/*
    * 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
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package java.io;
  
  import java.io.ObjectStreamClass.WeakClassKey;
  import java.lang.ref.ReferenceQueue;
  import java.lang.reflect.Array;
  import java.lang.reflect.Modifier;
  import java.lang.reflect.Proxy;
  import java.security.AccessControlContext;
  import java.security.AccessController;
  import java.security.PrivilegedAction;
  import java.security.PrivilegedActionException;
  import java.security.PrivilegedExceptionAction;
  import java.util.Arrays;
  import java.util.HashMap;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.concurrent.atomic.AtomicBoolean;
  import static java.io.ObjectStreamClass.processQueue;
  
  /**
   * An ObjectInputStream deserializes primitive data and objects previously
   * written using an ObjectOutputStream.
   *
   * <p>ObjectOutputStream and ObjectInputStream can provide an application with
   * persistent storage for graphs of objects when used with a FileOutputStream
   * and FileInputStream respectively.  ObjectInputStream is used to recover
   * those objects previously serialized. Other uses include passing objects
   * between hosts using a socket stream or for marshaling and unmarshaling
   * arguments and parameters in a remote communication system.
   *
   * <p>ObjectInputStream ensures that the types of all objects in the graph
   * created from the stream match the classes present in the Java Virtual
   * Machine.  Classes are loaded as required using the standard mechanisms.
   *
   * <p>Only objects that support the java.io.Serializable or
   * java.io.Externalizable interface can be read from streams.
   *
   * <p>The method <code>readObject</code> is used to read an object from the
   * stream.  Java's safe casting should be used to get the desired type.  In
   * Java, strings and arrays are objects and are treated as objects during
   * serialization. When read they need to be cast to the expected type.
   *
   * <p>Primitive data types can be read from the stream using the appropriate
   * method on DataInput.
   *
   * <p>The default deserialization mechanism for objects restores the contents
   * of each field to the value and type it had when it was written.  Fields
   * declared as transient or static are ignored by the deserialization process.
   * References to other objects cause those objects to be read from the stream
   * as necessary.  Graphs of objects are restored correctly using a reference
   * sharing mechanism.  New objects are always allocated when deserializing,
   * which prevents existing objects from being overwritten.
   *
   * <p>Reading an object is analogous to running the constructors of a new
   * object.  Memory is allocated for the object and initialized to zero (NULL).
   * No-arg constructors are invoked for the non-serializable classes and then
   * the fields of the serializable classes are restored from the stream starting
   * with the serializable class closest to java.lang.object and finishing with
   * the object's most specific class.
   *
   * <p>For example to read from a stream as written by the example in
   * ObjectOutputStream:
   * <br>
   * <pre>
   *      FileInputStream fis = new FileInputStream("t.tmp");
   *      ObjectInputStream ois = new ObjectInputStream(fis);
   *
   *      int i = ois.readInt();
   *      String today = (String) ois.readObject();
   *      Date date = (Date) ois.readObject();
   *
   *      ois.close();
   * </pre>
   *
  * <p>Classes control how they are serialized by implementing either the
  * java.io.Serializable or java.io.Externalizable interfaces.
  *
  * <p>Implementing the Serializable interface allows object serialization to
  * save and restore the entire state of the object and it allows classes to
  * evolve between the time the stream is written and the time it is read.  It
  * automatically traverses references between objects, saving and restoring
  * entire graphs.
  *
  * <p>Serializable classes that require special handling during the
  * serialization and deserialization process should implement the following
  * methods:<p>
  *
  * <pre>
  * private void writeObject(java.io.ObjectOutputStream stream)
  *     throws IOException;
  * private void readObject(java.io.ObjectInputStream stream)
  *     throws IOException, ClassNotFoundException;
  * private void readObjectNoData()
  *     throws ObjectStreamException;
  * </pre>
  *
  * <p>The readObject method is responsible for reading and restoring the state
  * of the object for its particular class using data written to the stream by
  * the corresponding writeObject method.  The method does not need to concern
  * itself with the state belonging to its superclasses or subclasses.  State is
  * restored by reading data from the ObjectInputStream for the individual
  * fields and making assignments to the appropriate fields of the object.
  * Reading primitive data types is supported by DataInput.
  *
  * <p>Any attempt to read object data which exceeds the boundaries of the
  * custom data written by the corresponding writeObject method will cause an
  * OptionalDataException to be thrown with an eof field value of true.
  * Non-object reads which exceed the end of the allotted data will reflect the
  * end of data in the same way that they would indicate the end of the stream:
  * bytewise reads will return -1 as the byte read or number of bytes read, and
  * primitive reads will throw EOFExceptions.  If there is no corresponding
  * writeObject method, then the end of default serialized data marks the end of
  * the allotted data.
  *
  * <p>Primitive and object read calls issued from within a readExternal method
  * behave in the same manner--if the stream is already positioned at the end of
  * data written by the corresponding writeExternal method, object reads will
  * throw OptionalDataExceptions with eof set to true, bytewise reads will
  * return -1, and primitive reads will throw EOFExceptions.  Note that this
  * behavior does not hold for streams written with the old
  * <code>ObjectStreamConstants.PROTOCOL_VERSION_1</code> protocol, in which the
  * end of data written by writeExternal methods is not demarcated, and hence
  * cannot be detected.
  *
  * <p>The readObjectNoData method is responsible for initializing the state of
  * the object for its particular class in the event that the serialization
  * stream does not list the given class as a superclass of the object being
  * deserialized.  This may occur in cases where the receiving party uses a
  * different version of the deserialized instance's class than the sending
  * party, and the receiver's version extends classes that are not extended by
  * the sender's version.  This may also occur if the serialization stream has
  * been tampered; hence, readObjectNoData is useful for initializing
  * deserialized objects properly despite a "hostile" or incomplete source
  * stream.
  *
  * <p>Serialization does not read or assign values to 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>Any exception that occurs while deserializing an object will be caught by
  * the ObjectInputStream and abort the reading 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 deserialized 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
  * deserialize an enum constant, ObjectInputStream reads the constant name from
  * the stream; the deserialized constant is then obtained by calling the static
  * method <code>Enum.valueOf(Class, String)</code> with the enum constant's
  * base type and the received constant name as arguments.  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 deserialized cannot be
  * customized: any class-specific readObject, readObjectNoData, and readResolve
  * methods defined by enum types are ignored during deserialization.
  * Similarly, any serialPersistentFields or serialVersionUID field declarations
  * are also ignored--all enum types have a fixed serialVersionUID of 0L.
  *
  * @author      Mike Warres
  * @author      Roger Riggs
  * @see java.io.DataInput
  * @see java.io.ObjectOutputStream
  * @see java.io.Serializable
  * @see <a href="../../../platform/serialization/spec/input.html"> Object Serialization Specification, Section 3, Object Input Classes</a>
  * @since   JDK1.1
  */
 public class ObjectInputStream
     extends InputStream implements ObjectInput, ObjectStreamConstants
 {
     /** handle value representing null */
     private static final int NULL_HANDLE = -1;
 
     /** marker for unshared objects in internal handle table */
     private static final Object unsharedMarker = new Object();
 
     /** table mapping primitive type names to corresponding class objects */
     private static final HashMap<String, Class<?>> primClasses
         = new HashMap<>(8, 1.0F);
     static {
         primClasses.put("boolean", boolean.class);
         primClasses.put("byte", byte.class);
         primClasses.put("char", char.class);
         primClasses.put("short", short.class);
         primClasses.put("int", int.class);
         primClasses.put("long", long.class);
         primClasses.put("float", float.class);
         primClasses.put("double", double.class);
         primClasses.put("void", void.class);
     }
 
     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 BlockDataInputStream bin;
     /** validation callback list */
     private final ValidationList vlist;
     /** recursion depth */
     private int depth;
     /** whether stream is closed */
     private boolean closed;
 
     /** wire handle -> obj/exception map */
     private final HandleTable handles;
     /** scratch field for passing handle values up/down call stack */
     private int passHandle = NULL_HANDLE;
     /** flag set when at end of field value block with no TC_ENDBLOCKDATA */
     private boolean defaultDataEnd = false;
 
     /** buffer for reading primitive field values */
     private byte[] primVals;
 
     /** if true, invoke readObjectOverride() instead of readObject() */
     private final boolean enableOverride;
     /** if true, invoke resolveObject() */
     private boolean enableResolve;
 
     /**
      * Context during upcalls to class-defined readObject methods; holds
      * object currently being deserialized and descriptor for current class.
      * Null when not during readObject upcall.
      */
     private SerialCallbackContext curContext;
 
     /**
      * Creates an ObjectInputStream that reads from the specified InputStream.
      * A serialization stream header is read from the stream and verified.
      * This constructor will block until the corresponding ObjectOutputStream
      * has written and flushed 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 ObjectInputStream.readFields or ObjectInputStream.readUnshared
      * methods.
      *
      * @param   in input stream to read from
      * @throws  StreamCorruptedException if the stream header is incorrect
      * @throws  IOException if an I/O error occurs while reading stream header
      * @throws  SecurityException if untrusted subclass illegally overrides
      *          security-sensitive methods
      * @throws  NullPointerException if <code>in</code> is <code>null</code>
      * @see     ObjectInputStream#ObjectInputStream()
      * @see     ObjectInputStream#readFields()
      * @see     ObjectOutputStream#ObjectOutputStream(OutputStream)
      */
     public ObjectInputStream(InputStream in) throws IOException {
         verifySubclass();
         bin = new BlockDataInputStream(in);
         handles = new HandleTable(10);
         vlist = new ValidationList();
         enableOverride = false;
         readStreamHeader();
         bin.setBlockDataMode(true);
     }
 
     /**
      * Provide a way for subclasses that are completely reimplementing
      * ObjectInputStream to not have to allocate private data just used by this
      * implementation of ObjectInputStream.
      *
      * <p>If there is a security manager installed, this method first calls the
      * security manager's <code>checkPermission</code> method with the
      * <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 ObjectInputStream() throws IOException, SecurityException {
         SecurityManager sm = System.getSecurityManager();
         if (sm != null) {
             sm.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
         }
         bin = null;
         handles = null;
         vlist = null;
         enableOverride = true;
     }
 
     /**
      * Read an object from the ObjectInputStream.  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 read.
      * Default deserializing for a class can be overriden using the writeObject
      * and readObject methods.  Objects referenced by this object are read
      * transitively so that a complete equivalent graph of objects is
      * reconstructed by readObject.
      *
      * <p>The root object is completely restored when all of its fields and the
      * objects it references are completely restored.  At this point the object
      * validation callbacks are executed in order based on their registered
      * priorities. The callbacks are registered by objects (in the readObject
      * special methods) as they are individually restored.
      *
      * <p>Exceptions are thrown for problems with the InputStream and for
      * classes that should not be deserialized.  All exceptions are fatal to
      * the InputStream and leave it in an indeterminate state; it is up to the
      * caller to ignore or recover the stream state.
      *
      * @throws  ClassNotFoundException Class of a serialized object cannot be
      *          found.
      * @throws  InvalidClassException Something is wrong with a class used by
      *          serialization.
      * @throws  StreamCorruptedException Control information in the
      *          stream is inconsistent.
      * @throws  OptionalDataException Primitive data was found in the
      *          stream instead of objects.
      * @throws  IOException Any of the usual Input/Output related exceptions.
      */
     public final Object readObject()
         throws IOException, ClassNotFoundException
     {
         if (enableOverride) {
             return readObjectOverride();
         }
 
         // if nested read, passHandle contains handle of enclosing object
         int outerHandle = passHandle;
         try {
             Object obj = readObject0(false);
             handles.markDependency(outerHandle, passHandle);
             ClassNotFoundException ex = handles.lookupException(passHandle);
             if (ex != null) {
                 throw ex;
             }
             if (depth == 0) {
                 vlist.doCallbacks();
             }
             return obj;
         } finally {
             passHandle = outerHandle;
             if (closed && depth == 0) {
                 clear();
             }
         }
     }
 
     /**
      * This method is called by trusted subclasses of ObjectOutputStream that
      * constructed ObjectOutputStream using the protected no-arg constructor.
      * The subclass is expected to provide an override method with the modifier
      * "final".
      *
      * @return  the Object read from the stream.
      * @throws  ClassNotFoundException Class definition of a serialized object
      *          cannot be found.
      * @throws  OptionalDataException Primitive data was found in the stream
      *          instead of objects.
      * @throws  IOException if I/O errors occurred while reading from the
      *          underlying stream
      * @see #ObjectInputStream()
      * @see #readObject()
      * @since 1.2
      */
     protected Object readObjectOverride()
         throws IOException, ClassNotFoundException
     {
         return null;
     }
 
     /**
      * Reads an "unshared" object from the ObjectInputStream.  This method is
      * identical to readObject, except that it prevents subsequent calls to
      * readObject and readUnshared from returning additional references to the
      * deserialized instance obtained via this call.  Specifically:
      * <ul>
      *   <li>If readUnshared is called to deserialize a back-reference (the
      *       stream representation of an object which has been written
      *       previously to the stream), an ObjectStreamException will be
      *       thrown.
      *
      *   <li>If readUnshared returns successfully, then any subsequent attempts
      *       to deserialize back-references to the stream handle deserialized
      *       by readUnshared will cause an ObjectStreamException to be thrown.
      * </ul>
      * Deserializing an object via readUnshared invalidates the stream handle
      * associated with the returned object.  Note that this in itself does not
      * always guarantee that the reference returned by readUnshared is unique;
      * the deserialized object may define a readResolve method which returns an
      * object visible to other parties, or readUnshared may return a Class
      * object or enum constant obtainable elsewhere in the stream or through
      * external means. If the deserialized object defines a readResolve method
      * and the invocation of that method returns an array, then readUnshared
      * returns a shallow clone of that array; this guarantees that the returned
      * array object is unique and cannot be obtained a second time from an
      * invocation of readObject or readUnshared on the ObjectInputStream,
      * even if the underlying data stream has been manipulated.
      *
      * <p>ObjectInputStream 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.
      *
      * @return  reference to deserialized object
      * @throws  ClassNotFoundException if class of an object to deserialize
      *          cannot be found
      * @throws  StreamCorruptedException if control information in the stream
      *          is inconsistent
      * @throws  ObjectStreamException if object to deserialize has already
      *          appeared in stream
      * @throws  OptionalDataException if primitive data is next in stream
      * @throws  IOException if an I/O error occurs during deserialization
      * @since   1.4
      */
     public Object readUnshared() throws IOException, ClassNotFoundException {
         // if nested read, passHandle contains handle of enclosing object
         int outerHandle = passHandle;
         try {
             Object obj = readObject0(true);
             handles.markDependency(outerHandle, passHandle);
             ClassNotFoundException ex = handles.lookupException(passHandle);
             if (ex != null) {
                 throw ex;
             }
             if (depth == 0) {
                 vlist.doCallbacks();
             }
             return obj;
         } finally {
             passHandle = outerHandle;
             if (closed && depth == 0) {
                 clear();
             }
         }
     }
 
     /**
      * Read the non-static and non-transient fields of the current class from
      * this stream.  This may only be called from the readObject method of the
      * class being deserialized. It will throw the NotActiveException if it is
      * called otherwise.
      *
      * @throws  ClassNotFoundException if the class of a serialized object
      *          could not be found.
      * @throws  IOException if an I/O error occurs.
      * @throws  NotActiveException if the stream is not currently reading
      *          objects.
      */
     public void defaultReadObject()
         throws IOException, ClassNotFoundException
     {
         if (curContext == null) {
             throw new NotActiveException("not in call to readObject");
         }
         Object curObj = curContext.getObj();
         ObjectStreamClass curDesc = curContext.getDesc();
         bin.setBlockDataMode(false);
         defaultReadFields(curObj, curDesc);
         bin.setBlockDataMode(true);
         if (!curDesc.hasWriteObjectData()) {
             /*
              * Fix for 4360508: since stream does not contain terminating
              * TC_ENDBLOCKDATA tag, set flag so that reading code elsewhere
              * knows to simulate end-of-custom-data behavior.
              */
             defaultDataEnd = true;
         }
         ClassNotFoundException ex = handles.lookupException(passHandle);
         if (ex != null) {
             throw ex;
         }
     }
 
     /**
      * Reads the persistent fields from the stream and makes them available by
      * name.
      *
      * @return  the <code>GetField</code> object representing the persistent
      *          fields of the object being deserialized
      * @throws  ClassNotFoundException if the class of a serialized object
      *          could not be found.
      * @throws  IOException if an I/O error occurs.
      * @throws  NotActiveException if the stream is not currently reading
      *          objects.
      * @since 1.2
      */
     public ObjectInputStream.GetField readFields()
         throws IOException, ClassNotFoundException
     {
         if (curContext == null) {
             throw new NotActiveException("not in call to readObject");
         }
         Object curObj = curContext.getObj();
         ObjectStreamClass curDesc = curContext.getDesc();
         bin.setBlockDataMode(false);
         GetFieldImpl getField = new GetFieldImpl(curDesc);
         getField.readFields();
         bin.setBlockDataMode(true);
         if (!curDesc.hasWriteObjectData()) {
             /*
              * Fix for 4360508: since stream does not contain terminating
              * TC_ENDBLOCKDATA tag, set flag so that reading code elsewhere
              * knows to simulate end-of-custom-data behavior.
              */
             defaultDataEnd = true;
         }
 
         return getField;
     }
 
     /**
      * Register an object to be validated before the graph is returned.  While
      * similar to resolveObject these validations are called after the entire
      * graph has been reconstituted.  Typically, a readObject method will
      * register the object with the stream so that when all of the objects are
      * restored a final set of validations can be performed.
      *
      * @param   obj the object to receive the validation callback.
      * @param   prio controls the order of callbacks;zero is a good default.
      *          Use higher numbers to be called back earlier, lower numbers for
      *          later callbacks. Within a priority, callbacks are processed in
      *          no particular order.
      * @throws  NotActiveException The stream is not currently reading objects
      *          so it is invalid to register a callback.
      * @throws  InvalidObjectException The validation object is null.
      */
     public void registerValidation(ObjectInputValidation obj, int prio)
         throws NotActiveException, InvalidObjectException
     {
         if (depth == 0) {
             throw new NotActiveException("stream inactive");
         }
         vlist.register(obj, prio);
     }
 
     /**
      * Load the local class equivalent of the specified stream class
      * description.  Subclasses may implement this method to allow classes to
      * be fetched from an alternate source.
      *
      * <p>The corresponding method in <code>ObjectOutputStream</code> is
      * <code>annotateClass</code>.  This method will be invoked only once for
      * each unique class in the stream.  This method can be implemented by
      * subclasses to use an alternate loading mechanism but must return a
      * <code>Class</code> object. Once returned, if the class is not an array
      * class, its serialVersionUID is compared to the serialVersionUID of the
      * serialized class, and if there is a mismatch, the deserialization fails
      * and an {@link InvalidClassException} is thrown.
      *
      * <p>The default implementation of this method in
      * <code>ObjectInputStream</code> returns the result of calling
      * <pre>
      *     Class.forName(desc.getName(), false, loader)
      * </pre>
      * where <code>loader</code> is determined as follows: if there is a
      * method on the current thread's stack whose declaring class was
      * defined by a user-defined class loader (and was not a generated to
      * implement reflective invocations), then <code>loader</code> is class
      * loader corresponding to the closest such method to the currently
      * executing frame; otherwise, <code>loader</code> is
      * <code>null</code>. If this call results in a
      * <code>ClassNotFoundException</code> and the name of the passed
      * <code>ObjectStreamClass</code> instance is the Java language keyword
      * for a primitive type or void, then the <code>Class</code> object
      * representing that primitive type or void will be returned
      * (e.g., an <code>ObjectStreamClass</code> with the name
      * <code>"int"</code> will be resolved to <code>Integer.TYPE</code>).
      * Otherwise, the <code>ClassNotFoundException</code> will be thrown to
      * the caller of this method.
      *
      * @param   desc an instance of class <code>ObjectStreamClass</code>
      * @return  a <code>Class</code> object corresponding to <code>desc</code>
      * @throws  IOException any of the usual Input/Output exceptions.
      * @throws  ClassNotFoundException if class of a serialized object cannot
      *          be found.
      */
     protected Class<?> resolveClass(ObjectStreamClass desc)
         throws IOException, ClassNotFoundException
     {
         String name = desc.getName();
         try {
             return Class.forName(name, false, latestUserDefinedLoader());
         } catch (ClassNotFoundException ex) {
             Class<?> cl = primClasses.get(name);
             if (cl != null) {
                 return cl;
             } else {
                 throw ex;
             }
         }
     }
 
     /**
      * Returns a proxy class that implements the interfaces named in a proxy
      * class descriptor; subclasses may implement this method to read custom
      * data from the stream along with the descriptors for dynamic proxy
      * classes, allowing them to use an alternate loading mechanism for the
      * interfaces and the proxy class.
      *
      * <p>This method is called exactly once for each unique proxy class
      * descriptor in the stream.
      *
      * <p>The corresponding method in <code>ObjectOutputStream</code> is
      * <code>annotateProxyClass</code>.  For a given subclass of
      * <code>ObjectInputStream</code> that overrides this method, the
      * <code>annotateProxyClass</code> method in the corresponding subclass of
      * <code>ObjectOutputStream</code> must write any data or objects read by
      * this method.
      *
      * <p>The default implementation of this method in
      * <code>ObjectInputStream</code> returns the result of calling
      * <code>Proxy.getProxyClass</code> with the list of <code>Class</code>
      * objects for the interfaces that are named in the <code>interfaces</code>
      * parameter.  The <code>Class</code> object for each interface name
      * <code>i</code> is the value returned by calling
      * <pre>
      *     Class.forName(i, false, loader)
      * </pre>
      * where <code>loader</code> is that of the first non-<code>null</code>
      * class loader up the execution stack, or <code>null</code> if no
      * non-<code>null</code> class loaders are on the stack (the same class
      * loader choice used by the <code>resolveClass</code> method).  Unless any
      * of the resolved interfaces are non-public, this same value of
      * <code>loader</code> is also the class loader passed to
      * <code>Proxy.getProxyClass</code>; if non-public interfaces are present,
      * their class loader is passed instead (if more than one non-public
      * interface class loader is encountered, an
      * <code>IllegalAccessError</code> is thrown).
      * If <code>Proxy.getProxyClass</code> throws an
      * <code>IllegalArgumentException</code>, <code>resolveProxyClass</code>
      * will throw a <code>ClassNotFoundException</code> containing the
      * <code>IllegalArgumentException</code>.
      *
      * @param interfaces the list of interface names that were
      *                deserialized in the proxy class descriptor
      * @return  a proxy class for the specified interfaces
      * @throws        IOException any exception thrown by the underlying
      *                <code>InputStream</code>
      * @throws        ClassNotFoundException if the proxy class or any of the
      *                named interfaces could not be found
      * @see ObjectOutputStream#annotateProxyClass(Class)
      * @since 1.3
      */
     protected Class<?> resolveProxyClass(String[] interfaces)
         throws IOException, ClassNotFoundException
     {
         ClassLoader latestLoader = latestUserDefinedLoader();
         ClassLoader nonPublicLoader = null;
         boolean hasNonPublicInterface = false;
 
         // define proxy in class loader of non-public interface(s), if any
         Class[] classObjs = new Class[interfaces.length];
         for (int i = 0; i < interfaces.length; i++) {
             Class cl = Class.forName(interfaces[i], false, latestLoader);
             if ((cl.getModifiers() & Modifier.PUBLIC) == 0) {
                 if (hasNonPublicInterface) {
                     if (nonPublicLoader != cl.getClassLoader()) {
                         throw new IllegalAccessError(
                             "conflicting non-public interface class loaders");
                     }
                 } else {
                     nonPublicLoader = cl.getClassLoader();
                     hasNonPublicInterface = true;
                 }
             }
             classObjs[i] = cl;
         }
         try {
             return Proxy.getProxyClass(
                 hasNonPublicInterface ? nonPublicLoader : latestLoader,
                 classObjs);
         } catch (IllegalArgumentException e) {
             throw new ClassNotFoundException(null, e);
         }
     }
 
     /**
      * This method will allow trusted subclasses of ObjectInputStream to
      * substitute one object for another during deserialization. Replacing
      * objects is disabled until enableResolveObject is called. The
      * enableResolveObject method checks that the stream requesting to resolve
      * object can be trusted. Every reference to serializable objects is passed
      * to resolveObject.  To insure that the private state of objects is not
      * unintentionally exposed only trusted streams may use resolveObject.
      *
      * <p>This method is called after an object has been read but before it is
      * returned from readObject.  The default resolveObject method just returns
      * the same object.
      *
      * <p>When a subclass is replacing objects it must insure 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.
      *
      * @param   obj object to be substituted
      * @return  the substituted object
      * @throws  IOException Any of the usual Input/Output exceptions.
      */
     protected Object resolveObject(Object obj) throws IOException {
         return obj;
     }
 
     /**
      * Enable the stream to allow objects read from the stream to be replaced.
      * When enabled, the resolveObject method is called for every object being
      * deserialized.
      *
      * <p>If <i>enable</i> is true, and there is a security manager installed,
      * this method first calls the security manager's
      * <code>checkPermission</code> method with the
      * <code>SerializablePermission("enableSubstitution")</code> permission to
      * ensure it's ok to enable the stream to allow objects read from the
      * stream to be replaced.
      *
      * @param   enable true for enabling use of <code>resolveObject</code> for
      *          every object being deserialized
      * @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 allow objects read from the stream to be replaced.
      * @see SecurityManager#checkPermission
      * @see java.io.SerializablePermission
      */
     protected boolean enableResolveObject(boolean enable)
         throws SecurityException
     {
         if (enable == enableResolve) {
             return enable;
         }
         if (enable) {
             SecurityManager sm = System.getSecurityManager();
             if (sm != null) {
                 sm.checkPermission(SUBSTITUTION_PERMISSION);
             }
         }
         enableResolve = enable;
         return !enableResolve;
     }
 
     /**
      * The readStreamHeader method is provided to allow subclasses to read and
      * verify their own stream headers. It reads and verifies the magic number
      * and version number.
      *
      * @throws  IOException if there are I/O errors while reading from the
      *          underlying <code>InputStream</code>
      * @throws  StreamCorruptedException if control information in the stream
      *          is inconsistent
      */
     protected void readStreamHeader()
         throws IOException, StreamCorruptedException
     {
         short s0 = bin.readShort();
         short s1 = bin.readShort();
         if (s0 != STREAM_MAGIC || s1 != STREAM_VERSION) {
             throw new StreamCorruptedException(
                 String.format("invalid stream header: %04X%04X", s0, s1));
         }
     }
 
     /**
      * Read a class descriptor from the serialization stream.  This method is
      * called when the ObjectInputStream expects a class descriptor as the next
      * item in the serialization stream.  Subclasses of ObjectInputStream may
      * override this method to read in class descriptors that have been written
      * in non-standard formats (by subclasses of ObjectOutputStream which have
      * overridden the <code>writeClassDescriptor</code> method).  By default,
      * this method reads class descriptors according to the format defined in
      * the Object Serialization specification.
      *
      * @return  the class descriptor read
      * @throws  IOException If an I/O error has occurred.
      * @throws  ClassNotFoundException If the Class of a serialized object used
      *          in the class descriptor representation cannot be found
      * @see java.io.ObjectOutputStream#writeClassDescriptor(java.io.ObjectStreamClass)
      * @since 1.3
      */
     protected ObjectStreamClass readClassDescriptor()
         throws IOException, ClassNotFoundException
     {
         ObjectStreamClass desc = new ObjectStreamClass();
         desc.readNonProxy(this);
         return desc;
     }
 
     /**
      * Reads a byte of data. This method will block if no input is available.
      *
      * @return  the byte read, or -1 if the end of the stream is reached.
      * @throws  IOException If an I/O error has occurred.
      */
     public int read() throws IOException {
         return bin.read();
     }
 
     /**
      * Reads into an array of bytes.  This method will block until some input
      * is available. Consider using java.io.DataInputStream.readFully to read
      * exactly 'length' bytes.
      *
      * @param   buf the buffer into which the data is read
      * @param   off the start offset of the data
      * @param   len the maximum number of bytes read
      * @return  the actual number of bytes read, -1 is returned when the end of
      *          the stream is reached.
      * @throws  IOException If an I/O error has occurred.
      * @see java.io.DataInputStream#readFully(byte[],int,int)
      */
     public int read(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();
         }
         return bin.read(buf, off, len, false);
     }
 
     /**
      * Returns the number of bytes that can be read without blocking.
      *
      * @return  the number of available bytes.
      * @throws  IOException if there are I/O errors while reading from the
      *          underlying <code>InputStream</code>
      */
     public int available() throws IOException {
         return bin.available();
     }
 
     /**
      * Closes the input stream. 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 {
         /*
          * Even if stream already closed, propagate redundant close to
          * underlying stream to stay consistent with previous implementations.
          */
         closed = true;
         if (depth == 0) {
             clear();
         }
         bin.close();
     }
 
     /**
      * Reads in a boolean.
      *
      * @return  the boolean read.
      * @throws  EOFException If end of file is reached.
      * @throws  IOException If other I/O error has occurred.
      */
     public boolean readBoolean() throws IOException {
         return bin.readBoolean();
     }
 
     /**
      * Reads an 8 bit byte.
      *
      * @return  the 8 bit byte read.
      * @throws  EOFException If end of file is reached.
      * @throws  IOException If other I/O error has occurred.
      */
     public byte readByte() throws IOException  {
         return bin.readByte();
     }
 
     /**
      * Reads an unsigned 8 bit byte.
      *
      * @return  the 8 bit byte read.
      * @throws  EOFException If end of file is reached.
      * @throws  IOException If other I/O error has occurred.
      */
     public int readUnsignedByte()  throws IOException {
         return bin.readUnsignedByte();
     }
 
     /**
      * Reads a 16 bit char.
      *
      * @return  the 16 bit char read.
      * @throws  EOFException If end of file is reached.
      * @throws  IOException If other I/O error has occurred.
      */
     public char readChar()  throws IOException {
         return bin.readChar();
     }
 
     /**
      * Reads a 16 bit short.
      *
      * @return  the 16 bit short read.
      * @throws  EOFException If end of file is reached.
      * @throws  IOException If other I/O error has occurred.
      */
     public short readShort()  throws IOException {
         return bin.readShort();
     }
 
     /**
      * Reads an unsigned 16 bit short.
      *
      * @return  the 16 bit short read.
      * @throws  EOFException If end of file is reached.
      * @throws  IOException If other I/O error has occurred.
      */
     public int readUnsignedShort() throws IOException {
         return bin.readUnsignedShort();
     }
 
     /**
      * Reads a 32 bit int.
      *
      * @return  the 32 bit integer read.
      * @throws  EOFException If end of file is reached.
      * @throws  IOException If other I/O error has occurred.
      */
     public int readInt()  throws IOException {
         return bin.readInt();
     }
 
     /**
      * Reads a 64 bit long.
      *
      * @return  the read 64 bit long.
      * @throws  EOFException If end of file is reached.
      * @throws  IOException If other I/O error has occurred.
      */
     public long readLong()  throws IOException {
         return bin.readLong();
     }
 
     /**
      * Reads a 32 bit float.
      *
      * @return  the 32 bit float read.
      * @throws  EOFException If end of file is reached.
      * @throws  IOException If other I/O error has occurred.
      */
     public float readFloat() throws IOException {
         return bin.readFloat();
     }
 
     /**
      * Reads a 64 bit double.
      *
      * @return  the 64 bit double read.
      * @throws  EOFException If end of file is reached.
      * @throws  IOException If other I/O error has occurred.
      */
     public double readDouble() throws IOException {
         return bin.readDouble();
     }
 
     /**
      * Reads bytes, blocking until all bytes are read.
      *
      * @param   buf the buffer into which the data is read
      * @throws  EOFException If end of file is reached.
      * @throws  IOException If other I/O error has occurred.
      */
     public void readFully(byte[] buf) throws IOException {
         bin.readFully(buf, 0, buf.length, false);
     }
 
     /**
      * Reads bytes, blocking until all bytes are read.
      *
      * @param   buf the buffer into which the data is read
      * @param   off the start offset of the data
      * @param   len the maximum number of bytes to read
      * @throws  EOFException If end of file is reached.
      * @throws  IOException If other I/O error has occurred.
      */
     public void readFully(byte[] buf, int off, int len) throws IOException {
         int endoff = off + len;
         if (off < 0 || len < 0 || endoff > buf.length || endoff < 0) {
             throw new IndexOutOfBoundsException();
         }
         bin.readFully(buf, off, len, false);
     }
 
     /**
      * Skips bytes.
      *
      * @param   len the number of bytes to be skipped
      * @return  the actual number of bytes skipped.
      * @throws  IOException If an I/O error has occurred.
      */
     public int skipBytes(int len) throws IOException {
         return bin.skipBytes(len);
     }
 
     /**
      * Reads in a line that has been terminated by a \n, \r, \r\n or EOF.
      *
      * @return  a String copy of the line.
      * @throws  IOException if there are I/O errors while reading from the
      *          underlying <code>InputStream</code>
      * @deprecated This method does not properly convert bytes to characters.
      *          see DataInputStream for the details and alternatives.
      */
     @Deprecated
     public String readLine() throws IOException {
         return bin.readLine();
     }
 
     /**
      * Reads a String in
      * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
      * format.
      *
      * @return  the String.
      * @throws  IOException if there are I/O errors while reading from the
      *          underlying <code>InputStream</code>
      * @throws  UTFDataFormatException if read bytes do not represent a valid
      *          modified UTF-8 encoding of a string
      */
     public String readUTF() throws IOException {
         return bin.readUTF();
     }
 
     /**
      * Provide access to the persistent fields read from the input stream.
      */
     public static abstract class GetField {
 
         /**
          * Get the ObjectStreamClass that describes the fields in the stream.
          *
          * @return  the descriptor class that describes the serializable fields
          */
         public abstract ObjectStreamClass getObjectStreamClass();
 
         /**
          * Return true if the named field is defaulted and has no value in this
          * stream.
          *
          * @param  name the name of the field
          * @return true, if and only if the named field is defaulted
          * @throws IOException if there are I/O errors while reading from
          *         the underlying <code>InputStream</code>
          * @throws IllegalArgumentException if <code>name</code> does not
          *         correspond to a serializable field
          */
         public abstract boolean defaulted(String name) throws IOException;
 
         /**
          * Get the value of the named boolean field from the persistent field.
          *
          * @param  name the name of the field
          * @param  val the default value to use if <code>name</code> does not
          *         have a value
          * @return the value of the named <code>boolean</code> field
          * @throws IOException if there are I/O errors while reading from the
          *         underlying <code>InputStream</code>
          * @throws IllegalArgumentException if type of <code>name</code> is
          *         not serializable or if the field type is incorrect
          */
         public abstract boolean get(String name, boolean val)
             throws IOException;
 
         /**
          * Get the value of the named byte field from the persistent field.
          *
          * @param  name the name of the field
          * @param  val the default value to use if <code>name</code> does not
          *         have a value
          * @return the value of the named <code>byte</code> field
          * @throws IOException if there are I/O errors while reading from the
          *         underlying <code>InputStream</code>
          * @throws IllegalArgumentException if type of <code>name</code> is
          *         not serializable or if the field type is incorrect
          */
         public abstract byte get(String name, byte val) throws IOException;
 
         /**
          * Get the value of the named char field from the persistent field.
          *
          * @param  name the name of the field
          * @param  val the default value to use if <code>name</code> does not
          *         have a value
          * @return the value of the named <code>char</code> field
          * @throws IOException if there are I/O errors while reading from the
          *         underlying <code>InputStream</code>
          * @throws IllegalArgumentException if type of <code>name</code> is
          *         not serializable or if the field type is incorrect
          */
         public abstract char get(String name, char val) throws IOException;
 
         /**
          * Get the value of the named short field from the persistent field.
          *
          * @param  name the name of the field
          * @param  val the default value to use if <code>name</code> does not
          *         have a value
          * @return the value of the named <code>short</code> field
          * @throws IOException if there are I/O errors while reading from the
          *         underlying <code>InputStream</code>
          * @throws IllegalArgumentException if type of <code>name</code> is
          *         not serializable or if the field type is incorrect
          */
         public abstract short get(String name, short val) throws IOException;
 
         /**
          * Get the value of the named int field from the persistent field.
          *
          * @param  name the name of the field
          * @param  val the default value to use if <code>name</code> does not
          *         have a value
          * @return the value of the named <code>int</code> field
          * @throws IOException if there are I/O errors while reading from the
          *         underlying <code>InputStream</code>
          * @throws IllegalArgumentException if type of <code>name</code> is
          *         not serializable or if the field type is incorrect
          */
         public abstract int get(String name, int val) throws IOException;
 
         /**
          * Get the value of the named long field from the persistent field.
          *
          * @param  name the name of the field
          * @param  val the default value to use if <code>name</code> does not
          *         have a value
          * @return the value of the named <code>long</code> field
          * @throws IOException if there are I/O errors while reading from the
          *         underlying <code>InputStream</code>
          * @throws IllegalArgumentException if type of <code>name</code> is
          *         not serializable or if the field type is incorrect
          */
         public abstract long get(String name, long val) throws IOException;
 
         /**
          * Get the value of the named float field from the persistent field.
          *
          * @param  name the name of the field
          * @param  val the default value to use if <code>name</code> does not
          *         have a value
          * @return the value of the named <code>float</code> field
          * @throws IOException if there are I/O errors while reading from the
          *         underlying <code>InputStream</code>
          * @throws IllegalArgumentException if type of <code>name</code> is
          *         not serializable or if the field type is incorrect
          */
         public abstract float get(String name, float val) throws IOException;
 
         /**
          * Get the value of the named double field from the persistent field.
          *
          * @param  name the name of the field
          * @param  val the default value to use if <code>name</code> does not
          *         have a value
          * @return the value of the named <code>double</code> field
          * @throws IOException if there are I/O errors while reading from the
          *         underlying <code>InputStream</code>
          * @throws IllegalArgumentException if type of <code>name</code> is
          *         not serializable or if the field type is incorrect
          */
         public abstract double get(String name, double val) throws IOException;
 
         /**
          * Get the value of the named Object field from the persistent field.
          *
          * @param  name the name of the field
          * @param  val the default value to use if <code>name</code> does not
          *         have a value
          * @return the value of the named <code>Object</code> field
          * @throws IOException if there are I/O errors while reading from the
          *         underlying <code>InputStream</code>
          * @throws IllegalArgumentException if type of <code>name</code> is
          *         not serializable or if the field type is incorrect
          */
         public abstract Object get(String name, Object val) throws IOException;
     }
 
     /**
      * 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 == ObjectInputStream.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 != ObjectInputStream.class;
                          cl = cl.getSuperclass())
                     {
                         try {
                             cl.getDeclaredMethod(
                                 "readUnshared", (Class[]) null);
                             return Boolean.FALSE;
                         } catch (NoSuchMethodException ex) {
                         }
                         try {
                             cl.getDeclaredMethod("readFields", (Class[]) null);
                             return Boolean.FALSE;
                         } catch (NoSuchMethodException ex) {
                         }
                     }
                     return Boolean.TRUE;
                 }
             }
         );
         return result.booleanValue();
     }
 
     /**
      * Clears internal data structures.
      */
     private void clear() {
         handles.clear();
         vlist.clear();
     }
 
     /**
      * Underlying readObject implementation.
      */
     private Object readObject0(boolean unshared) throws IOException {
         boolean oldMode = bin.getBlockDataMode();
         if (oldMode) {
             int remain = bin.currentBlockRemaining();
             if (remain > 0) {
                 throw new OptionalDataException(remain);
             } else if (defaultDataEnd) {
                 /*
                  * Fix for 4360508: stream is currently at the end of a field
                  * value block written via default serialization; since there
                  * is no terminating TC_ENDBLOCKDATA tag, simulate
                  * end-of-custom-data behavior explicitly.
                  */
                 throw new OptionalDataException(true);
             }
             bin.setBlockDataMode(false);
         }
 
         byte tc;
         while ((tc = bin.peekByte()) == TC_RESET) {
             bin.readByte();
             handleReset();
         }
 
         depth++;
         try {
             switch (tc) {
                 case TC_NULL:
                     return readNull();
 
                 case TC_REFERENCE:
                     return readHandle(unshared);
 
                 case TC_CLASS:
                     return readClass(unshared);
 
                 case TC_CLASSDESC:
                 case TC_PROXYCLASSDESC:
                     return readClassDesc(unshared);
 
                 case TC_STRING:
                 case TC_LONGSTRING:
                     return checkResolve(readString(unshared));
 
                 case TC_ARRAY:
                     return checkResolve(readArray(unshared));
 
                 case TC_ENUM:
                     return checkResolve(readEnum(unshared));
 
                 case TC_OBJECT:
                     return checkResolve(readOrdinaryObject(unshared));
 
                 case TC_EXCEPTION:
                     IOException ex = readFatalException();
                     throw new WriteAbortedException("writing aborted", ex);
 
                 case TC_BLOCKDATA:
                 case TC_BLOCKDATALONG:
                     if (oldMode) {
                         bin.setBlockDataMode(true);
                         bin.peek();             // force header read
                         throw new OptionalDataException(
                             bin.currentBlockRemaining());
                     } else {
                         throw new StreamCorruptedException(
                             "unexpected block data");
                     }
 
                 case TC_ENDBLOCKDATA:
                     if (oldMode) {
                         throw new OptionalDataException(true);
                     } else {
                         throw new StreamCorruptedException(
                             "unexpected end of block data");
                     }
 
                 default:
                     throw new StreamCorruptedException(
                         String.format("invalid type code: %02X", tc));
             }
         } finally {
             depth--;
             bin.setBlockDataMode(oldMode);
         }
     }
 
     /**
      * If resolveObject has been enabled and given object does not have an
      * exception associated with it, calls resolveObject to determine
      * replacement for object, and updates handle table accordingly.  Returns
      * replacement object, or echoes provided object if no replacement
      * occurred.  Expects that passHandle is set to given object's handle prior
      * to calling this method.
      */
     private Object checkResolve(Object obj) throws IOException {
         if (!enableResolve || handles.lookupException(passHandle) != null) {
             return obj;
         }
         Object rep = resolveObject(obj);
         if (rep != obj) {
             handles.setObject(passHandle, rep);
         }
         return rep;
     }
 
     /**
      * Reads string without allowing it to be replaced in stream.  Called from
      * within ObjectStreamClass.read().
      */
     String readTypeString() throws IOException {
         int oldHandle = passHandle;
         try {
             byte tc = bin.peekByte();
             switch (tc) {
                 case TC_NULL:
                     return (String) readNull();
 
                 case TC_REFERENCE:
                     return (String) readHandle(false);
 
                 case TC_STRING:
                 case TC_LONGSTRING:
                     return readString(false);
 
                 default:
                     throw new StreamCorruptedException(
                         String.format("invalid type code: %02X", tc));
             }
         } finally {
             passHandle = oldHandle;
         }
     }
 
     /**
      * Reads in null code, sets passHandle to NULL_HANDLE and returns null.
      */
     private Object readNull() throws IOException {
         if (bin.readByte() != TC_NULL) {
             throw new InternalError();
         }
         passHandle = NULL_HANDLE;
         return null;
     }
 
     /**
      * Reads in object handle, sets passHandle to the read handle, and returns
      * object associated with the handle.
      */
     private Object readHandle(boolean unshared) throws IOException {
         if (bin.readByte() != TC_REFERENCE) {
             throw new InternalError();
         }
         passHandle = bin.readInt() - baseWireHandle;
         if (passHandle < 0 || passHandle >= handles.size()) {
             throw new StreamCorruptedException(
                 String.format("invalid handle value: %08X", passHandle +
                 baseWireHandle));
         }
         if (unshared) {
             // REMIND: what type of exception to throw here?
             throw new InvalidObjectException(
                 "cannot read back reference as unshared");
         }
 
         Object obj = handles.lookupObject(passHandle);
         if (obj == unsharedMarker) {
             // REMIND: what type of exception to throw here?
             throw new InvalidObjectException(
                 "cannot read back reference to unshared object");
         }
         return obj;
     }
 
     /**
      * Reads in and returns class object.  Sets passHandle to class object's
      * assigned handle.  Returns null if class is unresolvable (in which case a
      * ClassNotFoundException will be associated with the class' handle in the
      * handle table).
      */
     private Class readClass(boolean unshared) throws IOException {
         if (bin.readByte() != TC_CLASS) {
             throw new InternalError();
         }
         ObjectStreamClass desc = readClassDesc(false);
         Class cl = desc.forClass();
         passHandle = handles.assign(unshared ? unsharedMarker : cl);
 
         ClassNotFoundException resolveEx = desc.getResolveException();
         if (resolveEx != null) {
             handles.markException(passHandle, resolveEx);
         }
 
         handles.finish(passHandle);
         return cl;
     }
 
     /**
      * Reads in and returns (possibly null) class descriptor.  Sets passHandle
      * to class descriptor's assigned handle.  If class descriptor cannot be
      * resolved to a class in the local VM, a ClassNotFoundException is
      * associated with the class descriptor's handle.
      */
     private ObjectStreamClass readClassDesc(boolean unshared)
         throws IOException
     {
         byte tc = bin.peekByte();
         switch (tc) {
             case TC_NULL:
                 return (ObjectStreamClass) readNull();
 
             case TC_REFERENCE:
                 return (ObjectStreamClass) readHandle(unshared);
 
             case TC_PROXYCLASSDESC:
                 return readProxyDesc(unshared);
 
             case TC_CLASSDESC:
                 return readNonProxyDesc(unshared);
 
             default:
                 throw new StreamCorruptedException(
                     String.format("invalid type code: %02X", tc));
         }
     }
 
     /**
      * Reads in and returns class descriptor for a dynamic proxy class.  Sets
      * passHandle to proxy class descriptor's assigned handle.  If proxy class
      * descriptor cannot be resolved to a class in the local VM, a
      * ClassNotFoundException is associated with the descriptor's handle.
      */
     private ObjectStreamClass readProxyDesc(boolean unshared)
         throws IOException
     {
         if (bin.readByte() != TC_PROXYCLASSDESC) {
             throw new InternalError();
         }
 
         ObjectStreamClass desc = new ObjectStreamClass();
         int descHandle = handles.assign(unshared ? unsharedMarker : desc);
         passHandle = NULL_HANDLE;
 
         int numIfaces = bin.readInt();
         String[] ifaces = new String[numIfaces];
         for (int i = 0; i < numIfaces; i++) {
             ifaces[i] = bin.readUTF();
         }
 
         Class cl = null;
         ClassNotFoundException resolveEx = null;
         bin.setBlockDataMode(true);
         try {
             if ((cl = resolveProxyClass(ifaces)) == null) {
                 resolveEx = new ClassNotFoundException("null class");
             }
         } catch (ClassNotFoundException ex) {
             resolveEx = ex;
         }
         skipCustomData();
 
         desc.initProxy(cl, resolveEx, readClassDesc(false));
 
         handles.finish(descHandle);
         passHandle = descHandle;
         return desc;
     }
 
     /**
      * Reads in and returns class descriptor for a class that is not a dynamic
      * proxy class.  Sets passHandle to class descriptor's assigned handle.  If
      * class descriptor cannot be resolved to a class in the local VM, a
      * ClassNotFoundException is associated with the descriptor's handle.
      */
     private ObjectStreamClass readNonProxyDesc(boolean unshared)
         throws IOException
     {
         if (bin.readByte() != TC_CLASSDESC) {
             throw new InternalError();
         }
 
         ObjectStreamClass desc = new ObjectStreamClass();
         int descHandle = handles.assign(unshared ? unsharedMarker : desc);
         passHandle = NULL_HANDLE;
 
         ObjectStreamClass readDesc = null;
         try {
             readDesc = readClassDescriptor();
         } catch (ClassNotFoundException ex) {
             throw (IOException) new InvalidClassException(
                 "failed to read class descriptor").initCause(ex);
         }
 
         Class cl = null;
         ClassNotFoundException resolveEx = null;
         bin.setBlockDataMode(true);
         try {
             if ((cl = resolveClass(readDesc)) == null) {
                 resolveEx = new ClassNotFoundException("null class");
             }
         } catch (ClassNotFoundException ex) {
             resolveEx = ex;
         }
         skipCustomData();
 
         desc.initNonProxy(readDesc, cl, resolveEx, readClassDesc(false));
 
         handles.finish(descHandle);
         passHandle = descHandle;
         return desc;
     }
 
     /**
      * Reads in and returns new string.  Sets passHandle to new string's
      * assigned handle.
      */
     private String readString(boolean unshared) throws IOException {
         String str;
         byte tc = bin.readByte();
         switch (tc) {
             case TC_STRING:
                 str = bin.readUTF();
                 break;
 
             case TC_LONGSTRING:
                 str = bin.readLongUTF();
                 break;
 
             default:
                 throw new StreamCorruptedException(
                     String.format("invalid type code: %02X", tc));
         }
         passHandle = handles.assign(unshared ? unsharedMarker : str);
         handles.finish(passHandle);
         return str;
     }
 
     /**
      * Reads in and returns array object, or null if array class is
      * unresolvable.  Sets passHandle to array's assigned handle.
      */
     private Object readArray(boolean unshared) throws IOException {
         if (bin.readByte() != TC_ARRAY) {
             throw new InternalError();
         }
 
         ObjectStreamClass desc = readClassDesc(false);
         int len = bin.readInt();
 
         Object array = null;
         Class cl, ccl = null;
         if ((cl = desc.forClass()) != null) {
             ccl = cl.getComponentType();
             array = Array.newInstance(ccl, len);
         }
 
         int arrayHandle = handles.assign(unshared ? unsharedMarker : array);
         ClassNotFoundException resolveEx = desc.getResolveException();
         if (resolveEx != null) {
             handles.markException(arrayHandle, resolveEx);
         }
 
         if (ccl == null) {
             for (int i = 0; i < len; i++) {
                 readObject0(false);
             }
         } else if (ccl.isPrimitive()) {
             if (ccl == Integer.TYPE) {
                 bin.readInts((int[]) array, 0, len);
             } else if (ccl == Byte.TYPE) {
                 bin.readFully((byte[]) array, 0, len, true);
             } else if (ccl == Long.TYPE) {
                 bin.readLongs((long[]) array, 0, len);
             } else if (ccl == Float.TYPE) {
                 bin.readFloats((float[]) array, 0, len);
             } else if (ccl == Double.TYPE) {
                 bin.readDoubles((double[]) array, 0, len);
             } else if (ccl == Short.TYPE) {
                 bin.readShorts((short[]) array, 0, len);
             } else if (ccl == Character.TYPE) {
                 bin.readChars((char[]) array, 0, len);
             } else if (ccl == Boolean.TYPE) {
                 bin.readBooleans((boolean[]) array, 0, len);
             } else {
                 throw new InternalError();
             }
         } else {
             Object[] oa = (Object[]) array;
             for (int i = 0; i < len; i++) {
                 oa[i] = readObject0(false);
                 handles.markDependency(arrayHandle, passHandle);
             }
         }
 
         handles.finish(arrayHandle);
         passHandle = arrayHandle;
         return array;
     }
 
     /**
      * Reads in and returns enum constant, or null if enum type is
      * unresolvable.  Sets passHandle to enum constant's assigned handle.
      */
     private Enum readEnum(boolean unshared) throws IOException {
         if (bin.readByte() != TC_ENUM) {
             throw new InternalError();
         }
 
         ObjectStreamClass desc = readClassDesc(false);
         if (!desc.isEnum()) {
             throw new InvalidClassException("non-enum class: " + desc);
         }
 
         int enumHandle = handles.assign(unshared ? unsharedMarker : null);
         ClassNotFoundException resolveEx = desc.getResolveException();
         if (resolveEx != null) {
             handles.markException(enumHandle, resolveEx);
         }
 
         String name = readString(false);
         Enum en = null;
         Class cl = desc.forClass();
         if (cl != null) {
             try {
                 en = Enum.valueOf(cl, name);
             } catch (IllegalArgumentException ex) {
                 throw (IOException) new InvalidObjectException(
                     "enum constant " + name + " does not exist in " +
                     cl).initCause(ex);
             }
             if (!unshared) {
                 handles.setObject(enumHandle, en);
             }
         }
 
         handles.finish(enumHandle);
         passHandle = enumHandle;
         return en;
     }
 
     /**
      * Reads and returns "ordinary" (i.e., not a String, Class,
      * ObjectStreamClass, array, or enum constant) object, or null if object's
      * class is unresolvable (in which case a ClassNotFoundException will be
      * associated with object's handle).  Sets passHandle to object's assigned
      * handle.
      */
     private Object readOrdinaryObject(boolean unshared)
         throws IOException
     {
         if (bin.readByte() != TC_OBJECT) {
             throw new InternalError();
         }
 
         ObjectStreamClass desc = readClassDesc(false);
         desc.checkDeserialize();
 
         Object obj;
         try {
             obj = desc.isInstantiable() ? desc.newInstance() : null;
         } catch (Exception ex) {
             throw (IOException) new InvalidClassException(
                 desc.forClass().getName(),
                 "unable to create instance").initCause(ex);
         }
 
         passHandle = handles.assign(unshared ? unsharedMarker : obj);
         ClassNotFoundException resolveEx = desc.getResolveException();
         if (resolveEx != null) {
             handles.markException(passHandle, resolveEx);
         }
 
         if (desc.isExternalizable()) {
             readExternalData((Externalizable) obj, desc);
         } else {
             readSerialData(obj, desc);
         }
 
         handles.finish(passHandle);
 
         if (obj != null &&
             handles.lookupException(passHandle) == null &&
             desc.hasReadResolveMethod())
         {
             Object rep = desc.invokeReadResolve(obj);
             if (unshared && rep.getClass().isArray()) {
                 rep = cloneArray(rep);
             }
             if (rep != obj) {
                 handles.setObject(passHandle, obj = rep);
             }
         }
 
         return obj;
     }
 
     /**
      * If obj is non-null, reads externalizable data by invoking readExternal()
      * method of obj; otherwise, attempts to skip over externalizable data.
      * Expects that passHandle is set to obj's handle before this method is
      * called.
      */
     private void readExternalData(Externalizable obj, ObjectStreamClass desc)
         throws IOException
     {
         SerialCallbackContext oldContext = curContext;
         curContext = null;
         try {
             boolean blocked = desc.hasBlockExternalData();
             if (blocked) {
                 bin.setBlockDataMode(true);
             }
             if (obj != null) {
                 try {
                     obj.readExternal(this);
                 } catch (ClassNotFoundException ex) {
                     /*
                      * In most cases, the handle table has already propagated
                      * a CNFException to passHandle at this point; this mark
                      * call is included to address cases where the readExternal
                      * method has cons'ed and thrown a new CNFException of its
                      * own.
                      */
                      handles.markException(passHandle, ex);
                 }
             }
             if (blocked) {
                 skipCustomData();
             }
         } finally {
             curContext = oldContext;
         }
         /*
          * At this point, if the externalizable data was not written in
          * block-data form and either the externalizable class doesn't exist
          * locally (i.e., obj == null) or readExternal() just threw a
          * CNFException, then the stream is probably in an inconsistent state,
          * since some (or all) of the externalizable data may not have been
          * consumed.  Since there's no "correct" action to take in this case,
          * we mimic the behavior of past serialization implementations and
          * blindly hope that the stream is in sync; if it isn't and additional
          * externalizable data remains in the stream, a subsequent read will
          * most likely throw a StreamCorruptedException.
          */
     }
 
     /**
      * Reads (or attempts to skip, if obj is null or is tagged with a
      * ClassNotFoundException) instance data for each serializable class of
      * object in stream, from superclass to subclass.  Expects that passHandle
      * is set to obj's handle before this method is called.
      */
     private void readSerialData(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 (slots[i].hasData) {
                 if (obj != null &&
                     slotDesc.hasReadObjectMethod() &&
                     handles.lookupException(passHandle) == null)
                 {
                     SerialCallbackContext oldContext = curContext;
 
                     try {
                         curContext = new SerialCallbackContext(obj, slotDesc);
 
                         bin.setBlockDataMode(true);
                         slotDesc.invokeReadObject(obj, this);
                     } catch (ClassNotFoundException ex) {
                         /*
                          * In most cases, the handle table has already
                          * propagated a CNFException to passHandle at this
                          * point; this mark call is included to address cases
                          * where the custom readObject method has cons'ed and
                          * thrown a new CNFException of its own.
                          */
                         handles.markException(passHandle, ex);
                     } finally {
                         curContext.setUsed();
                         curContext = oldContext;
                     }
 
                     /*
                      * defaultDataEnd may have been set indirectly by custom
                      * readObject() method when calling defaultReadObject() or
                      * readFields(); clear it to restore normal read behavior.
                      */
                     defaultDataEnd = false;
                 } else {
                     defaultReadFields(obj, slotDesc);
                 }
                 if (slotDesc.hasWriteObjectData()) {
                     skipCustomData();
                 } else {
                     bin.setBlockDataMode(false);
                 }
             } else {
                 if (obj != null &&
                     slotDesc.hasReadObjectNoDataMethod() &&
                     handles.lookupException(passHandle) == null)
                 {
                     slotDesc.invokeReadObjectNoData(obj);
                 }
             }
         }
     }
 
     /**
      * Skips over all block data and objects until TC_ENDBLOCKDATA is
      * encountered.
      */
     private void skipCustomData() throws IOException {
         int oldHandle = passHandle;
         for (;;) {
             if (bin.getBlockDataMode()) {
                 bin.skipBlockData();
                 bin.setBlockDataMode(false);
             }
             switch (bin.peekByte()) {
                 case TC_BLOCKDATA:
                 case TC_BLOCKDATALONG:
                     bin.setBlockDataMode(true);
                     break;
 
                 case TC_ENDBLOCKDATA:
                     bin.readByte();
                     passHandle = oldHandle;
                     return;
 
                 default:
                     readObject0(false);
                     break;
             }
         }
     }
 
     /**
      * Reads in values of serializable fields declared by given class
      * descriptor.  If obj is non-null, sets field values in obj.  Expects that
      * passHandle is set to obj's handle before this method is called.
      */
     private void defaultReadFields(Object obj, ObjectStreamClass desc)
         throws IOException
     {
         // REMIND: is isInstance check necessary?
         Class cl = desc.forClass();
         if (cl != null && obj != null && !cl.isInstance(obj)) {
             throw new ClassCastException();
         }
 
         int primDataSize = desc.getPrimDataSize();
         if (primVals == null || primVals.length < primDataSize) {
             primVals = new byte[primDataSize];
         }
         bin.readFully(primVals, 0, primDataSize, false);
         if (obj != null) {
             desc.setPrimFieldValues(obj, primVals);
         }
 
         int objHandle = passHandle;
         ObjectStreamField[] fields = desc.getFields(false);
         Object[] objVals = new Object[desc.getNumObjFields()];
         int numPrimFields = fields.length - objVals.length;
         for (int i = 0; i < objVals.length; i++) {
             ObjectStreamField f = fields[numPrimFields + i];
             objVals[i] = readObject0(f.isUnshared());
             if (f.getField() != null) {
                 handles.markDependency(objHandle, passHandle);
             }
         }
         if (obj != null) {
             desc.setObjFieldValues(obj, objVals);
         }
         passHandle = objHandle;
     }
 
     /**
      * Reads in and returns IOException that caused serialization to abort.
      * All stream state is discarded prior to reading in fatal exception.  Sets
      * passHandle to fatal exception's handle.
      */
     private IOException readFatalException() throws IOException {
         if (bin.readByte() != TC_EXCEPTION) {
             throw new InternalError();
         }
         clear();
         return (IOException) readObject0(false);
     }
 
     /**
      * If recursion depth is 0, clears internal data structures; otherwise,
      * throws a StreamCorruptedException.  This method is called when a
      * TC_RESET typecode is encountered.
      */
     private void handleReset() throws StreamCorruptedException {
         if (depth > 0) {
             throw new StreamCorruptedException(
                 "unexpected reset; recursion depth: " + depth);
         }
         clear();
     }
 
     /**
      * Converts specified span of bytes into float values.
      */
     // REMIND: remove once hotspot inlines Float.intBitsToFloat
     private static native void bytesToFloats(byte[] src, int srcpos,
                                              float[] dst, int dstpos,
                                              int nfloats);
 
     /**
      * Converts specified span of bytes into double values.
      */
     // REMIND: remove once hotspot inlines Double.longBitsToDouble
     private static native void bytesToDoubles(byte[] src, int srcpos,
                                               double[] dst, int dstpos,
                                               int ndoubles);
 
     /**
      * Returns the first non-null class loader (not counting class loaders of
      * generated reflection implementation classes) up the execution stack, or
      * null if only code from the null class loader is on the stack.  This
      * method is also called via reflection by the following RMI-IIOP class:
      *
      *     com.sun.corba.se.internal.util.JDKClassLoader
      *
      * This method should not be removed or its signature changed without
      * corresponding modifications to the above class.
      */
     // REMIND: change name to something more accurate?
     private static native ClassLoader latestUserDefinedLoader();
 
     /**
      * Default GetField implementation.
      */
     private class GetFieldImpl extends GetField {
 
         /** class descriptor describing serializable fields */
         private final ObjectStreamClass desc;
         /** primitive field values */
         private final byte[] primVals;
         /** object field values */
         private final Object[] objVals;
         /** object field value handles */
         private final int[] objHandles;
 
         /**
          * Creates GetFieldImpl object for reading fields defined in given
          * class descriptor.
          */
         GetFieldImpl(ObjectStreamClass desc) {
             this.desc = desc;
             primVals = new byte[desc.getPrimDataSize()];
             objVals = new Object[desc.getNumObjFields()];
             objHandles = new int[objVals.length];
         }
 
         public ObjectStreamClass getObjectStreamClass() {
             return desc;
         }
 
         public boolean defaulted(String name) throws IOException {
             return (getFieldOffset(name, null) < 0);
         }
 
         public boolean get(String name, boolean val) throws IOException {
             int off = getFieldOffset(name, Boolean.TYPE);
             return (off >= 0) ? Bits.getBoolean(primVals, off) : val;
         }
 
         public byte get(String name, byte val) throws IOException {
             int off = getFieldOffset(name, Byte.TYPE);
             return (off >= 0) ? primVals[off] : val;
         }
 
         public char get(String name, char val) throws IOException {
             int off = getFieldOffset(name, Character.TYPE);
             return (off >= 0) ? Bits.getChar(primVals, off) : val;
         }
 
         public short get(String name, short val) throws IOException {
             int off = getFieldOffset(name, Short.TYPE);
             return (off >= 0) ? Bits.getShort(primVals, off) : val;
         }
 
         public int get(String name, int val) throws IOException {
             int off = getFieldOffset(name, Integer.TYPE);
             return (off >= 0) ? Bits.getInt(primVals, off) : val;
         }
 
         public float get(String name, float val) throws IOException {
             int off = getFieldOffset(name, Float.TYPE);
             return (off >= 0) ? Bits.getFloat(primVals, off) : val;
         }
 
         public long get(String name, long val) throws IOException {
             int off = getFieldOffset(name, Long.TYPE);
             return (off >= 0) ? Bits.getLong(primVals, off) : val;
         }
 
         public double get(String name, double val) throws IOException {
             int off = getFieldOffset(name, Double.TYPE);
             return (off >= 0) ? Bits.getDouble(primVals, off) : val;
         }
 
         public Object get(String name, Object val) throws IOException {
             int off = getFieldOffset(name, Object.class);
             if (off >= 0) {
                 int objHandle = objHandles[off];
                 handles.markDependency(passHandle, objHandle);
                 return (handles.lookupException(objHandle) == null) ?
                     objVals[off] : null;
             } else {
                 return val;
             }
         }
 
         /**
          * Reads primitive and object field values from stream.
          */
         void readFields() throws IOException {
             bin.readFully(primVals, 0, primVals.length, false);
 
             int oldHandle = passHandle;
             ObjectStreamField[] fields = desc.getFields(false);
             int numPrimFields = fields.length - objVals.length;
             for (int i = 0; i < objVals.length; i++) {
                 objVals[i] =
                     readObject0(fields[numPrimFields + i].isUnshared());
                 objHandles[i] = passHandle;
             }
             passHandle = oldHandle;
         }
 
         /**
          * 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.
          * If no matching field is found in the (incoming) class
          * descriptor but a matching field is present in the associated local
          * class descriptor, returns -1.  Throws IllegalArgumentException if
          * neither incoming nor local class descriptor contains a match.
          */
         private int getFieldOffset(String name, Class type) {
             ObjectStreamField field = desc.getField(name, type);
             if (field != null) {
                 return field.getOffset();
             } else if (desc.getLocalDesc().getField(name, type) != null) {
                 return -1;
             } else {
                 throw new IllegalArgumentException("no such field " + name +
                                                    " with type " + type);
             }
         }
     }
 
     /**
      * Prioritized list of callbacks to be performed once object graph has been
      * completely deserialized.
      */
     private static class ValidationList {
 
         private static class Callback {
             final ObjectInputValidation obj;
             final int priority;
             Callback next;
             final AccessControlContext acc;
 
             Callback(ObjectInputValidation obj, int priority, Callback next,
                 AccessControlContext acc)
             {
                 this.obj = obj;
                 this.priority = priority;
                 this.next = next;
                 this.acc = acc;
             }
         }
 
         /** linked list of callbacks */
         private Callback list;
 
         /**
          * Creates new (empty) ValidationList.
          */
         ValidationList() {
         }
 
         /**
          * Registers callback.  Throws InvalidObjectException if callback
          * object is null.
          */
         void register(ObjectInputValidation obj, int priority)
             throws InvalidObjectException
         {
             if (obj == null) {
                 throw new InvalidObjectException("null callback");
             }
 
             Callback prev = null, cur = list;
             while (cur != null && priority < cur.priority) {
                 prev = cur;
                 cur = cur.next;
             }
             AccessControlContext acc = AccessController.getContext();
             if (prev != null) {
                 prev.next = new Callback(obj, priority, cur, acc);
             } else {
                 list = new Callback(obj, priority, list, acc);
             }
         }
 
         /**
          * Invokes all registered callbacks and clears the callback list.
          * Callbacks with higher priorities are called first; those with equal
          * priorities may be called in any order.  If any of the callbacks
          * throws an InvalidObjectException, the callback process is terminated
          * and the exception propagated upwards.
          */
         void doCallbacks() throws InvalidObjectException {
             try {
                 while (list != null) {
                     AccessController.doPrivileged(
                         new PrivilegedExceptionAction<Void>()
                     {
                         public Void run() throws InvalidObjectException {
                             list.obj.validateObject();
                             return null;
                         }
                     }, list.acc);
                     list = list.next;
                 }
             } catch (PrivilegedActionException ex) {
                 list = null;
                 throw (InvalidObjectException) ex.getException();
             }
         }
 
         /**
          * Resets the callback list to its initial (empty) state.
          */
         public void clear() {
             list = null;
         }
     }
 
     /**
      * Input stream supporting single-byte peek operations.
      */
     private static class PeekInputStream extends InputStream {
 
         /** underlying stream */
         private final InputStream in;
         /** peeked byte */
         private int peekb = -1;
 
         /**
          * Creates new PeekInputStream on top of given underlying stream.
          */
         PeekInputStream(InputStream in) {
             this.in = in;
         }
 
         /**
          * Peeks at next byte value in stream.  Similar to read(), except
          * that it does not consume the read value.
          */
         int peek() throws IOException {
             return (peekb >= 0) ? peekb : (peekb = in.read());
         }
 
         public int read() throws IOException {
             if (peekb >= 0) {
                 int v = peekb;
                 peekb = -1;
                 return v;
             } else {
                 return in.read();
             }
         }
 
         public int read(byte[] b, int off, int len) throws IOException {
             if (len == 0) {
                 return 0;
             } else if (peekb < 0) {
                 return in.read(b, off, len);
             } else {
                 b[off++] = (byte) peekb;
                 len--;
                 peekb = -1;
                 int n = in.read(b, off, len);
                 return (n >= 0) ? (n + 1) : 1;
             }
         }
 
         void readFully(byte[] b, int off, int len) throws IOException {
             int n = 0;
             while (n < len) {
                 int count = read(b, off + n, len - n);
                 if (count < 0) {
                     throw new EOFException();
                 }
                 n += count;
             }
         }
 
         public long skip(long n) throws IOException {
             if (n <= 0) {
                 return 0;
             }
             int skipped = 0;
             if (peekb >= 0) {
                 peekb = -1;
                 skipped++;
                 n--;
             }
             return skipped + skip(n);
         }
 
         public int available() throws IOException {
             return in.available() + ((peekb >= 0) ? 1 : 0);
         }
 
         public void close() throws IOException {
             in.close();
         }
     }
 
     /**
      * Input stream with two modes: in default mode, inputs data written in the
      * same format as DataOutputStream; in "block data" mode, inputs data
      * bracketed by block data markers (see object serialization specification
      * for details).  Buffering depends on block data mode: when in default
      * mode, no data is buffered in advance; when in block data mode, all data
      * for the current data block is read in at once (and buffered).
      */
     private class BlockDataInputStream
         extends InputStream implements DataInput
     {
         /** 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 reading strings) */
         private static final int CHAR_BUF_SIZE = 256;
         /** readBlockHeader() return value indicating header read may block */
         private static final int HEADER_BLOCKED = -2;
 
         /** buffer for reading general/block data */
         private final byte[] buf = new byte[MAX_BLOCK_SIZE];
         /** buffer for reading block data headers */
         private final byte[] hbuf = new byte[MAX_HEADER_SIZE];
         /** char buffer for fast string reads */
         private final char[] cbuf = new char[CHAR_BUF_SIZE];
 
         /** block data mode */
         private boolean blkmode = false;
 
         // block data state fields; values meaningful only when blkmode true
         /** current offset into buf */
         private int pos = 0;
         /** end offset of valid data in buf, or -1 if no more block data */
         private int end = -1;
         /** number of bytes in current block yet to be read from stream */
         private int unread = 0;
 
         /** underlying stream (wrapped in peekable filter stream) */
         private final PeekInputStream in;
         /** loopback stream (for data reads that span data blocks) */
         private final DataInputStream din;
 
         /**
          * Creates new BlockDataInputStream on top of given underlying stream.
          * Block data mode is turned off by default.
          */
         BlockDataInputStream(InputStream in) {
             this.in = new PeekInputStream(in);
             din = new DataInputStream(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.  Throws IllegalStateException if
          * block data mode is being switched from on to off while unconsumed
          * block data is still present in the stream.
          */
         boolean setBlockDataMode(boolean newmode) throws IOException {
             if (blkmode == newmode) {
                 return blkmode;
             }
             if (newmode) {
                 pos = 0;
                 end = 0;
                 unread = 0;
             } else if (pos < end) {
                 throw new IllegalStateException("unread block data");
             }
             blkmode = newmode;
             return !blkmode;
         }
 
         /**
          * Returns true if the stream is currently in block data mode, false
          * otherwise.
          */
         boolean getBlockDataMode() {
             return blkmode;
         }
 
         /**
          * If in block data mode, skips to the end of the current group of data
          * blocks (but does not unset block data mode).  If not in block data
          * mode, throws an IllegalStateException.
          */
         void skipBlockData() throws IOException {
             if (!blkmode) {
                 throw new IllegalStateException("not in block data mode");
             }
             while (end >= 0) {
                 refill();
             }
         }
 
         /**
          * Attempts to read in the next block data header (if any).  If
          * canBlock is false and a full header cannot be read without possibly
          * blocking, returns HEADER_BLOCKED, else if the next element in the
          * stream is a block data header, returns the block data length
          * specified by the header, else returns -1.
          */
         private int readBlockHeader(boolean canBlock) throws IOException {
             if (defaultDataEnd) {
                 /*
                  * Fix for 4360508: stream is currently at the end of a field
                  * value block written via default serialization; since there
                  * is no terminating TC_ENDBLOCKDATA tag, simulate
                  * end-of-custom-data behavior explicitly.
                  */
                 return -1;
             }
             try {
                 for (;;) {
                     int avail = canBlock ? Integer.MAX_VALUE : in.available();
                     if (avail == 0) {
                         return HEADER_BLOCKED;
                     }
 
                     int tc = in.peek();
                     switch (tc) {
                         case TC_BLOCKDATA:
                             if (avail < 2) {
                                 return HEADER_BLOCKED;
                             }
                             in.readFully(hbuf, 0, 2);
                             return hbuf[1] & 0xFF;
 
                         case TC_BLOCKDATALONG:
                             if (avail < 5) {
                                 return HEADER_BLOCKED;
                             }
                             in.readFully(hbuf, 0, 5);
                             int len = Bits.getInt(hbuf, 1);
                             if (len < 0) {
                                 throw new StreamCorruptedException(
                                     "illegal block data header length: " +
                                     len);
                             }
                             return len;
 
                         /*
                          * TC_RESETs may occur in between data blocks.
                          * Unfortunately, this case must be parsed at a lower
                          * level than other typecodes, since primitive data
                          * reads may span data blocks separated by a TC_RESET.
                          */
                         case TC_RESET:
                             in.read();
                             handleReset();
                             break;
 
                         default:
                             if (tc >= 0 && (tc < TC_BASE || tc > TC_MAX)) {
                                 throw new StreamCorruptedException(
                                     String.format("invalid type code: %02X",
                                     tc));
                             }
                             return -1;
                     }
                 }
             } catch (EOFException ex) {
                 throw new StreamCorruptedException(
                     "unexpected EOF while reading block data header");
             }
         }
 
         /**
          * Refills internal buffer buf with block data.  Any data in buf at the
          * time of the call is considered consumed.  Sets the pos, end, and
          * unread fields to reflect the new amount of available block data; if
          * the next element in the stream is not a data block, sets pos and
          * unread to 0 and end to -1.
          */
         private void refill() throws IOException {
             try {
                 do {
                     pos = 0;
                     if (unread > 0) {
                         int n =
                             in.read(buf, 0, Math.min(unread, MAX_BLOCK_SIZE));
                         if (n >= 0) {
                             end = n;
                             unread -= n;
                         } else {
                             throw new StreamCorruptedException(
                                 "unexpected EOF in middle of data block");
                         }
                     } else {
                         int n = readBlockHeader(true);
                         if (n >= 0) {
                             end = 0;
                             unread = n;
                         } else {
                             end = -1;
                             unread = 0;
                         }
                     }
                 } while (pos == end);
             } catch (IOException ex) {
                 pos = 0;
                 end = -1;
                 unread = 0;
                 throw ex;
             }
         }
 
         /**
          * If in block data mode, returns the number of unconsumed bytes
          * remaining in the current data block.  If not in block data mode,
          * throws an IllegalStateException.
          */
         int currentBlockRemaining() {
             if (blkmode) {
                 return (end >= 0) ? (end - pos) + unread : 0;
             } else {
                 throw new IllegalStateException();
             }
         }
 
         /**
          * Peeks at (but does not consume) and returns the next byte value in
          * the stream, or -1 if the end of the stream/block data (if in block
          * data mode) has been reached.
          */
         int peek() throws IOException {
             if (blkmode) {
                 if (pos == end) {
                     refill();
                 }
                 return (end >= 0) ? (buf[pos] & 0xFF) : -1;
             } else {
                 return in.peek();
             }
         }
 
         /**
          * Peeks at (but does not consume) and returns the next byte value in
          * the stream, or throws EOFException if end of stream/block data has
          * been reached.
          */
         byte peekByte() throws IOException {
             int val = peek();
             if (val < 0) {
                 throw new EOFException();
             }
             return (byte) val;
         }
 
 
         /* ----------------- generic input stream methods ------------------ */
         /*
          * The following methods are equivalent to their counterparts in
          * InputStream, except that they interpret data block boundaries and
          * read the requested data from within data blocks when in block data
          * mode.
          */
 
         public int read() throws IOException {
             if (blkmode) {
                 if (pos == end) {
                     refill();
                 }
                 return (end >= 0) ? (buf[pos++] & 0xFF) : -1;
             } else {
                 return in.read();
             }
         }
 
         public int read(byte[] b, int off, int len) throws IOException {
             return read(b, off, len, false);
         }
 
         public long skip(long len) throws IOException {
             long remain = len;
             while (remain > 0) {
                 if (blkmode) {
                     if (pos == end) {
                         refill();
                     }
                     if (end < 0) {
                         break;
                     }
                     int nread = (int) Math.min(remain, end - pos);
                     remain -= nread;
                     pos += nread;
                 } else {
                     int nread = (int) Math.min(remain, MAX_BLOCK_SIZE);
                     if ((nread = in.read(buf, 0, nread)) < 0) {
                         break;
                     }
                     remain -= nread;
                 }
             }
             return len - remain;
         }
 
         public int available() throws IOException {
             if (blkmode) {
                 if ((pos == end) && (unread == 0)) {
                     int n;
                     while ((n = readBlockHeader(false)) == 0) ;
                     switch (n) {
                         case HEADER_BLOCKED:
                             break;
 
                         case -1:
                             pos = 0;
                             end = -1;
                             break;
 
                         default:
                             pos = 0;
                             end = 0;
                             unread = n;
                             break;
                     }
                 }
                 // avoid unnecessary call to in.available() if possible
                 int unreadAvail = (unread > 0) ?
                     Math.min(in.available(), unread) : 0;
                 return (end >= 0) ? (end - pos) + unreadAvail : 0;
             } else {
                 return in.available();
             }
         }
 
         public void close() throws IOException {
             if (blkmode) {
                 pos = 0;
                 end = -1;
                 unread = 0;
             }
             in.close();
         }
 
         /**
          * Attempts to read len bytes into byte array b at offset off.  Returns
          * the number of bytes read, or -1 if the end of stream/block data has
          * been reached.  If copy is true, reads values into an intermediate
          * buffer before copying them to b (to avoid exposing a reference to
          * b).
          */
         int read(byte[] b, int off, int len, boolean copy) throws IOException {
             if (len == 0) {
                 return 0;
             } else if (blkmode) {
                 if (pos == end) {
                     refill();
                 }
                 if (end < 0) {
                     return -1;
                 }
                 int nread = Math.min(len, end - pos);
                 System.arraycopy(buf, pos, b, off, nread);
                 pos += nread;
                 return nread;
             } else if (copy) {
                 int nread = in.read(buf, 0, Math.min(len, MAX_BLOCK_SIZE));
                 if (nread > 0) {
                     System.arraycopy(buf, 0, b, off, nread);
                 }
                 return nread;
             } else {
                 return in.read(b, off, len);
             }
         }
 
         /* ----------------- primitive data input methods ------------------ */
         /*
          * The following methods are equivalent to their counterparts in
          * DataInputStream, except that they interpret data block boundaries
          * and read the requested data from within data blocks when in block
          * data mode.
          */
 
         public void readFully(byte[] b) throws IOException {
             readFully(b, 0, b.length, false);
         }
 
         public void readFully(byte[] b, int off, int len) throws IOException {
             readFully(b, off, len, false);
         }
 
         public void readFully(byte[] b, int off, int len, boolean copy)
             throws IOException
         {
             while (len > 0) {
                 int n = read(b, off, len, copy);
                 if (n < 0) {
                     throw new EOFException();
                 }
                 off += n;
                 len -= n;
             }
         }
 
         public int skipBytes(int n) throws IOException {
             return din.skipBytes(n);
         }
 
         public boolean readBoolean() throws IOException {
             int v = read();
             if (v < 0) {
                 throw new EOFException();
             }
             return (v != 0);
         }
 
         public byte readByte() throws IOException {
             int v = read();
             if (v < 0) {
                 throw new EOFException();
             }
             return (byte) v;
         }
 
         public int readUnsignedByte() throws IOException {
             int v = read();
             if (v < 0) {
                 throw new EOFException();
             }
             return v;
         }
 
         public char readChar() throws IOException {
             if (!blkmode) {
                 pos = 0;
                 in.readFully(buf, 0, 2);
             } else if (end - pos < 2) {
                 return din.readChar();
             }
             char v = Bits.getChar(buf, pos);
             pos += 2;
             return v;
         }
 
         public short readShort() throws IOException {
             if (!blkmode) {
                 pos = 0;
                 in.readFully(buf, 0, 2);
             } else if (end - pos < 2) {
                 return din.readShort();
             }
             short v = Bits.getShort(buf, pos);
             pos += 2;
             return v;
         }
 
         public int readUnsignedShort() throws IOException {
             if (!blkmode) {
                 pos = 0;
                 in.readFully(buf, 0, 2);
             } else if (end - pos < 2) {
                 return din.readUnsignedShort();
             }
             int v = Bits.getShort(buf, pos) & 0xFFFF;
             pos += 2;
             return v;
         }
 
         public int readInt() throws IOException {
             if (!blkmode) {
                 pos = 0;
                 in.readFully(buf, 0, 4);
             } else if (end - pos < 4) {
                 return din.readInt();
             }
             int v = Bits.getInt(buf, pos);
             pos += 4;
             return v;
         }
 
         public float readFloat() throws IOException {
             if (!blkmode) {
                 pos = 0;
                 in.readFully(buf, 0, 4);
             } else if (end - pos < 4) {
                 return din.readFloat();
             }
             float v = Bits.getFloat(buf, pos);
             pos += 4;
             return v;
         }
 
         public long readLong() throws IOException {
             if (!blkmode) {
                 pos = 0;
                 in.readFully(buf, 0, 8);
             } else if (end - pos < 8) {
                 return din.readLong();
             }
             long v = Bits.getLong(buf, pos);
             pos += 8;
             return v;
         }
 
         public double readDouble() throws IOException {
             if (!blkmode) {
                 pos = 0;
                 in.readFully(buf, 0, 8);
             } else if (end - pos < 8) {
                 return din.readDouble();
             }
             double v = Bits.getDouble(buf, pos);
             pos += 8;
             return v;
         }
 
         public String readUTF() throws IOException {
             return readUTFBody(readUnsignedShort());
         }
 
         public String readLine() throws IOException {
             return din.readLine();      // deprecated, not worth optimizing
         }
 
         /* -------------- primitive data array input methods --------------- */
         /*
          * The following methods read in spans of primitive data values.
          * Though equivalent to calling the corresponding primitive read
          * methods repeatedly, these methods are optimized for reading groups
          * of primitive data values more efficiently.
          */
 
         void readBooleans(boolean[] v, int off, int len) throws IOException {
             int stop, endoff = off + len;
             while (off < endoff) {
                 if (!blkmode) {
                     int span = Math.min(endoff - off, MAX_BLOCK_SIZE);
                     in.readFully(buf, 0, span);
                     stop = off + span;
                     pos = 0;
                 } else if (end - pos < 1) {
                     v[off++] = din.readBoolean();
                     continue;
                 } else {
                     stop = Math.min(endoff, off + end - pos);
                 }
 
                 while (off < stop) {
                     v[off++] = Bits.getBoolean(buf, pos++);
                 }
             }
         }
 
         void readChars(char[] v, int off, int len) throws IOException {
             int stop, endoff = off + len;
             while (off < endoff) {
                 if (!blkmode) {
                     int span = Math.min(endoff - off, MAX_BLOCK_SIZE >> 1);
                     in.readFully(buf, 0, span << 1);
                     stop = off + span;
                     pos = 0;
                 } else if (end - pos < 2) {
                     v[off++] = din.readChar();
                     continue;
                 } else {
                     stop = Math.min(endoff, off + ((end - pos) >> 1));
                 }
 
                 while (off < stop) {
                     v[off++] = Bits.getChar(buf, pos);
                     pos += 2;
                 }
             }
         }
 
         void readShorts(short[] v, int off, int len) throws IOException {
             int stop, endoff = off + len;
             while (off < endoff) {
                 if (!blkmode) {
                     int span = Math.min(endoff - off, MAX_BLOCK_SIZE >> 1);
                     in.readFully(buf, 0, span << 1);
                     stop = off + span;
                     pos = 0;
                 } else if (end - pos < 2) {
                     v[off++] = din.readShort();
                     continue;
                 } else {
                     stop = Math.min(endoff, off + ((end - pos) >> 1));
                 }
 
                 while (off < stop) {
                     v[off++] = Bits.getShort(buf, pos);
                     pos += 2;
                 }
             }
         }
 
         void readInts(int[] v, int off, int len) throws IOException {
             int stop, endoff = off + len;
             while (off < endoff) {
                 if (!blkmode) {
                     int span = Math.min(endoff - off, MAX_BLOCK_SIZE >> 2);
                     in.readFully(buf, 0, span << 2);
                     stop = off + span;
                     pos = 0;
                 } else if (end - pos < 4) {
                     v[off++] = din.readInt();
                     continue;
                 } else {
                     stop = Math.min(endoff, off + ((end - pos) >> 2));
                 }
 
                 while (off < stop) {
                     v[off++] = Bits.getInt(buf, pos);
                     pos += 4;
                 }
             }
         }
 
         void readFloats(float[] v, int off, int len) throws IOException {
             int span, endoff = off + len;
             while (off < endoff) {
                 if (!blkmode) {
                     span = Math.min(endoff - off, MAX_BLOCK_SIZE >> 2);
                     in.readFully(buf, 0, span << 2);
                     pos = 0;
                 } else if (end - pos < 4) {
                     v[off++] = din.readFloat();
                     continue;
                 } else {
                     span = Math.min(endoff - off, ((end - pos) >> 2));
                 }
 
                 bytesToFloats(buf, pos, v, off, span);
                 off += span;
                 pos += span << 2;
             }
         }
 
         void readLongs(long[] v, int off, int len) throws IOException {
             int stop, endoff = off + len;
             while (off < endoff) {
                 if (!blkmode) {
                     int span = Math.min(endoff - off, MAX_BLOCK_SIZE >> 3);
                     in.readFully(buf, 0, span << 3);
                     stop = off + span;
                     pos = 0;
                 } else if (end - pos < 8) {
                     v[off++] = din.readLong();
                     continue;
                 } else {
                     stop = Math.min(endoff, off + ((end - pos) >> 3));
                 }
 
                 while (off < stop) {
                     v[off++] = Bits.getLong(buf, pos);
                     pos += 8;
                 }
             }
         }
 
         void readDoubles(double[] v, int off, int len) throws IOException {
             int span, endoff = off + len;
             while (off < endoff) {
                 if (!blkmode) {
                     span = Math.min(endoff - off, MAX_BLOCK_SIZE >> 3);
                     in.readFully(buf, 0, span << 3);
                     pos = 0;
                 } else if (end - pos < 8) {
                     v[off++] = din.readDouble();
                     continue;
                 } else {
                     span = Math.min(endoff - off, ((end - pos) >> 3));
                 }
 
                 bytesToDoubles(buf, pos, v, off, span);
                 off += span;
                 pos += span << 3;
             }
         }
 
         /**
          * Reads in string written 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.
          */
         String readLongUTF() throws IOException {
             return readUTFBody(readLong());
         }
 
         /**
          * Reads in the "body" (i.e., the UTF representation minus the 2-byte
          * or 8-byte length header) of a UTF encoding, which occupies the next
          * utflen bytes.
          */
         private String readUTFBody(long utflen) throws IOException {
             StringBuilder sbuf = new StringBuilder();
             if (!blkmode) {
                 end = pos = 0;
             }
 
             while (utflen > 0) {
                 int avail = end - pos;
                 if (avail >= 3 || (long) avail == utflen) {
                     utflen -= readUTFSpan(sbuf, utflen);
                 } else {
                     if (blkmode) {
                         // near block boundary, read one byte at a time
                         utflen -= readUTFChar(sbuf, utflen);
                     } else {
                         // shift and refill buffer manually
                         if (avail > 0) {
                             System.arraycopy(buf, pos, buf, 0, avail);
                         }
                         pos = 0;
                         end = (int) Math.min(MAX_BLOCK_SIZE, utflen);
                         in.readFully(buf, avail, end - avail);
                     }
                 }
             }
 
             return sbuf.toString();
         }
 
         /**
          * Reads span of UTF-encoded characters out of internal buffer
          * (starting at offset pos and ending at or before offset end),
          * consuming no more than utflen bytes.  Appends read characters to
          * sbuf.  Returns the number of bytes consumed.
          */
         private long readUTFSpan(StringBuilder sbuf, long utflen)
             throws IOException
         {
             int cpos = 0;
             int start = pos;
             int avail = Math.min(end - pos, CHAR_BUF_SIZE);
             // stop short of last char unless all of utf bytes in buffer
             int stop = pos + ((utflen > avail) ? avail - 2 : (int) utflen);
             boolean outOfBounds = false;
 
             try {
                 while (pos < stop) {
                     int b1, b2, b3;
                     b1 = buf[pos++] & 0xFF;
                     switch (b1 >> 4) {
                         case 0:
                         case 1:
                         case 2:
                         case 3:
                         case 4:
                         case 5:
                         case 6:
                         case 7:   // 1 byte format: 0xxxxxxx
                             cbuf[cpos++] = (char) b1;
                             break;
 
                         case 12:
                         case 13:  // 2 byte format: 110xxxxx 10xxxxxx
                             b2 = buf[pos++];
                             if ((b2 & 0xC0) != 0x80) {
                                 throw new UTFDataFormatException();
                             }
                             cbuf[cpos++] = (char) (((b1 & 0x1F) << 6) |
                                                    ((b2 & 0x3F) << 0));
                             break;
 
                         case 14:  // 3 byte format: 1110xxxx 10xxxxxx 10xxxxxx
                             b3 = buf[pos + 1];
                             b2 = buf[pos + 0];
                             pos += 2;
                             if ((b2 & 0xC0) != 0x80 || (b3 & 0xC0) != 0x80) {
                                 throw new UTFDataFormatException();
                             }
                             cbuf[cpos++] = (char) (((b1 & 0x0F) << 12) |
                                                    ((b2 & 0x3F) << 6) |
                                                    ((b3 & 0x3F) << 0));
                             break;
 
                         default:  // 10xx xxxx, 1111 xxxx
                             throw new UTFDataFormatException();
                     }
                 }
             } catch (ArrayIndexOutOfBoundsException ex) {
                 outOfBounds = true;
             } finally {
                 if (outOfBounds || (pos - start) > utflen) {
                     /*
                      * Fix for 4450867: if a malformed utf char causes the
                      * conversion loop to scan past the expected end of the utf
                      * string, only consume the expected number of utf bytes.
                      */
                     pos = start + (int) utflen;
                     throw new UTFDataFormatException();
                 }
             }
 
             sbuf.append(cbuf, 0, cpos);
             return pos - start;
         }
 
         /**
          * Reads in single UTF-encoded character one byte at a time, appends
          * the character to sbuf, and returns the number of bytes consumed.
          * This method is used when reading in UTF strings written in block
          * data mode to handle UTF-encoded characters which (potentially)
          * straddle block-data boundaries.
          */
         private int readUTFChar(StringBuilder sbuf, long utflen)
             throws IOException
         {
             int b1, b2, b3;
             b1 = readByte() & 0xFF;
             switch (b1 >> 4) {
                 case 0:
                 case 1:
                 case 2:
                 case 3:
                 case 4:
                 case 5:
                 case 6:
                 case 7:     // 1 byte format: 0xxxxxxx
                     sbuf.append((char) b1);
                     return 1;
 
                 case 12:
                 case 13:    // 2 byte format: 110xxxxx 10xxxxxx
                     if (utflen < 2) {
                         throw new UTFDataFormatException();
                     }
                     b2 = readByte();
                     if ((b2 & 0xC0) != 0x80) {
                         throw new UTFDataFormatException();
                     }
                     sbuf.append((char) (((b1 & 0x1F) << 6) |
                                         ((b2 & 0x3F) << 0)));
                     return 2;
 
                 case 14:    // 3 byte format: 1110xxxx 10xxxxxx 10xxxxxx
                     if (utflen < 3) {
                         if (utflen == 2) {
                             readByte();         // consume remaining byte
                         }
                         throw new UTFDataFormatException();
                     }
                     b2 = readByte();
                     b3 = readByte();
                     if ((b2 & 0xC0) != 0x80 || (b3 & 0xC0) != 0x80) {
                         throw new UTFDataFormatException();
                     }
                     sbuf.append((char) (((b1 & 0x0F) << 12) |
                                         ((b2 & 0x3F) << 6) |
                                         ((b3 & 0x3F) << 0)));
                     return 3;
 
                 default:   // 10xx xxxx, 1111 xxxx
                     throw new UTFDataFormatException();
             }
         }
     }
 
     /**
      * Unsynchronized table which tracks wire handle to object mappings, as
      * well as ClassNotFoundExceptions associated with deserialized objects.
      * This class implements an exception-propagation algorithm for
      * determining which objects should have ClassNotFoundExceptions associated
      * with them, taking into account cycles and discontinuities (e.g., skipped
      * fields) in the object graph.
      *
      * <p>General use of the table is as follows: during deserialization, a
      * given object is first assigned a handle by calling the assign method.
      * This method leaves the assigned handle in an "open" state, wherein
      * dependencies on the exception status of other handles can be registered
      * by calling the markDependency method, or an exception can be directly
      * associated with the handle by calling markException.  When a handle is
      * tagged with an exception, the HandleTable assumes responsibility for
      * propagating the exception to any other objects which depend
      * (transitively) on the exception-tagged object.
      *
      * <p>Once all exception information/dependencies for the handle have been
      * registered, the handle should be "closed" by calling the finish method
      * on it.  The act of finishing a handle allows the exception propagation
      * algorithm to aggressively prune dependency links, lessening the
      * performance/memory impact of exception tracking.
      *
      * <p>Note that the exception propagation algorithm used depends on handles
      * being assigned/finished in LIFO order; however, for simplicity as well
      * as memory conservation, it does not enforce this constraint.
      */
     // REMIND: add full description of exception propagation algorithm?
     private static class HandleTable {
 
         /* status codes indicating whether object has associated exception */
         private static final byte STATUS_OK = 1;
         private static final byte STATUS_UNKNOWN = 2;
         private static final byte STATUS_EXCEPTION = 3;
 
         /** array mapping handle -> object status */
         byte[] status;
         /** array mapping handle -> object/exception (depending on status) */
         Object[] entries;
         /** array mapping handle -> list of dependent handles (if any) */
         HandleList[] deps;
         /** lowest unresolved dependency */
         int lowDep = -1;
         /** number of handles in table */
         int size = 0;
 
         /**
          * Creates handle table with the given initial capacity.
          */
         HandleTable(int initialCapacity) {
             status = new byte[initialCapacity];
             entries = new Object[initialCapacity];
             deps = new HandleList[initialCapacity];
         }
 
         /**
          * Assigns next available handle to given object, and returns assigned
          * handle.  Once object has been completely deserialized (and all
          * dependencies on other objects identified), the handle should be
          * "closed" by passing it to finish().
          */
         int assign(Object obj) {
             if (size >= entries.length) {
                 grow();
             }
             status[size] = STATUS_UNKNOWN;
             entries[size] = obj;
             return size++;
         }
 
         /**
          * Registers a dependency (in exception status) of one handle on
          * another.  The dependent handle must be "open" (i.e., assigned, but
          * not finished yet).  No action is taken if either dependent or target
          * handle is NULL_HANDLE.
          */
         void markDependency(int dependent, int target) {
             if (dependent == NULL_HANDLE || target == NULL_HANDLE) {
                 return;
             }
             switch (status[dependent]) {
 
                 case STATUS_UNKNOWN:
                     switch (status[target]) {
                         case STATUS_OK:
                             // ignore dependencies on objs with no exception
                             break;
 
                         case STATUS_EXCEPTION:
                             // eagerly propagate exception
                             markException(dependent,
                                 (ClassNotFoundException) entries[target]);
                             break;
 
                         case STATUS_UNKNOWN:
                             // add to dependency list of target
                             if (deps[target] == null) {
                                 deps[target] = new HandleList();
                             }
                             deps[target].add(dependent);
 
                             // remember lowest unresolved target seen
                             if (lowDep < 0 || lowDep > target) {
                                 lowDep = target;
                             }
                             break;
 
                         default:
                             throw new InternalError();
                     }
                     break;
 
                 case STATUS_EXCEPTION:
                     break;
 
                 default:
                     throw new InternalError();
             }
         }
 
         /**
          * Associates a ClassNotFoundException (if one not already associated)
          * with the currently active handle and propagates it to other
          * referencing objects as appropriate.  The specified handle must be
          * "open" (i.e., assigned, but not finished yet).
          */
         void markException(int handle, ClassNotFoundException ex) {
             switch (status[handle]) {
                 case STATUS_UNKNOWN:
                     status[handle] = STATUS_EXCEPTION;
                     entries[handle] = ex;
 
                     // propagate exception to dependents
                     HandleList dlist = deps[handle];
                     if (dlist != null) {
                         int ndeps = dlist.size();
                         for (int i = 0; i < ndeps; i++) {
                             markException(dlist.get(i), ex);
                         }
                         deps[handle] = null;
                     }
                     break;
 
                 case STATUS_EXCEPTION:
                     break;
 
                 default:
                     throw new InternalError();
             }
         }
 
         /**
          * Marks given handle as finished, meaning that no new dependencies
          * will be marked for handle.  Calls to the assign and finish methods
          * must occur in LIFO order.
          */
         void finish(int handle) {
             int end;
             if (lowDep < 0) {
                 // no pending unknowns, only resolve current handle
                 end = handle + 1;
             } else if (lowDep >= handle) {
                 // pending unknowns now clearable, resolve all upward handles
                 end = size;
                 lowDep = -1;
             } else {
                 // unresolved backrefs present, can't resolve anything yet
                 return;
             }
 
             // change STATUS_UNKNOWN -> STATUS_OK in selected span of handles
             for (int i = handle; i < end; i++) {
                 switch (status[i]) {
                     case STATUS_UNKNOWN:
                         status[i] = STATUS_OK;
                         deps[i] = null;
                         break;
 
                     case STATUS_OK:
                     case STATUS_EXCEPTION:
                         break;
 
                     default:
                         throw new InternalError();
                 }
             }
         }
 
         /**
          * Assigns a new object to the given handle.  The object previously
          * associated with the handle is forgotten.  This method has no effect
          * if the given handle already has an exception associated with it.
          * This method may be called at any time after the handle is assigned.
          */
         void setObject(int handle, Object obj) {
             switch (status[handle]) {
                 case STATUS_UNKNOWN:
                 case STATUS_OK:
                     entries[handle] = obj;
                     break;
 
                 case STATUS_EXCEPTION:
                     break;
 
                 default:
                     throw new InternalError();
             }
         }
 
         /**
          * Looks up and returns object associated with the given handle.
          * Returns null if the given handle is NULL_HANDLE, or if it has an
          * associated ClassNotFoundException.
          */
         Object lookupObject(int handle) {
             return (handle != NULL_HANDLE &&
                     status[handle] != STATUS_EXCEPTION) ?
                 entries[handle] : null;
         }
 
         /**
          * Looks up and returns ClassNotFoundException associated with the
          * given handle.  Returns null if the given handle is NULL_HANDLE, or
          * if there is no ClassNotFoundException associated with the handle.
          */
         ClassNotFoundException lookupException(int handle) {
             return (handle != NULL_HANDLE &&
                     status[handle] == STATUS_EXCEPTION) ?
                 (ClassNotFoundException) entries[handle] : null;
         }
 
         /**
          * Resets table to its initial state.
          */
         void clear() {
             Arrays.fill(status, 0, size, (byte) 0);
             Arrays.fill(entries, 0, size, null);
             Arrays.fill(deps, 0, size, null);
             lowDep = -1;
             size = 0;
         }
 
         /**
          * Returns number of handles registered in table.
          */
         int size() {
             return size;
         }
 
         /**
          * Expands capacity of internal arrays.
          */
         private void grow() {
             int newCapacity = (entries.length << 1) + 1;
 
             byte[] newStatus = new byte[newCapacity];
             Object[] newEntries = new Object[newCapacity];
             HandleList[] newDeps = new HandleList[newCapacity];
 
             System.arraycopy(status, 0, newStatus, 0, size);
             System.arraycopy(entries, 0, newEntries, 0, size);
             System.arraycopy(deps, 0, newDeps, 0, size);
 
             status = newStatus;
             entries = newEntries;
             deps = newDeps;
         }
 
         /**
          * Simple growable list of (integer) handles.
          */
         private static class HandleList {
             private int[] list = new int[4];
             private int size = 0;
 
             public HandleList() {
             }
 
             public void add(int handle) {
                 if (size >= list.length) {
                     int[] newList = new int[list.length << 1];
                     System.arraycopy(list, 0, newList, 0, list.length);
                     list = newList;
                 }
                 list[size++] = handle;
             }
 
             public int get(int index) {
                 if (index >= size) {
                     throw new ArrayIndexOutOfBoundsException();
                 }
                 return list[index];
             }
 
             public int size() {
                 return size;
             }
         }
     }
 
     /**
      * Method for cloning arrays in case of using unsharing reading
      */
     private static Object cloneArray(Object array) {
         if (array instanceof Object[]) {
             return ((Object[]) array).clone();
         } else if (array instanceof boolean[]) {
             return ((boolean[]) array).clone();
         } else if (array instanceof byte[]) {
             return ((byte[]) array).clone();
         } else if (array instanceof char[]) {
             return ((char[]) array).clone();
         } else if (array instanceof double[]) {
             return ((double[]) array).clone();
         } else if (array instanceof float[]) {
             return ((float[]) array).clone();
         } else if (array instanceof int[]) {
             return ((int[]) array).clone();
         } else if (array instanceof long[]) {
             return ((long[]) array).clone();
         } else if (array instanceof short[]) {
             return ((short[]) array).clone();
         } else {
             throw new AssertionError();
         }
     }
 
 }