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 * @author John Rose, JSR 292 EG
103 * @since 1.7
104 */
105 public final
106 class MethodType
107 implements Constable,
108 TypeDescriptor.OfMethod<Class<?>, MethodType>,
109 java.io.Serializable {
110 @java.io.Serial
111 private static final long serialVersionUID = 292L; // {rtype, {ptype...}}
112
113 // The rtype and ptypes fields define the structural identity of the method type:
114 private final @Stable Class<?> rtype;
115 private final @Stable Class<?>[] ptypes;
116
117 // The remaining fields are caches of various sorts:
118 private @Stable MethodTypeForm form; // erased form, plus cached data about primitives
119 private @Stable MethodType wrapAlt; // alternative wrapped/unwrapped version
120 private @Stable Invokers invokers; // cache of handy higher-order adapters
121 private @Stable String methodDescriptor; // cache for toMethodDescriptorString
122
123 /**
124 * Constructor that performs no copying or validation.
125 * Should only be called from the factory method makeImpl
126 */
127 private MethodType(Class<?> rtype, Class<?>[] ptypes) {
128 this.rtype = rtype;
129 this.ptypes = ptypes;
130 }
131
132 /*trusted*/ MethodTypeForm form() { return form; }
133 /*trusted*/ Class<?> rtype() { return rtype; }
134 /*trusted*/ Class<?>[] ptypes() { return ptypes; }
135
136 void setForm(MethodTypeForm f) { form = f; }
137
138 /** This number, mandated by the JVM spec as 255,
139 * is the maximum number of <em>slots</em>
140 * that any Java method can receive in its argument list.
141 * It limits both JVM signatures and method type objects.
142 * The longest possible invocation will look like
143 * {@code staticMethod(arg1, arg2, ..., arg255)} or
144 * {@code x.virtualMethod(arg1, arg2, ..., arg254)}.
145 */
146 /*non-public*/
147 static final int MAX_JVM_ARITY = 255; // this is mandated by the JVM spec.
148
149 /** This number is the maximum arity of a method handle, 254.
150 * It is derived from the absolute JVM-imposed arity by subtracting one,
151 * which is the slot occupied by the method handle itself at the
152 * beginning of the argument list used to invoke the method handle.
153 * The longest possible invocation will look like
154 * {@code mh.invoke(arg1, arg2, ..., arg254)}.
155 */
156 // Issue: Should we allow MH.invokeWithArguments to go to the full 255?
157 /*non-public*/
158 static final int MAX_MH_ARITY = MAX_JVM_ARITY-1; // deduct one for mh receiver
159
160 /** This number is the maximum arity of a method handle invoker, 253.
161 * It is derived from the absolute JVM-imposed arity by subtracting two,
162 * which are the slots occupied by invoke method handle, and the
163 * target method handle, which are both at the beginning of the argument
164 * list used to invoke the target method handle.
165 * The longest possible invocation will look like
166 * {@code invokermh.invoke(targetmh, arg1, arg2, ..., arg253)}.
167 */
168 /*non-public*/
169 static final int MAX_MH_INVOKER_ARITY = MAX_MH_ARITY-1; // deduct one more for invoker
170
171 private static void checkRtype(Class<?> rtype) {
172 Objects.requireNonNull(rtype);
173 }
174 private static void checkPtype(Class<?> ptype) {
175 Objects.requireNonNull(ptype);
176 if (ptype == void.class)
177 throw newIllegalArgumentException("parameter type cannot be void");
178 }
179 /** Return number of extra slots (count of long/double args). */
180 private static int checkPtypes(Class<?>[] ptypes) {
181 int slots = 0;
182 for (Class<?> ptype : ptypes) {
183 checkPtype(ptype);
184 if (ptype == double.class || ptype == long.class) {
185 slots++;
186 }
187 }
188 checkSlotCount(ptypes.length + slots);
189 return slots;
190 }
191
192 static {
193 // MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work:
194 assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0);
195 }
196 static void checkSlotCount(int count) {
197 if ((count & MAX_JVM_ARITY) != count)
198 throw newIllegalArgumentException("bad parameter count "+count);
199 }
200 private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) {
201 if (num instanceof Integer) num = "bad index: "+num;
202 return new IndexOutOfBoundsException(num.toString());
203 }
204
205 static final ConcurrentWeakInternSet<MethodType> internTable = new ConcurrentWeakInternSet<>();
206
207 static final Class<?>[] NO_PTYPES = {};
208
209 /**
210 * Finds or creates an instance of the given method type.
211 * @param rtype the return type
212 * @param ptypes the parameter types
213 * @return a method type with the given components
214 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
215 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
216 */
217 public static MethodType methodType(Class<?> rtype, Class<?>[] ptypes) {
218 return makeImpl(rtype, ptypes, false);
219 }
220
221 /**
222 * Finds or creates a method type with the given components.
223 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
224 * @param rtype the return type
225 * @param ptypes the parameter types
226 * @return a method type with the given components
227 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
228 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
229 */
230 public static MethodType methodType(Class<?> rtype, List<Class<?>> ptypes) {
231 boolean notrust = false; // random List impl. could return evil ptypes array
232 return makeImpl(rtype, listToArray(ptypes), notrust);
233 }
234
235 private static Class<?>[] listToArray(List<Class<?>> ptypes) {
236 // sanity check the size before the toArray call, since size might be huge
237 checkSlotCount(ptypes.size());
238 return ptypes.toArray(NO_PTYPES);
239 }
240
241 /**
242 * Finds or creates a method type with the given components.
243 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
244 * The leading parameter type is prepended to the remaining array.
245 * @param rtype the return type
246 * @param ptype0 the first parameter type
247 * @param ptypes the remaining parameter types
248 * @return a method type with the given components
249 * @throws NullPointerException if {@code rtype} or {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is null
250 * @throws IllegalArgumentException if {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is {@code void.class}
251 */
252 public static MethodType methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes) {
253 Class<?>[] ptypes1 = new Class<?>[1+ptypes.length];
254 ptypes1[0] = ptype0;
255 System.arraycopy(ptypes, 0, ptypes1, 1, ptypes.length);
256 return makeImpl(rtype, ptypes1, true);
257 }
258
259 /**
260 * Finds or creates a method type with the given components.
261 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
262 * The resulting method has no parameter types.
263 * @param rtype the return type
264 * @return a method type with the given return value
265 * @throws NullPointerException if {@code rtype} is null
266 */
267 public static MethodType methodType(Class<?> rtype) {
268 return makeImpl(rtype, NO_PTYPES, true);
269 }
270
271 /**
272 * Finds or creates a method type with the given components.
273 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
274 * The resulting method has the single given parameter type.
275 * @param rtype the return type
276 * @param ptype0 the parameter type
277 * @return a method type with the given return value and parameter type
278 * @throws NullPointerException if {@code rtype} or {@code ptype0} is null
279 * @throws IllegalArgumentException if {@code ptype0} is {@code void.class}
280 */
281 public static MethodType methodType(Class<?> rtype, Class<?> ptype0) {
282 return makeImpl(rtype, new Class<?>[]{ ptype0 }, true);
283 }
284
285 /**
286 * Finds or creates a method type with the given components.
287 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
288 * The resulting method has the same parameter types as {@code ptypes},
289 * and the specified return type.
290 * @param rtype the return type
291 * @param ptypes the method type which supplies the parameter types
292 * @return a method type with the given components
293 * @throws NullPointerException if {@code rtype} or {@code ptypes} is null
294 */
295 public static MethodType methodType(Class<?> rtype, MethodType ptypes) {
296 return makeImpl(rtype, ptypes.ptypes, true);
297 }
298
299 /**
300 * Sole factory method to find or create an interned method type.
301 * @param rtype desired return type
302 * @param ptypes desired parameter types
303 * @param trusted whether the ptypes can be used without cloning
304 * @return the unique method type of the desired structure
305 */
306 /*trusted*/
307 static MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {
308 if (ptypes.length == 0) {
309 ptypes = NO_PTYPES; trusted = true;
310 }
311 MethodType primordialMT = new MethodType(rtype, ptypes);
312 MethodType mt = internTable.get(primordialMT);
313 if (mt != null)
314 return mt;
315
316 // promote the object to the Real Thing, and reprobe
317 MethodType.checkRtype(rtype);
318 if (trusted) {
319 MethodType.checkPtypes(ptypes);
320 mt = primordialMT;
321 } else {
322 // Make defensive copy then validate
323 ptypes = Arrays.copyOf(ptypes, ptypes.length);
324 MethodType.checkPtypes(ptypes);
325 mt = new MethodType(rtype, ptypes);
326 }
327 mt.form = MethodTypeForm.findForm(mt);
328 return internTable.add(mt);
329 }
330 private static final @Stable MethodType[] objectOnlyTypes = new MethodType[20];
331
332 /**
333 * Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array.
334 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
335 * All parameters and the return type will be {@code Object},
336 * except the final array parameter if any, which will be {@code Object[]}.
337 * @param objectArgCount number of parameters (excluding the final array parameter if any)
338 * @param finalArray whether there will be a trailing array parameter, of type {@code Object[]}
339 * @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments
340 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true)
341 * @see #genericMethodType(int)
342 */
343 public static MethodType genericMethodType(int objectArgCount, boolean finalArray) {
344 MethodType mt;
345 checkSlotCount(objectArgCount);
346 int ivarargs = (!finalArray ? 0 : 1);
347 int ootIndex = objectArgCount*2 + ivarargs;
348 if (ootIndex < objectOnlyTypes.length) {
349 mt = objectOnlyTypes[ootIndex];
350 if (mt != null) return mt;
351 }
352 Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs];
353 Arrays.fill(ptypes, Object.class);
354 if (ivarargs != 0) ptypes[objectArgCount] = Object[].class;
355 mt = makeImpl(Object.class, ptypes, true);
356 if (ootIndex < objectOnlyTypes.length) {
357 objectOnlyTypes[ootIndex] = mt; // cache it here also!
358 }
359 return mt;
360 }
361
362 /**
363 * Finds or creates a method type whose components are all {@code Object}.
364 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
365 * All parameters and the return type will be Object.
366 * @param objectArgCount number of parameters
367 * @return a generally applicable method type, for all calls of the given argument count
368 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255
369 * @see #genericMethodType(int, boolean)
370 */
371 public static MethodType genericMethodType(int objectArgCount) {
372 return genericMethodType(objectArgCount, false);
373 }
374
375 /**
376 * Finds or creates a method type with a single different parameter type.
377 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
378 * @param num the index (zero-based) of the parameter type to change
379 * @param nptype a new parameter type to replace the old one with
380 * @return the same type, except with the selected parameter changed
381 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
382 * @throws IllegalArgumentException if {@code nptype} is {@code void.class}
383 * @throws NullPointerException if {@code nptype} is null
384 */
385 public MethodType changeParameterType(int num, Class<?> nptype) {
386 if (parameterType(num) == nptype) return this;
387 checkPtype(nptype);
388 Class<?>[] nptypes = ptypes.clone();
389 nptypes[num] = nptype;
390 return makeImpl(rtype, nptypes, true);
391 }
392
393 /**
394 * Finds or creates a method type with additional parameter types.
395 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
396 * @param num the position (zero-based) of the inserted parameter type(s)
397 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
398 * @return the same type, except with the selected parameter(s) inserted
399 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
400 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
401 * or if the resulting method type would have more than 255 parameter slots
402 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
403 */
404 public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) {
405 int len = ptypes.length;
406 if (num < 0 || num > len)
407 throw newIndexOutOfBoundsException(num);
408 int ins = checkPtypes(ptypesToInsert);
409 checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins);
410 int ilen = ptypesToInsert.length;
411 if (ilen == 0) return this;
412 Class<?>[] nptypes = new Class<?>[len + ilen];
413 if (num > 0) {
414 System.arraycopy(ptypes, 0, nptypes, 0, num);
415 }
416 System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen);
417 if (num < len) {
418 System.arraycopy(ptypes, num, nptypes, num+ilen, len-num);
419 }
420 return makeImpl(rtype, nptypes, true);
421 }
422
423 /**
424 * Finds or creates a method type with additional parameter types.
425 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
426 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
427 * @return the same type, except with the selected parameter(s) appended
428 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
429 * or if the resulting method type would have more than 255 parameter slots
430 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
431 */
432 public MethodType appendParameterTypes(Class<?>... ptypesToInsert) {
433 return insertParameterTypes(parameterCount(), ptypesToInsert);
434 }
435
436 /**
437 * Finds or creates a method type with additional parameter types.
438 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
439 * @param num the position (zero-based) of the inserted parameter type(s)
440 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
441 * @return the same type, except with the selected parameter(s) inserted
442 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
443 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
444 * or if the resulting method type would have more than 255 parameter slots
445 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
446 */
447 public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) {
448 return insertParameterTypes(num, listToArray(ptypesToInsert));
449 }
450
451 /**
452 * Finds or creates a method type with additional parameter types.
453 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
454 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
455 * @return the same type, except with the selected parameter(s) appended
456 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
457 * or if the resulting method type would have more than 255 parameter slots
458 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
459 */
460 public MethodType appendParameterTypes(List<Class<?>> ptypesToInsert) {
461 return insertParameterTypes(parameterCount(), ptypesToInsert);
462 }
463
464 /**
465 * Finds or creates a method type with modified parameter types.
466 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
467 * @param start the position (zero-based) of the first replaced parameter type(s)
468 * @param end the position (zero-based) after the last replaced parameter type(s)
469 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
470 * @return the same type, except with the selected parameter(s) replaced
471 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
472 * or if {@code end} is negative or greater than {@code parameterCount()}
473 * or if {@code start} is greater than {@code end}
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 */
478 /*non-public*/
479 MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) {
480 if (start == end)
481 return insertParameterTypes(start, ptypesToInsert);
482 int len = ptypes.length;
483 if (!(0 <= start && start <= end && end <= len))
484 throw newIndexOutOfBoundsException("start="+start+" end="+end);
485 int ilen = ptypesToInsert.length;
486 if (ilen == 0)
487 return dropParameterTypes(start, end);
488 return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert);
489 }
490
491 /** Replace the last arrayLength parameter types with the component type of arrayType.
492 * @param arrayType any array type
493 * @param pos position at which to spread
494 * @param arrayLength the number of parameter types to change
495 * @return the resulting type
496 */
497 /*non-public*/
498 MethodType asSpreaderType(Class<?> arrayType, int pos, int arrayLength) {
499 assert(parameterCount() >= arrayLength);
500 int spreadPos = pos;
501 if (arrayLength == 0) return this; // nothing to change
502 if (arrayType == Object[].class) {
503 if (isGeneric()) return this; // nothing to change
504 if (spreadPos == 0) {
505 // no leading arguments to preserve; go generic
506 MethodType res = genericMethodType(arrayLength);
507 if (rtype != Object.class) {
508 res = res.changeReturnType(rtype);
509 }
510 return res;
511 }
512 }
513 Class<?> elemType = arrayType.getComponentType();
514 assert(elemType != null);
515 for (int i = spreadPos; i < spreadPos + arrayLength; i++) {
516 if (ptypes[i] != elemType) {
517 Class<?>[] fixedPtypes = ptypes.clone();
518 Arrays.fill(fixedPtypes, i, spreadPos + arrayLength, elemType);
519 return methodType(rtype, fixedPtypes);
520 }
521 }
522 return this; // arguments check out; no change
523 }
524
525 /** Return the leading parameter type, which must exist and be a reference.
526 * @return the leading parameter type, after error checks
527 */
528 /*non-public*/
529 Class<?> leadingReferenceParameter() {
530 Class<?> ptype;
531 if (ptypes.length == 0 ||
532 (ptype = ptypes[0]).isPrimitive())
533 throw newIllegalArgumentException("no leading reference parameter");
534 return ptype;
535 }
536
537 /** Delete the last parameter type and replace it with arrayLength copies of the component type of arrayType.
538 * @param arrayType any array type
539 * @param pos position at which to insert parameters
540 * @param arrayLength the number of parameter types to insert
541 * @return the resulting type
542 */
543 /*non-public*/
544 MethodType asCollectorType(Class<?> arrayType, int pos, int arrayLength) {
545 assert(parameterCount() >= 1);
546 assert(pos < ptypes.length);
547 assert(ptypes[pos].isAssignableFrom(arrayType));
548 MethodType res;
549 if (arrayType == Object[].class) {
550 res = genericMethodType(arrayLength);
551 if (rtype != Object.class) {
552 res = res.changeReturnType(rtype);
553 }
554 } else {
555 Class<?> elemType = arrayType.getComponentType();
556 assert(elemType != null);
557 res = methodType(rtype, Collections.nCopies(arrayLength, elemType));
558 }
559 if (ptypes.length == 1) {
560 return res;
561 } else {
562 // insert after (if need be), then before
563 if (pos < ptypes.length - 1) {
564 res = res.insertParameterTypes(arrayLength, Arrays.copyOfRange(ptypes, pos + 1, ptypes.length));
565 }
566 return res.insertParameterTypes(0, Arrays.copyOf(ptypes, pos));
567 }
568 }
569
570 /**
571 * Finds or creates a method type with some parameter types omitted.
572 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
573 * @param start the index (zero-based) of the first parameter type to remove
574 * @param end the index (greater than {@code start}) of the first parameter type after not to remove
575 * @return the same type, except with the selected parameter(s) removed
576 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
577 * or if {@code end} is negative or greater than {@code parameterCount()}
578 * or if {@code start} is greater than {@code end}
579 */
580 public MethodType dropParameterTypes(int start, int end) {
581 int len = ptypes.length;
582 if (!(0 <= start && start <= end && end <= len))
583 throw newIndexOutOfBoundsException("start="+start+" end="+end);
584 if (start == end) return this;
585 Class<?>[] nptypes;
586 if (start == 0) {
587 if (end == len) {
588 // drop all parameters
589 nptypes = NO_PTYPES;
590 } else {
591 // drop initial parameter(s)
592 nptypes = Arrays.copyOfRange(ptypes, end, len);
593 }
594 } else {
595 if (end == len) {
596 // drop trailing parameter(s)
597 nptypes = Arrays.copyOfRange(ptypes, 0, start);
598 } else {
599 int tail = len - end;
600 nptypes = Arrays.copyOfRange(ptypes, 0, start + tail);
601 System.arraycopy(ptypes, end, nptypes, start, tail);
602 }
603 }
604 return makeImpl(rtype, nptypes, true);
605 }
606
607 /**
608 * Finds or creates a method type with a different return type.
609 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
610 * @param nrtype a return parameter type to replace the old one with
611 * @return the same type, except with the return type change
612 * @throws NullPointerException if {@code nrtype} is null
613 */
614 public MethodType changeReturnType(Class<?> nrtype) {
615 if (returnType() == nrtype) return this;
616 return makeImpl(nrtype, ptypes, true);
617 }
618
619 /**
620 * Reports if this type contains a primitive argument or return value.
621 * The return type {@code void} counts as a primitive.
622 * @return true if any of the types are primitives
623 */
624 public boolean hasPrimitives() {
625 return form.hasPrimitives();
626 }
627
628 /**
629 * Reports if this type contains a wrapper argument or return value.
630 * Wrappers are types which box primitive values, such as {@link Integer}.
631 * The reference type {@code java.lang.Void} counts as a wrapper,
632 * if it occurs as a return type.
633 * @return true if any of the types are wrappers
634 */
635 public boolean hasWrappers() {
636 return unwrap() != this;
637 }
638
639 /**
640 * Erases all reference types to {@code Object}.
641 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
642 * All primitive types (including {@code void}) will remain unchanged.
643 * @return a version of the original type with all reference types replaced
644 */
645 public MethodType erase() {
646 return form.erasedType();
647 }
648
649 /**
650 * Erases all reference types to {@code Object}, and all subword types to {@code int}.
651 * This is the reduced type polymorphism used by private methods
652 * such as {@link MethodHandle#invokeBasic invokeBasic}.
653 * @return a version of the original type with all reference and subword types replaced
654 */
655 /*non-public*/
656 MethodType basicType() {
657 return form.basicType();
658 }
659
660 private static final @Stable Class<?>[] METHOD_HANDLE_ARRAY
661 = new Class<?>[] { MethodHandle.class };
662
663 /**
664 * @return a version of the original type with MethodHandle prepended as the first argument
665 */
666 /*non-public*/
667 MethodType invokerType() {
668 return insertParameterTypes(0, METHOD_HANDLE_ARRAY);
669 }
670
671 /**
672 * Converts all types, both reference and primitive, to {@code Object}.
673 * Convenience method for {@link #genericMethodType(int) genericMethodType}.
674 * The expression {@code type.wrap().erase()} produces the same value
675 * as {@code type.generic()}.
676 * @return a version of the original type with all types replaced
677 */
678 public MethodType generic() {
679 return genericMethodType(parameterCount());
680 }
681
682 /*non-public*/
683 boolean isGeneric() {
684 return this == erase() && !hasPrimitives();
685 }
686
687 /**
688 * Converts all primitive types to their corresponding wrapper types.
689 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
690 * All reference types (including wrapper types) will remain unchanged.
691 * A {@code void} return type is changed to the type {@code java.lang.Void}.
692 * The expression {@code type.wrap().erase()} produces the same value
693 * as {@code type.generic()}.
694 * @return a version of the original type with all primitive types replaced
695 */
696 public MethodType wrap() {
697 return hasPrimitives() ? wrapWithPrims(this) : this;
698 }
699
700 /**
701 * Converts all wrapper types to their corresponding primitive types.
702 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
703 * All primitive types (including {@code void}) will remain unchanged.
704 * A return type of {@code java.lang.Void} is changed to {@code void}.
705 * @return a version of the original type with all wrapper types replaced
706 */
707 public MethodType unwrap() {
708 MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this);
709 return unwrapWithNoPrims(noprims);
710 }
711
712 private static MethodType wrapWithPrims(MethodType pt) {
713 assert(pt.hasPrimitives());
714 MethodType wt = pt.wrapAlt;
715 if (wt == null) {
716 // fill in lazily
717 wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP, MethodTypeForm.WRAP);
718 assert(wt != null);
719 pt.wrapAlt = wt;
720 }
721 return wt;
722 }
723
724 private static MethodType unwrapWithNoPrims(MethodType wt) {
725 assert(!wt.hasPrimitives());
726 MethodType uwt = wt.wrapAlt;
727 if (uwt == null) {
728 // fill in lazily
729 uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP, MethodTypeForm.UNWRAP);
730 if (uwt == null)
731 uwt = wt; // type has no wrappers or prims at all
732 wt.wrapAlt = uwt;
733 }
734 return uwt;
735 }
736
737 /**
738 * Returns the parameter type at the specified index, within this method type.
739 * @param num the index (zero-based) of the desired parameter type
740 * @return the selected parameter type
741 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
742 */
743 public Class<?> parameterType(int num) {
744 return ptypes[num];
745 }
746 /**
747 * Returns the number of parameter types in this method type.
748 * @return the number of parameter types
749 */
750 public int parameterCount() {
751 return ptypes.length;
752 }
753 /**
754 * Returns the return type of this method type.
755 * @return the return type
756 */
757 public Class<?> returnType() {
758 return rtype;
759 }
760
761 /**
762 * Presents the parameter types as a list (a convenience method).
763 * The list will be immutable.
764 * @return the parameter types (as an immutable list)
765 */
766 public List<Class<?>> parameterList() {
767 return Collections.unmodifiableList(Arrays.asList(ptypes.clone()));
768 }
769
770 /**
771 * Returns the last parameter type of this method type.
772 * If this type has no parameters, the sentinel value
773 * {@code void.class} is returned instead.
774 * @apiNote
775 * <p>
776 * The sentinel value is chosen so that reflective queries can be
777 * made directly against the result value.
778 * The sentinel value cannot be confused with a real parameter,
779 * since {@code void} is never acceptable as a parameter type.
780 * For variable arity invocation modes, the expression
781 * {@link Class#getComponentType lastParameterType().getComponentType()}
782 * is useful to query the type of the "varargs" parameter.
783 * @return the last parameter type if any, else {@code void.class}
784 * @since 10
785 */
786 public Class<?> lastParameterType() {
787 int len = ptypes.length;
788 return len == 0 ? void.class : ptypes[len-1];
789 }
790
791 /**
792 * Presents the parameter types as an array (a convenience method).
793 * Changes to the array will not result in changes to the type.
794 * @return the parameter types (as a fresh copy if necessary)
795 */
796 public Class<?>[] parameterArray() {
797 return ptypes.clone();
798 }
799
800 /**
801 * Compares the specified object with this type for equality.
802 * That is, it returns {@code true} if and only if the specified object
803 * is also a method type with exactly the same parameters and return type.
804 * @param x object to compare
805 * @see Object#equals(Object)
806 */
807 // This implementation may also return true if x is a WeakEntry containing
808 // a method type that is equal to this. This is an internal implementation
809 // detail to allow for faster method type lookups.
810 // See ConcurrentWeakInternSet.WeakEntry#equals(Object)
811 @Override
812 public boolean equals(Object x) {
813 if (this == x) {
814 return true;
815 }
816 if (x instanceof MethodType) {
817 return equals((MethodType)x);
818 }
819 if (x instanceof ConcurrentWeakInternSet.WeakEntry) {
820 Object o = ((ConcurrentWeakInternSet.WeakEntry)x).get();
821 if (o instanceof MethodType) {
822 return equals((MethodType)o);
823 }
824 }
825 return false;
826 }
827
828 private boolean equals(MethodType that) {
829 return this.rtype == that.rtype
830 && Arrays.equals(this.ptypes, that.ptypes);
831 }
832
833 /**
834 * Returns the hash code value for this method type.
835 * It is defined to be the same as the hashcode of a List
836 * whose elements are the return type followed by the
837 * parameter types.
838 * @return the hash code value for this method type
839 * @see Object#hashCode()
840 * @see #equals(Object)
841 * @see List#hashCode()
842 */
843 @Override
844 public int hashCode() {
845 int hashCode = 31 + rtype.hashCode();
846 for (Class<?> ptype : ptypes)
847 hashCode = 31 * hashCode + ptype.hashCode();
848 return hashCode;
849 }
850
851 /**
852 * Returns a string representation of the method type,
853 * of the form {@code "(PT0,PT1...)RT"}.
854 * The string representation of a method type is a
855 * parenthesis enclosed, comma separated list of type names,
856 * followed immediately by the return type.
857 * <p>
858 * Each type is represented by its
859 * {@link java.lang.Class#getSimpleName simple name}.
860 */
861 @Override
862 public String toString() {
863 StringJoiner sj = new StringJoiner(",", "(",
864 ")" + rtype.getSimpleName());
865 for (int i = 0; i < ptypes.length; i++) {
866 sj.add(ptypes[i].getSimpleName());
867 }
868 return sj.toString();
869 }
870
871 /** True if my parameter list is effectively identical to the given full list,
872 * after skipping the given number of my own initial parameters.
873 * In other words, after disregarding {@code skipPos} parameters,
874 * my remaining parameter list is no longer than the {@code fullList}, and
875 * is equal to the same-length initial sublist of {@code fullList}.
876 */
877 /*non-public*/
878 boolean effectivelyIdenticalParameters(int skipPos, List<Class<?>> fullList) {
879 int myLen = ptypes.length, fullLen = fullList.size();
880 if (skipPos > myLen || myLen - skipPos > fullLen)
881 return false;
882 List<Class<?>> myList = Arrays.asList(ptypes);
883 if (skipPos != 0) {
884 myList = myList.subList(skipPos, myLen);
885 myLen -= skipPos;
886 }
887 if (fullLen == myLen)
888 return myList.equals(fullList);
889 else
890 return myList.equals(fullList.subList(0, myLen));
891 }
892
893 /** True if the old return type can always be viewed (w/o casting) under new return type,
894 * and the new parameters can be viewed (w/o casting) under the old parameter types.
895 */
896 /*non-public*/
897 boolean isViewableAs(MethodType newType, boolean keepInterfaces) {
898 if (!VerifyType.isNullConversion(returnType(), newType.returnType(), keepInterfaces))
899 return false;
900 if (form == newType.form && form.erasedType == this)
901 return true; // my reference parameters are all Object
902 if (ptypes == newType.ptypes)
903 return true;
904 int argc = parameterCount();
905 if (argc != newType.parameterCount())
906 return false;
907 for (int i = 0; i < argc; i++) {
908 if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i), keepInterfaces))
909 return false;
910 }
911 return true;
912 }
913 /*non-public*/
914 boolean isConvertibleTo(MethodType newType) {
915 MethodTypeForm oldForm = this.form();
916 MethodTypeForm newForm = newType.form();
917 if (oldForm == newForm)
918 // same parameter count, same primitive/object mix
919 return true;
920 if (!canConvert(returnType(), newType.returnType()))
921 return false;
922 Class<?>[] srcTypes = newType.ptypes;
923 Class<?>[] dstTypes = ptypes;
924 if (srcTypes == dstTypes)
925 return true;
926 int argc;
927 if ((argc = srcTypes.length) != dstTypes.length)
928 return false;
929 if (argc <= 1) {
930 if (argc == 1 && !canConvert(srcTypes[0], dstTypes[0]))
931 return false;
932 return true;
933 }
934 if ((!oldForm.hasPrimitives() && oldForm.erasedType == this) ||
935 (!newForm.hasPrimitives() && newForm.erasedType == newType)) {
936 // Somewhat complicated test to avoid a loop of 2 or more trips.
937 // If either type has only Object parameters, we know we can convert.
938 assert(canConvertParameters(srcTypes, dstTypes));
939 return true;
940 }
941 return canConvertParameters(srcTypes, dstTypes);
942 }
943
944 /** Returns true if MHs.explicitCastArguments produces the same result as MH.asType.
945 * If the type conversion is impossible for either, the result should be false.
946 */
947 /*non-public*/
948 boolean explicitCastEquivalentToAsType(MethodType newType) {
949 if (this == newType) return true;
950 if (!explicitCastEquivalentToAsType(rtype, newType.rtype)) {
951 return false;
952 }
953 Class<?>[] srcTypes = newType.ptypes;
954 Class<?>[] dstTypes = ptypes;
955 if (dstTypes == srcTypes) {
956 return true;
957 }
958 assert(dstTypes.length == srcTypes.length);
959 for (int i = 0; i < dstTypes.length; i++) {
960 if (!explicitCastEquivalentToAsType(srcTypes[i], dstTypes[i])) {
961 return false;
962 }
963 }
964 return true;
965 }
966
967 /** Reports true if the src can be converted to the dst, by both asType and MHs.eCE,
968 * and with the same effect.
969 * MHs.eCA has the following "upgrades" to MH.asType:
970 * 1. interfaces are unchecked (that is, treated as if aliased to Object)
971 * Therefore, {@code Object->CharSequence} is possible in both cases but has different semantics
972 * 2. the full matrix of primitive-to-primitive conversions is supported
973 * Narrowing like {@code long->byte} and basic-typing like {@code boolean->int}
974 * are not supported by asType, but anything supported by asType is equivalent
975 * with MHs.eCE.
976 * 3a. unboxing conversions can be followed by the full matrix of primitive conversions
977 * 3b. unboxing of null is permitted (creates a zero primitive value)
978 * Other than interfaces, reference-to-reference conversions are the same.
979 * Boxing primitives to references is the same for both operators.
980 */
981 private static boolean explicitCastEquivalentToAsType(Class<?> src, Class<?> dst) {
982 if (src == dst || dst == Object.class || dst == void.class) return true;
983 if (src.isPrimitive()) {
984 // Could be a prim/prim conversion, where casting is a strict superset.
985 // Or a boxing conversion, which is always to an exact wrapper class.
986 return canConvert(src, dst);
987 } else if (dst.isPrimitive()) {
988 // Unboxing behavior is different between MHs.eCA & MH.asType (see 3b).
989 return false;
990 } else {
991 // R->R always works, but we have to avoid a check-cast to an interface.
992 return !dst.isInterface() || dst.isAssignableFrom(src);
993 }
994 }
995
996 private boolean canConvertParameters(Class<?>[] srcTypes, Class<?>[] dstTypes) {
997 for (int i = 0; i < srcTypes.length; i++) {
998 if (!canConvert(srcTypes[i], dstTypes[i])) {
999 return false;
1000 }
1001 }
1002 return true;
1003 }
1004
1005 /*non-public*/
1006 static boolean canConvert(Class<?> src, Class<?> dst) {
1007 // short-circuit a few cases:
1008 if (src == dst || src == Object.class || dst == Object.class) return true;
1009 // the remainder of this logic is documented in MethodHandle.asType
1010 if (src.isPrimitive()) {
1011 // can force void to an explicit null, a la reflect.Method.invoke
1012 // can also force void to a primitive zero, by analogy
1013 if (src == void.class) return true; //or !dst.isPrimitive()?
1014 Wrapper sw = Wrapper.forPrimitiveType(src);
1015 if (dst.isPrimitive()) {
1016 // P->P must widen
1017 return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw);
1018 } else {
1019 // P->R must box and widen
1020 return dst.isAssignableFrom(sw.wrapperType());
1021 }
1022 } else if (dst.isPrimitive()) {
1023 // any value can be dropped
1024 if (dst == void.class) return true;
1025 Wrapper dw = Wrapper.forPrimitiveType(dst);
1026 // R->P must be able to unbox (from a dynamically chosen type) and widen
1027 // For example:
1028 // Byte/Number/Comparable/Object -> dw:Byte -> byte.
1029 // Character/Comparable/Object -> dw:Character -> char
1030 // Boolean/Comparable/Object -> dw:Boolean -> boolean
1031 // This means that dw must be cast-compatible with src.
1032 if (src.isAssignableFrom(dw.wrapperType())) {
1033 return true;
1034 }
1035 // The above does not work if the source reference is strongly typed
1036 // to a wrapper whose primitive must be widened. For example:
1037 // Byte -> unbox:byte -> short/int/long/float/double
1038 // Character -> unbox:char -> int/long/float/double
1039 if (Wrapper.isWrapperType(src) &&
1040 dw.isConvertibleFrom(Wrapper.forWrapperType(src))) {
1041 // can unbox from src and then widen to dst
1042 return true;
1043 }
1044 // We have already covered cases which arise due to runtime unboxing
1045 // of a reference type which covers several wrapper types:
1046 // Object -> cast:Integer -> unbox:int -> long/float/double
1047 // Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double
1048 // An marginal case is Number -> dw:Character -> char, which would be OK if there were a
1049 // subclass of Number which wraps a value that can convert to char.
1050 // Since there is none, we don't need an extra check here to cover char or boolean.
1051 return false;
1052 } else {
1053 // R->R always works, since null is always valid dynamically
1054 return true;
1055 }
1056 }
1057
1058 /// Queries which have to do with the bytecode architecture
1059
1060 /** Reports the number of JVM stack slots required to invoke a method
1061 * of this type. Note that (for historical reasons) the JVM requires
1062 * a second stack slot to pass long and double arguments.
1063 * So this method returns {@link #parameterCount() parameterCount} plus the
1064 * number of long and double parameters (if any).
1065 * <p>
1066 * This method is included for the benefit of applications that must
1067 * generate bytecodes that process method handles and invokedynamic.
1068 * @return the number of JVM stack slots for this type's parameters
1069 */
1070 /*non-public*/
1071 int parameterSlotCount() {
1072 return form.parameterSlotCount();
1073 }
1074
1075 /*non-public*/
1076 Invokers invokers() {
1077 Invokers inv = invokers;
1078 if (inv != null) return inv;
1079 invokers = inv = new Invokers(this);
1080 return inv;
1081 }
1082
1083 /**
1084 * Finds or creates an instance of a method type, given the spelling of its bytecode descriptor.
1085 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
1086 * Any class or interface name embedded in the descriptor string will be
1087 * resolved by the given loader (or if it is null, on the system class loader).
1088 * <p>
1089 * Note that it is possible to encounter method types which cannot be
1090 * constructed by this method, because their component types are
1091 * not all reachable from a common class loader.
1092 * <p>
1093 * This method is included for the benefit of applications that must
1094 * generate bytecodes that process method handles and {@code invokedynamic}.
1095 * @param descriptor a bytecode-level type descriptor string "(T...)T"
1096 * @param loader the class loader in which to look up the types
1097 * @return a method type matching the bytecode-level type descriptor
1098 * @throws NullPointerException if the string is null
1099 * @throws IllegalArgumentException if the string is not well-formed
1100 * @throws TypeNotPresentException if a named type cannot be found
1101 * @throws SecurityException if the security manager is present and
1102 * {@code loader} is {@code null} and the caller does not have the
1103 * {@link RuntimePermission}{@code ("getClassLoader")}
1104 */
1105 public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader)
1106 throws IllegalArgumentException, TypeNotPresentException
1107 {
1108 if (loader == null) {
1109 SecurityManager sm = System.getSecurityManager();
1110 if (sm != null) {
1111 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
1112 }
1113 }
1114 return fromDescriptor(descriptor,
1115 (loader == null) ? ClassLoader.getSystemClassLoader() : loader);
1116 }
1117
1118 /**
1119 * Same as {@link #fromMethodDescriptorString(String, ClassLoader)}, but
1120 * {@code null} ClassLoader means the bootstrap loader is used here.
1121 * <p>
1122 * IMPORTANT: This method is preferable for JDK internal use as it more
1123 * correctly interprets {@code null} ClassLoader than
1124 * {@link #fromMethodDescriptorString(String, ClassLoader)}.
1125 * Use of this method also avoids early initialization issues when system
1126 * ClassLoader is not initialized yet.
1127 */
1128 static MethodType fromDescriptor(String descriptor, ClassLoader loader)
1129 throws IllegalArgumentException, TypeNotPresentException
1130 {
1131 if (!descriptor.startsWith("(") || // also generates NPE if needed
1132 descriptor.indexOf(')') < 0 ||
1133 descriptor.indexOf('.') >= 0)
1134 throw newIllegalArgumentException("not a method descriptor: "+descriptor);
1135 List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader);
1136 Class<?> rtype = types.remove(types.size() - 1);
1137 Class<?>[] ptypes = listToArray(types);
1138 return makeImpl(rtype, ptypes, true);
1139 }
1140
1141 /**
1142 * Produces a bytecode descriptor representation of the method type.
1143 * <p>
1144 * Note that this is not a strict inverse of {@link #fromMethodDescriptorString fromMethodDescriptorString}.
1145 * Two distinct classes which share a common name but have different class loaders
1146 * will appear identical when viewed within descriptor strings.
1147 * <p>
1148 * This method is included for the benefit of applications that must
1149 * generate bytecodes that process method handles and {@code invokedynamic}.
1150 * {@link #fromMethodDescriptorString(java.lang.String, java.lang.ClassLoader) fromMethodDescriptorString},
1151 * because the latter requires a suitable class loader argument.
1152 * @return the bytecode type descriptor representation
1153 */
1154 public String toMethodDescriptorString() {
1155 String desc = methodDescriptor;
1156 if (desc == null) {
1157 desc = BytecodeDescriptor.unparseMethod(this.rtype, this.ptypes);
1158 methodDescriptor = desc;
1159 }
1160 return desc;
1161 }
1162
1163 /**
1164 * Return a field type descriptor string for this type
1165 *
1166 * @return the descriptor string
1167 * @jvms 4.3.2 Field Descriptors
1168 * @since 12
1169 */
1170 @Override
1171 public String descriptorString() {
1172 return toMethodDescriptorString();
1173 }
1174
1175 /*non-public*/
1176 static String toFieldDescriptorString(Class<?> cls) {
1177 return BytecodeDescriptor.unparse(cls);
1178 }
1179
1180 /**
1181 * Return a nominal descriptor for this instance, if one can be
1182 * constructed, or an empty {@link Optional} if one cannot be.
1183 *
1184 * @return An {@link Optional} containing the resulting nominal descriptor,
1185 * or an empty {@link Optional} if one cannot be constructed.
1186 * @since 12
1187 */
1188 @Override
1189 public Optional<MethodTypeDesc> describeConstable() {
1190 try {
1191 return Optional.of(MethodTypeDesc.of(returnType().describeConstable().orElseThrow(),
1192 Stream.of(parameterArray())
1193 .map(p -> p.describeConstable().orElseThrow())
1194 .toArray(ClassDesc[]::new)));
1195 }
1196 catch (NoSuchElementException e) {
1197 return Optional.empty();
1198 }
1199 }
1200
1201 /// Serialization.
1202
1203 /**
1204 * There are no serializable fields for {@code MethodType}.
1205 */
1206 @java.io.Serial
1207 private static final java.io.ObjectStreamField[] serialPersistentFields = { };
1208
1209 /**
1210 * Save the {@code MethodType} instance to a stream.
1211 *
1212 * @serialData
1213 * For portability, the serialized format does not refer to named fields.
1214 * Instead, the return type and parameter type arrays are written directly
1215 * from the {@code writeObject} method, using two calls to {@code s.writeObject}
1216 * as follows:
1217 * <blockquote><pre>{@code
1218 s.writeObject(this.returnType());
1219 s.writeObject(this.parameterArray());
1220 * }</pre></blockquote>
1221 * <p>
1222 * The deserialized field values are checked as if they were
1223 * provided to the factory method {@link #methodType(Class,Class[]) methodType}.
1224 * For example, null values, or {@code void} parameter types,
1225 * will lead to exceptions during deserialization.
1226 * @param s the stream to write the object to
1227 * @throws java.io.IOException if there is a problem writing the object
1228 */
1229 @java.io.Serial
1230 private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
1231 s.defaultWriteObject(); // requires serialPersistentFields to be an empty array
1232 s.writeObject(returnType());
1233 s.writeObject(parameterArray());
1234 }
1235
1236 /**
1237 * Reconstitute the {@code MethodType} instance from a stream (that is,
1238 * deserialize it).
1239 * This instance is a scratch object with bogus final fields.
1240 * It provides the parameters to the factory method called by
1241 * {@link #readResolve readResolve}.
1242 * After that call it is discarded.
1243 * @param s the stream to read the object from
1244 * @throws java.io.IOException if there is a problem reading the object
1245 * @throws ClassNotFoundException if one of the component classes cannot be resolved
1246 * @see #readResolve
1247 * @see #writeObject
1248 */
1249 @java.io.Serial
1250 private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
1251 // Assign temporary defaults in case this object escapes
1252 MethodType_init(void.class, NO_PTYPES);
1253
1254 s.defaultReadObject(); // requires serialPersistentFields to be an empty array
1255
1256 Class<?> returnType = (Class<?>) s.readObject();
1257 Class<?>[] parameterArray = (Class<?>[]) s.readObject();
1258 parameterArray = parameterArray.clone(); // make sure it is unshared
1259
1260 // Assign deserialized values
1261 MethodType_init(returnType, parameterArray);
1262 }
1263
1264 // Initialization of state for deserialization only
1265 private void MethodType_init(Class<?> rtype, Class<?>[] ptypes) {
1266 // In order to communicate these values to readResolve, we must
1267 // store them into the implementation-specific final fields.
1268 checkRtype(rtype);
1269 checkPtypes(ptypes);
1270 UNSAFE.putReference(this, OffsetHolder.rtypeOffset, rtype);
1271 UNSAFE.putReference(this, OffsetHolder.ptypesOffset, ptypes);
1272 }
1273
1274 // Support for resetting final fields while deserializing. Implement Holder
1275 // pattern to make the rarely needed offset calculation lazy.
1276 private static class OffsetHolder {
1277 static final long rtypeOffset
1278 = UNSAFE.objectFieldOffset(MethodType.class, "rtype");
1279
1280 static final long ptypesOffset
1281 = UNSAFE.objectFieldOffset(MethodType.class, "ptypes");
1282 }
1283
1284 /**
1285 * Resolves and initializes a {@code MethodType} object
1286 * after serialization.
1287 * @return the fully initialized {@code MethodType} object
1288 */
1289 @java.io.Serial
1290 private Object readResolve() {
1291 // Do not use a trusted path for deserialization:
1292 // return makeImpl(rtype, ptypes, true);
1293 // Verify all operands, and make sure ptypes is unshared:
1294 try {
1295 return methodType(rtype, ptypes);
1296 } finally {
1297 // Re-assign defaults in case this object escapes
1298 MethodType_init(void.class, NO_PTYPES);
1299 }
1300 }
1301
1302 /**
1303 * Simple implementation of weak concurrent intern set.
1304 *
1305 * @param <T> interned type
1306 */
1307 private static class ConcurrentWeakInternSet<T> {
1308
1309 private final ConcurrentMap<WeakEntry<T>, WeakEntry<T>> map;
1310 private final ReferenceQueue<T> stale;
1311
1312 public ConcurrentWeakInternSet() {
1313 this.map = new ConcurrentHashMap<>(512);
1314 this.stale = new ReferenceQueue<>();
1315 }
1316
1317 /**
1318 * Get the existing interned element.
1319 * This method returns null if no element is interned.
1320 *
1321 * @param elem element to look up
1322 * @return the interned element
1323 */
1324 public T get(T elem) {
1325 if (elem == null) throw new NullPointerException();
1326 expungeStaleElements();
1327
1328 WeakEntry<T> value = map.get(elem);
1329 if (value != null) {
1330 T res = value.get();
1331 if (res != null) {
1332 return res;
1333 }
1334 }
1335 return null;
1336 }
1337
1338 /**
1339 * Interns the element.
1340 * Always returns non-null element, matching the one in the intern set.
1341 * Under the race against another add(), it can return <i>different</i>
1342 * element, if another thread beats us to interning it.
1343 *
1344 * @param elem element to add
1345 * @return element that was actually added
1346 */
1347 public T add(T elem) {
1348 if (elem == null) throw new NullPointerException();
1349
1350 // Playing double race here, and so spinloop is required.
1351 // First race is with two concurrent updaters.
1352 // Second race is with GC purging weak ref under our feet.
1353 // Hopefully, we almost always end up with a single pass.
1354 T interned;
1355 WeakEntry<T> e = new WeakEntry<>(elem, stale);
1356 do {
1357 expungeStaleElements();
1358 WeakEntry<T> exist = map.putIfAbsent(e, e);
1359 interned = (exist == null) ? elem : exist.get();
1360 } while (interned == null);
1361 return interned;
1362 }
1363
1364 private void expungeStaleElements() {
1365 Reference<? extends T> reference;
1366 while ((reference = stale.poll()) != null) {
1367 map.remove(reference);
1368 }
1369 }
1370
1371 private static class WeakEntry<T> extends WeakReference<T> {
1372
1373 public final int hashcode;
1374
1375 public WeakEntry(T key, ReferenceQueue<T> queue) {
1376 super(key, queue);
1377 hashcode = key.hashCode();
1378 }
1379
1380 /**
1381 * This implementation returns {@code true} if {@code obj} is another
1382 * {@code WeakEntry} whose referent is equal to this referent, or
1383 * if {@code obj} is equal to the referent of this. This allows
1384 * lookups to be made without wrapping in a {@code WeakEntry}.
1385 *
1386 * @param obj the object to compare
1387 * @return true if {@code obj} is equal to this or the referent of this
1388 * @see MethodType#equals(Object)
1389 * @see Object#equals(Object)
1390 */
1391 @Override
1392 public boolean equals(Object obj) {
1393 Object mine = get();
1394 if (obj instanceof WeakEntry) {
1395 Object that = ((WeakEntry) obj).get();
1396 return (that == null || mine == null) ? (this == obj) : mine.equals(that);
1397 }
1398 return (mine == null) ? (obj == null) : mine.equals(obj);
1399 }
1400
1401 @Override
1402 public int hashCode() {
1403 return hashcode;
1404 }
1405
1406 }
1407 }
1408
1409 }