = getDeclaredSerialFields(cl)) == null) {

                 fields = getDefaultSerialFields(cl);

             }

             Arrays.sort(fields);

         } else {

             fields = NO_FIELDS;

         }

         return fields;

     }

     /**

      * Returns serializable fields of given class as defined explicitly by a

      * "serialPersistentFields" field, or null if no appropriate

      * "serialPersistentFields" field is defined.  Serializable fields backed

      * by an actual field of the class are represented by ObjectStreamFields

      * with corresponding non-null Field objects.  For compatibility with past

      * releases, a "serialPersistentFields" field with a null value is

      * considered equivalent to not declaring "serialPersistentFields".  Throws

      * InvalidClassException if the declared serializable fields are

      * invalid--e.g., if multiple fields share the same name.

      */

     private static ObjectStreamField[] getDeclaredSerialFields(Class<?> cl)

         throws InvalidClassException

     {

         throw new SecurityException();

     }

     /**

      * Returns array of ObjectStreamFields corresponding to all non-static

      * non-transient fields declared by given class.  Each ObjectStreamField

      * contains a Field object for the field it represents.  If no default

      * serializable fields exist, NO_FIELDS is returned.

      */

     private static ObjectStreamField[] getDefaultSerialFields(Class<?> cl) {

         throw new SecurityException();

     }

     /**

      * Returns explicit serial version UID value declared by given class, or

      * null if none.

      */

     private static Long getDeclaredSUID(Class<?> cl) {

         return null;

     }

     /**

      * Computes the default serial version UID value for the given class.

      */

     private static long computeDefaultSUID(Class<?> cl) {

         throw new SecurityException();

     }

 }