/*

  * Copyright (c) 1996, 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

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  * questions.

  */

 package java.io;

 import java.io.ObjectStreamClass.WeakClassKey;

 import java.lang.ref.ReferenceQueue;

 import java.security.AccessController;

 import java.security.PrivilegedAction;

 import java.util.ArrayList;

 import java.util.Arrays;

 import java.util.List;

 import java.util.concurrent.ConcurrentHashMap;

 import java.util.concurrent.ConcurrentMap;

 import static java.io.ObjectStreamClass.processQueue;

 import java.io.SerialCallbackContext;

 /**

  * An ObjectOutputStream writes primitive data types and graphs of Java objects

  * to an OutputStream.  The objects can be read (reconstituted) using an

  * ObjectInputStream.  Persistent storage of objects can be accomplished by

  * using a file for the stream.  If the stream is a network socket stream, the

  * objects can be reconstituted on another host or in another process.

  *

  * <p>Only objects that support the java.io.Serializable interface can be

  * written to streams.  The class of each serializable object is encoded

  * including the class name and signature of the class, the values of the

  * object's fields and arrays, and the closure of any other objects referenced

  * from the initial objects.

  *

  * <p>The method writeObject is used to write an object to the stream.  Any

  * object, including Strings and arrays, is written with writeObject. Multiple

  * objects or primitives can be written to the stream.  The objects must be

  * read back from the corresponding ObjectInputstream with the same types and

  * in the same order as they were written.

  *

  * <p>Primitive data types can also be written to the stream using the

  * appropriate methods from DataOutput. Strings can also be written using the

  * writeUTF method.

  *

  * <p>The default serialization mechanism for an object writes the class of the

  * object, the class signature, and the values of all non-transient and

  * non-static fields.  References to other objects (except in transient or

  * static fields) cause those objects to be written also. Multiple references

  * to a single object are encoded using a reference sharing mechanism so that

  * graphs of objects can be restored to the same shape as when the original was

  * written.

  *

  * <p>For example to write an object that can be read by the example in

  * ObjectInputStream:

  * <br>

  * <pre>

  *      FileOutputStream fos = new FileOutputStream("t.tmp");

  *      ObjectOutputStream oos = new ObjectOutputStream(fos);

  *

  *      oos.writeInt(12345);

  *      oos.writeObject("Today");

  *      oos.writeObject(new Date());

  *

  *      oos.close();

  * </pre>

  *

  * <p>Classes that require special handling during the serialization and

  * deserialization process must implement special methods with these exact

  * signatures:

  * <br>

  * <pre>

  * private void readObject(java.io.ObjectInputStream stream)

  *     throws IOException, ClassNotFoundException;

  * private void writeObject(java.io.ObjectOutputStream stream)

  *     throws IOException

  * private void readObjectNoData()

  *     throws ObjectStreamException;

  * </pre>

  *

  * <p>The writeObject method is responsible for writing the state of the object

  * for its particular class so that the corresponding readObject method can

  * restore it.  The method does not need to concern itself with the state

  * belonging to the object's superclasses or subclasses.  State is saved by

  * writing the individual fields to the ObjectOutputStream using the

  * writeObject method or by using the methods for primitive data types

  * supported by DataOutput.

  *

  * <p>Serialization does not write out the fields of any object that does not

  * implement the java.io.Serializable interface.  Subclasses of Objects that

  * are not serializable can be serializable. In this case the non-serializable

  * class must have a no-arg constructor to allow its fields to be initialized.

  * In this case it is the responsibility of the subclass to save and restore

  * the state of the non-serializable class. It is frequently the case that the

  * fields of that class are accessible (public, package, or protected) or that

  * there are get and set methods that can be used to restore the state.

  *

  * <p>Serialization of an object can be prevented by implementing writeObject

  * and readObject methods that throw the NotSerializableException.  The

  * exception will be caught by the ObjectOutputStream and abort the

  * serialization process.

  *

  * <p>Implementing the Externalizable interface allows the object to assume

  * complete control over the contents and format of the object's serialized

  * form.  The methods of the Externalizable interface, writeExternal and

  * readExternal, are called to save and restore the objects state.  When

  * implemented by a class they can write and read their own state using all of

  * the methods of ObjectOutput and ObjectInput.  It is the responsibility of

  * the objects to handle any versioning that occurs.

  *

  * <p>Enum constants are serialized differently than ordinary serializable or

  * externalizable objects.  The serialized form of an enum constant consists

  * solely of its name; field values of the constant are not transmitted.  To

  * serialize an enum constant, ObjectOutputStream writes the string returned by

  * the constant's name method.  Like other serializable or externalizable

  * objects, enum constants can function as the targets of back references

  * appearing subsequently in the serialization stream.  The process by which

  * enum constants are serialized cannot be customized; any class-specific

  * writeObject and writeReplace methods defined by enum types are ignored

  * during serialization.  Similarly, any serialPersistentFields or

  * serialVersionUID field declarations are also ignored--all enum types have a

  * fixed serialVersionUID of 0L.

  *

  * <p>Primitive data, excluding serializable fields and externalizable data, is

  * written to the ObjectOutputStream in block-data records. A block data record

  * is composed of a header and data. The block data header consists of a marker

  * and the number of bytes to follow the header.  Consecutive primitive data

  * writes are merged into one block-data record.  The blocking factor used for

  * a block-data record will be 1024 bytes.  Each block-data record will be

  * filled up to 1024 bytes, or be written whenever there is a termination of

  * block-data mode.  Calls to the ObjectOutputStream methods writeObject,

  * defaultWriteObject and writeFields initially terminate any existing

  * block-data record.

  *

  * @author      Mike Warres

  * @author      Roger Riggs

  * @see java.io.DataOutput

  * @see java.io.ObjectInputStream

  * @see java.io.Serializable

  * @see java.io.Externalizable

  * @see <a href="../../../platform/serialization/spec/output.html">Object Serialization Specification, Section 2, Object Output Classes</a>

  * @since       JDK1.1

  */

 public class ObjectOutputStream

     extends OutputStream implements ObjectOutput, ObjectStreamConstants

 {

     private static class Caches {

         /** cache of subclass security audit results */

         static final ConcurrentMap<WeakClassKey,Boolean> subclassAudits =

             new ConcurrentHashMap<>();

         /** queue for WeakReferences to audited subclasses */

         static final ReferenceQueue<Class<?>> subclassAuditsQueue =

             new ReferenceQueue<>();

     }

     /** filter stream for handling block data conversion */

     private final BlockDataOutputStream bout;

     /** obj -> wire handle map */

     private final HandleTable handles;

     /** obj -> replacement obj map */

     private final ReplaceTable subs;

     /** stream protocol version */

     private int protocol = PROTOCOL_VERSION_2;

     /** recursion depth */

     private int depth;

     /** buffer for writing primitive field values */

     private byte[] primVals;

     /** if true, invoke writeObjectOverride() instead of writeObject() */

     private final boolean enableOverride;

     /** if true, invoke replaceObject() */

     private boolean enableReplace;

     // values below valid only during upcalls to writeObject()/writeExternal()

     /**

      * Context during upcalls to class-defined writeObject methods; holds

      * object currently being serialized and descriptor for current class.

      * Null when not during writeObject upcall.

      */

     private SerialCallbackContext curContext;

     /** current PutField object */

     private PutFieldImpl curPut;

     /** custom storage for debug trace info */

     private final DebugTraceInfoStack debugInfoStack;

     /**

      * value of "sun.io.serialization.extendedDebugInfo" property,

      * as true or false for extended information about exception's place

      */

     private static final boolean extendedDebugInfo =

         java.security.AccessController.doPrivileged(

             new sun.security.action.GetBooleanAction(

                 "sun.io.serialization.extendedDebugInfo")).booleanValue();

     /**

      * Creates an ObjectOutputStream that writes to the specified OutputStream.

      * This constructor writes the serialization stream header to the

      * underlying stream; callers may wish to flush the stream immediately to

      * ensure that constructors for receiving ObjectInputStreams will not block

      * when reading the header.

      *

      * <p>If a security manager is installed, this constructor will check for

      * the "enableSubclassImplementation" SerializablePermission when invoked

      * directly or indirectly by the constructor of a subclass which overrides

      * the ObjectOutputStream.putFields or ObjectOutputStream.writeUnshared

      * methods.

      *

      * @param   out output stream to write to

      * @throws  IOException if an I/O error occurs while writing stream header

      * @throws  SecurityException if untrusted subclass illegally overrides

      *          security-sensitive methods

      * @throws  NullPointerException if <code>out</code> is <code>null</code>

      * @since   1.4

      * @see     ObjectOutputStream#ObjectOutputStream()

      * @see     ObjectOutputStream#putFields()

      * @see     ObjectInputStream#ObjectInputStream(InputStream)

      */

     public ObjectOutputStream(OutputStream out) throws IOException {

         verifySubclass();

         bout = new BlockDataOutputStream(out);

         handles = new HandleTable(10, (float) 3.00);

         subs = new ReplaceTable(10, (float) 3.00);

         enableOverride = false;

         writeStreamHeader();

         bout.setBlockDataMode(true);

         if (extendedDebugInfo) {

             debugInfoStack = new DebugTraceInfoStack();

         } else {

             debugInfoStack = null;

         }

     }

     /**

      * Provide a way for subclasses that are completely reimplementing

      * ObjectOutputStream to not have to allocate private data just used by

      * this implementation of ObjectOutputStream.

      *

      * <p>If there is a security manager installed, this method first calls the

      * security manager's <code>checkPermission</code> method with a

      * <code>SerializablePermission("enableSubclassImplementation")</code>

      * permission to ensure it's ok to enable subclassing.

      *

      * @throws  SecurityException if a security manager exists and its

      *          <code>checkPermission</code> method denies enabling

      *          subclassing.

      * @see SecurityManager#checkPermission

      * @see java.io.SerializablePermission

      */

     protected ObjectOutputStream() throws IOException, SecurityException {

         SecurityManager sm = System.getSecurityManager();

         if (sm != null) {

             sm.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);

         }

         bout = null;

         handles = null;

         subs = null;

         enableOverride = true;

         debugInfoStack = null;

     }

     /**

      * Specify stream protocol version to use when writing the stream.

      *

      * <p>This routine provides a hook to enable the current version of

      * Serialization to write in a format that is backwards compatible to a

      * previous version of the stream format.

      *

      * <p>Every effort will be made to avoid introducing additional

      * backwards incompatibilities; however, sometimes there is no

      * other alternative.

      *

      * @param   version use ProtocolVersion from java.io.ObjectStreamConstants.

      * @throws  IllegalStateException if called after any objects

      *          have been serialized.

      * @throws  IllegalArgumentException if invalid version is passed in.

      * @throws  IOException if I/O errors occur

      * @see java.io.ObjectStreamConstants#PROTOCOL_VERSION_1

      * @see java.io.ObjectStreamConstants#PROTOCOL_VERSION_2

      * @since   1.2

      */

     public void useProtocolVersion(int version) throws IOException {

         if (handles.size() != 0) {

             // REMIND: implement better check for pristine stream?

             throw new IllegalStateException("stream non-empty");

         }

         switch (version) {

             case PROTOCOL_VERSION_1:

             case PROTOCOL_VERSION_2:

                 protocol = version;

                 break;

             default:

                 throw new IllegalArgumentException(

                     "unknown version: " + version);

         }

     }

     /**

      * Write the specified object to the ObjectOutputStream.  The class of the

      * object, the signature of the class, and the values of the non-transient

      * and non-static fields of the class and all of its supertypes are

      * written.  Default serialization for a class can be overridden using the

      * writeObject and the readObject methods.  Objects referenced by this

      * object are written transitively so that a complete equivalent graph of

      * objects can be reconstructed by an ObjectInputStream.

      *

      * <p>Exceptions are thrown for problems with the OutputStream and for

      * classes that should not be serialized.  All exceptions are fatal to the

      * OutputStream, which is left in an indeterminate state, and it is up to

      * the caller to ignore or recover the stream state.

      *

      * @throws  InvalidClassException Something is wrong with a class used by

      *          serialization.

      * @throws  NotSerializableException Some object to be serialized does not

      *          implement the java.io.Serializable interface.

      * @throws  IOException Any exception thrown by the underlying

      *          OutputStream.

      */

     public final void writeObject(Object obj) throws IOException {

         if (enableOverride) {

             writeObjectOverride(obj);

             return;

         }

         try {

             writeObject0(obj, false);

         } catch (IOException ex) {

             if (depth == 0) {

                 writeFatalException(ex);

             }

             throw ex;

         }

     }

     /**

      * Method used by subclasses to override the default writeObject method.

      * This method is called by trusted subclasses of ObjectInputStream that

      * constructed ObjectInputStream using the protected no-arg constructor.

      * The subclass is expected to provide an override method with the modifier

      * "final".

      *

      * @param   obj object to be written to the underlying stream

      * @throws  IOException if there are I/O errors while writing to the

      *          underlying stream

      * @see #ObjectOutputStream()

      * @see #writeObject(Object)

      * @since 1.2

      */

     protected void writeObjectOverride(Object obj) throws IOException {

     }

     /**

      * Writes an "unshared" object to the ObjectOutputStream.  This method is

      * identical to writeObject, except that it always writes the given object

      * as a new, unique object in the stream (as opposed to a back-reference

      * pointing to a previously serialized instance).  Specifically:

      * <ul>

      *   <li>An object written via writeUnshared is always serialized in the

      *       same manner as a newly appearing object (an object that has not

      *       been written to the stream yet), regardless of whether or not the

      *       object has been written previously.

      *

      *   <li>If writeObject is used to write an object that has been previously

      *       written with writeUnshared, the previous writeUnshared operation

      *       is treated as if it were a write of a separate object.  In other

      *       words, ObjectOutputStream will never generate back-references to

      *       object data written by calls to writeUnshared.

      * </ul>

      * While writing an object via writeUnshared does not in itself guarantee a

      * unique reference to the object when it is deserialized, it allows a

      * single object to be defined multiple times in a stream, so that multiple

      * calls to readUnshared by the receiver will not conflict.  Note that the

      * rules described above only apply to the base-level object written with

      * writeUnshared, and not to any transitively referenced sub-objects in the

      * object graph to be serialized.

      *

      * <p>ObjectOutputStream subclasses which override this method can only be

      * constructed in security contexts possessing the

      * "enableSubclassImplementation" SerializablePermission; any attempt to

      * instantiate such a subclass without this permission will cause a

      * SecurityException to be thrown.

      *

      * @param   obj object to write to stream

      * @throws  NotSerializableException if an object in the graph to be

      *          serialized does not implement the Serializable interface

      * @throws  InvalidClassException if a problem exists with the class of an

      *          object to be serialized

      * @throws  IOException if an I/O error occurs during serialization

      * @since 1.4

      */

     public void writeUnshared(Object obj) throws IOException {

         try {

             writeObject0(obj, true);

         } catch (IOException ex) {

             if (depth == 0) {

                 writeFatalException(ex);

             }

             throw ex;

         }

     }

     /**

      * Write the non-static and non-transient fields of the current class to

      * this stream.  This may only be called from the writeObject method of the

      * class being serialized. It will throw the NotActiveException if it is

      * called otherwise.

      *

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          <code>OutputStream</code>

      */

     public void defaultWriteObject() throws IOException {

         if ( curContext == null ) {

             throw new NotActiveException("not in call to writeObject");

         }

         Object curObj = curContext.getObj();

         ObjectStreamClass curDesc = curContext.getDesc();

         bout.setBlockDataMode(false);

         defaultWriteFields(curObj, curDesc);

         bout.setBlockDataMode(true);

     }

     /**

      * Retrieve the object used to buffer persistent fields to be written to

      * the stream.  The fields will be written to the stream when writeFields

      * method is called.

      *

      * @return  an instance of the class Putfield that holds the serializable

      *          fields

      * @throws  IOException if I/O errors occur

      * @since 1.2

      */

     public ObjectOutputStream.PutField putFields() throws IOException {

         if (curPut == null) {

             if (curContext == null) {

                 throw new NotActiveException("not in call to writeObject");

             }

             Object curObj = curContext.getObj();

             ObjectStreamClass curDesc = curContext.getDesc();

             curPut = new PutFieldImpl(curDesc);

         }

         return curPut;

     }

     /**

      * Write the buffered fields to the stream.

      *

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      * @throws  NotActiveException Called when a classes writeObject method was

      *          not called to write the state of the object.

      * @since 1.2

      */

     public void writeFields() throws IOException {

         if (curPut == null) {

             throw new NotActiveException("no current PutField object");

         }

         bout.setBlockDataMode(false);

         curPut.writeFields();

         bout.setBlockDataMode(true);

     }

     /**

      * Reset will disregard the state of any objects already written to the

      * stream.  The state is reset to be the same as a new ObjectOutputStream.

      * The current point in the stream is marked as reset so the corresponding

      * ObjectInputStream will be reset at the same point.  Objects previously

      * written to the stream will not be refered to as already being in the

      * stream.  They will be written to the stream again.

      *

      * @throws  IOException if reset() is invoked while serializing an object.

      */

     public void reset() throws IOException {

         if (depth != 0) {

             throw new IOException("stream active");

         }

         bout.setBlockDataMode(false);

         bout.writeByte(TC_RESET);

         clear();

         bout.setBlockDataMode(true);

     }

     /**

      * Subclasses may implement this method to allow class data to be stored in

      * the stream. By default this method does nothing.  The corresponding

      * method in ObjectInputStream is resolveClass.  This method is called

      * exactly once for each unique class in the stream.  The class name and

      * signature will have already been written to the stream.  This method may

      * make free use of the ObjectOutputStream to save any representation of

      * the class it deems suitable (for example, the bytes of the class file).

      * The resolveClass method in the corresponding subclass of

      * ObjectInputStream must read and use any data or objects written by

      * annotateClass.

      *

      * @param   cl the class to annotate custom data for

      * @throws  IOException Any exception thrown by the underlying

      *          OutputStream.

      */

     protected void annotateClass(Class<?> cl) throws IOException {

     }

     /**

      * Subclasses may implement this method to store custom data in the stream

      * along with descriptors for dynamic proxy classes.

      *

      * <p>This method is called exactly once for each unique proxy class

      * descriptor in the stream.  The default implementation of this method in

      * <code>ObjectOutputStream</code> does nothing.

      *

      * <p>The corresponding method in <code>ObjectInputStream</code> is

      * <code>resolveProxyClass</code>.  For a given subclass of

      * <code>ObjectOutputStream</code> that overrides this method, the

      * <code>resolveProxyClass</code> method in the corresponding subclass of

      * <code>ObjectInputStream</code> must read any data or objects written by

      * <code>annotateProxyClass</code>.

      *

      * @param   cl the proxy class to annotate custom data for

      * @throws  IOException any exception thrown by the underlying

      *          <code>OutputStream</code>

      * @see ObjectInputStream#resolveProxyClass(String[])

      * @since   1.3

      */

     protected void annotateProxyClass(Class<?> cl) throws IOException {

     }

     /**

      * This method will allow trusted subclasses of ObjectOutputStream to

      * substitute one object for another during serialization. Replacing

      * objects is disabled until enableReplaceObject is called. The

      * enableReplaceObject method checks that the stream requesting to do

      * replacement can be trusted.  The first occurrence of each object written

      * into the serialization stream is passed to replaceObject.  Subsequent

      * references to the object are replaced by the object returned by the

      * original call to replaceObject.  To ensure that the private state of

      * objects is not unintentionally exposed, only trusted streams may use

      * replaceObject.

      *

      * <p>The ObjectOutputStream.writeObject method takes a parameter of type

      * Object (as opposed to type Serializable) to allow for cases where

      * non-serializable objects are replaced by serializable ones.

      *

      * <p>When a subclass is replacing objects it must insure that either a

      * complementary substitution must be made during deserialization or that

      * the substituted object is compatible with every field where the

      * reference will be stored.  Objects whose type is not a subclass of the

      * type of the field or array element abort the serialization by raising an

      * exception and the object is not be stored.

      *

      * <p>This method is called only once when each object is first

      * encountered.  All subsequent references to the object will be redirected

      * to the new object. This method should return the object to be

      * substituted or the original object.

      *

      * <p>Null can be returned as the object to be substituted, but may cause

      * NullReferenceException in classes that contain references to the

      * original object since they may be expecting an object instead of

      * null.

      *

      * @param   obj the object to be replaced

      * @return  the alternate object that replaced the specified one

      * @throws  IOException Any exception thrown by the underlying

      *          OutputStream.

      */

     protected Object replaceObject(Object obj) throws IOException {

         return obj;

     }

     /**

      * Enable the stream to do replacement of objects in the stream.  When

      * enabled, the replaceObject method is called for every object being

      * serialized.

      *

      * <p>If <code>enable</code> is true, and there is a security manager

      * installed, this method first calls the security manager's

      * <code>checkPermission</code> method with a

      * <code>SerializablePermission("enableSubstitution")</code> permission to

      * ensure it's ok to enable the stream to do replacement of objects in the

      * stream.

      *

      * @param   enable boolean parameter to enable replacement of objects

      * @return  the previous setting before this method was invoked

      * @throws  SecurityException if a security manager exists and its

      *          <code>checkPermission</code> method denies enabling the stream

      *          to do replacement of objects in the stream.

      * @see SecurityManager#checkPermission

      * @see java.io.SerializablePermission

      */

     protected boolean enableReplaceObject(boolean enable)

         throws SecurityException

     {

         if (enable == enableReplace) {

             return enable;

         }

         if (enable) {

             SecurityManager sm = System.getSecurityManager();

             if (sm != null) {

                 sm.checkPermission(SUBSTITUTION_PERMISSION);

             }

         }

         enableReplace = enable;

         return !enableReplace;

     }

     /**

      * The writeStreamHeader method is provided so subclasses can append or

      * prepend their own header to the stream.  It writes the magic number and

      * version to the stream.

      *

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      */

     protected void writeStreamHeader() throws IOException {

         bout.writeShort(STREAM_MAGIC);

         bout.writeShort(STREAM_VERSION);

     }

     /**

      * Write the specified class descriptor to the ObjectOutputStream.  Class

      * descriptors are used to identify the classes of objects written to the

      * stream.  Subclasses of ObjectOutputStream may override this method to

      * customize the way in which class descriptors are written to the

      * serialization stream.  The corresponding method in ObjectInputStream,

      * <code>readClassDescriptor</code>, should then be overridden to

      * reconstitute the class descriptor from its custom stream representation.

      * By default, this method writes class descriptors according to the format

      * defined in the Object Serialization specification.

      *

      * <p>Note that this method will only be called if the ObjectOutputStream

      * is not using the old serialization stream format (set by calling

      * ObjectOutputStream's <code>useProtocolVersion</code> method).  If this

      * serialization stream is using the old format

      * (<code>PROTOCOL_VERSION_1</code>), the class descriptor will be written

      * internally in a manner that cannot be overridden or customized.

      *

      * @param   desc class descriptor to write to the stream

      * @throws  IOException If an I/O error has occurred.

      * @see java.io.ObjectInputStream#readClassDescriptor()

      * @see #useProtocolVersion(int)

      * @see java.io.ObjectStreamConstants#PROTOCOL_VERSION_1

      * @since 1.3

      */

     protected void writeClassDescriptor(ObjectStreamClass desc)

         throws IOException

     {

         desc.writeNonProxy(this);

     }

     /**

      * Writes a byte. This method will block until the byte is actually

      * written.

      *

      * @param   val the byte to be written to the stream

      * @throws  IOException If an I/O error has occurred.

      */

     public void write(int val) throws IOException {

         bout.write(val);

     }

     /**

      * Writes an array of bytes. This method will block until the bytes are

      * actually written.

      *

      * @param   buf the data to be written

      * @throws  IOException If an I/O error has occurred.

      */

     public void write(byte[] buf) throws IOException {

         bout.write(buf, 0, buf.length, false);

     }

     /**

      * Writes a sub array of bytes.

      *

      * @param   buf the data to be written

      * @param   off the start offset in the data

      * @param   len the number of bytes that are written

      * @throws  IOException If an I/O error has occurred.

      */

     public void write(byte[] buf, int off, int len) throws IOException {

         if (buf == null) {

             throw new NullPointerException();

         }

         int endoff = off + len;

         if (off < 0 || len < 0 || endoff > buf.length || endoff < 0) {

             throw new IndexOutOfBoundsException();

         }

         bout.write(buf, off, len, false);

     }

     /**

      * Flushes the stream. This will write any buffered output bytes and flush

      * through to the underlying stream.

      *

      * @throws  IOException If an I/O error has occurred.

      */

     public void flush() throws IOException {

         bout.flush();

     }

     /**

      * Drain any buffered data in ObjectOutputStream.  Similar to flush but

      * does not propagate the flush to the underlying stream.

      *

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      */

     protected void drain() throws IOException {

         bout.drain();

     }

     /**

      * Closes the stream. This method must be called to release any resources

      * associated with the stream.

      *

      * @throws  IOException If an I/O error has occurred.

      */

     public void close() throws IOException {

         flush();

         clear();

         bout.close();

     }

     /**

      * Writes a boolean.

      *

      * @param   val the boolean to be written

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      */

     public void writeBoolean(boolean val) throws IOException {

         bout.writeBoolean(val);

     }

     /**

      * Writes an 8 bit byte.

      *

      * @param   val the byte value to be written

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      */

     public void writeByte(int val) throws IOException  {

         bout.writeByte(val);

     }

     /**

      * Writes a 16 bit short.

      *

      * @param   val the short value to be written

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      */

     public void writeShort(int val)  throws IOException {

         bout.writeShort(val);

     }

     /**

      * Writes a 16 bit char.

      *

      * @param   val the char value to be written

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      */

     public void writeChar(int val)  throws IOException {

         bout.writeChar(val);

     }

     /**

      * Writes a 32 bit int.

      *

      * @param   val the integer value to be written

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      */

     public void writeInt(int val)  throws IOException {

         bout.writeInt(val);

     }

     /**

      * Writes a 64 bit long.

      *

      * @param   val the long value to be written

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      */

     public void writeLong(long val)  throws IOException {

         bout.writeLong(val);

     }

     /**

      * Writes a 32 bit float.

      *

      * @param   val the float value to be written

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      */

     public void writeFloat(float val) throws IOException {

         bout.writeFloat(val);

     }

     /**

      * Writes a 64 bit double.

      *

      * @param   val the double value to be written

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      */

     public void writeDouble(double val) throws IOException {

         bout.writeDouble(val);

     }

     /**

      * Writes a String as a sequence of bytes.

      *

      * @param   str the String of bytes to be written

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      */

     public void writeBytes(String str) throws IOException {

         bout.writeBytes(str);

     }

     /**

      * Writes a String as a sequence of chars.

      *

      * @param   str the String of chars to be written

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      */

     public void writeChars(String str) throws IOException {

         bout.writeChars(str);

     }

     /**

      * Primitive data write of this String in

      * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>

      * format.  Note that there is a

      * significant difference between writing a String into the stream as

      * primitive data or as an Object. A String instance written by writeObject

      * is written into the stream as a String initially. Future writeObject()

      * calls write references to the string into the stream.

      *

      * @param   str the String to be written

      * @throws  IOException if I/O errors occur while writing to the underlying

      *          stream

      */

     public void writeUTF(String str) throws IOException {

         bout.writeUTF(str);

     }

     /**

      * Provide programmatic access to the persistent fields to be written

      * to ObjectOutput.

      *

      * @since 1.2

      */

     public static abstract class PutField {

         /**

          * Put the value of the named boolean field into the persistent field.

          *

          * @param  name the name of the serializable field

          * @param  val the value to assign to the field

          * @throws IllegalArgumentException if <code>name</code> does not

          * match the name of a serializable field for the class whose fields

          * are being written, or if the type of the named field is not

          * <code>boolean</code>

          */

         public abstract void put(String name, boolean val);

         /**

          * Put the value of the named byte field into the persistent field.

          *

          * @param  name the name of the serializable field

          * @param  val the value to assign to the field

          * @throws IllegalArgumentException if <code>name</code> does not

          * match the name of a serializable field for the class whose fields

          * are being written, or if the type of the named field is not

          * <code>byte</code>

          */

         public abstract void put(String name, byte val);

         /**

          * Put the value of the named char field into the persistent field.

          *

          * @param  name the name of the serializable field

          * @param  val the value to assign to the field

          * @throws IllegalArgumentException if <code>name</code> does not

          * match the name of a serializable field for the class whose fields

          * are being written, or if the type of the named field is not

          * <code>char</code>

          */

         public abstract void put(String name, char val);

         /**

          * Put the value of the named short field into the persistent field.

          *

          * @param  name the name of the serializable field

          * @param  val the value to assign to the field

          * @throws IllegalArgumentException if <code>name</code> does not

          * match the name of a serializable field for the class whose fields

          * are being written, or if the type of the named field is not

          * <code>short</code>

          */

         public abstract void put(String name, short val);

         /**

          * Put the value of the named int field into the persistent field.

          *

          * @param  name the name of the serializable field

          * @param  val the value to assign to the field

          * @throws IllegalArgumentException if <code>name</code> does not

          * match the name of a serializable field for the class whose fields

          * are being written, or if the type of the named field is not

          * <code>int</code>

          */

         public abstract void put(String name, int val);

         /**

          * Put the value of the named long field into the persistent field.

          *

          * @param  name the name of the serializable field

          * @param  val the value to assign to the field

          * @throws IllegalArgumentException if <code>name</code> does not

          * match the name of a serializable field for the class whose fields

          * are being written, or if the type of the named field is not

          * <code>long</code>

          */

         public abstract void put(String name, long val);

         /**

          * Put the value of the named float field into the persistent field.

          *

          * @param  name the name of the serializable field

          * @param  val the value to assign to the field

          * @throws IllegalArgumentException if <code>name</code> does not

          * match the name of a serializable field for the class whose fields

          * are being written, or if the type of the named field is not

          * <code>float</code>

          */

         public abstract void put(String name, float val);

         /**

          * Put the value of the named double field into the persistent field.

          *

          * @param  name the name of the serializable field

          * @param  val the value to assign to the field

          * @throws IllegalArgumentException if <code>name</code> does not

          * match the name of a serializable field for the class whose fields

          * are being written, or if the type of the named field is not

          * <code>double</code>

          */

         public abstract void put(String name, double val);

         /**

          * Put the value of the named Object field into the persistent field.

          *

          * @param  name the name of the serializable field

          * @param  val the value to assign to the field

          *         (which may be <code>null</code>)

          * @throws IllegalArgumentException if <code>name</code> does not

          * match the name of a serializable field for the class whose fields

          * are being written, or if the type of the named field is not a

          * reference type

          */

         public abstract void put(String name, Object val);

         /**

          * Write the data and fields to the specified ObjectOutput stream,

          * which must be the same stream that produced this

          * <code>PutField</code> object.

          *

          * @param  out the stream to write the data and fields to

          * @throws IOException if I/O errors occur while writing to the

          *         underlying stream

          * @throws IllegalArgumentException if the specified stream is not

          *         the same stream that produced this <code>PutField</code>

          *         object

          * @deprecated This method does not write the values contained by this

          *         <code>PutField</code> object in a proper format, and may

          *         result in corruption of the serialization stream.  The

          *         correct way to write <code>PutField</code> data is by

          *         calling the {@link java.io.ObjectOutputStream#writeFields()}

          *         method.

          */

         @Deprecated

         public abstract void write(ObjectOutput out) throws IOException;

     }

     /**

      * Returns protocol version in use.

      */

     int getProtocolVersion() {

         return protocol;

     }

     /**

      * Writes string without allowing it to be replaced in stream.  Used by

      * ObjectStreamClass to write class descriptor type strings.

      */

     void writeTypeString(String str) throws IOException {

         int handle;

         if (str == null) {

             writeNull();

         } else if ((handle = handles.lookup(str)) != -1) {

             writeHandle(handle);

         } else {

             writeString(str, false);

         }

     }

     /**

      * Verifies that this (possibly subclass) instance can be constructed

      * without violating security constraints: the subclass must not override

      * security-sensitive non-final methods, or else the

      * "enableSubclassImplementation" SerializablePermission is checked.

      */

     private void verifySubclass() {

         Class cl = getClass();

         if (cl == ObjectOutputStream.class) {

             return;

         }

         SecurityManager sm = System.getSecurityManager();

         if (sm == null) {

             return;

         }

         processQueue(Caches.subclassAuditsQueue, Caches.subclassAudits);

         WeakClassKey key = new WeakClassKey(cl, Caches.subclassAuditsQueue);

         Boolean result = Caches.subclassAudits.get(key);

         if (result == null) {

             result = Boolean.valueOf(auditSubclass(cl));

             Caches.subclassAudits.putIfAbsent(key, result);

         }

         if (result.booleanValue()) {

             return;

         }

         sm.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);

     }

     /**

      * Performs reflective checks on given subclass to verify that it doesn't

      * override security-sensitive non-final methods.  Returns true if subclass

      * is "safe", false otherwise.

      */

     private static boolean auditSubclass(final Class subcl) {

         Boolean result = AccessController.doPrivileged(

             new PrivilegedAction<Boolean>() {

                 public Boolean run() {

                     for (Class cl = subcl;

                          cl != ObjectOutputStream.class;

                          cl = cl.getSuperclass())

                     {

                         try {

                             cl.getDeclaredMethod(

                                 "writeUnshared", new Class[] { Object.class });

                             return Boolean.FALSE;

                         } catch (NoSuchMethodException ex) {

                         }

                         try {

                             cl.getDeclaredMethod("putFields", (Class[]) null);

                             return Boolean.FALSE;

                         } catch (NoSuchMethodException ex) {

                         }

                     }

                     return Boolean.TRUE;

                 }

             }

         );

         return result.booleanValue();

     }

     /**

      * Clears internal data structures.

      */

     private void clear() {

         subs.clear();

         handles.clear();

     }

     /**

      * Underlying writeObject/writeUnshared implementation.

      */

     private void writeObject0(Object obj, boolean unshared)

         throws IOException

     {

         boolean oldMode = bout.setBlockDataMode(false);

         depth++;

         try {

             // handle previously written and non-replaceable objects

             int h;

             if ((obj = subs.lookup(obj)) == null) {

                 writeNull();

                 return;

             } else if (!unshared && (h = handles.lookup(obj)) != -1) {

                 writeHandle(h);

                 return;

             } else if (obj instanceof Class) {

                 writeClass((Class) obj, unshared);

                 return;

             } else if (obj instanceof ObjectStreamClass) {

                 writeClassDesc((ObjectStreamClass) obj, unshared);

                 return;

             }

             // check for replacement object

             Object orig = obj;

             Class cl = obj.getClass();

             ObjectStreamClass desc;

             for (;;) {

                 // REMIND: skip this check for strings/arrays?

                 Class repCl;

                 desc = ObjectStreamClass.lookup(cl, true);

                 if (!desc.hasWriteReplaceMethod() ||

                     (obj = desc.invokeWriteReplace(obj)) == null ||

                     (repCl = obj.getClass()) == cl)

                 {

                     break;

                 }

                 cl = repCl;

             }

             if (enableReplace) {

                 Object rep = replaceObject(obj);

                 if (rep != obj && rep != null) {

                     cl = rep.getClass();

                     desc = ObjectStreamClass.lookup(cl, true);

                 }

                 obj = rep;

             }

             // if object replaced, run through original checks a second time

             if (obj != orig) {

                 subs.assign(orig, obj);

                 if (obj == null) {

                     writeNull();

                     return;

                 } else if (!unshared && (h = handles.lookup(obj)) != -1) {

                     writeHandle(h);

                     return;

                 } else if (obj instanceof Class) {

                     writeClass((Class) obj, unshared);

                     return;

                 } else if (obj instanceof ObjectStreamClass) {

                     writeClassDesc((ObjectStreamClass) obj, unshared);

                     return;

                 }

             }

             // remaining cases

             if (obj instanceof String) {

                 writeString((String) obj, unshared);

             } else if (cl.isArray()) {

                 writeArray(obj, desc, unshared);

             } else if (obj instanceof Enum) {

                 writeEnum((Enum) obj, desc, unshared);

             } else if (obj instanceof Serializable) {

                 writeOrdinaryObject(obj, desc, unshared);

             } else {

                 if (extendedDebugInfo) {

                     throw new NotSerializableException(

                         cl.getName() + "\n" + debugInfoStack.toString());

                 } else {

                     throw new NotSerializableException(cl.getName());

                 }

             }

         } finally {

             depth--;

             bout.setBlockDataMode(oldMode);

         }

     }

     /**

      * Writes null code to stream.

      */

     private void writeNull() throws IOException {

         bout.writeByte(TC_NULL);

     }

     /**

      * Writes given object handle to stream.

      */

     private void writeHandle(int handle) throws IOException {

         bout.writeByte(TC_REFERENCE);

         bout.writeInt(baseWireHandle + handle);

     }

     /**

      * Writes representation of given class to stream.

      */

     private void writeClass(Class cl, boolean unshared) throws IOException {

         bout.writeByte(TC_CLASS);

         writeClassDesc(ObjectStreamClass.lookup(cl, true), false);

         handles.assign(unshared ? null : cl);

     }

     /**

      * Writes representation of given class descriptor to stream.

      */

     private void writeClassDesc(ObjectStreamClass desc, boolean unshared)

         throws IOException

     {

         int handle;

         if (desc == null) {

             writeNull();

         } else if (!unshared && (handle = handles.lookup(desc)) != -1) {

             writeHandle(handle);

         } else if (desc.isProxy()) {

             writeProxyDesc(desc, unshared);

         } else {

             writeNonProxyDesc(desc, unshared);

         }

     }

     /**

      * Writes class descriptor representing a dynamic proxy class to stream.

      */

     private void writeProxyDesc(ObjectStreamClass desc, boolean unshared)

         throws IOException

     {

         bout.writeByte(TC_PROXYCLASSDESC);

         handles.assign(unshared ? null : desc);

         Class cl = desc.forClass();

         Class[] ifaces = cl.getInterfaces();

         bout.writeInt(ifaces.length);

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

             bout.writeUTF(ifaces[i].getName());

         }

         bout.setBlockDataMode(true);

         annotateProxyClass(cl);

         bout.setBlockDataMode(false);

         bout.writeByte(TC_ENDBLOCKDATA);

         writeClassDesc(desc.getSuperDesc(), false);

     }

     /**

      * Writes class descriptor representing a standard (i.e., not a dynamic

      * proxy) class to stream.

      */

     private void writeNonProxyDesc(ObjectStreamClass desc, boolean unshared)

         throws IOException

     {

         bout.writeByte(TC_CLASSDESC);

         handles.assign(unshared ? null : desc);

         if (protocol == PROTOCOL_VERSION_1) {

             // do not invoke class descriptor write hook with old protocol

             desc.writeNonProxy(this);

         } else {

             writeClassDescriptor(desc);

         }

         Class cl = desc.forClass();

         bout.setBlockDataMode(true);

         annotateClass(cl);

         bout.setBlockDataMode(false);

         bout.writeByte(TC_ENDBLOCKDATA);

         writeClassDesc(desc.getSuperDesc(), false);

     }

     /**

      * Writes given string to stream, using standard or long UTF format

      * depending on string length.

      */

     private void writeString(String str, boolean unshared) throws IOException {

         handles.assign(unshared ? null : str);

         long utflen = bout.getUTFLength(str);

         if (utflen <= 0xFFFF) {

             bout.writeByte(TC_STRING);

             bout.writeUTF(str, utflen);

         } else {

             bout.writeByte(TC_LONGSTRING);

             bout.writeLongUTF(str, utflen);

         }

     }

     /**

      * Writes given array object to stream.

      */

     private void writeArray(Object array,

                             ObjectStreamClass desc,

                             boolean unshared)

         throws IOException

     {

         bout.writeByte(TC_ARRAY);

         writeClassDesc(desc, false);

         handles.assign(unshared ? null : array);

         Class ccl = desc.forClass().getComponentType();

         if (ccl.isPrimitive()) {

             if (ccl == Integer.TYPE) {

                 int[] ia = (int[]) array;

                 bout.writeInt(ia.length);

                 bout.writeInts(ia, 0, ia.length);

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

                 byte[] ba = (byte[]) array;

                 bout.writeInt(ba.length);

                 bout.write(ba, 0, ba.length, true);

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

                 long[] ja = (long[]) array;

                 bout.writeInt(ja.length);

                 bout.writeLongs(ja, 0, ja.length);

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

                 float[] fa = (float[]) array;

                 bout.writeInt(fa.length);

                 bout.writeFloats(fa, 0, fa.length);

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

                 double[] da = (double[]) array;

                 bout.writeInt(da.length);

                 bout.writeDoubles(da, 0, da.length);

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

                 short[] sa = (short[]) array;

                 bout.writeInt(sa.length);

                 bout.writeShorts(sa, 0, sa.length);

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

                 char[] ca = (char[]) array;

                 bout.writeInt(ca.length);

                 bout.writeChars(ca, 0, ca.length);

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

                 boolean[] za = (boolean[]) array;

                 bout.writeInt(za.length);

                 bout.writeBooleans(za, 0, za.length);

             } else {

                 throw new InternalError();

             }

         } else {

             Object[] objs = (Object[]) array;

             int len = objs.length;

             bout.writeInt(len);

             if (extendedDebugInfo) {

                 debugInfoStack.push(

                     "array (class \"" + array.getClass().getName() +

                     "\", size: " + len  + ")");

             }

             try {

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

                     if (extendedDebugInfo) {

                         debugInfoStack.push(

                             "element of array (index: " + i + ")");

                     }

                     try {

                         writeObject0(objs[i], false);

                     } finally {

                         if (extendedDebugInfo) {

                             debugInfoStack.pop();

                         }

                     }

                 }

             } finally {

                 if (extendedDebugInfo) {

                     debugInfoStack.pop();

                 }

             }

         }

     }

     /**

      * Writes given enum constant to stream.

      */

     private void writeEnum(Enum en,

                            ObjectStreamClass desc,

                            boolean unshared)

         throws IOException

     {

         bout.writeByte(TC_ENUM);

         ObjectStreamClass sdesc = desc.getSuperDesc();

         writeClassDesc((sdesc.forClass() == Enum.class) ? desc : sdesc, false);

         handles.assign(unshared ? null : en);

         writeString(en.name(), false);

     }

     /**

      * Writes representation of a "ordinary" (i.e., not a String, Class,

      * ObjectStreamClass, array, or enum constant) serializable object to the

      * stream.

      */

     private void writeOrdinaryObject(Object obj,

                                      ObjectStreamClass desc,

                                      boolean unshared)

         throws IOException

     {

         if (extendedDebugInfo) {

             debugInfoStack.push(

                 (depth == 1 ? "root " : "") + "object (class \"" +

                 obj.getClass().getName() + "\", " + obj.toString() + ")");

         }

         try {

             desc.checkSerialize();

             bout.writeByte(TC_OBJECT);

             writeClassDesc(desc, false);

             handles.assign(unshared ? null : obj);

             if (desc.isExternalizable() && !desc.isProxy()) {

                 writeExternalData((Externalizable) obj);

             } else {

                 writeSerialData(obj, desc);

             }

         } finally {

             if (extendedDebugInfo) {

                 debugInfoStack.pop();

             }

         }

     }

     /**

      * Writes externalizable data of given object by invoking its

      * writeExternal() method.

      */

     private void writeExternalData(Externalizable obj) throws IOException {

         PutFieldImpl oldPut = curPut;

         curPut = null;

         if (extendedDebugInfo) {

             debugInfoStack.push("writeExternal data");

         }

         SerialCallbackContext oldContext = curContext;

         try {

             curContext = null;

             if (protocol == PROTOCOL_VERSION_1) {

                 obj.writeExternal(this);

             } else {

                 bout.setBlockDataMode(true);

                 obj.writeExternal(this);

                 bout.setBlockDataMode(false);

                 bout.writeByte(TC_ENDBLOCKDATA);

             }

         } finally {

             curContext = oldContext;

             if (extendedDebugInfo) {

                 debugInfoStack.pop();

             }

         }

         curPut = oldPut;

     }

     /**

      * Writes instance data for each serializable class of given object, from

      * superclass to subclass.

      */

     private void writeSerialData(Object obj, ObjectStreamClass desc)

         throws IOException

     {

         ObjectStreamClass.ClassDataSlot[] slots = desc.getClassDataLayout();

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

             ObjectStreamClass slotDesc = slots[i].desc;

             if (slotDesc.hasWriteObjectMethod()) {

                 PutFieldImpl oldPut = curPut;

                 curPut = null;

                 SerialCallbackContext oldContext = curContext;

                 if (extendedDebugInfo) {

                     debugInfoStack.push(

                         "custom writeObject data (class \"" +

                         slotDesc.getName() + "\")");

                 }

                 try {

                     curContext = new SerialCallbackContext(obj, slotDesc);

                     bout.setBlockDataMode(true);

                     slotDesc.invokeWriteObject(obj, this);

                     bout.setBlockDataMode(false);

                     bout.writeByte(TC_ENDBLOCKDATA);

                 } finally {

                     curContext.setUsed();

                     curContext = oldContext;

                     if (extendedDebugInfo) {

                         debugInfoStack.pop();

                     }

                 }

                 curPut = oldPut;

             } else {

                 defaultWriteFields(obj, slotDesc);

             }

         }

     }

     /**

      * Fetches and writes values of serializable fields of given object to

      * stream.  The given class descriptor specifies which field values to

      * write, and in which order they should be written.

      */

     private void defaultWriteFields(Object obj, ObjectStreamClass desc)

         throws IOException

     {

         // REMIND: perform conservative isInstance check here?

         desc.checkDefaultSerialize();

         int primDataSize = desc.getPrimDataSize();

         if (primVals == null || primVals.length < primDataSize) {

             primVals = new byte[primDataSize];

         }

         desc.getPrimFieldValues(obj, primVals);

         bout.write(primVals, 0, primDataSize, false);

         ObjectStreamField[] fields = desc.getFields(false);

         Object[] objVals = new Object[desc.getNumObjFields()];

         int numPrimFields = fields.length - objVals.length;

         desc.getObjFieldValues(obj, objVals);

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

             if (extendedDebugInfo) {

                 debugInfoStack.push(

                     "field (class \"" + desc.getName() + "\", name: \"" +

                     fields[numPrimFields + i].getName() + "\", type: \"" +

                     fields[numPrimFields + i].getType() + "\")");

             }

             try {

                 writeObject0(objVals[i],

                              fields[numPrimFields + i].isUnshared());

             } finally {

                 if (extendedDebugInfo) {

                     debugInfoStack.pop();

                 }

             }

         }

     }

     /**

      * Attempts to write to stream fatal IOException that has caused

      * serialization to abort.

      */

     private void writeFatalException(IOException ex) throws IOException {

         /*

          * Note: the serialization specification states that if a second

          * IOException occurs while attempting to serialize the original fatal

          * exception to the stream, then a StreamCorruptedException should be

          * thrown (section 2.1).  However, due to a bug in previous

          * implementations of serialization, StreamCorruptedExceptions were

          * rarely (if ever) actually thrown--the "root" exceptions from

          * underlying streams were thrown instead.  This historical behavior is

          * followed here for consistency.

          */

         clear();

         boolean oldMode = bout.setBlockDataMode(false);

         try {

             bout.writeByte(TC_EXCEPTION);

             writeObject0(ex, false);

             clear();

         } finally {

             bout.setBlockDataMode(oldMode);

         }

     }

     /**

      * Converts specified span of float values into byte values.

      */

     // REMIND: remove once hotspot inlines Float.floatToIntBits

     private static native void floatsToBytes(float[] src, int srcpos,

                                              byte[] dst, int dstpos,

                                              int nfloats);

     /**

      * Converts specified span of double values into byte values.

      */

     // REMIND: remove once hotspot inlines Double.doubleToLongBits

     private static native void doublesToBytes(double[] src, int srcpos,

                                               byte[] dst, int dstpos,

                                               int ndoubles);

     /**

      * Default PutField implementation.

      */

     private class PutFieldImpl extends PutField {

         /** class descriptor describing serializable fields */

         private final ObjectStreamClass desc;

         /** primitive field values */

         private final byte[] primVals;

         /** object field values */

         private final Object[] objVals;

         /**

          * Creates PutFieldImpl object for writing fields defined in given

          * class descriptor.

          */

         PutFieldImpl(ObjectStreamClass desc) {

             this.desc = desc;

             primVals = new byte[desc.getPrimDataSize()];

             objVals = new Object[desc.getNumObjFields()];

         }

         public void put(String name, boolean val) {

             Bits.putBoolean(primVals, getFieldOffset(name, Boolean.TYPE), val);

         }

         public void put(String name, byte val) {

             primVals[getFieldOffset(name, Byte.TYPE)] = val;

         }

         public void put(String name, char val) {

             Bits.putChar(primVals, getFieldOffset(name, Character.TYPE), val);

         }

         public void put(String name, short val) {

             Bits.putShort(primVals, getFieldOffset(name, Short.TYPE), val);

         }

         public void put(String name, int val) {

             Bits.putInt(primVals, getFieldOffset(name, Integer.TYPE), val);

         }

         public void put(String name, float val) {

             Bits.putFloat(primVals, getFieldOffset(name, Float.TYPE), val);

         }

         public void put(String name, long val) {

             Bits.putLong(primVals, getFieldOffset(name, Long.TYPE), val);

         }

         public void put(String name, double val) {

             Bits.putDouble(primVals, getFieldOffset(name, Double.TYPE), val);

         }

         public void put(String name, Object val) {

             objVals[getFieldOffset(name, Object.class)] = val;

         }

         // deprecated in ObjectOutputStream.PutField

         public void write(ObjectOutput out) throws IOException {

             /*

              * Applications should *not* use this method to write PutField

              * data, as it will lead to stream corruption if the PutField

              * object writes any primitive data (since block data mode is not

              * unset/set properly, as is done in OOS.writeFields()).  This

              * broken implementation is being retained solely for behavioral

              * compatibility, in order to support applications which use

              * OOS.PutField.write() for writing only non-primitive data.

              *

              * Serialization of unshared objects is not implemented here since

              * it is not necessary for backwards compatibility; also, unshared

              * semantics may not be supported by the given ObjectOutput

              * instance.  Applications which write unshared objects using the

              * PutField API must use OOS.writeFields().

              */

             if (ObjectOutputStream.this != out) {

                 throw new IllegalArgumentException("wrong stream");

             }

             out.write(primVals, 0, primVals.length);

             ObjectStreamField[] fields = desc.getFields(false);

             int numPrimFields = fields.length - objVals.length;

             // REMIND: warn if numPrimFields > 0?

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

                 if (fields[numPrimFields + i].isUnshared()) {

                     throw new IOException("cannot write unshared object");

                 }

                 out.writeObject(objVals[i]);

             }

         }

         /**

          * Writes buffered primitive data and object fields to stream.

          */

         void writeFields() throws IOException {

             bout.write(primVals, 0, primVals.length, false);

             ObjectStreamField[] fields = desc.getFields(false);

             int numPrimFields = fields.length - objVals.length;

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

                 if (extendedDebugInfo) {

                     debugInfoStack.push(

                         "field (class \"" + desc.getName() + "\", name: \"" +

                         fields[numPrimFields + i].getName() + "\", type: \"" +

                         fields[numPrimFields + i].getType() + "\")");

                 }

                 try {

                     writeObject0(objVals[i],

                                  fields[numPrimFields + i].isUnshared());

                 } finally {

                     if (extendedDebugInfo) {

                         debugInfoStack.pop();

                     }

                 }

             }

         }

         /**

          * Returns offset of field with given 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.

          * Throws IllegalArgumentException if no matching field found.

          */

         private int getFieldOffset(String name, Class type) {

             ObjectStreamField field = desc.getField(name, type);

             if (field == null) {

                 throw new IllegalArgumentException("no such field " + name +

                                                    " with type " + type);

             }

             return field.getOffset();

         }

     }

     /**

      * Buffered output stream with two modes: in default mode, outputs data in

      * same format as DataOutputStream; in "block data" mode, outputs data

      * bracketed by block data markers (see object serialization specification

      * for details).

      */

     private static class BlockDataOutputStream

         extends OutputStream implements DataOutput

     {

         /** maximum data block length */

         private static final int MAX_BLOCK_SIZE = 1024;

         /** maximum data block header length */

         private static final int MAX_HEADER_SIZE = 5;

         /** (tunable) length of char buffer (for writing strings) */

         private static final int CHAR_BUF_SIZE = 256;

         /** buffer for writing general/block data */

         private final byte[] buf = new byte[MAX_BLOCK_SIZE];

         /** buffer for writing block data headers */

         private final byte[] hbuf = new byte[MAX_HEADER_SIZE];

         /** char buffer for fast string writes */

         private final char[] cbuf = new char[CHAR_BUF_SIZE];

         /** block data mode */

         private boolean blkmode = false;

         /** current offset into buf */

         private int pos = 0;

         /** underlying output stream */

         private final OutputStream out;

         /** loopback stream (for data writes that span data blocks) */

         private final DataOutputStream dout;

         /**

          * Creates new BlockDataOutputStream on top of given underlying stream.

          * Block data mode is turned off by default.

          */

         BlockDataOutputStream(OutputStream out) {

             this.out = out;

             dout = new DataOutputStream(this);

         }

         /**

          * Sets block data mode to the given mode (true == on, false == off)

          * and returns the previous mode value.  If the new mode is the same as

          * the old mode, no action is taken.  If the new mode differs from the

          * old mode, any buffered data is flushed before switching to the new

          * mode.

          */

         boolean setBlockDataMode(boolean mode) throws IOException {

             if (blkmode == mode) {

                 return blkmode;

             }

             drain();

             blkmode = mode;

             return !blkmode;

         }

         /**

          * Returns true if the stream is currently in block data mode, false

          * otherwise.

          */

         boolean getBlockDataMode() {

             return blkmode;

         }

         /* ----------------- generic output stream methods ----------------- */

         /*

          * The following methods are equivalent to their counterparts in

          * OutputStream, except that they partition written data into data

          * blocks when in block data mode.

          */

         public void write(int b) throws IOException {

             if (pos >= MAX_BLOCK_SIZE) {

                 drain();

             }

             buf[pos++] = (byte) b;

         }

         public void write(byte[] b) throws IOException {

             write(b, 0, b.length, false);

         }

         public void write(byte[] b, int off, int len) throws IOException {

             write(b, off, len, false);

         }

         public void flush() throws IOException {

             drain();

             out.flush();

         }

         public void close() throws IOException {

             flush();

             out.close();

         }

         /**

          * Writes specified span of byte values from given array.  If copy is

          * true, copies the values to an intermediate buffer before writing

          * them to underlying stream (to avoid exposing a reference to the

          * original byte array).

          */

         void write(byte[] b, int off, int len, boolean copy)

             throws IOException

         {

             if (!(copy || blkmode)) {           // write directly

                 drain();

                 out.write(b, off, len);

                 return;

             }

             while (len > 0) {

                 if (pos >= MAX_BLOCK_SIZE) {

                     drain();

                 }

                 if (len >= MAX_BLOCK_SIZE && !copy && pos == 0) {

                     // avoid unnecessary copy

                     writeBlockHeader(MAX_BLOCK_SIZE);

                     out.write(b, off, MAX_BLOCK_SIZE);

                     off += MAX_BLOCK_SIZE;

                     len -= MAX_BLOCK_SIZE;

                 } else {

                     int wlen = Math.min(len, MAX_BLOCK_SIZE - pos);

                     System.arraycopy(b, off, buf, pos, wlen);

                     pos += wlen;

                     off += wlen;

                     len -= wlen;

                 }

             }

         }

         /**

          * Writes all buffered data from this stream to the underlying stream,

          * but does not flush underlying stream.

          */

         void drain() throws IOException {

             if (pos == 0) {

                 return;

             }

             if (blkmode) {

                 writeBlockHeader(pos);

             }

             out.write(buf, 0, pos);

             pos = 0;

         }

         /**

          * Writes block data header.  Data blocks shorter than 256 bytes are

          * prefixed with a 2-byte header; all others start with a 5-byte

          * header.

          */

         private void writeBlockHeader(int len) throws IOException {

             if (len <= 0xFF) {

                 hbuf[0] = TC_BLOCKDATA;

                 hbuf[1] = (byte) len;

                 out.write(hbuf, 0, 2);

             } else {

                 hbuf[0] = TC_BLOCKDATALONG;

                 Bits.putInt(hbuf, 1, len);

                 out.write(hbuf, 0, 5);

             }

         }

         /* ----------------- primitive data output methods ----------------- */

         /*

          * The following methods are equivalent to their counterparts in

          * DataOutputStream, except that they partition written data into data

          * blocks when in block data mode.

          */

         public void writeBoolean(boolean v) throws IOException {

             if (pos >= MAX_BLOCK_SIZE) {

                 drain();

             }

             Bits.putBoolean(buf, pos++, v);

         }

         public void writeByte(int v) throws IOException {

             if (pos >= MAX_BLOCK_SIZE) {

                 drain();

             }

             buf[pos++] = (byte) v;

         }

         public void writeChar(int v) throws IOException {

             if (pos + 2 <= MAX_BLOCK_SIZE) {

                 Bits.putChar(buf, pos, (char) v);

                 pos += 2;

             } else {

                 dout.writeChar(v);

             }

         }

         public void writeShort(int v) throws IOException {

             if (pos + 2 <= MAX_BLOCK_SIZE) {

                 Bits.putShort(buf, pos, (short) v);

                 pos += 2;

             } else {

                 dout.writeShort(v);

             }

         }

         public void writeInt(int v) throws IOException {

             if (pos + 4 <= MAX_BLOCK_SIZE) {

                 Bits.putInt(buf, pos, v);

                 pos += 4;

             } else {

                 dout.writeInt(v);

             }

         }

         public void writeFloat(float v) throws IOException {

             if (pos + 4 <= MAX_BLOCK_SIZE) {

                 Bits.putFloat(buf, pos, v);

                 pos += 4;

             } else {

                 dout.writeFloat(v);

             }

         }

         public void writeLong(long v) throws IOException {

             if (pos + 8 <= MAX_BLOCK_SIZE) {

                 Bits.putLong(buf, pos, v);

                 pos += 8;

             } else {

                 dout.writeLong(v);

             }

         }

         public void writeDouble(double v) throws IOException {

             if (pos + 8 <= MAX_BLOCK_SIZE) {

                 Bits.putDouble(buf, pos, v);

                 pos += 8;

             } else {

                 dout.writeDouble(v);

             }

         }

         public void writeBytes(String s) throws IOException {

             int endoff = s.length();

             int cpos = 0;

             int csize = 0;

             for (int off = 0; off < endoff; ) {

                 if (cpos >= csize) {

                     cpos = 0;

                     csize = Math.min(endoff - off, CHAR_BUF_SIZE);

                     s.getChars(off, off + csize, cbuf, 0);

                 }

                 if (pos >= MAX_BLOCK_SIZE) {

                     drain();

                 }

                 int n = Math.min(csize - cpos, MAX_BLOCK_SIZE - pos);

                 int stop = pos + n;

                 while (pos < stop) {

                     buf[pos++] = (byte) cbuf[cpos++];

                 }

                 off += n;

             }

         }

         public void writeChars(String s) throws IOException {

             int endoff = s.length();

             for (int off = 0; off < endoff; ) {

                 int csize = Math.min(endoff - off, CHAR_BUF_SIZE);

                 s.getChars(off, off + csize, cbuf, 0);

                 writeChars(cbuf, 0, csize);

                 off += csize;

             }

         }

         public void writeUTF(String s) throws IOException {

             writeUTF(s, getUTFLength(s));

         }

         /* -------------- primitive data array output methods -------------- */

         /*

          * The following methods write out spans of primitive data values.

          * Though equivalent to calling the corresponding primitive write

          * methods repeatedly, these methods are optimized for writing groups

          * of primitive data values more efficiently.

          */

         void writeBooleans(boolean[] v, int off, int len) throws IOException {

             int endoff = off + len;

             while (off < endoff) {

                 if (pos >= MAX_BLOCK_SIZE) {

                     drain();

                 }

                 int stop = Math.min(endoff, off + (MAX_BLOCK_SIZE - pos));

                 while (off < stop) {

                     Bits.putBoolean(buf, pos++, v[off++]);

                 }

             }

         }

         void writeChars(char[] v, int off, int len) throws IOException {

             int limit = MAX_BLOCK_SIZE - 2;

             int endoff = off + len;

             while (off < endoff) {

                 if (pos <= limit) {

                     int avail = (MAX_BLOCK_SIZE - pos) >> 1;

                     int stop = Math.min(endoff, off + avail);

                     while (off < stop) {

                         Bits.putChar(buf, pos, v[off++]);

                         pos += 2;

                     }

                 } else {

                     dout.writeChar(v[off++]);

                 }

             }

         }

         void writeShorts(short[] v, int off, int len) throws IOException {

             int limit = MAX_BLOCK_SIZE - 2;

             int endoff = off + len;

             while (off < endoff) {

                 if (pos <= limit) {

                     int avail = (MAX_BLOCK_SIZE - pos) >> 1;

                     int stop = Math.min(endoff, off + avail);

                     while (off < stop) {

                         Bits.putShort(buf, pos, v[off++]);

                         pos += 2;

                     }

                 } else {

                     dout.writeShort(v[off++]);

                 }

             }

         }

         void writeInts(int[] v, int off, int len) throws IOException {

             int limit = MAX_BLOCK_SIZE - 4;

             int endoff = off + len;

             while (off < endoff) {

                 if (pos <= limit) {

                     int avail = (MAX_BLOCK_SIZE - pos) >> 2;

                     int stop = Math.min(endoff, off + avail);

                     while (off < stop) {

                         Bits.putInt(buf, pos, v[off++]);

                         pos += 4;

                     }

                 } else {

                     dout.writeInt(v[off++]);

                 }

             }

         }

         void writeFloats(float[] v, int off, int len) throws IOException {

             int limit = MAX_BLOCK_SIZE - 4;

             int endoff = off + len;

             while (off < endoff) {

                 if (pos <= limit) {

                     int avail = (MAX_BLOCK_SIZE - pos) >> 2;

                     int chunklen = Math.min(endoff - off, avail);

                     floatsToBytes(v, off, buf, pos, chunklen);

                     off += chunklen;

                     pos += chunklen << 2;

                 } else {

                     dout.writeFloat(v[off++]);

                 }

             }

         }

         void writeLongs(long[] v, int off, int len) throws IOException {

             int limit = MAX_BLOCK_SIZE - 8;

             int endoff = off + len;

             while (off < endoff) {

                 if (pos <= limit) {

                     int avail = (MAX_BLOCK_SIZE - pos) >> 3;

                     int stop = Math.min(endoff, off + avail);

                     while (off < stop) {

                         Bits.putLong(buf, pos, v[off++]);

                         pos += 8;

                     }

                 } else {

                     dout.writeLong(v[off++]);

                 }

             }

         }

         void writeDoubles(double[] v, int off, int len) throws IOException {

             int limit = MAX_BLOCK_SIZE - 8;

             int endoff = off + len;

             while (off < endoff) {

                 if (pos <= limit) {

                     int avail = (MAX_BLOCK_SIZE - pos) >> 3;

                     int chunklen = Math.min(endoff - off, avail);

                     doublesToBytes(v, off, buf, pos, chunklen);

                     off += chunklen;

                     pos += chunklen << 3;

                 } else {

                     dout.writeDouble(v[off++]);

                 }

             }

         }

         /**

          * Returns the length in bytes of the UTF encoding of the given string.

          */

         long getUTFLength(String s) {

             int len = s.length();

             long utflen = 0;

             for (int off = 0; off < len; ) {

                 int csize = Math.min(len - off, CHAR_BUF_SIZE);

                 s.getChars(off, off + csize, cbuf, 0);

                 for (int cpos = 0; cpos < csize; cpos++) {

                     char c = cbuf[cpos];

                     if (c >= 0x0001 && c <= 0x007F) {

                         utflen++;

                     } else if (c > 0x07FF) {

                         utflen += 3;

                     } else {

                         utflen += 2;

                     }

                 }

                 off += csize;

             }

             return utflen;

         }

         /**

          * Writes the given string in UTF format.  This method is used in

          * situations where the UTF encoding length of the string is already

          * known; specifying it explicitly avoids a prescan of the string to

          * determine its UTF length.

          */

         void writeUTF(String s, long utflen) throws IOException {

             if (utflen > 0xFFFFL) {

                 throw new UTFDataFormatException();

             }

             writeShort((int) utflen);

             if (utflen == (long) s.length()) {

                 writeBytes(s);

             } else {

                 writeUTFBody(s);

             }

         }

         /**

          * Writes given string in "long" UTF format.  "Long" UTF format is

          * identical to standard UTF, except that it uses an 8 byte header

          * (instead of the standard 2 bytes) to convey the UTF encoding length.

          */

         void writeLongUTF(String s) throws IOException {

             writeLongUTF(s, getUTFLength(s));

         }

         /**

          * Writes given string in "long" UTF format, where the UTF encoding

          * length of the string is already known.

          */

         void writeLongUTF(String s, long utflen) throws IOException {

             writeLong(utflen);

             if (utflen == (long) s.length()) {

                 writeBytes(s);

             } else {

                 writeUTFBody(s);

             }

         }

         /**

          * Writes the "body" (i.e., the UTF representation minus the 2-byte or

          * 8-byte length header) of the UTF encoding for the given string.

          */

         private void writeUTFBody(String s) throws IOException {

             int limit = MAX_BLOCK_SIZE - 3;

             int len = s.length();

             for (int off = 0; off < len; ) {

                 int csize = Math.min(len - off, CHAR_BUF_SIZE);

                 s.getChars(off, off + csize, cbuf, 0);

                 for (int cpos = 0; cpos < csize; cpos++) {

                     char c = cbuf[cpos];

                     if (pos <= limit) {

                         if (c <= 0x007F && c != 0) {

                             buf[pos++] = (byte) c;

                         } else if (c > 0x07FF) {

                             buf[pos + 2] = (byte) (0x80 | ((c >> 0) & 0x3F));

                             buf[pos + 1] = (byte) (0x80 | ((c >> 6) & 0x3F));

                             buf[pos + 0] = (byte) (0xE0 | ((c >> 12) & 0x0F));

                             pos += 3;

                         } else {

                             buf[pos + 1] = (byte) (0x80 | ((c >> 0) & 0x3F));

                             buf[pos + 0] = (byte) (0xC0 | ((c >> 6) & 0x1F));

                             pos += 2;

                         }

                     } else {    // write one byte at a time to normalize block

                         if (c <= 0x007F && c != 0) {

                             write(c);

                         } else if (c > 0x07FF) {

                             write(0xE0 | ((c >> 12) & 0x0F));

                             write(0x80 | ((c >> 6) & 0x3F));

                             write(0x80 | ((c >> 0) & 0x3F));

                         } else {

                             write(0xC0 | ((c >> 6) & 0x1F));

                             write(0x80 | ((c >> 0) & 0x3F));

                         }

                     }

                 }

                 off += csize;

             }

         }

     }

     /**

      * Lightweight identity hash table which maps objects to integer handles,

      * assigned in ascending order.

      */

     private static class HandleTable {

         /* number of mappings in table/next available handle */

         private int size;

         /* size threshold determining when to expand hash spine */

         private int threshold;

         /* factor for computing size threshold */

         private final float loadFactor;

         /* maps hash value -> candidate handle value */

         private int[] spine;

         /* maps handle value -> next candidate handle value */

         private int[] next;

         /* maps handle value -> associated object */

         private Object[] objs;

         /**

          * Creates new HandleTable with given capacity and load factor.

          */

         HandleTable(int initialCapacity, float loadFactor) {

             this.loadFactor = loadFactor;

             spine = new int[initialCapacity];

             next = new int[initialCapacity];

             objs = new Object[initialCapacity];

             threshold = (int) (initialCapacity * loadFactor);

             clear();

         }

         /**

          * Assigns next available handle to given object, and returns handle

          * value.  Handles are assigned in ascending order starting at 0.

          */

         int assign(Object obj) {

             if (size >= next.length) {

                 growEntries();

             }

             if (size >= threshold) {

                 growSpine();

             }

             insert(obj, size);

             return size++;

         }

         /**

          * Looks up and returns handle associated with given object, or -1 if

          * no mapping found.

          */

         int lookup(Object obj) {

             if (size == 0) {

                 return -1;

             }

             int index = hash(obj) % spine.length;

             for (int i = spine[index]; i >= 0; i = next[i]) {

                 if (objs[i] == obj) {

                     return i;

                 }

             }

             return -1;

         }

         /**

          * Resets table to its initial (empty) state.

          */

         void clear() {

             Arrays.fill(spine, -1);

             Arrays.fill(objs, 0, size, null);

             size = 0;

         }

         /**

          * Returns the number of mappings currently in table.

          */

         int size() {

             return size;

         }

         /**

          * Inserts mapping object -> handle mapping into table.  Assumes table

          * is large enough to accommodate new mapping.

          */

         private void insert(Object obj, int handle) {

             int index = hash(obj) % spine.length;

             objs[handle] = obj;

             next[handle] = spine[index];

             spine[index] = handle;

         }

         /**

          * Expands the hash "spine" -- equivalent to increasing the number of

          * buckets in a conventional hash table.

          */

         private void growSpine() {

             spine = new int[(spine.length << 1) + 1];

             threshold = (int) (spine.length * loadFactor);

             Arrays.fill(spine, -1);

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

                 insert(objs[i], i);

             }

         }

         /**

          * Increases hash table capacity by lengthening entry arrays.

          */

         private void growEntries() {

             int newLength = (next.length << 1) + 1;

             int[] newNext = new int[newLength];

             System.arraycopy(next, 0, newNext, 0, size);

             next = newNext;

             Object[] newObjs = new Object[newLength];

             System.arraycopy(objs, 0, newObjs, 0, size);

             objs = newObjs;

         }

         /**

          * Returns hash value for given object.

          */

         private int hash(Object obj) {

             return System.identityHashCode(obj) & 0x7FFFFFFF;

         }

     }

     /**

      * Lightweight identity hash table which maps objects to replacement

      * objects.

      */

     private static class ReplaceTable {

         /* maps object -> index */

         private final HandleTable htab;

         /* maps index -> replacement object */

         private Object[] reps;

         /**

          * Creates new ReplaceTable with given capacity and load factor.

          */

         ReplaceTable(int initialCapacity, float loadFactor) {

             htab = new HandleTable(initialCapacity, loadFactor);

             reps = new Object[initialCapacity];

         }

         /**

          * Enters mapping from object to replacement object.

          */

         void assign(Object obj, Object rep) {

             int index = htab.assign(obj);

             while (index >= reps.length) {

                 grow();

             }

             reps[index] = rep;

         }

         /**

          * Looks up and returns replacement for given object.  If no

          * replacement is found, returns the lookup object itself.

          */

         Object lookup(Object obj) {

             int index = htab.lookup(obj);

             return (index >= 0) ? reps[index] : obj;

         }

         /**

          * Resets table to its initial (empty) state.

          */

         void clear() {

             Arrays.fill(reps, 0, htab.size(), null);

             htab.clear();

         }

         /**

          * Returns the number of mappings currently in table.

          */

         int size() {

             return htab.size();

         }

         /**

          * Increases table capacity.

          */

         private void grow() {

             Object[] newReps = new Object[(reps.length << 1) + 1];

             System.arraycopy(reps, 0, newReps, 0, reps.length);

             reps = newReps;

         }

     }

     /**

      * Stack to keep debug information about the state of the

      * serialization process, for embedding in exception messages.

      */

     private static class DebugTraceInfoStack {

         private final List<String> stack;

         DebugTraceInfoStack() {

             stack = new ArrayList<>();

         }

         /**

          * Removes all of the elements from enclosed list.

          */

         void clear() {

             stack.clear();

         }

         /**

          * Removes the object at the top of enclosed list.

          */

         void pop() {

             stack.remove(stack.size()-1);

         }

         /**

          * Pushes a String onto the top of enclosed list.

          */

         void push(String entry) {

             stack.add("\t- " + entry);

         }

         /**

          * Returns a string representation of this object

          */

         public String toString() {

             StringBuilder buffer = new StringBuilder();

             if (!stack.isEmpty()) {

                 for(int i = stack.size(); i > 0; i-- ) {

                     buffer.append(stack.get(i-1) + ((i != 1) ? "\n" : ""));

                 }

             }

             return buffer.toString();

         }

     }

 }