1 /*
   2  * Copyright (c) 1996, 2010, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.io;
  27 
  28 import java.io.ObjectStreamClass.WeakClassKey;
  29 import java.lang.ref.ReferenceQueue;
  30 import java.lang.reflect.Array;
  31 import java.lang.reflect.Modifier;
  32 import java.lang.reflect.Proxy;
  33 import java.security.AccessControlContext;
  34 import java.security.AccessController;
  35 import java.security.PrivilegedAction;
  36 import java.security.PrivilegedActionException;
  37 import java.security.PrivilegedExceptionAction;
  38 import java.util.Arrays;
  39 import java.util.HashMap;
  40 import java.util.concurrent.ConcurrentHashMap;
  41 import java.util.concurrent.ConcurrentMap;
  42 import java.util.concurrent.atomic.AtomicBoolean;
  43 import static java.io.ObjectStreamClass.processQueue;
  44 
  45 /**
  46  * An ObjectInputStream deserializes primitive data and objects previously
  47  * written using an ObjectOutputStream.
  48  *
  49  * <p>ObjectOutputStream and ObjectInputStream can provide an application with
  50  * persistent storage for graphs of objects when used with a FileOutputStream
  51  * and FileInputStream respectively.  ObjectInputStream is used to recover
  52  * those objects previously serialized. Other uses include passing objects
  53  * between hosts using a socket stream or for marshaling and unmarshaling
  54  * arguments and parameters in a remote communication system.
  55  *
  56  * <p>ObjectInputStream ensures that the types of all objects in the graph
  57  * created from the stream match the classes present in the Java Virtual
  58  * Machine.  Classes are loaded as required using the standard mechanisms.
  59  *
  60  * <p>Only objects that support the java.io.Serializable or
  61  * java.io.Externalizable interface can be read from streams.
  62  *
  63  * <p>The method <code>readObject</code> is used to read an object from the
  64  * stream.  Java's safe casting should be used to get the desired type.  In
  65  * Java, strings and arrays are objects and are treated as objects during
  66  * serialization. When read they need to be cast to the expected type.
  67  *
  68  * <p>Primitive data types can be read from the stream using the appropriate
  69  * method on DataInput.
  70  *
  71  * <p>The default deserialization mechanism for objects restores the contents
  72  * of each field to the value and type it had when it was written.  Fields
  73  * declared as transient or static are ignored by the deserialization process.
  74  * References to other objects cause those objects to be read from the stream
  75  * as necessary.  Graphs of objects are restored correctly using a reference
  76  * sharing mechanism.  New objects are always allocated when deserializing,
  77  * which prevents existing objects from being overwritten.
  78  *
  79  * <p>Reading an object is analogous to running the constructors of a new
  80  * object.  Memory is allocated for the object and initialized to zero (NULL).
  81  * No-arg constructors are invoked for the non-serializable classes and then
  82  * the fields of the serializable classes are restored from the stream starting
  83  * with the serializable class closest to java.lang.object and finishing with
  84  * the object's most specific class.
  85  *
  86  * <p>For example to read from a stream as written by the example in
  87  * ObjectOutputStream:
  88  * <br>
  89  * <pre>
  90  *      FileInputStream fis = new FileInputStream("t.tmp");
  91  *      ObjectInputStream ois = new ObjectInputStream(fis);
  92  *
  93  *      int i = ois.readInt();
  94  *      String today = (String) ois.readObject();
  95  *      Date date = (Date) ois.readObject();
  96  *
  97  *      ois.close();
  98  * </pre>
  99  *
 100  * <p>Classes control how they are serialized by implementing either the
 101  * java.io.Serializable or java.io.Externalizable interfaces.
 102  *
 103  * <p>Implementing the Serializable interface allows object serialization to
 104  * save and restore the entire state of the object and it allows classes to
 105  * evolve between the time the stream is written and the time it is read.  It
 106  * automatically traverses references between objects, saving and restoring
 107  * entire graphs.
 108  *
 109  * <p>Serializable classes that require special handling during the
 110  * serialization and deserialization process should implement the following
 111  * methods:<p>
 112  *
 113  * <pre>
 114  * private void writeObject(java.io.ObjectOutputStream stream)
 115  *     throws IOException;
 116  * private void readObject(java.io.ObjectInputStream stream)
 117  *     throws IOException, ClassNotFoundException;
 118  * private void readObjectNoData()
 119  *     throws ObjectStreamException;
 120  * </pre>
 121  *
 122  * <p>The readObject method is responsible for reading and restoring the state
 123  * of the object for its particular class using data written to the stream by
 124  * the corresponding writeObject method.  The method does not need to concern
 125  * itself with the state belonging to its superclasses or subclasses.  State is
 126  * restored by reading data from the ObjectInputStream for the individual
 127  * fields and making assignments to the appropriate fields of the object.
 128  * Reading primitive data types is supported by DataInput.
 129  *
 130  * <p>Any attempt to read object data which exceeds the boundaries of the
 131  * custom data written by the corresponding writeObject method will cause an
 132  * OptionalDataException to be thrown with an eof field value of true.
 133  * Non-object reads which exceed the end of the allotted data will reflect the
 134  * end of data in the same way that they would indicate the end of the stream:
 135  * bytewise reads will return -1 as the byte read or number of bytes read, and
 136  * primitive reads will throw EOFExceptions.  If there is no corresponding
 137  * writeObject method, then the end of default serialized data marks the end of
 138  * the allotted data.
 139  *
 140  * <p>Primitive and object read calls issued from within a readExternal method
 141  * behave in the same manner--if the stream is already positioned at the end of
 142  * data written by the corresponding writeExternal method, object reads will
 143  * throw OptionalDataExceptions with eof set to true, bytewise reads will
 144  * return -1, and primitive reads will throw EOFExceptions.  Note that this
 145  * behavior does not hold for streams written with the old
 146  * <code>ObjectStreamConstants.PROTOCOL_VERSION_1</code> protocol, in which the
 147  * end of data written by writeExternal methods is not demarcated, and hence
 148  * cannot be detected.
 149  *
 150  * <p>The readObjectNoData method is responsible for initializing the state of
 151  * the object for its particular class in the event that the serialization
 152  * stream does not list the given class as a superclass of the object being
 153  * deserialized.  This may occur in cases where the receiving party uses a
 154  * different version of the deserialized instance's class than the sending
 155  * party, and the receiver's version extends classes that are not extended by
 156  * the sender's version.  This may also occur if the serialization stream has
 157  * been tampered; hence, readObjectNoData is useful for initializing
 158  * deserialized objects properly despite a "hostile" or incomplete source
 159  * stream.
 160  *
 161  * <p>Serialization does not read or assign values to the fields of any object
 162  * that does not implement the java.io.Serializable interface.  Subclasses of
 163  * Objects that are not serializable can be serializable. In this case the
 164  * non-serializable class must have a no-arg constructor to allow its fields to
 165  * be initialized.  In this case it is the responsibility of the subclass to
 166  * save and restore the state of the non-serializable class. It is frequently
 167  * the case that the fields of that class are accessible (public, package, or
 168  * protected) or that there are get and set methods that can be used to restore
 169  * the state.
 170  *
 171  * <p>Any exception that occurs while deserializing an object will be caught by
 172  * the ObjectInputStream and abort the reading process.
 173  *
 174  * <p>Implementing the Externalizable interface allows the object to assume
 175  * complete control over the contents and format of the object's serialized
 176  * form.  The methods of the Externalizable interface, writeExternal and
 177  * readExternal, are called to save and restore the objects state.  When
 178  * implemented by a class they can write and read their own state using all of
 179  * the methods of ObjectOutput and ObjectInput.  It is the responsibility of
 180  * the objects to handle any versioning that occurs.
 181  *
 182  * <p>Enum constants are deserialized differently than ordinary serializable or
 183  * externalizable objects.  The serialized form of an enum constant consists
 184  * solely of its name; field values of the constant are not transmitted.  To
 185  * deserialize an enum constant, ObjectInputStream reads the constant name from
 186  * the stream; the deserialized constant is then obtained by calling the static
 187  * method <code>Enum.valueOf(Class, String)</code> with the enum constant's
 188  * base type and the received constant name as arguments.  Like other
 189  * serializable or externalizable objects, enum constants can function as the
 190  * targets of back references appearing subsequently in the serialization
 191  * stream.  The process by which enum constants are deserialized cannot be
 192  * customized: any class-specific readObject, readObjectNoData, and readResolve
 193  * methods defined by enum types are ignored during deserialization.
 194  * Similarly, any serialPersistentFields or serialVersionUID field declarations
 195  * are also ignored--all enum types have a fixed serialVersionUID of 0L.
 196  *
 197  * @author      Mike Warres
 198  * @author      Roger Riggs
 199  * @see java.io.DataInput
 200  * @see java.io.ObjectOutputStream
 201  * @see java.io.Serializable
 202  * @see <a href="../../../platform/serialization/spec/input.html"> Object Serialization Specification, Section 3, Object Input Classes</a>
 203  * @since   JDK1.1
 204  */
 205 public class ObjectInputStream
 206     extends InputStream implements ObjectInput, ObjectStreamConstants
 207 {
 208     /** handle value representing null */
 209     private static final int NULL_HANDLE = -1;
 210 
 211     /** marker for unshared objects in internal handle table */
 212     private static final Object unsharedMarker = new Object();
 213 
 214     /** table mapping primitive type names to corresponding class objects */
 215     private static final HashMap<String, Class<?>> primClasses
 216         = new HashMap<String, Class<?>>(8, 1.0F);
 217     static {
 218         primClasses.put("boolean", boolean.class);
 219         primClasses.put("byte", byte.class);
 220         primClasses.put("char", char.class);
 221         primClasses.put("short", short.class);
 222         primClasses.put("int", int.class);
 223         primClasses.put("long", long.class);
 224         primClasses.put("float", float.class);
 225         primClasses.put("double", double.class);
 226         primClasses.put("void", void.class);
 227     }
 228 
 229     private static class Caches {
 230         /** cache of subclass security audit results */
 231         static final ConcurrentMap<WeakClassKey,Boolean> subclassAudits =
 232             new ConcurrentHashMap<WeakClassKey,Boolean>();
 233 
 234         /** queue for WeakReferences to audited subclasses */
 235         static final ReferenceQueue<Class<?>> subclassAuditsQueue =
 236             new ReferenceQueue<Class<?>>();
 237     }
 238 
 239     /** filter stream for handling block data conversion */
 240     private final BlockDataInputStream bin;
 241     /** validation callback list */
 242     private final ValidationList vlist;
 243     /** recursion depth */
 244     private int depth;
 245     /** whether stream is closed */
 246     private boolean closed;
 247 
 248     /** wire handle -> obj/exception map */
 249     private final HandleTable handles;
 250     /** scratch field for passing handle values up/down call stack */
 251     private int passHandle = NULL_HANDLE;
 252     /** flag set when at end of field value block with no TC_ENDBLOCKDATA */
 253     private boolean defaultDataEnd = false;
 254 
 255     /** buffer for reading primitive field values */
 256     private byte[] primVals;
 257 
 258     /** if true, invoke readObjectOverride() instead of readObject() */
 259     private final boolean enableOverride;
 260     /** if true, invoke resolveObject() */
 261     private boolean enableResolve;
 262 
 263     /**
 264      * Context during upcalls to class-defined readObject methods; holds
 265      * object currently being deserialized and descriptor for current class.
 266      * Null when not during readObject upcall.
 267      */
 268     private SerialCallbackContext curContext;
 269 
 270     /**
 271      * Creates an ObjectInputStream that reads from the specified InputStream.
 272      * A serialization stream header is read from the stream and verified.
 273      * This constructor will block until the corresponding ObjectOutputStream
 274      * has written and flushed the header.
 275      *
 276      * <p>If a security manager is installed, this constructor will check for
 277      * the "enableSubclassImplementation" SerializablePermission when invoked
 278      * directly or indirectly by the constructor of a subclass which overrides
 279      * the ObjectInputStream.readFields or ObjectInputStream.readUnshared
 280      * methods.
 281      *
 282      * @param   in input stream to read from
 283      * @throws  StreamCorruptedException if the stream header is incorrect
 284      * @throws  IOException if an I/O error occurs while reading stream header
 285      * @throws  SecurityException if untrusted subclass illegally overrides
 286      *          security-sensitive methods
 287      * @throws  NullPointerException if <code>in</code> is <code>null</code>
 288      * @see     ObjectInputStream#ObjectInputStream()
 289      * @see     ObjectInputStream#readFields()
 290      * @see     ObjectOutputStream#ObjectOutputStream(OutputStream)
 291      */
 292     public ObjectInputStream(InputStream in) throws IOException {
 293         verifySubclass();
 294         bin = new BlockDataInputStream(in);
 295         handles = new HandleTable(10);
 296         vlist = new ValidationList();
 297         enableOverride = false;
 298         readStreamHeader();
 299         bin.setBlockDataMode(true);
 300     }
 301 
 302     /**
 303      * Provide a way for subclasses that are completely reimplementing
 304      * ObjectInputStream to not have to allocate private data just used by this
 305      * implementation of ObjectInputStream.
 306      *
 307      * <p>If there is a security manager installed, this method first calls the
 308      * security manager's <code>checkPermission</code> method with the
 309      * <code>SerializablePermission("enableSubclassImplementation")</code>
 310      * permission to ensure it's ok to enable subclassing.
 311      *
 312      * @throws  SecurityException if a security manager exists and its
 313      *          <code>checkPermission</code> method denies enabling
 314      *          subclassing.
 315      * @see SecurityManager#checkPermission
 316      * @see java.io.SerializablePermission
 317      */
 318     protected ObjectInputStream() throws IOException, SecurityException {
 319         SecurityManager sm = System.getSecurityManager();
 320         if (sm != null) {
 321             sm.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
 322         }
 323         bin = null;
 324         handles = null;
 325         vlist = null;
 326         enableOverride = true;
 327     }
 328 
 329     /**
 330      * Read an object from the ObjectInputStream.  The class of the object, the
 331      * signature of the class, and the values of the non-transient and
 332      * non-static fields of the class and all of its supertypes are read.
 333      * Default deserializing for a class can be overriden using the writeObject
 334      * and readObject methods.  Objects referenced by this object are read
 335      * transitively so that a complete equivalent graph of objects is
 336      * reconstructed by readObject.
 337      *
 338      * <p>The root object is completely restored when all of its fields and the
 339      * objects it references are completely restored.  At this point the object
 340      * validation callbacks are executed in order based on their registered
 341      * priorities. The callbacks are registered by objects (in the readObject
 342      * special methods) as they are individually restored.
 343      *
 344      * <p>Exceptions are thrown for problems with the InputStream and for
 345      * classes that should not be deserialized.  All exceptions are fatal to
 346      * the InputStream and leave it in an indeterminate state; it is up to the
 347      * caller to ignore or recover the stream state.
 348      *
 349      * @throws  ClassNotFoundException Class of a serialized object cannot be
 350      *          found.
 351      * @throws  InvalidClassException Something is wrong with a class used by
 352      *          serialization.
 353      * @throws  StreamCorruptedException Control information in the
 354      *          stream is inconsistent.
 355      * @throws  OptionalDataException Primitive data was found in the
 356      *          stream instead of objects.
 357      * @throws  IOException Any of the usual Input/Output related exceptions.
 358      */
 359     public final Object readObject()
 360         throws IOException, ClassNotFoundException
 361     {
 362         if (enableOverride) {
 363             return readObjectOverride();
 364         }
 365 
 366         // if nested read, passHandle contains handle of enclosing object
 367         int outerHandle = passHandle;
 368         try {
 369             Object obj = readObject0(false);
 370             handles.markDependency(outerHandle, passHandle);
 371             ClassNotFoundException ex = handles.lookupException(passHandle);
 372             if (ex != null) {
 373                 throw ex;
 374             }
 375             if (depth == 0) {
 376                 vlist.doCallbacks();
 377             }
 378             return obj;
 379         } finally {
 380             passHandle = outerHandle;
 381             if (closed && depth == 0) {
 382                 clear();
 383             }
 384         }
 385     }
 386 
 387     /**
 388      * This method is called by trusted subclasses of ObjectOutputStream that
 389      * constructed ObjectOutputStream using the protected no-arg constructor.
 390      * The subclass is expected to provide an override method with the modifier
 391      * "final".
 392      *
 393      * @return  the Object read from the stream.
 394      * @throws  ClassNotFoundException Class definition of a serialized object
 395      *          cannot be found.
 396      * @throws  OptionalDataException Primitive data was found in the stream
 397      *          instead of objects.
 398      * @throws  IOException if I/O errors occurred while reading from the
 399      *          underlying stream
 400      * @see #ObjectInputStream()
 401      * @see #readObject()
 402      * @since 1.2
 403      */
 404     protected Object readObjectOverride()
 405         throws IOException, ClassNotFoundException
 406     {
 407         return null;
 408     }
 409 
 410     /**
 411      * Reads an "unshared" object from the ObjectInputStream.  This method is
 412      * identical to readObject, except that it prevents subsequent calls to
 413      * readObject and readUnshared from returning additional references to the
 414      * deserialized instance obtained via this call.  Specifically:
 415      * <ul>
 416      *   <li>If readUnshared is called to deserialize a back-reference (the
 417      *       stream representation of an object which has been written
 418      *       previously to the stream), an ObjectStreamException will be
 419      *       thrown.
 420      *
 421      *   <li>If readUnshared returns successfully, then any subsequent attempts
 422      *       to deserialize back-references to the stream handle deserialized
 423      *       by readUnshared will cause an ObjectStreamException to be thrown.
 424      * </ul>
 425      * Deserializing an object via readUnshared invalidates the stream handle
 426      * associated with the returned object.  Note that this in itself does not
 427      * always guarantee that the reference returned by readUnshared is unique;
 428      * the deserialized object may define a readResolve method which returns an
 429      * object visible to other parties, or readUnshared may return a Class
 430      * object or enum constant obtainable elsewhere in the stream or through
 431      * external means. If the deserialized object defines a readResolve method
 432      * and the invocation of that method returns an array, then readUnshared
 433      * returns a shallow clone of that array; this guarantees that the returned
 434      * array object is unique and cannot be obtained a second time from an
 435      * invocation of readObject or readUnshared on the ObjectInputStream,
 436      * even if the underlying data stream has been manipulated.
 437      *
 438      * <p>ObjectInputStream subclasses which override this method can only be
 439      * constructed in security contexts possessing the
 440      * "enableSubclassImplementation" SerializablePermission; any attempt to
 441      * instantiate such a subclass without this permission will cause a
 442      * SecurityException to be thrown.
 443      *
 444      * @return  reference to deserialized object
 445      * @throws  ClassNotFoundException if class of an object to deserialize
 446      *          cannot be found
 447      * @throws  StreamCorruptedException if control information in the stream
 448      *          is inconsistent
 449      * @throws  ObjectStreamException if object to deserialize has already
 450      *          appeared in stream
 451      * @throws  OptionalDataException if primitive data is next in stream
 452      * @throws  IOException if an I/O error occurs during deserialization
 453      * @since   1.4
 454      */
 455     public Object readUnshared() throws IOException, ClassNotFoundException {
 456         // if nested read, passHandle contains handle of enclosing object
 457         int outerHandle = passHandle;
 458         try {
 459             Object obj = readObject0(true);
 460             handles.markDependency(outerHandle, passHandle);
 461             ClassNotFoundException ex = handles.lookupException(passHandle);
 462             if (ex != null) {
 463                 throw ex;
 464             }
 465             if (depth == 0) {
 466                 vlist.doCallbacks();
 467             }
 468             return obj;
 469         } finally {
 470             passHandle = outerHandle;
 471             if (closed && depth == 0) {
 472                 clear();
 473             }
 474         }
 475     }
 476 
 477     /**
 478      * Read the non-static and non-transient fields of the current class from
 479      * this stream.  This may only be called from the readObject method of the
 480      * class being deserialized. It will throw the NotActiveException if it is
 481      * called otherwise.
 482      *
 483      * @throws  ClassNotFoundException if the class of a serialized object
 484      *          could not be found.
 485      * @throws  IOException if an I/O error occurs.
 486      * @throws  NotActiveException if the stream is not currently reading
 487      *          objects.
 488      */
 489     public void defaultReadObject()
 490         throws IOException, ClassNotFoundException
 491     {
 492         if (curContext == null) {
 493             throw new NotActiveException("not in call to readObject");
 494         }
 495         Object curObj = curContext.getObj();
 496         ObjectStreamClass curDesc = curContext.getDesc();
 497         bin.setBlockDataMode(false);
 498         defaultReadFields(curObj, curDesc);
 499         bin.setBlockDataMode(true);
 500         if (!curDesc.hasWriteObjectData()) {
 501             /*
 502              * Fix for 4360508: since stream does not contain terminating
 503              * TC_ENDBLOCKDATA tag, set flag so that reading code elsewhere
 504              * knows to simulate end-of-custom-data behavior.
 505              */
 506             defaultDataEnd = true;
 507         }
 508         ClassNotFoundException ex = handles.lookupException(passHandle);
 509         if (ex != null) {
 510             throw ex;
 511         }
 512     }
 513 
 514     /**
 515      * Reads the persistent fields from the stream and makes them available by
 516      * name.
 517      *
 518      * @return  the <code>GetField</code> object representing the persistent
 519      *          fields of the object being deserialized
 520      * @throws  ClassNotFoundException if the class of a serialized object
 521      *          could not be found.
 522      * @throws  IOException if an I/O error occurs.
 523      * @throws  NotActiveException if the stream is not currently reading
 524      *          objects.
 525      * @since 1.2
 526      */
 527     public ObjectInputStream.GetField readFields()
 528         throws IOException, ClassNotFoundException
 529     {
 530         if (curContext == null) {
 531             throw new NotActiveException("not in call to readObject");
 532         }
 533         Object curObj = curContext.getObj();
 534         ObjectStreamClass curDesc = curContext.getDesc();
 535         bin.setBlockDataMode(false);
 536         GetFieldImpl getField = new GetFieldImpl(curDesc);
 537         getField.readFields();
 538         bin.setBlockDataMode(true);
 539         if (!curDesc.hasWriteObjectData()) {
 540             /*
 541              * Fix for 4360508: since stream does not contain terminating
 542              * TC_ENDBLOCKDATA tag, set flag so that reading code elsewhere
 543              * knows to simulate end-of-custom-data behavior.
 544              */
 545             defaultDataEnd = true;
 546         }
 547 
 548         return getField;
 549     }
 550 
 551     /**
 552      * Register an object to be validated before the graph is returned.  While
 553      * similar to resolveObject these validations are called after the entire
 554      * graph has been reconstituted.  Typically, a readObject method will
 555      * register the object with the stream so that when all of the objects are
 556      * restored a final set of validations can be performed.
 557      *
 558      * @param   obj the object to receive the validation callback.
 559      * @param   prio controls the order of callbacks;zero is a good default.
 560      *          Use higher numbers to be called back earlier, lower numbers for
 561      *          later callbacks. Within a priority, callbacks are processed in
 562      *          no particular order.
 563      * @throws  NotActiveException The stream is not currently reading objects
 564      *          so it is invalid to register a callback.
 565      * @throws  InvalidObjectException The validation object is null.
 566      */
 567     public void registerValidation(ObjectInputValidation obj, int prio)
 568         throws NotActiveException, InvalidObjectException
 569     {
 570         if (depth == 0) {
 571             throw new NotActiveException("stream inactive");
 572         }
 573         vlist.register(obj, prio);
 574     }
 575 
 576     /**
 577      * Load the local class equivalent of the specified stream class
 578      * description.  Subclasses may implement this method to allow classes to
 579      * be fetched from an alternate source.
 580      *
 581      * <p>The corresponding method in <code>ObjectOutputStream</code> is
 582      * <code>annotateClass</code>.  This method will be invoked only once for
 583      * each unique class in the stream.  This method can be implemented by
 584      * subclasses to use an alternate loading mechanism but must return a
 585      * <code>Class</code> object. Once returned, if the class is not an array
 586      * class, its serialVersionUID is compared to the serialVersionUID of the
 587      * serialized class, and if there is a mismatch, the deserialization fails
 588      * and an {@link InvalidClassException} is thrown.
 589      *
 590      * <p>The default implementation of this method in
 591      * <code>ObjectInputStream</code> returns the result of calling
 592      * <pre>
 593      *     Class.forName(desc.getName(), false, loader)
 594      * </pre>
 595      * where <code>loader</code> is determined as follows: if there is a
 596      * method on the current thread's stack whose declaring class was
 597      * defined by a user-defined class loader (and was not a generated to
 598      * implement reflective invocations), then <code>loader</code> is class
 599      * loader corresponding to the closest such method to the currently
 600      * executing frame; otherwise, <code>loader</code> is
 601      * <code>null</code>. If this call results in a
 602      * <code>ClassNotFoundException</code> and the name of the passed
 603      * <code>ObjectStreamClass</code> instance is the Java language keyword
 604      * for a primitive type or void, then the <code>Class</code> object
 605      * representing that primitive type or void will be returned
 606      * (e.g., an <code>ObjectStreamClass</code> with the name
 607      * <code>"int"</code> will be resolved to <code>Integer.TYPE</code>).
 608      * Otherwise, the <code>ClassNotFoundException</code> will be thrown to
 609      * the caller of this method.
 610      *
 611      * @param   desc an instance of class <code>ObjectStreamClass</code>
 612      * @return  a <code>Class</code> object corresponding to <code>desc</code>
 613      * @throws  IOException any of the usual Input/Output exceptions.
 614      * @throws  ClassNotFoundException if class of a serialized object cannot
 615      *          be found.
 616      */
 617     protected Class<?> resolveClass(ObjectStreamClass desc)
 618         throws IOException, ClassNotFoundException
 619     {
 620         String name = desc.getName();
 621         try {
 622             return Class.forName(name, false, latestUserDefinedLoader());
 623         } catch (ClassNotFoundException ex) {
 624             Class<?> cl = primClasses.get(name);
 625             if (cl != null) {
 626                 return cl;
 627             } else {
 628                 throw ex;
 629             }
 630         }
 631     }
 632 
 633     /**
 634      * Returns a proxy class that implements the interfaces named in a proxy
 635      * class descriptor; subclasses may implement this method to read custom
 636      * data from the stream along with the descriptors for dynamic proxy
 637      * classes, allowing them to use an alternate loading mechanism for the
 638      * interfaces and the proxy class.
 639      *
 640      * <p>This method is called exactly once for each unique proxy class
 641      * descriptor in the stream.
 642      *
 643      * <p>The corresponding method in <code>ObjectOutputStream</code> is
 644      * <code>annotateProxyClass</code>.  For a given subclass of
 645      * <code>ObjectInputStream</code> that overrides this method, the
 646      * <code>annotateProxyClass</code> method in the corresponding subclass of
 647      * <code>ObjectOutputStream</code> must write any data or objects read by
 648      * this method.
 649      *
 650      * <p>The default implementation of this method in
 651      * <code>ObjectInputStream</code> returns the result of calling
 652      * <code>Proxy.getProxyClass</code> with the list of <code>Class</code>
 653      * objects for the interfaces that are named in the <code>interfaces</code>
 654      * parameter.  The <code>Class</code> object for each interface name
 655      * <code>i</code> is the value returned by calling
 656      * <pre>
 657      *     Class.forName(i, false, loader)
 658      * </pre>
 659      * where <code>loader</code> is that of the first non-<code>null</code>
 660      * class loader up the execution stack, or <code>null</code> if no
 661      * non-<code>null</code> class loaders are on the stack (the same class
 662      * loader choice used by the <code>resolveClass</code> method).  Unless any
 663      * of the resolved interfaces are non-public, this same value of
 664      * <code>loader</code> is also the class loader passed to
 665      * <code>Proxy.getProxyClass</code>; if non-public interfaces are present,
 666      * their class loader is passed instead (if more than one non-public
 667      * interface class loader is encountered, an
 668      * <code>IllegalAccessError</code> is thrown).
 669      * If <code>Proxy.getProxyClass</code> throws an
 670      * <code>IllegalArgumentException</code>, <code>resolveProxyClass</code>
 671      * will throw a <code>ClassNotFoundException</code> containing the
 672      * <code>IllegalArgumentException</code>.
 673      *
 674      * @param interfaces the list of interface names that were
 675      *                deserialized in the proxy class descriptor
 676      * @return  a proxy class for the specified interfaces
 677      * @throws        IOException any exception thrown by the underlying
 678      *                <code>InputStream</code>
 679      * @throws        ClassNotFoundException if the proxy class or any of the
 680      *                named interfaces could not be found
 681      * @see ObjectOutputStream#annotateProxyClass(Class)
 682      * @since 1.3
 683      */
 684     protected Class<?> resolveProxyClass(String[] interfaces)
 685         throws IOException, ClassNotFoundException
 686     {
 687         ClassLoader latestLoader = latestUserDefinedLoader();
 688         ClassLoader nonPublicLoader = null;
 689         boolean hasNonPublicInterface = false;
 690 
 691         // define proxy in class loader of non-public interface(s), if any
 692         Class[] classObjs = new Class[interfaces.length];
 693         for (int i = 0; i < interfaces.length; i++) {
 694             Class cl = Class.forName(interfaces[i], false, latestLoader);
 695             if ((cl.getModifiers() & Modifier.PUBLIC) == 0) {
 696                 if (hasNonPublicInterface) {
 697                     if (nonPublicLoader != cl.getClassLoader()) {
 698                         throw new IllegalAccessError(
 699                             "conflicting non-public interface class loaders");
 700                     }
 701                 } else {
 702                     nonPublicLoader = cl.getClassLoader();
 703                     hasNonPublicInterface = true;
 704                 }
 705             }
 706             classObjs[i] = cl;
 707         }
 708         try {
 709             return Proxy.getProxyClass(
 710                 hasNonPublicInterface ? nonPublicLoader : latestLoader,
 711                 classObjs);
 712         } catch (IllegalArgumentException e) {
 713             throw new ClassNotFoundException(null, e);
 714         }
 715     }
 716 
 717     /**
 718      * This method will allow trusted subclasses of ObjectInputStream to
 719      * substitute one object for another during deserialization. Replacing
 720      * objects is disabled until enableResolveObject is called. The
 721      * enableResolveObject method checks that the stream requesting to resolve
 722      * object can be trusted. Every reference to serializable objects is passed
 723      * to resolveObject.  To insure that the private state of objects is not
 724      * unintentionally exposed only trusted streams may use resolveObject.
 725      *
 726      * <p>This method is called after an object has been read but before it is
 727      * returned from readObject.  The default resolveObject method just returns
 728      * the same object.
 729      *
 730      * <p>When a subclass is replacing objects it must insure that the
 731      * substituted object is compatible with every field where the reference
 732      * will be stored.  Objects whose type is not a subclass of the type of the
 733      * field or array element abort the serialization by raising an exception
 734      * and the object is not be stored.
 735      *
 736      * <p>This method is called only once when each object is first
 737      * encountered.  All subsequent references to the object will be redirected
 738      * to the new object.
 739      *
 740      * @param   obj object to be substituted
 741      * @return  the substituted object
 742      * @throws  IOException Any of the usual Input/Output exceptions.
 743      */
 744     protected Object resolveObject(Object obj) throws IOException {
 745         return obj;
 746     }
 747 
 748     /**
 749      * Enable the stream to allow objects read from the stream to be replaced.
 750      * When enabled, the resolveObject method is called for every object being
 751      * deserialized.
 752      *
 753      * <p>If <i>enable</i> is true, and there is a security manager installed,
 754      * this method first calls the security manager's
 755      * <code>checkPermission</code> method with the
 756      * <code>SerializablePermission("enableSubstitution")</code> permission to
 757      * ensure it's ok to enable the stream to allow objects read from the
 758      * stream to be replaced.
 759      *
 760      * @param   enable true for enabling use of <code>resolveObject</code> for
 761      *          every object being deserialized
 762      * @return  the previous setting before this method was invoked
 763      * @throws  SecurityException if a security manager exists and its
 764      *          <code>checkPermission</code> method denies enabling the stream
 765      *          to allow objects read from the stream to be replaced.
 766      * @see SecurityManager#checkPermission
 767      * @see java.io.SerializablePermission
 768      */
 769     protected boolean enableResolveObject(boolean enable)
 770         throws SecurityException
 771     {
 772         if (enable == enableResolve) {
 773             return enable;
 774         }
 775         if (enable) {
 776             SecurityManager sm = System.getSecurityManager();
 777             if (sm != null) {
 778                 sm.checkPermission(SUBSTITUTION_PERMISSION);
 779             }
 780         }
 781         enableResolve = enable;
 782         return !enableResolve;
 783     }
 784 
 785     /**
 786      * The readStreamHeader method is provided to allow subclasses to read and
 787      * verify their own stream headers. It reads and verifies the magic number
 788      * and version number.
 789      *
 790      * @throws  IOException if there are I/O errors while reading from the
 791      *          underlying <code>InputStream</code>
 792      * @throws  StreamCorruptedException if control information in the stream
 793      *          is inconsistent
 794      */
 795     protected void readStreamHeader()
 796         throws IOException, StreamCorruptedException
 797     {
 798         short s0 = bin.readShort();
 799         short s1 = bin.readShort();
 800         if (s0 != STREAM_MAGIC || s1 != STREAM_VERSION) {
 801             throw new StreamCorruptedException(
 802                 String.format("invalid stream header: %04X%04X", s0, s1));
 803         }
 804     }
 805 
 806     /**
 807      * Read a class descriptor from the serialization stream.  This method is
 808      * called when the ObjectInputStream expects a class descriptor as the next
 809      * item in the serialization stream.  Subclasses of ObjectInputStream may
 810      * override this method to read in class descriptors that have been written
 811      * in non-standard formats (by subclasses of ObjectOutputStream which have
 812      * overridden the <code>writeClassDescriptor</code> method).  By default,
 813      * this method reads class descriptors according to the format defined in
 814      * the Object Serialization specification.
 815      *
 816      * @return  the class descriptor read
 817      * @throws  IOException If an I/O error has occurred.
 818      * @throws  ClassNotFoundException If the Class of a serialized object used
 819      *          in the class descriptor representation cannot be found
 820      * @see java.io.ObjectOutputStream#writeClassDescriptor(java.io.ObjectStreamClass)
 821      * @since 1.3
 822      */
 823     protected ObjectStreamClass readClassDescriptor()
 824         throws IOException, ClassNotFoundException
 825     {
 826         ObjectStreamClass desc = new ObjectStreamClass();
 827         desc.readNonProxy(this);
 828         return desc;
 829     }
 830 
 831     /**
 832      * Reads a byte of data. This method will block if no input is available.
 833      *
 834      * @return  the byte read, or -1 if the end of the stream is reached.
 835      * @throws  IOException If an I/O error has occurred.
 836      */
 837     public int read() throws IOException {
 838         return bin.read();
 839     }
 840 
 841     /**
 842      * Reads into an array of bytes.  This method will block until some input
 843      * is available. Consider using java.io.DataInputStream.readFully to read
 844      * exactly 'length' bytes.
 845      *
 846      * @param   buf the buffer into which the data is read
 847      * @param   off the start offset of the data
 848      * @param   len the maximum number of bytes read
 849      * @return  the actual number of bytes read, -1 is returned when the end of
 850      *          the stream is reached.
 851      * @throws  IOException If an I/O error has occurred.
 852      * @see java.io.DataInputStream#readFully(byte[],int,int)
 853      */
 854     public int read(byte[] buf, int off, int len) throws IOException {
 855         if (buf == null) {
 856             throw new NullPointerException();
 857         }
 858         int endoff = off + len;
 859         if (off < 0 || len < 0 || endoff > buf.length || endoff < 0) {
 860             throw new IndexOutOfBoundsException();
 861         }
 862         return bin.read(buf, off, len, false);
 863     }
 864 
 865     /**
 866      * Returns the number of bytes that can be read without blocking.
 867      *
 868      * @return  the number of available bytes.
 869      * @throws  IOException if there are I/O errors while reading from the
 870      *          underlying <code>InputStream</code>
 871      */
 872     public int available() throws IOException {
 873         return bin.available();
 874     }
 875 
 876     /**
 877      * Closes the input stream. Must be called to release any resources
 878      * associated with the stream.
 879      *
 880      * @throws  IOException If an I/O error has occurred.
 881      */
 882     public void close() throws IOException {
 883         /*
 884          * Even if stream already closed, propagate redundant close to
 885          * underlying stream to stay consistent with previous implementations.
 886          */
 887         closed = true;
 888         if (depth == 0) {
 889             clear();
 890         }
 891         bin.close();
 892     }
 893 
 894     /**
 895      * Reads in a boolean.
 896      *
 897      * @return  the boolean read.
 898      * @throws  EOFException If end of file is reached.
 899      * @throws  IOException If other I/O error has occurred.
 900      */
 901     public boolean readBoolean() throws IOException {
 902         return bin.readBoolean();
 903     }
 904 
 905     /**
 906      * Reads an 8 bit byte.
 907      *
 908      * @return  the 8 bit byte read.
 909      * @throws  EOFException If end of file is reached.
 910      * @throws  IOException If other I/O error has occurred.
 911      */
 912     public byte readByte() throws IOException  {
 913         return bin.readByte();
 914     }
 915 
 916     /**
 917      * Reads an unsigned 8 bit byte.
 918      *
 919      * @return  the 8 bit byte read.
 920      * @throws  EOFException If end of file is reached.
 921      * @throws  IOException If other I/O error has occurred.
 922      */
 923     public int readUnsignedByte()  throws IOException {
 924         return bin.readUnsignedByte();
 925     }
 926 
 927     /**
 928      * Reads a 16 bit char.
 929      *
 930      * @return  the 16 bit char read.
 931      * @throws  EOFException If end of file is reached.
 932      * @throws  IOException If other I/O error has occurred.
 933      */
 934     public char readChar()  throws IOException {
 935         return bin.readChar();
 936     }
 937 
 938     /**
 939      * Reads a 16 bit short.
 940      *
 941      * @return  the 16 bit short read.
 942      * @throws  EOFException If end of file is reached.
 943      * @throws  IOException If other I/O error has occurred.
 944      */
 945     public short readShort()  throws IOException {
 946         return bin.readShort();
 947     }
 948 
 949     /**
 950      * Reads an unsigned 16 bit short.
 951      *
 952      * @return  the 16 bit short read.
 953      * @throws  EOFException If end of file is reached.
 954      * @throws  IOException If other I/O error has occurred.
 955      */
 956     public int readUnsignedShort() throws IOException {
 957         return bin.readUnsignedShort();
 958     }
 959 
 960     /**
 961      * Reads a 32 bit int.
 962      *
 963      * @return  the 32 bit integer read.
 964      * @throws  EOFException If end of file is reached.
 965      * @throws  IOException If other I/O error has occurred.
 966      */
 967     public int readInt()  throws IOException {
 968         return bin.readInt();
 969     }
 970 
 971     /**
 972      * Reads a 64 bit long.
 973      *
 974      * @return  the read 64 bit long.
 975      * @throws  EOFException If end of file is reached.
 976      * @throws  IOException If other I/O error has occurred.
 977      */
 978     public long readLong()  throws IOException {
 979         return bin.readLong();
 980     }
 981 
 982     /**
 983      * Reads a 32 bit float.
 984      *
 985      * @return  the 32 bit float read.
 986      * @throws  EOFException If end of file is reached.
 987      * @throws  IOException If other I/O error has occurred.
 988      */
 989     public float readFloat() throws IOException {
 990         return bin.readFloat();
 991     }
 992 
 993     /**
 994      * Reads a 64 bit double.
 995      *
 996      * @return  the 64 bit double read.
 997      * @throws  EOFException If end of file is reached.
 998      * @throws  IOException If other I/O error has occurred.
 999      */
1000     public double readDouble() throws IOException {
1001         return bin.readDouble();
1002     }
1003 
1004     /**
1005      * Reads bytes, blocking until all bytes are read.
1006      *
1007      * @param   buf the buffer into which the data is read
1008      * @throws  EOFException If end of file is reached.
1009      * @throws  IOException If other I/O error has occurred.
1010      */
1011     public void readFully(byte[] buf) throws IOException {
1012         bin.readFully(buf, 0, buf.length, false);
1013     }
1014 
1015     /**
1016      * Reads bytes, blocking until all bytes are read.
1017      *
1018      * @param   buf the buffer into which the data is read
1019      * @param   off the start offset of the data
1020      * @param   len the maximum number of bytes to read
1021      * @throws  EOFException If end of file is reached.
1022      * @throws  IOException If other I/O error has occurred.
1023      */
1024     public void readFully(byte[] buf, int off, int len) throws IOException {
1025         int endoff = off + len;
1026         if (off < 0 || len < 0 || endoff > buf.length || endoff < 0) {
1027             throw new IndexOutOfBoundsException();
1028         }
1029         bin.readFully(buf, off, len, false);
1030     }
1031 
1032     /**
1033      * Skips bytes.
1034      *
1035      * @param   len the number of bytes to be skipped
1036      * @return  the actual number of bytes skipped.
1037      * @throws  IOException If an I/O error has occurred.
1038      */
1039     public int skipBytes(int len) throws IOException {
1040         return bin.skipBytes(len);
1041     }
1042 
1043     /**
1044      * Reads in a line that has been terminated by a \n, \r, \r\n or EOF.
1045      *
1046      * @return  a String copy of the line.
1047      * @throws  IOException if there are I/O errors while reading from the
1048      *          underlying <code>InputStream</code>
1049      * @deprecated This method does not properly convert bytes to characters.
1050      *          see DataInputStream for the details and alternatives.
1051      */
1052     @Deprecated
1053     public String readLine() throws IOException {
1054         return bin.readLine();
1055     }
1056 
1057     /**
1058      * Reads a String in
1059      * <a href="DataInput.html#modified-utf-8">modified UTF-8</a>
1060      * format.
1061      *
1062      * @return  the String.
1063      * @throws  IOException if there are I/O errors while reading from the
1064      *          underlying <code>InputStream</code>
1065      * @throws  UTFDataFormatException if read bytes do not represent a valid
1066      *          modified UTF-8 encoding of a string
1067      */
1068     public String readUTF() throws IOException {
1069         return bin.readUTF();
1070     }
1071 
1072     /**
1073      * Provide access to the persistent fields read from the input stream.
1074      */
1075     public static abstract class GetField {
1076 
1077         /**
1078          * Get the ObjectStreamClass that describes the fields in the stream.
1079          *
1080          * @return  the descriptor class that describes the serializable fields
1081          */
1082         public abstract ObjectStreamClass getObjectStreamClass();
1083 
1084         /**
1085          * Return true if the named field is defaulted and has no value in this
1086          * stream.
1087          *
1088          * @param  name the name of the field
1089          * @return true, if and only if the named field is defaulted
1090          * @throws IOException if there are I/O errors while reading from
1091          *         the underlying <code>InputStream</code>
1092          * @throws IllegalArgumentException if <code>name</code> does not
1093          *         correspond to a serializable field
1094          */
1095         public abstract boolean defaulted(String name) throws IOException;
1096 
1097         /**
1098          * Get the value of the named boolean field from the persistent field.
1099          *
1100          * @param  name the name of the field
1101          * @param  val the default value to use if <code>name</code> does not
1102          *         have a value
1103          * @return the value of the named <code>boolean</code> field
1104          * @throws IOException if there are I/O errors while reading from the
1105          *         underlying <code>InputStream</code>
1106          * @throws IllegalArgumentException if type of <code>name</code> is
1107          *         not serializable or if the field type is incorrect
1108          */
1109         public abstract boolean get(String name, boolean val)
1110             throws IOException;
1111 
1112         /**
1113          * Get the value of the named byte field from the persistent field.
1114          *
1115          * @param  name the name of the field
1116          * @param  val the default value to use if <code>name</code> does not
1117          *         have a value
1118          * @return the value of the named <code>byte</code> field
1119          * @throws IOException if there are I/O errors while reading from the
1120          *         underlying <code>InputStream</code>
1121          * @throws IllegalArgumentException if type of <code>name</code> is
1122          *         not serializable or if the field type is incorrect
1123          */
1124         public abstract byte get(String name, byte val) throws IOException;
1125 
1126         /**
1127          * Get the value of the named char field from the persistent field.
1128          *
1129          * @param  name the name of the field
1130          * @param  val the default value to use if <code>name</code> does not
1131          *         have a value
1132          * @return the value of the named <code>char</code> field
1133          * @throws IOException if there are I/O errors while reading from the
1134          *         underlying <code>InputStream</code>
1135          * @throws IllegalArgumentException if type of <code>name</code> is
1136          *         not serializable or if the field type is incorrect
1137          */
1138         public abstract char get(String name, char val) throws IOException;
1139 
1140         /**
1141          * Get the value of the named short field from the persistent field.
1142          *
1143          * @param  name the name of the field
1144          * @param  val the default value to use if <code>name</code> does not
1145          *         have a value
1146          * @return the value of the named <code>short</code> field
1147          * @throws IOException if there are I/O errors while reading from the
1148          *         underlying <code>InputStream</code>
1149          * @throws IllegalArgumentException if type of <code>name</code> is
1150          *         not serializable or if the field type is incorrect
1151          */
1152         public abstract short get(String name, short val) throws IOException;
1153 
1154         /**
1155          * Get the value of the named int field from the persistent field.
1156          *
1157          * @param  name the name of the field
1158          * @param  val the default value to use if <code>name</code> does not
1159          *         have a value
1160          * @return the value of the named <code>int</code> field
1161          * @throws IOException if there are I/O errors while reading from the
1162          *         underlying <code>InputStream</code>
1163          * @throws IllegalArgumentException if type of <code>name</code> is
1164          *         not serializable or if the field type is incorrect
1165          */
1166         public abstract int get(String name, int val) throws IOException;
1167 
1168         /**
1169          * Get the value of the named long field from the persistent field.
1170          *
1171          * @param  name the name of the field
1172          * @param  val the default value to use if <code>name</code> does not
1173          *         have a value
1174          * @return the value of the named <code>long</code> field
1175          * @throws IOException if there are I/O errors while reading from the
1176          *         underlying <code>InputStream</code>
1177          * @throws IllegalArgumentException if type of <code>name</code> is
1178          *         not serializable or if the field type is incorrect
1179          */
1180         public abstract long get(String name, long val) throws IOException;
1181 
1182         /**
1183          * Get the value of the named float field from the persistent field.
1184          *
1185          * @param  name the name of the field
1186          * @param  val the default value to use if <code>name</code> does not
1187          *         have a value
1188          * @return the value of the named <code>float</code> field
1189          * @throws IOException if there are I/O errors while reading from the
1190          *         underlying <code>InputStream</code>
1191          * @throws IllegalArgumentException if type of <code>name</code> is
1192          *         not serializable or if the field type is incorrect
1193          */
1194         public abstract float get(String name, float val) throws IOException;
1195 
1196         /**
1197          * Get the value of the named double field from the persistent field.
1198          *
1199          * @param  name the name of the field
1200          * @param  val the default value to use if <code>name</code> does not
1201          *         have a value
1202          * @return the value of the named <code>double</code> field
1203          * @throws IOException if there are I/O errors while reading from the
1204          *         underlying <code>InputStream</code>
1205          * @throws IllegalArgumentException if type of <code>name</code> is
1206          *         not serializable or if the field type is incorrect
1207          */
1208         public abstract double get(String name, double val) throws IOException;
1209 
1210         /**
1211          * Get the value of the named Object field from the persistent field.
1212          *
1213          * @param  name the name of the field
1214          * @param  val the default value to use if <code>name</code> does not
1215          *         have a value
1216          * @return the value of the named <code>Object</code> field
1217          * @throws IOException if there are I/O errors while reading from the
1218          *         underlying <code>InputStream</code>
1219          * @throws IllegalArgumentException if type of <code>name</code> is
1220          *         not serializable or if the field type is incorrect
1221          */
1222         public abstract Object get(String name, Object val) throws IOException;
1223     }
1224 
1225     /**
1226      * Verifies that this (possibly subclass) instance can be constructed
1227      * without violating security constraints: the subclass must not override
1228      * security-sensitive non-final methods, or else the
1229      * "enableSubclassImplementation" SerializablePermission is checked.
1230      */
1231     private void verifySubclass() {
1232         Class cl = getClass();
1233         if (cl == ObjectInputStream.class) {
1234             return;
1235         }
1236         SecurityManager sm = System.getSecurityManager();
1237         if (sm == null) {
1238             return;
1239         }
1240         processQueue(Caches.subclassAuditsQueue, Caches.subclassAudits);
1241         WeakClassKey key = new WeakClassKey(cl, Caches.subclassAuditsQueue);
1242         Boolean result = Caches.subclassAudits.get(key);
1243         if (result == null) {
1244             result = Boolean.valueOf(auditSubclass(cl));
1245             Caches.subclassAudits.putIfAbsent(key, result);
1246         }
1247         if (result.booleanValue()) {
1248             return;
1249         }
1250         sm.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
1251     }
1252 
1253     /**
1254      * Performs reflective checks on given subclass to verify that it doesn't
1255      * override security-sensitive non-final methods.  Returns true if subclass
1256      * is "safe", false otherwise.
1257      */
1258     private static boolean auditSubclass(final Class<?> subcl) {
1259         Boolean result = AccessController.doPrivileged(
1260             new PrivilegedAction<Boolean>() {
1261                 public Boolean run() {
1262                     for (Class<?> cl = subcl;
1263                          cl != ObjectInputStream.class;
1264                          cl = cl.getSuperclass())
1265                     {
1266                         try {
1267                             cl.getDeclaredMethod(
1268                                 "readUnshared", (Class[]) null);
1269                             return Boolean.FALSE;
1270                         } catch (NoSuchMethodException ex) {
1271                         }
1272                         try {
1273                             cl.getDeclaredMethod("readFields", (Class[]) null);
1274                             return Boolean.FALSE;
1275                         } catch (NoSuchMethodException ex) {
1276                         }
1277                     }
1278                     return Boolean.TRUE;
1279                 }
1280             }
1281         );
1282         return result.booleanValue();
1283     }
1284 
1285     /**
1286      * Clears internal data structures.
1287      */
1288     private void clear() {
1289         handles.clear();
1290         vlist.clear();
1291     }
1292 
1293     /**
1294      * Underlying readObject implementation.
1295      */
1296     private Object readObject0(boolean unshared) throws IOException {
1297         boolean oldMode = bin.getBlockDataMode();
1298         if (oldMode) {
1299             int remain = bin.currentBlockRemaining();
1300             if (remain > 0) {
1301                 throw new OptionalDataException(remain);
1302             } else if (defaultDataEnd) {
1303                 /*
1304                  * Fix for 4360508: stream is currently at the end of a field
1305                  * value block written via default serialization; since there
1306                  * is no terminating TC_ENDBLOCKDATA tag, simulate
1307                  * end-of-custom-data behavior explicitly.
1308                  */
1309                 throw new OptionalDataException(true);
1310             }
1311             bin.setBlockDataMode(false);
1312         }
1313 
1314         byte tc;
1315         while ((tc = bin.peekByte()) == TC_RESET) {
1316             bin.readByte();
1317             handleReset();
1318         }
1319 
1320         depth++;
1321         try {
1322             switch (tc) {
1323                 case TC_NULL:
1324                     return readNull();
1325 
1326                 case TC_REFERENCE:
1327                     return readHandle(unshared);
1328 
1329                 case TC_CLASS:
1330                     return readClass(unshared);
1331 
1332                 case TC_CLASSDESC:
1333                 case TC_PROXYCLASSDESC:
1334                     return readClassDesc(unshared);
1335 
1336                 case TC_STRING:
1337                 case TC_LONGSTRING:
1338                     return checkResolve(readString(unshared));
1339 
1340                 case TC_ARRAY:
1341                     return checkResolve(readArray(unshared));
1342 
1343                 case TC_ENUM:
1344                     return checkResolve(readEnum(unshared));
1345 
1346                 case TC_OBJECT:
1347                     return checkResolve(readOrdinaryObject(unshared));
1348 
1349                 case TC_EXCEPTION:
1350                     IOException ex = readFatalException();
1351                     throw new WriteAbortedException("writing aborted", ex);
1352 
1353                 case TC_BLOCKDATA:
1354                 case TC_BLOCKDATALONG:
1355                     if (oldMode) {
1356                         bin.setBlockDataMode(true);
1357                         bin.peek();             // force header read
1358                         throw new OptionalDataException(
1359                             bin.currentBlockRemaining());
1360                     } else {
1361                         throw new StreamCorruptedException(
1362                             "unexpected block data");
1363                     }
1364 
1365                 case TC_ENDBLOCKDATA:
1366                     if (oldMode) {
1367                         throw new OptionalDataException(true);
1368                     } else {
1369                         throw new StreamCorruptedException(
1370                             "unexpected end of block data");
1371                     }
1372 
1373                 default:
1374                     throw new StreamCorruptedException(
1375                         String.format("invalid type code: %02X", tc));
1376             }
1377         } finally {
1378             depth--;
1379             bin.setBlockDataMode(oldMode);
1380         }
1381     }
1382 
1383     /**
1384      * If resolveObject has been enabled and given object does not have an
1385      * exception associated with it, calls resolveObject to determine
1386      * replacement for object, and updates handle table accordingly.  Returns
1387      * replacement object, or echoes provided object if no replacement
1388      * occurred.  Expects that passHandle is set to given object's handle prior
1389      * to calling this method.
1390      */
1391     private Object checkResolve(Object obj) throws IOException {
1392         if (!enableResolve || handles.lookupException(passHandle) != null) {
1393             return obj;
1394         }
1395         Object rep = resolveObject(obj);
1396         if (rep != obj) {
1397             handles.setObject(passHandle, rep);
1398         }
1399         return rep;
1400     }
1401 
1402     /**
1403      * Reads string without allowing it to be replaced in stream.  Called from
1404      * within ObjectStreamClass.read().
1405      */
1406     String readTypeString() throws IOException {
1407         int oldHandle = passHandle;
1408         try {
1409             byte tc = bin.peekByte();
1410             switch (tc) {
1411                 case TC_NULL:
1412                     return (String) readNull();
1413 
1414                 case TC_REFERENCE:
1415                     return (String) readHandle(false);
1416 
1417                 case TC_STRING:
1418                 case TC_LONGSTRING:
1419                     return readString(false);
1420 
1421                 default:
1422                     throw new StreamCorruptedException(
1423                         String.format("invalid type code: %02X", tc));
1424             }
1425         } finally {
1426             passHandle = oldHandle;
1427         }
1428     }
1429 
1430     /**
1431      * Reads in null code, sets passHandle to NULL_HANDLE and returns null.
1432      */
1433     private Object readNull() throws IOException {
1434         if (bin.readByte() != TC_NULL) {
1435             throw new InternalError();
1436         }
1437         passHandle = NULL_HANDLE;
1438         return null;
1439     }
1440 
1441     /**
1442      * Reads in object handle, sets passHandle to the read handle, and returns
1443      * object associated with the handle.
1444      */
1445     private Object readHandle(boolean unshared) throws IOException {
1446         if (bin.readByte() != TC_REFERENCE) {
1447             throw new InternalError();
1448         }
1449         passHandle = bin.readInt() - baseWireHandle;
1450         if (passHandle < 0 || passHandle >= handles.size()) {
1451             throw new StreamCorruptedException(
1452                 String.format("invalid handle value: %08X", passHandle +
1453                 baseWireHandle));
1454         }
1455         if (unshared) {
1456             // REMIND: what type of exception to throw here?
1457             throw new InvalidObjectException(
1458                 "cannot read back reference as unshared");
1459         }
1460 
1461         Object obj = handles.lookupObject(passHandle);
1462         if (obj == unsharedMarker) {
1463             // REMIND: what type of exception to throw here?
1464             throw new InvalidObjectException(
1465                 "cannot read back reference to unshared object");
1466         }
1467         return obj;
1468     }
1469 
1470     /**
1471      * Reads in and returns class object.  Sets passHandle to class object's
1472      * assigned handle.  Returns null if class is unresolvable (in which case a
1473      * ClassNotFoundException will be associated with the class' handle in the
1474      * handle table).
1475      */
1476     private Class readClass(boolean unshared) throws IOException {
1477         if (bin.readByte() != TC_CLASS) {
1478             throw new InternalError();
1479         }
1480         ObjectStreamClass desc = readClassDesc(false);
1481         Class cl = desc.forClass();
1482         passHandle = handles.assign(unshared ? unsharedMarker : cl);
1483 
1484         ClassNotFoundException resolveEx = desc.getResolveException();
1485         if (resolveEx != null) {
1486             handles.markException(passHandle, resolveEx);
1487         }
1488 
1489         handles.finish(passHandle);
1490         return cl;
1491     }
1492 
1493     /**
1494      * Reads in and returns (possibly null) class descriptor.  Sets passHandle
1495      * to class descriptor's assigned handle.  If class descriptor cannot be
1496      * resolved to a class in the local VM, a ClassNotFoundException is
1497      * associated with the class descriptor's handle.
1498      */
1499     private ObjectStreamClass readClassDesc(boolean unshared)
1500         throws IOException
1501     {
1502         byte tc = bin.peekByte();
1503         switch (tc) {
1504             case TC_NULL:
1505                 return (ObjectStreamClass) readNull();
1506 
1507             case TC_REFERENCE:
1508                 return (ObjectStreamClass) readHandle(unshared);
1509 
1510             case TC_PROXYCLASSDESC:
1511                 return readProxyDesc(unshared);
1512 
1513             case TC_CLASSDESC:
1514                 return readNonProxyDesc(unshared);
1515 
1516             default:
1517                 throw new StreamCorruptedException(
1518                     String.format("invalid type code: %02X", tc));
1519         }
1520     }
1521 
1522     /**
1523      * Reads in and returns class descriptor for a dynamic proxy class.  Sets
1524      * passHandle to proxy class descriptor's assigned handle.  If proxy class
1525      * descriptor cannot be resolved to a class in the local VM, a
1526      * ClassNotFoundException is associated with the descriptor's handle.
1527      */
1528     private ObjectStreamClass readProxyDesc(boolean unshared)
1529         throws IOException
1530     {
1531         if (bin.readByte() != TC_PROXYCLASSDESC) {
1532             throw new InternalError();
1533         }
1534 
1535         ObjectStreamClass desc = new ObjectStreamClass();
1536         int descHandle = handles.assign(unshared ? unsharedMarker : desc);
1537         passHandle = NULL_HANDLE;
1538 
1539         int numIfaces = bin.readInt();
1540         String[] ifaces = new String[numIfaces];
1541         for (int i = 0; i < numIfaces; i++) {
1542             ifaces[i] = bin.readUTF();
1543         }
1544 
1545         Class cl = null;
1546         ClassNotFoundException resolveEx = null;
1547         bin.setBlockDataMode(true);
1548         try {
1549             if ((cl = resolveProxyClass(ifaces)) == null) {
1550                 resolveEx = new ClassNotFoundException("null class");
1551             }
1552         } catch (ClassNotFoundException ex) {
1553             resolveEx = ex;
1554         }
1555         skipCustomData();
1556 
1557         desc.initProxy(cl, resolveEx, readClassDesc(false));
1558 
1559         handles.finish(descHandle);
1560         passHandle = descHandle;
1561         return desc;
1562     }
1563 
1564     /**
1565      * Reads in and returns class descriptor for a class that is not a dynamic
1566      * proxy class.  Sets passHandle to class descriptor's assigned handle.  If
1567      * class descriptor cannot be resolved to a class in the local VM, a
1568      * ClassNotFoundException is associated with the descriptor's handle.
1569      */
1570     private ObjectStreamClass readNonProxyDesc(boolean unshared)
1571         throws IOException
1572     {
1573         if (bin.readByte() != TC_CLASSDESC) {
1574             throw new InternalError();
1575         }
1576 
1577         ObjectStreamClass desc = new ObjectStreamClass();
1578         int descHandle = handles.assign(unshared ? unsharedMarker : desc);
1579         passHandle = NULL_HANDLE;
1580 
1581         ObjectStreamClass readDesc = null;
1582         try {
1583             readDesc = readClassDescriptor();
1584         } catch (ClassNotFoundException ex) {
1585             throw (IOException) new InvalidClassException(
1586                 "failed to read class descriptor").initCause(ex);
1587         }
1588 
1589         Class cl = null;
1590         ClassNotFoundException resolveEx = null;
1591         bin.setBlockDataMode(true);
1592         try {
1593             if ((cl = resolveClass(readDesc)) == null) {
1594                 resolveEx = new ClassNotFoundException("null class");
1595             }
1596         } catch (ClassNotFoundException ex) {
1597             resolveEx = ex;
1598         }
1599         skipCustomData();
1600 
1601         desc.initNonProxy(readDesc, cl, resolveEx, readClassDesc(false));
1602 
1603         handles.finish(descHandle);
1604         passHandle = descHandle;
1605         return desc;
1606     }
1607 
1608     /**
1609      * Reads in and returns new string.  Sets passHandle to new string's
1610      * assigned handle.
1611      */
1612     private String readString(boolean unshared) throws IOException {
1613         String str;
1614         byte tc = bin.readByte();
1615         switch (tc) {
1616             case TC_STRING:
1617                 str = bin.readUTF();
1618                 break;
1619 
1620             case TC_LONGSTRING:
1621                 str = bin.readLongUTF();
1622                 break;
1623 
1624             default:
1625                 throw new StreamCorruptedException(
1626                     String.format("invalid type code: %02X", tc));
1627         }
1628         passHandle = handles.assign(unshared ? unsharedMarker : str);
1629         handles.finish(passHandle);
1630         return str;
1631     }
1632 
1633     /**
1634      * Reads in and returns array object, or null if array class is
1635      * unresolvable.  Sets passHandle to array's assigned handle.
1636      */
1637     private Object readArray(boolean unshared) throws IOException {
1638         if (bin.readByte() != TC_ARRAY) {
1639             throw new InternalError();
1640         }
1641 
1642         ObjectStreamClass desc = readClassDesc(false);
1643         int len = bin.readInt();
1644 
1645         Object array = null;
1646         Class cl, ccl = null;
1647         if ((cl = desc.forClass()) != null) {
1648             ccl = cl.getComponentType();
1649             array = Array.newInstance(ccl, len);
1650         }
1651 
1652         int arrayHandle = handles.assign(unshared ? unsharedMarker : array);
1653         ClassNotFoundException resolveEx = desc.getResolveException();
1654         if (resolveEx != null) {
1655             handles.markException(arrayHandle, resolveEx);
1656         }
1657 
1658         if (ccl == null) {
1659             for (int i = 0; i < len; i++) {
1660                 readObject0(false);
1661             }
1662         } else if (ccl.isPrimitive()) {
1663             if (ccl == Integer.TYPE) {
1664                 bin.readInts((int[]) array, 0, len);
1665             } else if (ccl == Byte.TYPE) {
1666                 bin.readFully((byte[]) array, 0, len, true);
1667             } else if (ccl == Long.TYPE) {
1668                 bin.readLongs((long[]) array, 0, len);
1669             } else if (ccl == Float.TYPE) {
1670                 bin.readFloats((float[]) array, 0, len);
1671             } else if (ccl == Double.TYPE) {
1672                 bin.readDoubles((double[]) array, 0, len);
1673             } else if (ccl == Short.TYPE) {
1674                 bin.readShorts((short[]) array, 0, len);
1675             } else if (ccl == Character.TYPE) {
1676                 bin.readChars((char[]) array, 0, len);
1677             } else if (ccl == Boolean.TYPE) {
1678                 bin.readBooleans((boolean[]) array, 0, len);
1679             } else {
1680                 throw new InternalError();
1681             }
1682         } else {
1683             Object[] oa = (Object[]) array;
1684             for (int i = 0; i < len; i++) {
1685                 oa[i] = readObject0(false);
1686                 handles.markDependency(arrayHandle, passHandle);
1687             }
1688         }
1689 
1690         handles.finish(arrayHandle);
1691         passHandle = arrayHandle;
1692         return array;
1693     }
1694 
1695     /**
1696      * Reads in and returns enum constant, or null if enum type is
1697      * unresolvable.  Sets passHandle to enum constant's assigned handle.
1698      */
1699     private Enum readEnum(boolean unshared) throws IOException {
1700         if (bin.readByte() != TC_ENUM) {
1701             throw new InternalError();
1702         }
1703 
1704         ObjectStreamClass desc = readClassDesc(false);
1705         if (!desc.isEnum()) {
1706             throw new InvalidClassException("non-enum class: " + desc);
1707         }
1708 
1709         int enumHandle = handles.assign(unshared ? unsharedMarker : null);
1710         ClassNotFoundException resolveEx = desc.getResolveException();
1711         if (resolveEx != null) {
1712             handles.markException(enumHandle, resolveEx);
1713         }
1714 
1715         String name = readString(false);
1716         Enum en = null;
1717         Class cl = desc.forClass();
1718         if (cl != null) {
1719             try {
1720                 en = Enum.valueOf(cl, name);
1721             } catch (IllegalArgumentException ex) {
1722                 throw (IOException) new InvalidObjectException(
1723                     "enum constant " + name + " does not exist in " +
1724                     cl).initCause(ex);
1725             }
1726             if (!unshared) {
1727                 handles.setObject(enumHandle, en);
1728             }
1729         }
1730 
1731         handles.finish(enumHandle);
1732         passHandle = enumHandle;
1733         return en;
1734     }
1735 
1736     /**
1737      * Reads and returns "ordinary" (i.e., not a String, Class,
1738      * ObjectStreamClass, array, or enum constant) object, or null if object's
1739      * class is unresolvable (in which case a ClassNotFoundException will be
1740      * associated with object's handle).  Sets passHandle to object's assigned
1741      * handle.
1742      */
1743     private Object readOrdinaryObject(boolean unshared)
1744         throws IOException
1745     {
1746         if (bin.readByte() != TC_OBJECT) {
1747             throw new InternalError();
1748         }
1749 
1750         ObjectStreamClass desc = readClassDesc(false);
1751         desc.checkDeserialize();
1752 
1753         Object obj;
1754         try {
1755             obj = desc.isInstantiable() ? desc.newInstance() : null;
1756         } catch (Exception ex) {
1757             throw (IOException) new InvalidClassException(
1758                 desc.forClass().getName(),
1759                 "unable to create instance").initCause(ex);
1760         }
1761 
1762         passHandle = handles.assign(unshared ? unsharedMarker : obj);
1763         ClassNotFoundException resolveEx = desc.getResolveException();
1764         if (resolveEx != null) {
1765             handles.markException(passHandle, resolveEx);
1766         }
1767 
1768         if (desc.isExternalizable()) {
1769             readExternalData((Externalizable) obj, desc);
1770         } else {
1771             readSerialData(obj, desc);
1772         }
1773 
1774         handles.finish(passHandle);
1775 
1776         if (obj != null &&
1777             handles.lookupException(passHandle) == null &&
1778             desc.hasReadResolveMethod())
1779         {
1780             Object rep = desc.invokeReadResolve(obj);
1781             if (unshared && rep.getClass().isArray()) {
1782                 rep = cloneArray(rep);
1783             }
1784             if (rep != obj) {
1785                 handles.setObject(passHandle, obj = rep);
1786             }
1787         }
1788 
1789         return obj;
1790     }
1791 
1792     /**
1793      * If obj is non-null, reads externalizable data by invoking readExternal()
1794      * method of obj; otherwise, attempts to skip over externalizable data.
1795      * Expects that passHandle is set to obj's handle before this method is
1796      * called.
1797      */
1798     private void readExternalData(Externalizable obj, ObjectStreamClass desc)
1799         throws IOException
1800     {
1801         SerialCallbackContext oldContext = curContext;
1802         curContext = null;
1803         try {
1804             boolean blocked = desc.hasBlockExternalData();
1805             if (blocked) {
1806                 bin.setBlockDataMode(true);
1807             }
1808             if (obj != null) {
1809                 try {
1810                     obj.readExternal(this);
1811                 } catch (ClassNotFoundException ex) {
1812                     /*
1813                      * In most cases, the handle table has already propagated
1814                      * a CNFException to passHandle at this point; this mark
1815                      * call is included to address cases where the readExternal
1816                      * method has cons'ed and thrown a new CNFException of its
1817                      * own.
1818                      */
1819                      handles.markException(passHandle, ex);
1820                 }
1821             }
1822             if (blocked) {
1823                 skipCustomData();
1824             }
1825         } finally {
1826             curContext = oldContext;
1827         }
1828         /*
1829          * At this point, if the externalizable data was not written in
1830          * block-data form and either the externalizable class doesn't exist
1831          * locally (i.e., obj == null) or readExternal() just threw a
1832          * CNFException, then the stream is probably in an inconsistent state,
1833          * since some (or all) of the externalizable data may not have been
1834          * consumed.  Since there's no "correct" action to take in this case,
1835          * we mimic the behavior of past serialization implementations and
1836          * blindly hope that the stream is in sync; if it isn't and additional
1837          * externalizable data remains in the stream, a subsequent read will
1838          * most likely throw a StreamCorruptedException.
1839          */
1840     }
1841 
1842     /**
1843      * Reads (or attempts to skip, if obj is null or is tagged with a
1844      * ClassNotFoundException) instance data for each serializable class of
1845      * object in stream, from superclass to subclass.  Expects that passHandle
1846      * is set to obj's handle before this method is called.
1847      */
1848     private void readSerialData(Object obj, ObjectStreamClass desc)
1849         throws IOException
1850     {
1851         ObjectStreamClass.ClassDataSlot[] slots = desc.getClassDataLayout();
1852         for (int i = 0; i < slots.length; i++) {
1853             ObjectStreamClass slotDesc = slots[i].desc;
1854 
1855             if (slots[i].hasData) {
1856                 if (obj != null &&
1857                     slotDesc.hasReadObjectMethod() &&
1858                     handles.lookupException(passHandle) == null)
1859                 {
1860                     SerialCallbackContext oldContext = curContext;
1861 
1862                     try {
1863                         curContext = new SerialCallbackContext(obj, slotDesc);
1864 
1865                         bin.setBlockDataMode(true);
1866                         slotDesc.invokeReadObject(obj, this);
1867                     } catch (ClassNotFoundException ex) {
1868                         /*
1869                          * In most cases, the handle table has already
1870                          * propagated a CNFException to passHandle at this
1871                          * point; this mark call is included to address cases
1872                          * where the custom readObject method has cons'ed and
1873                          * thrown a new CNFException of its own.
1874                          */
1875                         handles.markException(passHandle, ex);
1876                     } finally {
1877                         curContext.setUsed();
1878                         curContext = oldContext;
1879                     }
1880 
1881                     /*
1882                      * defaultDataEnd may have been set indirectly by custom
1883                      * readObject() method when calling defaultReadObject() or
1884                      * readFields(); clear it to restore normal read behavior.
1885                      */
1886                     defaultDataEnd = false;
1887                 } else {
1888                     defaultReadFields(obj, slotDesc);
1889                 }
1890                 if (slotDesc.hasWriteObjectData()) {
1891                     skipCustomData();
1892                 } else {
1893                     bin.setBlockDataMode(false);
1894                 }
1895             } else {
1896                 if (obj != null &&
1897                     slotDesc.hasReadObjectNoDataMethod() &&
1898                     handles.lookupException(passHandle) == null)
1899                 {
1900                     slotDesc.invokeReadObjectNoData(obj);
1901                 }
1902             }
1903         }
1904     }
1905 
1906     /**
1907      * Skips over all block data and objects until TC_ENDBLOCKDATA is
1908      * encountered.
1909      */
1910     private void skipCustomData() throws IOException {
1911         int oldHandle = passHandle;
1912         for (;;) {
1913             if (bin.getBlockDataMode()) {
1914                 bin.skipBlockData();
1915                 bin.setBlockDataMode(false);
1916             }
1917             switch (bin.peekByte()) {
1918                 case TC_BLOCKDATA:
1919                 case TC_BLOCKDATALONG:
1920                     bin.setBlockDataMode(true);
1921                     break;
1922 
1923                 case TC_ENDBLOCKDATA:
1924                     bin.readByte();
1925                     passHandle = oldHandle;
1926                     return;
1927 
1928                 default:
1929                     readObject0(false);
1930                     break;
1931             }
1932         }
1933     }
1934 
1935     /**
1936      * Reads in values of serializable fields declared by given class
1937      * descriptor.  If obj is non-null, sets field values in obj.  Expects that
1938      * passHandle is set to obj's handle before this method is called.
1939      */
1940     private void defaultReadFields(Object obj, ObjectStreamClass desc)
1941         throws IOException
1942     {
1943         // REMIND: is isInstance check necessary?
1944         Class cl = desc.forClass();
1945         if (cl != null && obj != null && !cl.isInstance(obj)) {
1946             throw new ClassCastException();
1947         }
1948 
1949         int primDataSize = desc.getPrimDataSize();
1950         if (primVals == null || primVals.length < primDataSize) {
1951             primVals = new byte[primDataSize];
1952         }
1953         bin.readFully(primVals, 0, primDataSize, false);
1954         if (obj != null) {
1955             desc.setPrimFieldValues(obj, primVals);
1956         }
1957 
1958         int objHandle = passHandle;
1959         ObjectStreamField[] fields = desc.getFields(false);
1960         Object[] objVals = new Object[desc.getNumObjFields()];
1961         int numPrimFields = fields.length - objVals.length;
1962         for (int i = 0; i < objVals.length; i++) {
1963             ObjectStreamField f = fields[numPrimFields + i];
1964             objVals[i] = readObject0(f.isUnshared());
1965             if (f.getField() != null) {
1966                 handles.markDependency(objHandle, passHandle);
1967             }
1968         }
1969         if (obj != null) {
1970             desc.setObjFieldValues(obj, objVals);
1971         }
1972         passHandle = objHandle;
1973     }
1974 
1975     /**
1976      * Reads in and returns IOException that caused serialization to abort.
1977      * All stream state is discarded prior to reading in fatal exception.  Sets
1978      * passHandle to fatal exception's handle.
1979      */
1980     private IOException readFatalException() throws IOException {
1981         if (bin.readByte() != TC_EXCEPTION) {
1982             throw new InternalError();
1983         }
1984         clear();
1985         return (IOException) readObject0(false);
1986     }
1987 
1988     /**
1989      * If recursion depth is 0, clears internal data structures; otherwise,
1990      * throws a StreamCorruptedException.  This method is called when a
1991      * TC_RESET typecode is encountered.
1992      */
1993     private void handleReset() throws StreamCorruptedException {
1994         if (depth > 0) {
1995             throw new StreamCorruptedException(
1996                 "unexpected reset; recursion depth: " + depth);
1997         }
1998         clear();
1999     }
2000 
2001     /**
2002      * Converts specified span of bytes into float values.
2003      */
2004     // REMIND: remove once hotspot inlines Float.intBitsToFloat
2005     private static native void bytesToFloats(byte[] src, int srcpos,
2006                                              float[] dst, int dstpos,
2007                                              int nfloats);
2008 
2009     /**
2010      * Converts specified span of bytes into double values.
2011      */
2012     // REMIND: remove once hotspot inlines Double.longBitsToDouble
2013     private static native void bytesToDoubles(byte[] src, int srcpos,
2014                                               double[] dst, int dstpos,
2015                                               int ndoubles);
2016 
2017     /**
2018      * Returns the first non-null class loader (not counting class loaders of
2019      * generated reflection implementation classes) up the execution stack, or
2020      * null if only code from the null class loader is on the stack.  This
2021      * method is also called via reflection by the following RMI-IIOP class:
2022      *
2023      *     com.sun.corba.se.internal.util.JDKClassLoader
2024      *
2025      * This method should not be removed or its signature changed without
2026      * corresponding modifications to the above class.
2027      */
2028     // REMIND: change name to something more accurate?
2029     private static native ClassLoader latestUserDefinedLoader();
2030 
2031     /**
2032      * Default GetField implementation.
2033      */
2034     private class GetFieldImpl extends GetField {
2035 
2036         /** class descriptor describing serializable fields */
2037         private final ObjectStreamClass desc;
2038         /** primitive field values */
2039         private final byte[] primVals;
2040         /** object field values */
2041         private final Object[] objVals;
2042         /** object field value handles */
2043         private final int[] objHandles;
2044 
2045         /**
2046          * Creates GetFieldImpl object for reading fields defined in given
2047          * class descriptor.
2048          */
2049         GetFieldImpl(ObjectStreamClass desc) {
2050             this.desc = desc;
2051             primVals = new byte[desc.getPrimDataSize()];
2052             objVals = new Object[desc.getNumObjFields()];
2053             objHandles = new int[objVals.length];
2054         }
2055 
2056         public ObjectStreamClass getObjectStreamClass() {
2057             return desc;
2058         }
2059 
2060         public boolean defaulted(String name) throws IOException {
2061             return (getFieldOffset(name, null) < 0);
2062         }
2063 
2064         public boolean get(String name, boolean val) throws IOException {
2065             int off = getFieldOffset(name, Boolean.TYPE);
2066             return (off >= 0) ? Bits.getBoolean(primVals, off) : val;
2067         }
2068 
2069         public byte get(String name, byte val) throws IOException {
2070             int off = getFieldOffset(name, Byte.TYPE);
2071             return (off >= 0) ? primVals[off] : val;
2072         }
2073 
2074         public char get(String name, char val) throws IOException {
2075             int off = getFieldOffset(name, Character.TYPE);
2076             return (off >= 0) ? Bits.getChar(primVals, off) : val;
2077         }
2078 
2079         public short get(String name, short val) throws IOException {
2080             int off = getFieldOffset(name, Short.TYPE);
2081             return (off >= 0) ? Bits.getShort(primVals, off) : val;
2082         }
2083 
2084         public int get(String name, int val) throws IOException {
2085             int off = getFieldOffset(name, Integer.TYPE);
2086             return (off >= 0) ? Bits.getInt(primVals, off) : val;
2087         }
2088 
2089         public float get(String name, float val) throws IOException {
2090             int off = getFieldOffset(name, Float.TYPE);
2091             return (off >= 0) ? Bits.getFloat(primVals, off) : val;
2092         }
2093 
2094         public long get(String name, long val) throws IOException {
2095             int off = getFieldOffset(name, Long.TYPE);
2096             return (off >= 0) ? Bits.getLong(primVals, off) : val;
2097         }
2098 
2099         public double get(String name, double val) throws IOException {
2100             int off = getFieldOffset(name, Double.TYPE);
2101             return (off >= 0) ? Bits.getDouble(primVals, off) : val;
2102         }
2103 
2104         public Object get(String name, Object val) throws IOException {
2105             int off = getFieldOffset(name, Object.class);
2106             if (off >= 0) {
2107                 int objHandle = objHandles[off];
2108                 handles.markDependency(passHandle, objHandle);
2109                 return (handles.lookupException(objHandle) == null) ?
2110                     objVals[off] : null;
2111             } else {
2112                 return val;
2113             }
2114         }
2115 
2116         /**
2117          * Reads primitive and object field values from stream.
2118          */
2119         void readFields() throws IOException {
2120             bin.readFully(primVals, 0, primVals.length, false);
2121 
2122             int oldHandle = passHandle;
2123             ObjectStreamField[] fields = desc.getFields(false);
2124             int numPrimFields = fields.length - objVals.length;
2125             for (int i = 0; i < objVals.length; i++) {
2126                 objVals[i] =
2127                     readObject0(fields[numPrimFields + i].isUnshared());
2128                 objHandles[i] = passHandle;
2129             }
2130             passHandle = oldHandle;
2131         }
2132 
2133         /**
2134          * Returns offset of field with given name and type.  A specified type
2135          * of null matches all types, Object.class matches all non-primitive
2136          * types, and any other non-null type matches assignable types only.
2137          * If no matching field is found in the (incoming) class
2138          * descriptor but a matching field is present in the associated local
2139          * class descriptor, returns -1.  Throws IllegalArgumentException if
2140          * neither incoming nor local class descriptor contains a match.
2141          */
2142         private int getFieldOffset(String name, Class type) {
2143             ObjectStreamField field = desc.getField(name, type);
2144             if (field != null) {
2145                 return field.getOffset();
2146             } else if (desc.getLocalDesc().getField(name, type) != null) {
2147                 return -1;
2148             } else {
2149                 throw new IllegalArgumentException("no such field " + name +
2150                                                    " with type " + type);
2151             }
2152         }
2153     }
2154 
2155     /**
2156      * Prioritized list of callbacks to be performed once object graph has been
2157      * completely deserialized.
2158      */
2159     private static class ValidationList {
2160 
2161         private static class Callback {
2162             final ObjectInputValidation obj;
2163             final int priority;
2164             Callback next;
2165             final AccessControlContext acc;
2166 
2167             Callback(ObjectInputValidation obj, int priority, Callback next,
2168                 AccessControlContext acc)
2169             {
2170                 this.obj = obj;
2171                 this.priority = priority;
2172                 this.next = next;
2173                 this.acc = acc;
2174             }
2175         }
2176 
2177         /** linked list of callbacks */
2178         private Callback list;
2179 
2180         /**
2181          * Creates new (empty) ValidationList.
2182          */
2183         ValidationList() {
2184         }
2185 
2186         /**
2187          * Registers callback.  Throws InvalidObjectException if callback
2188          * object is null.
2189          */
2190         void register(ObjectInputValidation obj, int priority)
2191             throws InvalidObjectException
2192         {
2193             if (obj == null) {
2194                 throw new InvalidObjectException("null callback");
2195             }
2196 
2197             Callback prev = null, cur = list;
2198             while (cur != null && priority < cur.priority) {
2199                 prev = cur;
2200                 cur = cur.next;
2201             }
2202             AccessControlContext acc = AccessController.getContext();
2203             if (prev != null) {
2204                 prev.next = new Callback(obj, priority, cur, acc);
2205             } else {
2206                 list = new Callback(obj, priority, list, acc);
2207             }
2208         }
2209 
2210         /**
2211          * Invokes all registered callbacks and clears the callback list.
2212          * Callbacks with higher priorities are called first; those with equal
2213          * priorities may be called in any order.  If any of the callbacks
2214          * throws an InvalidObjectException, the callback process is terminated
2215          * and the exception propagated upwards.
2216          */
2217         void doCallbacks() throws InvalidObjectException {
2218             try {
2219                 while (list != null) {
2220                     AccessController.doPrivileged(
2221                         new PrivilegedExceptionAction<Void>()
2222                     {
2223                         public Void run() throws InvalidObjectException {
2224                             list.obj.validateObject();
2225                             return null;
2226                         }
2227                     }, list.acc);
2228                     list = list.next;
2229                 }
2230             } catch (PrivilegedActionException ex) {
2231                 list = null;
2232                 throw (InvalidObjectException) ex.getException();
2233             }
2234         }
2235 
2236         /**
2237          * Resets the callback list to its initial (empty) state.
2238          */
2239         public void clear() {
2240             list = null;
2241         }
2242     }
2243 
2244     /**
2245      * Input stream supporting single-byte peek operations.
2246      */
2247     private static class PeekInputStream extends InputStream {
2248 
2249         /** underlying stream */
2250         private final InputStream in;
2251         /** peeked byte */
2252         private int peekb = -1;
2253 
2254         /**
2255          * Creates new PeekInputStream on top of given underlying stream.
2256          */
2257         PeekInputStream(InputStream in) {
2258             this.in = in;
2259         }
2260 
2261         /**
2262          * Peeks at next byte value in stream.  Similar to read(), except
2263          * that it does not consume the read value.
2264          */
2265         int peek() throws IOException {
2266             return (peekb >= 0) ? peekb : (peekb = in.read());
2267         }
2268 
2269         public int read() throws IOException {
2270             if (peekb >= 0) {
2271                 int v = peekb;
2272                 peekb = -1;
2273                 return v;
2274             } else {
2275                 return in.read();
2276             }
2277         }
2278 
2279         public int read(byte[] b, int off, int len) throws IOException {
2280             if (len == 0) {
2281                 return 0;
2282             } else if (peekb < 0) {
2283                 return in.read(b, off, len);
2284             } else {
2285                 b[off++] = (byte) peekb;
2286                 len--;
2287                 peekb = -1;
2288                 int n = in.read(b, off, len);
2289                 return (n >= 0) ? (n + 1) : 1;
2290             }
2291         }
2292 
2293         void readFully(byte[] b, int off, int len) throws IOException {
2294             int n = 0;
2295             while (n < len) {
2296                 int count = read(b, off + n, len - n);
2297                 if (count < 0) {
2298                     throw new EOFException();
2299                 }
2300                 n += count;
2301             }
2302         }
2303 
2304         public long skip(long n) throws IOException {
2305             if (n <= 0) {
2306                 return 0;
2307             }
2308             int skipped = 0;
2309             if (peekb >= 0) {
2310                 peekb = -1;
2311                 skipped++;
2312                 n--;
2313             }
2314             return skipped + skip(n);
2315         }
2316 
2317         public int available() throws IOException {
2318             return in.available() + ((peekb >= 0) ? 1 : 0);
2319         }
2320 
2321         public void close() throws IOException {
2322             in.close();
2323         }
2324     }
2325 
2326     /**
2327      * Input stream with two modes: in default mode, inputs data written in the
2328      * same format as DataOutputStream; in "block data" mode, inputs data
2329      * bracketed by block data markers (see object serialization specification
2330      * for details).  Buffering depends on block data mode: when in default
2331      * mode, no data is buffered in advance; when in block data mode, all data
2332      * for the current data block is read in at once (and buffered).
2333      */
2334     private class BlockDataInputStream
2335         extends InputStream implements DataInput
2336     {
2337         /** maximum data block length */
2338         private static final int MAX_BLOCK_SIZE = 1024;
2339         /** maximum data block header length */
2340         private static final int MAX_HEADER_SIZE = 5;
2341         /** (tunable) length of char buffer (for reading strings) */
2342         private static final int CHAR_BUF_SIZE = 256;
2343         /** readBlockHeader() return value indicating header read may block */
2344         private static final int HEADER_BLOCKED = -2;
2345 
2346         /** buffer for reading general/block data */
2347         private final byte[] buf = new byte[MAX_BLOCK_SIZE];
2348         /** buffer for reading block data headers */
2349         private final byte[] hbuf = new byte[MAX_HEADER_SIZE];
2350         /** char buffer for fast string reads */
2351         private final char[] cbuf = new char[CHAR_BUF_SIZE];
2352 
2353         /** block data mode */
2354         private boolean blkmode = false;
2355 
2356         // block data state fields; values meaningful only when blkmode true
2357         /** current offset into buf */
2358         private int pos = 0;
2359         /** end offset of valid data in buf, or -1 if no more block data */
2360         private int end = -1;
2361         /** number of bytes in current block yet to be read from stream */
2362         private int unread = 0;
2363 
2364         /** underlying stream (wrapped in peekable filter stream) */
2365         private final PeekInputStream in;
2366         /** loopback stream (for data reads that span data blocks) */
2367         private final DataInputStream din;
2368 
2369         /**
2370          * Creates new BlockDataInputStream on top of given underlying stream.
2371          * Block data mode is turned off by default.
2372          */
2373         BlockDataInputStream(InputStream in) {
2374             this.in = new PeekInputStream(in);
2375             din = new DataInputStream(this);
2376         }
2377 
2378         /**
2379          * Sets block data mode to the given mode (true == on, false == off)
2380          * and returns the previous mode value.  If the new mode is the same as
2381          * the old mode, no action is taken.  Throws IllegalStateException if
2382          * block data mode is being switched from on to off while unconsumed
2383          * block data is still present in the stream.
2384          */
2385         boolean setBlockDataMode(boolean newmode) throws IOException {
2386             if (blkmode == newmode) {
2387                 return blkmode;
2388             }
2389             if (newmode) {
2390                 pos = 0;
2391                 end = 0;
2392                 unread = 0;
2393             } else if (pos < end) {
2394                 throw new IllegalStateException("unread block data");
2395             }
2396             blkmode = newmode;
2397             return !blkmode;
2398         }
2399 
2400         /**
2401          * Returns true if the stream is currently in block data mode, false
2402          * otherwise.
2403          */
2404         boolean getBlockDataMode() {
2405             return blkmode;
2406         }
2407 
2408         /**
2409          * If in block data mode, skips to the end of the current group of data
2410          * blocks (but does not unset block data mode).  If not in block data
2411          * mode, throws an IllegalStateException.
2412          */
2413         void skipBlockData() throws IOException {
2414             if (!blkmode) {
2415                 throw new IllegalStateException("not in block data mode");
2416             }
2417             while (end >= 0) {
2418                 refill();
2419             }
2420         }
2421 
2422         /**
2423          * Attempts to read in the next block data header (if any).  If
2424          * canBlock is false and a full header cannot be read without possibly
2425          * blocking, returns HEADER_BLOCKED, else if the next element in the
2426          * stream is a block data header, returns the block data length
2427          * specified by the header, else returns -1.
2428          */
2429         private int readBlockHeader(boolean canBlock) throws IOException {
2430             if (defaultDataEnd) {
2431                 /*
2432                  * Fix for 4360508: stream is currently at the end of a field
2433                  * value block written via default serialization; since there
2434                  * is no terminating TC_ENDBLOCKDATA tag, simulate
2435                  * end-of-custom-data behavior explicitly.
2436                  */
2437                 return -1;
2438             }
2439             try {
2440                 for (;;) {
2441                     int avail = canBlock ? Integer.MAX_VALUE : in.available();
2442                     if (avail == 0) {
2443                         return HEADER_BLOCKED;
2444                     }
2445 
2446                     int tc = in.peek();
2447                     switch (tc) {
2448                         case TC_BLOCKDATA:
2449                             if (avail < 2) {
2450                                 return HEADER_BLOCKED;
2451                             }
2452                             in.readFully(hbuf, 0, 2);
2453                             return hbuf[1] & 0xFF;
2454 
2455                         case TC_BLOCKDATALONG:
2456                             if (avail < 5) {
2457                                 return HEADER_BLOCKED;
2458                             }
2459                             in.readFully(hbuf, 0, 5);
2460                             int len = Bits.getInt(hbuf, 1);
2461                             if (len < 0) {
2462                                 throw new StreamCorruptedException(
2463                                     "illegal block data header length: " +
2464                                     len);
2465                             }
2466                             return len;
2467 
2468                         /*
2469                          * TC_RESETs may occur in between data blocks.
2470                          * Unfortunately, this case must be parsed at a lower
2471                          * level than other typecodes, since primitive data
2472                          * reads may span data blocks separated by a TC_RESET.
2473                          */
2474                         case TC_RESET:
2475                             in.read();
2476                             handleReset();
2477                             break;
2478 
2479                         default:
2480                             if (tc >= 0 && (tc < TC_BASE || tc > TC_MAX)) {
2481                                 throw new StreamCorruptedException(
2482                                     String.format("invalid type code: %02X",
2483                                     tc));
2484                             }
2485                             return -1;
2486                     }
2487                 }
2488             } catch (EOFException ex) {
2489                 throw new StreamCorruptedException(
2490                     "unexpected EOF while reading block data header");
2491             }
2492         }
2493 
2494         /**
2495          * Refills internal buffer buf with block data.  Any data in buf at the
2496          * time of the call is considered consumed.  Sets the pos, end, and
2497          * unread fields to reflect the new amount of available block data; if
2498          * the next element in the stream is not a data block, sets pos and
2499          * unread to 0 and end to -1.
2500          */
2501         private void refill() throws IOException {
2502             try {
2503                 do {
2504                     pos = 0;
2505                     if (unread > 0) {
2506                         int n =
2507                             in.read(buf, 0, Math.min(unread, MAX_BLOCK_SIZE));
2508                         if (n >= 0) {
2509                             end = n;
2510                             unread -= n;
2511                         } else {
2512                             throw new StreamCorruptedException(
2513                                 "unexpected EOF in middle of data block");
2514                         }
2515                     } else {
2516                         int n = readBlockHeader(true);
2517                         if (n >= 0) {
2518                             end = 0;
2519                             unread = n;
2520                         } else {
2521                             end = -1;
2522                             unread = 0;
2523                         }
2524                     }
2525                 } while (pos == end);
2526             } catch (IOException ex) {
2527                 pos = 0;
2528                 end = -1;
2529                 unread = 0;
2530                 throw ex;
2531             }
2532         }
2533 
2534         /**
2535          * If in block data mode, returns the number of unconsumed bytes
2536          * remaining in the current data block.  If not in block data mode,
2537          * throws an IllegalStateException.
2538          */
2539         int currentBlockRemaining() {
2540             if (blkmode) {
2541                 return (end >= 0) ? (end - pos) + unread : 0;
2542             } else {
2543                 throw new IllegalStateException();
2544             }
2545         }
2546 
2547         /**
2548          * Peeks at (but does not consume) and returns the next byte value in
2549          * the stream, or -1 if the end of the stream/block data (if in block
2550          * data mode) has been reached.
2551          */
2552         int peek() throws IOException {
2553             if (blkmode) {
2554                 if (pos == end) {
2555                     refill();
2556                 }
2557                 return (end >= 0) ? (buf[pos] & 0xFF) : -1;
2558             } else {
2559                 return in.peek();
2560             }
2561         }
2562 
2563         /**
2564          * Peeks at (but does not consume) and returns the next byte value in
2565          * the stream, or throws EOFException if end of stream/block data has
2566          * been reached.
2567          */
2568         byte peekByte() throws IOException {
2569             int val = peek();
2570             if (val < 0) {
2571                 throw new EOFException();
2572             }
2573             return (byte) val;
2574         }
2575 
2576 
2577         /* ----------------- generic input stream methods ------------------ */
2578         /*
2579          * The following methods are equivalent to their counterparts in
2580          * InputStream, except that they interpret data block boundaries and
2581          * read the requested data from within data blocks when in block data
2582          * mode.
2583          */
2584 
2585         public int read() throws IOException {
2586             if (blkmode) {
2587                 if (pos == end) {
2588                     refill();
2589                 }
2590                 return (end >= 0) ? (buf[pos++] & 0xFF) : -1;
2591             } else {
2592                 return in.read();
2593             }
2594         }
2595 
2596         public int read(byte[] b, int off, int len) throws IOException {
2597             return read(b, off, len, false);
2598         }
2599 
2600         public long skip(long len) throws IOException {
2601             long remain = len;
2602             while (remain > 0) {
2603                 if (blkmode) {
2604                     if (pos == end) {
2605                         refill();
2606                     }
2607                     if (end < 0) {
2608                         break;
2609                     }
2610                     int nread = (int) Math.min(remain, end - pos);
2611                     remain -= nread;
2612                     pos += nread;
2613                 } else {
2614                     int nread = (int) Math.min(remain, MAX_BLOCK_SIZE);
2615                     if ((nread = in.read(buf, 0, nread)) < 0) {
2616                         break;
2617                     }
2618                     remain -= nread;
2619                 }
2620             }
2621             return len - remain;
2622         }
2623 
2624         public int available() throws IOException {
2625             if (blkmode) {
2626                 if ((pos == end) && (unread == 0)) {
2627                     int n;
2628                     while ((n = readBlockHeader(false)) == 0) ;
2629                     switch (n) {
2630                         case HEADER_BLOCKED:
2631                             break;
2632 
2633                         case -1:
2634                             pos = 0;
2635                             end = -1;
2636                             break;
2637 
2638                         default:
2639                             pos = 0;
2640                             end = 0;
2641                             unread = n;
2642                             break;
2643                     }
2644                 }
2645                 // avoid unnecessary call to in.available() if possible
2646                 int unreadAvail = (unread > 0) ?
2647                     Math.min(in.available(), unread) : 0;
2648                 return (end >= 0) ? (end - pos) + unreadAvail : 0;
2649             } else {
2650                 return in.available();
2651             }
2652         }
2653 
2654         public void close() throws IOException {
2655             if (blkmode) {
2656                 pos = 0;
2657                 end = -1;
2658                 unread = 0;
2659             }
2660             in.close();
2661         }
2662 
2663         /**
2664          * Attempts to read len bytes into byte array b at offset off.  Returns
2665          * the number of bytes read, or -1 if the end of stream/block data has
2666          * been reached.  If copy is true, reads values into an intermediate
2667          * buffer before copying them to b (to avoid exposing a reference to
2668          * b).
2669          */
2670         int read(byte[] b, int off, int len, boolean copy) throws IOException {
2671             if (len == 0) {
2672                 return 0;
2673             } else if (blkmode) {
2674                 if (pos == end) {
2675                     refill();
2676                 }
2677                 if (end < 0) {
2678                     return -1;
2679                 }
2680                 int nread = Math.min(len, end - pos);
2681                 System.arraycopy(buf, pos, b, off, nread);
2682                 pos += nread;
2683                 return nread;
2684             } else if (copy) {
2685                 int nread = in.read(buf, 0, Math.min(len, MAX_BLOCK_SIZE));
2686                 if (nread > 0) {
2687                     System.arraycopy(buf, 0, b, off, nread);
2688                 }
2689                 return nread;
2690             } else {
2691                 return in.read(b, off, len);
2692             }
2693         }
2694 
2695         /* ----------------- primitive data input methods ------------------ */
2696         /*
2697          * The following methods are equivalent to their counterparts in
2698          * DataInputStream, except that they interpret data block boundaries
2699          * and read the requested data from within data blocks when in block
2700          * data mode.
2701          */
2702 
2703         public void readFully(byte[] b) throws IOException {
2704             readFully(b, 0, b.length, false);
2705         }
2706 
2707         public void readFully(byte[] b, int off, int len) throws IOException {
2708             readFully(b, off, len, false);
2709         }
2710 
2711         public void readFully(byte[] b, int off, int len, boolean copy)
2712             throws IOException
2713         {
2714             while (len > 0) {
2715                 int n = read(b, off, len, copy);
2716                 if (n < 0) {
2717                     throw new EOFException();
2718                 }
2719                 off += n;
2720                 len -= n;
2721             }
2722         }
2723 
2724         public int skipBytes(int n) throws IOException {
2725             return din.skipBytes(n);
2726         }
2727 
2728         public boolean readBoolean() throws IOException {
2729             int v = read();
2730             if (v < 0) {
2731                 throw new EOFException();
2732             }
2733             return (v != 0);
2734         }
2735 
2736         public byte readByte() throws IOException {
2737             int v = read();
2738             if (v < 0) {
2739                 throw new EOFException();
2740             }
2741             return (byte) v;
2742         }
2743 
2744         public int readUnsignedByte() throws IOException {
2745             int v = read();
2746             if (v < 0) {
2747                 throw new EOFException();
2748             }
2749             return v;
2750         }
2751 
2752         public char readChar() throws IOException {
2753             if (!blkmode) {
2754                 pos = 0;
2755                 in.readFully(buf, 0, 2);
2756             } else if (end - pos < 2) {
2757                 return din.readChar();
2758             }
2759             char v = Bits.getChar(buf, pos);
2760             pos += 2;
2761             return v;
2762         }
2763 
2764         public short readShort() throws IOException {
2765             if (!blkmode) {
2766                 pos = 0;
2767                 in.readFully(buf, 0, 2);
2768             } else if (end - pos < 2) {
2769                 return din.readShort();
2770             }
2771             short v = Bits.getShort(buf, pos);
2772             pos += 2;
2773             return v;
2774         }
2775 
2776         public int readUnsignedShort() throws IOException {
2777             if (!blkmode) {
2778                 pos = 0;
2779                 in.readFully(buf, 0, 2);
2780             } else if (end - pos < 2) {
2781                 return din.readUnsignedShort();
2782             }
2783             int v = Bits.getShort(buf, pos) & 0xFFFF;
2784             pos += 2;
2785             return v;
2786         }
2787 
2788         public int readInt() throws IOException {
2789             if (!blkmode) {
2790                 pos = 0;
2791                 in.readFully(buf, 0, 4);
2792             } else if (end - pos < 4) {
2793                 return din.readInt();
2794             }
2795             int v = Bits.getInt(buf, pos);
2796             pos += 4;
2797             return v;
2798         }
2799 
2800         public float readFloat() throws IOException {
2801             if (!blkmode) {
2802                 pos = 0;
2803                 in.readFully(buf, 0, 4);
2804             } else if (end - pos < 4) {
2805                 return din.readFloat();
2806             }
2807             float v = Bits.getFloat(buf, pos);
2808             pos += 4;
2809             return v;
2810         }
2811 
2812         public long readLong() throws IOException {
2813             if (!blkmode) {
2814                 pos = 0;
2815                 in.readFully(buf, 0, 8);
2816             } else if (end - pos < 8) {
2817                 return din.readLong();
2818             }
2819             long v = Bits.getLong(buf, pos);
2820             pos += 8;
2821             return v;
2822         }
2823 
2824         public double readDouble() throws IOException {
2825             if (!blkmode) {
2826                 pos = 0;
2827                 in.readFully(buf, 0, 8);
2828             } else if (end - pos < 8) {
2829                 return din.readDouble();
2830             }
2831             double v = Bits.getDouble(buf, pos);
2832             pos += 8;
2833             return v;
2834         }
2835 
2836         public String readUTF() throws IOException {
2837             return readUTFBody(readUnsignedShort());
2838         }
2839 
2840         public String readLine() throws IOException {
2841             return din.readLine();      // deprecated, not worth optimizing
2842         }
2843 
2844         /* -------------- primitive data array input methods --------------- */
2845         /*
2846          * The following methods read in spans of primitive data values.
2847          * Though equivalent to calling the corresponding primitive read
2848          * methods repeatedly, these methods are optimized for reading groups
2849          * of primitive data values more efficiently.
2850          */
2851 
2852         void readBooleans(boolean[] v, int off, int len) throws IOException {
2853             int stop, endoff = off + len;
2854             while (off < endoff) {
2855                 if (!blkmode) {
2856                     int span = Math.min(endoff - off, MAX_BLOCK_SIZE);
2857                     in.readFully(buf, 0, span);
2858                     stop = off + span;
2859                     pos = 0;
2860                 } else if (end - pos < 1) {
2861                     v[off++] = din.readBoolean();
2862                     continue;
2863                 } else {
2864                     stop = Math.min(endoff, off + end - pos);
2865                 }
2866 
2867                 while (off < stop) {
2868                     v[off++] = Bits.getBoolean(buf, pos++);
2869                 }
2870             }
2871         }
2872 
2873         void readChars(char[] v, int off, int len) throws IOException {
2874             int stop, endoff = off + len;
2875             while (off < endoff) {
2876                 if (!blkmode) {
2877                     int span = Math.min(endoff - off, MAX_BLOCK_SIZE >> 1);
2878                     in.readFully(buf, 0, span << 1);
2879                     stop = off + span;
2880                     pos = 0;
2881                 } else if (end - pos < 2) {
2882                     v[off++] = din.readChar();
2883                     continue;
2884                 } else {
2885                     stop = Math.min(endoff, off + ((end - pos) >> 1));
2886                 }
2887 
2888                 while (off < stop) {
2889                     v[off++] = Bits.getChar(buf, pos);
2890                     pos += 2;
2891                 }
2892             }
2893         }
2894 
2895         void readShorts(short[] v, int off, int len) throws IOException {
2896             int stop, endoff = off + len;
2897             while (off < endoff) {
2898                 if (!blkmode) {
2899                     int span = Math.min(endoff - off, MAX_BLOCK_SIZE >> 1);
2900                     in.readFully(buf, 0, span << 1);
2901                     stop = off + span;
2902                     pos = 0;
2903                 } else if (end - pos < 2) {
2904                     v[off++] = din.readShort();
2905                     continue;
2906                 } else {
2907                     stop = Math.min(endoff, off + ((end - pos) >> 1));
2908                 }
2909 
2910                 while (off < stop) {
2911                     v[off++] = Bits.getShort(buf, pos);
2912                     pos += 2;
2913                 }
2914             }
2915         }
2916 
2917         void readInts(int[] v, int off, int len) throws IOException {
2918             int stop, endoff = off + len;
2919             while (off < endoff) {
2920                 if (!blkmode) {
2921                     int span = Math.min(endoff - off, MAX_BLOCK_SIZE >> 2);
2922                     in.readFully(buf, 0, span << 2);
2923                     stop = off + span;
2924                     pos = 0;
2925                 } else if (end - pos < 4) {
2926                     v[off++] = din.readInt();
2927                     continue;
2928                 } else {
2929                     stop = Math.min(endoff, off + ((end - pos) >> 2));
2930                 }
2931 
2932                 while (off < stop) {
2933                     v[off++] = Bits.getInt(buf, pos);
2934                     pos += 4;
2935                 }
2936             }
2937         }
2938 
2939         void readFloats(float[] v, int off, int len) throws IOException {
2940             int span, endoff = off + len;
2941             while (off < endoff) {
2942                 if (!blkmode) {
2943                     span = Math.min(endoff - off, MAX_BLOCK_SIZE >> 2);
2944                     in.readFully(buf, 0, span << 2);
2945                     pos = 0;
2946                 } else if (end - pos < 4) {
2947                     v[off++] = din.readFloat();
2948                     continue;
2949                 } else {
2950                     span = Math.min(endoff - off, ((end - pos) >> 2));
2951                 }
2952 
2953                 bytesToFloats(buf, pos, v, off, span);
2954                 off += span;
2955                 pos += span << 2;
2956             }
2957         }
2958 
2959         void readLongs(long[] v, int off, int len) throws IOException {
2960             int stop, endoff = off + len;
2961             while (off < endoff) {
2962                 if (!blkmode) {
2963                     int span = Math.min(endoff - off, MAX_BLOCK_SIZE >> 3);
2964                     in.readFully(buf, 0, span << 3);
2965                     stop = off + span;
2966                     pos = 0;
2967                 } else if (end - pos < 8) {
2968                     v[off++] = din.readLong();
2969                     continue;
2970                 } else {
2971                     stop = Math.min(endoff, off + ((end - pos) >> 3));
2972                 }
2973 
2974                 while (off < stop) {
2975                     v[off++] = Bits.getLong(buf, pos);
2976                     pos += 8;
2977                 }
2978             }
2979         }
2980 
2981         void readDoubles(double[] v, int off, int len) throws IOException {
2982             int span, endoff = off + len;
2983             while (off < endoff) {
2984                 if (!blkmode) {
2985                     span = Math.min(endoff - off, MAX_BLOCK_SIZE >> 3);
2986                     in.readFully(buf, 0, span << 3);
2987                     pos = 0;
2988                 } else if (end - pos < 8) {
2989                     v[off++] = din.readDouble();
2990                     continue;
2991                 } else {
2992                     span = Math.min(endoff - off, ((end - pos) >> 3));
2993                 }
2994 
2995                 bytesToDoubles(buf, pos, v, off, span);
2996                 off += span;
2997                 pos += span << 3;
2998             }
2999         }
3000 
3001         /**
3002          * Reads in string written in "long" UTF format.  "Long" UTF format is
3003          * identical to standard UTF, except that it uses an 8 byte header
3004          * (instead of the standard 2 bytes) to convey the UTF encoding length.
3005          */
3006         String readLongUTF() throws IOException {
3007             return readUTFBody(readLong());
3008         }
3009 
3010         /**
3011          * Reads in the "body" (i.e., the UTF representation minus the 2-byte
3012          * or 8-byte length header) of a UTF encoding, which occupies the next
3013          * utflen bytes.
3014          */
3015         private String readUTFBody(long utflen) throws IOException {
3016             StringBuilder sbuf = new StringBuilder();
3017             if (!blkmode) {
3018                 end = pos = 0;
3019             }
3020 
3021             while (utflen > 0) {
3022                 int avail = end - pos;
3023                 if (avail >= 3 || (long) avail == utflen) {
3024                     utflen -= readUTFSpan(sbuf, utflen);
3025                 } else {
3026                     if (blkmode) {
3027                         // near block boundary, read one byte at a time
3028                         utflen -= readUTFChar(sbuf, utflen);
3029                     } else {
3030                         // shift and refill buffer manually
3031                         if (avail > 0) {
3032                             System.arraycopy(buf, pos, buf, 0, avail);
3033                         }
3034                         pos = 0;
3035                         end = (int) Math.min(MAX_BLOCK_SIZE, utflen);
3036                         in.readFully(buf, avail, end - avail);
3037                     }
3038                 }
3039             }
3040 
3041             return sbuf.toString();
3042         }
3043 
3044         /**
3045          * Reads span of UTF-encoded characters out of internal buffer
3046          * (starting at offset pos and ending at or before offset end),
3047          * consuming no more than utflen bytes.  Appends read characters to
3048          * sbuf.  Returns the number of bytes consumed.
3049          */
3050         private long readUTFSpan(StringBuilder sbuf, long utflen)
3051             throws IOException
3052         {
3053             int cpos = 0;
3054             int start = pos;
3055             int avail = Math.min(end - pos, CHAR_BUF_SIZE);
3056             // stop short of last char unless all of utf bytes in buffer
3057             int stop = pos + ((utflen > avail) ? avail - 2 : (int) utflen);
3058             boolean outOfBounds = false;
3059 
3060             try {
3061                 while (pos < stop) {
3062                     int b1, b2, b3;
3063                     b1 = buf[pos++] & 0xFF;
3064                     switch (b1 >> 4) {
3065                         case 0:
3066                         case 1:
3067                         case 2:
3068                         case 3:
3069                         case 4:
3070                         case 5:
3071                         case 6:
3072                         case 7:   // 1 byte format: 0xxxxxxx
3073                             cbuf[cpos++] = (char) b1;
3074                             break;
3075 
3076                         case 12:
3077                         case 13:  // 2 byte format: 110xxxxx 10xxxxxx
3078                             b2 = buf[pos++];
3079                             if ((b2 & 0xC0) != 0x80) {
3080                                 throw new UTFDataFormatException();
3081                             }
3082                             cbuf[cpos++] = (char) (((b1 & 0x1F) << 6) |
3083                                                    ((b2 & 0x3F) << 0));
3084                             break;
3085 
3086                         case 14:  // 3 byte format: 1110xxxx 10xxxxxx 10xxxxxx
3087                             b3 = buf[pos + 1];
3088                             b2 = buf[pos + 0];
3089                             pos += 2;
3090                             if ((b2 & 0xC0) != 0x80 || (b3 & 0xC0) != 0x80) {
3091                                 throw new UTFDataFormatException();
3092                             }
3093                             cbuf[cpos++] = (char) (((b1 & 0x0F) << 12) |
3094                                                    ((b2 & 0x3F) << 6) |
3095                                                    ((b3 & 0x3F) << 0));
3096                             break;
3097 
3098                         default:  // 10xx xxxx, 1111 xxxx
3099                             throw new UTFDataFormatException();
3100                     }
3101                 }
3102             } catch (ArrayIndexOutOfBoundsException ex) {
3103                 outOfBounds = true;
3104             } finally {
3105                 if (outOfBounds || (pos - start) > utflen) {
3106                     /*
3107                      * Fix for 4450867: if a malformed utf char causes the
3108                      * conversion loop to scan past the expected end of the utf
3109                      * string, only consume the expected number of utf bytes.
3110                      */
3111                     pos = start + (int) utflen;
3112                     throw new UTFDataFormatException();
3113                 }
3114             }
3115 
3116             sbuf.append(cbuf, 0, cpos);
3117             return pos - start;
3118         }
3119 
3120         /**
3121          * Reads in single UTF-encoded character one byte at a time, appends
3122          * the character to sbuf, and returns the number of bytes consumed.
3123          * This method is used when reading in UTF strings written in block
3124          * data mode to handle UTF-encoded characters which (potentially)
3125          * straddle block-data boundaries.
3126          */
3127         private int readUTFChar(StringBuilder sbuf, long utflen)
3128             throws IOException
3129         {
3130             int b1, b2, b3;
3131             b1 = readByte() & 0xFF;
3132             switch (b1 >> 4) {
3133                 case 0:
3134                 case 1:
3135                 case 2:
3136                 case 3:
3137                 case 4:
3138                 case 5:
3139                 case 6:
3140                 case 7:     // 1 byte format: 0xxxxxxx
3141                     sbuf.append((char) b1);
3142                     return 1;
3143 
3144                 case 12:
3145                 case 13:    // 2 byte format: 110xxxxx 10xxxxxx
3146                     if (utflen < 2) {
3147                         throw new UTFDataFormatException();
3148                     }
3149                     b2 = readByte();
3150                     if ((b2 & 0xC0) != 0x80) {
3151                         throw new UTFDataFormatException();
3152                     }
3153                     sbuf.append((char) (((b1 & 0x1F) << 6) |
3154                                         ((b2 & 0x3F) << 0)));
3155                     return 2;
3156 
3157                 case 14:    // 3 byte format: 1110xxxx 10xxxxxx 10xxxxxx
3158                     if (utflen < 3) {
3159                         if (utflen == 2) {
3160                             readByte();         // consume remaining byte
3161                         }
3162                         throw new UTFDataFormatException();
3163                     }
3164                     b2 = readByte();
3165                     b3 = readByte();
3166                     if ((b2 & 0xC0) != 0x80 || (b3 & 0xC0) != 0x80) {
3167                         throw new UTFDataFormatException();
3168                     }
3169                     sbuf.append((char) (((b1 & 0x0F) << 12) |
3170                                         ((b2 & 0x3F) << 6) |
3171                                         ((b3 & 0x3F) << 0)));
3172                     return 3;
3173 
3174                 default:   // 10xx xxxx, 1111 xxxx
3175                     throw new UTFDataFormatException();
3176             }
3177         }
3178     }
3179 
3180     /**
3181      * Unsynchronized table which tracks wire handle to object mappings, as
3182      * well as ClassNotFoundExceptions associated with deserialized objects.
3183      * This class implements an exception-propagation algorithm for
3184      * determining which objects should have ClassNotFoundExceptions associated
3185      * with them, taking into account cycles and discontinuities (e.g., skipped
3186      * fields) in the object graph.
3187      *
3188      * <p>General use of the table is as follows: during deserialization, a
3189      * given object is first assigned a handle by calling the assign method.
3190      * This method leaves the assigned handle in an "open" state, wherein
3191      * dependencies on the exception status of other handles can be registered
3192      * by calling the markDependency method, or an exception can be directly
3193      * associated with the handle by calling markException.  When a handle is
3194      * tagged with an exception, the HandleTable assumes responsibility for
3195      * propagating the exception to any other objects which depend
3196      * (transitively) on the exception-tagged object.
3197      *
3198      * <p>Once all exception information/dependencies for the handle have been
3199      * registered, the handle should be "closed" by calling the finish method
3200      * on it.  The act of finishing a handle allows the exception propagation
3201      * algorithm to aggressively prune dependency links, lessening the
3202      * performance/memory impact of exception tracking.
3203      *
3204      * <p>Note that the exception propagation algorithm used depends on handles
3205      * being assigned/finished in LIFO order; however, for simplicity as well
3206      * as memory conservation, it does not enforce this constraint.
3207      */
3208     // REMIND: add full description of exception propagation algorithm?
3209     private static class HandleTable {
3210 
3211         /* status codes indicating whether object has associated exception */
3212         private static final byte STATUS_OK = 1;
3213         private static final byte STATUS_UNKNOWN = 2;
3214         private static final byte STATUS_EXCEPTION = 3;
3215 
3216         /** array mapping handle -> object status */
3217         byte[] status;
3218         /** array mapping handle -> object/exception (depending on status) */
3219         Object[] entries;
3220         /** array mapping handle -> list of dependent handles (if any) */
3221         HandleList[] deps;
3222         /** lowest unresolved dependency */
3223         int lowDep = -1;
3224         /** number of handles in table */
3225         int size = 0;
3226 
3227         /**
3228          * Creates handle table with the given initial capacity.
3229          */
3230         HandleTable(int initialCapacity) {
3231             status = new byte[initialCapacity];
3232             entries = new Object[initialCapacity];
3233             deps = new HandleList[initialCapacity];
3234         }
3235 
3236         /**
3237          * Assigns next available handle to given object, and returns assigned
3238          * handle.  Once object has been completely deserialized (and all
3239          * dependencies on other objects identified), the handle should be
3240          * "closed" by passing it to finish().
3241          */
3242         int assign(Object obj) {
3243             if (size >= entries.length) {
3244                 grow();
3245             }
3246             status[size] = STATUS_UNKNOWN;
3247             entries[size] = obj;
3248             return size++;
3249         }
3250 
3251         /**
3252          * Registers a dependency (in exception status) of one handle on
3253          * another.  The dependent handle must be "open" (i.e., assigned, but
3254          * not finished yet).  No action is taken if either dependent or target
3255          * handle is NULL_HANDLE.
3256          */
3257         void markDependency(int dependent, int target) {
3258             if (dependent == NULL_HANDLE || target == NULL_HANDLE) {
3259                 return;
3260             }
3261             switch (status[dependent]) {
3262 
3263                 case STATUS_UNKNOWN:
3264                     switch (status[target]) {
3265                         case STATUS_OK:
3266                             // ignore dependencies on objs with no exception
3267                             break;
3268 
3269                         case STATUS_EXCEPTION:
3270                             // eagerly propagate exception
3271                             markException(dependent,
3272                                 (ClassNotFoundException) entries[target]);
3273                             break;
3274 
3275                         case STATUS_UNKNOWN:
3276                             // add to dependency list of target
3277                             if (deps[target] == null) {
3278                                 deps[target] = new HandleList();
3279                             }
3280                             deps[target].add(dependent);
3281 
3282                             // remember lowest unresolved target seen
3283                             if (lowDep < 0 || lowDep > target) {
3284                                 lowDep = target;
3285                             }
3286                             break;
3287 
3288                         default:
3289                             throw new InternalError();
3290                     }
3291                     break;
3292 
3293                 case STATUS_EXCEPTION:
3294                     break;
3295 
3296                 default:
3297                     throw new InternalError();
3298             }
3299         }
3300 
3301         /**
3302          * Associates a ClassNotFoundException (if one not already associated)
3303          * with the currently active handle and propagates it to other
3304          * referencing objects as appropriate.  The specified handle must be
3305          * "open" (i.e., assigned, but not finished yet).
3306          */
3307         void markException(int handle, ClassNotFoundException ex) {
3308             switch (status[handle]) {
3309                 case STATUS_UNKNOWN:
3310                     status[handle] = STATUS_EXCEPTION;
3311                     entries[handle] = ex;
3312 
3313                     // propagate exception to dependents
3314                     HandleList dlist = deps[handle];
3315                     if (dlist != null) {
3316                         int ndeps = dlist.size();
3317                         for (int i = 0; i < ndeps; i++) {
3318                             markException(dlist.get(i), ex);
3319                         }
3320                         deps[handle] = null;
3321                     }
3322                     break;
3323 
3324                 case STATUS_EXCEPTION:
3325                     break;
3326 
3327                 default:
3328                     throw new InternalError();
3329             }
3330         }
3331 
3332         /**
3333          * Marks given handle as finished, meaning that no new dependencies
3334          * will be marked for handle.  Calls to the assign and finish methods
3335          * must occur in LIFO order.
3336          */
3337         void finish(int handle) {
3338             int end;
3339             if (lowDep < 0) {
3340                 // no pending unknowns, only resolve current handle
3341                 end = handle + 1;
3342             } else if (lowDep >= handle) {
3343                 // pending unknowns now clearable, resolve all upward handles
3344                 end = size;
3345                 lowDep = -1;
3346             } else {
3347                 // unresolved backrefs present, can't resolve anything yet
3348                 return;
3349             }
3350 
3351             // change STATUS_UNKNOWN -> STATUS_OK in selected span of handles
3352             for (int i = handle; i < end; i++) {
3353                 switch (status[i]) {
3354                     case STATUS_UNKNOWN:
3355                         status[i] = STATUS_OK;
3356                         deps[i] = null;
3357                         break;
3358 
3359                     case STATUS_OK:
3360                     case STATUS_EXCEPTION:
3361                         break;
3362 
3363                     default:
3364                         throw new InternalError();
3365                 }
3366             }
3367         }
3368 
3369         /**
3370          * Assigns a new object to the given handle.  The object previously
3371          * associated with the handle is forgotten.  This method has no effect
3372          * if the given handle already has an exception associated with it.
3373          * This method may be called at any time after the handle is assigned.
3374          */
3375         void setObject(int handle, Object obj) {
3376             switch (status[handle]) {
3377                 case STATUS_UNKNOWN:
3378                 case STATUS_OK:
3379                     entries[handle] = obj;
3380                     break;
3381 
3382                 case STATUS_EXCEPTION:
3383                     break;
3384 
3385                 default:
3386                     throw new InternalError();
3387             }
3388         }
3389 
3390         /**
3391          * Looks up and returns object associated with the given handle.
3392          * Returns null if the given handle is NULL_HANDLE, or if it has an
3393          * associated ClassNotFoundException.
3394          */
3395         Object lookupObject(int handle) {
3396             return (handle != NULL_HANDLE &&
3397                     status[handle] != STATUS_EXCEPTION) ?
3398                 entries[handle] : null;
3399         }
3400 
3401         /**
3402          * Looks up and returns ClassNotFoundException associated with the
3403          * given handle.  Returns null if the given handle is NULL_HANDLE, or
3404          * if there is no ClassNotFoundException associated with the handle.
3405          */
3406         ClassNotFoundException lookupException(int handle) {
3407             return (handle != NULL_HANDLE &&
3408                     status[handle] == STATUS_EXCEPTION) ?
3409                 (ClassNotFoundException) entries[handle] : null;
3410         }
3411 
3412         /**
3413          * Resets table to its initial state.
3414          */
3415         void clear() {
3416             Arrays.fill(status, 0, size, (byte) 0);
3417             Arrays.fill(entries, 0, size, null);
3418             Arrays.fill(deps, 0, size, null);
3419             lowDep = -1;
3420             size = 0;
3421         }
3422 
3423         /**
3424          * Returns number of handles registered in table.
3425          */
3426         int size() {
3427             return size;
3428         }
3429 
3430         /**
3431          * Expands capacity of internal arrays.
3432          */
3433         private void grow() {
3434             int newCapacity = (entries.length << 1) + 1;
3435 
3436             byte[] newStatus = new byte[newCapacity];
3437             Object[] newEntries = new Object[newCapacity];
3438             HandleList[] newDeps = new HandleList[newCapacity];
3439 
3440             System.arraycopy(status, 0, newStatus, 0, size);
3441             System.arraycopy(entries, 0, newEntries, 0, size);
3442             System.arraycopy(deps, 0, newDeps, 0, size);
3443 
3444             status = newStatus;
3445             entries = newEntries;
3446             deps = newDeps;
3447         }
3448 
3449         /**
3450          * Simple growable list of (integer) handles.
3451          */
3452         private static class HandleList {
3453             private int[] list = new int[4];
3454             private int size = 0;
3455 
3456             public HandleList() {
3457             }
3458 
3459             public void add(int handle) {
3460                 if (size >= list.length) {
3461                     int[] newList = new int[list.length << 1];
3462                     System.arraycopy(list, 0, newList, 0, list.length);
3463                     list = newList;
3464                 }
3465                 list[size++] = handle;
3466             }
3467 
3468             public int get(int index) {
3469                 if (index >= size) {
3470                     throw new ArrayIndexOutOfBoundsException();
3471                 }
3472                 return list[index];
3473             }
3474 
3475             public int size() {
3476                 return size;
3477             }
3478         }
3479     }
3480 
3481     /**
3482      * Method for cloning arrays in case of using unsharing reading
3483      */
3484     private static Object cloneArray(Object array) {
3485         if (array instanceof Object[]) {
3486             return ((Object[]) array).clone();
3487         } else if (array instanceof boolean[]) {
3488             return ((boolean[]) array).clone();
3489         } else if (array instanceof byte[]) {
3490             return ((byte[]) array).clone();
3491         } else if (array instanceof char[]) {
3492             return ((char[]) array).clone();
3493         } else if (array instanceof double[]) {
3494             return ((double[]) array).clone();
3495         } else if (array instanceof float[]) {
3496             return ((float[]) array).clone();
3497         } else if (array instanceof int[]) {
3498             return ((int[]) array).clone();
3499         } else if (array instanceof long[]) {
3500             return ((long[]) array).clone();
3501         } else if (array instanceof short[]) {
3502             return ((short[]) array).clone();
3503         } else {
3504             throw new AssertionError();
3505         }
3506     }
3507 
3508 }