/*
 * Copyright (c) 1996, 2020, 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).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 */

package java.io;

import java.io.ObjectStreamClass.WeakClassKey;
import java.io.ObjectStreamClass.RecordSupport;
import java.lang.System.Logger;
import java.lang.invoke.MethodHandle;
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.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import static java.io.ObjectStreamClass.processQueue;

import jdk.internal.access.SharedSecrets;
import jdk.internal.misc.Unsafe;
import sun.reflect.misc.ReflectUtil;
import sun.security.action.GetBooleanAction;

An ObjectInputStream deserializes primitive data and objects previously
written using an ObjectOutputStream.
Warning: Deserialization of untrusted data is inherently dangerous
and should be avoided. Untrusted data should be carefully validated according to the
"Serialization and Deserialization" section of the
{@extLink secure_coding_guidelines_javase Secure Coding Guidelines for Java SE}.
{@extLink serialization_filter_guide Serialization Filtering} describes best
practices for defensive use of serial filters.

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.
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.
Only objects that support the java.io.Serializable or
java.io.Externalizable interface can be read from streams.
The method readObject 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. 
Primitive data types can be read from the stream using the appropriate
method on DataInput.
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.
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.
For example to read from a stream as written by the example in
ObjectOutputStream:


     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();

Classes control how they are serialized by implementing either the
java.io.Serializable or java.io.Externalizable interfaces.
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.
Serializable classes that require special handling during the
serialization and deserialization process should implement the following
methods:
private void writeObject(java.io.ObjectOutputStream stream)
    throws IOException;
private void readObject(java.io.ObjectInputStream stream)
    throws IOException, ClassNotFoundException;
private void readObjectNoData()
    throws ObjectStreamException;

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.
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.
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 ObjectStreamConstants.PROTOCOL_VERSION_1 protocol, in which the end of data written by writeExternal methods is not demarcated, and hence cannot be detected. 
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.
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.
The contents of the stream can be filtered during deserialization. If a filter is set on an ObjectInputStream, the ObjectInputFilter can check that the classes, array lengths, number of references in the stream, depth, and number of bytes consumed from the input stream are allowed and if not, can terminate deserialization. A system-wide filter can be configured that is applied to each ObjectInputStream unless replaced using setObjectInputFilter. 
Any exception that occurs while deserializing an object will be caught by
the ObjectInputStream and abort the reading process.
Implementing the Externalizable interface allows the object to assume
complete control over the contents and format of the object's serialized
form.  The methods of the Externalizable interface, writeExternal and
readExternal, are called to save and restore the objects state.  When
implemented by a class they can write and read their own state using all of
the methods of ObjectOutput and ObjectInput.  It is the responsibility of
the objects to handle any versioning that occurs.
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 Enum.valueOf(Class, String) 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,      Roger Riggs
See Also:
DataInput
ObjectOutputStream
Serializable

 *     Object Serialization Specification, Section 3, Object Input Classes
Implementation Requirements:


Records are serialized differently than ordinary serializable or externalizable
objects. The serialized form of a record object is a sequence of values derived
from the record components. The stream format of a record object is the same as
that of an ordinary object in the stream. During deserialization, if the local
class equivalent of the specified stream class descriptor is a record class,
then first the stream fields are read and reconstructed to serve as the record's
component values; and second, a record object is created by invoking the
record's canonical constructor with the component values as arguments (or the
default value for component's type if a component value is absent from the
stream).
Like other serializable or externalizable objects, record objects can function
as the target of back references appearing subsequently in the serialization
stream. However, a cycle in the graph where the record object is referred to,
either directly or transitively, by one of its components, is not preserved.
The record components are deserialized prior to the invocation of the record
constructor, hence this limitation (see

[Section 1.14, "Circular References" for additional information).
The process by which record objects are serialized or externalized cannot be
customized; any class-specific writeObject, readObject, readObjectNoData,
writeExternal, and readExternal methods defined by record classes are
ignored during serialization and deserialization. However, a substitute object
to be serialized or a designate replacement may be specified, by the
writeReplace and readResolve methods, respectively.  Any
serialPersistentFields field declaration is ignored. Documenting serializable
fields and data for record classes is unnecessary, since there is no variation
in the serial form, other than whether a substitute or replacement object is
used. The serialVersionUID of a record class is 0L unless explicitly
declared. The requirement for matching serialVersionUID values is waived for
record classes.
Since:
  1.1/**
 * An ObjectInputStream deserializes primitive data and objects previously
 * written using an ObjectOutputStream.
 *
 * <p><strong>Warning: Deserialization of untrusted data is inherently dangerous
 * and should be avoided. Untrusted data should be carefully validated according to the
 * "Serialization and Deserialization" section of the
 * {@extLink secure_coding_guidelines_javase Secure Coding Guidelines for Java SE}.
 * {@extLink serialization_filter_guide Serialization Filtering} describes best
 * practices for defensive use of serial filters.
 * </strong></p>
 *
 * <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} 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:
 *
 * <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} 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>The contents of the stream can be filtered during deserialization.
 * If a {@linkplain #setObjectInputFilter(ObjectInputFilter) filter is set}
 * on an ObjectInputStream, the {@link ObjectInputFilter} can check that
 * the classes, array lengths, number of references in the stream, depth, and
 * number of bytes consumed from the input stream are allowed and
 * if not, can terminate deserialization.
 * A {@linkplain ObjectInputFilter.Config#setSerialFilter(ObjectInputFilter) system-wide filter}
 * can be configured that is applied to each {@code ObjectInputStream} unless replaced
 * using {@link #setObjectInputFilter(ObjectInputFilter) setObjectInputFilter}.
 *
 * <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)} 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.
 *
 * @implSpec
 * <a id="record-serialization"></a>
 * Records are serialized differently than ordinary serializable or externalizable
 * objects. The serialized form of a record object is a sequence of values derived
 * from the record components. The stream format of a record object is the same as
 * that of an ordinary object in the stream. During deserialization, if the local
 * class equivalent of the specified stream class descriptor is a record class,
 * then first the stream fields are read and reconstructed to serve as the record's
 * component values; and second, a record object is created by invoking the
 * record's <i>canonical</i> constructor with the component values as arguments (or the
 * default value for component's type if a component value is absent from the
 * stream).
 * Like other serializable or externalizable objects, record objects can function
 * as the target of back references appearing subsequently in the serialization
 * stream. However, a cycle in the graph where the record object is referred to,
 * either directly or transitively, by one of its components, is not preserved.
 * The record components are deserialized prior to the invocation of the record
 * constructor, hence this limitation (see
 * <a href="{@docRoot}/../specs/serialization/serial-arch.html#cyclic-references">
 * [Section 1.14, "Circular References"</a> for additional information).
 * The process by which record objects are serialized or externalized cannot be
 * customized; any class-specific writeObject, readObject, readObjectNoData,
 * writeExternal, and readExternal methods defined by record classes are
 * ignored during serialization and deserialization. However, a substitute object
 * to be serialized or a designate replacement may be specified, by the
 * writeReplace and readResolve methods, respectively.  Any
 * serialPersistentFields field declaration is ignored. Documenting serializable
 * fields and data for record classes is unnecessary, since there is no variation
 * in the serial form, other than whether a substitute or replacement object is
 * used. The serialVersionUID of a record class is 0L unless explicitly
 * declared. The requirement for matching serialVersionUID values is waived for
 * record classes.
 *
 * @author      Mike Warres
 * @author      Roger Riggs
 * @see java.io.DataInput
 * @see java.io.ObjectOutputStream
 * @see java.io.Serializable
 * @see <a href="{@docRoot}/../specs/serialization/input.html">
 *     Object Serialization Specification, Section 3, Object Input Classes</a>
 * @since   1.1
 */
public class ObjectInputStream
    extends InputStream implements ObjectInput, ObjectStreamConstants
{
    
handle value representing null /** handle value representing null */
    private static final int NULL_HANDLE = -1;

    
marker for unshared objects in internal handle table /** marker for unshared objects in internal handle table */
    private static final Object unsharedMarker = new Object();

    
immutable table mapping primitive type names to corresponding
class objects
/**
     * immutable table mapping primitive type names to corresponding
     * class objects
     */
    private static final Map<String, Class<?>> primClasses =
        Map.of("boolean", boolean.class,
               "byte", byte.class,
               "char", char.class,
               "short", short.class,
               "int", int.class,
               "long", long.class,
               "float", float.class,
               "double", double.class,
               "void", void.class);

    private static class Caches {
        
cache of subclass security audit results /** cache of subclass security audit results */
        static final ConcurrentMap<WeakClassKey,Boolean> subclassAudits =
            new ConcurrentHashMap<>();

        
queue for WeakReferences to audited subclasses /** queue for WeakReferences to audited subclasses */
        static final ReferenceQueue<Class<?>> subclassAuditsQueue =
            new ReferenceQueue<>();

        
Property to permit setting a filter after objects have been read. See ObjectInputStream.setObjectInputFilter(ObjectInputFilter) /**
         * Property to permit setting a filter after objects
         * have been read.
         * See {@link #setObjectInputFilter(ObjectInputFilter)}
         */
        static final boolean SET_FILTER_AFTER_READ = GetBooleanAction
                .privilegedGetProperty("jdk.serialSetFilterAfterRead");
    }

    /*
     * Separate class to defer initialization of logging until needed.
     */
    private static class Logging {
        /*
         * Logger for ObjectInputFilter results.
         * Setup the filter logger if it is set to DEBUG or TRACE.
         * (Assuming it will not change).
         */
        static final System.Logger filterLogger;

        static {
            Logger filterLog = System.getLogger("java.io.serialization");
            filterLogger = (filterLog.isLoggable(Logger.Level.DEBUG)
                    || filterLog.isLoggable(Logger.Level.TRACE)) ? filterLog : null;
        }
    }

    
filter stream for handling block data conversion /** filter stream for handling block data conversion */
    private final BlockDataInputStream bin;
    
validation callback list /** validation callback list */
    private final ValidationList vlist;
    
recursion depth /** recursion depth */
    private long depth;
    
Total number of references to any type of object, class, enum, proxy, etc. /** Total number of references to any type of object, class, enum, proxy, etc. */
    private long totalObjectRefs;
    
whether stream is closed /** whether stream is closed */
    private boolean closed;

    
wire handle -> obj/exception map /** wire handle -> obj/exception map */
    private final HandleTable handles;
    
scratch field for passing handle values up/down call stack /** 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 /** flag set when at end of field value block with no TC_ENDBLOCKDATA */
    private boolean defaultDataEnd = false;

    
if true, invoke readObjectOverride() instead of readObject() /** if true, invoke readObjectOverride() instead of readObject() */
    private final boolean enableOverride;
    
if true, invoke resolveObject() /** 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.
/**
     * 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;

    
Filter of class descriptors and classes read from the stream;
may be null.
/**
     * Filter of class descriptors and classes read from the stream;
     * may be null.
     */
    private ObjectInputFilter serialFilter;

    
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.
The serialization filter is initialized to the value of the system-wide filter. 
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.
Params:
in – input stream to read from
Throws:
StreamCorruptedException – if the stream header is incorrect
IOException – if an I/O error occurs while reading stream header
SecurityException – if untrusted subclass illegally overrides
         security-sensitive methods
NullPointerException – if in is null
See Also:
ObjectInputStream()
readFields()
ObjectOutputStream(OutputStream)/**
     * 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>The serialization filter is initialized to the value of
     * {@linkplain ObjectInputFilter.Config#getSerialFilter() the system-wide filter}.
     *
     * <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} is {@code null}
     * @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();
        serialFilter = ObjectInputFilter.Config.getSerialFilter();
        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.
The serialization filter is initialized to the value of the system-wide filter. 
If there is a security manager installed, this method first calls the security manager's checkPermission method with the SerializablePermission("enableSubclassImplementation") permission to ensure it's ok to enable subclassing. 
Throws:
SecurityException – if a security manager exists and its checkPermission method denies enabling subclassing.
IOException – if an I/O error occurs while creating this stream
See Also:
SecurityManager.checkPermission
SerializablePermission/**
     * 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>The serialization filter is initialized to the value of
     * {@linkplain ObjectInputFilter.Config#getSerialFilter() the system-wide filter}.
     *
     * <p>If there is a security manager installed, this method first calls the
     * security manager's {@code checkPermission} method with the
     * {@code SerializablePermission("enableSubclassImplementation")}
     * permission to ensure it's ok to enable subclassing.
     *
     * @throws  SecurityException if a security manager exists and its
     *          {@code checkPermission} method denies enabling
     *          subclassing.
     * @throws  IOException if an I/O error occurs while creating this stream
     * @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;
        serialFilter = ObjectInputFilter.Config.getSerialFilter();
        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 overridden 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.
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.
The serialization filter, when not null, is invoked for each object (regular or class) read to reconstruct the root object. See setObjectInputFilter for details. 
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.
InvalidClassException – Something is wrong with a class used by
         serialization.
StreamCorruptedException – Control information in the
         stream is inconsistent.
OptionalDataException – Primitive data was found in the
         stream instead of objects.
IOException – Any of the usual Input/Output related exceptions./**
     * 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 overridden 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>The serialization filter, when not {@code null}, is invoked for
     * each object (regular or class) read to reconstruct the root object.
     * See {@link #setObjectInputFilter(ObjectInputFilter) setObjectInputFilter} for details.
     *
     * <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 {
        return readObject(Object.class);
    }

    
Reads a String and only a string.
Throws:
EOFException – If end of file is reached.
IOException – If other I/O error has occurred.
Returns:
 the String read/**
     * Reads a String and only a string.
     *
     * @return  the String read
     * @throws  EOFException If end of file is reached.
     * @throws  IOException If other I/O error has occurred.
     */
    private String readString() throws IOException {
        try {
            return (String) readObject(String.class);
        } catch (ClassNotFoundException cnf) {
            throw new IllegalStateException(cnf);
        }
    }

    
Internal method to read an object from the ObjectInputStream of the expected type. Called only from readObject() and readString(). Only Object.class and String.class are supported. 
Params:
type – the type expected; either Object.class or String.class
Throws:
IOException – Any of the usual Input/Output related exceptions.
ClassNotFoundException – Class of a serialized object cannot be
         found.
Returns:
an object of the type/**
     * Internal method to read an object from the ObjectInputStream of the expected type.
     * Called only from {@code readObject()} and {@code readString()}.
     * Only {@code Object.class} and {@code String.class} are supported.
     *
     * @param type the type expected; either Object.class or String.class
     * @return an object of the type
     * @throws  IOException Any of the usual Input/Output related exceptions.
     * @throws  ClassNotFoundException Class of a serialized object cannot be
     *          found.
     */
    private final Object readObject(Class<?> type)
        throws IOException, ClassNotFoundException
    {
        if (enableOverride) {
            return readObjectOverride();
        }

        if (! (type == Object.class || type == String.class))
            throw new AssertionError("internal error");

        // if nested read, passHandle contains handle of enclosing object
        int outerHandle = passHandle;
        try {
            Object obj = readObject0(type, false);
            handles.markDependency(outerHandle, passHandle);
            ClassNotFoundException ex = handles.lookupException(passHandle);
            if (ex != null) {
                throw ex;
            }
            if (depth == 0) {
                vlist.doCallbacks();
                freeze();
            }
            return obj;
        } finally {
            passHandle = outerHandle;
            if (closed && depth == 0) {
                clear();
            }
        }
    }

    
This method is called by trusted subclasses of ObjectInputStream that
constructed ObjectInputStream using the protected no-arg constructor.
The subclass is expected to provide an override method with the modifier
"final".
Throws:
ClassNotFoundException – Class definition of a serialized object
         cannot be found.
OptionalDataException – Primitive data was found in the stream
         instead of objects.
IOException – if I/O errors occurred while reading from the
         underlying stream
See Also:
ObjectInputStream()
readObject()
Returns:
 the Object read from the stream.
Since:
1.2/**
     * This method is called by trusted subclasses of ObjectInputStream that
     * constructed ObjectInputStream using the protected no-arg constructor.
     * The subclass is expected to provide an override method with the modifier
     * "final".
     *
     * @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:

  
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.
  
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.

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.
The serialization filter, when not null, is invoked for each object (regular or class) read to reconstruct the root object. See setObjectInputFilter for details. 
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.
Throws:
ClassNotFoundException – if class of an object to deserialize
         cannot be found
StreamCorruptedException – if control information in the stream
         is inconsistent
ObjectStreamException – if object to deserialize has already
         appeared in stream
OptionalDataException – if primitive data is next in stream
IOException – if an I/O error occurs during deserialization
Returns:
 reference to deserialized object
Since:
  1.4/**
     * 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>The serialization filter, when not {@code null}, is invoked for
     * each object (regular or class) read to reconstruct the root object.
     * See {@link #setObjectInputFilter(ObjectInputFilter) setObjectInputFilter} for details.
     *
     * <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(Object.class, true);
            handles.markDependency(outerHandle, passHandle);
            ClassNotFoundException ex = handles.lookupException(passHandle);
            if (ex != null) {
                throw ex;
            }
            if (depth == 0) {
                vlist.doCallbacks();
                freeze();
            }
            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.
IOException – if an I/O error occurs.
NotActiveException – if the stream is not currently reading
         objects./**
     * 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
    {
        SerialCallbackContext ctx = curContext;
        if (ctx == null) {
            throw new NotActiveException("not in call to readObject");
        }
        Object curObj = ctx.getObj();
        ObjectStreamClass curDesc = ctx.getDesc();
        bin.setBlockDataMode(false);
        FieldValues vals = defaultReadFields(curObj, curDesc);
        if (curObj != null) {
            defaultCheckFieldValues(curObj, curDesc, vals);
            defaultSetFieldValues(curObj, curDesc, vals);
        }
        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.
Throws:
ClassNotFoundException – if the class of a serialized object
         could not be found.
IOException – if an I/O error occurs.
NotActiveException – if the stream is not currently reading
         objects.
Returns:
 the GetField object representing the persistent fields of the object being deserialized
Since:
1.2/**
     * Reads the persistent fields from the stream and makes them available by
     * name.
     *
     * @return  the {@code GetField} 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
    {
        SerialCallbackContext ctx = curContext;
        if (ctx == null) {
            throw new NotActiveException("not in call to readObject");
        }
        ctx.checkAndSetUsed();
        ObjectStreamClass curDesc = ctx.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.
Params:
obj – the object to receive the validation callback.
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.
InvalidObjectException – The validation object is null./**
     * 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.
The corresponding method in ObjectOutputStream is annotateClass. 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 Class 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 InvalidClassException is thrown. 
The default implementation of this method in ObjectInputStream returns the result of calling 
    Class.forName(desc.getName(), false, loader)
 where loader is the first class loader on the current thread's stack (starting from the currently executing method) that is neither the platform
class loader nor its ancestor; otherwise, loader is the platform class loader. If this call results in a ClassNotFoundException and the name of the passed ObjectStreamClass instance is the Java language keyword for a primitive type or void, then the Class object representing that primitive type or void will be returned (e.g., an ObjectStreamClass with the name "int" will be resolved to Integer.TYPE). Otherwise, the ClassNotFoundException will be thrown to the caller of this method. 
Params:
desc – an instance of class ObjectStreamClass
Throws:
IOException – any of the usual Input/Output exceptions.
ClassNotFoundException – if class of a serialized object cannot
         be found.
Returns:
 a Class object corresponding to desc/**
     * 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} is
     * {@code annotateClass}.  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} 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} returns the result of calling
     * <pre>
     *     Class.forName(desc.getName(), false, loader)
     * </pre>
     * where {@code loader} is the first class loader on the current
     * thread's stack (starting from the currently executing method) that is
     * neither the {@linkplain ClassLoader#getPlatformClassLoader() platform
     * class loader} nor its ancestor; otherwise, {@code loader} is the
     * <em>platform class loader</em>. If this call results in a
     * {@code ClassNotFoundException} and the name of the passed
     * {@code ObjectStreamClass} instance is the Java language keyword
     * for a primitive type or void, then the {@code Class} object
     * representing that primitive type or void will be returned
     * (e.g., an {@code ObjectStreamClass} with the name
     * {@code "int"} will be resolved to {@code Integer.TYPE}).
     * Otherwise, the {@code ClassNotFoundException} will be thrown to
     * the caller of this method.
     *
     * @param   desc an instance of class {@code ObjectStreamClass}
     * @return  a {@code Class} object corresponding to {@code desc}
     * @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.
This method is called exactly once for each unique proxy class
descriptor in the stream.
The corresponding method in ObjectOutputStream is annotateProxyClass. For a given subclass of ObjectInputStream that overrides this method, the annotateProxyClass method in the corresponding subclass of ObjectOutputStream must write any data or objects read by this method. 
The default implementation of this method in ObjectInputStream returns the result of calling Proxy.getProxyClass with the list of Class objects for the interfaces that are named in the interfaces parameter. The Class object for each interface name i is the value returned by calling 
    Class.forName(i, false, loader)
 where loader is the first class loader on the current thread's stack (starting from the currently executing method) that is neither the platform
class loader nor its ancestor; otherwise, loader is the platform class loader. Unless any of the resolved interfaces are non-public, this same value of loader is also the class loader passed to Proxy.getProxyClass; if non-public interfaces are present, their class loader is passed instead (if more than one non-public interface class loader is encountered, an IllegalAccessError is thrown). If Proxy.getProxyClass throws an IllegalArgumentException, resolveProxyClass will throw a ClassNotFoundException containing the IllegalArgumentException. 
Params:
interfaces – the list of interface names that were
               deserialized in the proxy class descriptor
Throws:
IOException – any exception thrown by the underlying InputStream
ClassNotFoundException – if the proxy class or any of the
               named interfaces could not be found
See Also:
ObjectOutputStream.annotateProxyClass(Class<?>)
Returns:
 a proxy class for the specified interfaces
Since:
1.3/**
     * 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} is
     * {@code annotateProxyClass}.  For a given subclass of
     * {@code ObjectInputStream} that overrides this method, the
     * {@code annotateProxyClass} method in the corresponding subclass of
     * {@code ObjectOutputStream} must write any data or objects read by
     * this method.
     *
     * <p>The default implementation of this method in
     * {@code ObjectInputStream} returns the result of calling
     * {@code Proxy.getProxyClass} with the list of {@code Class}
     * objects for the interfaces that are named in the {@code interfaces}
     * parameter.  The {@code Class} object for each interface name
     * {@code i} is the value returned by calling
     * <pre>
     *     Class.forName(i, false, loader)
     * </pre>
     * where {@code loader} is the first class loader on the current
     * thread's stack (starting from the currently executing method) that is
     * neither the {@linkplain ClassLoader#getPlatformClassLoader() platform
     * class loader} nor its ancestor; otherwise, {@code loader} is the
     * <em>platform class loader</em>.
     * Unless any of the resolved interfaces are non-public, this same value
     * of {@code loader} is also the class loader passed to
     * {@code Proxy.getProxyClass}; 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} is thrown).
     * If {@code Proxy.getProxyClass} throws an
     * {@code IllegalArgumentException}, {@code resolveProxyClass}
     * will throw a {@code ClassNotFoundException} containing the
     * {@code IllegalArgumentException}.
     *
     * @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}
     * @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 {
            @SuppressWarnings("deprecation")
            Class<?> proxyClass = Proxy.getProxyClass(
                hasNonPublicInterface ? nonPublicLoader : latestLoader,
                classObjs);
            return proxyClass;
        } 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.
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.
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.
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.
Params:
obj – object to be substituted
Throws:
IOException – Any of the usual Input/Output exceptions.
Returns:
 the substituted object/**
     * 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;
    }

    
Enables the stream to do replacement of objects read from the stream. When enabled, the resolveObject method is called for every object being deserialized. 
If object replacement is currently not enabled, and enable is true, and there is a security manager installed, this method first calls the security manager's checkPermission method with the SerializablePermission("enableSubstitution") permission to ensure that the caller is permitted to enable the stream to do replacement of objects read from the stream. 
Params:
enable – true for enabling use of resolveObject for every object being deserialized
Throws:
SecurityException – if a security manager exists and its checkPermission method denies enabling the stream to do replacement of objects read from the stream.
See Also:
SecurityManager.checkPermission
SerializablePermission
Returns:
 the previous setting before this method was invoked/**
     * Enables the stream to do replacement of objects read from the stream. When
     * enabled, the {@link #resolveObject} method is called for every object being
     * deserialized.
     *
     * <p>If object replacement is currently not enabled, and
     * {@code enable} is true, and there is a security manager installed,
     * this method first calls the security manager's
     * {@code checkPermission} method with the
     * {@code SerializablePermission("enableSubstitution")} permission to
     * ensure that the caller is permitted to enable the stream to do replacement
     * of objects read from the stream.
     *
     * @param   enable true for enabling use of {@code resolveObject} 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} method denies enabling the stream
     *          to do replacement of objects read from the stream.
     * @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 InputStream
StreamCorruptedException – if control information in the stream
         is inconsistent/**
     * 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}
     * @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 writeClassDescriptor method). By default, this method reads class descriptors according to the format defined in the Object Serialization specification. 
Throws:
IOException – If an I/O error has occurred.
ClassNotFoundException – If the Class of a serialized object used
         in the class descriptor representation cannot be found
See Also:
ObjectOutputStream.writeClassDescriptor(ObjectStreamClass)
Returns:
 the class descriptor read
Since:
1.3/**
     * 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} 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.
Throws:
IOException – If an I/O error has occurred.
Returns:
 the byte read, or -1 if the end of the stream is reached./**
     * 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.
Params:
buf – the buffer into which the data is read
off – the start offset in the destination array buf
len – the maximum number of bytes read
Throws:
NullPointerException – if buf is null.
IndexOutOfBoundsException – if off is negative, len is negative, or len is greater than buf.length - off.
IOException – If an I/O error has occurred.
See Also:
DataInputStream.readFully(byte[], int, int)
Returns:
 the actual number of bytes read, -1 is returned when the end of
         the stream is reached./**
     * 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 in the destination array {@code buf}
     * @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  NullPointerException if {@code buf} is {@code null}.
     * @throws  IndexOutOfBoundsException if {@code off} is negative,
     *          {@code len} is negative, or {@code len} is greater than
     *          {@code buf.length - off}.
     * @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.
Throws:
IOException – if there are I/O errors while reading from the underlying InputStream
Returns:
 the number of available bytes./**
     * 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}
     */
    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./**
     * 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.
Throws:
EOFException – If end of file is reached.
IOException – If other I/O error has occurred.
Returns:
 the boolean read./**
     * 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.
Throws:
EOFException – If end of file is reached.
IOException – If other I/O error has occurred.
Returns:
 the 8 bit byte read./**
     * 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.
Throws:
EOFException – If end of file is reached.
IOException – If other I/O error has occurred.
Returns:
 the 8 bit byte read./**
     * 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.
Throws:
EOFException – If end of file is reached.
IOException – If other I/O error has occurred.
Returns:
 the 16 bit char read./**
     * 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.
Throws:
EOFException – If end of file is reached.
IOException – If other I/O error has occurred.
Returns:
 the 16 bit short read./**
     * 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.
Throws:
EOFException – If end of file is reached.
IOException – If other I/O error has occurred.
Returns:
 the 16 bit short read./**
     * 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.
Throws:
EOFException – If end of file is reached.
IOException – If other I/O error has occurred.
Returns:
 the 32 bit integer read./**
     * 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.
Throws:
EOFException – If end of file is reached.
IOException – If other I/O error has occurred.
Returns:
 the read 64 bit long./**
     * 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.
Throws:
EOFException – If end of file is reached.
IOException – If other I/O error has occurred.
Returns:
 the 32 bit float read./**
     * 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.
Throws:
EOFException – If end of file is reached.
IOException – If other I/O error has occurred.
Returns:
 the 64 bit double read./**
     * 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.
Params:
buf – the buffer into which the data is read
Throws:
NullPointerException – If buf is null.
EOFException – If end of file is reached.
IOException – If other I/O error has occurred./**
     * Reads bytes, blocking until all bytes are read.
     *
     * @param   buf the buffer into which the data is read
     * @throws  NullPointerException If {@code buf} is {@code null}.
     * @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.
Params:
buf – the buffer into which the data is read
off – the start offset into the data array buf
len – the maximum number of bytes to read
Throws:
NullPointerException – If buf is null.
IndexOutOfBoundsException – If off is negative, len is negative, or len is greater than buf.length - off.
EOFException – If end of file is reached.
IOException – If other I/O error has occurred./**
     * Reads bytes, blocking until all bytes are read.
     *
     * @param   buf the buffer into which the data is read
     * @param   off the start offset into the data array {@code buf}
     * @param   len the maximum number of bytes to read
     * @throws  NullPointerException If {@code buf} is {@code null}.
     * @throws  IndexOutOfBoundsException If {@code off} is negative,
     *          {@code len} is negative, or {@code len} is greater than
     *          {@code buf.length - off}.
     * @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.
Params:
len – the number of bytes to be skipped
Throws:
IOException – If an I/O error has occurred.
Returns:
 the actual number of bytes skipped./**
     * 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.
Throws:
IOException – if there are I/O errors while reading from the underlying InputStream
Returns:
 a String copy of the line.
Deprecated:
This method does not properly convert bytes to characters.
         see DataInputStream for the details and alternatives./**
     * 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}
     * @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
modified UTF-8
format.
Throws:
IOException – if there are I/O errors while reading from the underlying InputStream
UTFDataFormatException – if read bytes do not represent a valid
         modified UTF-8 encoding of a string
Returns:
 the String./**
     * 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}
     * @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();
    }

    
Returns the serialization filter for this stream. The serialization filter is the most recent filter set in setObjectInputFilter or the initial system-wide filter from ObjectInputFilter.Config.getSerialFilter. 
Returns:
the serialization filter for the stream; may be null
Since:
9/**
     * Returns the serialization filter for this stream.
     * The serialization filter is the most recent filter set in
     * {@link #setObjectInputFilter setObjectInputFilter} or
     * the initial system-wide filter from
     * {@link ObjectInputFilter.Config#getSerialFilter() ObjectInputFilter.Config.getSerialFilter}.
     *
     * @return the serialization filter for the stream; may be null
     * @since 9
     */
    public final ObjectInputFilter getObjectInputFilter() {
        return serialFilter;
    }

    
Set the serialization filter for the stream. The filter's checkInput method is called for each class and reference in the stream. The filter can check any or all of the class, the array length, the number of references, the depth of the graph, and the size of the input stream. The depth is the number of nested readObject calls starting with the reading of the root of the graph being deserialized and the current object being deserialized. The number of references is the cumulative number of objects and references to objects already read from the stream including the current object being read. The filter is invoked only when reading objects from the stream and for not primitives. 
 If the filter returns Status.REJECTED, null or throws a RuntimeException, the active readObject or readUnshared throws InvalidClassException, otherwise deserialization continues uninterrupted. 
 The serialization filter is initialized to the value of ObjectInputFilter.Config.getSerialFilter when the  ObjectInputStream is constructed and can be set to a custom filter only once. The filter must be set before reading any objects from the stream; for example, by calling readObject or readUnshared. 
Params:
filter – the filter, may be null
Throws:
SecurityException – if there is security manager and the SerializablePermission("serialFilter") is not granted
IllegalStateException – if the current filter is not null and is not the system-wide filter, or if an object has been read
Implementation Requirements:
 The filter, when not null, is invoked during readObject and readUnshared for each object (regular or class) in the stream. Strings are treated as primitives and do not invoke the filter. The filter is called for: 

    
each object reference previously deserialized from the stream (class is null, arrayLength is -1), 
each regular class (class is not null, arrayLength is -1), 
each interface of a dynamic proxy and the dynamic proxy class itself (class is not null, arrayLength is -1), 
each array is filtered using the array type and length of the array
    (class is the array type, arrayLength is the requested length),
    
each object replaced by its class' readResolve method is filtered using the replacement object's class, if not null, and if it is an array, the arrayLength, otherwise -1, 
and each object replaced by resolveObject is filtered using the replacement object's class, if not null, and if it is an array, the arrayLength, otherwise -1. 
 When the checkInput method is invoked it is given access to the current class, the array length, the current number of references already read from the stream, the depth of nested calls to readObject or readUnshared, and the implementation dependent number of bytes consumed from the input stream. 
 Each call to readObject or readUnshared increases the depth by 1 before reading an object and decreases by 1 before returning normally or exceptionally. The depth starts at 1 and increases for each nested object and decrements when each nested call returns. The count of references in the stream starts at 1 and is increased before reading an object.
Since:
9/**
     * Set the serialization filter for the stream.
     * The filter's {@link ObjectInputFilter#checkInput checkInput} method is called
     * for each class and reference in the stream.
     * The filter can check any or all of the class, the array length, the number
     * of references, the depth of the graph, and the size of the input stream.
     * The depth is the number of nested {@linkplain #readObject readObject}
     * calls starting with the reading of the root of the graph being deserialized
     * and the current object being deserialized.
     * The number of references is the cumulative number of objects and references
     * to objects already read from the stream including the current object being read.
     * The filter is invoked only when reading objects from the stream and for
     * not primitives.
     * <p>
     * If the filter returns {@link ObjectInputFilter.Status#REJECTED Status.REJECTED},
     * {@code null} or throws a {@link RuntimeException},
     * the active {@code readObject} or {@code readUnshared}
     * throws {@link InvalidClassException}, otherwise deserialization
     * continues uninterrupted.
     * <p>
     * The serialization filter is initialized to the value of
     * {@link ObjectInputFilter.Config#getSerialFilter() ObjectInputFilter.Config.getSerialFilter}
     * when the {@code  ObjectInputStream} is constructed and can be set
     * to a custom filter only once.
     * The filter must be set before reading any objects from the stream;
     * for example, by calling {@link #readObject} or {@link #readUnshared}.
     *
     * @implSpec
     * The filter, when not {@code null}, is invoked during {@link #readObject readObject}
     * and {@link #readUnshared readUnshared} for each object (regular or class) in the stream.
     * Strings are treated as primitives and do not invoke the filter.
     * The filter is called for:
     * <ul>
     *     <li>each object reference previously deserialized from the stream
     *     (class is {@code null}, arrayLength is -1),
     *     <li>each regular class (class is not {@code null}, arrayLength is -1),
     *     <li>each interface of a dynamic proxy and the dynamic proxy class itself
     *     (class is not {@code null}, arrayLength is -1),
     *     <li>each array is filtered using the array type and length of the array
     *     (class is the array type, arrayLength is the requested length),
     *     <li>each object replaced by its class' {@code readResolve} method
     *         is filtered using the replacement object's class, if not {@code null},
     *         and if it is an array, the arrayLength, otherwise -1,
     *     <li>and each object replaced by {@link #resolveObject resolveObject}
     *         is filtered using the replacement object's class, if not {@code null},
     *         and if it is an array, the arrayLength, otherwise -1.
     * </ul>
     *
     * When the {@link ObjectInputFilter#checkInput checkInput} method is invoked
     * it is given access to the current class, the array length,
     * the current number of references already read from the stream,
     * the depth of nested calls to {@link #readObject readObject} or
     * {@link #readUnshared readUnshared},
     * and the implementation dependent number of bytes consumed from the input stream.
     * <p>
     * Each call to {@link #readObject readObject} or
     * {@link #readUnshared readUnshared} increases the depth by 1
     * before reading an object and decreases by 1 before returning
     * normally or exceptionally.
     * The depth starts at {@code 1} and increases for each nested object and
     * decrements when each nested call returns.
     * The count of references in the stream starts at {@code 1} and
     * is increased before reading an object.
     *
     * @param filter the filter, may be null
     * @throws SecurityException if there is security manager and the
     *       {@code SerializablePermission("serialFilter")} is not granted
     * @throws IllegalStateException if the {@linkplain #getObjectInputFilter() current filter}
     *       is not {@code null} and is not the system-wide filter, or
     *       if an object has been read
     * @since 9
     */
    public final void setObjectInputFilter(ObjectInputFilter filter) {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkPermission(ObjectStreamConstants.SERIAL_FILTER_PERMISSION);
        }
        // Allow replacement of the system-wide filter if not already set
        if (serialFilter != null &&
                serialFilter != ObjectInputFilter.Config.getSerialFilter()) {
            throw new IllegalStateException("filter can not be set more than once");
        }
        if (totalObjectRefs > 0 && !Caches.SET_FILTER_AFTER_READ) {
            throw new IllegalStateException(
                    "filter can not be set after an object has been read");
        }
        this.serialFilter = filter;
    }

    
Invoke the serialization filter if non-null.
If the filter rejects or an exception is thrown, throws InvalidClassException.
Params:
clazz – the class; may be null
arrayLength – the array length requested; use -1 if not creating an array
Throws:
InvalidClassException – if it rejected by the filter or a RuntimeException is thrown/**
     * Invoke the serialization filter if non-null.
     * If the filter rejects or an exception is thrown, throws InvalidClassException.
     *
     * @param clazz the class; may be null
     * @param arrayLength the array length requested; use {@code -1} if not creating an array
     * @throws InvalidClassException if it rejected by the filter or
     *        a {@link RuntimeException} is thrown
     */
    private void filterCheck(Class<?> clazz, int arrayLength)
            throws InvalidClassException {
        if (serialFilter != null) {
            RuntimeException ex = null;
            ObjectInputFilter.Status status;
            // Info about the stream is not available if overridden by subclass, return 0
            long bytesRead = (bin == null) ? 0 : bin.getBytesRead();
            try {
                status = serialFilter.checkInput(new FilterValues(clazz, arrayLength,
                        totalObjectRefs, depth, bytesRead));
            } catch (RuntimeException e) {
                // Preventive interception of an exception to log
                status = ObjectInputFilter.Status.REJECTED;
                ex = e;
            }
            if (Logging.filterLogger != null) {
                // Debug logging of filter checks that fail; Tracing for those that succeed
                Logging.filterLogger.log(status == null || status == ObjectInputFilter.Status.REJECTED
                                ? Logger.Level.DEBUG
                                : Logger.Level.TRACE,
                        "ObjectInputFilter {0}: {1}, array length: {2}, nRefs: {3}, depth: {4}, bytes: {5}, ex: {6}",
                        status, clazz, arrayLength, totalObjectRefs, depth, bytesRead,
                        Objects.toString(ex, "n/a"));
            }
            if (status == null ||
                    status == ObjectInputFilter.Status.REJECTED) {
                InvalidClassException ice = new InvalidClassException("filter status: " + status);
                ice.initCause(ex);
                throw ice;
            }
        }
    }

    
Checks the given array type and length to ensure that creation of such
an array is permitted by this ObjectInputStream. The arrayType argument
must represent an actual array type.
This private method is called via SharedSecrets.
Params:
arrayType – the array type
arrayLength – the array length
Throws:
NullPointerException – if arrayType is null
IllegalArgumentException – if arrayType isn't actually an array type
NegativeArraySizeException – if arrayLength is negative
InvalidClassException – if the filter rejects creation/**
     * Checks the given array type and length to ensure that creation of such
     * an array is permitted by this ObjectInputStream. The arrayType argument
     * must represent an actual array type.
     *
     * This private method is called via SharedSecrets.
     *
     * @param arrayType the array type
     * @param arrayLength the array length
     * @throws NullPointerException if arrayType is null
     * @throws IllegalArgumentException if arrayType isn't actually an array type
     * @throws NegativeArraySizeException if arrayLength is negative
     * @throws InvalidClassException if the filter rejects creation
     */
    private void checkArray(Class<?> arrayType, int arrayLength) throws InvalidClassException {
        if (! arrayType.isArray()) {
            throw new IllegalArgumentException("not an array type");
        }

        if (arrayLength < 0) {
            throw new NegativeArraySizeException();
        }

        filterCheck(arrayType, arrayLength);
    }

    
Provide access to the persistent fields read from the input stream.
/**
     * Provide access to the persistent fields read from the input stream.
     */
    public abstract static class GetField {
        
Constructor for subclasses to call.
/**
         * Constructor for subclasses to call.
         */
        public GetField() {}

        
Get the ObjectStreamClass that describes the fields in the stream.
Returns:
 the descriptor class that describes the serializable fields/**
         * 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.
Params:
name – the name of the field
Throws:
IOException – if there are I/O errors while reading from the underlying InputStream
IllegalArgumentException – if name does not correspond to a serializable field
Returns:
true, if and only if the named field is defaulted/**
         * 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}
         * @throws IllegalArgumentException if {@code name} 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.
Params:
name – the name of the field
val – the default value to use if name does not have a value
Throws:
IOException – if there are I/O errors while reading from the underlying InputStream
IllegalArgumentException – if type of name is not serializable or if the field type is incorrect
Returns:
the value of the named boolean field/**
         * 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} does not
         *         have a value
         * @return the value of the named {@code boolean} field
         * @throws IOException if there are I/O errors while reading from the
         *         underlying {@code InputStream}
         * @throws IllegalArgumentException if type of {@code name} 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.
Params:
name – the name of the field
val – the default value to use if name does not have a value
Throws:
IOException – if there are I/O errors while reading from the underlying InputStream
IllegalArgumentException – if type of name is not serializable or if the field type is incorrect
Returns:
the value of the named byte field/**
         * 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} does not
         *         have a value
         * @return the value of the named {@code byte} field
         * @throws IOException if there are I/O errors while reading from the
         *         underlying {@code InputStream}
         * @throws IllegalArgumentException if type of {@code name} 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.
Params:
name – the name of the field
val – the default value to use if name does not have a value
Throws:
IOException – if there are I/O errors while reading from the underlying InputStream
IllegalArgumentException – if type of name is not serializable or if the field type is incorrect
Returns:
the value of the named char field/**
         * 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} does not
         *         have a value
         * @return the value of the named {@code char} field
         * @throws IOException if there are I/O errors while reading from the
         *         underlying {@code InputStream}
         * @throws IllegalArgumentException if type of {@code name} 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.
Params:
name – the name of the field
val – the default value to use if name does not have a value
Throws:
IOException – if there are I/O errors while reading from the underlying InputStream
IllegalArgumentException – if type of name is not serializable or if the field type is incorrect
Returns:
the value of the named short field/**
         * 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} does not
         *         have a value
         * @return the value of the named {@code short} field
         * @throws IOException if there are I/O errors while reading from the
         *         underlying {@code InputStream}
         * @throws IllegalArgumentException if type of {@code name} 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.
Params:
name – the name of the field
val – the default value to use if name does not have a value
Throws:
IOException – if there are I/O errors while reading from the underlying InputStream
IllegalArgumentException – if type of name is not serializable or if the field type is incorrect
Returns:
the value of the named int field/**
         * 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} does not
         *         have a value
         * @return the value of the named {@code int} field
         * @throws IOException if there are I/O errors while reading from the
         *         underlying {@code InputStream}
         * @throws IllegalArgumentException if type of {@code name} 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.
Params:
name – the name of the field
val – the default value to use if name does not have a value
Throws:
IOException – if there are I/O errors while reading from the underlying InputStream
IllegalArgumentException – if type of name is not serializable or if the field type is incorrect
Returns:
the value of the named long field/**
         * 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} does not
         *         have a value
         * @return the value of the named {@code long} field
         * @throws IOException if there are I/O errors while reading from the
         *         underlying {@code InputStream}
         * @throws IllegalArgumentException if type of {@code name} 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.
Params:
name – the name of the field
val – the default value to use if name does not have a value
Throws:
IOException – if there are I/O errors while reading from the underlying InputStream
IllegalArgumentException – if type of name is not serializable or if the field type is incorrect
Returns:
the value of the named float field/**
         * 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} does not
         *         have a value
         * @return the value of the named {@code float} field
         * @throws IOException if there are I/O errors while reading from the
         *         underlying {@code InputStream}
         * @throws IllegalArgumentException if type of {@code name} 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.
Params:
name – the name of the field
val – the default value to use if name does not have a value
Throws:
IOException – if there are I/O errors while reading from the underlying InputStream
IllegalArgumentException – if type of name is not serializable or if the field type is incorrect
Returns:
the value of the named double field/**
         * 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} does not
         *         have a value
         * @return the value of the named {@code double} field
         * @throws IOException if there are I/O errors while reading from the
         *         underlying {@code InputStream}
         * @throws IllegalArgumentException if type of {@code name} 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.
Params:
name – the name of the field
val – the default value to use if name does not have a value
Throws:
IOException – if there are I/O errors while reading from the underlying InputStream
IllegalArgumentException – if type of name is not serializable or if the field type is incorrect
Returns:
the value of the named Object field/**
         * 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} does not
         *         have a value
         * @return the value of the named {@code Object} field
         * @throws IOException if there are I/O errors while reading from the
         *         underlying {@code InputStream}
         * @throws IllegalArgumentException if type of {@code name} 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.
/**
     * 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 = auditSubclass(cl);
            Caches.subclassAudits.putIfAbsent(key, result);
        }
        if (!result) {
            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.
/**
     * 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(Class<?> subcl) {
        return 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;
                }
            }
        );
    }

    
Clears internal data structures.
/**
     * Clears internal data structures.
     */
    private void clear() {
        handles.clear();
        vlist.clear();
    }

    
Underlying readObject implementation.
Params:
type – a type expected to be deserialized; non-null
unshared – true if the object can not be a reference to a shared object, otherwise false/**
     * Underlying readObject implementation.
     * @param type a type expected to be deserialized; non-null
     * @param unshared true if the object can not be a reference to a shared object, otherwise false
     */
    private Object readObject0(Class<?> type, 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++;
        totalObjectRefs++;
        try {
            switch (tc) {
                case TC_NULL:
                    return readNull();

                case TC_REFERENCE:
                    // check the type of the existing object
                    return type.cast(readHandle(unshared));

                case TC_CLASS:
                    if (type == String.class) {
                        throw new ClassCastException("Cannot cast a class to java.lang.String");
                    }
                    return readClass(unshared);

                case TC_CLASSDESC:
                case TC_PROXYCLASSDESC:
                    if (type == String.class) {
                        throw new ClassCastException("Cannot cast a class to java.lang.String");
                    }
                    return readClassDesc(unshared);

                case TC_STRING:
                case TC_LONGSTRING:
                    return checkResolve(readString(unshared));

                case TC_ARRAY:
                    if (type == String.class) {
                        throw new ClassCastException("Cannot cast an array to java.lang.String");
                    }
                    return checkResolve(readArray(unshared));

                case TC_ENUM:
                    if (type == String.class) {
                        throw new ClassCastException("Cannot cast an enum to java.lang.String");
                    }
                    return checkResolve(readEnum(unshared));

                case TC_OBJECT:
                    if (type == String.class) {
                        throw new ClassCastException("Cannot cast an object to java.lang.String");
                    }
                    return checkResolve(readOrdinaryObject(unshared));

                case TC_EXCEPTION:
                    if (type == String.class) {
                        throw new ClassCastException("Cannot cast an exception to java.lang.String");
                    }
                    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.
/**
     * 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) {
            // The type of the original object has been filtered but resolveObject
            // may have replaced it;  filter the replacement's type
            if (rep != null) {
                if (rep.getClass().isArray()) {
                    filterCheck(rep.getClass(), Array.getLength(rep));
                } else {
                    filterCheck(rep.getClass(), -1);
                }
            }
            handles.setObject(passHandle, rep);
        }
        return rep;
    }

    
Reads string without allowing it to be replaced in stream.  Called from
within ObjectStreamClass.read().
/**
     * 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.
/**
     * 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.
/**
     * 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");
        }
        filterCheck(null, -1);       // just a check for number of references, depth, no class
        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).
/**
     * 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.
/**
     * 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();
        ObjectStreamClass descriptor;
        switch (tc) {
            case TC_NULL:
                descriptor = (ObjectStreamClass) readNull();
                break;
            case TC_REFERENCE:
                descriptor = (ObjectStreamClass) readHandle(unshared);
                // Should only reference initialized class descriptors
                descriptor.checkInitialized();
                break;
            case TC_PROXYCLASSDESC:
                descriptor = readProxyDesc(unshared);
                break;
            case TC_CLASSDESC:
                descriptor = readNonProxyDesc(unshared);
                break;
            default:
                throw new StreamCorruptedException(
                    String.format("invalid type code: %02X", tc));
        }
        return descriptor;
    }

    private boolean isCustomSubclass() {
        // Return true if this class is a custom subclass of ObjectInputStream
        return getClass().getClassLoader()
                    != ObjectInputStream.class.getClassLoader();
    }

    
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.
/**
     * 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();
        if (numIfaces > 65535) {
            throw new InvalidObjectException("interface limit exceeded: "
                    + numIfaces);
        }
        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");
            } else if (!Proxy.isProxyClass(cl)) {
                throw new InvalidClassException("Not a proxy");
            } else {
                // ReflectUtil.checkProxyPackageAccess makes a test
                // equivalent to isCustomSubclass so there's no need
                // to condition this call to isCustomSubclass == true here.
                ReflectUtil.checkProxyPackageAccess(
                        getClass().getClassLoader(),
                        cl.getInterfaces());
                // Filter the interfaces
                for (Class<?> clazz : cl.getInterfaces()) {
                    filterCheck(clazz, -1);
                }
            }
        } catch (ClassNotFoundException ex) {
            resolveEx = ex;
        }

        // Call filterCheck on the class before reading anything else
        filterCheck(cl, -1);

        skipCustomData();

        try {
            totalObjectRefs++;
            depth++;
            desc.initProxy(cl, resolveEx, readClassDesc(false));
        } finally {
            depth--;
        }

        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.
/**
     * 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;
        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);
        final boolean checksRequired = isCustomSubclass();
        try {
            if ((cl = resolveClass(readDesc)) == null) {
                resolveEx = new ClassNotFoundException("null class");
            } else if (checksRequired) {
                ReflectUtil.checkPackageAccess(cl);
            }
        } catch (ClassNotFoundException ex) {
            resolveEx = ex;
        }

        // Call filterCheck on the class before reading anything else
        filterCheck(cl, -1);

        skipCustomData();

        try {
            totalObjectRefs++;
            depth++;
            desc.initNonProxy(readDesc, cl, resolveEx, readClassDesc(false));
        } finally {
            depth--;
        }

        handles.finish(descHandle);
        passHandle = descHandle;

        return desc;
    }

    
Reads in and returns new string.  Sets passHandle to new string's
assigned handle.
/**
     * 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.
/**
     * 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();

        filterCheck(desc.forClass(), len);

        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(Object.class, 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(Object.class, 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.
/**
     * 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<?> result = null;
        Class<?> cl = desc.forClass();
        if (cl != null) {
            try {
                @SuppressWarnings("unchecked")
                Enum<?> en = Enum.valueOf((Class)cl, name);
                result = en;
            } catch (IllegalArgumentException ex) {
                throw (IOException) new InvalidObjectException(
                    "enum constant " + name + " does not exist in " +
                    cl).initCause(ex);
            }
            if (!unshared) {
                handles.setObject(enumHandle, result);
            }
        }

        handles.finish(enumHandle);
        passHandle = enumHandle;
        return result;
    }

    
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.
/**
     * 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();

        Class<?> cl = desc.forClass();
        if (cl == String.class || cl == Class.class
                || cl == ObjectStreamClass.class) {
            throw new InvalidClassException("invalid class descriptor");
        }

        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);
        }

        final boolean isRecord = desc.isRecord();
        if (isRecord) {
            assert obj == null;
            obj = readRecord(desc);
            if (!unshared)
                handles.setObject(passHandle, obj);
        } else 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) {
                // Filter the replacement object
                if (rep != null) {
                    if (rep.getClass().isArray()) {
                        filterCheck(rep.getClass(), Array.getLength(rep));
                    } else {
                        filterCheck(rep.getClass(), -1);
                    }
                }
                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.
/**
     * 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;
        if (oldContext != null)
            oldContext.check();
        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 {
            if (oldContext != null)
                oldContext.check();
            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 a record. /** Reads a record. */
    private Object readRecord(ObjectStreamClass desc) throws IOException {
        ObjectStreamClass.ClassDataSlot[] slots = desc.getClassDataLayout();
        if (slots.length != 1) {
            // skip any superclass stream field values
            for (int i = 0; i < slots.length-1; i++) {
                ObjectStreamClass slotDesc = slots[i].desc;
                if (slots[i].hasData) {
                    defaultReadFields(null, slotDesc);
                }
            }
        }

        FieldValues fieldValues = defaultReadFields(null, desc);

        // get canonical record constructor adapted to take two arguments:
        // - byte[] primValues
        // - Object[] objValues
        // and return Object
        MethodHandle ctrMH = RecordSupport.deserializationCtr(desc);

        try {
            return (Object) ctrMH.invokeExact(fieldValues.primValues, fieldValues.objValues);
        } catch (Exception e) {
            InvalidObjectException ioe = new InvalidObjectException(e.getMessage());
            ioe.initCause(e);
            throw ioe;
        } catch (Error e) {
            throw e;
        } catch (Throwable t) {
            ObjectStreamException ose = new InvalidObjectException(
                    "ReflectiveOperationException during deserialization");
            ose.initCause(t);
            throw ose;
        }
    }

    
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.
/**
     * 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();
        // Best effort Failure Atomicity; slotValues will be non-null if field
        // values can be set after reading all field data in the hierarchy.
        // Field values can only be set after reading all data if there are no
        // user observable methods in the hierarchy, readObject(NoData). The
        // top most Serializable class in the hierarchy can be skipped.
        FieldValues[] slotValues = null;

        boolean hasSpecialReadMethod = false;
        for (int i = 1; i < slots.length; i++) {
            ObjectStreamClass slotDesc = slots[i].desc;
            if (slotDesc.hasReadObjectMethod()
                  || slotDesc.hasReadObjectNoDataMethod()) {
                hasSpecialReadMethod = true;
                break;
            }
        }
        // No special read methods, can store values and defer setting.
        if (!hasSpecialReadMethod)
            slotValues = new FieldValues[slots.length];

        for (int i = 0; i < slots.length; i++) {
            ObjectStreamClass slotDesc = slots[i].desc;

            if (slots[i].hasData) {
                if (obj == null || handles.lookupException(passHandle) != null) {
                    defaultReadFields(null, slotDesc); // skip field values
                } else if (slotDesc.hasReadObjectMethod()) {
                    ThreadDeath t = null;
                    boolean reset = false;
                    SerialCallbackContext oldContext = curContext;
                    if (oldContext != null)
                        oldContext.check();
                    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 {
                        do {
                            try {
                                curContext.setUsed();
                                if (oldContext!= null)
                                    oldContext.check();
                                curContext = oldContext;
                                reset = true;
                            } catch (ThreadDeath x) {
                                t = x;  // defer until reset is true
                            }
                        } while (!reset);
                        if (t != null)
                            throw t;
                    }

                    /*
                     * 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 {
                    FieldValues vals = defaultReadFields(obj, slotDesc);
                    if (slotValues != null) {
                        slotValues[i] = vals;
                    } else if (obj != null) {
                        defaultCheckFieldValues(obj, slotDesc, vals);
                        defaultSetFieldValues(obj, slotDesc, vals);
                    }
                }

                if (slotDesc.hasWriteObjectData()) {
                    skipCustomData();
                } else {
                    bin.setBlockDataMode(false);
                }
            } else {
                if (obj != null &&
                    slotDesc.hasReadObjectNoDataMethod() &&
                    handles.lookupException(passHandle) == null)
                {
                    slotDesc.invokeReadObjectNoData(obj);
                }
            }
        }

        if (obj != null && slotValues != null) {
            // Check that the non-primitive types are assignable for all slots
            // before assigning.
            for (int i = 0; i < slots.length; i++) {
                if (slotValues[i] != null)
                    defaultCheckFieldValues(obj, slots[i].desc, slotValues[i]);
            }
            for (int i = 0; i < slots.length; i++) {
                if (slotValues[i] != null)
                    defaultSetFieldValues(obj, slots[i].desc, slotValues[i]);
            }
        }
    }

    
Skips over all block data and objects until TC_ENDBLOCKDATA is
encountered.
/**
     * 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(Object.class, false);
                    break;
            }
        }
    }

    /*package-private*/ class FieldValues {
        final byte[] primValues;
        final Object[] objValues;

        FieldValues(byte[] primValues, Object[] objValues) {
            this.primValues = primValues;
            this.objValues = objValues;
        }
    }

    
Reads in values of serializable fields declared by given class
descriptor. Expects that passHandle is set to obj's handle before this
method is called.
/**
     * Reads in values of serializable fields declared by given class
     * descriptor. Expects that passHandle is set to obj's handle before this
     * method is called.
     */
    private FieldValues defaultReadFields(Object obj, ObjectStreamClass desc)
        throws IOException
    {
        Class<?> cl = desc.forClass();
        if (cl != null && obj != null && !cl.isInstance(obj)) {
            throw new ClassCastException();
        }

        byte[] primVals = null;
        int primDataSize = desc.getPrimDataSize();
        if (primDataSize > 0) {
            primVals = new byte[primDataSize];
            bin.readFully(primVals, 0, primDataSize, false);
        }

        Object[] objVals = null;
        int numObjFields = desc.getNumObjFields();
        if (numObjFields > 0) {
            int objHandle = passHandle;
            ObjectStreamField[] fields = desc.getFields(false);
            objVals = new Object[numObjFields];
            int numPrimFields = fields.length - objVals.length;
            for (int i = 0; i < objVals.length; i++) {
                ObjectStreamField f = fields[numPrimFields + i];
                objVals[i] = readObject0(Object.class, f.isUnshared());
                if (f.getField() != null) {
                    handles.markDependency(objHandle, passHandle);
                }
            }
            passHandle = objHandle;
        }

        return new FieldValues(primVals, objVals);
    }

    
Throws ClassCastException if any value is not assignable. /** Throws ClassCastException if any value is not assignable. */
    private void defaultCheckFieldValues(Object obj, ObjectStreamClass desc,
                                         FieldValues values) {
        Object[] objectValues = values.objValues;
        if (objectValues != null)
            desc.checkObjFieldValueTypes(obj, objectValues);
    }

    
Sets field values in obj. /** Sets field values in obj. */
    private void defaultSetFieldValues(Object obj, ObjectStreamClass desc,
                                       FieldValues values) {
        byte[] primValues = values.primValues;
        Object[] objectValues = values.objValues;

        if (primValues != null)
            desc.setPrimFieldValues(obj, primValues);
        if (objectValues != null)
            desc.setObjFieldValues(obj, objectValues);
    }

    
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.
/**
     * 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(Object.class, 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.
/**
     * 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();
    }

    
Returns the first non-null and non-platform class loader (not counting
class loaders of generated reflection implementation classes) up the
execution stack, or the platform class loader if only code from the
bootstrap and platform class loader is on the stack.
/**
     * Returns the first non-null and non-platform class loader (not counting
     * class loaders of generated reflection implementation classes) up the
     * execution stack, or the platform class loader if only code from the
     * bootstrap and platform class loader is on the stack.
     */
    private static ClassLoader latestUserDefinedLoader() {
        return jdk.internal.misc.VM.latestUserDefinedLoader();
    }

    
Default GetField implementation.
/**
     * Default GetField implementation.
     */
    private class GetFieldImpl extends GetField {

        
class descriptor describing serializable fields /** class descriptor describing serializable fields */
        private final ObjectStreamClass desc;
        
primitive field values /** primitive field values */
        private final byte[] primVals;
        
object field values /** object field values */
        private final Object[] objVals;
        
object field value handles /** object field value handles */
        private final int[] objHandles;

        
Creates GetFieldImpl object for reading fields defined in given
class descriptor.
/**
         * 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.
/**
         * 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(Object.class, 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.
/**
         * 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.
/**
     * 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 /** linked list of callbacks */
        private Callback list;

        
Creates new (empty) ValidationList.
/**
         * Creates new (empty) ValidationList.
         */
        ValidationList() {
        }

        
Registers callback.  Throws InvalidObjectException if callback
object is null.
/**
         * 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.
/**
         * 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.
/**
         * Resets the callback list to its initial (empty) state.
         */
        public void clear() {
            list = null;
        }
    }

    
Hold a snapshot of values to be passed to an ObjectInputFilter.
/**
     * Hold a snapshot of values to be passed to an ObjectInputFilter.
     */
    static class FilterValues implements ObjectInputFilter.FilterInfo {
        final Class<?> clazz;
        final long arrayLength;
        final long totalObjectRefs;
        final long depth;
        final long streamBytes;

        public FilterValues(Class<?> clazz, long arrayLength, long totalObjectRefs,
                            long depth, long streamBytes) {
            this.clazz = clazz;
            this.arrayLength = arrayLength;
            this.totalObjectRefs = totalObjectRefs;
            this.depth = depth;
            this.streamBytes = streamBytes;
        }

        @Override
        public Class<?> serialClass() {
            return clazz;
        }

        @Override
        public long arrayLength() {
            return arrayLength;
        }

        @Override
        public long references() {
            return totalObjectRefs;
        }

        @Override
        public long depth() {
            return depth;
        }

        @Override
        public long streamBytes() {
            return streamBytes;
        }
    }

    
Input stream supporting single-byte peek operations.
/**
     * Input stream supporting single-byte peek operations.
     */
    private static class PeekInputStream extends InputStream {

        
underlying stream /** underlying stream */
        private final InputStream in;
        
peeked byte /** peeked byte */
        private int peekb = -1;
        
total bytes read from the stream /** total bytes read from the stream */
        private long totalBytesRead = 0;

        
Creates new PeekInputStream on top of given underlying stream.
/**
         * 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.
/**
         * Peeks at next byte value in stream.  Similar to read(), except
         * that it does not consume the read value.
         */
        int peek() throws IOException {
            if (peekb >= 0) {
                return peekb;
            }
            peekb = in.read();
            totalBytesRead += peekb >= 0 ? 1 : 0;
            return peekb;
        }

        public int read() throws IOException {
            if (peekb >= 0) {
                int v = peekb;
                peekb = -1;
                return v;
            } else {
                int nbytes = in.read();
                totalBytesRead += nbytes >= 0 ? 1 : 0;
                return nbytes;
            }
        }

        public int read(byte[] b, int off, int len) throws IOException {
            int nbytes;
            if (len == 0) {
                return 0;
            } else if (peekb < 0) {
                nbytes = in.read(b, off, len);
                totalBytesRead += nbytes >= 0 ? nbytes : 0;
                return nbytes;
            } else {
                b[off++] = (byte) peekb;
                len--;
                peekb = -1;
                nbytes = in.read(b, off, len);
                totalBytesRead += nbytes >= 0 ? nbytes : 0;
                return (nbytes >= 0) ? (nbytes + 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--;
            }
            n = skipped + in.skip(n);
            totalBytesRead += n;
            return n;
        }

        public int available() throws IOException {
            return in.available() + ((peekb >= 0) ? 1 : 0);
        }

        public void close() throws IOException {
            in.close();
        }

        public long getBytesRead() {
            return totalBytesRead;
        }
    }

    private static final Unsafe UNSAFE = Unsafe.getUnsafe();

    
Performs a "freeze" action, required to adhere to final field semantics.
 This method can be called unconditionally before returning the graph,
from the topmost readObject call, since it is expected that the
additional cost of the freeze action is negligible compared to
reconstituting even the most simple graph.
 Nested calls to readObject do not issue freeze actions because the
sub-graph returned from a nested call is not guaranteed to be fully
initialized yet (possible cycles).
/**
     * Performs a "freeze" action, required to adhere to final field semantics.
     *
     * <p> This method can be called unconditionally before returning the graph,
     * from the topmost readObject call, since it is expected that the
     * additional cost of the freeze action is negligible compared to
     * reconstituting even the most simple graph.
     *
     * <p> Nested calls to readObject do not issue freeze actions because the
     * sub-graph returned from a nested call is not guaranteed to be fully
     * initialized yet (possible cycles).
     */
    private void freeze() {
        // Issue a StoreStore|StoreLoad fence, which is at least sufficient
        // to provide final-freeze semantics.
        UNSAFE.storeFence();
    }

    
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).
/**
     * 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 /** maximum data block length */
        private static final int MAX_BLOCK_SIZE = 1024;
        
maximum data block header length /** maximum data block header length */
        private static final int MAX_HEADER_SIZE = 5;
        
(tunable) length of char buffer (for reading strings) /** (tunable) length of char buffer (for reading strings) */
        private static final int CHAR_BUF_SIZE = 256;
        
readBlockHeader() return value indicating header read may block /** readBlockHeader() return value indicating header read may block */
        private static final int HEADER_BLOCKED = -2;

        
buffer for reading general/block data /** buffer for reading general/block data */
        private final byte[] buf = new byte[MAX_BLOCK_SIZE];
        
buffer for reading block data headers /** buffer for reading block data headers */
        private final byte[] hbuf = new byte[MAX_HEADER_SIZE];
        
char buffer for fast string reads /** char buffer for fast string reads */
        private final char[] cbuf = new char[CHAR_BUF_SIZE];

        
block data mode /** block data mode */
        private boolean blkmode = false;

        // block data state fields; values meaningful only when blkmode true
        
current offset into buf /** current offset into buf */
        private int pos = 0;
        
end offset of valid data in buf, or -1 if no more block data /** 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 /** number of bytes in current block yet to be read from stream */
        private int unread = 0;

        
underlying stream (wrapped in peekable filter stream) /** underlying stream (wrapped in peekable filter stream) */
        private final PeekInputStream in;
        
loopback stream (for data reads that span data blocks) /** 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.
/**
         * 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.
/**
         * 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.
/**
         * 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.
/**
         * 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.
/**
         * 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.
/**
         * 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.
/**
         * 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.
/**
         * 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.
/**
         * 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).
/**
         * 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());
        }

        @SuppressWarnings("deprecation")
        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 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.readFloat();
                    continue;
                } else {
                    stop = Math.min(endoff, ((end - pos) >> 2));
                }

                while (off < stop) {
                    v[off++] = Bits.getFloat(buf, pos);
                    pos += 4;
                }
            }
        }

        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 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.readDouble();
                    continue;
                } else {
                    stop = Math.min(endoff - off, ((end - pos) >> 3));
                }

                while (off < stop) {
                    v[off++] = Bits.getDouble(buf, pos);
                    pos += 8;
                }
            }
        }

        
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.
/**
         * 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.
/**
         * 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;
            if (utflen > 0 && utflen < Integer.MAX_VALUE) {
                // a reasonable initial capacity based on the UTF length
                int initialCapacity = Math.min((int)utflen, 0xFFFF);
                sbuf = new StringBuilder(initialCapacity);
            } else {
                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.
/**
         * 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.
/**
         * 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();
            }
        }

        
Returns the number of bytes read from the input stream.
Returns:
the number of bytes read from the input stream/**
         * Returns the number of bytes read from the input stream.
         * @return the number of bytes read from the input stream
         */
        long getBytesRead() {
            return in.getBytesRead();
        }
    }

    
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.
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.
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.
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.
/**
     * 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 /** array mapping handle -> object status */
        byte[] status;
        
array mapping handle -> object/exception (depending on status) /** array mapping handle -> object/exception (depending on status) */
        Object[] entries;
        
array mapping handle -> list of dependent handles (if any) /** array mapping handle -> list of dependent handles (if any) */
        HandleList[] deps;
        
lowest unresolved dependency /** lowest unresolved dependency */
        int lowDep = -1;
        
number of handles in table /** number of handles in table */
        int size = 0;

        
Creates handle table with the given initial capacity.
/**
         * 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().
/**
         * 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. Additionally, no action is taken if the
dependent and target are the same.
/**
         * 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. Additionally, no action is taken if the
         * dependent and target are the same.
         */
        void markDependency(int dependent, int target) {
            if (dependent == target || 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).
/**
         * 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.
/**
         * 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.
/**
         * 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.
/**
         * 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.
/**
         * 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.
/**
         * 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.
/**
         * Returns number of handles registered in table.
         */
        int size() {
            return size;
        }

        
Expands capacity of internal arrays.
/**
         * 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.
/**
         * 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
/**
     * 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();
        }
    }

    static {
        SharedSecrets.setJavaObjectInputStreamAccess(ObjectInputStream::checkArray);
        SharedSecrets.setJavaObjectInputStreamReadString(ObjectInputStream::readString);
    }

}