1 /* 2 * Copyright (c) 2008, 2013, 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.lang.invoke; 27 28 import sun.invoke.util.Wrapper; 29 import java.lang.ref.WeakReference; 30 import java.lang.ref.Reference; 31 import java.lang.ref.ReferenceQueue; 32 import java.util.Arrays; 33 import java.util.Collections; 34 import java.util.List; 35 import java.util.Objects; 36 import java.util.concurrent.ConcurrentMap; 37 import java.util.concurrent.ConcurrentHashMap; 38 import sun.invoke.util.BytecodeDescriptor; 39 import static java.lang.invoke.MethodHandleStatics.*; 40 41 /** 42 * A method type represents the arguments and return type accepted and 43 * returned by a method handle, or the arguments and return type passed 44 * and expected by a method handle caller. Method types must be properly 45 * matched between a method handle and all its callers, 46 * and the JVM's operations enforce this matching at, specifically 47 * during calls to {@link MethodHandle#invokeExact MethodHandle.invokeExact} 48 * and {@link MethodHandle#invoke MethodHandle.invoke}, and during execution 49 * of {@code invokedynamic} instructions. 50 * <p> 51 * The structure is a return type accompanied by any number of parameter types. 52 * The types (primitive, {@code void}, and reference) are represented by {@link Class} objects. 53 * (For ease of exposition, we treat {@code void} as if it were a type. 54 * In fact, it denotes the absence of a return type.) 55 * <p> 56 * All instances of {@code MethodType} are immutable. 57 * Two instances are completely interchangeable if they compare equal. 58 * Equality depends on pairwise correspondence of the return and parameter types and on nothing else. 59 * <p> 60 * This type can be created only by factory methods. 61 * All factory methods may cache values, though caching is not guaranteed. 62 * Some factory methods are static, while others are virtual methods which 63 * modify precursor method types, e.g., by changing a selected parameter. 64 * <p> 65 * Factory methods which operate on groups of parameter types 66 * are systematically presented in two versions, so that both Java arrays and 67 * Java lists can be used to work with groups of parameter types. 68 * The query methods {@code parameterArray} and {@code parameterList} 69 * also provide a choice between arrays and lists. 70 * <p> 71 * {@code MethodType} objects are sometimes derived from bytecode instructions 72 * such as {@code invokedynamic}, specifically from the type descriptor strings associated 73 * with the instructions in a class file's constant pool. 74 * <p> 75 * Like classes and strings, method types can also be represented directly 76 * in a class file's constant pool as constants. 77 * A method type may be loaded by an {@code ldc} instruction which refers 78 * to a suitable {@code CONSTANT_MethodType} constant pool entry. 79 * The entry refers to a {@code CONSTANT_Utf8} spelling for the descriptor string. 80 * (For full details on method type constants, 81 * see sections 4.4.8 and 5.4.3.5 of the Java Virtual Machine Specification.) 82 * <p> 83 * When the JVM materializes a {@code MethodType} from a descriptor string, 84 * all classes named in the descriptor must be accessible, and will be loaded. 85 * (But the classes need not be initialized, as is the case with a {@code CONSTANT_Class}.) 86 * This loading may occur at any time before the {@code MethodType} object is first derived. 87 * @author John Rose, JSR 292 EG 88 */ 89 public final 90 class MethodType implements java.io.Serializable { 91 private static final long serialVersionUID = 292L; // {rtype, {ptype...}} 92 93 // The rtype and ptypes fields define the structural identity of the method type: 94 private final Class<?> rtype; 95 private final Class<?>[] ptypes; 96 97 // The remaining fields are caches of various sorts: 98 private @Stable MethodTypeForm form; // erased form, plus cached data about primitives 99 private @Stable MethodType wrapAlt; // alternative wrapped/unwrapped version 100 // Android-changed: Remove adapter cache. We're not dynamically generating any 101 // adapters at this point. 102 // private @Stable Invokers invokers; // cache of handy higher-order adapters 103 private @Stable String methodDescriptor; // cache for toMethodDescriptorString 104 105 /** 106 * Check the given parameters for validity and store them into the final fields. 107 */ 108 private MethodType(Class<?> rtype, Class<?>[] ptypes, boolean trusted) { 109 checkRtype(rtype); 110 checkPtypes(ptypes); 111 this.rtype = rtype; 112 // defensively copy the array passed in by the user 113 this.ptypes = trusted ? ptypes : Arrays.copyOf(ptypes, ptypes.length); 114 } 115 116 /** 117 * Construct a temporary unchecked instance of MethodType for use only as a key to the intern table. 118 * Does not check the given parameters for validity, and must be discarded after it is used as a searching key. 119 * The parameters are reversed for this constructor, so that is is not accidentally used. 120 */ 121 private MethodType(Class<?>[] ptypes, Class<?> rtype) { 122 this.rtype = rtype; 123 this.ptypes = ptypes; 124 } 125 126 /*trusted*/ MethodTypeForm form() { return form; } 127 /*trusted*/ /** @hide */ public Class<?> rtype() { return rtype; } 128 /*trusted*/ /** @hide */ public Class<?>[] ptypes() { return ptypes; } 129 130 // Android-changed: Removed method setForm. It's unused in the JDK and there's no 131 // good reason to allow the form to be set externally. 132 // 133 // void setForm(MethodTypeForm f) { form = f; } 134 135 /** This number, mandated by the JVM spec as 255, 136 * is the maximum number of <em>slots</em> 137 * that any Java method can receive in its argument list. 138 * It limits both JVM signatures and method type objects. 139 * The longest possible invocation will look like 140 * {@code staticMethod(arg1, arg2, ..., arg255)} or 141 * {@code x.virtualMethod(arg1, arg2, ..., arg254)}. 142 */ 143 /*non-public*/ static final int MAX_JVM_ARITY = 255; // this is mandated by the JVM spec. 144 145 /** This number is the maximum arity of a method handle, 254. 146 * It is derived from the absolute JVM-imposed arity by subtracting one, 147 * which is the slot occupied by the method handle itself at the 148 * beginning of the argument list used to invoke the method handle. 149 * The longest possible invocation will look like 150 * {@code mh.invoke(arg1, arg2, ..., arg254)}. 151 */ 152 // Issue: Should we allow MH.invokeWithArguments to go to the full 255? 153 /*non-public*/ static final int MAX_MH_ARITY = MAX_JVM_ARITY-1; // deduct one for mh receiver 154 155 /** This number is the maximum arity of a method handle invoker, 253. 156 * It is derived from the absolute JVM-imposed arity by subtracting two, 157 * which are the slots occupied by invoke method handle, and the 158 * target method handle, which are both at the beginning of the argument 159 * list used to invoke the target method handle. 160 * The longest possible invocation will look like 161 * {@code invokermh.invoke(targetmh, arg1, arg2, ..., arg253)}. 162 */ 163 /*non-public*/ static final int MAX_MH_INVOKER_ARITY = MAX_MH_ARITY-1; // deduct one more for invoker 164 165 private static void checkRtype(Class<?> rtype) { 166 Objects.requireNonNull(rtype); 167 } 168 private static void checkPtype(Class<?> ptype) { 169 Objects.requireNonNull(ptype); 170 if (ptype == void.class) 171 throw newIllegalArgumentException("parameter type cannot be void"); 172 } 173 /** Return number of extra slots (count of long/double args). */ 174 private static int checkPtypes(Class<?>[] ptypes) { 175 int slots = 0; 176 for (Class<?> ptype : ptypes) { 177 checkPtype(ptype); 178 if (ptype == double.class || ptype == long.class) { 179 slots++; 180 } 181 } 182 checkSlotCount(ptypes.length + slots); 183 return slots; 184 } 185 static void checkSlotCount(int count) { 186 assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0); 187 // MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work: 188 if ((count & MAX_JVM_ARITY) != count) 189 throw newIllegalArgumentException("bad parameter count "+count); 190 } 191 private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) { 192 if (num instanceof Integer) num = "bad index: "+num; 193 return new IndexOutOfBoundsException(num.toString()); 194 } 195 196 static final ConcurrentWeakInternSet<MethodType> internTable = new ConcurrentWeakInternSet<>(); 197 198 static final Class<?>[] NO_PTYPES = {}; 199 200 /** 201 * Finds or creates an instance of the given method type. 202 * @param rtype the return type 203 * @param ptypes the parameter types 204 * @return a method type with the given components 205 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null 206 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class} 207 */ 208 public static 209 MethodType methodType(Class<?> rtype, Class<?>[] ptypes) { 210 return makeImpl(rtype, ptypes, false); 211 } 212 213 /** 214 * Finds or creates a method type with the given components. 215 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 216 * @param rtype the return type 217 * @param ptypes the parameter types 218 * @return a method type with the given components 219 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null 220 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class} 221 */ 222 public static 223 MethodType methodType(Class<?> rtype, List<Class<?>> ptypes) { 224 boolean notrust = false; // random List impl. could return evil ptypes array 225 return makeImpl(rtype, listToArray(ptypes), notrust); 226 } 227 228 private static Class<?>[] listToArray(List<Class<?>> ptypes) { 229 // sanity check the size before the toArray call, since size might be huge 230 checkSlotCount(ptypes.size()); 231 return ptypes.toArray(NO_PTYPES); 232 } 233 234 /** 235 * Finds or creates a method type with the given components. 236 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 237 * The leading parameter type is prepended to the remaining array. 238 * @param rtype the return type 239 * @param ptype0 the first parameter type 240 * @param ptypes the remaining parameter types 241 * @return a method type with the given components 242 * @throws NullPointerException if {@code rtype} or {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is null 243 * @throws IllegalArgumentException if {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is {@code void.class} 244 */ 245 public static 246 MethodType methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes) { 247 Class<?>[] ptypes1 = new Class<?>[1+ptypes.length]; 248 ptypes1[0] = ptype0; 249 System.arraycopy(ptypes, 0, ptypes1, 1, ptypes.length); 250 return makeImpl(rtype, ptypes1, true); 251 } 252 253 /** 254 * Finds or creates a method type with the given components. 255 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 256 * The resulting method has no parameter types. 257 * @param rtype the return type 258 * @return a method type with the given return value 259 * @throws NullPointerException if {@code rtype} is null 260 */ 261 public static 262 MethodType methodType(Class<?> rtype) { 263 return makeImpl(rtype, NO_PTYPES, true); 264 } 265 266 /** 267 * Finds or creates a method type with the given components. 268 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 269 * The resulting method has the single given parameter type. 270 * @param rtype the return type 271 * @param ptype0 the parameter type 272 * @return a method type with the given return value and parameter type 273 * @throws NullPointerException if {@code rtype} or {@code ptype0} is null 274 * @throws IllegalArgumentException if {@code ptype0} is {@code void.class} 275 */ 276 public static 277 MethodType methodType(Class<?> rtype, Class<?> ptype0) { 278 return makeImpl(rtype, new Class<?>[]{ ptype0 }, true); 279 } 280 281 /** 282 * Finds or creates a method type with the given components. 283 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 284 * The resulting method has the same parameter types as {@code ptypes}, 285 * and the specified return type. 286 * @param rtype the return type 287 * @param ptypes the method type which supplies the parameter types 288 * @return a method type with the given components 289 * @throws NullPointerException if {@code rtype} or {@code ptypes} is null 290 */ 291 public static 292 MethodType methodType(Class<?> rtype, MethodType ptypes) { 293 return makeImpl(rtype, ptypes.ptypes, true); 294 } 295 296 /** 297 * Sole factory method to find or create an interned method type. 298 * @param rtype desired return type 299 * @param ptypes desired parameter types 300 * @param trusted whether the ptypes can be used without cloning 301 * @return the unique method type of the desired structure 302 */ 303 /*trusted*/ static 304 MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) { 305 MethodType mt = internTable.get(new MethodType(ptypes, rtype)); 306 if (mt != null) 307 return mt; 308 if (ptypes.length == 0) { 309 ptypes = NO_PTYPES; trusted = true; 310 } 311 mt = new MethodType(rtype, ptypes, trusted); 312 // promote the object to the Real Thing, and reprobe 313 mt.form = MethodTypeForm.findForm(mt); 314 return internTable.add(mt); 315 } 316 private static final MethodType[] objectOnlyTypes = new MethodType[20]; 317 318 /** 319 * Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array. 320 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 321 * All parameters and the return type will be {@code Object}, 322 * except the final array parameter if any, which will be {@code Object[]}. 323 * @param objectArgCount number of parameters (excluding the final array parameter if any) 324 * @param finalArray whether there will be a trailing array parameter, of type {@code Object[]} 325 * @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments 326 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true) 327 * @see #genericMethodType(int) 328 */ 329 public static 330 MethodType genericMethodType(int objectArgCount, boolean finalArray) { 331 MethodType mt; 332 checkSlotCount(objectArgCount); 333 int ivarargs = (!finalArray ? 0 : 1); 334 int ootIndex = objectArgCount*2 + ivarargs; 335 if (ootIndex < objectOnlyTypes.length) { 336 mt = objectOnlyTypes[ootIndex]; 337 if (mt != null) return mt; 338 } 339 Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs]; 340 Arrays.fill(ptypes, Object.class); 341 if (ivarargs != 0) ptypes[objectArgCount] = Object[].class; 342 mt = makeImpl(Object.class, ptypes, true); 343 if (ootIndex < objectOnlyTypes.length) { 344 objectOnlyTypes[ootIndex] = mt; // cache it here also! 345 } 346 return mt; 347 } 348 349 /** 350 * Finds or creates a method type whose components are all {@code Object}. 351 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 352 * All parameters and the return type will be Object. 353 * @param objectArgCount number of parameters 354 * @return a generally applicable method type, for all calls of the given argument count 355 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 356 * @see #genericMethodType(int, boolean) 357 */ 358 public static 359 MethodType genericMethodType(int objectArgCount) { 360 return genericMethodType(objectArgCount, false); 361 } 362 363 /** 364 * Finds or creates a method type with a single different parameter type. 365 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 366 * @param num the index (zero-based) of the parameter type to change 367 * @param nptype a new parameter type to replace the old one with 368 * @return the same type, except with the selected parameter changed 369 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()} 370 * @throws IllegalArgumentException if {@code nptype} is {@code void.class} 371 * @throws NullPointerException if {@code nptype} is null 372 */ 373 public MethodType changeParameterType(int num, Class<?> nptype) { 374 if (parameterType(num) == nptype) return this; 375 checkPtype(nptype); 376 Class<?>[] nptypes = ptypes.clone(); 377 nptypes[num] = nptype; 378 return makeImpl(rtype, nptypes, true); 379 } 380 381 /** 382 * Finds or creates a method type with additional parameter types. 383 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 384 * @param num the position (zero-based) of the inserted parameter type(s) 385 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list 386 * @return the same type, except with the selected parameter(s) inserted 387 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()} 388 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} 389 * or if the resulting method type would have more than 255 parameter slots 390 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null 391 */ 392 public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) { 393 int len = ptypes.length; 394 if (num < 0 || num > len) 395 throw newIndexOutOfBoundsException(num); 396 int ins = checkPtypes(ptypesToInsert); 397 checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins); 398 int ilen = ptypesToInsert.length; 399 if (ilen == 0) return this; 400 Class<?>[] nptypes = Arrays.copyOfRange(ptypes, 0, len+ilen); 401 System.arraycopy(nptypes, num, nptypes, num+ilen, len-num); 402 System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen); 403 return makeImpl(rtype, nptypes, true); 404 } 405 406 /** 407 * Finds or creates a method type with additional parameter types. 408 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 409 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list 410 * @return the same type, except with the selected parameter(s) appended 411 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} 412 * or if the resulting method type would have more than 255 parameter slots 413 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null 414 */ 415 public MethodType appendParameterTypes(Class<?>... ptypesToInsert) { 416 return insertParameterTypes(parameterCount(), ptypesToInsert); 417 } 418 419 /** 420 * Finds or creates a method type with additional parameter types. 421 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 422 * @param num the position (zero-based) of the inserted parameter type(s) 423 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list 424 * @return the same type, except with the selected parameter(s) inserted 425 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()} 426 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} 427 * or if the resulting method type would have more than 255 parameter slots 428 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null 429 */ 430 public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) { 431 return insertParameterTypes(num, listToArray(ptypesToInsert)); 432 } 433 434 /** 435 * Finds or creates a method type with additional parameter types. 436 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 437 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list 438 * @return the same type, except with the selected parameter(s) appended 439 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} 440 * or if the resulting method type would have more than 255 parameter slots 441 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null 442 */ 443 public MethodType appendParameterTypes(List<Class<?>> ptypesToInsert) { 444 return insertParameterTypes(parameterCount(), ptypesToInsert); 445 } 446 447 /** 448 * Finds or creates a method type with modified parameter types. 449 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 450 * @param start the position (zero-based) of the first replaced parameter type(s) 451 * @param end the position (zero-based) after the last replaced parameter type(s) 452 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list 453 * @return the same type, except with the selected parameter(s) replaced 454 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()} 455 * or if {@code end} is negative or greater than {@code parameterCount()} 456 * or if {@code start} is greater than {@code end} 457 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} 458 * or if the resulting method type would have more than 255 parameter slots 459 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null 460 */ 461 /*non-public*/ MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) { 462 if (start == end) 463 return insertParameterTypes(start, ptypesToInsert); 464 int len = ptypes.length; 465 if (!(0 <= start && start <= end && end <= len)) 466 throw newIndexOutOfBoundsException("start="+start+" end="+end); 467 int ilen = ptypesToInsert.length; 468 if (ilen == 0) 469 return dropParameterTypes(start, end); 470 return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert); 471 } 472 473 /** Replace the last arrayLength parameter types with the component type of arrayType. 474 * @param arrayType any array type 475 * @param arrayLength the number of parameter types to change 476 * @return the resulting type 477 */ 478 /*non-public*/ MethodType asSpreaderType(Class<?> arrayType, int arrayLength) { 479 assert(parameterCount() >= arrayLength); 480 int spreadPos = ptypes.length - arrayLength; 481 if (arrayLength == 0) return this; // nothing to change 482 if (arrayType == Object[].class) { 483 if (isGeneric()) return this; // nothing to change 484 if (spreadPos == 0) { 485 // no leading arguments to preserve; go generic 486 MethodType res = genericMethodType(arrayLength); 487 if (rtype != Object.class) { 488 res = res.changeReturnType(rtype); 489 } 490 return res; 491 } 492 } 493 Class<?> elemType = arrayType.getComponentType(); 494 assert(elemType != null); 495 for (int i = spreadPos; i < ptypes.length; i++) { 496 if (ptypes[i] != elemType) { 497 Class<?>[] fixedPtypes = ptypes.clone(); 498 Arrays.fill(fixedPtypes, i, ptypes.length, elemType); 499 return methodType(rtype, fixedPtypes); 500 } 501 } 502 return this; // arguments check out; no change 503 } 504 505 /** Return the leading parameter type, which must exist and be a reference. 506 * @return the leading parameter type, after error checks 507 */ 508 /*non-public*/ Class<?> leadingReferenceParameter() { 509 Class<?> ptype; 510 if (ptypes.length == 0 || 511 (ptype = ptypes[0]).isPrimitive()) 512 throw newIllegalArgumentException("no leading reference parameter"); 513 return ptype; 514 } 515 516 /** Delete the last parameter type and replace it with arrayLength copies of the component type of arrayType. 517 * @param arrayType any array type 518 * @param arrayLength the number of parameter types to insert 519 * @return the resulting type 520 */ 521 /*non-public*/ MethodType asCollectorType(Class<?> arrayType, int arrayLength) { 522 assert(parameterCount() >= 1); 523 assert(lastParameterType().isAssignableFrom(arrayType)); 524 MethodType res; 525 if (arrayType == Object[].class) { 526 res = genericMethodType(arrayLength); 527 if (rtype != Object.class) { 528 res = res.changeReturnType(rtype); 529 } 530 } else { 531 Class<?> elemType = arrayType.getComponentType(); 532 assert(elemType != null); 533 res = methodType(rtype, Collections.nCopies(arrayLength, elemType)); 534 } 535 if (ptypes.length == 1) { 536 return res; 537 } else { 538 return res.insertParameterTypes(0, parameterList().subList(0, ptypes.length-1)); 539 } 540 } 541 542 /** 543 * Finds or creates a method type with some parameter types omitted. 544 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 545 * @param start the index (zero-based) of the first parameter type to remove 546 * @param end the index (greater than {@code start}) of the first parameter type after not to remove 547 * @return the same type, except with the selected parameter(s) removed 548 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()} 549 * or if {@code end} is negative or greater than {@code parameterCount()} 550 * or if {@code start} is greater than {@code end} 551 */ 552 public MethodType dropParameterTypes(int start, int end) { 553 int len = ptypes.length; 554 if (!(0 <= start && start <= end && end <= len)) 555 throw newIndexOutOfBoundsException("start="+start+" end="+end); 556 if (start == end) return this; 557 Class<?>[] nptypes; 558 if (start == 0) { 559 if (end == len) { 560 // drop all parameters 561 nptypes = NO_PTYPES; 562 } else { 563 // drop initial parameter(s) 564 nptypes = Arrays.copyOfRange(ptypes, end, len); 565 } 566 } else { 567 if (end == len) { 568 // drop trailing parameter(s) 569 nptypes = Arrays.copyOfRange(ptypes, 0, start); 570 } else { 571 int tail = len - end; 572 nptypes = Arrays.copyOfRange(ptypes, 0, start + tail); 573 System.arraycopy(ptypes, end, nptypes, start, tail); 574 } 575 } 576 return makeImpl(rtype, nptypes, true); 577 } 578 579 /** 580 * Finds or creates a method type with a different return type. 581 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 582 * @param nrtype a return parameter type to replace the old one with 583 * @return the same type, except with the return type change 584 * @throws NullPointerException if {@code nrtype} is null 585 */ 586 public MethodType changeReturnType(Class<?> nrtype) { 587 if (returnType() == nrtype) return this; 588 return makeImpl(nrtype, ptypes, true); 589 } 590 591 /** 592 * Reports if this type contains a primitive argument or return value. 593 * The return type {@code void} counts as a primitive. 594 * @return true if any of the types are primitives 595 */ 596 public boolean hasPrimitives() { 597 return form.hasPrimitives(); 598 } 599 600 /** 601 * Reports if this type contains a wrapper argument or return value. 602 * Wrappers are types which box primitive values, such as {@link Integer}. 603 * The reference type {@code java.lang.Void} counts as a wrapper, 604 * if it occurs as a return type. 605 * @return true if any of the types are wrappers 606 */ 607 public boolean hasWrappers() { 608 return unwrap() != this; 609 } 610 611 /** 612 * Erases all reference types to {@code Object}. 613 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 614 * All primitive types (including {@code void}) will remain unchanged. 615 * @return a version of the original type with all reference types replaced 616 */ 617 public MethodType erase() { 618 return form.erasedType(); 619 } 620 621 /** 622 * Erases all reference types to {@code Object}, and all subword types to {@code int}. 623 * This is the reduced type polymorphism used by private methods 624 * such as {@link MethodHandle#invokeBasic invokeBasic}. 625 * @return a version of the original type with all reference and subword types replaced 626 */ 627 /*non-public*/ MethodType basicType() { 628 return form.basicType(); 629 } 630 631 /** 632 * @return a version of the original type with MethodHandle prepended as the first argument 633 */ 634 /*non-public*/ MethodType invokerType() { 635 return insertParameterTypes(0, MethodHandle.class); 636 } 637 638 /** 639 * Converts all types, both reference and primitive, to {@code Object}. 640 * Convenience method for {@link #genericMethodType(int) genericMethodType}. 641 * The expression {@code type.wrap().erase()} produces the same value 642 * as {@code type.generic()}. 643 * @return a version of the original type with all types replaced 644 */ 645 public MethodType generic() { 646 return genericMethodType(parameterCount()); 647 } 648 649 /*non-public*/ boolean isGeneric() { 650 return this == erase() && !hasPrimitives(); 651 } 652 653 /** 654 * Converts all primitive types to their corresponding wrapper types. 655 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 656 * All reference types (including wrapper types) will remain unchanged. 657 * A {@code void} return type is changed to the type {@code java.lang.Void}. 658 * The expression {@code type.wrap().erase()} produces the same value 659 * as {@code type.generic()}. 660 * @return a version of the original type with all primitive types replaced 661 */ 662 public MethodType wrap() { 663 return hasPrimitives() ? wrapWithPrims(this) : this; 664 } 665 666 /** 667 * Converts all wrapper types to their corresponding primitive types. 668 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 669 * All primitive types (including {@code void}) will remain unchanged. 670 * A return type of {@code java.lang.Void} is changed to {@code void}. 671 * @return a version of the original type with all wrapper types replaced 672 */ 673 public MethodType unwrap() { 674 MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this); 675 return unwrapWithNoPrims(noprims); 676 } 677 678 private static MethodType wrapWithPrims(MethodType pt) { 679 assert(pt.hasPrimitives()); 680 MethodType wt = pt.wrapAlt; 681 if (wt == null) { 682 // fill in lazily 683 wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP, MethodTypeForm.WRAP); 684 assert(wt != null); 685 pt.wrapAlt = wt; 686 } 687 return wt; 688 } 689 690 private static MethodType unwrapWithNoPrims(MethodType wt) { 691 assert(!wt.hasPrimitives()); 692 MethodType uwt = wt.wrapAlt; 693 if (uwt == null) { 694 // fill in lazily 695 uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP, MethodTypeForm.UNWRAP); 696 if (uwt == null) 697 uwt = wt; // type has no wrappers or prims at all 698 wt.wrapAlt = uwt; 699 } 700 return uwt; 701 } 702 703 /** 704 * Returns the parameter type at the specified index, within this method type. 705 * @param num the index (zero-based) of the desired parameter type 706 * @return the selected parameter type 707 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()} 708 */ 709 public Class<?> parameterType(int num) { 710 return ptypes[num]; 711 } 712 /** 713 * Returns the number of parameter types in this method type. 714 * @return the number of parameter types 715 */ 716 public int parameterCount() { 717 return ptypes.length; 718 } 719 /** 720 * Returns the return type of this method type. 721 * @return the return type 722 */ 723 public Class<?> returnType() { 724 return rtype; 725 } 726 727 /** 728 * Presents the parameter types as a list (a convenience method). 729 * The list will be immutable. 730 * @return the parameter types (as an immutable list) 731 */ 732 public List<Class<?>> parameterList() { 733 return Collections.unmodifiableList(Arrays.asList(ptypes.clone())); 734 } 735 736 /*non-public*/ Class<?> lastParameterType() { 737 int len = ptypes.length; 738 return len == 0 ? void.class : ptypes[len-1]; 739 } 740 741 /** 742 * Presents the parameter types as an array (a convenience method). 743 * Changes to the array will not result in changes to the type. 744 * @return the parameter types (as a fresh copy if necessary) 745 */ 746 public Class<?>[] parameterArray() { 747 return ptypes.clone(); 748 } 749 750 /** 751 * Compares the specified object with this type for equality. 752 * That is, it returns <tt>true</tt> if and only if the specified object 753 * is also a method type with exactly the same parameters and return type. 754 * @param x object to compare 755 * @see Object#equals(Object) 756 */ 757 @Override 758 public boolean equals(Object x) { 759 return this == x || x instanceof MethodType && equals((MethodType)x); 760 } 761 762 private boolean equals(MethodType that) { 763 return this.rtype == that.rtype 764 && Arrays.equals(this.ptypes, that.ptypes); 765 } 766 767 /** 768 * Returns the hash code value for this method type. 769 * It is defined to be the same as the hashcode of a List 770 * whose elements are the return type followed by the 771 * parameter types. 772 * @return the hash code value for this method type 773 * @see Object#hashCode() 774 * @see #equals(Object) 775 * @see List#hashCode() 776 */ 777 @Override 778 public int hashCode() { 779 int hashCode = 31 + rtype.hashCode(); 780 for (Class<?> ptype : ptypes) 781 hashCode = 31*hashCode + ptype.hashCode(); 782 return hashCode; 783 } 784 785 /** 786 * Returns a string representation of the method type, 787 * of the form {@code "(PT0,PT1...)RT"}. 788 * The string representation of a method type is a 789 * parenthesis enclosed, comma separated list of type names, 790 * followed immediately by the return type. 791 * <p> 792 * Each type is represented by its 793 * {@link java.lang.Class#getSimpleName simple name}. 794 */ 795 @Override 796 public String toString() { 797 StringBuilder sb = new StringBuilder(); 798 sb.append("("); 799 for (int i = 0; i < ptypes.length; i++) { 800 if (i > 0) sb.append(","); 801 sb.append(ptypes[i].getSimpleName()); 802 } 803 sb.append(")"); 804 sb.append(rtype.getSimpleName()); 805 return sb.toString(); 806 } 807 808 /** True if the old return type can always be viewed (w/o casting) under new return type, 809 * and the new parameters can be viewed (w/o casting) under the old parameter types. 810 */ 811 // Android-changed: Removed implementation details. 812 // boolean isViewableAs(MethodType newType, boolean keepInterfaces); 813 // boolean parametersAreViewableAs(MethodType newType, boolean keepInterfaces); 814 /*non-public*/ 815 boolean isConvertibleTo(MethodType newType) { 816 MethodTypeForm oldForm = this.form(); 817 MethodTypeForm newForm = newType.form(); 818 if (oldForm == newForm) 819 // same parameter count, same primitive/object mix 820 return true; 821 if (!canConvert(returnType(), newType.returnType())) 822 return false; 823 Class<?>[] srcTypes = newType.ptypes; 824 Class<?>[] dstTypes = ptypes; 825 if (srcTypes == dstTypes) 826 return true; 827 int argc; 828 if ((argc = srcTypes.length) != dstTypes.length) 829 return false; 830 if (argc <= 1) { 831 if (argc == 1 && !canConvert(srcTypes[0], dstTypes[0])) 832 return false; 833 return true; 834 } 835 if ((oldForm.primitiveParameterCount() == 0 && oldForm.erasedType == this) || 836 (newForm.primitiveParameterCount() == 0 && newForm.erasedType == newType)) { 837 // Somewhat complicated test to avoid a loop of 2 or more trips. 838 // If either type has only Object parameters, we know we can convert. 839 assert(canConvertParameters(srcTypes, dstTypes)); 840 return true; 841 } 842 return canConvertParameters(srcTypes, dstTypes); 843 } 844 845 /** Returns true if MHs.explicitCastArguments produces the same result as MH.asType. 846 * If the type conversion is impossible for either, the result should be false. 847 */ 848 /*non-public*/ 849 boolean explicitCastEquivalentToAsType(MethodType newType) { 850 if (this == newType) return true; 851 if (!explicitCastEquivalentToAsType(rtype, newType.rtype)) { 852 return false; 853 } 854 Class<?>[] srcTypes = newType.ptypes; 855 Class<?>[] dstTypes = ptypes; 856 if (dstTypes == srcTypes) { 857 return true; 858 } 859 assert(dstTypes.length == srcTypes.length); 860 for (int i = 0; i < dstTypes.length; i++) { 861 if (!explicitCastEquivalentToAsType(srcTypes[i], dstTypes[i])) { 862 return false; 863 } 864 } 865 return true; 866 } 867 868 /** Reports true if the src can be converted to the dst, by both asType and MHs.eCE, 869 * and with the same effect. 870 * MHs.eCA has the following "upgrades" to MH.asType: 871 * 1. interfaces are unchecked (that is, treated as if aliased to Object) 872 * Therefore, {@code Object->CharSequence} is possible in both cases but has different semantics 873 * 2a. the full matrix of primitive-to-primitive conversions is supported 874 * Narrowing like {@code long->byte} and basic-typing like {@code boolean->int} 875 * are not supported by asType, but anything supported by asType is equivalent 876 * with MHs.eCE. 877 * 2b. conversion of void->primitive means explicit cast has to insert zero/false/null. 878 * 3a. unboxing conversions can be followed by the full matrix of primitive conversions 879 * 3b. unboxing of null is permitted (creates a zero primitive value) 880 * Other than interfaces, reference-to-reference conversions are the same. 881 * Boxing primitives to references is the same for both operators. 882 */ 883 private static boolean explicitCastEquivalentToAsType(Class<?> src, Class<?> dst) { 884 if (src == dst || dst == Object.class || dst == void.class) { 885 return true; 886 } else if (src.isPrimitive() && src != void.class) { 887 // Could be a prim/prim conversion, where casting is a strict superset. 888 // Or a boxing conversion, which is always to an exact wrapper class. 889 return canConvert(src, dst); 890 } else if (dst.isPrimitive()) { 891 // Unboxing behavior is different between MHs.eCA & MH.asType (see 3b). 892 return false; 893 } else { 894 // R->R always works, but we have to avoid a check-cast to an interface. 895 return !dst.isInterface() || dst.isAssignableFrom(src); 896 } 897 } 898 899 private boolean canConvertParameters(Class<?>[] srcTypes, Class<?>[] dstTypes) { 900 for (int i = 0; i < srcTypes.length; i++) { 901 if (!canConvert(srcTypes[i], dstTypes[i])) { 902 return false; 903 } 904 } 905 return true; 906 } 907 908 /*non-public*/ 909 static boolean canConvert(Class<?> src, Class<?> dst) { 910 // short-circuit a few cases: 911 if (src == dst || src == Object.class || dst == Object.class) return true; 912 // the remainder of this logic is documented in MethodHandle.asType 913 if (src.isPrimitive()) { 914 // can force void to an explicit null, a la reflect.Method.invoke 915 // can also force void to a primitive zero, by analogy 916 if (src == void.class) return true; //or !dst.isPrimitive()? 917 Wrapper sw = Wrapper.forPrimitiveType(src); 918 if (dst.isPrimitive()) { 919 // P->P must widen 920 return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw); 921 } else { 922 // P->R must box and widen 923 return dst.isAssignableFrom(sw.wrapperType()); 924 } 925 } else if (dst.isPrimitive()) { 926 // any value can be dropped 927 if (dst == void.class) return true; 928 Wrapper dw = Wrapper.forPrimitiveType(dst); 929 // R->P must be able to unbox (from a dynamically chosen type) and widen 930 // For example: 931 // Byte/Number/Comparable/Object -> dw:Byte -> byte. 932 // Character/Comparable/Object -> dw:Character -> char 933 // Boolean/Comparable/Object -> dw:Boolean -> boolean 934 // This means that dw must be cast-compatible with src. 935 if (src.isAssignableFrom(dw.wrapperType())) { 936 return true; 937 } 938 // The above does not work if the source reference is strongly typed 939 // to a wrapper whose primitive must be widened. For example: 940 // Byte -> unbox:byte -> short/int/long/float/double 941 // Character -> unbox:char -> int/long/float/double 942 if (Wrapper.isWrapperType(src) && 943 dw.isConvertibleFrom(Wrapper.forWrapperType(src))) { 944 // can unbox from src and then widen to dst 945 return true; 946 } 947 // We have already covered cases which arise due to runtime unboxing 948 // of a reference type which covers several wrapper types: 949 // Object -> cast:Integer -> unbox:int -> long/float/double 950 // Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double 951 // An marginal case is Number -> dw:Character -> char, which would be OK if there were a 952 // subclass of Number which wraps a value that can convert to char. 953 // Since there is none, we don't need an extra check here to cover char or boolean. 954 return false; 955 } else { 956 // R->R always works, since null is always valid dynamically 957 return true; 958 } 959 } 960 961 /** Reports the number of JVM stack slots required to invoke a method 962 * of this type. Note that (for historical reasons) the JVM requires 963 * a second stack slot to pass long and double arguments. 964 * So this method returns {@link #parameterCount() parameterCount} plus the 965 * number of long and double parameters (if any). 966 * <p> 967 * This method is included for the benefit of applications that must 968 * generate bytecodes that process method handles and invokedynamic. 969 * @return the number of JVM stack slots for this type's parameters 970 */ 971 /*non-public*/ int parameterSlotCount() { 972 return form.parameterSlotCount(); 973 } 974 975 /// Queries which have to do with the bytecode architecture 976 977 // Android-changed: These methods aren't needed on Android and are unused within the JDK. 978 // 979 // int parameterSlotDepth(int num); 980 // int returnSlotCount(); 981 // 982 // Android-changed: Removed cache of higher order adapters. 983 // 984 // Invokers invokers(); 985 986 /** 987 * Finds or creates an instance of a method type, given the spelling of its bytecode descriptor. 988 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 989 * Any class or interface name embedded in the descriptor string 990 * will be resolved by calling {@link ClassLoader#loadClass(java.lang.String)} 991 * on the given loader (or if it is null, on the system class loader). 992 * <p> 993 * Note that it is possible to encounter method types which cannot be 994 * constructed by this method, because their component types are 995 * not all reachable from a common class loader. 996 * <p> 997 * This method is included for the benefit of applications that must 998 * generate bytecodes that process method handles and {@code invokedynamic}. 999 * @param descriptor a bytecode-level type descriptor string "(T...)T" 1000 * @param loader the class loader in which to look up the types 1001 * @return a method type matching the bytecode-level type descriptor 1002 * @throws NullPointerException if the string is null 1003 * @throws IllegalArgumentException if the string is not well-formed 1004 * @throws TypeNotPresentException if a named type cannot be found 1005 */ 1006 public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader) 1007 throws IllegalArgumentException, TypeNotPresentException 1008 { 1009 if (!descriptor.startsWith("(") || // also generates NPE if needed 1010 descriptor.indexOf(')') < 0 || 1011 descriptor.indexOf('.') >= 0) 1012 throw newIllegalArgumentException("not a method descriptor: "+descriptor); 1013 List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader); 1014 Class<?> rtype = types.remove(types.size() - 1); 1015 checkSlotCount(types.size()); 1016 Class<?>[] ptypes = listToArray(types); 1017 return makeImpl(rtype, ptypes, true); 1018 } 1019 1020 /** 1021 * Produces a bytecode descriptor representation of the method type. 1022 * <p> 1023 * Note that this is not a strict inverse of {@link #fromMethodDescriptorString fromMethodDescriptorString}. 1024 * Two distinct classes which share a common name but have different class loaders 1025 * will appear identical when viewed within descriptor strings. 1026 * <p> 1027 * This method is included for the benefit of applications that must 1028 * generate bytecodes that process method handles and {@code invokedynamic}. 1029 * {@link #fromMethodDescriptorString(java.lang.String, java.lang.ClassLoader) fromMethodDescriptorString}, 1030 * because the latter requires a suitable class loader argument. 1031 * @return the bytecode type descriptor representation 1032 */ 1033 public String toMethodDescriptorString() { 1034 String desc = methodDescriptor; 1035 if (desc == null) { 1036 desc = BytecodeDescriptor.unparse(this); 1037 methodDescriptor = desc; 1038 } 1039 return desc; 1040 } 1041 1042 /*non-public*/ static String toFieldDescriptorString(Class<?> cls) { 1043 return BytecodeDescriptor.unparse(cls); 1044 } 1045 1046 /// Serialization. 1047 1048 /** 1049 * There are no serializable fields for {@code MethodType}. 1050 */ 1051 private static final java.io.ObjectStreamField[] serialPersistentFields = { }; 1052 1053 /** 1054 * Save the {@code MethodType} instance to a stream. 1055 * 1056 * @serialData 1057 * For portability, the serialized format does not refer to named fields. 1058 * Instead, the return type and parameter type arrays are written directly 1059 * from the {@code writeObject} method, using two calls to {@code s.writeObject} 1060 * as follows: 1061 * <blockquote><pre>{@code 1062 s.writeObject(this.returnType()); 1063 s.writeObject(this.parameterArray()); 1064 * }</pre></blockquote> 1065 * <p> 1066 * The deserialized field values are checked as if they were 1067 * provided to the factory method {@link #methodType(Class,Class[]) methodType}. 1068 * For example, null values, or {@code void} parameter types, 1069 * will lead to exceptions during deserialization. 1070 * @param s the stream to write the object to 1071 * @throws java.io.IOException if there is a problem writing the object 1072 */ 1073 private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException { 1074 s.defaultWriteObject(); // requires serialPersistentFields to be an empty array 1075 s.writeObject(returnType()); 1076 s.writeObject(parameterArray()); 1077 } 1078 1079 /** 1080 * Reconstitute the {@code MethodType} instance from a stream (that is, 1081 * deserialize it). 1082 * This instance is a scratch object with bogus final fields. 1083 * It provides the parameters to the factory method called by 1084 * {@link #readResolve readResolve}. 1085 * After that call it is discarded. 1086 * @param s the stream to read the object from 1087 * @throws java.io.IOException if there is a problem reading the object 1088 * @throws ClassNotFoundException if one of the component classes cannot be resolved 1089 * @see #MethodType() 1090 * @see #readResolve 1091 * @see #writeObject 1092 */ 1093 private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException { 1094 s.defaultReadObject(); // requires serialPersistentFields to be an empty array 1095 1096 Class<?> returnType = (Class<?>) s.readObject(); 1097 Class<?>[] parameterArray = (Class<?>[]) s.readObject(); 1098 1099 // Probably this object will never escape, but let's check 1100 // the field values now, just to be sure. 1101 checkRtype(returnType); 1102 checkPtypes(parameterArray); 1103 1104 parameterArray = parameterArray.clone(); // make sure it is unshared 1105 MethodType_init(returnType, parameterArray); 1106 } 1107 1108 /** 1109 * For serialization only. 1110 * Sets the final fields to null, pending {@code Unsafe.putObject}. 1111 */ 1112 private MethodType() { 1113 this.rtype = null; 1114 this.ptypes = null; 1115 } 1116 private void MethodType_init(Class<?> rtype, Class<?>[] ptypes) { 1117 // In order to communicate these values to readResolve, we must 1118 // store them into the implementation-specific final fields. 1119 checkRtype(rtype); 1120 checkPtypes(ptypes); 1121 UNSAFE.putObject(this, rtypeOffset, rtype); 1122 UNSAFE.putObject(this, ptypesOffset, ptypes); 1123 } 1124 1125 // Support for resetting final fields while deserializing 1126 private static final long rtypeOffset, ptypesOffset; 1127 static { 1128 try { 1129 rtypeOffset = UNSAFE.objectFieldOffset 1130 (MethodType.class.getDeclaredField("rtype")); 1131 ptypesOffset = UNSAFE.objectFieldOffset 1132 (MethodType.class.getDeclaredField("ptypes")); 1133 } catch (Exception ex) { 1134 throw new Error(ex); 1135 } 1136 } 1137 1138 /** 1139 * Resolves and initializes a {@code MethodType} object 1140 * after serialization. 1141 * @return the fully initialized {@code MethodType} object 1142 */ 1143 private Object readResolve() { 1144 // Do not use a trusted path for deserialization: 1145 //return makeImpl(rtype, ptypes, true); 1146 // Verify all operands, and make sure ptypes is unshared: 1147 return methodType(rtype, ptypes); 1148 } 1149 1150 /** 1151 * Simple implementation of weak concurrent intern set. 1152 * 1153 * @param <T> interned type 1154 */ 1155 private static class ConcurrentWeakInternSet<T> { 1156 1157 private final ConcurrentMap<WeakEntry<T>, WeakEntry<T>> map; 1158 private final ReferenceQueue<T> stale; 1159 1160 public ConcurrentWeakInternSet() { 1161 this.map = new ConcurrentHashMap<>(); 1162 this.stale = new ReferenceQueue<>(); 1163 } 1164 1165 /** 1166 * Get the existing interned element. 1167 * This method returns null if no element is interned. 1168 * 1169 * @param elem element to look up 1170 * @return the interned element 1171 */ 1172 public T get(T elem) { 1173 if (elem == null) throw new NullPointerException(); 1174 expungeStaleElements(); 1175 1176 WeakEntry<T> value = map.get(new WeakEntry<>(elem)); 1177 if (value != null) { 1178 T res = value.get(); 1179 if (res != null) { 1180 return res; 1181 } 1182 } 1183 return null; 1184 } 1185 1186 /** 1187 * Interns the element. 1188 * Always returns non-null element, matching the one in the intern set. 1189 * Under the race against another add(), it can return <i>different</i> 1190 * element, if another thread beats us to interning it. 1191 * 1192 * @param elem element to add 1193 * @return element that was actually added 1194 */ 1195 public T add(T elem) { 1196 if (elem == null) throw new NullPointerException(); 1197 1198 // Playing double race here, and so spinloop is required. 1199 // First race is with two concurrent updaters. 1200 // Second race is with GC purging weak ref under our feet. 1201 // Hopefully, we almost always end up with a single pass. 1202 T interned; 1203 WeakEntry<T> e = new WeakEntry<>(elem, stale); 1204 do { 1205 expungeStaleElements(); 1206 WeakEntry<T> exist = map.putIfAbsent(e, e); 1207 interned = (exist == null) ? elem : exist.get(); 1208 } while (interned == null); 1209 return interned; 1210 } 1211 1212 private void expungeStaleElements() { 1213 Reference<? extends T> reference; 1214 while ((reference = stale.poll()) != null) { 1215 map.remove(reference); 1216 } 1217 } 1218 1219 private static class WeakEntry<T> extends WeakReference<T> { 1220 1221 public final int hashcode; 1222 1223 public WeakEntry(T key, ReferenceQueue<T> queue) { 1224 super(key, queue); 1225 hashcode = key.hashCode(); 1226 } 1227 1228 public WeakEntry(T key) { 1229 super(key); 1230 hashcode = key.hashCode(); 1231 } 1232 1233 @Override 1234 public boolean equals(Object obj) { 1235 if (obj instanceof WeakEntry) { 1236 Object that = ((WeakEntry) obj).get(); 1237 Object mine = get(); 1238 return (that == null || mine == null) ? (this == obj) : mine.equals(that); 1239 } 1240 return false; 1241 } 1242 1243 @Override 1244 public int hashCode() { 1245 return hashcode; 1246 } 1247 1248 } 1249 } 1250 1251 } 1252
