1 /* 2 * Copyright (c) 2008, 2020, 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 java.lang.constant.ClassDesc; 29 import java.lang.constant.Constable; 30 import java.lang.constant.MethodTypeDesc; 31 import java.lang.ref.Reference; 32 import java.lang.ref.ReferenceQueue; 33 import java.lang.ref.WeakReference; 34 import java.util.Arrays; 35 import java.util.Collections; 36 import java.util.List; 37 import java.util.NoSuchElementException; 38 import java.util.Objects; 39 import java.util.Optional; 40 import java.util.StringJoiner; 41 import java.util.concurrent.ConcurrentHashMap; 42 import java.util.concurrent.ConcurrentMap; 43 import java.util.stream.Stream; 44 45 import jdk.internal.vm.annotation.Stable; 46 import sun.invoke.util.BytecodeDescriptor; 47 import sun.invoke.util.VerifyType; 48 import sun.invoke.util.Wrapper; 49 import sun.security.util.SecurityConstants; 50 51 import static java.lang.invoke.MethodHandleStatics.UNSAFE; 52 import static java.lang.invoke.MethodHandleStatics.newIllegalArgumentException; 53 import static java.lang.invoke.MethodType.fromDescriptor; 54 55 /** 56 * A method type represents the arguments and return type accepted and 57 * returned by a method handle, or the arguments and return type passed 58 * and expected by a method handle caller. Method types must be properly 59 * matched between a method handle and all its callers, 60 * and the JVM's operations enforce this matching at, specifically 61 * during calls to {@link MethodHandle#invokeExact MethodHandle.invokeExact} 62 * and {@link MethodHandle#invoke MethodHandle.invoke}, and during execution 63 * of {@code invokedynamic} instructions. 64 * <p> 65 * The structure is a return type accompanied by any number of parameter types. 66 * The types (primitive, {@code void}, and reference) are represented by {@link Class} objects. 67 * (For ease of exposition, we treat {@code void} as if it were a type. 68 * In fact, it denotes the absence of a return type.) 69 * <p> 70 * All instances of {@code MethodType} are immutable. 71 * Two instances are completely interchangeable if they compare equal. 72 * Equality depends on pairwise correspondence of the return and parameter types and on nothing else. 73 * <p> 74 * This type can be created only by factory methods. 75 * All factory methods may cache values, though caching is not guaranteed. 76 * Some factory methods are static, while others are virtual methods which 77 * modify precursor method types, e.g., by changing a selected parameter. 78 * <p> 79 * Factory methods which operate on groups of parameter types 80 * are systematically presented in two versions, so that both Java arrays and 81 * Java lists can be used to work with groups of parameter types. 82 * The query methods {@code parameterArray} and {@code parameterList} 83 * also provide a choice between arrays and lists. 84 * <p> 85 * {@code MethodType} objects are sometimes derived from bytecode instructions 86 * such as {@code invokedynamic}, specifically from the type descriptor strings associated 87 * with the instructions in a class file's constant pool. 88 * <p> 89 * Like classes and strings, method types can also be represented directly 90 * in a class file's constant pool as constants. 91 * A method type may be loaded by an {@code ldc} instruction which refers 92 * to a suitable {@code CONSTANT_MethodType} constant pool entry. 93 * The entry refers to a {@code CONSTANT_Utf8} spelling for the descriptor string. 94 * (For full details on method type constants, see sections {@jvms 95 * 4.4.8} and {@jvms 5.4.3.5} of the Java Virtual Machine 96 * Specification.) 97 * <p> 98 * When the JVM materializes a {@code MethodType} from a descriptor string, 99 * all classes named in the descriptor must be accessible, and will be loaded. 100 * (But the classes need not be initialized, as is the case with a {@code CONSTANT_Class}.) 101 * This loading may occur at any time before the {@code MethodType} object is first derived. 102 * <p> 103 * <b><a id="descriptor">Nominal Descriptors</a></b> 104 * <p> 105 * A {@code MethodType} can be described in {@linkplain MethodTypeDesc nominal form} 106 * if and only if all of the parameter types and return type can be described 107 * with a {@link Class#describeConstable() nominal descriptor} represented by 108 * {@link ClassDesc}. If a method type can be described nominally, then: 109 * <ul> 110 * <li>The method type has a {@link MethodTypeDesc nominal descriptor} 111 * returned by {@link #describeConstable() MethodType::describeConstable}.</li> 112 * <li>The descriptor string returned by 113 * {@link #descriptorString() MethodType::descriptorString} or 114 * {@link #toMethodDescriptorString() MethodType::toMethodDescriptorString} 115 * for the method type is a method descriptor (JVMS {@jvms 4.3.3}).</li> 116 * </ul> 117 * <p> 118 * If any of the parameter types or return type cannot be described 119 * nominally, i.e. {@link Class#describeConstable() Class::describeConstable} 120 * returns an empty optional for that type, 121 * then the method type cannot be described nominally: 122 * <ul> 123 * <li>The method type has no {@link MethodTypeDesc nominal descriptor} and 124 * {@link #describeConstable() MethodType::describeConstable} returns 125 * an empty optional.</li> 126 * <li>The descriptor string returned by 127 * {@link #descriptorString() MethodType::descriptorString} or 128 * {@link #toMethodDescriptorString() MethodType::toMethodDescriptorString} 129 * for the method type is not a type descriptor.</li> 130 * </ul> 131 * 132 * @author John Rose, JSR 292 EG 133 * @since 1.7 134 */ 135 public final 136 class MethodType 137 implements Constable, 138 TypeDescriptor.OfMethod<Class<?>, MethodType>, 139 java.io.Serializable { 140 @java.io.Serial 141 private static final long serialVersionUID = 292L; // {rtype, {ptype...}} 142 143 // The rtype and ptypes fields define the structural identity of the method type: 144 private final @Stable Class<?> rtype; 145 private final @Stable Class<?>[] ptypes; 146 147 // The remaining fields are caches of various sorts: 148 private @Stable MethodTypeForm form; // erased form, plus cached data about primitives 149 private @Stable Object wrapAlt; // alternative wrapped/unwrapped version and 150 // private communication for readObject and readResolve 151 private @Stable Invokers invokers; // cache of handy higher-order adapters 152 private @Stable String methodDescriptor; // cache for toMethodDescriptorString 153 154 /** 155 * Constructor that performs no copying or validation. 156 * Should only be called from the factory method makeImpl 157 */ MethodType(Class<?> rtype, Class<?>[] ptypes)158 private MethodType(Class<?> rtype, Class<?>[] ptypes) { 159 this.rtype = rtype; 160 this.ptypes = ptypes; 161 } 162 form()163 /*trusted*/ MethodTypeForm form() { return form; } rtype()164 /*trusted*/ Class<?> rtype() { return rtype; } ptypes()165 /*trusted*/ Class<?>[] ptypes() { return ptypes; } 166 setForm(MethodTypeForm f)167 void setForm(MethodTypeForm f) { form = f; } 168 169 /** This number, mandated by the JVM spec as 255, 170 * is the maximum number of <em>slots</em> 171 * that any Java method can receive in its argument list. 172 * It limits both JVM signatures and method type objects. 173 * The longest possible invocation will look like 174 * {@code staticMethod(arg1, arg2, ..., arg255)} or 175 * {@code x.virtualMethod(arg1, arg2, ..., arg254)}. 176 */ 177 /*non-public*/ 178 static final int MAX_JVM_ARITY = 255; // this is mandated by the JVM spec. 179 180 /** This number is the maximum arity of a method handle, 254. 181 * It is derived from the absolute JVM-imposed arity by subtracting one, 182 * which is the slot occupied by the method handle itself at the 183 * beginning of the argument list used to invoke the method handle. 184 * The longest possible invocation will look like 185 * {@code mh.invoke(arg1, arg2, ..., arg254)}. 186 */ 187 // Issue: Should we allow MH.invokeWithArguments to go to the full 255? 188 /*non-public*/ 189 static final int MAX_MH_ARITY = MAX_JVM_ARITY-1; // deduct one for mh receiver 190 191 /** This number is the maximum arity of a method handle invoker, 253. 192 * It is derived from the absolute JVM-imposed arity by subtracting two, 193 * which are the slots occupied by invoke method handle, and the 194 * target method handle, which are both at the beginning of the argument 195 * list used to invoke the target method handle. 196 * The longest possible invocation will look like 197 * {@code invokermh.invoke(targetmh, arg1, arg2, ..., arg253)}. 198 */ 199 /*non-public*/ 200 static final int MAX_MH_INVOKER_ARITY = MAX_MH_ARITY-1; // deduct one more for invoker 201 checkRtype(Class<?> rtype)202 private static void checkRtype(Class<?> rtype) { 203 Objects.requireNonNull(rtype); 204 } checkPtype(Class<?> ptype)205 private static void checkPtype(Class<?> ptype) { 206 Objects.requireNonNull(ptype); 207 if (ptype == void.class) 208 throw newIllegalArgumentException("parameter type cannot be void"); 209 } 210 /** Return number of extra slots (count of long/double args). */ checkPtypes(Class<?>[] ptypes)211 private static int checkPtypes(Class<?>[] ptypes) { 212 int slots = 0; 213 for (Class<?> ptype : ptypes) { 214 checkPtype(ptype); 215 if (ptype == double.class || ptype == long.class) { 216 slots++; 217 } 218 } 219 checkSlotCount(ptypes.length + slots); 220 return slots; 221 } 222 223 static { 224 // MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work: assert(MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0225 assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0); 226 } checkSlotCount(int count)227 static void checkSlotCount(int count) { 228 if ((count & MAX_JVM_ARITY) != count) 229 throw newIllegalArgumentException("bad parameter count "+count); 230 } newIndexOutOfBoundsException(Object num)231 private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) { 232 if (num instanceof Integer) num = "bad index: "+num; 233 return new IndexOutOfBoundsException(num.toString()); 234 } 235 236 static final ConcurrentWeakInternSet<MethodType> internTable = new ConcurrentWeakInternSet<>(); 237 238 static final Class<?>[] NO_PTYPES = {}; 239 240 /** 241 * Finds or creates an instance of the given method type. 242 * @param rtype the return type 243 * @param ptypes the parameter types 244 * @return a method type with the given components 245 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null 246 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class} 247 */ methodType(Class<?> rtype, Class<?>[] ptypes)248 public static MethodType methodType(Class<?> rtype, Class<?>[] ptypes) { 249 return makeImpl(rtype, ptypes, false); 250 } 251 252 /** 253 * Finds or creates a method type with the given components. 254 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 255 * @param rtype the return type 256 * @param ptypes the parameter types 257 * @return a method type with the given components 258 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null 259 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class} 260 */ methodType(Class<?> rtype, List<Class<?>> ptypes)261 public static MethodType methodType(Class<?> rtype, List<Class<?>> ptypes) { 262 boolean notrust = false; // random List impl. could return evil ptypes array 263 return makeImpl(rtype, listToArray(ptypes), notrust); 264 } 265 listToArray(List<Class<?>> ptypes)266 private static Class<?>[] listToArray(List<Class<?>> ptypes) { 267 // sanity check the size before the toArray call, since size might be huge 268 checkSlotCount(ptypes.size()); 269 return ptypes.toArray(NO_PTYPES); 270 } 271 272 /** 273 * Finds or creates a method type with the given components. 274 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 275 * The leading parameter type is prepended to the remaining array. 276 * @param rtype the return type 277 * @param ptype0 the first parameter type 278 * @param ptypes the remaining parameter types 279 * @return a method type with the given components 280 * @throws NullPointerException if {@code rtype} or {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is null 281 * @throws IllegalArgumentException if {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is {@code void.class} 282 */ methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes)283 public static MethodType methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes) { 284 Class<?>[] ptypes1 = new Class<?>[1+ptypes.length]; 285 ptypes1[0] = ptype0; 286 System.arraycopy(ptypes, 0, ptypes1, 1, ptypes.length); 287 return makeImpl(rtype, ptypes1, true); 288 } 289 290 /** 291 * Finds or creates a method type with the given components. 292 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 293 * The resulting method has no parameter types. 294 * @param rtype the return type 295 * @return a method type with the given return value 296 * @throws NullPointerException if {@code rtype} is null 297 */ methodType(Class<?> rtype)298 public static MethodType methodType(Class<?> rtype) { 299 return makeImpl(rtype, NO_PTYPES, true); 300 } 301 302 /** 303 * Finds or creates a method type with the given components. 304 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 305 * The resulting method has the single given parameter type. 306 * @param rtype the return type 307 * @param ptype0 the parameter type 308 * @return a method type with the given return value and parameter type 309 * @throws NullPointerException if {@code rtype} or {@code ptype0} is null 310 * @throws IllegalArgumentException if {@code ptype0} is {@code void.class} 311 */ methodType(Class<?> rtype, Class<?> ptype0)312 public static MethodType methodType(Class<?> rtype, Class<?> ptype0) { 313 return makeImpl(rtype, new Class<?>[]{ ptype0 }, true); 314 } 315 316 /** 317 * Finds or creates a method type with the given components. 318 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 319 * The resulting method has the same parameter types as {@code ptypes}, 320 * and the specified return type. 321 * @param rtype the return type 322 * @param ptypes the method type which supplies the parameter types 323 * @return a method type with the given components 324 * @throws NullPointerException if {@code rtype} or {@code ptypes} is null 325 */ methodType(Class<?> rtype, MethodType ptypes)326 public static MethodType methodType(Class<?> rtype, MethodType ptypes) { 327 return makeImpl(rtype, ptypes.ptypes, true); 328 } 329 330 /** 331 * Sole factory method to find or create an interned method type. 332 * @param rtype desired return type 333 * @param ptypes desired parameter types 334 * @param trusted whether the ptypes can be used without cloning 335 * @return the unique method type of the desired structure 336 */ 337 /*trusted*/ makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted)338 static MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) { 339 if (ptypes.length == 0) { 340 ptypes = NO_PTYPES; trusted = true; 341 } 342 MethodType primordialMT = new MethodType(rtype, ptypes); 343 MethodType mt = internTable.get(primordialMT); 344 if (mt != null) 345 return mt; 346 347 // promote the object to the Real Thing, and reprobe 348 MethodType.checkRtype(rtype); 349 if (trusted) { 350 MethodType.checkPtypes(ptypes); 351 mt = primordialMT; 352 } else { 353 // Make defensive copy then validate 354 ptypes = Arrays.copyOf(ptypes, ptypes.length); 355 MethodType.checkPtypes(ptypes); 356 mt = new MethodType(rtype, ptypes); 357 } 358 mt.form = MethodTypeForm.findForm(mt); 359 return internTable.add(mt); 360 } 361 private static final @Stable MethodType[] objectOnlyTypes = new MethodType[20]; 362 363 /** 364 * Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array. 365 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 366 * All parameters and the return type will be {@code Object}, 367 * except the final array parameter if any, which will be {@code Object[]}. 368 * @param objectArgCount number of parameters (excluding the final array parameter if any) 369 * @param finalArray whether there will be a trailing array parameter, of type {@code Object[]} 370 * @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments 371 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true) 372 * @see #genericMethodType(int) 373 */ genericMethodType(int objectArgCount, boolean finalArray)374 public static MethodType genericMethodType(int objectArgCount, boolean finalArray) { 375 MethodType mt; 376 checkSlotCount(objectArgCount); 377 int ivarargs = (!finalArray ? 0 : 1); 378 int ootIndex = objectArgCount*2 + ivarargs; 379 if (ootIndex < objectOnlyTypes.length) { 380 mt = objectOnlyTypes[ootIndex]; 381 if (mt != null) return mt; 382 } 383 Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs]; 384 Arrays.fill(ptypes, Object.class); 385 if (ivarargs != 0) ptypes[objectArgCount] = Object[].class; 386 mt = makeImpl(Object.class, ptypes, true); 387 if (ootIndex < objectOnlyTypes.length) { 388 objectOnlyTypes[ootIndex] = mt; // cache it here also! 389 } 390 return mt; 391 } 392 393 /** 394 * Finds or creates a method type whose components are all {@code Object}. 395 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 396 * All parameters and the return type will be Object. 397 * @param objectArgCount number of parameters 398 * @return a generally applicable method type, for all calls of the given argument count 399 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 400 * @see #genericMethodType(int, boolean) 401 */ genericMethodType(int objectArgCount)402 public static MethodType genericMethodType(int objectArgCount) { 403 return genericMethodType(objectArgCount, false); 404 } 405 406 /** 407 * Finds or creates a method type with a single different parameter type. 408 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 409 * @param num the index (zero-based) of the parameter type to change 410 * @param nptype a new parameter type to replace the old one with 411 * @return the same type, except with the selected parameter changed 412 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()} 413 * @throws IllegalArgumentException if {@code nptype} is {@code void.class} 414 * @throws NullPointerException if {@code nptype} is null 415 */ changeParameterType(int num, Class<?> nptype)416 public MethodType changeParameterType(int num, Class<?> nptype) { 417 if (parameterType(num) == nptype) return this; 418 checkPtype(nptype); 419 Class<?>[] nptypes = ptypes.clone(); 420 nptypes[num] = nptype; 421 return makeImpl(rtype, nptypes, true); 422 } 423 424 /** 425 * Finds or creates a method type with additional parameter types. 426 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 427 * @param num the position (zero-based) of the inserted parameter type(s) 428 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list 429 * @return the same type, except with the selected parameter(s) inserted 430 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()} 431 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} 432 * or if the resulting method type would have more than 255 parameter slots 433 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null 434 */ insertParameterTypes(int num, Class<?>... ptypesToInsert)435 public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) { 436 int len = ptypes.length; 437 if (num < 0 || num > len) 438 throw newIndexOutOfBoundsException(num); 439 int ins = checkPtypes(ptypesToInsert); 440 checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins); 441 int ilen = ptypesToInsert.length; 442 if (ilen == 0) return this; 443 Class<?>[] nptypes = new Class<?>[len + ilen]; 444 if (num > 0) { 445 System.arraycopy(ptypes, 0, nptypes, 0, num); 446 } 447 System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen); 448 if (num < len) { 449 System.arraycopy(ptypes, num, nptypes, num+ilen, len-num); 450 } 451 return makeImpl(rtype, nptypes, true); 452 } 453 454 /** 455 * Finds or creates a method type with additional parameter types. 456 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 457 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list 458 * @return the same type, except with the selected parameter(s) appended 459 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} 460 * or if the resulting method type would have more than 255 parameter slots 461 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null 462 */ appendParameterTypes(Class<?>.... ptypesToInsert)463 public MethodType appendParameterTypes(Class<?>... ptypesToInsert) { 464 return insertParameterTypes(parameterCount(), ptypesToInsert); 465 } 466 467 /** 468 * Finds or creates a method type with additional parameter types. 469 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 470 * @param num the position (zero-based) of the inserted parameter type(s) 471 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list 472 * @return the same type, except with the selected parameter(s) inserted 473 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()} 474 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} 475 * or if the resulting method type would have more than 255 parameter slots 476 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null 477 */ insertParameterTypes(int num, List<Class<?>> ptypesToInsert)478 public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) { 479 return insertParameterTypes(num, listToArray(ptypesToInsert)); 480 } 481 482 /** 483 * Finds or creates a method type with additional parameter types. 484 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 485 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list 486 * @return the same type, except with the selected parameter(s) appended 487 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} 488 * or if the resulting method type would have more than 255 parameter slots 489 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null 490 */ appendParameterTypes(List<Class<?>> ptypesToInsert)491 public MethodType appendParameterTypes(List<Class<?>> ptypesToInsert) { 492 return insertParameterTypes(parameterCount(), ptypesToInsert); 493 } 494 495 /** 496 * Finds or creates a method type with modified parameter types. 497 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 498 * @param start the position (zero-based) of the first replaced parameter type(s) 499 * @param end the position (zero-based) after the last replaced parameter type(s) 500 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list 501 * @return the same type, except with the selected parameter(s) replaced 502 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()} 503 * or if {@code end} is negative or greater than {@code parameterCount()} 504 * or if {@code start} is greater than {@code end} 505 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class} 506 * or if the resulting method type would have more than 255 parameter slots 507 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null 508 */ 509 /*non-public*/ replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert)510 MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) { 511 if (start == end) 512 return insertParameterTypes(start, ptypesToInsert); 513 int len = ptypes.length; 514 if (!(0 <= start && start <= end && end <= len)) 515 throw newIndexOutOfBoundsException("start="+start+" end="+end); 516 int ilen = ptypesToInsert.length; 517 if (ilen == 0) 518 return dropParameterTypes(start, end); 519 return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert); 520 } 521 522 /** Replace the last arrayLength parameter types with the component type of arrayType. 523 * @param arrayType any array type 524 * @param pos position at which to spread 525 * @param arrayLength the number of parameter types to change 526 * @return the resulting type 527 */ 528 /*non-public*/ asSpreaderType(Class<?> arrayType, int pos, int arrayLength)529 MethodType asSpreaderType(Class<?> arrayType, int pos, int arrayLength) { 530 assert(parameterCount() >= arrayLength); 531 int spreadPos = pos; 532 if (arrayLength == 0) return this; // nothing to change 533 if (arrayType == Object[].class) { 534 if (isGeneric()) return this; // nothing to change 535 if (spreadPos == 0) { 536 // no leading arguments to preserve; go generic 537 MethodType res = genericMethodType(arrayLength); 538 if (rtype != Object.class) { 539 res = res.changeReturnType(rtype); 540 } 541 return res; 542 } 543 } 544 Class<?> elemType = arrayType.getComponentType(); 545 assert(elemType != null); 546 for (int i = spreadPos; i < spreadPos + arrayLength; i++) { 547 if (ptypes[i] != elemType) { 548 Class<?>[] fixedPtypes = ptypes.clone(); 549 Arrays.fill(fixedPtypes, i, spreadPos + arrayLength, elemType); 550 return methodType(rtype, fixedPtypes); 551 } 552 } 553 return this; // arguments check out; no change 554 } 555 556 /** Return the leading parameter type, which must exist and be a reference. 557 * @return the leading parameter type, after error checks 558 */ 559 /*non-public*/ leadingReferenceParameter()560 Class<?> leadingReferenceParameter() { 561 Class<?> ptype; 562 if (ptypes.length == 0 || 563 (ptype = ptypes[0]).isPrimitive()) 564 throw newIllegalArgumentException("no leading reference parameter"); 565 return ptype; 566 } 567 568 /** Delete the last parameter type and replace it with arrayLength copies of the component type of arrayType. 569 * @param arrayType any array type 570 * @param pos position at which to insert parameters 571 * @param arrayLength the number of parameter types to insert 572 * @return the resulting type 573 */ 574 /*non-public*/ asCollectorType(Class<?> arrayType, int pos, int arrayLength)575 MethodType asCollectorType(Class<?> arrayType, int pos, int arrayLength) { 576 assert(parameterCount() >= 1); 577 assert(pos < ptypes.length); 578 assert(ptypes[pos].isAssignableFrom(arrayType)); 579 MethodType res; 580 if (arrayType == Object[].class) { 581 res = genericMethodType(arrayLength); 582 if (rtype != Object.class) { 583 res = res.changeReturnType(rtype); 584 } 585 } else { 586 Class<?> elemType = arrayType.getComponentType(); 587 assert(elemType != null); 588 res = methodType(rtype, Collections.nCopies(arrayLength, elemType)); 589 } 590 if (ptypes.length == 1) { 591 return res; 592 } else { 593 // insert after (if need be), then before 594 if (pos < ptypes.length - 1) { 595 res = res.insertParameterTypes(arrayLength, Arrays.copyOfRange(ptypes, pos + 1, ptypes.length)); 596 } 597 return res.insertParameterTypes(0, Arrays.copyOf(ptypes, pos)); 598 } 599 } 600 601 /** 602 * Finds or creates a method type with some parameter types omitted. 603 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 604 * @param start the index (zero-based) of the first parameter type to remove 605 * @param end the index (greater than {@code start}) of the first parameter type after not to remove 606 * @return the same type, except with the selected parameter(s) removed 607 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()} 608 * or if {@code end} is negative or greater than {@code parameterCount()} 609 * or if {@code start} is greater than {@code end} 610 */ 611 public MethodType dropParameterTypes(int start, int end) { 612 int len = ptypes.length; 613 if (!(0 <= start && start <= end && end <= len)) 614 throw newIndexOutOfBoundsException("start="+start+" end="+end); 615 if (start == end) return this; 616 Class<?>[] nptypes; 617 if (start == 0) { 618 if (end == len) { 619 // drop all parameters 620 nptypes = NO_PTYPES; 621 } else { 622 // drop initial parameter(s) 623 nptypes = Arrays.copyOfRange(ptypes, end, len); 624 } 625 } else { 626 if (end == len) { 627 // drop trailing parameter(s) 628 nptypes = Arrays.copyOfRange(ptypes, 0, start); 629 } else { 630 int tail = len - end; 631 nptypes = Arrays.copyOfRange(ptypes, 0, start + tail); 632 System.arraycopy(ptypes, end, nptypes, start, tail); 633 } 634 } 635 return makeImpl(rtype, nptypes, true); 636 } 637 638 /** 639 * Finds or creates a method type with a different return type. 640 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 641 * @param nrtype a return parameter type to replace the old one with 642 * @return the same type, except with the return type change 643 * @throws NullPointerException if {@code nrtype} is null 644 */ 645 public MethodType changeReturnType(Class<?> nrtype) { 646 if (returnType() == nrtype) return this; 647 return makeImpl(nrtype, ptypes, true); 648 } 649 650 /** 651 * Reports if this type contains a primitive argument or return value. 652 * The return type {@code void} counts as a primitive. 653 * @return true if any of the types are primitives 654 */ 655 public boolean hasPrimitives() { 656 return form.hasPrimitives(); 657 } 658 659 /** 660 * Reports if this type contains a wrapper argument or return value. 661 * Wrappers are types which box primitive values, such as {@link Integer}. 662 * The reference type {@code java.lang.Void} counts as a wrapper, 663 * if it occurs as a return type. 664 * @return true if any of the types are wrappers 665 */ 666 public boolean hasWrappers() { 667 return unwrap() != this; 668 } 669 670 /** 671 * Erases all reference types to {@code Object}. 672 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 673 * All primitive types (including {@code void}) will remain unchanged. 674 * @return a version of the original type with all reference types replaced 675 */ 676 public MethodType erase() { 677 return form.erasedType(); 678 } 679 680 /** 681 * Erases all reference types to {@code Object}, and all subword types to {@code int}. 682 * This is the reduced type polymorphism used by private methods 683 * such as {@link MethodHandle#invokeBasic invokeBasic}. 684 * @return a version of the original type with all reference and subword types replaced 685 */ 686 /*non-public*/ 687 MethodType basicType() { 688 return form.basicType(); 689 } 690 691 private static final @Stable Class<?>[] METHOD_HANDLE_ARRAY 692 = new Class<?>[] { MethodHandle.class }; 693 694 /** 695 * @return a version of the original type with MethodHandle prepended as the first argument 696 */ 697 /*non-public*/ 698 MethodType invokerType() { 699 return insertParameterTypes(0, METHOD_HANDLE_ARRAY); 700 } 701 702 /** 703 * Converts all types, both reference and primitive, to {@code Object}. 704 * Convenience method for {@link #genericMethodType(int) genericMethodType}. 705 * The expression {@code type.wrap().erase()} produces the same value 706 * as {@code type.generic()}. 707 * @return a version of the original type with all types replaced 708 */ 709 public MethodType generic() { 710 return genericMethodType(parameterCount()); 711 } 712 713 /*non-public*/ 714 boolean isGeneric() { 715 return this == erase() && !hasPrimitives(); 716 } 717 718 /** 719 * Converts all primitive types to their corresponding wrapper types. 720 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 721 * All reference types (including wrapper types) will remain unchanged. 722 * A {@code void} return type is changed to the type {@code java.lang.Void}. 723 * The expression {@code type.wrap().erase()} produces the same value 724 * as {@code type.generic()}. 725 * @return a version of the original type with all primitive types replaced 726 */ 727 public MethodType wrap() { 728 return hasPrimitives() ? wrapWithPrims(this) : this; 729 } 730 731 /** 732 * Converts all wrapper types to their corresponding primitive types. 733 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 734 * All primitive types (including {@code void}) will remain unchanged. 735 * A return type of {@code java.lang.Void} is changed to {@code void}. 736 * @return a version of the original type with all wrapper types replaced 737 */ 738 public MethodType unwrap() { 739 MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this); 740 return unwrapWithNoPrims(noprims); 741 } 742 743 private static MethodType wrapWithPrims(MethodType pt) { 744 assert(pt.hasPrimitives()); 745 MethodType wt = (MethodType)pt.wrapAlt; 746 if (wt == null) { 747 // fill in lazily 748 wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP, MethodTypeForm.WRAP); 749 assert(wt != null); 750 pt.wrapAlt = wt; 751 } 752 return wt; 753 } 754 755 private static MethodType unwrapWithNoPrims(MethodType wt) { 756 assert(!wt.hasPrimitives()); 757 MethodType uwt = (MethodType)wt.wrapAlt; 758 if (uwt == null) { 759 // fill in lazily 760 uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP, MethodTypeForm.UNWRAP); 761 if (uwt == null) 762 uwt = wt; // type has no wrappers or prims at all 763 wt.wrapAlt = uwt; 764 } 765 return uwt; 766 } 767 768 /** 769 * Returns the parameter type at the specified index, within this method type. 770 * @param num the index (zero-based) of the desired parameter type 771 * @return the selected parameter type 772 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()} 773 */ 774 public Class<?> parameterType(int num) { 775 return ptypes[num]; 776 } 777 /** 778 * Returns the number of parameter types in this method type. 779 * @return the number of parameter types 780 */ 781 public int parameterCount() { 782 return ptypes.length; 783 } 784 /** 785 * Returns the return type of this method type. 786 * @return the return type 787 */ 788 public Class<?> returnType() { 789 return rtype; 790 } 791 792 /** 793 * Presents the parameter types as a list (a convenience method). 794 * The list will be immutable. 795 * @return the parameter types (as an immutable list) 796 */ 797 public List<Class<?>> parameterList() { 798 return Collections.unmodifiableList(Arrays.asList(ptypes.clone())); 799 } 800 801 /** 802 * Returns the last parameter type of this method type. 803 * If this type has no parameters, the sentinel value 804 * {@code void.class} is returned instead. 805 * @apiNote 806 * <p> 807 * The sentinel value is chosen so that reflective queries can be 808 * made directly against the result value. 809 * The sentinel value cannot be confused with a real parameter, 810 * since {@code void} is never acceptable as a parameter type. 811 * For variable arity invocation modes, the expression 812 * {@link Class#getComponentType lastParameterType().getComponentType()} 813 * is useful to query the type of the "varargs" parameter. 814 * @return the last parameter type if any, else {@code void.class} 815 * @since 10 816 */ 817 public Class<?> lastParameterType() { 818 int len = ptypes.length; 819 return len == 0 ? void.class : ptypes[len-1]; 820 } 821 822 /** 823 * Presents the parameter types as an array (a convenience method). 824 * Changes to the array will not result in changes to the type. 825 * @return the parameter types (as a fresh copy if necessary) 826 */ 827 public Class<?>[] parameterArray() { 828 return ptypes.clone(); 829 } 830 831 /** 832 * Compares the specified object with this type for equality. 833 * That is, it returns {@code true} if and only if the specified object 834 * is also a method type with exactly the same parameters and return type. 835 * @param x object to compare 836 * @see Object#equals(Object) 837 */ 838 // This implementation may also return true if x is a WeakEntry containing 839 // a method type that is equal to this. This is an internal implementation 840 // detail to allow for faster method type lookups. 841 // See ConcurrentWeakInternSet.WeakEntry#equals(Object) 842 @Override 843 public boolean equals(Object x) { 844 if (this == x) { 845 return true; 846 } 847 if (x instanceof MethodType) { 848 return equals((MethodType)x); 849 } 850 if (x instanceof ConcurrentWeakInternSet.WeakEntry) { 851 Object o = ((ConcurrentWeakInternSet.WeakEntry)x).get(); 852 if (o instanceof MethodType) { 853 return equals((MethodType)o); 854 } 855 } 856 return false; 857 } 858 859 private boolean equals(MethodType that) { 860 return this.rtype == that.rtype 861 && Arrays.equals(this.ptypes, that.ptypes); 862 } 863 864 /** 865 * Returns the hash code value for this method type. 866 * It is defined to be the same as the hashcode of a List 867 * whose elements are the return type followed by the 868 * parameter types. 869 * @return the hash code value for this method type 870 * @see Object#hashCode() 871 * @see #equals(Object) 872 * @see List#hashCode() 873 */ 874 @Override 875 public int hashCode() { 876 int hashCode = 31 + rtype.hashCode(); 877 for (Class<?> ptype : ptypes) 878 hashCode = 31 * hashCode + ptype.hashCode(); 879 return hashCode; 880 } 881 882 /** 883 * Returns a string representation of the method type, 884 * of the form {@code "(PT0,PT1...)RT"}. 885 * The string representation of a method type is a 886 * parenthesis enclosed, comma separated list of type names, 887 * followed immediately by the return type. 888 * <p> 889 * Each type is represented by its 890 * {@link java.lang.Class#getSimpleName simple name}. 891 */ 892 @Override 893 public String toString() { 894 StringJoiner sj = new StringJoiner(",", "(", 895 ")" + rtype.getSimpleName()); 896 for (int i = 0; i < ptypes.length; i++) { 897 sj.add(ptypes[i].getSimpleName()); 898 } 899 return sj.toString(); 900 } 901 902 /** True if my parameter list is effectively identical to the given full list, 903 * after skipping the given number of my own initial parameters. 904 * In other words, after disregarding {@code skipPos} parameters, 905 * my remaining parameter list is no longer than the {@code fullList}, and 906 * is equal to the same-length initial sublist of {@code fullList}. 907 */ 908 /*non-public*/ 909 boolean effectivelyIdenticalParameters(int skipPos, List<Class<?>> fullList) { 910 int myLen = ptypes.length, fullLen = fullList.size(); 911 if (skipPos > myLen || myLen - skipPos > fullLen) 912 return false; 913 List<Class<?>> myList = Arrays.asList(ptypes); 914 if (skipPos != 0) { 915 myList = myList.subList(skipPos, myLen); 916 myLen -= skipPos; 917 } 918 if (fullLen == myLen) 919 return myList.equals(fullList); 920 else 921 return myList.equals(fullList.subList(0, myLen)); 922 } 923 924 /** True if the old return type can always be viewed (w/o casting) under new return type, 925 * and the new parameters can be viewed (w/o casting) under the old parameter types. 926 */ 927 /*non-public*/ 928 boolean isViewableAs(MethodType newType, boolean keepInterfaces) { 929 if (!VerifyType.isNullConversion(returnType(), newType.returnType(), keepInterfaces)) 930 return false; 931 if (form == newType.form && form.erasedType == this) 932 return true; // my reference parameters are all Object 933 if (ptypes == newType.ptypes) 934 return true; 935 int argc = parameterCount(); 936 if (argc != newType.parameterCount()) 937 return false; 938 for (int i = 0; i < argc; i++) { 939 if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i), keepInterfaces)) 940 return false; 941 } 942 return true; 943 } 944 /*non-public*/ 945 boolean isConvertibleTo(MethodType newType) { 946 MethodTypeForm oldForm = this.form(); 947 MethodTypeForm newForm = newType.form(); 948 if (oldForm == newForm) 949 // same parameter count, same primitive/object mix 950 return true; 951 if (!canConvert(returnType(), newType.returnType())) 952 return false; 953 Class<?>[] srcTypes = newType.ptypes; 954 Class<?>[] dstTypes = ptypes; 955 if (srcTypes == dstTypes) 956 return true; 957 int argc; 958 if ((argc = srcTypes.length) != dstTypes.length) 959 return false; 960 if (argc <= 1) { 961 if (argc == 1 && !canConvert(srcTypes[0], dstTypes[0])) 962 return false; 963 return true; 964 } 965 if ((!oldForm.hasPrimitives() && oldForm.erasedType == this) || 966 (!newForm.hasPrimitives() && newForm.erasedType == newType)) { 967 // Somewhat complicated test to avoid a loop of 2 or more trips. 968 // If either type has only Object parameters, we know we can convert. 969 assert(canConvertParameters(srcTypes, dstTypes)); 970 return true; 971 } 972 return canConvertParameters(srcTypes, dstTypes); 973 } 974 975 /** Returns true if MHs.explicitCastArguments produces the same result as MH.asType. 976 * If the type conversion is impossible for either, the result should be false. 977 */ 978 /*non-public*/ 979 boolean explicitCastEquivalentToAsType(MethodType newType) { 980 if (this == newType) return true; 981 if (!explicitCastEquivalentToAsType(rtype, newType.rtype)) { 982 return false; 983 } 984 Class<?>[] srcTypes = newType.ptypes; 985 Class<?>[] dstTypes = ptypes; 986 if (dstTypes == srcTypes) { 987 return true; 988 } 989 assert(dstTypes.length == srcTypes.length); 990 for (int i = 0; i < dstTypes.length; i++) { 991 if (!explicitCastEquivalentToAsType(srcTypes[i], dstTypes[i])) { 992 return false; 993 } 994 } 995 return true; 996 } 997 998 /** Reports true if the src can be converted to the dst, by both asType and MHs.eCE, 999 * and with the same effect. 1000 * MHs.eCA has the following "upgrades" to MH.asType: 1001 * 1. interfaces are unchecked (that is, treated as if aliased to Object) 1002 * Therefore, {@code Object->CharSequence} is possible in both cases but has different semantics 1003 * 2. the full matrix of primitive-to-primitive conversions is supported 1004 * Narrowing like {@code long->byte} and basic-typing like {@code boolean->int} 1005 * are not supported by asType, but anything supported by asType is equivalent 1006 * with MHs.eCE. 1007 * 3a. unboxing conversions can be followed by the full matrix of primitive conversions 1008 * 3b. unboxing of null is permitted (creates a zero primitive value) 1009 * Other than interfaces, reference-to-reference conversions are the same. 1010 * Boxing primitives to references is the same for both operators. 1011 */ 1012 private static boolean explicitCastEquivalentToAsType(Class<?> src, Class<?> dst) { 1013 if (src == dst || dst == Object.class || dst == void.class) return true; 1014 if (src.isPrimitive()) { 1015 // Could be a prim/prim conversion, where casting is a strict superset. 1016 // Or a boxing conversion, which is always to an exact wrapper class. 1017 return canConvert(src, dst); 1018 } else if (dst.isPrimitive()) { 1019 // Unboxing behavior is different between MHs.eCA & MH.asType (see 3b). 1020 return false; 1021 } else { 1022 // R->R always works, but we have to avoid a check-cast to an interface. 1023 return !dst.isInterface() || dst.isAssignableFrom(src); 1024 } 1025 } 1026 1027 private boolean canConvertParameters(Class<?>[] srcTypes, Class<?>[] dstTypes) { 1028 for (int i = 0; i < srcTypes.length; i++) { 1029 if (!canConvert(srcTypes[i], dstTypes[i])) { 1030 return false; 1031 } 1032 } 1033 return true; 1034 } 1035 1036 /*non-public*/ 1037 static boolean canConvert(Class<?> src, Class<?> dst) { 1038 // short-circuit a few cases: 1039 if (src == dst || src == Object.class || dst == Object.class) return true; 1040 // the remainder of this logic is documented in MethodHandle.asType 1041 if (src.isPrimitive()) { 1042 // can force void to an explicit null, a la reflect.Method.invoke 1043 // can also force void to a primitive zero, by analogy 1044 if (src == void.class) return true; //or !dst.isPrimitive()? 1045 Wrapper sw = Wrapper.forPrimitiveType(src); 1046 if (dst.isPrimitive()) { 1047 // P->P must widen 1048 return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw); 1049 } else { 1050 // P->R must box and widen 1051 return dst.isAssignableFrom(sw.wrapperType()); 1052 } 1053 } else if (dst.isPrimitive()) { 1054 // any value can be dropped 1055 if (dst == void.class) return true; 1056 Wrapper dw = Wrapper.forPrimitiveType(dst); 1057 // R->P must be able to unbox (from a dynamically chosen type) and widen 1058 // For example: 1059 // Byte/Number/Comparable/Object -> dw:Byte -> byte. 1060 // Character/Comparable/Object -> dw:Character -> char 1061 // Boolean/Comparable/Object -> dw:Boolean -> boolean 1062 // This means that dw must be cast-compatible with src. 1063 if (src.isAssignableFrom(dw.wrapperType())) { 1064 return true; 1065 } 1066 // The above does not work if the source reference is strongly typed 1067 // to a wrapper whose primitive must be widened. For example: 1068 // Byte -> unbox:byte -> short/int/long/float/double 1069 // Character -> unbox:char -> int/long/float/double 1070 if (Wrapper.isWrapperType(src) && 1071 dw.isConvertibleFrom(Wrapper.forWrapperType(src))) { 1072 // can unbox from src and then widen to dst 1073 return true; 1074 } 1075 // We have already covered cases which arise due to runtime unboxing 1076 // of a reference type which covers several wrapper types: 1077 // Object -> cast:Integer -> unbox:int -> long/float/double 1078 // Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double 1079 // An marginal case is Number -> dw:Character -> char, which would be OK if there were a 1080 // subclass of Number which wraps a value that can convert to char. 1081 // Since there is none, we don't need an extra check here to cover char or boolean. 1082 return false; 1083 } else { 1084 // R->R always works, since null is always valid dynamically 1085 return true; 1086 } 1087 } 1088 1089 /// Queries which have to do with the bytecode architecture 1090 1091 /** Reports the number of JVM stack slots required to invoke a method 1092 * of this type. Note that (for historical reasons) the JVM requires 1093 * a second stack slot to pass long and double arguments. 1094 * So this method returns {@link #parameterCount() parameterCount} plus the 1095 * number of long and double parameters (if any). 1096 * <p> 1097 * This method is included for the benefit of applications that must 1098 * generate bytecodes that process method handles and invokedynamic. 1099 * @return the number of JVM stack slots for this type's parameters 1100 */ 1101 /*non-public*/ 1102 int parameterSlotCount() { 1103 return form.parameterSlotCount(); 1104 } 1105 1106 /*non-public*/ 1107 Invokers invokers() { 1108 Invokers inv = invokers; 1109 if (inv != null) return inv; 1110 invokers = inv = new Invokers(this); 1111 return inv; 1112 } 1113 1114 /** 1115 * Finds or creates an instance of a method type, given the spelling of its bytecode descriptor. 1116 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}. 1117 * Any class or interface name embedded in the descriptor string will be 1118 * resolved by the given loader (or if it is null, on the system class loader). 1119 * <p> 1120 * Note that it is possible to encounter method types which cannot be 1121 * constructed by this method, because their component types are 1122 * not all reachable from a common class loader. 1123 * <p> 1124 * This method is included for the benefit of applications that must 1125 * generate bytecodes that process method handles and {@code invokedynamic}. 1126 * @param descriptor a bytecode-level type descriptor string "(T...)T" 1127 * @param loader the class loader in which to look up the types 1128 * @return a method type matching the bytecode-level type descriptor 1129 * @throws NullPointerException if the string is null 1130 * @throws IllegalArgumentException if the string is not well-formed 1131 * @throws TypeNotPresentException if a named type cannot be found 1132 * @throws SecurityException if the security manager is present and 1133 * {@code loader} is {@code null} and the caller does not have the 1134 * {@link RuntimePermission}{@code ("getClassLoader")} 1135 */ 1136 public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader) 1137 throws IllegalArgumentException, TypeNotPresentException 1138 { 1139 if (loader == null) { 1140 SecurityManager sm = System.getSecurityManager(); 1141 if (sm != null) { 1142 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION); 1143 } 1144 } 1145 return fromDescriptor(descriptor, 1146 (loader == null) ? ClassLoader.getSystemClassLoader() : loader); 1147 } 1148 1149 /** 1150 * Same as {@link #fromMethodDescriptorString(String, ClassLoader)}, but 1151 * {@code null} ClassLoader means the bootstrap loader is used here. 1152 * <p> 1153 * IMPORTANT: This method is preferable for JDK internal use as it more 1154 * correctly interprets {@code null} ClassLoader than 1155 * {@link #fromMethodDescriptorString(String, ClassLoader)}. 1156 * Use of this method also avoids early initialization issues when system 1157 * ClassLoader is not initialized yet. 1158 */ 1159 static MethodType fromDescriptor(String descriptor, ClassLoader loader) 1160 throws IllegalArgumentException, TypeNotPresentException 1161 { 1162 if (!descriptor.startsWith("(") || // also generates NPE if needed 1163 descriptor.indexOf(')') < 0 || 1164 descriptor.indexOf('.') >= 0) 1165 throw newIllegalArgumentException("not a method descriptor: "+descriptor); 1166 List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader); 1167 Class<?> rtype = types.remove(types.size() - 1); 1168 Class<?>[] ptypes = listToArray(types); 1169 return makeImpl(rtype, ptypes, true); 1170 } 1171 1172 /** 1173 * Returns a descriptor string for the method type. This method 1174 * is equivalent to calling {@link #descriptorString() MethodType::descriptorString}. 1175 * 1176 * <p> 1177 * Note that this is not a strict inverse of {@link #fromMethodDescriptorString fromMethodDescriptorString}. 1178 * Two distinct classes which share a common name but have different class loaders 1179 * will appear identical when viewed within descriptor strings. 1180 * <p> 1181 * This method is included for the benefit of applications that must 1182 * generate bytecodes that process method handles and {@code invokedynamic}. 1183 * {@link #fromMethodDescriptorString(java.lang.String, java.lang.ClassLoader) fromMethodDescriptorString}, 1184 * because the latter requires a suitable class loader argument. 1185 * @return the descriptor string for this method type 1186 * @jvms 4.3.3 Method Descriptors 1187 * @see <a href="#descriptor">Nominal Descriptor for {@code MethodType}</a> 1188 */ 1189 public String toMethodDescriptorString() { 1190 String desc = methodDescriptor; 1191 if (desc == null) { 1192 desc = BytecodeDescriptor.unparseMethod(this.rtype, this.ptypes); 1193 methodDescriptor = desc; 1194 } 1195 return desc; 1196 } 1197 1198 /** 1199 * Returns a descriptor string for this method type. 1200 * 1201 * <p> 1202 * If this method type can be <a href="#descriptor">described nominally</a>, 1203 * then the result is a method type descriptor (JVMS {@jvms 4.3.3}). 1204 * {@link MethodTypeDesc MethodTypeDesc} for this method type 1205 * can be produced by calling {@link MethodTypeDesc#ofDescriptor(String) 1206 * MethodTypeDesc::ofDescriptor} with the result descriptor string. 1207 * <p> 1208 * If this method type cannot be <a href="#descriptor">described nominally</a> 1209 * and the result is a string of the form: 1210 * <blockquote>{@code "(<parameter-descriptors>)<return-descriptor>"}</blockquote> 1211 * where {@code <parameter-descriptors>} is the concatenation of the 1212 * {@linkplain Class#descriptorString() descriptor string} of all 1213 * of the parameter types and the {@linkplain Class#descriptorString() descriptor string} 1214 * of the return type. No {@link java.lang.constant.MethodTypeDesc MethodTypeDesc} 1215 * can be produced from the result string. 1216 * 1217 * @return the descriptor string for this method type 1218 * @since 12 1219 * @jvms 4.3.3 Method Descriptors 1220 * @see <a href="#descriptor">Nominal Descriptor for {@code MethodType}</a> 1221 */ 1222 @Override 1223 public String descriptorString() { 1224 return toMethodDescriptorString(); 1225 } 1226 1227 /*non-public*/ 1228 static String toFieldDescriptorString(Class<?> cls) { 1229 return BytecodeDescriptor.unparse(cls); 1230 } 1231 1232 /** 1233 * Returns a nominal descriptor for this instance, if one can be 1234 * constructed, or an empty {@link Optional} if one cannot be. 1235 * 1236 * @return An {@link Optional} containing the resulting nominal descriptor, 1237 * or an empty {@link Optional} if one cannot be constructed. 1238 * @since 12 1239 * @see <a href="#descriptor">Nominal Descriptor for {@code MethodType}</a> 1240 */ 1241 @Override 1242 public Optional<MethodTypeDesc> describeConstable() { 1243 try { 1244 return Optional.of(MethodTypeDesc.of(returnType().describeConstable().orElseThrow(), 1245 Stream.of(parameterArray()) 1246 .map(p -> p.describeConstable().orElseThrow()) 1247 .toArray(ClassDesc[]::new))); 1248 } 1249 catch (NoSuchElementException e) { 1250 return Optional.empty(); 1251 } 1252 } 1253 1254 /// Serialization. 1255 1256 /** 1257 * There are no serializable fields for {@code MethodType}. 1258 */ 1259 @java.io.Serial 1260 private static final java.io.ObjectStreamField[] serialPersistentFields = { }; 1261 1262 /** 1263 * Save the {@code MethodType} instance to a stream. 1264 * 1265 * @serialData 1266 * For portability, the serialized format does not refer to named fields. 1267 * Instead, the return type and parameter type arrays are written directly 1268 * from the {@code writeObject} method, using two calls to {@code s.writeObject} 1269 * as follows: 1270 * <blockquote><pre>{@code 1271 s.writeObject(this.returnType()); 1272 s.writeObject(this.parameterArray()); 1273 * }</pre></blockquote> 1274 * <p> 1275 * The deserialized field values are checked as if they were 1276 * provided to the factory method {@link #methodType(Class,Class[]) methodType}. 1277 * For example, null values, or {@code void} parameter types, 1278 * will lead to exceptions during deserialization. 1279 * @param s the stream to write the object to 1280 * @throws java.io.IOException if there is a problem writing the object 1281 */ 1282 @java.io.Serial 1283 private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException { 1284 s.defaultWriteObject(); // requires serialPersistentFields to be an empty array 1285 s.writeObject(returnType()); 1286 s.writeObject(parameterArray()); 1287 } 1288 1289 /** 1290 * Reconstitute the {@code MethodType} instance from a stream (that is, 1291 * deserialize it). 1292 * This instance is a scratch object with bogus final fields. 1293 * It provides the parameters to the factory method called by 1294 * {@link #readResolve readResolve}. 1295 * After that call it is discarded. 1296 * @param s the stream to read the object from 1297 * @throws java.io.IOException if there is a problem reading the object 1298 * @throws ClassNotFoundException if one of the component classes cannot be resolved 1299 * @see #readResolve 1300 * @see #writeObject 1301 */ 1302 @java.io.Serial 1303 private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException { 1304 // Assign defaults in case this object escapes 1305 UNSAFE.putReference(this, OffsetHolder.rtypeOffset, void.class); 1306 UNSAFE.putReference(this, OffsetHolder.ptypesOffset, NO_PTYPES); 1307 1308 s.defaultReadObject(); // requires serialPersistentFields to be an empty array 1309 1310 Class<?> returnType = (Class<?>) s.readObject(); 1311 Class<?>[] parameterArray = (Class<?>[]) s.readObject(); 1312 1313 // Verify all operands, and make sure ptypes is unshared 1314 // Cache the new MethodType for readResolve 1315 wrapAlt = new MethodType[]{MethodType.methodType(returnType, parameterArray)}; 1316 } 1317 1318 // Support for resetting final fields while deserializing. Implement Holder 1319 // pattern to make the rarely needed offset calculation lazy. 1320 private static class OffsetHolder { 1321 static final long rtypeOffset 1322 = UNSAFE.objectFieldOffset(MethodType.class, "rtype"); 1323 1324 static final long ptypesOffset 1325 = UNSAFE.objectFieldOffset(MethodType.class, "ptypes"); 1326 } 1327 1328 /** 1329 * Resolves and initializes a {@code MethodType} object 1330 * after serialization. 1331 * @return the fully initialized {@code MethodType} object 1332 */ 1333 @java.io.Serial 1334 private Object readResolve() { 1335 // Do not use a trusted path for deserialization: 1336 // return makeImpl(rtype, ptypes, true); 1337 // Verify all operands, and make sure ptypes is unshared: 1338 // Return a new validated MethodType for the rtype and ptypes passed from readObject. 1339 MethodType mt = ((MethodType[])wrapAlt)[0]; 1340 wrapAlt = null; 1341 return mt; 1342 } 1343 1344 /** 1345 * Simple implementation of weak concurrent intern set. 1346 * 1347 * @param <T> interned type 1348 */ 1349 private static class ConcurrentWeakInternSet<T> { 1350 1351 private final ConcurrentMap<WeakEntry<T>, WeakEntry<T>> map; 1352 private final ReferenceQueue<T> stale; 1353 1354 public ConcurrentWeakInternSet() { 1355 this.map = new ConcurrentHashMap<>(512); 1356 this.stale = new ReferenceQueue<>(); 1357 } 1358 1359 /** 1360 * Get the existing interned element. 1361 * This method returns null if no element is interned. 1362 * 1363 * @param elem element to look up 1364 * @return the interned element 1365 */ 1366 public T get(T elem) { 1367 if (elem == null) throw new NullPointerException(); 1368 expungeStaleElements(); 1369 1370 WeakEntry<T> value = map.get(elem); 1371 if (value != null) { 1372 T res = value.get(); 1373 if (res != null) { 1374 return res; 1375 } 1376 } 1377 return null; 1378 } 1379 1380 /** 1381 * Interns the element. 1382 * Always returns non-null element, matching the one in the intern set. 1383 * Under the race against another add(), it can return <i>different</i> 1384 * element, if another thread beats us to interning it. 1385 * 1386 * @param elem element to add 1387 * @return element that was actually added 1388 */ 1389 public T add(T elem) { 1390 if (elem == null) throw new NullPointerException(); 1391 1392 // Playing double race here, and so spinloop is required. 1393 // First race is with two concurrent updaters. 1394 // Second race is with GC purging weak ref under our feet. 1395 // Hopefully, we almost always end up with a single pass. 1396 T interned; 1397 WeakEntry<T> e = new WeakEntry<>(elem, stale); 1398 do { 1399 expungeStaleElements(); 1400 WeakEntry<T> exist = map.putIfAbsent(e, e); 1401 interned = (exist == null) ? elem : exist.get(); 1402 } while (interned == null); 1403 return interned; 1404 } 1405 1406 private void expungeStaleElements() { 1407 Reference<? extends T> reference; 1408 while ((reference = stale.poll()) != null) { 1409 map.remove(reference); 1410 } 1411 } 1412 1413 private static class WeakEntry<T> extends WeakReference<T> { 1414 1415 public final int hashcode; 1416 1417 public WeakEntry(T key, ReferenceQueue<T> queue) { 1418 super(key, queue); 1419 hashcode = key.hashCode(); 1420 } 1421 1422 /** 1423 * This implementation returns {@code true} if {@code obj} is another 1424 * {@code WeakEntry} whose referent is equal to this referent, or 1425 * if {@code obj} is equal to the referent of this. This allows 1426 * lookups to be made without wrapping in a {@code WeakEntry}. 1427 * 1428 * @param obj the object to compare 1429 * @return true if {@code obj} is equal to this or the referent of this 1430 * @see MethodType#equals(Object) 1431 * @see Object#equals(Object) 1432 */ 1433 @Override 1434 public boolean equals(Object obj) { 1435 Object mine = get(); 1436 if (obj instanceof WeakEntry) { 1437 Object that = ((WeakEntry) obj).get(); 1438 return (that == null || mine == null) ? (this == obj) : mine.equals(that); 1439 } 1440 return (mine == null) ? (obj == null) : mine.equals(obj); 1441 } 1442 1443 @Override 1444 public int hashCode() { 1445 return hashcode; 1446 } 1447 1448 } 1449 } 1450 1451 } 1452