Java 1.2 How-To/JavaHowTo.iso/3rdParty/jbuilder/unsupported/JDK1.2beta3/SOURCE/SRC.ZIP/java/io/ObjectOutputStream.java

Java Source | 1998-03-20 | 55.1 KB | 1,769 lines

/*
 * @(#)ObjectOutputStream.java    1.64 98/03/18
 *
 * Copyright 1996-1998 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

package java.io;

import java.lang.reflect.InvocationTargetException;
import java.util.Stack;
import java.lang.reflect.InvocationTargetException;
import java.security.AccessController;

/**
 * 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 reconsituted
 * 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 <STRONG>writeObject</STRONG> 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 ostream = new FileOutputStream("t.tmp");
 *    ObjectOutputStream p = new ObjectOutputStream(ostream);
 *
 *    p.writeInt(12345);
 *    p.writeObject("Today");
 *    p.writeObject(new Date());
 *
 *    p.flush();
 *    ostream.close();
 *
 * </PRE>
 *
 * Classes that require special handling during the serialization and deserialization
 * process must implement special methods with these exact signatures: <p>
 *
 * <PRE>
 * private void readObject(java.io.ObjectInputStream stream)
 *     throws IOException, ClassNotFoundException;
 * private void writeObject(java.io.ObjectOutputStream stream)
 *     throws IOException
 * </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.
 *
 * 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.
 *
 * 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    Roger Riggs
 * @version     1.64, 03/18/98
 * @see java.io.DataOutput
 * @see java.io.ObjectInputStream
 * @see java.io.Serializable
 * @see java.io.Externalizable
 * @since       JDK1.1
 */
public class ObjectOutputStream
    extends OutputStream
    implements ObjectOutput, ObjectStreamConstants

{
    /**
     * Creates an ObjectOutputStream that writes to the specified OutputStream.
     * The stream header is written to the stream. The caller may want to call
     * flush immediately so that the corresponding ObjectInputStream can read
     * the header immediately.
     *
     * @exception IOException Any exception thrown by the underlying OutputStream.

     */
    public ObjectOutputStream(OutputStream out) throws IOException {
    enableSubclassImplementation = false;
    this.out = out;
    dos = new DataOutputStream(this);
    buf = new byte[1024];    // allocate buffer
    writeStreamHeader();
    resetStream();
    }

    /**
     * Provide a way for subclasses that are completely reimplementing
     * ObjectOutputStream to not have to allocate private data just used by
     * this implementation of ObjectOutputStream.
     *
     * Add the following line to the security policy file to enable
     * subclassing.
     *
     * <PRE>
     *        permission SerializablePermission "enableSubclassImplementation" ;
     * </PRE><p>
     *
     *
     * @exception IOException   Thrown if not called by a subclass.
     * @exception SecurityException if subclass does not have
     *                 SerializablePermission "enableSubclassImplementation".
     */
    protected ObjectOutputStream() throws IOException, SecurityException {
    SecurityManager sm = System.getSecurityManager();
    if (sm != null) sm.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
    enableSubclassImplementation = true;
    }

    /**
     * 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".
     *
     * @see #ObjectOutputStream()
     * @see @writeObject
     * @since JDK 1.2
     */
    protected void writeObjectOverride(Object obj) throws IOException
    {
    }

    /**
     * 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.<p>
     *
     * @param version   use ProtocolVersion from java.io.ObjectStreamConstants.
     * @exception IllegalStateException   Thrown if called after any objects have
     *                          been serialized.
     * @exception IllegalArgument if invalid version is passed in.
     *
     * @see java.io.ObjectStreamConstants#IntialProtocolVersion
     */
    public void useProtocolVersion(int version) throws IOException {
    if (nextWireOffset != 0)
        throw new IllegalStateException("Must call useProtocolVersion before writing any objects to the stream");

    switch (version) {
    case PROTOCOL_VERSION_1:
        useDeprecatedExternalizableFormat = true;
        break;
    case PROTOCOL_VERSION_2:
        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.
     * @exception InvalidClassException Something is wrong with a class used by
     *       serialization.
     * @exception NotSerializableException Some object to be serialized does not
     *      implement the java.io.Serializable interface.
     * @exception IOException Any exception thrown by the underlying OutputStream.
     */
    public final void writeObject(Object obj)
    throws IOException
    {
    if (enableSubclassImplementation) {
        writeObjectOverride(obj);
        return;
    }

    Object prevObject = currentObject;
    ObjectStreamClass prevClassDesc = currentClassDesc;
    boolean oldBlockDataMode = setBlockData(false);
    recursionDepth++;

    try {
        if (serializeNullAndRepeat(obj))
        return;

        if (checkSpecialClasses(obj))
        return;

        Object altobj = obj;

        /* Allow the class to replace the instance to be serialized. */
        if (obj instanceof Replaceable)
        altobj = ((Replaceable)obj).writeReplace();

        /* If the replacment is enabled, give subclasses one chance
         * to substitute a new object. If one is substituted,
         * recheck for null, repeated refs, and special cased classes
         */
        if (enableReplace) {
        altobj = replaceObject(altobj);
        }

        /* If the object has been replaced check that the object
         * is serializable and recheck for the special cases.
         */
        if (obj != altobj) {
        if (altobj != null && !(altobj instanceof Serializable)) {
            String clname = altobj.getClass().getName();
            throw new NotSerializableException(clname);
        }

        // If the alternate object is already
        // serialized just remember the replacement
        if (serializeNullAndRepeat(altobj)) {
            addReplacement(obj, altobj);
            return;
        }

        /* Add this to the set of replaced objects.
         * This must be done before the object is
         * serialized so that if the object indirectly
         * refers to the original it will be redirected to
         * the replacement.
         *
         * NB: checkSpecialClasses should only call
         * serializeNullandRepeat for objects that will not
         * recurse.
         */
        addReplacement(obj, altobj);

        if (checkSpecialClasses(altobj))
            return;

        obj = altobj;
        }

        if (checkSubstitutableSpecialClasses(obj))
        return;
        else {
        /* Write out the object as itself */
        outputObject(obj);
        }
    } catch (IOException ee) {
        if (abortIOException == null) {
        try {
            /* Prepare to write the exception to the stream.
             * End blockdatamode in case it's set
             * Write the exception code
             * reset the stream to forget all previous objects
             * write the exception that occurred
             * reset the stream again so subsequent objects won't map to
             * the exception or its args.
             * Continue below to rethrow the exception.
             */
            setBlockData(false);

            writeCode(TC_EXCEPTION);
            resetStream();
            setBlockData(false); //added since resetStream set to TRUE.
            this.outputObject(ee); //avoid recursing with writeObject
            resetStream();

            // Set the pending exception to be rethrown.
            abortIOException = ee;
        } catch (IOException fatal) {
            /* An exception occurred while writing the original exception to
             * the stream.  The original exception is not complete in
             * the stream and recusion would be bad. Supercede the original
             * Exception with a StreamCorruptedException using the message
             * from this current exception.
             */
            abortIOException =
            new StreamCorruptedException(fatal.getMessage());
        }
        }
    } finally {
        /* Restore state of previous call incase this is a nested call */
        recursionDepth--;
        currentObject = prevObject;
        currentClassDesc = prevClassDesc;
        setBlockData(oldBlockDataMode);
    }

    /* If the recursion depth is 0, test for and clear the pending exception.
     * If there is a pending exception throw it.
     */
    IOException pending = abortIOException;
    if (recursionDepth == 0)
        abortIOException = null;
    if (pending != null) {
        throw pending;
    }
    }

    /*
     * Check for special cases of serializing objects.
     * These objects are not subject to replacement.
     */
    private boolean checkSpecialClasses(Object obj) throws IOException {

    /*
     * If this is a class, don't allow substitution
     */
    if (obj instanceof Class) {
        outputClass((Class)obj);
        return true;
    }

    if (obj instanceof ObjectStreamClass) {
        outputClassDescriptor((ObjectStreamClass)obj);
        return true;
    }

    return false;
    }

    /*
     * Check for special cases of substitutable serializing objects.
     * These classes are replaceable.
     */
    private boolean checkSubstitutableSpecialClasses(Object obj)
    throws IOException
    {
    if (obj instanceof String) {
        outputString((String)obj);
        return true;
    }

    if (obj.getClass().isArray()) {
        outputArray(obj);
        return true;
    }

    return false;
    }

    /**
     * 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.
     */
    public void defaultWriteObject() throws IOException {
    if (currentObject == null || currentClassDesc == null)
        throw new NotActiveException("defaultWriteObject");

    ObjectStreamField[] fields =
        currentClassDesc.getFieldsNoCopy();
    if (fields.length > 0) {
        boolean prevmode = setBlockData(false);
        outputClassFields(currentObject, currentClassDesc.forClass(),
                  fields);
        setBlockData(prevmode);
    }
    }

    /**
     * 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.
     *
     * @since JDK1.2
     */
    public ObjectOutputStream.PutField putFields() throws IOException {
    if (currentObject == null || currentClassDesc == null)
        throw new NotActiveException("putFields");
        // TBD: check if defaultWriteObject has already been called.
        currentPutFields = new ObjectOutputStream.PutFieldImpl(currentClassDesc);
        return currentPutFields;
    }

    /**
     * Write the buffered fields to the stream.
     *
     * @since JDK1.2
     * @exception NotActiveException Called when a classes writeObject
     * method was not called to write the state of the object.
     */
    public void writeFields() throws IOException {
        if (currentObject == null || currentClassDesc == null || currentPutFields == null)
            throw new NotActiveException("writeFields");

    boolean prevmode = setBlockData(false);
        currentPutFields.write(this);
    setBlockData(prevmode);
    }

    /**
     * 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.
     */
    public void reset() throws IOException {
    if (currentObject != null || currentClassDesc != null)
        throw new IOException("Illegal call to reset");

    /* Write a reset to the stream. */
    setBlockData(false);
    writeCode(TC_RESET);

    resetStream();            // re-init the stream
    abortIOException = null;
    }

    /*
     * Internal reset function to reinitialize the state of the stream.
     * Reset state of things changed by using the stream.
     */
    private void resetStream() throws IOException {
    if (wireHandle2Object == null) {
        wireHandle2Object = new Object[100];
        wireNextHandle = new int[100];
        wireHash2Handle = new int[101];
    } else {

        // Storage Optimization for frequent calls to reset method.
        // Do not reallocate, only reinitialize.
        for (int i = 0; i < nextWireOffset; i++) {
        wireHandle2Object[i] = null;
        wireNextHandle[i] = 0;
        }
    }
      nextWireOffset = 0;
      for (int i = 0; i < wireHash2Handle.length; i++) {
          wireHash2Handle[i] = -1;
      }

    if (classDescStack == null)
        classDescStack = new Stack();
    else
        classDescStack.setSize(0);

    for (int i = 0; i < nextReplaceOffset; i++)
        replaceObjects[i] = null;
    nextReplaceOffset = 0;

      setBlockData(true);        /* Re-enable buffering */
      }

    /**
     * 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.
     *
     * @exception IOException Any exception thrown by the underlying OutputStream.
     */
    protected void annotateClass(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 replacment can be
     * trusted. Every reference to serializable objects is passed to
     * replaceObject.  To insure that the private state of objects is
     * not unintentionally exposed only trusted streams may use
     * replaceObject. <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.<p>
     *
     * @exception 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.
     * If the stream is a trusted class it is allowed to enable replacement.
     *
     *
     * When enabled the replaceObject method is called for every object
     * being serialized.
     *
     * Add the following line to the security policy file to enable
     * replaceObject() to be overriden by the subclass of ObjectOutputStream.
     *
     *        permission SerializablePermission "enableSubstitution" ;
     *
     * @exception java.security.SecurityException
     *             if SerializablePermission "enableSubstitution"
     *             is not allowed by the security policy.
     */
    protected boolean enableReplaceObject(boolean enable)
    throws SecurityException
    {
    boolean previous = enableReplace;
    if (enable) {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) sm.checkPermission(SUBSTITUTION_PERMISSION);
         enableReplace = true;
    } else {
        enableReplace = false;
    }
    return previous;
    }

    /**
     * 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.
     */
    protected void writeStreamHeader() throws IOException {
    writeShort(STREAM_MAGIC);
    writeShort(STREAM_VERSION);
    }

    /**
     * Write a string to the stream.
     * Note that since Strings are Objects, writeObject
     * will behave identically.
     */
    private void outputString(String s) throws IOException {
    /* Allocate a write handle but don't write it to the stream,
     * Write out the code for a string,
     * the read can regenerate the same sequence and it saves bytes.
     */
    assignWireOffset(s);
    writeCode(TC_STRING);
    writeUTF(s);
    }


    /* Classes are special, they can not be created during deserialization,
     * but the appropriate class can be found.
     */
    private void outputClass(Class aclass) throws IOException {

    writeCode(TC_CLASS);
    /* Find the class descriptor and write it out */
    ObjectStreamClass v = ObjectStreamClass.lookupInternal(aclass);
    if (v == null)
        throw new NotSerializableException(aclass.getName());

    outputClassDescriptor(v);

    assignWireOffset(aclass);
    }


    /* Write the class descriptor */
    private void outputClassDescriptor(ObjectStreamClass classdesc)
    throws IOException
    {
    if (serializeNullAndRepeat(classdesc))
        return;

    /* Write out the code for a class
     * Write out the class name and its serialVersionUID
     */
    writeCode(TC_CLASSDESC);
    String classname = classdesc.getName();

    writeUTF(classname);
    writeLong(classdesc.getSerialVersionUID());

    /* This is done here to be symetric with the inputClass method
     * Since the resolveClassName() method may use the stream.
     * The assignments of wirehandles must be done in the same order
     */
    assignWireOffset(classdesc);

    /* Write the version description for this class */
    classdesc.write(this);

    /* Give subclassers a chance to add the class implementation
     * to the stream.  Set BlockData mode so any information they
     * write can be skipped on reading.
     */
    boolean prevMode = setBlockData(true);
    annotateClass(classdesc.forClass());
    setBlockData(prevMode);
    writeCode(TC_ENDBLOCKDATA);

    /*
     * Write out the superclass descriptor of this descriptor
     * only if it is for a java.io.Serializable class.
     * else write null.
     */
    ObjectStreamClass superdesc = classdesc.getSuperclass();
    outputClassDescriptor(superdesc);
    }

    /**
     * Write an array out. Note that since Arrays are Objects, writeObject(obj)
     * will behave identically. <br><br>
     * @param o can represent an array of any type/dimension.
     */
    private void outputArray(Object obj)
    throws IOException
    {
    Class currclass = obj.getClass();

    ObjectStreamClass v = ObjectStreamClass.lookup(currclass);

    /* Write out the code for an array and the name of the class */
    writeCode(TC_ARRAY);
    outputClassDescriptor(v);

    /* Assign the wirehandle for this object and outputArrayValues
     * writes the length and the array contents.
     */
    assignWireOffset(obj);

    int i, length;
    Class type = currclass.getComponentType();

    if (type.isPrimitive()) {
        /* Write arrays of primitive types using the DataOutput
         * methods that convert each element into the output buffer.
         * The data types are ordered by the frequency
         * in which they are expected to occur.
         */
        if (type == Integer.TYPE) {
        int[] array = (int[])obj;
        length = array.length;
        writeInt(length);
        for (i = 0; i < length; i++) {
            writeInt(array[i]);
        }
        } else if (type == Byte.TYPE) {
        byte[] array = (byte[])obj;
        length = array.length;
        writeInt(length);
        write(array, 0, length);
        } else if (type == Long.TYPE) {
        long[] array = (long[])obj;
        length = array.length;
        writeInt(length);
        for (i = 0; i < length; i++) {
            writeLong(array[i]);
        }
        } else if (type == Float.TYPE) {
        float[] array = (float[])obj;
        length = array.length;
        writeInt(length);
        for (i = 0; i < length; i++) {
            writeFloat(array[i]);
        }
        } else if (type == Double.TYPE) {
        double[] array = (double[])obj;
        length = array.length;
        writeInt(length);
        for (i = 0; i < length; i++) {
            writeDouble(array[i]);
        }
        } else if (type == Short.TYPE) {
        short[] array = (short[])obj;
        length = array.length;
        writeInt(length);
        for (i = 0; i < length; i++) {
            writeShort(array[i]);
        }
        } else if (type == Character.TYPE) {
        char[] array = (char[])obj;
        length = array.length;
        writeInt(length);
        for (i = 0; i < length; i++) {
            writeChar(array[i]);
        }
        } else if (type == Boolean.TYPE) {
        boolean[] array = (boolean[])obj;
        length = array.length;
        writeInt(length);
        for (i = 0; i < length; i++) {
            writeBoolean(array[i]);
        }
        } else {
        throw new InvalidClassException(currclass.getName());
        }
    } else {
        Object[] array = (Object[])obj;
        length = array.length;
        writeInt(length);
        for (i = 0; i < length; i++) {
        writeObject(array[i]);
        }
    }
    }

    /*
     * Put the object into the stream The newObject code is written
     * followed by the ObjectStreamClass for the object's class.  Each
     * of the objects classes is written using the default
     * serialization code and dispatching to Specials where
     * appropriate.
     */
    private void outputObject(Object obj)
    throws IOException
    {
    currentObject = obj;
    Class currclass = obj.getClass();

    /* Get the Class descriptor for this class,
     * Throw a NotSerializableException if there is none.
     */
    currentClassDesc = ObjectStreamClass.lookup(currclass);
    if (currentClassDesc == null) {
        throw new NotSerializableException(currclass.getName());
    }

    /* Write the code to expect an instance and
     * the class descriptor of the instance
     */
    writeCode(TC_OBJECT);
    outputClassDescriptor(currentClassDesc);

    /* Assign the next wirehandle */
    assignWireOffset(obj);

    /* If the object is externalizable,
     * call writeExternal.
     * else do Serializable processing.
     */
    if (currentClassDesc.isExternalizable()) {
        Externalizable ext = (Externalizable)obj;
        if (useDeprecatedExternalizableFormat) {

        /* JDK 1.1 external data format.
         * Don't write in block data mode and no terminator tag.
         */
        ext.writeExternal(this);
        } else {

        /* JDK 1.2 Externalizable data format writes in block data mode
         * and terminates externalizable data with TAG_ENDBLOCKDATA.
         */
        setBlockData(true);
        try {
            ext.writeExternal(this);
        } finally {
            setBlockData(false);
            writeCode(TC_ENDBLOCKDATA);
        }
        }
    } else {

        /* The object's classes should be processed from supertype to subtype
         * Push all the clases of the current object onto a stack.
         * Remember the stack pointer where this set of classes is being pushed.
         */
        int stackMark = classDescStack.size();
        try {
        ObjectStreamClass next;
        while ((next = currentClassDesc.getSuperclass()) != null) {
            classDescStack.push(currentClassDesc);
            currentClassDesc = next;
        }

        /*
         * For currentClassDesc and all the pushed class descriptors
         *    If the class is writing its own data
         *          set blockData = true; call the class writeObject method
         *    If not
         *     invoke either the defaultWriteObject method.
         */
        do {
            if (currentClassDesc.hasWriteObject()) {
            setBlockData(true); /* Block any data the class writes */
            invokeObjectWriter(obj, currentClassDesc.forClass());
            setBlockData(false);
            writeCode(TC_ENDBLOCKDATA);
            } else {
            defaultWriteObject();
            }
        } while (classDescStack.size() > stackMark &&
             (currentClassDesc = (ObjectStreamClass)classDescStack.pop()) != null);
        } finally {
        classDescStack.setSize(stackMark);
        }
    }
    }

    /*
     * Return a replacement for 'forObject', if one exists.
     */
    private Object lookupReplace(Object obj) {
    for (int i = 0; i < nextReplaceOffset; i+= 2) {
        if (replaceObjects[i] == obj)
        return replaceObjects[i+1];
    }
    return obj;
    }


    /* Serialize the reference if it is NULL or is for an object that
     * was already replaced or already serialized.
     * If the object was already replaced, look for the replacement
     * object in the known objects and if found, write its handle
     * Return True if the reference is either null or a repeat.
     */
    private boolean serializeNullAndRepeat(Object obj)
    throws IOException
    {
        if (obj == null) {
        writeCode(TC_NULL);
        return true;
    }

    /* Look to see if this object has already been replaced.
     * If so, proceed using the replacement object.
     */
    if (replaceObjects != null) {
        obj = lookupReplace(obj);
    }

    int handle = findWireOffset(obj);
    if (handle >= 0) {
        /* Add a reference to the stream */
        writeCode(TC_REFERENCE);
        writeInt(handle + baseWireHandle);
        return true;
    }
    return false;        // not serialized, its up to the caller
    }

    /*
     * Locate and return if found the handle for the specified object.
     * -1 is returned if the object does not occur in the array of
     * known objects.
     */
    private int findWireOffset(Object obj) {
    int hash = System.identityHashCode(obj);
    int index = (hash & 0x7FFFFFFF) % wireHash2Handle.length;

    for (int handle = wireHash2Handle[index];
         handle >= 0;
         handle = wireNextHandle[handle]) {

        if (wireHandle2Object[handle] == obj)
        return handle;
    }
    return -1;
    }

    /* Allocate a handle for an object.
     * The Vector is indexed by the wireHandleOffset
     * and contains the object.
     */
    private void assignWireOffset(Object obj)
    throws IOException
    {
    // Extend the array if there isn't room for this new element
    if (nextWireOffset == wireHandle2Object.length) {
        Object[] oldhandles = wireHandle2Object;
        wireHandle2Object = new Object[nextWireOffset*2];
        System.arraycopy(oldhandles, 0,
                 wireHandle2Object, 0,
                 nextWireOffset);
        int[] oldnexthandles = wireNextHandle;
        wireNextHandle = new int[nextWireOffset*2];
        System.arraycopy(oldnexthandles, 0,
                 wireNextHandle, 0,
                 nextWireOffset);
        // TBD: Rehash the hash array if necessary
    }
    wireHandle2Object[nextWireOffset] = obj;

    hashInsert(obj, nextWireOffset);

    nextWireOffset++;
    return;
    }


    /*
     * Insert the specified object into the hash array and link if
     * necessary. Put the new object into the hash table and link the
     * previous to it. Newer objects occur earlier in the list.
     */
    private void hashInsert(Object obj, int offset) {
    int hash = System.identityHashCode(obj);
    int index = (hash & 0x7FFFFFFF) % wireHash2Handle.length;
    wireNextHandle[offset] = wireHash2Handle[index];
    wireHash2Handle[index] = offset;
    }

    /*
     * Add a replacement object to the table.
     * The even numbered indices are the original objects.
     * The odd numbered indices are the replacement objects.
     *
     */
    private void addReplacement(Object orig, Object replacement) {
    // Extend the array if there isn't room for this new element

    if (replaceObjects == null) {
        replaceObjects = new Object[10];
    }
    if (nextReplaceOffset == replaceObjects.length) {
        Object[] oldhandles = replaceObjects;
        replaceObjects = new Object[2+nextReplaceOffset*2];
        System.arraycopy(oldhandles, 0,
                 replaceObjects, 0,
                 nextReplaceOffset);
    }
    replaceObjects[nextReplaceOffset++] = orig;
    replaceObjects[nextReplaceOffset++] = replacement;
    }

    /* Write out the code indicating the type what follows.
     * See ObjectStreamConstants for definitions.
     */
    private void writeCode(int tag)
    throws IOException
    {
    writeByte(tag);
    }

    /*
     * Implement the OutputStream methods.  The stream has
     * two modes used internally to ObjectOutputStream.  When
     * in BlockData mode, all writes are buffered and written
     * to the underlying stream prefixed by a code and length.
     * When not in BlockData mode (false), writes pass directly
     * through to the underlying stream.
     * The BlockData mode is used to encapsulate data written
     * by class specific writeObject methods that is intended
     * only to be read by corresponding readObject method of the
     * same class.  The blocking of data allows it to be skipped
     * if necessary.
     *
     * The setBlockData method is used to switch buffering
     * on and off.  When switching between on and off
     * the buffer is drained.
     *
     * The actual buffering is very similar to that of
     * BufferedOutputStream but BufferedOutputStream can
     * write to the underlying stream without the headers.
     */
    private boolean blockDataMode;    /* true to buffer and block data */
    private byte[] buf;        /* byte array of buffered data. */
    private int count;        /* count of bytes in the buffer */
    private OutputStream out;    /* Stream to write the data to */

    /**
     * Writes a byte. This method will block until the byte is actually
     * written.
     * @param b    the byte
     * @exception IOException If an I/O error has occurred.
     */
    public void write(int data) throws IOException {

    if (count >= buf.length)
        drain();        /* Drain, make room for more */
    buf[count++] = (byte)data;
    }

    /**
     * Writes an array of bytes. This method will block until the bytes
     * are actually written.
     * @param b    the data to be written
     * @exception IOException If an I/O error has occurred.
     */
    public void write(byte b[]) throws IOException {
    write(b, 0, b.length);
    }

    /**
     * Writes a sub array of bytes.
     * @param b    the data to be written
     * @param off    the start offset in the data
     * @param len    the number of bytes that are written
     * @exception IOException If an I/O error has occurred.
     */
    public void write(byte b[], int off, int len) throws IOException {
    if (len < 0)
        throw new IndexOutOfBoundsException();

    if (blockDataMode) {
        writeCanonical(b, off, len);
    } else {
        /*
         * If array will fit in output buffer, copy it in there; otherwise,
         * drain anything in the buffer and send it through to underlying
         * output stream directly.
         */
        int avail = buf.length - count;
        if (len <= avail) {
        System.arraycopy(b, off, buf, count, len);
        count += len;
        } else {
        drain();
        out.write(b, off, len);
        }
    }
    }

    /**
     * Flushes the stream. This will write any buffered
     * output bytes and flush through to the underlying stream.
     * @exception IOException If an I/O error has occurred.
     */
    public void flush() throws IOException {
    drain();
    out.flush();
    }

    /**
     * Drain any buffered data in ObjectOutputStream.  Similar to flush
     * but does not propagate the flush to the underlaying stream.
     */
    protected void drain() throws IOException {
    /*
     * Drain the data buffer.
     * If the blocking mode is on, prepend the buffer
     * with the code for a blocked data and the length.
     * The code is TC_BLOCKDATA and the length is < 255 so it fits
     * in a byte.
     */
    if (count == 0)
        return;

    if (blockDataMode)
        writeBlockDataHeader(count);
    out.write(buf, 0, count);
    count = 0;
    }

    /**
     * Closes the stream. This method must be called
     * to release any resources associated with the
     * stream.
     * @exception IOException If an I/O error has occurred.
     */
    public void close() throws IOException {
    flush();        /* Make sure we're not holding any data */
    out.close();
    }

    /*
     * Set the blockData mode,  if it turned from on to off
     * the buffer is drained.  The previous mode is returned.
     */
    private boolean setBlockData(boolean mode) throws IOException {
    if (blockDataMode == mode)
        return mode;
    drain();
    blockDataMode = mode;
    return !mode;        /* previous value was the opposite */
    }

    /* Write the Block-data marker and the length of the data to follow
     * to stream 'out'. If the length is < 256, use the short header form.
     * othewise use the long form.
     */
    private void writeBlockDataHeader(int len) throws IOException {
    if (len <= 255) {
        out.write(TC_BLOCKDATA);
        out.write((byte)len);
    } else {
        // use block data with int size if necessary
        out.write(TC_BLOCKDATALONG);
        // send 32 bit int directly to underlying stream
        out.write((byte)((len >> 24) & 0xFF));
        out.write((byte)((len >> 16) & 0xFF));
        out.write((byte)((len >>  8) & 0xFF));
        out.write((byte)(len & 0xFF));
    }
    }

    /* Canonical form requires constant blocking factor. Write data
     * in b array in constant block-data chunks.
     *
     * Assumes only called when blockDataMode is true.
     */
    private void writeCanonical(byte b[], int off, int len)
    throws IOException
    {
    int bufAvail = buf.length - count;
    int bytesToWrite = len;

    // Handle case where byte array is larger than available buffer.
    if (bytesToWrite > bufAvail) {
        // Logically: fill rest of 'buf' with 'b' and drain.
        // Optimization: avoid copying to 'buf', write partial 'buf' and partial
        //               'b' directly to 'out'.
        writeBlockDataHeader(buf.length);
        out.write(buf, 0, count);
        out.write(b, off, bufAvail);

        count = 0;
        off += bufAvail;
        bytesToWrite -= bufAvail;

        // Optimization: write 'buf.length' BlockData directly to stream.
        while (bytesToWrite >= buf.length) {
        if (blockDataMode)
            writeBlockDataHeader(buf.length);
        out.write(b, off, buf.length);
        off += buf.length;
        bytesToWrite -= buf.length;
        }
    }

    // Put remainder of byte array into buffer.
    if (bytesToWrite != 0) {
        System.arraycopy(b, off, buf, count, bytesToWrite);
        count += bytesToWrite;
    }
    }

    /* -------------------------------------------------------------- */
    /*
     * Provide the methods to implement DataOutput.
     * These are copied from DataOutputStream to avoid the overhead
     * of multiple method calls and to buffer the data directly.
     */
    private DataOutputStream dos;

    /**
     * Writes a boolean.
     * @param data the boolean to be written
     */
    public void writeBoolean(boolean data) throws IOException {
    if (count >= buf.length)
        drain();
    buf[count++] = (byte)(data ? 1 : 0);

    }

    /**
     * Writes an 8 bit byte.
     * @param data the byte value to be written
     */
    public void writeByte(int data) throws IOException  {
    if (count >= buf.length)
        drain();
    buf[count++] = (byte)data;
    }

    /**
     * Writes a 16 bit short.
     * @param data the short value to be written
     */
    public void writeShort(int data)  throws IOException {
    if (count + 2 > buf.length) {
        if (blockDataMode) {

        // normalize block-data record by writing a byte at a time.
        dos.writeShort(data);
        return;
        } else {
        drain();
        }
    }
    buf[count++] = (byte)((data >>>  8));
    buf[count++] = (byte)((data >>>  0));
    }

    /**
     * Writes a 16 bit char.
     * @param data the char value to be written
     */
    public void writeChar(int data)  throws IOException {
    if (count + 2 > buf.length) {
        if (blockDataMode) {

        // normalize block-data record by writing a byte at a time.
        dos.writeChar(data);
        return;
        } else {
        drain();
        }
    }
    buf[count++] = (byte)((data >>>  8));
    buf[count++] = (byte)((data >>>  0));
    }

    /**
     * Writes a 32 bit int.
     * @param data the integer value to be written
     */
    public void writeInt(int data)  throws IOException {
    if (count + 4 > buf.length) {
        if (blockDataMode) {

        // normalize block-data record by writing a byte at a time.
        dos.writeInt(data);
        return;
        } else {
        drain();
        }
    }
    buf[count++] = (byte)((data >>> 24));
    buf[count++] = (byte)((data >>> 16));
    buf[count++] = (byte)((data >>>  8));
    buf[count++] = (byte)((data >>>  0));
    }

    /**
     * Writes a 64 bit long.
     * @param data the long value to be written
     */
    public void writeLong(long data)  throws IOException {
    if (count + 8 > buf.length) {
        if (blockDataMode) {

        // normalize block-data record by writing a byte at a time.
        dos.writeLong(data);
        return;
        } else {
        drain();
        }
    }
    buf[count++] = (byte)((int)(data >>> 56));
    buf[count++] = (byte)((int)(data >>> 48));
    buf[count++] = (byte)((int)(data >>> 40));
    buf[count++] = (byte)((int)(data >>> 32));
    buf[count++] = (byte)((data >>> 24));
    buf[count++] = (byte)((data >>> 16));
    buf[count++] = (byte)((data >>>  8));
    buf[count++] = (byte)((data >>>  0));
    }

    /**
     * Writes a 32 bit float.
     * @param data the float value to be written
     */
    public void writeFloat(float data) throws IOException {
    int value = Float.floatToIntBits(data);
    if (count + 4 > buf.length) {
        if (blockDataMode) {

        // normalize block-data record by writing a byte at a time.
        dos.writeFloat(data);
        return;
        } else {
        drain();
        }
    }
    buf[count++] = (byte)((value >>> 24));
    buf[count++] = (byte)((value >>> 16));
    buf[count++] = (byte)((value >>>  8));
    buf[count++] = (byte)((value >>>  0));
    }

    /**
     * Writes a 64 bit double.
     * @param data the double value to be written
     */
    public void writeDouble(double data) throws IOException {
    long value = Double.doubleToLongBits(data);
    if (count + 8 > buf.length) {
        if (blockDataMode) {

        // normalize block-data record by writing a byte at a time.
        dos.writeDouble(data);
        return;
        } else {
        drain();
        }
    }
    buf[count++] = (byte)((int)(value >>> 56));
    buf[count++] = (byte)((int)(value >>> 48));
    buf[count++] = (byte)((int)(value >>> 40));
    buf[count++] = (byte)((int)(value >>> 32));
    buf[count++] = (byte)((value >>> 24));
    buf[count++] = (byte)((value >>> 16));
    buf[count++] = (byte)((value >>>  8));
    buf[count++] = (byte)((value >>>  0));
    }

    /**
     * Writes a String as a sequence of bytes.
     * @param s the String of bytes to be written
     */
    public void writeBytes(String data) throws IOException {
    dos.writeBytes(data);
    }

    /**
     * Writes a String as a sequence of chars.
     * @param s the String of chars to be written
     */
    public void writeChars(String data) throws IOException {
    dos.writeChars(data);
    }

    /**
     * Writes a String in UTF format.
     * @param str the String in UTF format
     */
    public void writeUTF(String data) throws IOException {
    dos.writeUTF(data);
    }

    /* Write the fields of the specified class by invoking the appropriate
     * write* method on this class.
     */
    private void outputClassFields(Object o, Class cl,
                   ObjectStreamField[] fields)
    throws IOException, InvalidClassException {

    for (int i = 0; i < fields.length; i++) {
        if (fields[i].getField() == null)
        throw new InvalidClassException(cl.getName(),
            "Nonexistent field " + fields[i].getName());

        try {
        switch (fields[i].getTypeCode()) {
        case 'B':
            byte byteValue = fields[i].getField().getByte(o);
            writeByte(byteValue);
                break;
        case 'C':
            char charValue = fields[i].getField().getChar(o);
            writeChar(charValue);
                break;
        case 'F':
            float floatValue = fields[i].getField().getFloat(o);
            writeFloat(floatValue);
                break;
        case 'D' :
            double doubleValue = fields[i].getField().getDouble(o);
            writeDouble(doubleValue);
            break;
        case 'I':
            int intValue = fields[i].getField().getInt(o);
            writeInt(intValue);
                break;
        case 'J':
            long longValue = fields[i].getField().getLong(o);
            writeLong(longValue);
            break;
        case 'S':
            short shortValue = fields[i].getField().getShort(o);
            writeShort(shortValue);
                break;
        case 'Z':
            boolean booleanValue = fields[i].getField().getBoolean(o);
            writeBoolean(booleanValue);
                break;
        case '[':
        case 'L':
            Object objectValue = fields[i].getField().get(o);
            writeObject(objectValue);
                break;
        default:
            throw new InvalidClassException(cl.getName());
        }
        } catch (IllegalAccessException e) {
        throw new InvalidClassException(cl.getName(), e.getMessage());
        }
    }
    }

    /*
     * Test if WriteObject method is present, and if so, invoke writer.
     */
    private void invokeObjectWriter(Object obj, Class c)
    throws IOException
    {
    try {
        AccessController.beginPrivileged();
        currentClassDesc.writeObjectMethod.invoke(obj, writeObjectArglist);
    } catch (InvocationTargetException e) {
        Throwable t = e.getTargetException();
        if (t instanceof IOException)
        throw (IOException)t;
        else if (t instanceof RuntimeException)
        throw (RuntimeException) t;
        else if (t instanceof Error)
        throw (Error) t;
        else
        throw new Error("interal error");
    } catch (IllegalAccessException e) {
        // cannot happen
    } finally {
        AccessController.endPrivileged();
    }
    }

    /*************************************/

    /**
     * Provide programatic access to the persistent fields to be written
     * to ObjectOutput.
     *
     * @since JDK 1.2
     */
    static public abstract class PutField {
    /**
     * Put the value of the named boolean field into the persistent field.
     */
    abstract public void put(String name, boolean value);

    /**
     * Put the value of the named char field into the persistent fields.
     */
    abstract public void put(String name, char value);

    /**
     * Put the value of the named byte field into the persistent fields.
     */
    abstract public void put(String name, byte value);

    /**
     * Put the value of the named short field into the persistent fields.
     */
    abstract public void put(String name, short value);

    /**
     * Put the value of the named int field into the persistent fields.
     */
    abstract public void put(String name, int value);

    /**
     * Put the value of the named long field into the persistent fields.
     */
    abstract public void put(String name, long value);

    /**
     * Put the value of the named float field into the persistent fields.
     */
    abstract public void put(String name, float value);

    /**
     * Put the value of the named double field into the persistent field.
     */
    abstract public void put(String name, double value);

    /**
     * Put the value of the named Object field into the persistent field.
     */
    abstract public void put(String name, Object value);

    /**
     * Write the data and fields to the specified ObjectOutput stream.
     */
    abstract public void write(ObjectOutput out) throws IOException;
    };

    /*************************************************************/


    /**
     * Provide access to the persistent fields to be written to the output stream.
     */
    static class PutFieldImpl extends PutField {
     /**
      * Put the value of the named boolean field into the persistent field.
      */
     public void put(String name, boolean value)
         throws IllegalArgumentException
     {
         ObjectStreamField field = desc.getField(name);
         if (field == null || field.getType() != Boolean.TYPE)
         throw new IllegalArgumentException("No such boolean field");
         data[field.getOffset()] = (byte)(value ? 1 : 0);
     }

     /**
      * Put the value of the named char field into the persistent fields.
      */
     public void put(String name, char value) {
         ObjectStreamField field = desc.getField(name);;
         if (field == null || field.getType() != Character.TYPE)
         throw new IllegalArgumentException("No such char field");
         data[field.getOffset()] = (byte)(value >> 8);
         data[field.getOffset()+1] = (byte)(value);
     }

     /**
      * Put the value of the named byte field into the persistent fields.
      */
     public void put(String name, byte value) {
         ObjectStreamField field = desc.getField(name);;
         if (field == null || field.getType() != Byte.TYPE)
         throw new IllegalArgumentException("No such byte field");
         data[field.getOffset()] = value;
     }

     /**
      * Put the value of the named short field into the persistent fields.
      */
     public void put(String name, short value) {
         ObjectStreamField field = desc.getField(name);;
         if (field == null || field.getType() != Short.TYPE)
         throw new IllegalArgumentException("No such short field");

         int loffset = field.getOffset();
         data[loffset] = (byte)(value >> 8);
         data[loffset+1] = (byte)(value);
     }

     /**
      * Put the value of the named int field into the persistent fields.
      */
     public void put(String name, int value) {
         ObjectStreamField field = desc.getField(name);
         if (field == null || field.getType() != Integer.TYPE)
         throw new IllegalArgumentException("No such int field");

         int loffset = field.getOffset();
         data[loffset] = (byte)(value >> 24);
         data[loffset+1] = (byte)(value >> 16);
         data[loffset+2] = (byte)(value >> 8);
         data[loffset+3] = (byte)value;
     }

     /**
      * Put the value of the named long field into the persistent fields.
      */
     public void put(String name, long value) {
         ObjectStreamField field = desc.getField(name);
         if (field == null || field.getType() != Long.TYPE)
         throw new IllegalArgumentException("No such long field");

         int loffset = field.getOffset();
         data[loffset] = (byte)(value >> 56);
         data[loffset+1] = (byte)(value >> 48);
         data[loffset+2] = (byte)(value >> 40);
         data[loffset+3] = (byte)(value >> 32);
         data[loffset+4] = (byte)(value >> 24);
         data[loffset+5] = (byte)(value >> 16);
         data[loffset+6] = (byte)(value >> 8);
         data[loffset+7] = (byte)value;
     }

     /**
      * Put the value of the named float field into the persistent fields.
      */
     public void put(String name, float value) {
         int val = Float.floatToIntBits(value);
         ObjectStreamField field = desc.getField(name);
         if (field == null || field.getType() != Float.TYPE)
         throw new IllegalArgumentException("No such float field");

         int loffset = field.getOffset();
         data[loffset] = (byte)(val >> 24);
         data[loffset+1] = (byte)(val >> 16);
         data[loffset+2] = (byte)(val >> 8);
         data[loffset+3] = (byte)val;
     }

     /**
         * Put the value of the named double field into the persistent field.
         */
     public void put(String name, double value) {
         long val = Double.doubleToLongBits(value);
         ObjectStreamField field = desc.getField(name);
         if (field == null || field.getType() != Double.TYPE)
         throw new IllegalArgumentException("No such double field");

         int loffset = field.getOffset();
         data[loffset] = (byte)(val >> 56);
         data[loffset+1] = (byte)(val >> 48);
         data[loffset+2] = (byte)(val >> 40);
         data[loffset+3] = (byte)(val >> 32);
         data[loffset+4] = (byte)(val >> 24);
         data[loffset+5] = (byte)(val >> 16);
         data[loffset+6] = (byte)(val >> 8);
         data[loffset+7] = (byte)val;
     }

     /**
      * Put the value of the named Object field into the persistent field.
      */
     public void put(String name, Object value) {
         ObjectStreamField field = desc.getField(name);
         if (field == null || field.isPrimitive())
         throw new IllegalArgumentException("No such object field");
         objects[field.getOffset()] = value;
     }

     /**
      * Write the data and fields to the specified stream.
      */
     public void write(ObjectOutput out) throws IOException {
         if (data != null)
         out.write(data, 0, data.length);

         if (objects != null) {
         for (int i = 0; i < objects.length; i++)
             out.writeObject(objects[i]);
         }
     }

     /**
      * Create a PutField object for the a Class.
      * Allocate the arrays for primitives and objects.
      */
     PutFieldImpl(ObjectStreamClass descriptor) {
         desc = descriptor;
         if (desc.primBytes > 0)
         data = new byte[desc.primBytes];
         if (desc.objFields > 0)
         objects = new Object[desc.objFields];
     }

    /*
     * The byte array that contains the bytes for the primitive fields.
     * The Object array that contains the objects for the object fields.
     */
     private byte[] data;
     private Object[] objects;
     private ObjectStreamClass desc;
     };

    /*************************************************************/

    /* Remember the first exception that stopped this stream. */
    private IOException abortIOException = null;

    /* Object references are mapped to the wire handles through a hashtable
     * WireHandles are integers generated by the ObjectOutputStream,
     * they need only be unique within a stream.
     * Objects are assigned sequential handles and stored in wireHandle2Object.
     * The handle for an object is its index in wireHandle2Object.
     * Object with the "same" hashcode are chained using wireHash2Handle.
     * The hashcode of objects is used to index through the wireHash2Handle.
     * -1 is the marker for unused cells in wireNextHandle
     */
    private Object[] wireHandle2Object;
    private int[] wireNextHandle;
    private int[] wireHash2Handle;
    private int nextWireOffset;

    /* The object is the current object and ClassDescriptor is the current
     * subclass of the object being written. Nesting information is kept
     * on the stack.
     */
    private Object currentObject;
    private ObjectStreamClass currentClassDesc;
    private Stack classDescStack;
    private PutField currentPutFields;
    private Object[] writeObjectArglist = {this};

    /*
     * Flag set to true to allow replaceObject to be called.
     * Set by enableReplaceObject.
     * The array of replaceObjects and the index of the next insertion.
     */
    boolean enableReplace;
    private Object[] replaceObjects;
    private int nextReplaceOffset;

    /* Recursion level, starts at zero and is incremented for each entry
     * to writeObject.  Decremented before exit.
     */
    private int recursionDepth = 0;

    /* If true, use JDK 1.1 Externalizable data format. */
    boolean useDeprecatedExternalizableFormat = false;

    /* if true, override writeObject implementation with writeObjectOverride.
     */
    private final boolean enableSubclassImplementation;
}