1 /*
   2  * Copyright (c) 1996, 2022, 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.lang.invoke.MethodHandle;
  29 import java.lang.invoke.MethodHandles;
  30 import java.lang.invoke.MethodType;
  31 import java.lang.reflect.Constructor;
  32 import java.lang.reflect.Field;
  33 import java.lang.reflect.InaccessibleObjectException;
  34 import java.lang.reflect.InvocationTargetException;
  35 import java.lang.reflect.RecordComponent;
  36 import java.lang.reflect.UndeclaredThrowableException;
  37 import java.lang.reflect.Member;
  38 import java.lang.reflect.Method;
  39 import java.lang.reflect.Modifier;
  40 import java.lang.reflect.Proxy;
  41 import java.security.AccessControlContext;
  42 import java.security.AccessController;
  43 import java.security.MessageDigest;
  44 import java.security.NoSuchAlgorithmException;
  45 import java.security.PermissionCollection;
  46 import java.security.Permissions;
  47 import java.security.PrivilegedAction;
  48 import java.security.PrivilegedActionException;
  49 import java.security.PrivilegedExceptionAction;
  50 import java.security.ProtectionDomain;
  51 import java.util.ArrayList;
  52 import java.util.Arrays;
  53 import java.util.Collections;
  54 import java.util.Comparator;
  55 import java.util.HashSet;
  56 import java.util.Map;
  57 import java.util.Set;
  58 import java.util.concurrent.ConcurrentHashMap;
  59 import jdk.internal.misc.Unsafe;
  60 import jdk.internal.reflect.CallerSensitive;
  61 import jdk.internal.reflect.Reflection;
  62 import jdk.internal.reflect.ReflectionFactory;
  63 import jdk.internal.access.SharedSecrets;
  64 import jdk.internal.access.JavaSecurityAccess;
  65 import sun.reflect.misc.ReflectUtil;
  66 
  67 /**
  68  * Serialization's descriptor for classes.  It contains the name and
  69  * serialVersionUID of the class.  The ObjectStreamClass for a specific class
  70  * loaded in this Java VM can be found/created using the lookup method.
  71  *
  72  * <p>The algorithm to compute the SerialVersionUID is described in
  73  * <a href="{@docRoot}/../specs/serialization/class.html#stream-unique-identifiers">
  74  *    <cite>Java Object Serialization Specification</cite>, Section 4.6, "Stream Unique Identifiers"</a>.
  75  *
  76  * @author      Mike Warres
  77  * @author      Roger Riggs
  78  * @see ObjectStreamField
  79  * @see <a href="{@docRoot}/../specs/serialization/class.html">
  80  *      <cite>Java Object Serialization Specification,</cite> Section 4, "Class Descriptors"</a>
  81  * @since   1.1
  82  */
  83 public final class ObjectStreamClass implements Serializable {
  84 
  85     /** serialPersistentFields value indicating no serializable fields */
  86     public static final ObjectStreamField[] NO_FIELDS =
  87         new ObjectStreamField[0];
  88 
  89     @java.io.Serial
  90     private static final long serialVersionUID = -6120832682080437368L;
  91     /**
  92      * {@code ObjectStreamClass} has no fields for default serialization.
  93      */
  94     @java.io.Serial
  95     private static final ObjectStreamField[] serialPersistentFields =
  96         NO_FIELDS;
  97 
  98     /** reflection factory for obtaining serialization constructors */
  99     @SuppressWarnings("removal")
 100     private static final ReflectionFactory reflFactory =
 101         AccessController.doPrivileged(
 102             new ReflectionFactory.GetReflectionFactoryAction());
 103 
 104     private static class Caches {
 105         /** cache mapping local classes -> descriptors */
 106         static final ClassCache<ObjectStreamClass> localDescs =
 107             new ClassCache<>() {
 108                 @Override
 109                 protected ObjectStreamClass computeValue(Class<?> type) {
 110                     return new ObjectStreamClass(type);
 111                 }
 112             };
 113 
 114         /** cache mapping field group/local desc pairs -> field reflectors */
 115         static final ClassCache<Map<FieldReflectorKey, FieldReflector>> reflectors =
 116             new ClassCache<>() {
 117                 @Override
 118                 protected Map<FieldReflectorKey, FieldReflector> computeValue(Class<?> type) {
 119                     return new ConcurrentHashMap<>();
 120                 }
 121             };
 122     }
 123 
 124     /** class associated with this descriptor (if any) */
 125     private Class<?> cl;
 126     /** name of class represented by this descriptor */
 127     private String name;
 128     /** serialVersionUID of represented class (null if not computed yet) */
 129     private volatile Long suid;
 130 
 131     /** true if represents dynamic proxy class */
 132     private boolean isProxy;
 133     /** true if represents enum type */
 134     private boolean isEnum;
 135     /** true if represents record type */
 136     private boolean isRecord;
 137     /** true if represents a value class */
 138     private boolean isValue;
 139     /** true if represented class implements Serializable */
 140     private boolean serializable;
 141     /** true if represented class implements Externalizable */
 142     private boolean externalizable;
 143     /** true if desc has data written by class-defined writeObject method */
 144     private boolean hasWriteObjectData;
 145     /**
 146      * true if desc has externalizable data written in block data format; this
 147      * must be true by default to accommodate ObjectInputStream subclasses which
 148      * override readClassDescriptor() to return class descriptors obtained from
 149      * ObjectStreamClass.lookup() (see 4461737)
 150      */
 151     private boolean hasBlockExternalData = true;
 152 
 153     /**
 154      * Contains information about InvalidClassException instances to be thrown
 155      * when attempting operations on an invalid class. Note that instances of
 156      * this class are immutable and are potentially shared among
 157      * ObjectStreamClass instances.
 158      */
 159     private static class ExceptionInfo {
 160         private final String className;
 161         private final String message;
 162 
 163         ExceptionInfo(String cn, String msg) {
 164             className = cn;
 165             message = msg;
 166         }
 167 
 168         /**
 169          * Returns (does not throw) an InvalidClassException instance created
 170          * from the information in this object, suitable for being thrown by
 171          * the caller.
 172          */
 173         InvalidClassException newInvalidClassException() {
 174             return new InvalidClassException(className, message);
 175         }
 176     }
 177 
 178     /** exception (if any) thrown while attempting to resolve class */
 179     private ClassNotFoundException resolveEx;
 180     /** exception (if any) to throw if non-enum deserialization attempted */
 181     private ExceptionInfo deserializeEx;
 182     /** exception (if any) to throw if non-enum serialization attempted */
 183     private ExceptionInfo serializeEx;
 184     /** exception (if any) to throw if default serialization attempted */
 185     private ExceptionInfo defaultSerializeEx;
 186 
 187     /** serializable fields */
 188     private ObjectStreamField[] fields;
 189     /** aggregate marshalled size of primitive fields */
 190     private int primDataSize;
 191     /** number of non-primitive fields */
 192     private int numObjFields;
 193     /** reflector for setting/getting serializable field values */
 194     private FieldReflector fieldRefl;
 195     /** data layout of serialized objects described by this class desc */
 196     private volatile ClassDataSlot[] dataLayout;
 197 
 198     /** serialization-appropriate constructor, or null if none */
 199     private Constructor<?> cons;
 200     /** record canonical constructor (shared among OSCs for same class), or null */
 201     private MethodHandle canonicalCtr;
 202     /** cache of record deserialization constructors per unique set of stream fields
 203      * (shared among OSCs for same class), or null */
 204     private DeserializationConstructorsCache deserializationCtrs;
 205     /** session-cache of record deserialization constructor
 206      * (in de-serialized OSC only), or null */
 207     private MethodHandle deserializationCtr;
 208     /** protection domains that need to be checked when calling the constructor */
 209     private ProtectionDomain[] domains;
 210 
 211     /** class-defined writeObject method, or null if none */
 212     private Method writeObjectMethod;
 213     /** class-defined readObject method, or null if none */
 214     private Method readObjectMethod;
 215     /** class-defined readObjectNoData method, or null if none */
 216     private Method readObjectNoDataMethod;
 217     /** class-defined writeReplace method, or null if none */
 218     private Method writeReplaceMethod;
 219     /** class-defined readResolve method, or null if none */
 220     private Method readResolveMethod;
 221 
 222     /** local class descriptor for represented class (may point to self) */
 223     private ObjectStreamClass localDesc;
 224     /** superclass descriptor appearing in stream */
 225     private ObjectStreamClass superDesc;
 226 
 227     /** true if, and only if, the object has been correctly initialized */
 228     private boolean initialized;
 229 
 230     /**
 231      * Initializes native code.
 232      */
 233     private static native void initNative();
 234     static {
 235         initNative();
 236     }
 237 
 238     /**
 239      * Find the descriptor for a class that can be serialized.  Creates an
 240      * ObjectStreamClass instance if one does not exist yet for class. Null is
 241      * returned if the specified class does not implement java.io.Serializable
 242      * or java.io.Externalizable.
 243      *
 244      * @param   cl class for which to get the descriptor
 245      * @return  the class descriptor for the specified class
 246      */
 247     public static ObjectStreamClass lookup(Class<?> cl) {
 248         return lookup(cl, false);
 249     }
 250 
 251     /**
 252      * Returns the descriptor for any class, regardless of whether it
 253      * implements {@link Serializable}.
 254      *
 255      * @param        cl class for which to get the descriptor
 256      * @return       the class descriptor for the specified class
 257      * @since 1.6
 258      */
 259     public static ObjectStreamClass lookupAny(Class<?> cl) {
 260         return lookup(cl, true);
 261     }
 262 
 263     /**
 264      * Returns the name of the class described by this descriptor.
 265      * This method returns the name of the class in the format that
 266      * is used by the {@link Class#getName} method.
 267      *
 268      * @return a string representing the name of the class
 269      */
 270     public String getName() {
 271         return name;
 272     }
 273 
 274     /**
 275      * Return the serialVersionUID for this class.  The serialVersionUID
 276      * defines a set of classes all with the same name that have evolved from a
 277      * common root class and agree to be serialized and deserialized using a
 278      * common format.  NonSerializable classes have a serialVersionUID of 0L.
 279      *
 280      * @return  the SUID of the class described by this descriptor
 281      */
 282     @SuppressWarnings("removal")
 283     public long getSerialVersionUID() {
 284         // REMIND: synchronize instead of relying on volatile?
 285         if (suid == null) {
 286             if (isRecord)
 287                 return 0L;
 288 
 289             suid = AccessController.doPrivileged(
 290                 new PrivilegedAction<Long>() {
 291                     public Long run() {
 292                         return computeDefaultSUID(cl);
 293                     }
 294                 }
 295             );
 296         }
 297         return suid.longValue();
 298     }
 299 
 300     /**
 301      * Return the class in the local VM that this version is mapped to.  Null
 302      * is returned if there is no corresponding local class.
 303      *
 304      * @return  the {@code Class} instance that this descriptor represents
 305      */
 306     @SuppressWarnings("removal")
 307     @CallerSensitive
 308     public Class<?> forClass() {
 309         if (cl == null) {
 310             return null;
 311         }
 312         requireInitialized();
 313         if (System.getSecurityManager() != null) {
 314             Class<?> caller = Reflection.getCallerClass();
 315             if (ReflectUtil.needsPackageAccessCheck(caller.getClassLoader(), cl.getClassLoader())) {
 316                 ReflectUtil.checkPackageAccess(cl);
 317             }
 318         }
 319         return cl;
 320     }
 321 
 322     /**
 323      * Return an array of the fields of this serializable class.
 324      *
 325      * @return  an array containing an element for each persistent field of
 326      *          this class. Returns an array of length zero if there are no
 327      *          fields.
 328      * @since 1.2
 329      */
 330     public ObjectStreamField[] getFields() {
 331         return getFields(true);
 332     }
 333 
 334     /**
 335      * Get the field of this class by name.
 336      *
 337      * @param   name the name of the data field to look for
 338      * @return  The ObjectStreamField object of the named field or null if
 339      *          there is no such named field.
 340      */
 341     public ObjectStreamField getField(String name) {
 342         return getField(name, null);
 343     }
 344 
 345     /**
 346      * Return a string describing this ObjectStreamClass.
 347      */
 348     public String toString() {
 349         return name + ": static final long serialVersionUID = " +
 350             getSerialVersionUID() + "L;";
 351     }
 352 
 353     /**
 354      * Looks up and returns class descriptor for given class, or null if class
 355      * is non-serializable and "all" is set to false.
 356      *
 357      * @param   cl class to look up
 358      * @param   all if true, return descriptors for all classes; if false, only
 359      *          return descriptors for serializable classes
 360      */
 361     static ObjectStreamClass lookup(Class<?> cl, boolean all) {
 362         if (!(all || Serializable.class.isAssignableFrom(cl))) {
 363             return null;
 364         }
 365         return Caches.localDescs.get(cl);
 366     }
 367 
 368     /**
 369      * Creates local class descriptor representing given class.
 370      */
 371     @SuppressWarnings("removal")
 372     private ObjectStreamClass(final Class<?> cl) {
 373         this.cl = cl;
 374         name = cl.getName();
 375         isProxy = Proxy.isProxyClass(cl);
 376         isEnum = Enum.class.isAssignableFrom(cl);
 377         isRecord = cl.isRecord();
 378         isValue = cl.isValue();
 379         serializable = Serializable.class.isAssignableFrom(cl);
 380         externalizable = Externalizable.class.isAssignableFrom(cl);
 381 
 382         Class<?> superCl = cl.getSuperclass();
 383         superDesc = (superCl != null) ? lookup(superCl, false) : null;
 384         localDesc = this;
 385 
 386         if (serializable) {
 387             AccessController.doPrivileged(new PrivilegedAction<>() {
 388                 public Void run() {
 389                     if (isEnum) {
 390                         suid = 0L;
 391                         fields = NO_FIELDS;
 392                         return null;
 393                     }
 394                     if (cl.isArray()) {
 395                         fields = NO_FIELDS;
 396                         return null;
 397                     }
 398 
 399                     suid = getDeclaredSUID(cl);
 400                     try {
 401                         fields = getSerialFields(cl);
 402                         computeFieldOffsets();
 403                     } catch (InvalidClassException e) {
 404                         serializeEx = deserializeEx =
 405                             new ExceptionInfo(e.classname, e.getMessage());
 406                         fields = NO_FIELDS;
 407                     }
 408 
 409                     if (isRecord) {
 410                         canonicalCtr = canonicalRecordCtr(cl);
 411                         deserializationCtrs = new DeserializationConstructorsCache();
 412                     } else if (isValue) {
 413                         // Value objects are created using Unsafe.
 414                         cons = null;
 415                     } else if (externalizable) {
 416                         cons = getExternalizableConstructor(cl);
 417                     } else {
 418                         cons = getSerializableConstructor(cl);
 419                         writeObjectMethod = getPrivateMethod(cl, "writeObject",
 420                             new Class<?>[] { ObjectOutputStream.class },
 421                             Void.TYPE);
 422                         readObjectMethod = getPrivateMethod(cl, "readObject",
 423                             new Class<?>[] { ObjectInputStream.class },
 424                             Void.TYPE);
 425                         readObjectNoDataMethod = getPrivateMethod(
 426                             cl, "readObjectNoData", null, Void.TYPE);
 427                         hasWriteObjectData = (writeObjectMethod != null);
 428                     }
 429                     domains = getProtectionDomains(cons, cl);
 430                     writeReplaceMethod = getInheritableMethod(
 431                         cl, "writeReplace", null, Object.class);
 432                     readResolveMethod = getInheritableMethod(
 433                         cl, "readResolve", null, Object.class);
 434                     return null;
 435                 }
 436             });
 437         } else {
 438             suid = 0L;
 439             fields = NO_FIELDS;
 440         }
 441 
 442         try {
 443             fieldRefl = getReflector(fields, this);
 444         } catch (InvalidClassException ex) {
 445             // field mismatches impossible when matching local fields vs. self
 446             throw new InternalError(ex);
 447         }
 448 
 449         if (deserializeEx == null) {
 450             if (isEnum) {
 451                 deserializeEx = new ExceptionInfo(name, "enum type");
 452             } else if (cons == null && !(isRecord | isValue)) {
 453                 deserializeEx = new ExceptionInfo(name, "no valid constructor");
 454             }
 455         }
 456         if (isRecord && canonicalCtr == null) {
 457             deserializeEx = new ExceptionInfo(name, "record canonical constructor not found");
 458         } else {
 459             for (int i = 0; i < fields.length; i++) {
 460                 if (fields[i].getField() == null) {
 461                     defaultSerializeEx = new ExceptionInfo(
 462                         name, "unmatched serializable field(s) declared");
 463                 }
 464             }
 465         }
 466         initialized = true;
 467     }
 468 
 469     /**
 470      * Creates blank class descriptor which should be initialized via a
 471      * subsequent call to initProxy(), initNonProxy() or readNonProxy().
 472      */
 473     ObjectStreamClass() {
 474     }
 475 
 476     /**
 477      * Creates a PermissionDomain that grants no permission.
 478      */
 479     private ProtectionDomain noPermissionsDomain() {
 480         PermissionCollection perms = new Permissions();
 481         perms.setReadOnly();
 482         return new ProtectionDomain(null, perms);
 483     }
 484 
 485     /**
 486      * Aggregate the ProtectionDomains of all the classes that separate
 487      * a concrete class {@code cl} from its ancestor's class declaring
 488      * a constructor {@code cons}.
 489      *
 490      * If {@code cl} is defined by the boot loader, or the constructor
 491      * {@code cons} is declared by {@code cl}, or if there is no security
 492      * manager, then this method does nothing and {@code null} is returned.
 493      *
 494      * @param cons A constructor declared by {@code cl} or one of its
 495      *             ancestors.
 496      * @param cl A concrete class, which is either the class declaring
 497      *           the constructor {@code cons}, or a serializable subclass
 498      *           of that class.
 499      * @return An array of ProtectionDomain representing the set of
 500      *         ProtectionDomain that separate the concrete class {@code cl}
 501      *         from its ancestor's declaring {@code cons}, or {@code null}.
 502      */
 503     @SuppressWarnings("removal")
 504     private ProtectionDomain[] getProtectionDomains(Constructor<?> cons,
 505                                                     Class<?> cl) {
 506         ProtectionDomain[] domains = null;
 507         if (cons != null && cl.getClassLoader() != null
 508                 && System.getSecurityManager() != null) {
 509             Class<?> cls = cl;
 510             Class<?> fnscl = cons.getDeclaringClass();
 511             Set<ProtectionDomain> pds = null;
 512             while (cls != fnscl) {
 513                 ProtectionDomain pd = cls.getProtectionDomain();
 514                 if (pd != null) {
 515                     if (pds == null) pds = new HashSet<>();
 516                     pds.add(pd);
 517                 }
 518                 cls = cls.getSuperclass();
 519                 if (cls == null) {
 520                     // that's not supposed to happen
 521                     // make a ProtectionDomain with no permission.
 522                     // should we throw instead?
 523                     if (pds == null) pds = new HashSet<>();
 524                     else pds.clear();
 525                     pds.add(noPermissionsDomain());
 526                     break;
 527                 }
 528             }
 529             if (pds != null) {
 530                 domains = pds.toArray(new ProtectionDomain[0]);
 531             }
 532         }
 533         return domains;
 534     }
 535 
 536     /**
 537      * Initializes class descriptor representing a proxy class.
 538      */
 539     void initProxy(Class<?> cl,
 540                    ClassNotFoundException resolveEx,
 541                    ObjectStreamClass superDesc)
 542         throws InvalidClassException
 543     {
 544         ObjectStreamClass osc = null;
 545         if (cl != null) {
 546             osc = lookup(cl, true);
 547             if (!osc.isProxy) {
 548                 throw new InvalidClassException(
 549                     "cannot bind proxy descriptor to a non-proxy class");
 550             }
 551         }
 552         this.cl = cl;
 553         this.resolveEx = resolveEx;
 554         this.superDesc = superDesc;
 555         isProxy = true;
 556         serializable = true;
 557         suid = 0L;
 558         fields = NO_FIELDS;
 559         if (osc != null) {
 560             localDesc = osc;
 561             name = localDesc.name;
 562             externalizable = localDesc.externalizable;
 563             writeReplaceMethod = localDesc.writeReplaceMethod;
 564             readResolveMethod = localDesc.readResolveMethod;
 565             deserializeEx = localDesc.deserializeEx;
 566             domains = localDesc.domains;
 567             cons = localDesc.cons;
 568         }
 569         fieldRefl = getReflector(fields, localDesc);
 570         initialized = true;
 571     }
 572 
 573     /**
 574      * Initializes class descriptor representing a non-proxy class.
 575      */
 576     void initNonProxy(ObjectStreamClass model,
 577                       Class<?> cl,
 578                       ClassNotFoundException resolveEx,
 579                       ObjectStreamClass superDesc)
 580         throws InvalidClassException
 581     {
 582         long suid = model.getSerialVersionUID();
 583         ObjectStreamClass osc = null;
 584         if (cl != null) {
 585             osc = lookup(cl, true);
 586             if (osc.isProxy) {
 587                 throw new InvalidClassException(
 588                         "cannot bind non-proxy descriptor to a proxy class");
 589             }
 590             if (model.isEnum != osc.isEnum) {
 591                 throw new InvalidClassException(model.isEnum ?
 592                         "cannot bind enum descriptor to a non-enum class" :
 593                         "cannot bind non-enum descriptor to an enum class");
 594             }
 595 
 596             if (model.serializable == osc.serializable &&
 597                     !cl.isArray() && !cl.isRecord() &&
 598                     suid != osc.getSerialVersionUID()) {
 599                 throw new InvalidClassException(osc.name,
 600                         "local class incompatible: " +
 601                                 "stream classdesc serialVersionUID = " + suid +
 602                                 ", local class serialVersionUID = " +
 603                                 osc.getSerialVersionUID());
 604             }
 605 
 606             if (!classNamesEqual(model.name, osc.name)) {
 607                 throw new InvalidClassException(osc.name,
 608                         "local class name incompatible with stream class " +
 609                                 "name \"" + model.name + "\"");
 610             }
 611 
 612             if (!model.isEnum) {
 613                 if ((model.serializable == osc.serializable) &&
 614                         (model.externalizable != osc.externalizable)) {
 615                     throw new InvalidClassException(osc.name,
 616                             "Serializable incompatible with Externalizable");
 617                 }
 618 
 619                 if ((model.serializable != osc.serializable) ||
 620                         (model.externalizable != osc.externalizable) ||
 621                         !(model.serializable || model.externalizable)) {
 622                     deserializeEx = new ExceptionInfo(
 623                             osc.name, "class invalid for deserialization");
 624                 }
 625             }
 626         }
 627 
 628         this.cl = cl;
 629         this.resolveEx = resolveEx;
 630         this.superDesc = superDesc;
 631         name = model.name;
 632         this.suid = suid;
 633         isProxy = false;
 634         isEnum = model.isEnum;
 635         serializable = model.serializable;
 636         externalizable = model.externalizable;
 637         hasBlockExternalData = model.hasBlockExternalData;
 638         hasWriteObjectData = model.hasWriteObjectData;
 639         fields = model.fields;
 640         primDataSize = model.primDataSize;
 641         numObjFields = model.numObjFields;
 642 
 643         if (osc != null) {
 644             localDesc = osc;
 645             isRecord = localDesc.isRecord;
 646             isValue = localDesc.isValue;
 647             // canonical record constructor is shared
 648             canonicalCtr = localDesc.canonicalCtr;
 649             // cache of deserialization constructors is shared
 650             deserializationCtrs = localDesc.deserializationCtrs;
 651             writeObjectMethod = localDesc.writeObjectMethod;
 652             readObjectMethod = localDesc.readObjectMethod;
 653             readObjectNoDataMethod = localDesc.readObjectNoDataMethod;
 654             writeReplaceMethod = localDesc.writeReplaceMethod;
 655             readResolveMethod = localDesc.readResolveMethod;
 656             if (deserializeEx == null) {
 657                 deserializeEx = localDesc.deserializeEx;
 658             }
 659             domains = localDesc.domains;
 660             assert cl.isRecord() ? localDesc.cons == null : true;
 661             cons = localDesc.cons;
 662         }
 663 
 664         fieldRefl = getReflector(fields, localDesc);
 665         // reassign to matched fields so as to reflect local unshared settings
 666         fields = fieldRefl.getFields();
 667 
 668         initialized = true;
 669     }
 670 
 671     /**
 672      * Reads non-proxy class descriptor information from given input stream.
 673      * The resulting class descriptor is not fully functional; it can only be
 674      * used as input to the ObjectInputStream.resolveClass() and
 675      * ObjectStreamClass.initNonProxy() methods.
 676      */
 677     void readNonProxy(ObjectInputStream in)
 678         throws IOException, ClassNotFoundException
 679     {
 680         name = in.readUTF();
 681         suid = in.readLong();
 682         isProxy = false;
 683 
 684         byte flags = in.readByte();
 685         hasWriteObjectData =
 686             ((flags & ObjectStreamConstants.SC_WRITE_METHOD) != 0);
 687         hasBlockExternalData =
 688             ((flags & ObjectStreamConstants.SC_BLOCK_DATA) != 0);
 689         externalizable =
 690             ((flags & ObjectStreamConstants.SC_EXTERNALIZABLE) != 0);
 691         boolean sflag =
 692             ((flags & ObjectStreamConstants.SC_SERIALIZABLE) != 0);
 693         if (externalizable && sflag) {
 694             throw new InvalidClassException(
 695                 name, "serializable and externalizable flags conflict");
 696         }
 697         serializable = externalizable || sflag;
 698         isEnum = ((flags & ObjectStreamConstants.SC_ENUM) != 0);
 699         if (isEnum && suid.longValue() != 0L) {
 700             throw new InvalidClassException(name,
 701                 "enum descriptor has non-zero serialVersionUID: " + suid);
 702         }
 703 
 704         int numFields = in.readShort();
 705         if (isEnum && numFields != 0) {
 706             throw new InvalidClassException(name,
 707                 "enum descriptor has non-zero field count: " + numFields);
 708         }
 709         fields = (numFields > 0) ?
 710             new ObjectStreamField[numFields] : NO_FIELDS;
 711         for (int i = 0; i < numFields; i++) {
 712             char tcode = (char) in.readByte();
 713             String fname = in.readUTF();
 714             String signature = ((tcode == 'L') || (tcode == '[')) ?
 715                 in.readTypeString() : String.valueOf(tcode);
 716             try {
 717                 fields[i] = new ObjectStreamField(fname, signature, false);
 718             } catch (RuntimeException e) {
 719                 throw new InvalidClassException(name,
 720                                                 "invalid descriptor for field " +
 721                                                 fname, e);
 722             }
 723         }
 724         computeFieldOffsets();
 725     }
 726 
 727     /**
 728      * Writes non-proxy class descriptor information to given output stream.
 729      */
 730     void writeNonProxy(ObjectOutputStream out) throws IOException {
 731         out.writeUTF(name);
 732         out.writeLong(getSerialVersionUID());
 733 
 734         byte flags = 0;
 735         if (externalizable) {
 736             flags |= ObjectStreamConstants.SC_EXTERNALIZABLE;
 737             int protocol = out.getProtocolVersion();
 738             if (protocol != ObjectStreamConstants.PROTOCOL_VERSION_1) {
 739                 flags |= ObjectStreamConstants.SC_BLOCK_DATA;
 740             }
 741         } else if (serializable) {
 742             flags |= ObjectStreamConstants.SC_SERIALIZABLE;
 743         }
 744         if (hasWriteObjectData) {
 745             flags |= ObjectStreamConstants.SC_WRITE_METHOD;
 746         }
 747         if (isEnum) {
 748             flags |= ObjectStreamConstants.SC_ENUM;
 749         }
 750         out.writeByte(flags);
 751 
 752         out.writeShort(fields.length);
 753         for (int i = 0; i < fields.length; i++) {
 754             ObjectStreamField f = fields[i];
 755             out.writeByte(f.getTypeCode());
 756             out.writeUTF(f.getName());
 757             if (!f.isPrimitive()) {
 758                 out.writeTypeString(f.getTypeString());
 759             }
 760         }
 761     }
 762 
 763     /**
 764      * Returns ClassNotFoundException (if any) thrown while attempting to
 765      * resolve local class corresponding to this class descriptor.
 766      */
 767     ClassNotFoundException getResolveException() {
 768         return resolveEx;
 769     }
 770 
 771     /**
 772      * Throws InternalError if not initialized.
 773      */
 774     private final void requireInitialized() {
 775         if (!initialized)
 776             throw new InternalError("Unexpected call when not initialized");
 777     }
 778 
 779     /**
 780      * Throws InvalidClassException if not initialized.
 781      * To be called in cases where an uninitialized class descriptor indicates
 782      * a problem in the serialization stream.
 783      */
 784     final void checkInitialized() throws InvalidClassException {
 785         if (!initialized) {
 786             throw new InvalidClassException("Class descriptor should be initialized");
 787         }
 788     }
 789 
 790     /**
 791      * Throws an InvalidClassException if object instances referencing this
 792      * class descriptor should not be allowed to deserialize.  This method does
 793      * not apply to deserialization of enum constants.
 794      */
 795     void checkDeserialize() throws InvalidClassException {
 796         requireInitialized();
 797         if (deserializeEx != null) {
 798             throw deserializeEx.newInvalidClassException();
 799         }
 800     }
 801 
 802     /**
 803      * Throws an InvalidClassException if objects whose class is represented by
 804      * this descriptor should not be allowed to serialize.  This method does
 805      * not apply to serialization of enum constants.
 806      */
 807     void checkSerialize() throws InvalidClassException {
 808         requireInitialized();
 809         if (serializeEx != null) {
 810             throw serializeEx.newInvalidClassException();
 811         }
 812     }
 813 
 814     /**
 815      * Throws an InvalidClassException if objects whose class is represented by
 816      * this descriptor should not be permitted to use default serialization
 817      * (e.g., if the class declares serializable fields that do not correspond
 818      * to actual fields, and hence must use the GetField API).  This method
 819      * does not apply to deserialization of enum constants.
 820      */
 821     void checkDefaultSerialize() throws InvalidClassException {
 822         requireInitialized();
 823         if (defaultSerializeEx != null) {
 824             throw defaultSerializeEx.newInvalidClassException();
 825         }
 826     }
 827 
 828     /**
 829      * Returns superclass descriptor.  Note that on the receiving side, the
 830      * superclass descriptor may be bound to a class that is not a superclass
 831      * of the subclass descriptor's bound class.
 832      */
 833     ObjectStreamClass getSuperDesc() {
 834         requireInitialized();
 835         return superDesc;
 836     }
 837 
 838     /**
 839      * Returns the "local" class descriptor for the class associated with this
 840      * class descriptor (i.e., the result of
 841      * ObjectStreamClass.lookup(this.forClass())) or null if there is no class
 842      * associated with this descriptor.
 843      */
 844     ObjectStreamClass getLocalDesc() {
 845         requireInitialized();
 846         return localDesc;
 847     }
 848 
 849     /**
 850      * Returns arrays of ObjectStreamFields representing the serializable
 851      * fields of the represented class.  If copy is true, a clone of this class
 852      * descriptor's field array is returned, otherwise the array itself is
 853      * returned.
 854      */
 855     ObjectStreamField[] getFields(boolean copy) {
 856         return copy ? fields.clone() : fields;
 857     }
 858 
 859     /**
 860      * Looks up a serializable field of the represented class by name and type.
 861      * A specified type of null matches all types, Object.class matches all
 862      * non-primitive types, and any other non-null type matches assignable
 863      * types only.  Returns matching field, or null if no match found.
 864      */
 865     ObjectStreamField getField(String name, Class<?> type) {
 866         for (int i = 0; i < fields.length; i++) {
 867             ObjectStreamField f = fields[i];
 868             if (f.getName().equals(name)) {
 869                 if (type == null ||
 870                     (type == Object.class && !f.isPrimitive()))
 871                 {
 872                     return f;
 873                 }
 874                 Class<?> ftype = f.getType();
 875                 if (ftype != null && type.isAssignableFrom(ftype)) {
 876                     return f;
 877                 }
 878             }
 879         }
 880         return null;
 881     }
 882 
 883     /**
 884      * Returns true if class descriptor represents a dynamic proxy class, false
 885      * otherwise.
 886      */
 887     boolean isProxy() {
 888         requireInitialized();
 889         return isProxy;
 890     }
 891 
 892     /**
 893      * Returns true if class descriptor represents an enum type, false
 894      * otherwise.
 895      */
 896     boolean isEnum() {
 897         requireInitialized();
 898         return isEnum;
 899     }
 900 
 901     /**
 902      * Returns true if class descriptor represents a record type, false
 903      * otherwise.
 904      */
 905     boolean isRecord() {
 906         requireInitialized();
 907         return isRecord;
 908     }
 909 
 910     /**
 911      * Returns true if represented class implements Externalizable, false
 912      * otherwise.
 913      */
 914     boolean isExternalizable() {
 915         requireInitialized();
 916         return externalizable;
 917     }
 918 
 919     /**
 920      * Returns true if represented class implements Serializable, false
 921      * otherwise.
 922      */
 923     boolean isSerializable() {
 924         requireInitialized();
 925         return serializable;
 926     }
 927 
 928     /**
 929      * {@return {code true} if the class is a value class, {@code false} otherwise}
 930      */
 931     boolean isValue() {
 932         requireInitialized();
 933         return isValue;
 934     }
 935 
 936     /**
 937      * Returns true if class descriptor represents externalizable class that
 938      * has written its data in 1.2 (block data) format, false otherwise.
 939      */
 940     boolean hasBlockExternalData() {
 941         requireInitialized();
 942         return hasBlockExternalData;
 943     }
 944 
 945     /**
 946      * Returns true if class descriptor represents serializable (but not
 947      * externalizable) class which has written its data via a custom
 948      * writeObject() method, false otherwise.
 949      */
 950     boolean hasWriteObjectData() {
 951         requireInitialized();
 952         return hasWriteObjectData;
 953     }
 954 
 955     /**
 956      * Returns true if represented class is serializable/externalizable and can
 957      * be instantiated by the serialization runtime--i.e., if it is
 958      * externalizable and defines a public no-arg constructor, if it is
 959      * non-externalizable and its first non-serializable superclass defines an
 960      * accessible no-arg constructor, or if the class is a value class.
 961      * Otherwise, returns false.
 962      */
 963     boolean isInstantiable() {
 964         requireInitialized();
 965         return (cons != null | isValue);
 966     }
 967 
 968     /**
 969      * Returns true if represented class is serializable (but not
 970      * externalizable) and defines a conformant writeObject method.  Otherwise,
 971      * returns false.
 972      */
 973     boolean hasWriteObjectMethod() {
 974         requireInitialized();
 975         return (writeObjectMethod != null);
 976     }
 977 
 978     /**
 979      * Returns true if represented class is serializable (but not
 980      * externalizable) and defines a conformant readObject method.  Otherwise,
 981      * returns false.
 982      */
 983     boolean hasReadObjectMethod() {
 984         requireInitialized();
 985         return (readObjectMethod != null);
 986     }
 987 
 988     /**
 989      * Returns true if represented class is serializable (but not
 990      * externalizable) and defines a conformant readObjectNoData method.
 991      * Otherwise, returns false.
 992      */
 993     boolean hasReadObjectNoDataMethod() {
 994         requireInitialized();
 995         return (readObjectNoDataMethod != null);
 996     }
 997 
 998     /**
 999      * Returns true if represented class is serializable or externalizable and
1000      * defines a conformant writeReplace method.  Otherwise, returns false.
1001      */
1002     boolean hasWriteReplaceMethod() {
1003         requireInitialized();
1004         return (writeReplaceMethod != null);
1005     }
1006 
1007     /**
1008      * Returns true if represented class is serializable or externalizable and
1009      * defines a conformant readResolve method.  Otherwise, returns false.
1010      */
1011     boolean hasReadResolveMethod() {
1012         requireInitialized();
1013         return (readResolveMethod != null);
1014     }
1015 
1016     /**
1017      * Creates a new instance of the represented class.  If the class is
1018      * externalizable, invokes its public no-arg constructor; otherwise, if the
1019      * class is serializable, invokes the no-arg constructor of the first
1020      * non-serializable superclass.  Throws UnsupportedOperationException if
1021      * this class descriptor is not associated with a class, if the associated
1022      * class is non-serializable or if the appropriate no-arg constructor is
1023      * inaccessible/unavailable.
1024      */
1025     @SuppressWarnings("removal")
1026     Object newInstance()
1027         throws InstantiationException, InvocationTargetException,
1028                UnsupportedOperationException
1029     {
1030         requireInitialized();
1031         if (cons != null) {
1032             try {
1033                 if (domains == null || domains.length == 0) {
1034                     return cons.newInstance();
1035                 } else {
1036                     JavaSecurityAccess jsa = SharedSecrets.getJavaSecurityAccess();
1037                     PrivilegedAction<?> pea = () -> {
1038                         try {
1039                             return cons.newInstance();
1040                         } catch (InstantiationException
1041                                  | InvocationTargetException
1042                                  | IllegalAccessException x) {
1043                             throw new UndeclaredThrowableException(x);
1044                         }
1045                     }; // Can't use PrivilegedExceptionAction with jsa
1046                     try {
1047                         return jsa.doIntersectionPrivilege(pea,
1048                                    AccessController.getContext(),
1049                                    new AccessControlContext(domains));
1050                     } catch (UndeclaredThrowableException x) {
1051                         Throwable cause = x.getCause();
1052                         if (cause instanceof InstantiationException)
1053                             throw (InstantiationException) cause;
1054                         if (cause instanceof InvocationTargetException)
1055                             throw (InvocationTargetException) cause;
1056                         if (cause instanceof IllegalAccessException)
1057                             throw (IllegalAccessException) cause;
1058                         // not supposed to happen
1059                         throw x;
1060                     }
1061                 }
1062             } catch (IllegalAccessException ex) {
1063                 // should not occur, as access checks have been suppressed
1064                 throw new InternalError(ex);
1065             } catch (InstantiationError err) {
1066                 var ex = new InstantiationException();
1067                 ex.initCause(err);
1068                 throw ex;
1069             }
1070         } else if (isValue) {
1071             // Start with a buffered default value.
1072             return FieldReflector.newValueInstance(cl);
1073         }  else {
1074             throw new UnsupportedOperationException();
1075         }
1076     }
1077 
1078     /**
1079      * Finish the initialization of a value object.
1080      * @param obj an object (larval if a value object)
1081      * @return the finished object
1082      */
1083     Object finishValue(Object obj) {
1084         return (isValue) ? FieldReflector.finishValueInstance(obj) : obj;
1085     }
1086 
1087     /**
1088      * Invokes the writeObject method of the represented serializable class.
1089      * Throws UnsupportedOperationException if this class descriptor is not
1090      * associated with a class, or if the class is externalizable,
1091      * non-serializable or does not define writeObject.
1092      */
1093     void invokeWriteObject(Object obj, ObjectOutputStream out)
1094         throws IOException, UnsupportedOperationException
1095     {
1096         requireInitialized();
1097         if (writeObjectMethod != null) {
1098             try {
1099                 writeObjectMethod.invoke(obj, new Object[]{ out });
1100             } catch (InvocationTargetException ex) {
1101                 Throwable th = ex.getCause();
1102                 if (th instanceof IOException) {
1103                     throw (IOException) th;
1104                 } else {
1105                     throwMiscException(th);
1106                 }
1107             } catch (IllegalAccessException ex) {
1108                 // should not occur, as access checks have been suppressed
1109                 throw new InternalError(ex);
1110             }
1111         } else {
1112             throw new UnsupportedOperationException();
1113         }
1114     }
1115 
1116     /**
1117      * Invokes the readObject method of the represented serializable class.
1118      * Throws UnsupportedOperationException if this class descriptor is not
1119      * associated with a class, or if the class is externalizable,
1120      * non-serializable or does not define readObject.
1121      */
1122     void invokeReadObject(Object obj, ObjectInputStream in)
1123         throws ClassNotFoundException, IOException,
1124                UnsupportedOperationException
1125     {
1126         requireInitialized();
1127         if (readObjectMethod != null) {
1128             try {
1129                 readObjectMethod.invoke(obj, new Object[]{ in });
1130             } catch (InvocationTargetException ex) {
1131                 Throwable th = ex.getCause();
1132                 if (th instanceof ClassNotFoundException) {
1133                     throw (ClassNotFoundException) th;
1134                 } else if (th instanceof IOException) {
1135                     throw (IOException) th;
1136                 } else {
1137                     throwMiscException(th);
1138                 }
1139             } catch (IllegalAccessException ex) {
1140                 // should not occur, as access checks have been suppressed
1141                 throw new InternalError(ex);
1142             }
1143         } else {
1144             throw new UnsupportedOperationException();
1145         }
1146     }
1147 
1148     /**
1149      * Invokes the readObjectNoData method of the represented serializable
1150      * class.  Throws UnsupportedOperationException if this class descriptor is
1151      * not associated with a class, or if the class is externalizable,
1152      * non-serializable or does not define readObjectNoData.
1153      */
1154     void invokeReadObjectNoData(Object obj)
1155         throws IOException, UnsupportedOperationException
1156     {
1157         requireInitialized();
1158         if (readObjectNoDataMethod != null) {
1159             try {
1160                 readObjectNoDataMethod.invoke(obj, (Object[]) null);
1161             } catch (InvocationTargetException ex) {
1162                 Throwable th = ex.getCause();
1163                 if (th instanceof ObjectStreamException) {
1164                     throw (ObjectStreamException) th;
1165                 } else {
1166                     throwMiscException(th);
1167                 }
1168             } catch (IllegalAccessException ex) {
1169                 // should not occur, as access checks have been suppressed
1170                 throw new InternalError(ex);
1171             }
1172         } else {
1173             throw new UnsupportedOperationException();
1174         }
1175     }
1176 
1177     /**
1178      * Invokes the writeReplace method of the represented serializable class and
1179      * returns the result.  Throws UnsupportedOperationException if this class
1180      * descriptor is not associated with a class, or if the class is
1181      * non-serializable or does not define writeReplace.
1182      */
1183     Object invokeWriteReplace(Object obj)
1184         throws IOException, UnsupportedOperationException
1185     {
1186         requireInitialized();
1187         if (writeReplaceMethod != null) {
1188             try {
1189                 return writeReplaceMethod.invoke(obj, (Object[]) null);
1190             } catch (InvocationTargetException ex) {
1191                 Throwable th = ex.getCause();
1192                 if (th instanceof ObjectStreamException) {
1193                     throw (ObjectStreamException) th;
1194                 } else {
1195                     throwMiscException(th);
1196                     throw new InternalError(th);  // never reached
1197                 }
1198             } catch (IllegalAccessException ex) {
1199                 // should not occur, as access checks have been suppressed
1200                 throw new InternalError(ex);
1201             }
1202         } else {
1203             throw new UnsupportedOperationException();
1204         }
1205     }
1206 
1207     /**
1208      * Invokes the readResolve method of the represented serializable class and
1209      * returns the result.  Throws UnsupportedOperationException if this class
1210      * descriptor is not associated with a class, or if the class is
1211      * non-serializable or does not define readResolve.
1212      */
1213     Object invokeReadResolve(Object obj)
1214         throws IOException, UnsupportedOperationException
1215     {
1216         requireInitialized();
1217         if (readResolveMethod != null) {
1218             try {
1219                 return readResolveMethod.invoke(obj, (Object[]) null);
1220             } catch (InvocationTargetException ex) {
1221                 Throwable th = ex.getCause();
1222                 if (th instanceof ObjectStreamException) {
1223                     throw (ObjectStreamException) th;
1224                 } else {
1225                     throwMiscException(th);
1226                     throw new InternalError(th);  // never reached
1227                 }
1228             } catch (IllegalAccessException ex) {
1229                 // should not occur, as access checks have been suppressed
1230                 throw new InternalError(ex);
1231             }
1232         } else {
1233             throw new UnsupportedOperationException();
1234         }
1235     }
1236 
1237     /**
1238      * Class representing the portion of an object's serialized form allotted
1239      * to data described by a given class descriptor.  If "hasData" is false,
1240      * the object's serialized form does not contain data associated with the
1241      * class descriptor.
1242      */
1243     static class ClassDataSlot {
1244 
1245         /** class descriptor "occupying" this slot */
1246         final ObjectStreamClass desc;
1247         /** true if serialized form includes data for this slot's descriptor */
1248         final boolean hasData;
1249 
1250         ClassDataSlot(ObjectStreamClass desc, boolean hasData) {
1251             this.desc = desc;
1252             this.hasData = hasData;
1253         }
1254     }
1255 
1256     /**
1257      * Returns array of ClassDataSlot instances representing the data layout
1258      * (including superclass data) for serialized objects described by this
1259      * class descriptor.  ClassDataSlots are ordered by inheritance with those
1260      * containing "higher" superclasses appearing first.  The final
1261      * ClassDataSlot contains a reference to this descriptor.
1262      */
1263     ClassDataSlot[] getClassDataLayout() throws InvalidClassException {
1264         // REMIND: synchronize instead of relying on volatile?
1265         if (dataLayout == null) {
1266             dataLayout = getClassDataLayout0();
1267         }
1268         return dataLayout;
1269     }
1270 
1271     private ClassDataSlot[] getClassDataLayout0()
1272         throws InvalidClassException
1273     {
1274         ArrayList<ClassDataSlot> slots = new ArrayList<>();
1275         Class<?> start = cl, end = cl;
1276 
1277         // locate closest non-serializable superclass
1278         while (end != null && Serializable.class.isAssignableFrom(end)) {
1279             end = end.getSuperclass();
1280         }
1281 
1282         HashSet<String> oscNames = new HashSet<>(3);
1283 
1284         for (ObjectStreamClass d = this; d != null; d = d.superDesc) {
1285             if (oscNames.contains(d.name)) {
1286                 throw new InvalidClassException("Circular reference.");
1287             } else {
1288                 oscNames.add(d.name);
1289             }
1290 
1291             // search up inheritance hierarchy for class with matching name
1292             String searchName = (d.cl != null) ? d.cl.getName() : d.name;
1293             Class<?> match = null;
1294             for (Class<?> c = start; c != end; c = c.getSuperclass()) {
1295                 if (searchName.equals(c.getName())) {
1296                     match = c;
1297                     break;
1298                 }
1299             }
1300 
1301             // add "no data" slot for each unmatched class below match
1302             if (match != null) {
1303                 for (Class<?> c = start; c != match; c = c.getSuperclass()) {
1304                     slots.add(new ClassDataSlot(
1305                         ObjectStreamClass.lookup(c, true), false));
1306                 }
1307                 start = match.getSuperclass();
1308             }
1309 
1310             // record descriptor/class pairing
1311             slots.add(new ClassDataSlot(d.getVariantFor(match), true));
1312         }
1313 
1314         // add "no data" slot for any leftover unmatched classes
1315         for (Class<?> c = start; c != end; c = c.getSuperclass()) {
1316             slots.add(new ClassDataSlot(
1317                 ObjectStreamClass.lookup(c, true), false));
1318         }
1319 
1320         // order slots from superclass -> subclass
1321         Collections.reverse(slots);
1322         return slots.toArray(new ClassDataSlot[slots.size()]);
1323     }
1324 
1325     /**
1326      * Returns aggregate size (in bytes) of marshalled primitive field values
1327      * for represented class.
1328      */
1329     int getPrimDataSize() {
1330         return primDataSize;
1331     }
1332 
1333     /**
1334      * Returns number of non-primitive serializable fields of represented
1335      * class.
1336      */
1337     int getNumObjFields() {
1338         return numObjFields;
1339     }
1340 
1341     /**
1342      * Fetches the serializable primitive field values of object obj and
1343      * marshals them into byte array buf starting at offset 0.  It is the
1344      * responsibility of the caller to ensure that obj is of the proper type if
1345      * non-null.
1346      */
1347     void getPrimFieldValues(Object obj, byte[] buf) {
1348         fieldRefl.getPrimFieldValues(obj, buf);
1349     }
1350 
1351     /**
1352      * Sets the serializable primitive fields of object obj using values
1353      * unmarshalled from byte array buf starting at offset 0.  It is the
1354      * responsibility of the caller to ensure that obj is of the proper type if
1355      * non-null.
1356      */
1357     void setPrimFieldValues(Object obj, byte[] buf) {
1358         fieldRefl.setPrimFieldValues(obj, buf);
1359     }
1360 
1361     /**
1362      * Fetches the serializable object field values of object obj and stores
1363      * them in array vals starting at offset 0.  It is the responsibility of
1364      * the caller to ensure that obj is of the proper type if non-null.
1365      */
1366     void getObjFieldValues(Object obj, Object[] vals) {
1367         fieldRefl.getObjFieldValues(obj, vals);
1368     }
1369 
1370     /**
1371      * Checks that the given values, from array vals starting at offset 0,
1372      * are assignable to the given serializable object fields.
1373      * @throws ClassCastException if any value is not assignable
1374      */
1375     void checkObjFieldValueTypes(Object obj, Object[] vals) {
1376         fieldRefl.checkObjectFieldValueTypes(obj, vals);
1377     }
1378 
1379     /**
1380      * Sets the serializable object fields of object obj using values from
1381      * array vals starting at offset 0.  It is the responsibility of the caller
1382      * to ensure that obj is of the proper type if non-null.
1383      */
1384     void setObjFieldValues(Object obj, Object[] vals) {
1385         fieldRefl.setObjFieldValues(obj, vals);
1386     }
1387 
1388     /**
1389      * Calculates and sets serializable field offsets, as well as primitive
1390      * data size and object field count totals.  Throws InvalidClassException
1391      * if fields are illegally ordered.
1392      */
1393     private void computeFieldOffsets() throws InvalidClassException {
1394         primDataSize = 0;
1395         numObjFields = 0;
1396         int firstObjIndex = -1;
1397 
1398         for (int i = 0; i < fields.length; i++) {
1399             ObjectStreamField f = fields[i];
1400             switch (f.getTypeCode()) {
1401                 case 'Z', 'B' -> f.setOffset(primDataSize++);
1402                 case 'C', 'S' -> {
1403                     f.setOffset(primDataSize);
1404                     primDataSize += 2;
1405                 }
1406                 case 'I', 'F' -> {
1407                     f.setOffset(primDataSize);
1408                     primDataSize += 4;
1409                 }
1410                 case 'J', 'D' -> {
1411                     f.setOffset(primDataSize);
1412                     primDataSize += 8;
1413                 }
1414                 case '[', 'L' -> {
1415                     f.setOffset(numObjFields++);
1416                     if (firstObjIndex == -1) {
1417                         firstObjIndex = i;
1418                     }
1419                 }
1420                 default -> throw new InternalError();
1421             }
1422         }
1423         if (firstObjIndex != -1 &&
1424             firstObjIndex + numObjFields != fields.length)
1425         {
1426             throw new InvalidClassException(name, "illegal field order");
1427         }
1428     }
1429 
1430     /**
1431      * If given class is the same as the class associated with this class
1432      * descriptor, returns reference to this class descriptor.  Otherwise,
1433      * returns variant of this class descriptor bound to given class.
1434      */
1435     private ObjectStreamClass getVariantFor(Class<?> cl)
1436         throws InvalidClassException
1437     {
1438         if (this.cl == cl) {
1439             return this;
1440         }
1441         ObjectStreamClass desc = new ObjectStreamClass();
1442         if (isProxy) {
1443             desc.initProxy(cl, null, superDesc);
1444         } else {
1445             desc.initNonProxy(this, cl, null, superDesc);
1446         }
1447         return desc;
1448     }
1449 
1450     /**
1451      * Returns public no-arg constructor of given class, or null if none found.
1452      * Access checks are disabled on the returned constructor (if any), since
1453      * the defining class may still be non-public.
1454      */
1455     private static Constructor<?> getExternalizableConstructor(Class<?> cl) {
1456         try {
1457             Constructor<?> cons = cl.getDeclaredConstructor((Class<?>[]) null);
1458             cons.setAccessible(true);
1459             return ((cons.getModifiers() & Modifier.PUBLIC) != 0) ?
1460                 cons : null;
1461         } catch (NoSuchMethodException | InaccessibleObjectException ex) {
1462             return null;
1463         }
1464     }
1465 
1466     /**
1467      * Returns subclass-accessible no-arg constructor of first non-serializable
1468      * superclass, or null if none found.  Access checks are disabled on the
1469      * returned constructor (if any).
1470      */
1471     private static Constructor<?> getSerializableConstructor(Class<?> cl) {
1472         return reflFactory.newConstructorForSerialization(cl);
1473     }
1474 
1475     /**
1476      * Returns the canonical constructor for the given record class, or null if
1477      * the not found ( which should never happen for correctly generated record
1478      * classes ).
1479      */
1480     @SuppressWarnings("removal")
1481     private static MethodHandle canonicalRecordCtr(Class<?> cls) {
1482         assert cls.isRecord() : "Expected record, got: " + cls;
1483         PrivilegedAction<MethodHandle> pa = () -> {
1484             Class<?>[] paramTypes = Arrays.stream(cls.getRecordComponents())
1485                                           .map(RecordComponent::getType)
1486                                           .toArray(Class<?>[]::new);
1487             try {
1488                 Constructor<?> ctr = cls.getDeclaredConstructor(paramTypes);
1489                 ctr.setAccessible(true);
1490                 return MethodHandles.lookup().unreflectConstructor(ctr);
1491             } catch (IllegalAccessException | NoSuchMethodException e) {
1492                 return null;
1493             }
1494         };
1495         return AccessController.doPrivileged(pa);
1496     }
1497 
1498     /**
1499      * Returns the canonical constructor, if the local class equivalent of this
1500      * stream class descriptor is a record class, otherwise null.
1501      */
1502     MethodHandle getRecordConstructor() {
1503         return canonicalCtr;
1504     }
1505 
1506     /**
1507      * Returns non-static, non-abstract method with given signature provided it
1508      * is defined by or accessible (via inheritance) by the given class, or
1509      * null if no match found.  Access checks are disabled on the returned
1510      * method (if any).
1511      */
1512     private static Method getInheritableMethod(Class<?> cl, String name,
1513                                                Class<?>[] argTypes,
1514                                                Class<?> returnType)
1515     {
1516         Method meth = null;
1517         Class<?> defCl = cl;
1518         while (defCl != null) {
1519             try {
1520                 meth = defCl.getDeclaredMethod(name, argTypes);
1521                 break;
1522             } catch (NoSuchMethodException ex) {
1523                 defCl = defCl.getSuperclass();
1524             }
1525         }
1526 
1527         if ((meth == null) || (meth.getReturnType() != returnType)) {
1528             return null;
1529         }
1530         meth.setAccessible(true);
1531         int mods = meth.getModifiers();
1532         if ((mods & (Modifier.STATIC | Modifier.ABSTRACT)) != 0) {
1533             return null;
1534         } else if ((mods & (Modifier.PUBLIC | Modifier.PROTECTED)) != 0) {
1535             return meth;
1536         } else if ((mods & Modifier.PRIVATE) != 0) {
1537             return (cl == defCl) ? meth : null;
1538         } else {
1539             return packageEquals(cl, defCl) ? meth : null;
1540         }
1541     }
1542 
1543     /**
1544      * Returns non-static private method with given signature defined by given
1545      * class, or null if none found.  Access checks are disabled on the
1546      * returned method (if any).
1547      */
1548     private static Method getPrivateMethod(Class<?> cl, String name,
1549                                            Class<?>[] argTypes,
1550                                            Class<?> returnType)
1551     {
1552         try {
1553             Method meth = cl.getDeclaredMethod(name, argTypes);
1554             meth.setAccessible(true);
1555             int mods = meth.getModifiers();
1556             return ((meth.getReturnType() == returnType) &&
1557                     ((mods & Modifier.STATIC) == 0) &&
1558                     ((mods & Modifier.PRIVATE) != 0)) ? meth : null;
1559         } catch (NoSuchMethodException ex) {
1560             return null;
1561         }
1562     }
1563 
1564     /**
1565      * Returns true if classes are defined in the same runtime package, false
1566      * otherwise.
1567      */
1568     private static boolean packageEquals(Class<?> cl1, Class<?> cl2) {
1569         return cl1.getClassLoader() == cl2.getClassLoader() &&
1570                 cl1.getPackageName() == cl2.getPackageName();
1571     }
1572 
1573     /**
1574      * Compares class names for equality, ignoring package names.  Returns true
1575      * if class names equal, false otherwise.
1576      */
1577     private static boolean classNamesEqual(String name1, String name2) {
1578         int idx1 = name1.lastIndexOf('.') + 1;
1579         int idx2 = name2.lastIndexOf('.') + 1;
1580         int len1 = name1.length() - idx1;
1581         int len2 = name2.length() - idx2;
1582         return len1 == len2 &&
1583                 name1.regionMatches(idx1, name2, idx2, len1);
1584     }
1585 
1586     /**
1587      * Returns JVM type signature for given list of parameters and return type.
1588      */
1589     private static String getMethodSignature(Class<?>[] paramTypes,
1590                                              Class<?> retType)
1591     {
1592         StringBuilder sb = new StringBuilder();
1593         sb.append('(');
1594         for (int i = 0; i < paramTypes.length; i++) {
1595             sb.append(paramTypes[i].descriptorString());
1596         }
1597         sb.append(')');
1598         sb.append(retType.descriptorString());
1599         return sb.toString();
1600     }
1601 
1602     /**
1603      * Convenience method for throwing an exception that is either a
1604      * RuntimeException, Error, or of some unexpected type (in which case it is
1605      * wrapped inside an IOException).
1606      */
1607     private static void throwMiscException(Throwable th) throws IOException {
1608         if (th instanceof RuntimeException) {
1609             throw (RuntimeException) th;
1610         } else if (th instanceof Error) {
1611             throw (Error) th;
1612         } else {
1613             throw new IOException("unexpected exception type", th);
1614         }
1615     }
1616 
1617     /**
1618      * Returns ObjectStreamField array describing the serializable fields of
1619      * the given class.  Serializable fields backed by an actual field of the
1620      * class are represented by ObjectStreamFields with corresponding non-null
1621      * Field objects.  Throws InvalidClassException if the (explicitly
1622      * declared) serializable fields are invalid.
1623      */
1624     private static ObjectStreamField[] getSerialFields(Class<?> cl)
1625         throws InvalidClassException
1626     {
1627         if (!Serializable.class.isAssignableFrom(cl))
1628             return NO_FIELDS;
1629 
1630         ObjectStreamField[] fields;
1631         if (cl.isRecord()) {
1632             fields = getDefaultSerialFields(cl);
1633             Arrays.sort(fields);
1634         } else if (!Externalizable.class.isAssignableFrom(cl) &&
1635             !Proxy.isProxyClass(cl) &&
1636                    !cl.isInterface()) {
1637             if ((fields = getDeclaredSerialFields(cl)) == null) {
1638                 fields = getDefaultSerialFields(cl);
1639             }
1640             Arrays.sort(fields);
1641         } else {
1642             fields = NO_FIELDS;
1643         }
1644         return fields;
1645     }
1646 
1647     /**
1648      * Returns serializable fields of given class as defined explicitly by a
1649      * "serialPersistentFields" field, or null if no appropriate
1650      * "serialPersistentFields" field is defined.  Serializable fields backed
1651      * by an actual field of the class are represented by ObjectStreamFields
1652      * with corresponding non-null Field objects.  For compatibility with past
1653      * releases, a "serialPersistentFields" field with a null value is
1654      * considered equivalent to not declaring "serialPersistentFields".  Throws
1655      * InvalidClassException if the declared serializable fields are
1656      * invalid--e.g., if multiple fields share the same name.
1657      */
1658     private static ObjectStreamField[] getDeclaredSerialFields(Class<?> cl)
1659         throws InvalidClassException
1660     {
1661         ObjectStreamField[] serialPersistentFields = null;
1662         try {
1663             Field f = cl.getDeclaredField("serialPersistentFields");
1664             int mask = Modifier.PRIVATE | Modifier.STATIC | Modifier.FINAL;
1665             if ((f.getModifiers() & mask) == mask) {
1666                 f.setAccessible(true);
1667                 serialPersistentFields = (ObjectStreamField[]) f.get(null);
1668             }
1669         } catch (Exception ex) {
1670         }
1671         if (serialPersistentFields == null) {
1672             return null;
1673         } else if (serialPersistentFields.length == 0) {
1674             return NO_FIELDS;
1675         }
1676 
1677         ObjectStreamField[] boundFields =
1678             new ObjectStreamField[serialPersistentFields.length];
1679         Set<String> fieldNames = HashSet.newHashSet(serialPersistentFields.length);
1680 
1681         for (int i = 0; i < serialPersistentFields.length; i++) {
1682             ObjectStreamField spf = serialPersistentFields[i];
1683 
1684             String fname = spf.getName();
1685             if (fieldNames.contains(fname)) {
1686                 throw new InvalidClassException(
1687                     "multiple serializable fields named " + fname);
1688             }
1689             fieldNames.add(fname);
1690 
1691             try {
1692                 Field f = cl.getDeclaredField(fname);
1693                 if ((f.getType() == spf.getType()) &&
1694                     ((f.getModifiers() & Modifier.STATIC) == 0))
1695                 {
1696                     boundFields[i] =
1697                         new ObjectStreamField(f, spf.isUnshared(), true);
1698                 }
1699             } catch (NoSuchFieldException ex) {
1700             }
1701             if (boundFields[i] == null) {
1702                 boundFields[i] = new ObjectStreamField(
1703                     fname, spf.getType(), spf.isUnshared());
1704             }
1705         }
1706         return boundFields;
1707     }
1708 
1709     /**
1710      * Returns array of ObjectStreamFields corresponding to all non-static
1711      * non-transient fields declared by given class.  Each ObjectStreamField
1712      * contains a Field object for the field it represents.  If no default
1713      * serializable fields exist, NO_FIELDS is returned.
1714      */
1715     private static ObjectStreamField[] getDefaultSerialFields(Class<?> cl) {
1716         Field[] clFields = cl.getDeclaredFields();
1717         ArrayList<ObjectStreamField> list = new ArrayList<>();
1718         int mask = Modifier.STATIC | Modifier.TRANSIENT;
1719 
1720         for (int i = 0; i < clFields.length; i++) {
1721             if ((clFields[i].getModifiers() & mask) == 0) {
1722                 list.add(new ObjectStreamField(clFields[i], false, true));
1723             }
1724         }
1725         int size = list.size();
1726         return (size == 0) ? NO_FIELDS :
1727             list.toArray(new ObjectStreamField[size]);
1728     }
1729 
1730     /**
1731      * Returns explicit serial version UID value declared by given class, or
1732      * null if none.
1733      */
1734     private static Long getDeclaredSUID(Class<?> cl) {
1735         try {
1736             Field f = cl.getDeclaredField("serialVersionUID");
1737             int mask = Modifier.STATIC | Modifier.FINAL;
1738             if ((f.getModifiers() & mask) == mask) {
1739                 f.setAccessible(true);
1740                 return f.getLong(null);
1741             }
1742         } catch (Exception ex) {
1743         }
1744         return null;
1745     }
1746 
1747     /**
1748      * Computes the default serial version UID value for the given class.
1749      */
1750     private static long computeDefaultSUID(Class<?> cl) {
1751         if (!Serializable.class.isAssignableFrom(cl) || Proxy.isProxyClass(cl))
1752         {
1753             return 0L;
1754         }
1755 
1756         try {
1757             ByteArrayOutputStream bout = new ByteArrayOutputStream();
1758             DataOutputStream dout = new DataOutputStream(bout);
1759 
1760             dout.writeUTF(cl.getName());
1761 
1762             int classMods = cl.getModifiers() &
1763                 (Modifier.PUBLIC | Modifier.FINAL |
1764                  Modifier.INTERFACE | Modifier.ABSTRACT);
1765 
1766             /*
1767              * compensate for javac bug in which ABSTRACT bit was set for an
1768              * interface only if the interface declared methods
1769              */
1770             Method[] methods = cl.getDeclaredMethods();
1771             if ((classMods & Modifier.INTERFACE) != 0) {
1772                 classMods = (methods.length > 0) ?
1773                     (classMods | Modifier.ABSTRACT) :
1774                     (classMods & ~Modifier.ABSTRACT);
1775             }
1776             dout.writeInt(classMods);
1777 
1778             if (!cl.isArray()) {
1779                 /*
1780                  * compensate for change in 1.2FCS in which
1781                  * Class.getInterfaces() was modified to return Cloneable and
1782                  * Serializable for array classes.
1783                  */
1784                 Class<?>[] interfaces = cl.getInterfaces();
1785                 String[] ifaceNames = new String[interfaces.length];
1786                 for (int i = 0; i < interfaces.length; i++) {
1787                     ifaceNames[i] = interfaces[i].getName();
1788                 }
1789                 Arrays.sort(ifaceNames);
1790                 for (int i = 0; i < ifaceNames.length; i++) {
1791                     dout.writeUTF(ifaceNames[i]);
1792                 }
1793             }
1794 
1795             Field[] fields = cl.getDeclaredFields();
1796             MemberSignature[] fieldSigs = new MemberSignature[fields.length];
1797             for (int i = 0; i < fields.length; i++) {
1798                 fieldSigs[i] = new MemberSignature(fields[i]);
1799             }
1800             Arrays.sort(fieldSigs, new Comparator<>() {
1801                 public int compare(MemberSignature ms1, MemberSignature ms2) {
1802                     return ms1.name.compareTo(ms2.name);
1803                 }
1804             });
1805             for (int i = 0; i < fieldSigs.length; i++) {
1806                 MemberSignature sig = fieldSigs[i];
1807                 int mods = sig.member.getModifiers() &
1808                     (Modifier.PUBLIC | Modifier.PRIVATE | Modifier.PROTECTED |
1809                      Modifier.STATIC | Modifier.FINAL | Modifier.VOLATILE |
1810                      Modifier.TRANSIENT);
1811                 if (((mods & Modifier.PRIVATE) == 0) ||
1812                     ((mods & (Modifier.STATIC | Modifier.TRANSIENT)) == 0))
1813                 {
1814                     dout.writeUTF(sig.name);
1815                     dout.writeInt(mods);
1816                     dout.writeUTF(sig.signature);
1817                 }
1818             }
1819 
1820             if (hasStaticInitializer(cl)) {
1821                 dout.writeUTF("<clinit>");
1822                 dout.writeInt(Modifier.STATIC);
1823                 dout.writeUTF("()V");
1824             }
1825 
1826             Constructor<?>[] cons = cl.getDeclaredConstructors();
1827             MemberSignature[] consSigs = new MemberSignature[cons.length];
1828             for (int i = 0; i < cons.length; i++) {
1829                 consSigs[i] = new MemberSignature(cons[i]);
1830             }
1831             Arrays.sort(consSigs, new Comparator<>() {
1832                 public int compare(MemberSignature ms1, MemberSignature ms2) {
1833                     return ms1.signature.compareTo(ms2.signature);
1834                 }
1835             });
1836             for (int i = 0; i < consSigs.length; i++) {
1837                 MemberSignature sig = consSigs[i];
1838                 int mods = sig.member.getModifiers() &
1839                     (Modifier.PUBLIC | Modifier.PRIVATE | Modifier.PROTECTED |
1840                      Modifier.STATIC | Modifier.FINAL |
1841                      Modifier.SYNCHRONIZED | Modifier.NATIVE |
1842                      Modifier.ABSTRACT | Modifier.STRICT);
1843                 if ((mods & Modifier.PRIVATE) == 0) {
1844                     dout.writeUTF("<init>");
1845                     dout.writeInt(mods);
1846                     dout.writeUTF(sig.signature.replace('/', '.'));
1847                 }
1848             }
1849 
1850             MemberSignature[] methSigs = new MemberSignature[methods.length];
1851             for (int i = 0; i < methods.length; i++) {
1852                 methSigs[i] = new MemberSignature(methods[i]);
1853             }
1854             Arrays.sort(methSigs, new Comparator<>() {
1855                 public int compare(MemberSignature ms1, MemberSignature ms2) {
1856                     int comp = ms1.name.compareTo(ms2.name);
1857                     if (comp == 0) {
1858                         comp = ms1.signature.compareTo(ms2.signature);
1859                     }
1860                     return comp;
1861                 }
1862             });
1863             for (int i = 0; i < methSigs.length; i++) {
1864                 MemberSignature sig = methSigs[i];
1865                 int mods = sig.member.getModifiers() &
1866                     (Modifier.PUBLIC | Modifier.PRIVATE | Modifier.PROTECTED |
1867                      Modifier.STATIC | Modifier.FINAL |
1868                      Modifier.SYNCHRONIZED | Modifier.NATIVE |
1869                      Modifier.ABSTRACT | Modifier.STRICT);
1870                 if ((mods & Modifier.PRIVATE) == 0) {
1871                     dout.writeUTF(sig.name);
1872                     dout.writeInt(mods);
1873                     dout.writeUTF(sig.signature.replace('/', '.'));
1874                 }
1875             }
1876 
1877             dout.flush();
1878 
1879             MessageDigest md = MessageDigest.getInstance("SHA");
1880             byte[] hashBytes = md.digest(bout.toByteArray());
1881             long hash = 0;
1882             for (int i = Math.min(hashBytes.length, 8) - 1; i >= 0; i--) {
1883                 hash = (hash << 8) | (hashBytes[i] & 0xFF);
1884             }
1885             return hash;
1886         } catch (IOException ex) {
1887             throw new InternalError(ex);
1888         } catch (NoSuchAlgorithmException ex) {
1889             throw new SecurityException(ex.getMessage());
1890         }
1891     }
1892 
1893     /**
1894      * Returns true if the given class defines a static initializer method,
1895      * false otherwise.
1896      */
1897     private static native boolean hasStaticInitializer(Class<?> cl);
1898 
1899     /**
1900      * Class for computing and caching field/constructor/method signatures
1901      * during serialVersionUID calculation.
1902      */
1903     private static class MemberSignature {
1904 
1905         public final Member member;
1906         public final String name;
1907         public final String signature;
1908 
1909         public MemberSignature(Field field) {
1910             member = field;
1911             name = field.getName();
1912             signature = field.getType().descriptorString();
1913         }
1914 
1915         public MemberSignature(Constructor<?> cons) {
1916             member = cons;
1917             name = cons.getName();
1918             signature = getMethodSignature(
1919                 cons.getParameterTypes(), Void.TYPE);
1920         }
1921 
1922         public MemberSignature(Method meth) {
1923             member = meth;
1924             name = meth.getName();
1925             signature = getMethodSignature(
1926                 meth.getParameterTypes(), meth.getReturnType());
1927         }
1928     }
1929 
1930     /**
1931      * Class for setting and retrieving serializable field values in batch.
1932      */
1933     // REMIND: dynamically generate these?
1934     private static class FieldReflector {
1935 
1936         /** handle for performing unsafe operations */
1937         private static final Unsafe unsafe = Unsafe.getUnsafe();
1938 
1939         /** fields to operate on */
1940         private final ObjectStreamField[] fields;
1941         /** number of primitive fields */
1942         private final int numPrimFields;
1943         /** unsafe field keys for reading fields - may contain dupes */
1944         private final long[] readKeys;
1945         /** unsafe fields keys for writing fields - no dupes */
1946         private final long[] writeKeys;
1947         /** field data offsets */
1948         private final int[] offsets;
1949         /** field type codes */
1950         private final char[] typeCodes;
1951         /** field types */
1952         private final Class<?>[] types;
1953 
1954         /**
1955          * Return a new instance of the class using Unsafe.uninitializedDefaultValue
1956          * and buffer it.
1957          * @param clazz The value class
1958          * @return a buffered default value
1959          */
1960         static Object newValueInstance(Class<?> clazz) throws InstantiationException{
1961             assert clazz.isValue() : "Should be a value class";
1962             Object obj = unsafe.uninitializedDefaultValue(clazz);
1963             return unsafe.makePrivateBuffer(obj);
1964         }
1965 
1966         /**
1967          * Finish a value object, clear the larval state and returning the value object.
1968          * @param obj a buffered value object in a larval state
1969          * @return the finished value object
1970          */
1971         static Object finishValueInstance(Object obj) {
1972             assert (obj.getClass().isValue()) : "Should be a value class";
1973             return unsafe.finishPrivateBuffer(obj);
1974         }
1975 
1976         /**
1977          * Constructs FieldReflector capable of setting/getting values from the
1978          * subset of fields whose ObjectStreamFields contain non-null
1979          * reflective Field objects.  ObjectStreamFields with null Fields are
1980          * treated as filler, for which get operations return default values
1981          * and set operations discard given values.
1982          */
1983         FieldReflector(ObjectStreamField[] fields) {
1984             this.fields = fields;
1985             int nfields = fields.length;
1986             readKeys = new long[nfields];
1987             writeKeys = new long[nfields];
1988             offsets = new int[nfields];
1989             typeCodes = new char[nfields];
1990             ArrayList<Class<?>> typeList = new ArrayList<>();
1991             Set<Long> usedKeys = new HashSet<>();
1992 
1993 
1994             for (int i = 0; i < nfields; i++) {
1995                 ObjectStreamField f = fields[i];
1996                 Field rf = f.getField();
1997                 long key = (rf != null) ?
1998                     unsafe.objectFieldOffset(rf) : Unsafe.INVALID_FIELD_OFFSET;
1999                 readKeys[i] = key;
2000                 writeKeys[i] = usedKeys.add(key) ?
2001                     key : Unsafe.INVALID_FIELD_OFFSET;
2002                 offsets[i] = f.getOffset();
2003                 typeCodes[i] = f.getTypeCode();
2004                 if (!f.isPrimitive()) {
2005                     typeList.add((rf != null) ? rf.getType() : null);
2006                 }
2007             }
2008 
2009             types = typeList.toArray(new Class<?>[typeList.size()]);
2010             numPrimFields = nfields - types.length;
2011         }
2012 
2013         /**
2014          * Returns list of ObjectStreamFields representing fields operated on
2015          * by this reflector.  The shared/unshared values and Field objects
2016          * contained by ObjectStreamFields in the list reflect their bindings
2017          * to locally defined serializable fields.
2018          */
2019         ObjectStreamField[] getFields() {
2020             return fields;
2021         }
2022 
2023         /**
2024          * Fetches the serializable primitive field values of object obj and
2025          * marshals them into byte array buf starting at offset 0.  The caller
2026          * is responsible for ensuring that obj is of the proper type.
2027          */
2028         void getPrimFieldValues(Object obj, byte[] buf) {
2029             if (obj == null) {
2030                 throw new NullPointerException();
2031             }
2032             /* assuming checkDefaultSerialize() has been called on the class
2033              * descriptor this FieldReflector was obtained from, no field keys
2034              * in array should be equal to Unsafe.INVALID_FIELD_OFFSET.
2035              */
2036             for (int i = 0; i < numPrimFields; i++) {
2037                 long key = readKeys[i];
2038                 int off = offsets[i];
2039                 switch (typeCodes[i]) {
2040                     case 'Z' -> Bits.putBoolean(buf, off, unsafe.getBoolean(obj, key));
2041                     case 'B' -> buf[off] = unsafe.getByte(obj, key);
2042                     case 'C' -> Bits.putChar(buf, off, unsafe.getChar(obj, key));
2043                     case 'S' -> Bits.putShort(buf, off, unsafe.getShort(obj, key));
2044                     case 'I' -> Bits.putInt(buf, off, unsafe.getInt(obj, key));
2045                     case 'F' -> Bits.putFloat(buf, off, unsafe.getFloat(obj, key));
2046                     case 'J' -> Bits.putLong(buf, off, unsafe.getLong(obj, key));
2047                     case 'D' -> Bits.putDouble(buf, off, unsafe.getDouble(obj, key));
2048                     default  -> throw new InternalError();
2049                 }
2050             }
2051         }
2052 
2053         /**
2054          * Sets the serializable primitive fields of object obj using values
2055          * unmarshalled from byte array buf starting at offset 0.  The caller
2056          * is responsible for ensuring that obj is of the proper type.
2057          */
2058         void setPrimFieldValues(Object obj, byte[] buf) {
2059             if (obj == null) {
2060                 throw new NullPointerException();
2061             }
2062             for (int i = 0; i < numPrimFields; i++) {
2063                 long key = writeKeys[i];
2064                 if (key == Unsafe.INVALID_FIELD_OFFSET) {
2065                     continue;           // discard value
2066                 }
2067                 int off = offsets[i];
2068                 switch (typeCodes[i]) {
2069                     case 'Z' -> unsafe.putBoolean(obj, key, Bits.getBoolean(buf, off));
2070                     case 'B' -> unsafe.putByte(obj, key, buf[off]);
2071                     case 'C' -> unsafe.putChar(obj, key, Bits.getChar(buf, off));
2072                     case 'S' -> unsafe.putShort(obj, key, Bits.getShort(buf, off));
2073                     case 'I' -> unsafe.putInt(obj, key, Bits.getInt(buf, off));
2074                     case 'F' -> unsafe.putFloat(obj, key, Bits.getFloat(buf, off));
2075                     case 'J' -> unsafe.putLong(obj, key, Bits.getLong(buf, off));
2076                     case 'D' -> unsafe.putDouble(obj, key, Bits.getDouble(buf, off));
2077                     default  -> throw new InternalError();
2078                 }
2079             }
2080         }
2081 
2082         /**
2083          * Fetches the serializable object field values of object obj and
2084          * stores them in array vals starting at offset 0.  The caller is
2085          * responsible for ensuring that obj is of the proper type.
2086          */
2087         void getObjFieldValues(Object obj, Object[] vals) {
2088             if (obj == null) {
2089                 throw new NullPointerException();
2090             }
2091             /* assuming checkDefaultSerialize() has been called on the class
2092              * descriptor this FieldReflector was obtained from, no field keys
2093              * in array should be equal to Unsafe.INVALID_FIELD_OFFSET.
2094              */
2095             for (int i = numPrimFields; i < fields.length; i++) {
2096                 Field f = fields[i].getField();
2097                 vals[offsets[i]] = switch (typeCodes[i]) {
2098                     case 'L', '[' ->
2099                             unsafe.isFlattened(f)
2100                                     ? unsafe.getValue(obj, readKeys[i], f.getType())
2101                                     : unsafe.getReference(obj, readKeys[i]);
2102                     default       -> throw new InternalError();
2103                 };
2104             }
2105         }
2106 
2107         /**
2108          * Checks that the given values, from array vals starting at offset 0,
2109          * are assignable to the given serializable object fields.
2110          * @throws ClassCastException if any value is not assignable
2111          */
2112         void checkObjectFieldValueTypes(Object obj, Object[] vals) {
2113             setObjFieldValues(obj, vals, true);
2114         }
2115 
2116         /**
2117          * Sets the serializable object fields of object obj using values from
2118          * array vals starting at offset 0.  The caller is responsible for
2119          * ensuring that obj is of the proper type; however, attempts to set a
2120          * field with a value of the wrong type will trigger an appropriate
2121          * ClassCastException.
2122          */
2123         void setObjFieldValues(Object obj, Object[] vals) {
2124             setObjFieldValues(obj, vals, false);
2125         }
2126 
2127         private void setObjFieldValues(Object obj, Object[] vals, boolean dryRun) {
2128             if (obj == null) {
2129                 throw new NullPointerException();
2130             }
2131             for (int i = numPrimFields; i < fields.length; i++) {
2132                 long key = writeKeys[i];
2133                 if (key == Unsafe.INVALID_FIELD_OFFSET) {
2134                     continue;           // discard value
2135                 }
2136                 switch (typeCodes[i]) {
2137                     case 'L', '[' -> {
2138                         Field f = fields[i].getField();
2139                         Object val = vals[offsets[i]];
2140                         if (val != null &&
2141                             !types[i - numPrimFields].isInstance(val))
2142                         {
2143                             throw new ClassCastException(
2144                                 "cannot assign instance of " +
2145                                 val.getClass().getName() + " to field " +
2146                                 f.getDeclaringClass().getName() + "." +
2147                                 f.getName() + " of type " +
2148                                 f.getType().getName() + " in instance of " +
2149                                 obj.getClass().getName());
2150                         }
2151                         if (!dryRun) {
2152                             if (unsafe.isFlattened(f)) {
2153                                 unsafe.putValue(obj, key, f.getType(), val);
2154                             } else {
2155                                 unsafe.putReference(obj, key, val);
2156                             }
2157                         }
2158                     }
2159                     default -> throw new InternalError();
2160                 }
2161             }
2162         }
2163     }
2164 
2165     /**
2166      * Matches given set of serializable fields with serializable fields
2167      * described by the given local class descriptor, and returns a
2168      * FieldReflector instance capable of setting/getting values from the
2169      * subset of fields that match (non-matching fields are treated as filler,
2170      * for which get operations return default values and set operations
2171      * discard given values).  Throws InvalidClassException if unresolvable
2172      * type conflicts exist between the two sets of fields.
2173      */
2174     private static FieldReflector getReflector(ObjectStreamField[] fields,
2175                                                ObjectStreamClass localDesc)
2176         throws InvalidClassException
2177     {
2178         // class irrelevant if no fields
2179         Class<?> cl = (localDesc != null && fields.length > 0) ?
2180             localDesc.cl : Void.class;
2181 
2182         var clReflectors = Caches.reflectors.get(cl);
2183         var key = new FieldReflectorKey(fields);
2184         var reflector = clReflectors.get(key);
2185         if (reflector == null) {
2186             reflector = new FieldReflector(matchFields(fields, localDesc));
2187             var oldReflector = clReflectors.putIfAbsent(key, reflector);
2188             if (oldReflector != null) {
2189                 reflector = oldReflector;
2190             }
2191         }
2192         return reflector;
2193     }
2194 
2195     /**
2196      * FieldReflector cache lookup key.  Keys are considered equal if they
2197      * refer to equivalent field formats.
2198      */
2199     private static class FieldReflectorKey {
2200 
2201         private final String[] sigs;
2202         private final int hash;
2203 
2204         FieldReflectorKey(ObjectStreamField[] fields)
2205         {
2206             sigs = new String[2 * fields.length];
2207             for (int i = 0, j = 0; i < fields.length; i++) {
2208                 ObjectStreamField f = fields[i];
2209                 sigs[j++] = f.getName();
2210                 sigs[j++] = f.getSignature();
2211             }
2212             hash = Arrays.hashCode(sigs);
2213         }
2214 
2215         public int hashCode() {
2216             return hash;
2217         }
2218 
2219         public boolean equals(Object obj) {
2220             return obj == this ||
2221                    obj instanceof FieldReflectorKey other &&
2222                    Arrays.equals(sigs, other.sigs);
2223         }
2224     }
2225 
2226     /**
2227      * Matches given set of serializable fields with serializable fields
2228      * obtained from the given local class descriptor (which contain bindings
2229      * to reflective Field objects).  Returns list of ObjectStreamFields in
2230      * which each ObjectStreamField whose signature matches that of a local
2231      * field contains a Field object for that field; unmatched
2232      * ObjectStreamFields contain null Field objects.  Shared/unshared settings
2233      * of the returned ObjectStreamFields also reflect those of matched local
2234      * ObjectStreamFields.  Throws InvalidClassException if unresolvable type
2235      * conflicts exist between the two sets of fields.
2236      */
2237     private static ObjectStreamField[] matchFields(ObjectStreamField[] fields,
2238                                                    ObjectStreamClass localDesc)
2239         throws InvalidClassException
2240     {
2241         ObjectStreamField[] localFields = (localDesc != null) ?
2242             localDesc.fields : NO_FIELDS;
2243 
2244         /*
2245          * Even if fields == localFields, we cannot simply return localFields
2246          * here.  In previous implementations of serialization,
2247          * ObjectStreamField.getType() returned Object.class if the
2248          * ObjectStreamField represented a non-primitive field and belonged to
2249          * a non-local class descriptor.  To preserve this (questionable)
2250          * behavior, the ObjectStreamField instances returned by matchFields
2251          * cannot report non-primitive types other than Object.class; hence
2252          * localFields cannot be returned directly.
2253          */
2254 
2255         ObjectStreamField[] matches = new ObjectStreamField[fields.length];
2256         for (int i = 0; i < fields.length; i++) {
2257             ObjectStreamField f = fields[i], m = null;
2258             for (int j = 0; j < localFields.length; j++) {
2259                 ObjectStreamField lf = localFields[j];
2260                 if (f.getName().equals(lf.getName())) {
2261                     if ((f.isPrimitive() || lf.isPrimitive()) &&
2262                         f.getTypeCode() != lf.getTypeCode())
2263                     {
2264                         throw new InvalidClassException(localDesc.name,
2265                             "incompatible types for field " + f.getName());
2266                     }
2267                     if (lf.getField() != null) {
2268                         m = new ObjectStreamField(
2269                             lf.getField(), lf.isUnshared(), false);
2270                     } else {
2271                         m = new ObjectStreamField(
2272                             lf.getName(), lf.getSignature(), lf.isUnshared());
2273                     }
2274                 }
2275             }
2276             if (m == null) {
2277                 m = new ObjectStreamField(
2278                     f.getName(), f.getSignature(), false);
2279             }
2280             m.setOffset(f.getOffset());
2281             matches[i] = m;
2282         }
2283         return matches;
2284     }
2285 
2286     /**
2287      * A LRA cache of record deserialization constructors.
2288      */
2289     @SuppressWarnings("serial")
2290     private static final class DeserializationConstructorsCache
2291         extends ConcurrentHashMap<DeserializationConstructorsCache.Key, MethodHandle>  {
2292 
2293         // keep max. 10 cached entries - when the 11th element is inserted the oldest
2294         // is removed and 10 remains - 11 is the biggest map size where internal
2295         // table of 16 elements is sufficient (inserting 12th element would resize it to 32)
2296         private static final int MAX_SIZE = 10;
2297         private Key.Impl first, last; // first and last in FIFO queue
2298 
2299         DeserializationConstructorsCache() {
2300             // start small - if there is more than one shape of ObjectStreamClass
2301             // deserialized, there will typically be two (current version and previous version)
2302             super(2);
2303         }
2304 
2305         MethodHandle get(ObjectStreamField[] fields) {
2306             return get(new Key.Lookup(fields));
2307         }
2308 
2309         synchronized MethodHandle putIfAbsentAndGet(ObjectStreamField[] fields, MethodHandle mh) {
2310             Key.Impl key = new Key.Impl(fields);
2311             var oldMh = putIfAbsent(key, mh);
2312             if (oldMh != null) return oldMh;
2313             // else we did insert new entry -> link the new key as last
2314             if (last == null) {
2315                 last = first = key;
2316             } else {
2317                 last = (last.next = key);
2318             }
2319             // may need to remove first
2320             if (size() > MAX_SIZE) {
2321                 assert first != null;
2322                 remove(first);
2323                 first = first.next;
2324                 if (first == null) {
2325                     last = null;
2326                 }
2327             }
2328             return mh;
2329         }
2330 
2331         // a key composed of ObjectStreamField[] names and types
2332         abstract static class Key {
2333             abstract int length();
2334             abstract String fieldName(int i);
2335             abstract Class<?> fieldType(int i);
2336 
2337             @Override
2338             public final int hashCode() {
2339                 int n = length();
2340                 int h = 0;
2341                 for (int i = 0; i < n; i++) h = h * 31 + fieldType(i).hashCode();
2342                 for (int i = 0; i < n; i++) h = h * 31 + fieldName(i).hashCode();
2343                 return h;
2344             }
2345 
2346             @Override
2347             public final boolean equals(Object obj) {
2348                 if (!(obj instanceof Key other)) return false;
2349                 int n = length();
2350                 if (n != other.length()) return false;
2351                 for (int i = 0; i < n; i++) if (fieldType(i) != other.fieldType(i)) return false;
2352                 for (int i = 0; i < n; i++) if (!fieldName(i).equals(other.fieldName(i))) return false;
2353                 return true;
2354             }
2355 
2356             // lookup key - just wraps ObjectStreamField[]
2357             static final class Lookup extends Key {
2358                 final ObjectStreamField[] fields;
2359 
2360                 Lookup(ObjectStreamField[] fields) { this.fields = fields; }
2361 
2362                 @Override
2363                 int length() { return fields.length; }
2364 
2365                 @Override
2366                 String fieldName(int i) { return fields[i].getName(); }
2367 
2368                 @Override
2369                 Class<?> fieldType(int i) { return fields[i].getType(); }
2370             }
2371 
2372             // real key - copies field names and types and forms FIFO queue in cache
2373             static final class Impl extends Key {
2374                 Impl next;
2375                 final String[] fieldNames;
2376                 final Class<?>[] fieldTypes;
2377 
2378                 Impl(ObjectStreamField[] fields) {
2379                     this.fieldNames = new String[fields.length];
2380                     this.fieldTypes = new Class<?>[fields.length];
2381                     for (int i = 0; i < fields.length; i++) {
2382                         fieldNames[i] = fields[i].getName();
2383                         fieldTypes[i] = fields[i].getType();
2384                     }
2385                 }
2386 
2387                 @Override
2388                 int length() { return fieldNames.length; }
2389 
2390                 @Override
2391                 String fieldName(int i) { return fieldNames[i]; }
2392 
2393                 @Override
2394                 Class<?> fieldType(int i) { return fieldTypes[i]; }
2395             }
2396         }
2397     }
2398 
2399     /** Record specific support for retrieving and binding stream field values. */
2400     static final class RecordSupport {
2401         /**
2402          * Returns canonical record constructor adapted to take two arguments:
2403          * {@code (byte[] primValues, Object[] objValues)}
2404          * and return
2405          * {@code Object}
2406          */
2407         @SuppressWarnings("removal")
2408         static MethodHandle deserializationCtr(ObjectStreamClass desc) {
2409             // check the cached value 1st
2410             MethodHandle mh = desc.deserializationCtr;
2411             if (mh != null) return mh;
2412             mh = desc.deserializationCtrs.get(desc.getFields(false));
2413             if (mh != null) return desc.deserializationCtr = mh;
2414 
2415             // retrieve record components
2416             RecordComponent[] recordComponents;
2417             try {
2418                 Class<?> cls = desc.forClass();
2419                 PrivilegedExceptionAction<RecordComponent[]> pa = cls::getRecordComponents;
2420                 recordComponents = AccessController.doPrivileged(pa);
2421             } catch (PrivilegedActionException e) {
2422                 throw new InternalError(e.getCause());
2423             }
2424 
2425             // retrieve the canonical constructor
2426             // (T1, T2, ..., Tn):TR
2427             mh = desc.getRecordConstructor();
2428 
2429             // change return type to Object
2430             // (T1, T2, ..., Tn):TR -> (T1, T2, ..., Tn):Object
2431             mh = mh.asType(mh.type().changeReturnType(Object.class));
2432 
2433             // drop last 2 arguments representing primValues and objValues arrays
2434             // (T1, T2, ..., Tn):Object -> (T1, T2, ..., Tn, byte[], Object[]):Object
2435             mh = MethodHandles.dropArguments(mh, mh.type().parameterCount(), byte[].class, Object[].class);
2436 
2437             for (int i = recordComponents.length-1; i >= 0; i--) {
2438                 String name = recordComponents[i].getName();
2439                 Class<?> type = recordComponents[i].getType();
2440                 // obtain stream field extractor that extracts argument at
2441                 // position i (Ti+1) from primValues and objValues arrays
2442                 // (byte[], Object[]):Ti+1
2443                 MethodHandle combiner = streamFieldExtractor(name, type, desc);
2444                 // fold byte[] privValues and Object[] objValues into argument at position i (Ti+1)
2445                 // (..., Ti, Ti+1, byte[], Object[]):Object -> (..., Ti, byte[], Object[]):Object
2446                 mh = MethodHandles.foldArguments(mh, i, combiner);
2447             }
2448             // what we are left with is a MethodHandle taking just the primValues
2449             // and objValues arrays and returning the constructed record instance
2450             // (byte[], Object[]):Object
2451 
2452             // store it into cache and return the 1st value stored
2453             return desc.deserializationCtr =
2454                 desc.deserializationCtrs.putIfAbsentAndGet(desc.getFields(false), mh);
2455         }
2456 
2457         /** Returns the number of primitive fields for the given descriptor. */
2458         private static int numberPrimValues(ObjectStreamClass desc) {
2459             ObjectStreamField[] fields = desc.getFields();
2460             int primValueCount = 0;
2461             for (int i = 0; i < fields.length; i++) {
2462                 if (fields[i].isPrimitive())
2463                     primValueCount++;
2464                 else
2465                     break;  // can be no more
2466             }
2467             return primValueCount;
2468         }
2469 
2470         /**
2471          * Returns extractor MethodHandle taking the primValues and objValues arrays
2472          * and extracting the argument of canonical constructor with given name and type
2473          * or producing  default value for the given type if the field is absent.
2474          */
2475         private static MethodHandle streamFieldExtractor(String pName,
2476                                                          Class<?> pType,
2477                                                          ObjectStreamClass desc) {
2478             ObjectStreamField[] fields = desc.getFields(false);
2479 
2480             for (int i = 0; i < fields.length; i++) {
2481                 ObjectStreamField f = fields[i];
2482                 String fName = f.getName();
2483                 if (!fName.equals(pName))
2484                     continue;
2485 
2486                 Class<?> fType = f.getField().getType();
2487                 if (!pType.isAssignableFrom(fType))
2488                     throw new InternalError(fName + " unassignable, pType:" + pType + ", fType:" + fType);
2489 
2490                 if (f.isPrimitive()) {
2491                     // (byte[], int):fType
2492                     MethodHandle mh = PRIM_VALUE_EXTRACTORS.get(fType);
2493                     if (mh == null) {
2494                         throw new InternalError("Unexpected type: " + fType);
2495                     }
2496                     // bind offset
2497                     // (byte[], int):fType -> (byte[]):fType
2498                     mh = MethodHandles.insertArguments(mh, 1, f.getOffset());
2499                     // drop objValues argument
2500                     // (byte[]):fType -> (byte[], Object[]):fType
2501                     mh = MethodHandles.dropArguments(mh, 1, Object[].class);
2502                     // adapt return type to pType
2503                     // (byte[], Object[]):fType -> (byte[], Object[]):pType
2504                     if (pType != fType) {
2505                         mh = mh.asType(mh.type().changeReturnType(pType));
2506                     }
2507                     return mh;
2508                 } else { // reference
2509                     // (Object[], int):Object
2510                     MethodHandle mh = MethodHandles.arrayElementGetter(Object[].class);
2511                     // bind index
2512                     // (Object[], int):Object -> (Object[]):Object
2513                     mh = MethodHandles.insertArguments(mh, 1, i - numberPrimValues(desc));
2514                     // drop primValues argument
2515                     // (Object[]):Object -> (byte[], Object[]):Object
2516                     mh = MethodHandles.dropArguments(mh, 0, byte[].class);
2517                     // adapt return type to pType
2518                     // (byte[], Object[]):Object -> (byte[], Object[]):pType
2519                     if (pType != Object.class) {
2520                         mh = mh.asType(mh.type().changeReturnType(pType));
2521                     }
2522                     return mh;
2523                 }
2524             }
2525 
2526             // return default value extractor if no field matches pName
2527             return MethodHandles.empty(MethodType.methodType(pType, byte[].class, Object[].class));
2528         }
2529 
2530         private static final Map<Class<?>, MethodHandle> PRIM_VALUE_EXTRACTORS;
2531         static {
2532             var lkp = MethodHandles.lookup();
2533             try {
2534                 PRIM_VALUE_EXTRACTORS = Map.of(
2535                     byte.class, MethodHandles.arrayElementGetter(byte[].class),
2536                     short.class, lkp.findStatic(Bits.class, "getShort", MethodType.methodType(short.class, byte[].class, int.class)),
2537                     int.class, lkp.findStatic(Bits.class, "getInt", MethodType.methodType(int.class, byte[].class, int.class)),
2538                     long.class, lkp.findStatic(Bits.class, "getLong", MethodType.methodType(long.class, byte[].class, int.class)),
2539                     float.class, lkp.findStatic(Bits.class, "getFloat", MethodType.methodType(float.class, byte[].class, int.class)),
2540                     double.class, lkp.findStatic(Bits.class, "getDouble", MethodType.methodType(double.class, byte[].class, int.class)),
2541                     char.class, lkp.findStatic(Bits.class, "getChar", MethodType.methodType(char.class, byte[].class, int.class)),
2542                     boolean.class, lkp.findStatic(Bits.class, "getBoolean", MethodType.methodType(boolean.class, byte[].class, int.class))
2543                 );
2544             } catch (NoSuchMethodException | IllegalAccessException e) {
2545                 throw new InternalError("Can't lookup Bits.getXXX", e);
2546             }
2547         }
2548     }
2549 }