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Java Source Code / Java Documentation  » 6.0 JDK Core » io nio » java.io 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


        /*
         * Copyright 1996-2006 Sun Microsystems, Inc.  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.  Sun designates this
         * particular file as subject to the "Classpath" exception as provided
         * by Sun in the LICENSE file that accompanied this code.
         *
         * This code is distributed in the hope that it will be useful, but WITHOUT
         * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
         * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
         * version 2 for more details (a copy is included in the LICENSE file that
         * accompanied this code).
         *
         * You should have received a copy of the GNU General Public License version
         * 2 along with this work; if not, write to the Free Software Foundation,
         * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
         *
         * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
         * CA 95054 USA or visit www.sun.com if you need additional information or
         * have any questions.
         */

        package java.io;

        import java.lang.ref.Reference;
        import java.lang.ref.ReferenceQueue;
        import java.lang.ref.SoftReference;
        import java.lang.ref.WeakReference;
        import java.lang.reflect.Constructor;
        import java.lang.reflect.Field;
        import java.lang.reflect.InvocationTargetException;
        import java.lang.reflect.Member;
        import java.lang.reflect.Method;
        import java.lang.reflect.Modifier;
        import java.lang.reflect.Proxy;
        import java.security.AccessController;
        import java.security.MessageDigest;
        import java.security.NoSuchAlgorithmException;
        import java.security.PrivilegedAction;
        import java.util.ArrayList;
        import java.util.Arrays;
        import java.util.Collections;
        import java.util.Comparator;
        import java.util.HashSet;
        import java.util.Set;
        import java.util.concurrent.ConcurrentHashMap;
        import java.util.concurrent.ConcurrentMap;
        import sun.misc.Unsafe;
        import sun.reflect.ReflectionFactory;

        /**
         * Serialization's descriptor for classes.  It contains the name and
         * serialVersionUID of the class.  The ObjectStreamClass for a specific class
         * loaded in this Java VM can be found/created using the lookup method.
         * 
         * <p>The algorithm to compute the SerialVersionUID is described in 
         * <a href="../../../platform/serialization/spec/class.html#4100">Object
         * Serialization Specification, Section 4.6, Stream Unique Identifiers</a>.
         *
         * @author	Mike Warres
         * @author	Roger Riggs
         * @version 1.158, 05/05/07
         * @see ObjectStreamField
         * @see <a href="../../../platform/serialization/spec/class.html">Object Serialization Specification, Section 4, Class Descriptors</a>
         * @since   JDK1.1
         */
        public class ObjectStreamClass implements  Serializable {

            /** serialPersistentFields value indicating no serializable fields */
            public static final ObjectStreamField[] NO_FIELDS = new ObjectStreamField[0];

            private static final long serialVersionUID = -6120832682080437368L;
            private static final ObjectStreamField[] serialPersistentFields = NO_FIELDS;

            /** reflection factory for obtaining serialization constructors */
            private static final ReflectionFactory reflFactory = (ReflectionFactory) AccessController
                    .doPrivileged(new ReflectionFactory.GetReflectionFactoryAction());

            private static class Caches {
                /** cache mapping local classes -> descriptors */
                static final ConcurrentMap<WeakClassKey, Reference<?>> localDescs = new ConcurrentHashMap<WeakClassKey, Reference<?>>();

                /** cache mapping field group/local desc pairs -> field reflectors */
                static final ConcurrentMap<FieldReflectorKey, Reference<?>> reflectors = new ConcurrentHashMap<FieldReflectorKey, Reference<?>>();

                /** queue for WeakReferences to local classes */
                private static final ReferenceQueue<Class<?>> localDescsQueue = new ReferenceQueue<Class<?>>();
                /** queue for WeakReferences to field reflectors keys */
                private static final ReferenceQueue<Class<?>> reflectorsQueue = new ReferenceQueue<Class<?>>();
            }

            /** class associated with this descriptor (if any) */
            private Class cl;
            /** name of class represented by this descriptor */
            private String name;
            /** serialVersionUID of represented class (null if not computed yet) */
            private volatile Long suid;

            /** true if represents dynamic proxy class */
            private boolean isProxy;
            /** true if represents enum type */
            private boolean isEnum;
            /** true if represented class implements Serializable */
            private boolean serializable;
            /** true if represented class implements Externalizable */
            private boolean externalizable;
            /** true if desc has data written by class-defined writeObject method */
            private boolean hasWriteObjectData;
            /** 
             * true if desc has externalizable data written in block data format; this
             * must be true by default to accommodate ObjectInputStream subclasses which
             * override readClassDescriptor() to return class descriptors obtained from
             * ObjectStreamClass.lookup() (see 4461737)
             */
            private boolean hasBlockExternalData = true;

            /** exception (if any) thrown while attempting to resolve class */
            private ClassNotFoundException resolveEx;
            /** exception (if any) to throw if non-enum deserialization attempted */
            private InvalidClassException deserializeEx;
            /** exception (if any) to throw if non-enum serialization attempted */
            private InvalidClassException serializeEx;
            /** exception (if any) to throw if default serialization attempted */
            private InvalidClassException defaultSerializeEx;

            /** serializable fields */
            private ObjectStreamField[] fields;
            /** aggregate marshalled size of primitive fields */
            private int primDataSize;
            /** number of non-primitive fields */
            private int numObjFields;
            /** reflector for setting/getting serializable field values */
            private FieldReflector fieldRefl;
            /** data layout of serialized objects described by this class desc */
            private volatile ClassDataSlot[] dataLayout;

            /** serialization-appropriate constructor, or null if none */
            private Constructor cons;
            /** class-defined writeObject method, or null if none */
            private Method writeObjectMethod;
            /** class-defined readObject method, or null if none */
            private Method readObjectMethod;
            /** class-defined readObjectNoData method, or null if none */
            private Method readObjectNoDataMethod;
            /** class-defined writeReplace method, or null if none */
            private Method writeReplaceMethod;
            /** class-defined readResolve method, or null if none */
            private Method readResolveMethod;

            /** local class descriptor for represented class (may point to self) */
            private ObjectStreamClass localDesc;
            /** superclass descriptor appearing in stream */
            private ObjectStreamClass super Desc;

            /**
             * Initializes native code.
             */
            private static native void initNative();

            static {
                initNative();
            }

            /** 
             * Find the descriptor for a class that can be serialized.  Creates an
             * ObjectStreamClass instance if one does not exist yet for class. Null is
             * returned if the specified class does not implement java.io.Serializable
             * or java.io.Externalizable.
             *
             * @param	cl class for which to get the descriptor
             * @return	the class descriptor for the specified class
             */
            public static ObjectStreamClass lookup(Class<?> cl) {
                return lookup(cl, false);
            }

            /**
             * Returns the descriptor for any class, regardless of whether it
             * implements {@link Serializable}.
             *
             * @param        cl class for which to get the descriptor
             * @return       the class descriptor for the specified class
             * @since 1.6
             */
            public static ObjectStreamClass lookupAny(Class<?> cl) {
                return lookup(cl, true);
            }

            /**
             * Returns the name of the class described by this descriptor.
             * This method returns the name of the class in the format that
             * is used by the {@link Class#getName} method.
             *
             * @return a string representing the name of the class
             */
            public String getName() {
                return name;
            }

            /**
             * Return the serialVersionUID for this class.  The serialVersionUID
             * defines a set of classes all with the same name that have evolved from a
             * common root class and agree to be serialized and deserialized using a
             * common format.  NonSerializable classes have a serialVersionUID of 0L.
             *
             * @return	the SUID of the class described by this descriptor
             */
            public long getSerialVersionUID() {
                // REMIND: synchronize instead of relying on volatile?
                if (suid == null) {
                    suid = (Long) AccessController
                            .doPrivileged(new PrivilegedAction() {
                                public Object run() {
                                    return Long.valueOf(computeDefaultSUID(cl));
                                }
                            });
                }
                return suid.longValue();
            }

            /**
             * Return the class in the local VM that this version is mapped to.  Null
             * is returned if there is no corresponding local class.
             *
             * @return	the <code>Class</code> instance that this descriptor represents
             */
            public Class<?> forClass() {
                return cl;
            }

            /**
             * Return an array of the fields of this serializable class.
             *
             * @return	an array containing an element for each persistent field of
             * 		this class. Returns an array of length zero if there are no
             * 		fields.
             * @since 1.2
             */
            public ObjectStreamField[] getFields() {
                return getFields(true);
            }

            /**
             * Get the field of this class by name.
             *
             * @param	name the name of the data field to look for
             * @return	The ObjectStreamField object of the named field or null if
             * 		there is no such named field.
             */
            public ObjectStreamField getField(String name) {
                return getField(name, null);
            }

            /**
             * Return a string describing this ObjectStreamClass.
             */
            public String toString() {
                return name + ": static final long serialVersionUID = "
                        + getSerialVersionUID() + "L;";
            }

            /**
             * Looks up and returns class descriptor for given class, or null if class
             * is non-serializable and "all" is set to false.
             * 
             * @param	cl class to look up
             * @param	all if true, return descriptors for all classes; if false, only
             * 		return descriptors for serializable classes
             */
            static ObjectStreamClass lookup(Class cl, boolean all) {
                if (!(all || Serializable.class.isAssignableFrom(cl))) {
                    return null;
                }
                processQueue(Caches.localDescsQueue, Caches.localDescs);
                WeakClassKey key = new WeakClassKey(cl, Caches.localDescsQueue);
                Reference<?> ref = Caches.localDescs.get(key);
                Object entry = null;
                if (ref != null) {
                    entry = ref.get();
                }
                EntryFuture future = null;
                if (entry == null) {
                    EntryFuture newEntry = new EntryFuture();
                    Reference<?> newRef = new SoftReference<EntryFuture>(
                            newEntry);
                    do {
                        if (ref != null) {
                            Caches.localDescs.remove(key, ref);
                        }
                        ref = Caches.localDescs.putIfAbsent(key, newRef);
                        if (ref != null) {
                            entry = ref.get();
                        }
                    } while (ref != null && entry == null);
                    if (entry == null) {
                        future = newEntry;
                    }
                }

                if (entry instanceof  ObjectStreamClass) { // check common case first
                    return (ObjectStreamClass) entry;
                }
                if (entry instanceof  EntryFuture) {
                    future = (EntryFuture) entry;
                    if (future.getOwner() == Thread.currentThread()) {
                        /*
                         * Handle nested call situation described by 4803747: waiting
                         * for future value to be set by a lookup() call further up the
                         * stack will result in deadlock, so calculate and set the
                         * future value here instead.
                         */
                        entry = null;
                    } else {
                        entry = future.get();
                    }
                }
                if (entry == null) {
                    try {
                        entry = new ObjectStreamClass(cl);
                    } catch (Throwable th) {
                        entry = th;
                    }
                    if (future.set(entry)) {
                        Caches.localDescs.put(key, new SoftReference<Object>(
                                entry));
                    } else {
                        // nested lookup call already set future
                        entry = future.get();
                    }
                }

                if (entry instanceof  ObjectStreamClass) {
                    return (ObjectStreamClass) entry;
                } else if (entry instanceof  RuntimeException) {
                    throw (RuntimeException) entry;
                } else if (entry instanceof  Error) {
                    throw (Error) entry;
                } else {
                    throw new InternalError("unexpected entry: " + entry);
                }
            }

            /**
             * Placeholder used in class descriptor and field reflector lookup tables
             * for an entry in the process of being initialized.  (Internal) callers
             * which receive an EntryFuture belonging to another thread as the result
             * of a lookup should call the get() method of the EntryFuture; this will
             * return the actual entry once it is ready for use and has been set().  To
             * conserve objects, EntryFutures synchronize on themselves.
             */
            private static class EntryFuture {

                private static final Object unset = new Object();
                private final Thread owner = Thread.currentThread();
                private Object entry = unset;

                /**
                 * Attempts to set the value contained by this EntryFuture.  If the
                 * EntryFuture's value has not been set already, then the value is
                 * saved, any callers blocked in the get() method are notified, and
                 * true is returned.  If the value has already been set, then no saving
                 * or notification occurs, and false is returned.
                 */
                synchronized boolean set(Object entry) {
                    if (this .entry != unset) {
                        return false;
                    }
                    this .entry = entry;
                    notifyAll();
                    return true;
                }

                /**
                 * Returns the value contained by this EntryFuture, blocking if
                 * necessary until a value is set.
                 */
                synchronized Object get() {
                    boolean interrupted = false;
                    while (entry == unset) {
                        try {
                            wait();
                        } catch (InterruptedException ex) {
                            interrupted = true;
                        }
                    }
                    if (interrupted) {
                        AccessController.doPrivileged(new PrivilegedAction() {
                            public Object run() {
                                Thread.currentThread().interrupt();
                                return null;
                            }
                        });
                    }
                    return entry;
                }

                /**
                 * Returns the thread that created this EntryFuture.
                 */
                Thread getOwner() {
                    return owner;
                }
            }

            /**
             * Creates local class descriptor representing given class.
             */
            private ObjectStreamClass(final Class cl) {
                this .cl = cl;
                name = cl.getName();
                isProxy = Proxy.isProxyClass(cl);
                isEnum = Enum.class.isAssignableFrom(cl);
                serializable = Serializable.class.isAssignableFrom(cl);
                externalizable = Externalizable.class.isAssignableFrom(cl);

                Class super Cl = cl.getSuperclass();
                super Desc = (super Cl != null) ? lookup(super Cl, false) : null;
                localDesc = this ;

                if (serializable) {
                    AccessController.doPrivileged(new PrivilegedAction() {
                        public Object run() {
                            if (isEnum) {
                                suid = Long.valueOf(0);
                                fields = NO_FIELDS;
                                return null;
                            }
                            if (cl.isArray()) {
                                fields = NO_FIELDS;
                                return null;
                            }

                            suid = getDeclaredSUID(cl);
                            try {
                                fields = getSerialFields(cl);
                                computeFieldOffsets();
                            } catch (InvalidClassException e) {
                                serializeEx = deserializeEx = e;
                                fields = NO_FIELDS;
                            }

                            if (externalizable) {
                                cons = getExternalizableConstructor(cl);
                            } else {
                                cons = getSerializableConstructor(cl);
                                writeObjectMethod = getPrivateMethod(
                                        cl,
                                        "writeObject",
                                        new Class[] { ObjectOutputStream.class },
                                        Void.TYPE);
                                readObjectMethod = getPrivateMethod(
                                        cl,
                                        "readObject",
                                        new Class[] { ObjectInputStream.class },
                                        Void.TYPE);
                                readObjectNoDataMethod = getPrivateMethod(cl,
                                        "readObjectNoData", null, Void.TYPE);
                                hasWriteObjectData = (writeObjectMethod != null);
                            }
                            writeReplaceMethod = getInheritableMethod(cl,
                                    "writeReplace", null, Object.class);
                            readResolveMethod = getInheritableMethod(cl,
                                    "readResolve", null, Object.class);
                            return null;
                        }
                    });
                } else {
                    suid = Long.valueOf(0);
                    fields = NO_FIELDS;
                }

                try {
                    fieldRefl = getReflector(fields, this );
                } catch (InvalidClassException ex) {
                    // field mismatches impossible when matching local fields vs. self
                    throw new InternalError();
                }

                if (deserializeEx == null) {
                    if (isEnum) {
                        deserializeEx = new InvalidClassException(name,
                                "enum type");
                    } else if (cons == null) {
                        deserializeEx = new InvalidClassException(name,
                                "no valid constructor");
                    }
                }
                for (int i = 0; i < fields.length; i++) {
                    if (fields[i].getField() == null) {
                        defaultSerializeEx = new InvalidClassException(name,
                                "unmatched serializable field(s) declared");
                    }
                }
            }

            /**
             * Creates blank class descriptor which should be initialized via a
             * subsequent call to initProxy(), initNonProxy() or readNonProxy().
             */
            ObjectStreamClass() {
            }

            /**
             * Initializes class descriptor representing a proxy class.
             */
            void initProxy(Class cl, ClassNotFoundException resolveEx,
                    ObjectStreamClass super Desc) throws InvalidClassException {
                this .cl = cl;
                this .resolveEx = resolveEx;
                this .super Desc = super Desc;
                isProxy = true;
                serializable = true;
                suid = Long.valueOf(0);
                fields = NO_FIELDS;

                if (cl != null) {
                    localDesc = lookup(cl, true);
                    if (!localDesc.isProxy) {
                        throw new InvalidClassException(
                                "cannot bind proxy descriptor to a non-proxy class");
                    }
                    name = localDesc.name;
                    externalizable = localDesc.externalizable;
                    cons = localDesc.cons;
                    writeReplaceMethod = localDesc.writeReplaceMethod;
                    readResolveMethod = localDesc.readResolveMethod;
                    deserializeEx = localDesc.deserializeEx;
                }
                fieldRefl = getReflector(fields, localDesc);
            }

            /**
             * Initializes class descriptor representing a non-proxy class.
             */
            void initNonProxy(ObjectStreamClass model, Class cl,
                    ClassNotFoundException resolveEx,
                    ObjectStreamClass super Desc) throws InvalidClassException {
                this .cl = cl;
                this .resolveEx = resolveEx;
                this .super Desc = super Desc;
                name = model.name;
                suid = Long.valueOf(model.getSerialVersionUID());
                isProxy = false;
                isEnum = model.isEnum;
                serializable = model.serializable;
                externalizable = model.externalizable;
                hasBlockExternalData = model.hasBlockExternalData;
                hasWriteObjectData = model.hasWriteObjectData;
                fields = model.fields;
                primDataSize = model.primDataSize;
                numObjFields = model.numObjFields;

                if (cl != null) {
                    localDesc = lookup(cl, true);
                    if (localDesc.isProxy) {
                        throw new InvalidClassException(
                                "cannot bind non-proxy descriptor to a proxy class");
                    }
                    if (isEnum != localDesc.isEnum) {
                        throw new InvalidClassException(
                                isEnum ? "cannot bind enum descriptor to a non-enum class"
                                        : "cannot bind non-enum descriptor to an enum class");
                    }

                    if (serializable == localDesc.serializable
                            && !cl.isArray()
                            && suid.longValue() != localDesc
                                    .getSerialVersionUID()) {
                        throw new InvalidClassException(
                                localDesc.name,
                                "local class incompatible: "
                                        + "stream classdesc serialVersionUID = "
                                        + suid
                                        + ", local class serialVersionUID = "
                                        + localDesc.getSerialVersionUID());
                    }

                    if (!classNamesEqual(name, localDesc.name)) {
                        throw new InvalidClassException(localDesc.name,
                                "local class name incompatible with stream class "
                                        + "name \"" + name + "\"");
                    }

                    if (!isEnum) {
                        if ((serializable == localDesc.serializable)
                                && (externalizable != localDesc.externalizable)) {
                            throw new InvalidClassException(localDesc.name,
                                    "Serializable incompatible with Externalizable");
                        }

                        if ((serializable != localDesc.serializable)
                                || (externalizable != localDesc.externalizable)
                                || !(serializable || externalizable)) {
                            deserializeEx = new InvalidClassException(
                                    localDesc.name,
                                    "class invalid for deserialization");
                        }
                    }

                    cons = localDesc.cons;
                    writeObjectMethod = localDesc.writeObjectMethod;
                    readObjectMethod = localDesc.readObjectMethod;
                    readObjectNoDataMethod = localDesc.readObjectNoDataMethod;
                    writeReplaceMethod = localDesc.writeReplaceMethod;
                    readResolveMethod = localDesc.readResolveMethod;
                    if (deserializeEx == null) {
                        deserializeEx = localDesc.deserializeEx;
                    }
                }
                fieldRefl = getReflector(fields, localDesc);
                // reassign to matched fields so as to reflect local unshared settings
                fields = fieldRefl.getFields();
            }

            /**
             * Reads non-proxy class descriptor information from given input stream.
             * The resulting class descriptor is not fully functional; it can only be
             * used as input to the ObjectInputStream.resolveClass() and
             * ObjectStreamClass.initNonProxy() methods.
             */
            void readNonProxy(ObjectInputStream in) throws IOException,
                    ClassNotFoundException {
                name = in.readUTF();
                suid = Long.valueOf(in.readLong());
                isProxy = false;

                byte flags = in.readByte();
                hasWriteObjectData = ((flags & ObjectStreamConstants.SC_WRITE_METHOD) != 0);
                hasBlockExternalData = ((flags & ObjectStreamConstants.SC_BLOCK_DATA) != 0);
                externalizable = ((flags & ObjectStreamConstants.SC_EXTERNALIZABLE) != 0);
                boolean sflag = ((flags & ObjectStreamConstants.SC_SERIALIZABLE) != 0);
                if (externalizable && sflag) {
                    throw new InvalidClassException(name,
                            "serializable and externalizable flags conflict");
                }
                serializable = externalizable || sflag;
                isEnum = ((flags & ObjectStreamConstants.SC_ENUM) != 0);
                if (isEnum && suid.longValue() != 0L) {
                    throw new InvalidClassException(name,
                            "enum descriptor has non-zero serialVersionUID: "
                                    + suid);
                }

                int numFields = in.readShort();
                if (isEnum && numFields != 0) {
                    throw new InvalidClassException(name,
                            "enum descriptor has non-zero field count: "
                                    + numFields);
                }
                fields = (numFields > 0) ? new ObjectStreamField[numFields]
                        : NO_FIELDS;
                for (int i = 0; i < numFields; i++) {
                    char tcode = (char) in.readByte();
                    String fname = in.readUTF();
                    String signature = ((tcode == 'L') || (tcode == '[')) ? in
                            .readTypeString()
                            : new String(new char[] { tcode });
                    try {
                        fields[i] = new ObjectStreamField(fname, signature,
                                false);
                    } catch (RuntimeException e) {
                        throw (IOException) new InvalidClassException(name,
                                "invalid descriptor for field " + fname)
                                .initCause(e);
                    }
                }
                computeFieldOffsets();
            }

            /**
             * Writes non-proxy class descriptor information to given output stream.
             */
            void writeNonProxy(ObjectOutputStream out) throws IOException {
                out.writeUTF(name);
                out.writeLong(getSerialVersionUID());

                byte flags = 0;
                if (externalizable) {
                    flags |= ObjectStreamConstants.SC_EXTERNALIZABLE;
                    int protocol = out.getProtocolVersion();
                    if (protocol != ObjectStreamConstants.PROTOCOL_VERSION_1) {
                        flags |= ObjectStreamConstants.SC_BLOCK_DATA;
                    }
                } else if (serializable) {
                    flags |= ObjectStreamConstants.SC_SERIALIZABLE;
                }
                if (hasWriteObjectData) {
                    flags |= ObjectStreamConstants.SC_WRITE_METHOD;
                }
                if (isEnum) {
                    flags |= ObjectStreamConstants.SC_ENUM;
                }
                out.writeByte(flags);

                out.writeShort(fields.length);
                for (int i = 0; i < fields.length; i++) {
                    ObjectStreamField f = fields[i];
                    out.writeByte(f.getTypeCode());
                    out.writeUTF(f.getName());
                    if (!f.isPrimitive()) {
                        out.writeTypeString(f.getTypeString());
                    }
                }
            }

            /**
             * Returns ClassNotFoundException (if any) thrown while attempting to
             * resolve local class corresponding to this class descriptor.
             */
            ClassNotFoundException getResolveException() {
                return resolveEx;
            }

            /**
             * Throws an InvalidClassException if object instances referencing this
             * class descriptor should not be allowed to deserialize.  This method does
             * not apply to deserialization of enum constants.
             */
            void checkDeserialize() throws InvalidClassException {
                if (deserializeEx != null) {
                    InvalidClassException ice = new InvalidClassException(
                            deserializeEx.classname, deserializeEx.getMessage());
                    ice.initCause(deserializeEx);
                    throw ice;
                }
            }

            /**
             * Throws an InvalidClassException if objects whose class is represented by
             * this descriptor should not be allowed to serialize.  This method does
             * not apply to serialization of enum constants.
             */
            void checkSerialize() throws InvalidClassException {
                if (serializeEx != null) {
                    InvalidClassException ice = new InvalidClassException(
                            serializeEx.classname, serializeEx.getMessage());
                    ice.initCause(serializeEx);
                    throw ice;
                }
            }

            /**
             * Throws an InvalidClassException if objects whose class is represented by
             * this descriptor should not be permitted to use default serialization
             * (e.g., if the class declares serializable fields that do not correspond
             * to actual fields, and hence must use the GetField API).  This method
             * does not apply to deserialization of enum constants.
             */
            void checkDefaultSerialize() throws InvalidClassException {
                if (defaultSerializeEx != null) {
                    InvalidClassException ice = new InvalidClassException(
                            defaultSerializeEx.classname, defaultSerializeEx
                                    .getMessage());
                    ice.initCause(defaultSerializeEx);
                    throw ice;
                }
            }

            /**
             * Returns superclass descriptor.  Note that on the receiving side, the
             * superclass descriptor may be bound to a class that is not a superclass
             * of the subclass descriptor's bound class.
             */
            ObjectStreamClass getSuperDesc() {
                return super Desc;
            }

            /**
             * Returns the "local" class descriptor for the class associated with this
             * class descriptor (i.e., the result of
             * ObjectStreamClass.lookup(this.forClass())) or null if there is no class
             * associated with this descriptor.
             */
            ObjectStreamClass getLocalDesc() {
                return localDesc;
            }

            /**
             * Returns arrays of ObjectStreamFields representing the serializable
             * fields of the represented class.  If copy is true, a clone of this class
             * descriptor's field array is returned, otherwise the array itself is
             * returned.
             */
            ObjectStreamField[] getFields(boolean copy) {
                return copy ? (ObjectStreamField[]) fields.clone() : fields;
            }

            /**
             * Looks up a serializable field of the represented class by name and type.
             * A specified type of null matches all types, Object.class matches all
             * non-primitive types, and any other non-null type matches assignable
             * types only.  Returns matching field, or null if no match found.
             */
            ObjectStreamField getField(String name, Class type) {
                for (int i = 0; i < fields.length; i++) {
                    ObjectStreamField f = fields[i];
                    if (f.getName().equals(name)) {
                        if (type == null
                                || (type == Object.class && !f.isPrimitive())) {
                            return f;
                        }
                        Class ftype = f.getType();
                        if (ftype != null && type.isAssignableFrom(ftype)) {
                            return f;
                        }
                    }
                }
                return null;
            }

            /**
             * Returns true if class descriptor represents a dynamic proxy class, false
             * otherwise.
             */
            boolean isProxy() {
                return isProxy;
            }

            /**
             * Returns true if class descriptor represents an enum type, false
             * otherwise.
             */
            boolean isEnum() {
                return isEnum;
            }

            /**
             * Returns true if represented class implements Externalizable, false
             * otherwise.
             */
            boolean isExternalizable() {
                return externalizable;
            }

            /**
             * Returns true if represented class implements Serializable, false
             * otherwise.
             */
            boolean isSerializable() {
                return serializable;
            }

            /**
             * Returns true if class descriptor represents externalizable class that
             * has written its data in 1.2 (block data) format, false otherwise.
             */
            boolean hasBlockExternalData() {
                return hasBlockExternalData;
            }

            /**
             * Returns true if class descriptor represents serializable (but not
             * externalizable) class which has written its data via a custom
             * writeObject() method, false otherwise.
             */
            boolean hasWriteObjectData() {
                return hasWriteObjectData;
            }

            /**
             * Returns true if represented class is serializable/externalizable and can
             * be instantiated by the serialization runtime--i.e., if it is
             * externalizable and defines a public no-arg constructor, or if it is
             * non-externalizable and its first non-serializable superclass defines an
             * accessible no-arg constructor.  Otherwise, returns false.
             */
            boolean isInstantiable() {
                return (cons != null);
            }

            /**
             * Returns true if represented class is serializable (but not
             * externalizable) and defines a conformant writeObject method.  Otherwise,
             * returns false.
             */
            boolean hasWriteObjectMethod() {
                return (writeObjectMethod != null);
            }

            /**
             * Returns true if represented class is serializable (but not
             * externalizable) and defines a conformant readObject method.  Otherwise,
             * returns false.
             */
            boolean hasReadObjectMethod() {
                return (readObjectMethod != null);
            }

            /**
             * Returns true if represented class is serializable (but not
             * externalizable) and defines a conformant readObjectNoData method.
             * Otherwise, returns false.
             */
            boolean hasReadObjectNoDataMethod() {
                return (readObjectNoDataMethod != null);
            }

            /**
             * Returns true if represented class is serializable or externalizable and
             * defines a conformant writeReplace method.  Otherwise, returns false.
             */
            boolean hasWriteReplaceMethod() {
                return (writeReplaceMethod != null);
            }

            /**
             * Returns true if represented class is serializable or externalizable and
             * defines a conformant readResolve method.  Otherwise, returns false.
             */
            boolean hasReadResolveMethod() {
                return (readResolveMethod != null);
            }

            /**
             * Creates a new instance of the represented class.  If the class is
             * externalizable, invokes its public no-arg constructor; otherwise, if the
             * class is serializable, invokes the no-arg constructor of the first
             * non-serializable superclass.  Throws UnsupportedOperationException if
             * this class descriptor is not associated with a class, if the associated
             * class is non-serializable or if the appropriate no-arg constructor is
             * inaccessible/unavailable.
             */
            Object newInstance() throws InstantiationException,
                    InvocationTargetException, UnsupportedOperationException {
                if (cons != null) {
                    try {
                        return cons.newInstance();
                    } catch (IllegalAccessException ex) {
                        // should not occur, as access checks have been suppressed
                        throw new InternalError();
                    }
                } else {
                    throw new UnsupportedOperationException();
                }
            }

            /**
             * Invokes the writeObject method of the represented serializable class.
             * Throws UnsupportedOperationException if this class descriptor is not
             * associated with a class, or if the class is externalizable,
             * non-serializable or does not define writeObject.
             */
            void invokeWriteObject(Object obj, ObjectOutputStream out)
                    throws IOException, UnsupportedOperationException {
                if (writeObjectMethod != null) {
                    try {
                        writeObjectMethod.invoke(obj, new Object[] { out });
                    } catch (InvocationTargetException ex) {
                        Throwable th = ex.getTargetException();
                        if (th instanceof  IOException) {
                            throw (IOException) th;
                        } else {
                            throwMiscException(th);
                        }
                    } catch (IllegalAccessException ex) {
                        // should not occur, as access checks have been suppressed
                        throw new InternalError();
                    }
                } else {
                    throw new UnsupportedOperationException();
                }
            }

            /**
             * Invokes the readObject method of the represented serializable class.
             * Throws UnsupportedOperationException if this class descriptor is not
             * associated with a class, or if the class is externalizable,
             * non-serializable or does not define readObject.
             */
            void invokeReadObject(Object obj, ObjectInputStream in)
                    throws ClassNotFoundException, IOException,
                    UnsupportedOperationException {
                if (readObjectMethod != null) {
                    try {
                        readObjectMethod.invoke(obj, new Object[] { in });
                    } catch (InvocationTargetException ex) {
                        Throwable th = ex.getTargetException();
                        if (th instanceof  ClassNotFoundException) {
                            throw (ClassNotFoundException) th;
                        } else if (th instanceof  IOException) {
                            throw (IOException) th;
                        } else {
                            throwMiscException(th);
                        }
                    } catch (IllegalAccessException ex) {
                        // should not occur, as access checks have been suppressed
                        throw new InternalError();
                    }
                } else {
                    throw new UnsupportedOperationException();
                }
            }

            /**
             * Invokes the readObjectNoData method of the represented serializable
             * class.  Throws UnsupportedOperationException if this class descriptor is
             * not associated with a class, or if the class is externalizable,
             * non-serializable or does not define readObjectNoData.
             */
            void invokeReadObjectNoData(Object obj) throws IOException,
                    UnsupportedOperationException {
                if (readObjectNoDataMethod != null) {
                    try {
                        readObjectNoDataMethod.invoke(obj, (Object[]) null);
                    } catch (InvocationTargetException ex) {
                        Throwable th = ex.getTargetException();
                        if (th instanceof  ObjectStreamException) {
                            throw (ObjectStreamException) th;
                        } else {
                            throwMiscException(th);
                        }
                    } catch (IllegalAccessException ex) {
                        // should not occur, as access checks have been suppressed
                        throw new InternalError();
                    }
                } else {
                    throw new UnsupportedOperationException();
                }
            }

            /**
             * Invokes the writeReplace method of the represented serializable class and
             * returns the result.  Throws UnsupportedOperationException if this class
             * descriptor is not associated with a class, or if the class is
             * non-serializable or does not define writeReplace.
             */
            Object invokeWriteReplace(Object obj) throws IOException,
                    UnsupportedOperationException {
                if (writeReplaceMethod != null) {
                    try {
                        return writeReplaceMethod.invoke(obj, (Object[]) null);
                    } catch (InvocationTargetException ex) {
                        Throwable th = ex.getTargetException();
                        if (th instanceof  ObjectStreamException) {
                            throw (ObjectStreamException) th;
                        } else {
                            throwMiscException(th);
                            throw new InternalError(); // never reached
                        }
                    } catch (IllegalAccessException ex) {
                        // should not occur, as access checks have been suppressed
                        throw new InternalError();
                    }
                } else {
                    throw new UnsupportedOperationException();
                }
            }

            /**
             * Invokes the readResolve method of the represented serializable class and
             * returns the result.  Throws UnsupportedOperationException if this class
             * descriptor is not associated with a class, or if the class is
             * non-serializable or does not define readResolve.
             */
            Object invokeReadResolve(Object obj) throws IOException,
                    UnsupportedOperationException {
                if (readResolveMethod != null) {
                    try {
                        return readResolveMethod.invoke(obj, (Object[]) null);
                    } catch (InvocationTargetException ex) {
                        Throwable th = ex.getTargetException();
                        if (th instanceof  ObjectStreamException) {
                            throw (ObjectStreamException) th;
                        } else {
                            throwMiscException(th);
                            throw new InternalError(); // never reached
                        }
                    } catch (IllegalAccessException ex) {
                        // should not occur, as access checks have been suppressed
                        throw new InternalError();
                    }
                } else {
                    throw new UnsupportedOperationException();
                }
            }

            /**
             * Class representing the portion of an object's serialized form allotted
             * to data described by a given class descriptor.  If "hasData" is false,
             * the object's serialized form does not contain data associated with the
             * class descriptor.
             */
            static class ClassDataSlot {

                /** class descriptor "occupying" this slot */
                final ObjectStreamClass desc;
                /** true if serialized form includes data for this slot's descriptor */
                final boolean hasData;

                ClassDataSlot(ObjectStreamClass desc, boolean hasData) {
                    this .desc = desc;
                    this .hasData = hasData;
                }
            }

            /**
             * Returns array of ClassDataSlot instances representing the data layout
             * (including superclass data) for serialized objects described by this
             * class descriptor.  ClassDataSlots are ordered by inheritance with those
             * containing "higher" superclasses appearing first.  The final
             * ClassDataSlot contains a reference to this descriptor.
             */
            ClassDataSlot[] getClassDataLayout() throws InvalidClassException {
                // REMIND: synchronize instead of relying on volatile?
                if (dataLayout == null) {
                    dataLayout = getClassDataLayout0();
                }
                return dataLayout;
            }

            private ClassDataSlot[] getClassDataLayout0()
                    throws InvalidClassException {
                ArrayList slots = new ArrayList();
                Class start = cl, end = cl;

                // locate closest non-serializable superclass
                while (end != null && Serializable.class.isAssignableFrom(end)) {
                    end = end.getSuperclass();
                }

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

                    // search up inheritance hierarchy for class with matching name
                    String searchName = (d.cl != null) ? d.cl.getName()
                            : d.name;
                    Class match = null;
                    for (Class c = start; c != end; c = c.getSuperclass()) {
                        if (searchName.equals(c.getName())) {
                            match = c;
                            break;
                        }
                    }

                    // add "no data" slot for each unmatched class below match
                    if (match != null) {
                        for (Class c = start; c != match; c = c.getSuperclass()) {
                            slots.add(new ClassDataSlot(ObjectStreamClass
                                    .lookup(c, true), false));
                        }
                        start = match.getSuperclass();
                    }

                    // record descriptor/class pairing
                    slots.add(new ClassDataSlot(d.getVariantFor(match), true));
                }

                // add "no data" slot for any leftover unmatched classes
                for (Class c = start; c != end; c = c.getSuperclass()) {
                    slots.add(new ClassDataSlot(ObjectStreamClass.lookup(c,
                            true), false));
                }

                // order slots from superclass -> subclass
                Collections.reverse(slots);
                return (ClassDataSlot[]) slots.toArray(new ClassDataSlot[slots
                        .size()]);
            }

            /**
             * Returns aggregate size (in bytes) of marshalled primitive field values
             * for represented class.
             */
            int getPrimDataSize() {
                return primDataSize;
            }

            /**
             * Returns number of non-primitive serializable fields of represented
             * class.
             */
            int getNumObjFields() {
                return numObjFields;
            }

            /**
             * Fetches the serializable primitive field values of object obj and
             * marshals them into byte array buf starting at offset 0.  It is the
             * responsibility of the caller to ensure that obj is of the proper type if
             * non-null.
             */
            void getPrimFieldValues(Object obj, byte[] buf) {
                fieldRefl.getPrimFieldValues(obj, buf);
            }

            /**
             * Sets the serializable primitive fields of object obj using values
             * unmarshalled from byte array buf starting at offset 0.  It is the
             * responsibility of the caller to ensure that obj is of the proper type if
             * non-null.
             */
            void setPrimFieldValues(Object obj, byte[] buf) {
                fieldRefl.setPrimFieldValues(obj, buf);
            }

            /**
             * Fetches the serializable object field values of object obj and stores
             * them in array vals starting at offset 0.  It is the responsibility of
             * the caller to ensure that obj is of the proper type if non-null.
             */
            void getObjFieldValues(Object obj, Object[] vals) {
                fieldRefl.getObjFieldValues(obj, vals);
            }

            /**
             * Sets the serializable object fields of object obj using values from
             * array vals starting at offset 0.  It is the responsibility of the caller
             * to ensure that obj is of the proper type if non-null.
             */
            void setObjFieldValues(Object obj, Object[] vals) {
                fieldRefl.setObjFieldValues(obj, vals);
            }

            /**
             * Calculates and sets serializable field offsets, as well as primitive
             * data size and object field count totals.  Throws InvalidClassException
             * if fields are illegally ordered.
             */
            private void computeFieldOffsets() throws InvalidClassException {
                primDataSize = 0;
                numObjFields = 0;
                int firstObjIndex = -1;

                for (int i = 0; i < fields.length; i++) {
                    ObjectStreamField f = fields[i];
                    switch (f.getTypeCode()) {
                    case 'Z':
                    case 'B':
                        f.setOffset(primDataSize++);
                        break;

                    case 'C':
                    case 'S':
                        f.setOffset(primDataSize);
                        primDataSize += 2;
                        break;

                    case 'I':
                    case 'F':
                        f.setOffset(primDataSize);
                        primDataSize += 4;
                        break;

                    case 'J':
                    case 'D':
                        f.setOffset(primDataSize);
                        primDataSize += 8;
                        break;

                    case '[':
                    case 'L':
                        f.setOffset(numObjFields++);
                        if (firstObjIndex == -1) {
                            firstObjIndex = i;
                        }
                        break;

                    default:
                        throw new InternalError();
                    }
                }
                if (firstObjIndex != -1
                        && firstObjIndex + numObjFields != fields.length) {
                    throw new InvalidClassException(name, "illegal field order");
                }
            }

            /**
             * If given class is the same as the class associated with this class
             * descriptor, returns reference to this class descriptor.  Otherwise,
             * returns variant of this class descriptor bound to given class.
             */
            private ObjectStreamClass getVariantFor(Class cl)
                    throws InvalidClassException {
                if (this .cl == cl) {
                    return this ;
                }
                ObjectStreamClass desc = new ObjectStreamClass();
                if (isProxy) {
                    desc.initProxy(cl, null, super Desc);
                } else {
                    desc.initNonProxy(this , cl, null, super Desc);
                }
                return desc;
            }

            /**
             * Returns public no-arg constructor of given class, or null if none found.
             * Access checks are disabled on the returned constructor (if any), since
             * the defining class may still be non-public.
             */
            private static Constructor getExternalizableConstructor(Class cl) {
                try {
                    Constructor cons = cl
                            .getDeclaredConstructor((Class[]) null);
                    cons.setAccessible(true);
                    return ((cons.getModifiers() & Modifier.PUBLIC) != 0) ? cons
                            : null;
                } catch (NoSuchMethodException ex) {
                    return null;
                }
            }

            /**
             * Returns subclass-accessible no-arg constructor of first non-serializable
             * superclass, or null if none found.  Access checks are disabled on the
             * returned constructor (if any).
             */
            private static Constructor getSerializableConstructor(Class cl) {
                Class initCl = cl;
                while (Serializable.class.isAssignableFrom(initCl)) {
                    if ((initCl = initCl.getSuperclass()) == null) {
                        return null;
                    }
                }
                try {
                    Constructor cons = initCl
                            .getDeclaredConstructor((Class[]) null);
                    int mods = cons.getModifiers();
                    if ((mods & Modifier.PRIVATE) != 0
                            || ((mods & (Modifier.PUBLIC | Modifier.PROTECTED)) == 0 && !packageEquals(
                                    cl, initCl))) {
                        return null;
                    }
                    cons = reflFactory.newConstructorForSerialization(cl, cons);
                    cons.setAccessible(true);
                    return cons;
                } catch (NoSuchMethodException ex) {
                    return null;
                }
            }

            /**
             * Returns non-static, non-abstract method with given signature provided it
             * is defined by or accessible (via inheritance) by the given class, or
             * null if no match found.  Access checks are disabled on the returned
             * method (if any).
             */
            private static Method getInheritableMethod(Class cl, String name,
                    Class[] argTypes, Class returnType) {
                Method meth = null;
                Class defCl = cl;
                while (defCl != null) {
                    try {
                        meth = defCl.getDeclaredMethod(name, argTypes);
                        break;
                    } catch (NoSuchMethodException ex) {
                        defCl = defCl.getSuperclass();
                    }
                }

                if ((meth == null) || (meth.getReturnType() != returnType)) {
                    return null;
                }
                meth.setAccessible(true);
                int mods = meth.getModifiers();
                if ((mods & (Modifier.STATIC | Modifier.ABSTRACT)) != 0) {
                    return null;
                } else if ((mods & (Modifier.PUBLIC | Modifier.PROTECTED)) != 0) {
                    return meth;
                } else if ((mods & Modifier.PRIVATE) != 0) {
                    return (cl == defCl) ? meth : null;
                } else {
                    return packageEquals(cl, defCl) ? meth : null;
                }
            }

            /**
             * Returns non-static private method with given signature defined by given
             * class, or null if none found.  Access checks are disabled on the
             * returned method (if any).
             */
            private static Method getPrivateMethod(Class cl, String name,
                    Class[] argTypes, Class returnType) {
                try {
                    Method meth = cl.getDeclaredMethod(name, argTypes);
                    meth.setAccessible(true);
                    int mods = meth.getModifiers();
                    return ((meth.getReturnType() == returnType)
                            && ((mods & Modifier.STATIC) == 0) && ((mods & Modifier.PRIVATE) != 0)) ? meth
                            : null;
                } catch (NoSuchMethodException ex) {
                    return null;
                }
            }

            /**
             * Returns true if classes are defined in the same runtime package, false
             * otherwise.
             */
            private static boolean packageEquals(Class cl1, Class cl2) {
                return (cl1.getClassLoader() == cl2.getClassLoader() && getPackageName(
                        cl1).equals(getPackageName(cl2)));
            }

            /**
             * Returns package name of given class.
             */
            private static String getPackageName(Class cl) {
                String s = cl.getName();
                int i = s.lastIndexOf('[');
                if (i >= 0) {
                    s = s.substring(i + 2);
                }
                i = s.lastIndexOf('.');
                return (i >= 0) ? s.substring(0, i) : "";
            }

            /**
             * Compares class names for equality, ignoring package names.  Returns true
             * if class names equal, false otherwise.
             */
            private static boolean classNamesEqual(String name1, String name2) {
                name1 = name1.substring(name1.lastIndexOf('.') + 1);
                name2 = name2.substring(name2.lastIndexOf('.') + 1);
                return name1.equals(name2);
            }

            /**
             * Returns JVM type signature for given class.
             */
            static String getClassSignature(Class cl) {
                StringBuilder sbuf = new StringBuilder();
                while (cl.isArray()) {
                    sbuf.append('[');
                    cl = cl.getComponentType();
                }
                if (cl.isPrimitive()) {
                    if (cl == Integer.TYPE) {
                        sbuf.append('I');
                    } else if (cl == Byte.TYPE) {
                        sbuf.append('B');
                    } else if (cl == Long.TYPE) {
                        sbuf.append('J');
                    } else if (cl == Float.TYPE) {
                        sbuf.append('F');
                    } else if (cl == Double.TYPE) {
                        sbuf.append('D');
                    } else if (cl == Short.TYPE) {
                        sbuf.append('S');
                    } else if (cl == Character.TYPE) {
                        sbuf.append('C');
                    } else if (cl == Boolean.TYPE) {
                        sbuf.append('Z');
                    } else if (cl == Void.TYPE) {
                        sbuf.append('V');
                    } else {
                        throw new InternalError();
                    }
                } else {
                    sbuf.append('L' + cl.getName().replace('.', '/') + ';');
                }
                return sbuf.toString();
            }

            /**
             * Returns JVM type signature for given list of parameters and return type.
             */
            private static String getMethodSignature(Class[] paramTypes,
                    Class retType) {
                StringBuilder sbuf = new StringBuilder();
                sbuf.append('(');
                for (int i = 0; i < paramTypes.length; i++) {
                    sbuf.append(getClassSignature(paramTypes[i]));
                }
                sbuf.append(')');
                sbuf.append(getClassSignature(retType));
                return sbuf.toString();
            }

            /**
             * Convenience method for throwing an exception that is either a
             * RuntimeException, Error, or of some unexpected type (in which case it is
             * wrapped inside an IOException).
             */
            private static void throwMiscException(Throwable th)
                    throws IOException {
                if (th instanceof  RuntimeException) {
                    throw (RuntimeException) th;
                } else if (th instanceof  Error) {
                    throw (Error) th;
                } else {
                    IOException ex = new IOException(
                            "unexpected exception type");
                    ex.initCause(th);
                    throw ex;
                }
            }

            /**
             * Returns ObjectStreamField array describing the serializable fields of
             * the given class.  Serializable fields backed by an actual field of the
             * class are represented by ObjectStreamFields with corresponding non-null
             * Field objects.  Throws InvalidClassException if the (explicitly
             * declared) serializable fields are invalid.
             */
            private static ObjectStreamField[] getSerialFields(Class cl)
                    throws InvalidClassException {
                ObjectStreamField[] fields;
                if (Serializable.class.isAssignableFrom(cl)
                        && !Externalizable.class.isAssignableFrom(cl)
                        && !Proxy.isProxyClass(cl) && !cl.isInterface()) {
                    if ((fields = getDeclaredSerialFields(cl)) == null) {
                        fields = getDefaultSerialFields(cl);
                    }
                    Arrays.sort(fields);
                } else {
                    fields = NO_FIELDS;
                }
                return fields;
            }

            /**
             * Returns serializable fields of given class as defined explicitly by a
             * "serialPersistentFields" field, or null if no appropriate
             * "serialPersistentFields" field is defined.  Serializable fields backed
             * by an actual field of the class are represented by ObjectStreamFields
             * with corresponding non-null Field objects.  For compatibility with past
             * releases, a "serialPersistentFields" field with a null value is
             * considered equivalent to not declaring "serialPersistentFields".  Throws
             * InvalidClassException if the declared serializable fields are
             * invalid--e.g., if multiple fields share the same name.
             */
            private static ObjectStreamField[] getDeclaredSerialFields(Class cl)
                    throws InvalidClassException {
                ObjectStreamField[] serialPersistentFields = null;
                try {
                    Field f = cl.getDeclaredField("serialPersistentFields");
                    int mask = Modifier.PRIVATE | Modifier.STATIC
                            | Modifier.FINAL;
                    if ((f.getModifiers() & mask) == mask) {
                        f.setAccessible(true);
                        serialPersistentFields = (ObjectStreamField[]) f
                                .get(null);
                    }
                } catch (Exception ex) {
                }
                if (serialPersistentFields == null) {
                    return null;
                } else if (serialPersistentFields.length == 0) {
                    return NO_FIELDS;
                }

                ObjectStreamField[] boundFields = new ObjectStreamField[serialPersistentFields.length];
                Set fieldNames = new HashSet(serialPersistentFields.length);

                for (int i = 0; i < serialPersistentFields.length; i++) {
                    ObjectStreamField spf = serialPersistentFields[i];

                    String fname = spf.getName();
                    if (fieldNames.contains(fname)) {
                        throw new InvalidClassException(
                                "multiple serializable fields named " + fname);
                    }
                    fieldNames.add(fname);

                    try {
                        Field f = cl.getDeclaredField(fname);
                        if ((f.getType() == spf.getType())
                                && ((f.getModifiers() & Modifier.STATIC) == 0)) {
                            boundFields[i] = new ObjectStreamField(f, spf
                                    .isUnshared(), true);
                        }
                    } catch (NoSuchFieldException ex) {
                    }
                    if (boundFields[i] == null) {
                        boundFields[i] = new ObjectStreamField(fname, spf
                                .getType(), spf.isUnshared());
                    }
                }
                return boundFields;
            }

            /**
             * Returns array of ObjectStreamFields corresponding to all non-static
             * non-transient fields declared by given class.  Each ObjectStreamField
             * contains a Field object for the field it represents.  If no default
             * serializable fields exist, NO_FIELDS is returned.
             */
            private static ObjectStreamField[] getDefaultSerialFields(Class cl) {
                Field[] clFields = cl.getDeclaredFields();
                ArrayList list = new ArrayList();
                int mask = Modifier.STATIC | Modifier.TRANSIENT;

                for (int i = 0; i < clFields.length; i++) {
                    if ((clFields[i].getModifiers() & mask) == 0) {
                        list
                                .add(new ObjectStreamField(clFields[i], false,
                                        true));
                    }
                }
                int size = list.size();
                return (size == 0) ? NO_FIELDS : (ObjectStreamField[]) list
                        .toArray(new ObjectStreamField[size]);
            }

            /**
             * Returns explicit serial version UID value declared by given class, or
             * null if none.
             */
            private static Long getDeclaredSUID(Class cl) {
                try {
                    Field f = cl.getDeclaredField("serialVersionUID");
                    int mask = Modifier.STATIC | Modifier.FINAL;
                    if ((f.getModifiers() & mask) == mask) {
                        f.setAccessible(true);
                        return Long.valueOf(f.getLong(null));
                    }
                } catch (Exception ex) {
                }
                return null;
            }

            /**
             * Computes the default serial version UID value for the given class.
             */
            private static long computeDefaultSUID(Class cl) {
                if (!Serializable.class.isAssignableFrom(cl)
                        || Proxy.isProxyClass(cl)) {
                    return 0L;
                }

                try {
                    ByteArrayOutputStream bout = new ByteArrayOutputStream();
                    DataOutputStream dout = new DataOutputStream(bout);

                    dout.writeUTF(cl.getName());

                    int classMods = cl.getModifiers()
                            & (Modifier.PUBLIC | Modifier.FINAL
                                    | Modifier.INTERFACE | Modifier.ABSTRACT);

                    /*
                     * compensate for javac bug in which ABSTRACT bit was set for an
                     * interface only if the interface declared methods
                     */
                    Method[] methods = cl.getDeclaredMethods();
                    if ((classMods & Modifier.INTERFACE) != 0) {
                        classMods = (methods.length > 0) ? (classMods | Modifier.ABSTRACT)
                                : (classMods & ~Modifier.ABSTRACT);
                    }
                    dout.writeInt(classMods);

                    if (!cl.isArray()) {
                        /*
                         * compensate for change in 1.2FCS in which
                         * Class.getInterfaces() was modified to return Cloneable and
                         * Serializable for array classes.
                         */
                        Class[] interfaces = cl.getInterfaces();
                        String[] ifaceNames = new String[interfaces.length];
                        for (int i = 0; i < interfaces.length; i++) {
                            ifaceNames[i] = interfaces[i].getName();
                        }
                        Arrays.sort(ifaceNames);
                        for (int i = 0; i < ifaceNames.length; i++) {
                            dout.writeUTF(ifaceNames[i]);
                        }
                    }

                    Field[] fields = cl.getDeclaredFields();
                    MemberSignature[] fieldSigs = new MemberSignature[fields.length];
                    for (int i = 0; i < fields.length; i++) {
                        fieldSigs[i] = new MemberSignature(fields[i]);
                    }
                    Arrays.sort(fieldSigs, new Comparator() {
                        public int compare(Object o1, Object o2) {
                            String name1 = ((MemberSignature) o1).name;
                            String name2 = ((MemberSignature) o2).name;
                            return name1.compareTo(name2);
                        }
                    });
                    for (int i = 0; i < fieldSigs.length; i++) {
                        MemberSignature sig = fieldSigs[i];
                        int mods = sig.member.getModifiers()
                                & (Modifier.PUBLIC | Modifier.PRIVATE
                                        | Modifier.PROTECTED | Modifier.STATIC
                                        | Modifier.FINAL | Modifier.VOLATILE | Modifier.TRANSIENT);
                        if (((mods & Modifier.PRIVATE) == 0)
                                || ((mods & (Modifier.STATIC | Modifier.TRANSIENT)) == 0)) {
                            dout.writeUTF(sig.name);
                            dout.writeInt(mods);
                            dout.writeUTF(sig.signature);
                        }
                    }

                    if (hasStaticInitializer(cl)) {
                        dout.writeUTF("<clinit>");
                        dout.writeInt(Modifier.STATIC);
                        dout.writeUTF("()V");
                    }

                    Constructor[] cons = cl.getDeclaredConstructors();
                    MemberSignature[] consSigs = new MemberSignature[cons.length];
                    for (int i = 0; i < cons.length; i++) {
                        consSigs[i] = new MemberSignature(cons[i]);
                    }
                    Arrays.sort(consSigs, new Comparator() {
                        public int compare(Object o1, Object o2) {
                            String sig1 = ((MemberSignature) o1).signature;
                            String sig2 = ((MemberSignature) o2).signature;
                            return sig1.compareTo(sig2);
                        }
                    });
                    for (int i = 0; i < consSigs.length; i++) {
                        MemberSignature sig = consSigs[i];
                        int mods = sig.member.getModifiers()
                                & (Modifier.PUBLIC | Modifier.PRIVATE
                                        | Modifier.PROTECTED | Modifier.STATIC
                                        | Modifier.FINAL
                                        | Modifier.SYNCHRONIZED
                                        | Modifier.NATIVE | Modifier.ABSTRACT | Modifier.STRICT);
                        if ((mods & Modifier.PRIVATE) == 0) {
                            dout.writeUTF("<init>");
                            dout.writeInt(mods);
                            dout.writeUTF(sig.signature.replace('/', '.'));
                        }
                    }

                    MemberSignature[] methSigs = new MemberSignature[methods.length];
                    for (int i = 0; i < methods.length; i++) {
                        methSigs[i] = new MemberSignature(methods[i]);
                    }
                    Arrays.sort(methSigs, new Comparator() {
                        public int compare(Object o1, Object o2) {
                            MemberSignature ms1 = (MemberSignature) o1;
                            MemberSignature ms2 = (MemberSignature) o2;
                            int comp = ms1.name.compareTo(ms2.name);
                            if (comp == 0) {
                                comp = ms1.signature.compareTo(ms2.signature);
                            }
                            return comp;
                        }
                    });
                    for (int i = 0; i < methSigs.length; i++) {
                        MemberSignature sig = methSigs[i];
                        int mods = sig.member.getModifiers()
                                & (Modifier.PUBLIC | Modifier.PRIVATE
                                        | Modifier.PROTECTED | Modifier.STATIC
                                        | Modifier.FINAL
                                        | Modifier.SYNCHRONIZED
                                        | Modifier.NATIVE | Modifier.ABSTRACT | Modifier.STRICT);
                        if ((mods & Modifier.PRIVATE) == 0) {
                            dout.writeUTF(sig.name);
                            dout.writeInt(mods);
                            dout.writeUTF(sig.signature.replace('/', '.'));
                        }
                    }

                    dout.flush();

                    MessageDigest md = MessageDigest.getInstance("SHA");
                    byte[] hashBytes = md.digest(bout.toByteArray());
                    long hash = 0;
                    for (int i = Math.min(hashBytes.length, 8) - 1; i >= 0; i--) {
                        hash = (hash << 8) | (hashBytes[i] & 0xFF);
                    }
                    return hash;
                } catch (IOException ex) {
                    throw new InternalError();
                } catch (NoSuchAlgorithmException ex) {
                    throw new SecurityException(ex.getMessage());
                }
            }

            /**
             * Returns true if the given class defines a static initializer method,
             * false otherwise.
             */
            private native static boolean hasStaticInitializer(Class cl);

            /**
             * Class for computing and caching field/constructor/method signatures
             * during serialVersionUID calculation.
             */
            private static class MemberSignature {

                public final Member member;
                public final String name;
                public final String signature;

                public MemberSignature(Field field) {
                    member = field;
                    name = field.getName();
                    signature = getClassSignature(field.getType());
                }

                public MemberSignature(Constructor cons) {
                    member = cons;
                    name = cons.getName();
                    signature = getMethodSignature(cons.getParameterTypes(),
                            Void.TYPE);
                }

                public MemberSignature(Method meth) {
                    member = meth;
                    name = meth.getName();
                    signature = getMethodSignature(meth.getParameterTypes(),
                            meth.getReturnType());
                }
            }

            /**
             * Class for setting and retrieving serializable field values in batch.
             */
            // REMIND: dynamically generate these?
            private static class FieldReflector {

                /** handle for performing unsafe operations */
                private static final Unsafe unsafe = Unsafe.getUnsafe();

                /** fields to operate on */
                private final ObjectStreamField[] fields;
                /** number of primitive fields */
                private final int numPrimFields;
                /** unsafe field keys */
                private final long[] keys;
                /** field data offsets */
                private final int[] offsets;
                /** field type codes */
                private final char[] typeCodes;
                /** field types */
                private final Class[] types;

                /**
                 * Constructs FieldReflector capable of setting/getting values from the
                 * subset of fields whose ObjectStreamFields contain non-null
                 * reflective Field objects.  ObjectStreamFields with null Fields are
                 * treated as filler, for which get operations return default values
                 * and set operations discard given values.
                 */
                FieldReflector(ObjectStreamField[] fields) {
                    this .fields = fields;
                    int nfields = fields.length;
                    keys = new long[nfields];
                    offsets = new int[nfields];
                    typeCodes = new char[nfields];
                    ArrayList typeList = new ArrayList();

                    for (int i = 0; i < nfields; i++) {
                        ObjectStreamField f = fields[i];
                        Field rf = f.getField();
                        keys[i] = (rf != null) ? unsafe.objectFieldOffset(rf)
                                : Unsafe.INVALID_FIELD_OFFSET;
                        offsets[i] = f.getOffset();
                        typeCodes[i] = f.getTypeCode();
                        if (!f.isPrimitive()) {
                            typeList.add((rf != null) ? rf.getType() : null);
                        }
                    }

                    types = (Class[]) typeList.toArray(new Class[typeList
                            .size()]);
                    numPrimFields = nfields - types.length;
                }

                /**
                 * Returns list of ObjectStreamFields representing fields operated on
                 * by this reflector.  The shared/unshared values and Field objects
                 * contained by ObjectStreamFields in the list reflect their bindings
                 * to locally defined serializable fields.
                 */
                ObjectStreamField[] getFields() {
                    return fields;
                }

                /**
                 * Fetches the serializable primitive field values of object obj and
                 * marshals them into byte array buf starting at offset 0.  The caller
                 * is responsible for ensuring that obj is of the proper type.
                 */
                void getPrimFieldValues(Object obj, byte[] buf) {
                    if (obj == null) {
                        throw new NullPointerException();
                    }
                    /* assuming checkDefaultSerialize() has been called on the class
                     * descriptor this FieldReflector was obtained from, no field keys
                     * in array should be equal to Unsafe.INVALID_FIELD_OFFSET.
                     */
                    for (int i = 0; i < numPrimFields; i++) {
                        long key = keys[i];
                        int off = offsets[i];
                        switch (typeCodes[i]) {
                        case 'Z':
                            Bits.putBoolean(buf, off, unsafe.getBoolean(obj,
                                    key));
                            break;

                        case 'B':
                            buf[off] = unsafe.getByte(obj, key);
                            break;

                        case 'C':
                            Bits.putChar(buf, off, unsafe.getChar(obj, key));
                            break;

                        case 'S':
                            Bits.putShort(buf, off, unsafe.getShort(obj, key));
                            break;

                        case 'I':
                            Bits.putInt(buf, off, unsafe.getInt(obj, key));
                            break;

                        case 'F':
                            Bits.putFloat(buf, off, unsafe.getFloat(obj, key));
                            break;

                        case 'J':
                            Bits.putLong(buf, off, unsafe.getLong(obj, key));
                            break;

                        case 'D':
                            Bits
                                    .putDouble(buf, off, unsafe.getDouble(obj,
                                            key));
                            break;

                        default:
                            throw new InternalError();
                        }
                    }
                }

                /**
                 * Sets the serializable primitive fields of object obj using values
                 * unmarshalled from byte array buf starting at offset 0.  The caller
                 * is responsible for ensuring that obj is of the proper type.
                 */
                void setPrimFieldValues(Object obj, byte[] buf) {
                    if (obj == null) {
                        throw new NullPointerException();
                    }
                    for (int i = 0; i < numPrimFields; i++) {
                        long key = keys[i];
                        if (key == Unsafe.INVALID_FIELD_OFFSET) {
                            continue; // discard value
                        }
                        int off = offsets[i];
                        switch (typeCodes[i]) {
                        case 'Z':
                            unsafe.putBoolean(obj, key, Bits.getBoolean(buf,
                                    off));
                            break;

                        case 'B':
                            unsafe.putByte(obj, key, buf[off]);
                            break;

                        case 'C':
                            unsafe.putChar(obj, key, Bits.getChar(buf, off));
                            break;

                        case 'S':
                            unsafe.putShort(obj, key, Bits.getShort(buf, off));
                            break;

                        case 'I':
                            unsafe.putInt(obj, key, Bits.getInt(buf, off));
                            break;

                        case 'F':
                            unsafe.putFloat(obj, key, Bits.getFloat(buf, off));
                            break;

                        case 'J':
                            unsafe.putLong(obj, key, Bits.getLong(buf, off));
                            break;

                        case 'D':
                            unsafe
                                    .putDouble(obj, key, Bits.getDouble(buf,
                                            off));
                            break;

                        default:
                            throw new InternalError();
                        }
                    }
                }

                /**
                 * Fetches the serializable object field values of object obj and
                 * stores them in array vals starting at offset 0.  The caller is
                 * responsible for ensuring that obj is of the proper type.
                 */
                void getObjFieldValues(Object obj, Object[] vals) {
                    if (obj == null) {
                        throw new NullPointerException();
                    }
                    /* assuming checkDefaultSerialize() has been called on the class
                     * descriptor this FieldReflector was obtained from, no field keys
                     * in array should be equal to Unsafe.INVALID_FIELD_OFFSET.
                     */
                    for (int i = numPrimFields; i < fields.length; i++) {
                        switch (typeCodes[i]) {
                        case 'L':
                        case '[':
                            vals[offsets[i]] = unsafe.getObject(obj, keys[i]);
                            break;

                        default:
                            throw new InternalError();
                        }
                    }
                }

                /**
                 * Sets the serializable object fields of object obj using values from
                 * array vals starting at offset 0.  The caller is responsible for
                 * ensuring that obj is of the proper type; however, attempts to set a
                 * field with a value of the wrong type will trigger an appropriate
                 * ClassCastException.
                 */
                void setObjFieldValues(Object obj, Object[] vals) {
                    if (obj == null) {
                        throw new NullPointerException();
                    }
                    for (int i = numPrimFields; i < fields.length; i++) {
                        long key = keys[i];
                        if (key == Unsafe.INVALID_FIELD_OFFSET) {
                            continue; // discard value
                        }
                        switch (typeCodes[i]) {
                        case 'L':
                        case '[':
                            Object val = vals[offsets[i]];
                            if (val != null
                                    && !types[i - numPrimFields]
                                            .isInstance(val)) {
                                Field f = fields[i].getField();
                                throw new ClassCastException(
                                        "cannot assign instance of "
                                                + val.getClass().getName()
                                                + " to field "
                                                + f.getDeclaringClass()
                                                        .getName() + "."
                                                + f.getName() + " of type "
                                                + f.getType().getName()
                                                + " in instance of "
                                                + obj.getClass().getName());
                            }
                            unsafe.putObject(obj, key, val);
                            break;

                        default:
                            throw new InternalError();
                        }
                    }
                }
            }

            /**
             * Matches given set of serializable fields with serializable fields
             * described by the given local class descriptor, and returns a
             * FieldReflector instance capable of setting/getting values from the
             * subset of fields that match (non-matching fields are treated as filler,
             * for which get operations return default values and set operations
             * discard given values).  Throws InvalidClassException if unresolvable
             * type conflicts exist between the two sets of fields.
             */
            private static FieldReflector getReflector(
                    ObjectStreamField[] fields, ObjectStreamClass localDesc)
                    throws InvalidClassException {
                // class irrelevant if no fields
                Class cl = (localDesc != null && fields.length > 0) ? localDesc.cl
                        : null;
                processQueue(Caches.reflectorsQueue, Caches.reflectors);
                FieldReflectorKey key = new FieldReflectorKey(cl, fields,
                        Caches.reflectorsQueue);
                Reference<?> ref = Caches.reflectors.get(key);
                Object entry = null;
                if (ref != null) {
                    entry = ref.get();
                }
                EntryFuture future = null;
                if (entry == null) {
                    EntryFuture newEntry = new EntryFuture();
                    Reference<?> newRef = new SoftReference<EntryFuture>(
                            newEntry);
                    do {
                        if (ref != null) {
                            Caches.reflectors.remove(key, ref);
                        }
                        ref = Caches.reflectors.putIfAbsent(key, newRef);
                        if (ref != null) {
                            entry = ref.get();
                        }
                    } while (ref != null && entry == null);
                    if (entry == null) {
                        future = newEntry;
                    }
                }

                if (entry instanceof  FieldReflector) { // check common case first
                    return (FieldReflector) entry;
                } else if (entry instanceof  EntryFuture) {
                    entry = ((EntryFuture) entry).get();
                } else if (entry == null) {
                    try {
                        entry = new FieldReflector(matchFields(fields,
                                localDesc));
                    } catch (Throwable th) {
                        entry = th;
                    }
                    future.set(entry);
                    Caches.reflectors
                            .put(key, new SoftReference<Object>(entry));
                }

                if (entry instanceof  FieldReflector) {
                    return (FieldReflector) entry;
                } else if (entry instanceof  InvalidClassException) {
                    throw (InvalidClassException) entry;
                } else if (entry instanceof  RuntimeException) {
                    throw (RuntimeException) entry;
                } else if (entry instanceof  Error) {
                    throw (Error) entry;
                } else {
                    throw new InternalError("unexpected entry: " + entry);
                }
            }

            /**
             * FieldReflector cache lookup key.  Keys are considered equal if they
             * refer to the same class and equivalent field formats.
             */
            private static class FieldReflectorKey extends
                    WeakReference<Class<?>> {

                private final String sigs;
                private final int hash;
                private final boolean nullClass;

                FieldReflectorKey(Class cl, ObjectStreamField[] fields,
                        ReferenceQueue<Class<?>> queue) {
                    super (cl, queue);
                    nullClass = (cl == null);
                    StringBuilder sbuf = new StringBuilder();
                    for (int i = 0; i < fields.length; i++) {
                        ObjectStreamField f = fields[i];
                        sbuf.append(f.getName()).append(f.getSignature());
                    }
                    sigs = sbuf.toString();
                    hash = System.identityHashCode(cl) + sigs.hashCode();
                }

                public int hashCode() {
                    return hash;
                }

                public boolean equals(Object obj) {
                    if (obj == this ) {
                        return true;
                    }

                    if (obj instanceof  FieldReflectorKey) {
                        FieldReflectorKey other = (FieldReflectorKey) obj;
                        Class<?> referent;
                        return (nullClass ? other.nullClass
                                : ((referent = get()) != null)
                                        && (referent == other.get()))
                                && sigs.equals(other.sigs);
                    } else {
                        return false;
                    }
                }
            }

            /**
             * Matches given set of serializable fields with serializable fields
             * obtained from the given local class descriptor (which contain bindings
             * to reflective Field objects).  Returns list of ObjectStreamFields in
             * which each ObjectStreamField whose signature matches that of a local
             * field contains a Field object for that field; unmatched
             * ObjectStreamFields contain null Field objects.  Shared/unshared settings
             * of the returned ObjectStreamFields also reflect those of matched local
             * ObjectStreamFields.  Throws InvalidClassException if unresolvable type
             * conflicts exist between the two sets of fields.
             */
            private static ObjectStreamField[] matchFields(
                    ObjectStreamField[] fields, ObjectStreamClass localDesc)
                    throws InvalidClassException {
                ObjectStreamField[] localFields = (localDesc != null) ? localDesc.fields
                        : NO_FIELDS;

                /*
                 * Even if fields == localFields, we cannot simply return localFields
                 * here.  In previous implementations of serialization,
                 * ObjectStreamField.getType() returned Object.class if the
                 * ObjectStreamField represented a non-primitive field and belonged to
                 * a non-local class descriptor.  To preserve this (questionable)
                 * behavior, the ObjectStreamField instances returned by matchFields
                 * cannot report non-primitive types other than Object.class; hence
                 * localFields cannot be returned directly.
                 */

                ObjectStreamField[] matches = new ObjectStreamField[fields.length];
                for (int i = 0; i < fields.length; i++) {
                    ObjectStreamField f = fields[i], m = null;
                    for (int j = 0; j < localFields.length; j++) {
                        ObjectStreamField lf = localFields[j];
                        if (f.getName().equals(lf.getName())) {
                            if ((f.isPrimitive() || lf.isPrimitive())
                                    && f.getTypeCode() != lf.getTypeCode()) {
                                throw new InvalidClassException(localDesc.name,
                                        "incompatible types for field "
                                                + f.getName());
                            }
                            if (lf.getField() != null) {
                                m = new ObjectStreamField(lf.getField(), lf
                                        .isUnshared(), false);
                            } else {
                                m = new ObjectStreamField(lf.getName(), lf
                                        .getSignature(), lf.isUnshared());
                            }
                        }
                    }
                    if (m == null) {
                        m = new ObjectStreamField(f.getName(),
                                f.getSignature(), false);
                    }
                    m.setOffset(f.getOffset());
                    matches[i] = m;
                }
                return matches;
            }

            /**
             * Removes from the specified map any keys that have been enqueued
             * on the specified reference queue.
             */
            static void processQueue(ReferenceQueue<Class<?>> queue,
                    ConcurrentMap<? extends WeakReference<Class<?>>, ?> map) {
                Reference<? extends Class<?>> ref;
                while ((ref = queue.poll()) != null) {
                    map.remove(ref);
                }
            }

            /**
             *  Weak key for Class objects.
             *
             **/
            static class WeakClassKey extends WeakReference<Class<?>> {
                /**
                 * saved value of the referent's identity hash code, to maintain
                 * a consistent hash code after the referent has been cleared
                 */
                private final int hash;

                /**
                 * Create a new WeakClassKey to the given object, registered 
                 * with a queue.
                 */
                WeakClassKey(Class<?> cl, ReferenceQueue<Class<?>> refQueue) {
                    super (cl, refQueue);
                    hash = System.identityHashCode(cl);
                }

                /**
                 * Returns the identity hash code of the original referent.
                 */
                public int hashCode() {
                    return hash;
                }

                /**
                 * Returns true if the given object is this identical 
                 * WeakClassKey instance, or, if this object's referent has not 
                 * been cleared, if the given object is another WeakClassKey 
                 * instance with the identical non-null referent as this one.
                 */
                public boolean equals(Object obj) {
                    if (obj == this ) {
                        return true;
                    }

                    if (obj instanceof  WeakClassKey) {
                        Object referent = get();
                        return (referent != null)
                                && (referent == ((WeakClassKey) obj).get());
                    } else {
                        return false;
                    }
                }
            }
        }
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