1 /*
   2  * Copyright (c) 2008, 2012, 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 sun.invoke.util;
  27 
  28 public enum Wrapper {
  29     //        wrapperType      simple     primitiveType  simple     char  emptyArray     format
  30     BOOLEAN(  Boolean.class,   "Boolean", boolean.class, "boolean", 'Z', new boolean[0], Format.unsigned( 1)),
  31     // These must be in the order defined for widening primitive conversions in JLS 5.1.2
  32     // Avoid boxing integral types here to defer initialization of internal caches
  33     BYTE   (     Byte.class,      "Byte",    byte.class,    "byte", 'B', new    byte[0], Format.signed(   8)),
  34     SHORT  (    Short.class,     "Short",   short.class,   "short", 'S', new   short[0], Format.signed(  16)),
  35     CHAR   (Character.class, "Character",    char.class,    "char", 'C', new    char[0], Format.unsigned(16)),
  36     INT    (  Integer.class,   "Integer",     int.class,     "int", 'I', new     int[0], Format.signed(  32)),
  37     LONG   (     Long.class,      "Long",    long.class,    "long", 'J', new    long[0], Format.signed(  64)),
  38     FLOAT  (    Float.class,     "Float",   float.class,   "float", 'F', new   float[0], Format.floating(32)),
  39     DOUBLE (   Double.class,    "Double",  double.class,  "double", 'D', new  double[0], Format.floating(64)),
  40     OBJECT (   Object.class,    "Object",  Object.class,  "Object", 'L', new  Object[0], Format.other(    1)),
  41     // VOID must be the last type, since it is "assignable" from any other type:
  42     VOID   (     Void.class,      "Void",    void.class,    "void", 'V',           null, Format.other(    0)),
  43     ;
  44 
  45     public static final int COUNT = 10;
  46 
  47     private final Class<?> wrapperType;
  48     private final Class<?> primitiveType;
  49     private final char     basicTypeChar;
  50     private final Object   emptyArray;
  51     private final int      format;
  52     private final String   wrapperSimpleName;
  53     private final String   primitiveSimpleName;
  54 
  55     private Wrapper(Class<?> wtype, String wtypeName, Class<?> ptype, String ptypeName, char tchar, Object emptyArray, int format) {
  56         this.wrapperType = wtype;
  57         this.primitiveType = ptype;
  58         this.basicTypeChar = tchar;
  59         this.emptyArray = emptyArray;
  60         this.format = format;
  61         this.wrapperSimpleName = wtypeName;
  62         this.primitiveSimpleName = ptypeName;
  63     }
  64 
  65     /** For debugging, give the details of this wrapper. */
  66     public String detailString() {
  67         return wrapperSimpleName+
  68                 java.util.Arrays.asList(wrapperType, primitiveType,
  69                 basicTypeChar, zero(),
  70                 "0x"+Integer.toHexString(format));
  71     }
  72 
  73     private abstract static class Format {
  74         static final int SLOT_SHIFT = 0, SIZE_SHIFT = 2, KIND_SHIFT = 12;
  75         static final int
  76                 SIGNED   = (-1) << KIND_SHIFT,
  77                 UNSIGNED = 0    << KIND_SHIFT,
  78                 FLOATING = 1    << KIND_SHIFT;
  79         static final int
  80                 SLOT_MASK = ((1<<(SIZE_SHIFT-SLOT_SHIFT))-1),
  81                 SIZE_MASK = ((1<<(KIND_SHIFT-SIZE_SHIFT))-1);
  82         static int format(int kind, int size, int slots) {
  83             assert(((kind >> KIND_SHIFT) << KIND_SHIFT) == kind);
  84             assert((size & (size-1)) == 0); // power of two
  85             assert((kind == SIGNED)   ? (size > 0) :
  86                    (kind == UNSIGNED) ? (size > 0) :
  87                    (kind == FLOATING) ? (size == 32 || size == 64)  :
  88                    false);
  89             assert((slots == 2) ? (size == 64) :
  90                    (slots == 1) ? (size <= 32) :
  91                    false);
  92             return kind | (size << SIZE_SHIFT) | (slots << SLOT_SHIFT);
  93         }
  94         static final int
  95                 INT      = SIGNED   | (32 << SIZE_SHIFT) | (1 << SLOT_SHIFT),
  96                 SHORT    = SIGNED   | (16 << SIZE_SHIFT) | (1 << SLOT_SHIFT),
  97                 BOOLEAN  = UNSIGNED | (1  << SIZE_SHIFT) | (1 << SLOT_SHIFT),
  98                 CHAR     = UNSIGNED | (16 << SIZE_SHIFT) | (1 << SLOT_SHIFT),
  99                 FLOAT    = FLOATING | (32 << SIZE_SHIFT) | (1 << SLOT_SHIFT),
 100                 VOID     = UNSIGNED | (0  << SIZE_SHIFT) | (0 << SLOT_SHIFT),
 101                 NUM_MASK = (-1) << SIZE_SHIFT;
 102         static int signed(int size)   { return format(SIGNED,   size, (size > 32 ? 2 : 1)); }
 103         static int unsigned(int size) { return format(UNSIGNED, size, (size > 32 ? 2 : 1)); }
 104         static int floating(int size) { return format(FLOATING, size, (size > 32 ? 2 : 1)); }
 105         static int other(int slots)   { return slots << SLOT_SHIFT; }
 106     }
 107 
 108     /// format queries:
 109 
 110     /** How many bits are in the wrapped value?  Returns 0 for OBJECT or VOID. */
 111     public int     bitWidth()      { return (format >> Format.SIZE_SHIFT) & Format.SIZE_MASK; }
 112     /** How many JVM stack slots occupied by the wrapped value?  Returns 0 for VOID. */
 113     public int     stackSlots()    { return (format >> Format.SLOT_SHIFT) & Format.SLOT_MASK; }
 114     /** Does the wrapped value occupy a single JVM stack slot? */
 115     public boolean isSingleWord()  { return (format & (1 << Format.SLOT_SHIFT)) != 0; }
 116     /** Does the wrapped value occupy two JVM stack slots? */
 117     public boolean isDoubleWord()  { return (format & (2 << Format.SLOT_SHIFT)) != 0; }
 118     /** Is the wrapped type numeric (not void or object)? */
 119     public boolean isNumeric()     { return (format & Format.NUM_MASK) != 0; }
 120     /** Is the wrapped type a primitive other than float, double, or void? */
 121     public boolean isIntegral()    { return isNumeric() && format < Format.FLOAT; }
 122     /** Is the wrapped type one of int, boolean, byte, char, or short? */
 123     public boolean isSubwordOrInt() { return isIntegral() && isSingleWord(); }
 124     /* Is the wrapped value a signed integral type (one of byte, short, int, or long)? */
 125     public boolean isSigned()      { return format < Format.VOID; }
 126     /* Is the wrapped value an unsigned integral type (one of boolean or char)? */
 127     public boolean isUnsigned()    { return format >= Format.BOOLEAN && format < Format.FLOAT; }
 128     /** Is the wrapped type either float or double? */
 129     public boolean isFloating()    { return format >= Format.FLOAT; }
 130     /** Is the wrapped type either void or a reference? */
 131     public boolean isOther()       { return (format & ~Format.SLOT_MASK) == 0; }
 132 
 133     /** Does the JLS 5.1.2 allow a variable of this wrapper's
 134      *  primitive type to be assigned from a value of the given wrapper's primitive type?
 135      *  Cases:
 136      *  <ul>
 137      *  <li>unboxing followed by widening primitive conversion
 138      *  <li>any type converted to {@code void} (i.e., dropping a method call's value)
 139      *  <li>boxing conversion followed by widening reference conversion to {@code Object}
 140      *  </ul>
 141      *  These are the cases allowed by MethodHandle.asType.
 142      */
 143     public boolean isConvertibleFrom(Wrapper source) {
 144         if (this == source)  return true;
 145         if (this.compareTo(source) < 0) {
 146             // At best, this is a narrowing conversion.
 147             return false;
 148         }
 149         // All conversions are allowed in the enum order between floats and signed ints.
 150         // First detect non-signed non-float types (boolean, char, Object, void).
 151         boolean floatOrSigned = (((this.format & source.format) & Format.SIGNED) != 0);
 152         if (!floatOrSigned) {
 153             if (this.isOther())  return true;
 154             // can convert char to int or wider, but nothing else
 155             if (source.format == Format.CHAR)  return true;
 156             // no other conversions are classified as widening
 157             return false;
 158         }
 159         // All signed and float conversions in the enum order are widening.
 160         assert(this.isFloating() || this.isSigned());
 161         assert(source.isFloating() || source.isSigned());
 162         return true;
 163     }
 164 
 165     static {
 166         assert(checkConvertibleFrom());
 167         assert(COUNT == Wrapper.values().length);
 168     }
 169     private static boolean checkConvertibleFrom() {
 170         // Check the matrix for correct classification of widening conversions.
 171         for (Wrapper w : values()) {
 172             assert(w.isConvertibleFrom(w));
 173             assert(VOID.isConvertibleFrom(w));
 174             if (w != VOID) {
 175                 assert(OBJECT.isConvertibleFrom(w));
 176                 assert(!w.isConvertibleFrom(VOID));
 177             }
 178             // check relations with unsigned integral types:
 179             if (w != CHAR) {
 180                 assert(!CHAR.isConvertibleFrom(w));
 181                 if (!w.isConvertibleFrom(INT))
 182                     assert(!w.isConvertibleFrom(CHAR));
 183             }
 184             if (w != BOOLEAN) {
 185                 assert(!BOOLEAN.isConvertibleFrom(w));
 186                 if (w != VOID && w != OBJECT)
 187                     assert(!w.isConvertibleFrom(BOOLEAN));
 188             }
 189             // check relations with signed integral types:
 190             if (w.isSigned()) {
 191                 for (Wrapper x : values()) {
 192                     if (w == x)  continue;
 193                     if (x.isFloating())
 194                         assert(!w.isConvertibleFrom(x));
 195                     else if (x.isSigned()) {
 196                         if (w.compareTo(x) < 0)
 197                             assert(!w.isConvertibleFrom(x));
 198                         else
 199                             assert(w.isConvertibleFrom(x));
 200                     }
 201                 }
 202             }
 203             // check relations with floating types:
 204             if (w.isFloating()) {
 205                 for (Wrapper x : values()) {
 206                     if (w == x)  continue;
 207                     if (x.isSigned())
 208                         assert(w.isConvertibleFrom(x));
 209                     else if (x.isFloating()) {
 210                         if (w.compareTo(x) < 0)
 211                             assert(!w.isConvertibleFrom(x));
 212                         else
 213                             assert(w.isConvertibleFrom(x));
 214                     }
 215                 }
 216             }
 217         }
 218         return true;  // i.e., assert(true)
 219     }
 220 
 221     /** Produce a zero value for the given wrapper type.
 222      *  This will be a numeric zero for a number or character,
 223      *  false for a boolean, and null for a reference or void.
 224      *  The common thread is that this is what is contained
 225      *  in a default-initialized variable of the given primitive
 226      *  type.  (For void, it is what a reflective method returns
 227      *  instead of no value at all.)
 228      */
 229     public Object zero() {
 230         switch (this) {
 231             case BOOLEAN:
 232                 return Boolean.FALSE;
 233             case INT:
 234                 return (Integer)0;
 235             case BYTE:
 236                 return (Byte)(byte)0;
 237             case CHAR:
 238                 return (Character)(char)0;
 239             case SHORT:
 240                 return (Short)(short)0;
 241             case LONG:
 242                 return (Long)(long)0;
 243             case FLOAT:
 244                 return FLOAT_ZERO;
 245             case DOUBLE:
 246                 return DOUBLE_ZERO;
 247             case VOID:
 248             case OBJECT:
 249             default:
 250                 return null;
 251         }
 252     }
 253 
 254     private static final Object DOUBLE_ZERO = (Double)(double)0;
 255     private static final Object FLOAT_ZERO = (Float)(float)0;
 256 
 257     /** Produce a zero value for the given wrapper type T.
 258      *  The optional argument must a type compatible with this wrapper.
 259      *  Equivalent to {@code this.cast(this.zero(), type)}.
 260      */
 261     public <T> T zero(Class<T> type) { return convert(zero(), type); }
 262 
 263     /** Return the wrapper that wraps values of the given type.
 264      *  The type may be {@code Object}, meaning the {@code OBJECT} wrapper.
 265      *  Otherwise, the type must be a primitive.
 266      *  @throws IllegalArgumentException for unexpected types
 267      */
 268     public static Wrapper forPrimitiveType(Class<?> type) {
 269         Wrapper w = findPrimitiveType(type);
 270         if (w != null)  return w;
 271         if (type.isPrimitive())
 272             throw new InternalError(); // redo hash function
 273         throw newIllegalArgumentException("not primitive: "+type);
 274     }
 275 
 276     /** Return the wrapper that corresponds to the provided basic type char.
 277      *  The basic type char must be for one of the eight primitive types, or void.
 278      *  @throws IllegalArgumentException for unexpected types
 279      */
 280     public static Wrapper forPrimitiveType(char basicTypeChar) {
 281         switch (basicTypeChar) {
 282             case 'I': return INT;
 283             case 'J': return LONG;
 284             case 'S': return SHORT;
 285             case 'B': return BYTE;
 286             case 'C': return CHAR;
 287             case 'F': return FLOAT;
 288             case 'D': return DOUBLE;
 289             case 'Z': return BOOLEAN;
 290             case 'V': return VOID;
 291             default: throw newIllegalArgumentException("not primitive: " + basicTypeChar);
 292         }
 293     }
 294 
 295     static Wrapper findPrimitiveType(Class<?> type) {
 296         Wrapper w = FROM_PRIM[hashPrim(type)];
 297         if (w != null && w.primitiveType == type) {
 298             return w;
 299         }
 300         return null;
 301     }
 302 
 303     /** Return the wrapper that wraps values into the given wrapper type.
 304      *  If it is {@code Object}, return {@code OBJECT}.
 305      *  Otherwise, it must be a wrapper type.
 306      *  The type must not be a primitive type.
 307      *  @throws IllegalArgumentException for unexpected types
 308      */
 309     public static Wrapper forWrapperType(Class<?> type) {
 310         Wrapper w = findWrapperType(type);
 311         if (w != null)  return w;
 312         for (Wrapper x : values())
 313             if (x.wrapperType == type)
 314                 throw new InternalError(); // redo hash function
 315         throw newIllegalArgumentException("not wrapper: "+type);
 316     }
 317 
 318     static Wrapper findWrapperType(Class<?> type) {
 319         Wrapper w = FROM_WRAP[hashWrap(type)];
 320         if (w != null && w.wrapperType == type) {
 321             return w;
 322         }
 323         return null;
 324     }
 325 
 326     /** Return the wrapper that corresponds to the given bytecode
 327      *  signature character.  Return {@code OBJECT} for the character 'L'.
 328      *  @throws IllegalArgumentException for any non-signature character or {@code '['}.
 329      */
 330     public static Wrapper forBasicType(char type) {
 331         Wrapper w = FROM_CHAR[hashChar(type)];
 332         if (w != null && w.basicTypeChar == type) {
 333             return w;
 334         }
 335         for (Wrapper x : values())
 336             if (w.basicTypeChar == type)
 337                 throw new InternalError(); // redo hash function
 338         throw newIllegalArgumentException("not basic type char: "+type);
 339     }
 340 
 341     /** Return the wrapper for the given type, if it is
 342      *  a primitive type, else return {@code OBJECT}.
 343      */
 344     public static Wrapper forBasicType(Class<?> type) {
 345         if (type.isPrimitive())
 346             return forPrimitiveType(type);
 347         return OBJECT;  // any reference, including wrappers or arrays
 348     }
 349 
 350     // Note on perfect hashes:
 351     //   for signature chars c, do (c + (c >> 1)) % 16
 352     //   for primitive type names n, do (n[0] + n[2]) % 16
 353     // The type name hash works for both primitive and wrapper names.
 354     // You can add "java/lang/Object" to the primitive names.
 355     // But you add the wrapper name Object, use (n[2] + (3*n[1])) % 16.
 356     private static final Wrapper[] FROM_PRIM = new Wrapper[16];
 357     private static final Wrapper[] FROM_WRAP = new Wrapper[16];
 358     private static final Wrapper[] FROM_CHAR = new Wrapper[16];
 359     private static int hashPrim(Class<?> x) {
 360         String xn = x.getName();
 361         if (xn.length() < 3)  return 0;
 362         return (xn.charAt(0) + xn.charAt(2)) % 16;
 363     }
 364     private static int hashWrap(Class<?> x) {
 365         String xn = x.getName();
 366         final int offset = 10; assert(offset == "java.lang.".length());
 367         if (xn.length() < offset+3)  return 0;
 368         return (3*xn.charAt(offset+1) + xn.charAt(offset+2)) % 16;
 369     }
 370     private static int hashChar(char x) {
 371         return (x + (x >> 1)) % 16;
 372     }
 373     static {
 374         for (Wrapper w : values()) {
 375             int pi = hashPrim(w.primitiveType);
 376             int wi = hashWrap(w.wrapperType);
 377             int ci = hashChar(w.basicTypeChar);
 378             assert(FROM_PRIM[pi] == null);
 379             assert(FROM_WRAP[wi] == null);
 380             assert(FROM_CHAR[ci] == null);
 381             FROM_PRIM[pi] = w;
 382             FROM_WRAP[wi] = w;
 383             FROM_CHAR[ci] = w;
 384         }
 385         //assert(jdk.sun.invoke.util.WrapperTest.test(false));
 386     }
 387 
 388     /** What is the primitive type wrapped by this wrapper? */
 389     public Class<?> primitiveType() { return primitiveType; }
 390 
 391     /** What is the wrapper type for this wrapper? */
 392     public Class<?> wrapperType() { return wrapperType; }
 393 
 394     /** What is the wrapper type for this wrapper?
 395      * Otherwise, the example type must be the wrapper type,
 396      * or the corresponding primitive type.
 397      * (For {@code OBJECT}, the example type can be any non-primitive,
 398      * and is normalized to {@code Object.class}.)
 399      * The resulting class type has the same type parameter.
 400      */
 401     public <T> Class<T> wrapperType(Class<T> exampleType) {
 402         if (exampleType == wrapperType) {
 403             return exampleType;
 404         } else if (exampleType == primitiveType ||
 405                    wrapperType == Object.class ||
 406                    exampleType.isInterface()) {
 407             return forceType(wrapperType, exampleType);
 408         }
 409         throw newClassCastException(exampleType, primitiveType);
 410     }
 411 
 412     private static ClassCastException newClassCastException(Class<?> actual, Class<?> expected) {
 413         return new ClassCastException(actual + " is not compatible with " + expected);
 414     }
 415 
 416     /** If {@code type} is a primitive type, return the corresponding
 417      *  wrapper type, else return {@code type} unchanged.
 418      */
 419     public static <T> Class<T> asWrapperType(Class<T> type) {
 420         if (type.isPrimitive()) {
 421             return forPrimitiveType(type).wrapperType(type);
 422         }
 423         return type;
 424     }
 425 
 426     /** If {@code type} is a wrapper type, return the corresponding
 427      *  primitive type, else return {@code type} unchanged.
 428      */
 429     public static <T> Class<T> asPrimitiveType(Class<T> type) {
 430         Wrapper w = findWrapperType(type);
 431         if (w != null) {
 432             return forceType(w.primitiveType(), type);
 433         }
 434         return type;
 435     }
 436 
 437     /** Query:  Is the given type a wrapper, such as {@code Integer} or {@code Void}? */
 438     public static boolean isWrapperType(Class<?> type) {
 439         return findWrapperType(type) != null;
 440     }
 441 
 442     /** Query:  Is the given type a primitive, such as {@code int} or {@code void}? */
 443     public static boolean isPrimitiveType(Class<?> type) {
 444         return type.isPrimitive();
 445     }
 446 
 447     /** What is the bytecode signature character for this type?
 448      *  All non-primitives, including array types, report as 'L', the signature character for references.
 449      */
 450     public static char basicTypeChar(Class<?> type) {
 451         if (!type.isPrimitive())
 452             return 'L';
 453         else
 454             return forPrimitiveType(type).basicTypeChar();
 455     }
 456 
 457     /** What is the bytecode signature character for this wrapper's
 458      *  primitive type?
 459      */
 460     public char basicTypeChar() { return basicTypeChar; }
 461 
 462     /** What is the simple name of the wrapper type?
 463      */
 464     public String wrapperSimpleName() { return wrapperSimpleName; }
 465 
 466     /** What is the simple name of the primitive type?
 467      */
 468     public String primitiveSimpleName() { return primitiveSimpleName; }
 469 
 470 //    /** Wrap a value in the given type, which may be either a primitive or wrapper type.
 471 //     *  Performs standard primitive conversions, including truncation and float conversions.
 472 //     */
 473 //    public static <T> T wrap(Object x, Class<T> type) {
 474 //        return Wrapper.valueOf(type).cast(x, type);
 475 //    }
 476 
 477     /** Cast a wrapped value to the given type, which may be either a primitive or wrapper type.
 478      *  The given target type must be this wrapper's primitive or wrapper type.
 479      *  If this wrapper is OBJECT, the target type may also be an interface, perform no runtime check.
 480      *  Performs standard primitive conversions, including truncation and float conversions.
 481      *  The given type must be compatible with this wrapper.  That is, it must either
 482      *  be the wrapper type (or a subtype, in the case of {@code OBJECT}) or else
 483      *  it must be the wrapper's primitive type.
 484      *  Primitive conversions are only performed if the given type is itself a primitive.
 485      *  @throws ClassCastException if the given type is not compatible with this wrapper
 486      */
 487     public <T> T cast(Object x, Class<T> type) {
 488         return convert(x, type, true);
 489     }
 490 
 491     /** Convert a wrapped value to the given type.
 492      *  The given target type must be this wrapper's primitive or wrapper type.
 493      *  This is equivalent to {@link #cast}, except that it refuses to perform
 494      *  narrowing primitive conversions.
 495      */
 496     public <T> T convert(Object x, Class<T> type) {
 497         return convert(x, type, false);
 498     }
 499 
 500     private <T> T convert(Object x, Class<T> type, boolean isCast) {
 501         if (this == OBJECT) {
 502             // If the target wrapper is OBJECT, just do a reference cast.
 503             // If the target type is an interface, perform no runtime check.
 504             // (This loophole is safe, and is allowed by the JVM verifier.)
 505             // If the target type is a primitive, change it to a wrapper.
 506             assert(!type.isPrimitive());
 507             if (!type.isInterface())
 508                 type.cast(x);
 509             @SuppressWarnings("unchecked")
 510             T result = (T) x;  // unchecked warning is expected here
 511             return result;
 512         }
 513         Class<T> wtype = wrapperType(type);
 514         if (wtype.isInstance(x)) {
 515             return wtype.cast(x);
 516         }
 517         if (!isCast) {
 518             Class<?> sourceType = x.getClass();  // throw NPE if x is null
 519             Wrapper source = findWrapperType(sourceType);
 520             if (source == null || !this.isConvertibleFrom(source)) {
 521                 throw newClassCastException(wtype, sourceType);
 522             }
 523         } else if (x == null) {
 524             @SuppressWarnings("unchecked")
 525             T z = (T) zero();
 526             return z;
 527         }
 528         @SuppressWarnings("unchecked")
 529         T result = (T) wrap(x);  // unchecked warning is expected here
 530         assert (result == null ? Void.class : result.getClass()) == wtype;
 531         return result;
 532     }
 533 
 534     /** Cast a reference type to another reference type.
 535      * If the target type is an interface, perform no runtime check.
 536      * (This loophole is safe, and is allowed by the JVM verifier.)
 537      * If the target type is a primitive, change it to a wrapper.
 538      */
 539     static <T> Class<T> forceType(Class<?> type, Class<T> exampleType) {
 540         assert(type == exampleType ||
 541                type.isPrimitive() && forPrimitiveType(type) == findWrapperType(exampleType) ||
 542                exampleType.isPrimitive() && forPrimitiveType(exampleType) == findWrapperType(type) ||
 543                type == Object.class && !exampleType.isPrimitive());
 544         @SuppressWarnings("unchecked")
 545         Class<T> result = (Class<T>) type;  // unchecked warning is expected here
 546         return result;
 547     }
 548 
 549     /** Wrap a value in this wrapper's type.
 550      * Performs standard primitive conversions, including truncation and float conversions.
 551      * Performs returns the unchanged reference for {@code OBJECT}.
 552      * Returns null for {@code VOID}.
 553      * Returns a zero value for a null input.
 554      * @throws ClassCastException if this wrapper is numeric and the operand
 555      *                            is not a number, character, boolean, or null
 556      */
 557     public Object wrap(Object x) {
 558         // do non-numeric wrappers first
 559         switch (basicTypeChar) {
 560             case 'L': return x;
 561             case 'V': return null;
 562         }
 563         Number xn = numberValue(x);
 564         switch (basicTypeChar) {
 565             case 'I': return Integer.valueOf(xn.intValue());
 566             case 'J': return Long.valueOf(xn.longValue());
 567             case 'F': return Float.valueOf(xn.floatValue());
 568             case 'D': return Double.valueOf(xn.doubleValue());
 569             case 'S': return Short.valueOf((short) xn.intValue());
 570             case 'B': return Byte.valueOf((byte) xn.intValue());
 571             case 'C': return Character.valueOf((char) xn.intValue());
 572             case 'Z': return Boolean.valueOf(boolValue(xn.byteValue()));
 573         }
 574         throw new InternalError("bad wrapper");
 575     }
 576 
 577     /** Wrap a value (an int or smaller value) in this wrapper's type.
 578      * Performs standard primitive conversions, including truncation and float conversions.
 579      * Produces an {@code Integer} for {@code OBJECT}, although the exact type
 580      * of the operand is not known.
 581      * Returns null for {@code VOID}.
 582      */
 583     public Object wrap(int x) {
 584         if (basicTypeChar == 'L')  return (Integer)x;
 585         switch (basicTypeChar) {
 586             case 'L': throw newIllegalArgumentException("cannot wrap to object type");
 587             case 'V': return null;
 588             case 'I': return Integer.valueOf(x);
 589             case 'J': return Long.valueOf(x);
 590             case 'F': return Float.valueOf(x);
 591             case 'D': return Double.valueOf(x);
 592             case 'S': return Short.valueOf((short) x);
 593             case 'B': return Byte.valueOf((byte) x);
 594             case 'C': return Character.valueOf((char) x);
 595             case 'Z': return Boolean.valueOf(boolValue((byte) x));
 596         }
 597         throw new InternalError("bad wrapper");
 598     }
 599 
 600     private static Number numberValue(Object x) {
 601         if (x instanceof Number)     return (Number)x;
 602         if (x instanceof Character)  return (int)(Character)x;
 603         if (x instanceof Boolean)    return (Boolean)x ? 1 : 0;
 604         // Remaining allowed case of void:  Must be a null reference.
 605         return (Number)x;
 606     }
 607 
 608     // Parameter type of boolValue must be byte, because
 609     // MethodHandles.explicitCastArguments defines boolean
 610     // conversion as first converting to byte.
 611     private static boolean boolValue(byte bits) {
 612         bits &= 1;  // simple 31-bit zero extension
 613         return (bits != 0);
 614     }
 615 
 616     private static RuntimeException newIllegalArgumentException(String message, Object x) {
 617         return newIllegalArgumentException(message + x);
 618     }
 619     private static RuntimeException newIllegalArgumentException(String message) {
 620         return new IllegalArgumentException(message);
 621     }
 622 
 623     // primitive array support
 624     public Object makeArray(int len) {
 625         return java.lang.reflect.Array.newInstance(primitiveType, len);
 626     }
 627     public Class<?> arrayType() {
 628         return emptyArray.getClass();
 629     }
 630     public void copyArrayUnboxing(Object[] values, int vpos, Object a, int apos, int length) {
 631         if (a.getClass() != arrayType())
 632             arrayType().cast(a);  // throw NPE or CCE if bad type
 633         for (int i = 0; i < length; i++) {
 634             Object value = values[i+vpos];
 635             value = convert(value, primitiveType);
 636             java.lang.reflect.Array.set(a, i+apos, value);
 637         }
 638     }
 639     public void copyArrayBoxing(Object a, int apos, Object[] values, int vpos, int length) {
 640         if (a.getClass() != arrayType())
 641             arrayType().cast(a);  // throw NPE or CCE if bad type
 642         for (int i = 0; i < length; i++) {
 643             Object value = java.lang.reflect.Array.get(a, i+apos);
 644             //Already done: value = convert(value, primitiveType);
 645             assert(value.getClass() == wrapperType);
 646             values[i+vpos] = value;
 647         }
 648     }
 649 }