1 /*
2 * Copyright (c) 2008, 2019, 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,
95 * see sections {@jvms 4.4.8} and {@jvms 5.4.3.5} of the Java Virtual Machine Specification.)
96 * <p>
97 * When the JVM materializes a {@code MethodType} from a descriptor string,
98 * all classes named in the descriptor must be accessible, and will be loaded.
99 * (But the classes need not be initialized, as is the case with a {@code CONSTANT_Class}.)
100 * This loading may occur at any time before the {@code MethodType} object is first derived.
101 * @author John Rose, JSR 292 EG
102 * @since 1.7
103 */
104 public final
105 class MethodType
106 implements Constable,
107 TypeDescriptor.OfMethod<Class<?>, MethodType>,
108 java.io.Serializable {
109 @java.io.Serial
110 private static final long serialVersionUID = 292L; // {rtype, {ptype...}}
111
112 // The rtype and ptypes fields define the structural identity of the method type:
113 private final @Stable Class<?> rtype;
114 private final @Stable Class<?>[] ptypes;
115
116 // The remaining fields are caches of various sorts:
117 private @Stable MethodTypeForm form; // erased form, plus cached data about primitives
118 private @Stable MethodType wrapAlt; // alternative wrapped/unwrapped version
119 private @Stable Invokers invokers; // cache of handy higher-order adapters
120 private @Stable String methodDescriptor; // cache for toMethodDescriptorString
121
122 /**
123 * Constructor that performs no copying or validation.
124 * Should only be called from the factory method makeImpl
125 */
126 private MethodType(Class<?> rtype, Class<?>[] ptypes) {
127 this.rtype = rtype;
128 this.ptypes = ptypes;
129 }
130
131 /*trusted*/ MethodTypeForm form() { return form; }
132 /*trusted*/ Class<?> rtype() { return rtype; }
133 /*trusted*/ Class<?>[] ptypes() { return ptypes; }
134
135 void setForm(MethodTypeForm f) { form = f; }
136
137 /** This number, mandated by the JVM spec as 255,
138 * is the maximum number of <em>slots</em>
139 * that any Java method can receive in its argument list.
140 * It limits both JVM signatures and method type objects.
141 * The longest possible invocation will look like
142 * {@code staticMethod(arg1, arg2, ..., arg255)} or
143 * {@code x.virtualMethod(arg1, arg2, ..., arg254)}.
144 */
145 /*non-public*/
146 static final int MAX_JVM_ARITY = 255; // this is mandated by the JVM spec.
147
148 /** This number is the maximum arity of a method handle, 254.
149 * It is derived from the absolute JVM-imposed arity by subtracting one,
150 * which is the slot occupied by the method handle itself at the
151 * beginning of the argument list used to invoke the method handle.
152 * The longest possible invocation will look like
153 * {@code mh.invoke(arg1, arg2, ..., arg254)}.
154 */
155 // Issue: Should we allow MH.invokeWithArguments to go to the full 255?
156 /*non-public*/
157 static final int MAX_MH_ARITY = MAX_JVM_ARITY-1; // deduct one for mh receiver
158
159 /** This number is the maximum arity of a method handle invoker, 253.
160 * It is derived from the absolute JVM-imposed arity by subtracting two,
161 * which are the slots occupied by invoke method handle, and the
162 * target method handle, which are both at the beginning of the argument
163 * list used to invoke the target method handle.
164 * The longest possible invocation will look like
165 * {@code invokermh.invoke(targetmh, arg1, arg2, ..., arg253)}.
166 */
167 /*non-public*/
168 static final int MAX_MH_INVOKER_ARITY = MAX_MH_ARITY-1; // deduct one more for invoker
169
170 private static void checkRtype(Class<?> rtype) {
171 Objects.requireNonNull(rtype);
172 }
173 private static void checkPtype(Class<?> ptype) {
174 Objects.requireNonNull(ptype);
175 if (ptype == void.class)
176 throw newIllegalArgumentException("parameter type cannot be void");
177 }
178 /** Return number of extra slots (count of long/double args). */
179 private static int checkPtypes(Class<?>[] ptypes) {
180 int slots = 0;
181 for (Class<?> ptype : ptypes) {
182 checkPtype(ptype);
183 if (ptype == double.class || ptype == long.class) {
184 slots++;
185 }
186 }
187 checkSlotCount(ptypes.length + slots);
188 return slots;
189 }
190
191 static {
192 // MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work:
193 assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0);
194 }
195 static void checkSlotCount(int count) {
196 if ((count & MAX_JVM_ARITY) != count)
197 throw newIllegalArgumentException("bad parameter count "+count);
198 }
199 private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) {
200 if (num instanceof Integer) num = "bad index: "+num;
201 return new IndexOutOfBoundsException(num.toString());
202 }
203
204 static final ConcurrentWeakInternSet<MethodType> internTable = new ConcurrentWeakInternSet<>();
205
206 static final Class<?>[] NO_PTYPES = {};
207
208 /**
209 * Finds or creates an instance of the given method type.
210 * @param rtype the return type
211 * @param ptypes the parameter types
212 * @return a method type with the given components
213 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
214 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
215 */
216 public static MethodType methodType(Class<?> rtype, Class<?>[] ptypes) {
217 return makeImpl(rtype, ptypes, false);
218 }
219
220 /**
221 * Finds or creates a method type with the given components.
222 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
223 * @param rtype the return type
224 * @param ptypes the parameter types
225 * @return a method type with the given components
226 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
227 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
228 */
229 public static MethodType methodType(Class<?> rtype, List<Class<?>> ptypes) {
230 boolean notrust = false; // random List impl. could return evil ptypes array
231 return makeImpl(rtype, listToArray(ptypes), notrust);
232 }
233
234 private static Class<?>[] listToArray(List<Class<?>> ptypes) {
235 // sanity check the size before the toArray call, since size might be huge
236 checkSlotCount(ptypes.size());
237 return ptypes.toArray(NO_PTYPES);
238 }
239
240 /**
241 * Finds or creates a method type with the given components.
242 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
243 * The leading parameter type is prepended to the remaining array.
244 * @param rtype the return type
245 * @param ptype0 the first parameter type
246 * @param ptypes the remaining parameter types
247 * @return a method type with the given components
248 * @throws NullPointerException if {@code rtype} or {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is null
249 * @throws IllegalArgumentException if {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is {@code void.class}
250 */
251 public static MethodType methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes) {
252 Class<?>[] ptypes1 = new Class<?>[1+ptypes.length];
253 ptypes1[0] = ptype0;
254 System.arraycopy(ptypes, 0, ptypes1, 1, ptypes.length);
255 return makeImpl(rtype, ptypes1, true);
256 }
257
258 /**
259 * Finds or creates a method type with the given components.
260 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
261 * The resulting method has no parameter types.
262 * @param rtype the return type
263 * @return a method type with the given return value
264 * @throws NullPointerException if {@code rtype} is null
265 */
266 public static MethodType methodType(Class<?> rtype) {
267 return makeImpl(rtype, NO_PTYPES, true);
268 }
269
270 /**
271 * Finds or creates a method type with the given components.
272 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
273 * The resulting method has the single given parameter type.
274 * @param rtype the return type
275 * @param ptype0 the parameter type
276 * @return a method type with the given return value and parameter type
277 * @throws NullPointerException if {@code rtype} or {@code ptype0} is null
278 * @throws IllegalArgumentException if {@code ptype0} is {@code void.class}
279 */
280 public static MethodType methodType(Class<?> rtype, Class<?> ptype0) {
281 return makeImpl(rtype, new Class<?>[]{ ptype0 }, true);
282 }
283
284 /**
285 * Finds or creates a method type with the given components.
286 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
287 * The resulting method has the same parameter types as {@code ptypes},
288 * and the specified return type.
289 * @param rtype the return type
290 * @param ptypes the method type which supplies the parameter types
291 * @return a method type with the given components
292 * @throws NullPointerException if {@code rtype} or {@code ptypes} is null
293 */
294 public static MethodType methodType(Class<?> rtype, MethodType ptypes) {
295 return makeImpl(rtype, ptypes.ptypes, true);
296 }
297
298 /**
299 * Sole factory method to find or create an interned method type.
300 * @param rtype desired return type
301 * @param ptypes desired parameter types
302 * @param trusted whether the ptypes can be used without cloning
303 * @return the unique method type of the desired structure
304 */
305 /*trusted*/
306 static MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {
307 if (ptypes.length == 0) {
308 ptypes = NO_PTYPES; trusted = true;
309 }
310 MethodType primordialMT = new MethodType(rtype, ptypes);
311 MethodType mt = internTable.get(primordialMT);
312 if (mt != null)
313 return mt;
314
315 // promote the object to the Real Thing, and reprobe
316 MethodType.checkRtype(rtype);
317 if (trusted) {
318 MethodType.checkPtypes(ptypes);
319 mt = primordialMT;
320 } else {
321 // Make defensive copy then validate
322 ptypes = Arrays.copyOf(ptypes, ptypes.length);
323 MethodType.checkPtypes(ptypes);
324 mt = new MethodType(rtype, ptypes);
325 }
326 mt.form = MethodTypeForm.findForm(mt);
327 return internTable.add(mt);
328 }
329 private static final @Stable MethodType[] objectOnlyTypes = new MethodType[20];
330
331 /**
332 * Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array.
333 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
334 * All parameters and the return type will be {@code Object},
335 * except the final array parameter if any, which will be {@code Object[]}.
336 * @param objectArgCount number of parameters (excluding the final array parameter if any)
337 * @param finalArray whether there will be a trailing array parameter, of type {@code Object[]}
338 * @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments
339 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true)
340 * @see #genericMethodType(int)
341 */
342 public static MethodType genericMethodType(int objectArgCount, boolean finalArray) {
343 MethodType mt;
344 checkSlotCount(objectArgCount);
345 int ivarargs = (!finalArray ? 0 : 1);
346 int ootIndex = objectArgCount*2 + ivarargs;
347 if (ootIndex < objectOnlyTypes.length) {
348 mt = objectOnlyTypes[ootIndex];
349 if (mt != null) return mt;
350 }
351 Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs];
352 Arrays.fill(ptypes, Object.class);
353 if (ivarargs != 0) ptypes[objectArgCount] = Object[].class;
354 mt = makeImpl(Object.class, ptypes, true);
355 if (ootIndex < objectOnlyTypes.length) {
356 objectOnlyTypes[ootIndex] = mt; // cache it here also!
357 }
358 return mt;
359 }
360
361 /**
362 * Finds or creates a method type whose components are all {@code Object}.
363 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
364 * All parameters and the return type will be Object.
365 * @param objectArgCount number of parameters
366 * @return a generally applicable method type, for all calls of the given argument count
367 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255
368 * @see #genericMethodType(int, boolean)
369 */
370 public static MethodType genericMethodType(int objectArgCount) {
371 return genericMethodType(objectArgCount, false);
372 }
373
374 /**
375 * Finds or creates a method type with a single different parameter type.
376 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
377 * @param num the index (zero-based) of the parameter type to change
378 * @param nptype a new parameter type to replace the old one with
379 * @return the same type, except with the selected parameter changed
380 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
381 * @throws IllegalArgumentException if {@code nptype} is {@code void.class}
382 * @throws NullPointerException if {@code nptype} is null
383 */
384 public MethodType changeParameterType(int num, Class<?> nptype) {
385 if (parameterType(num) == nptype) return this;
386 checkPtype(nptype);
387 Class<?>[] nptypes = ptypes.clone();
388 nptypes[num] = nptype;
389 return makeImpl(rtype, nptypes, true);
390 }
391
392 /**
393 * Finds or creates a method type with additional parameter types.
394 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
395 * @param num the position (zero-based) of the inserted parameter type(s)
396 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
397 * @return the same type, except with the selected parameter(s) inserted
398 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
399 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
400 * or if the resulting method type would have more than 255 parameter slots
401 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
402 */
403 public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) {
404 int len = ptypes.length;
405 if (num < 0 || num > len)
406 throw newIndexOutOfBoundsException(num);
407 int ins = checkPtypes(ptypesToInsert);
408 checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins);
409 int ilen = ptypesToInsert.length;
410 if (ilen == 0) return this;
411 Class<?>[] nptypes = new Class<?>[len + ilen];
412 if (num > 0) {
413 System.arraycopy(ptypes, 0, nptypes, 0, num);
414 }
415 System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen);
416 if (num < len) {
417 System.arraycopy(ptypes, num, nptypes, num+ilen, len-num);
418 }
419 return makeImpl(rtype, nptypes, true);
420 }
421
422 /**
423 * Finds or creates a method type with additional parameter types.
424 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
425 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
426 * @return the same type, except with the selected parameter(s) appended
427 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
428 * or if the resulting method type would have more than 255 parameter slots
429 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
430 */
431 public MethodType appendParameterTypes(Class<?>... ptypesToInsert) {
432 return insertParameterTypes(parameterCount(), ptypesToInsert);
433 }
434
435 /**
436 * Finds or creates a method type with additional parameter types.
437 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
438 * @param num the position (zero-based) of the inserted parameter type(s)
439 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
440 * @return the same type, except with the selected parameter(s) inserted
441 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
442 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
443 * or if the resulting method type would have more than 255 parameter slots
444 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
445 */
446 public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) {
447 return insertParameterTypes(num, listToArray(ptypesToInsert));
448 }
449
450 /**
451 * Finds or creates a method type with additional parameter types.
452 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
453 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
454 * @return the same type, except with the selected parameter(s) appended
455 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
456 * or if the resulting method type would have more than 255 parameter slots
457 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
458 */
459 public MethodType appendParameterTypes(List<Class<?>> ptypesToInsert) {
460 return insertParameterTypes(parameterCount(), ptypesToInsert);
461 }
462
463 /**
464 * Finds or creates a method type with modified parameter types.
465 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
466 * @param start the position (zero-based) of the first replaced parameter type(s)
467 * @param end the position (zero-based) after the last replaced parameter type(s)
468 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
469 * @return the same type, except with the selected parameter(s) replaced
470 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
471 * or if {@code end} is negative or greater than {@code parameterCount()}
472 * or if {@code start} is greater than {@code end}
473 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
474 * or if the resulting method type would have more than 255 parameter slots
475 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
476 */
477 /*non-public*/
478 MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) {
479 if (start == end)
480 return insertParameterTypes(start, ptypesToInsert);
481 int len = ptypes.length;
482 if (!(0 <= start && start <= end && end <= len))
483 throw newIndexOutOfBoundsException("start="+start+" end="+end);
484 int ilen = ptypesToInsert.length;
485 if (ilen == 0)
486 return dropParameterTypes(start, end);
487 return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert);
488 }
489
490 /** Replace the last arrayLength parameter types with the component type of arrayType.
491 * @param arrayType any array type
492 * @param pos position at which to spread
493 * @param arrayLength the number of parameter types to change
494 * @return the resulting type
495 */
496 /*non-public*/
497 MethodType asSpreaderType(Class<?> arrayType, int pos, int arrayLength) {
498 assert(parameterCount() >= arrayLength);
499 int spreadPos = pos;
500 if (arrayLength == 0) return this; // nothing to change
501 if (arrayType == Object[].class) {
502 if (isGeneric()) return this; // nothing to change
503 if (spreadPos == 0) {
504 // no leading arguments to preserve; go generic
505 MethodType res = genericMethodType(arrayLength);
506 if (rtype != Object.class) {
507 res = res.changeReturnType(rtype);
508 }
509 return res;
510 }
511 }
512 Class<?> elemType = arrayType.getComponentType();
513 assert(elemType != null);
514 for (int i = spreadPos; i < spreadPos + arrayLength; i++) {
515 if (ptypes[i] != elemType) {
516 Class<?>[] fixedPtypes = ptypes.clone();
517 Arrays.fill(fixedPtypes, i, spreadPos + arrayLength, elemType);
518 return methodType(rtype, fixedPtypes);
519 }
520 }
521 return this; // arguments check out; no change
522 }
523
524 /** Return the leading parameter type, which must exist and be a reference.
525 * @return the leading parameter type, after error checks
526 */
527 /*non-public*/
528 Class<?> leadingReferenceParameter() {
529 Class<?> ptype;
530 if (ptypes.length == 0 ||
531 (ptype = ptypes[0]).isPrimitive())
532 throw newIllegalArgumentException("no leading reference parameter");
533 return ptype;
534 }
535
536 /** Delete the last parameter type and replace it with arrayLength copies of the component type of arrayType.
537 * @param arrayType any array type
538 * @param pos position at which to insert parameters
539 * @param arrayLength the number of parameter types to insert
540 * @return the resulting type
541 */
542 /*non-public*/
543 MethodType asCollectorType(Class<?> arrayType, int pos, int arrayLength) {
544 assert(parameterCount() >= 1);
545 assert(pos < ptypes.length);
546 assert(ptypes[pos].isAssignableFrom(arrayType));
547 MethodType res;
548 if (arrayType == Object[].class) {
549 res = genericMethodType(arrayLength);
550 if (rtype != Object.class) {
551 res = res.changeReturnType(rtype);
552 }
553 } else {
554 Class<?> elemType = arrayType.getComponentType();
555 assert(elemType != null);
556 res = methodType(rtype, Collections.nCopies(arrayLength, elemType));
557 }
558 if (ptypes.length == 1) {
559 return res;
560 } else {
561 // insert after (if need be), then before
562 if (pos < ptypes.length - 1) {
563 res = res.insertParameterTypes(arrayLength, Arrays.copyOfRange(ptypes, pos + 1, ptypes.length));
564 }
565 return res.insertParameterTypes(0, Arrays.copyOf(ptypes, pos));
566 }
567 }
568
569 /**
570 * Finds or creates a method type with some parameter types omitted.
571 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
572 * @param start the index (zero-based) of the first parameter type to remove
573 * @param end the index (greater than {@code start}) of the first parameter type after not to remove
574 * @return the same type, except with the selected parameter(s) removed
575 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
576 * or if {@code end} is negative or greater than {@code parameterCount()}
577 * or if {@code start} is greater than {@code end}
578 */
579 public MethodType dropParameterTypes(int start, int end) {
580 int len = ptypes.length;
581 if (!(0 <= start && start <= end && end <= len))
582 throw newIndexOutOfBoundsException("start="+start+" end="+end);
583 if (start == end) return this;
584 Class<?>[] nptypes;
585 if (start == 0) {
586 if (end == len) {
587 // drop all parameters
588 nptypes = NO_PTYPES;
589 } else {
590 // drop initial parameter(s)
591 nptypes = Arrays.copyOfRange(ptypes, end, len);
592 }
593 } else {
594 if (end == len) {
595 // drop trailing parameter(s)
596 nptypes = Arrays.copyOfRange(ptypes, 0, start);
597 } else {
598 int tail = len - end;
599 nptypes = Arrays.copyOfRange(ptypes, 0, start + tail);
600 System.arraycopy(ptypes, end, nptypes, start, tail);
601 }
602 }
603 return makeImpl(rtype, nptypes, true);
604 }
605
606 /**
607 * Finds or creates a method type with a different return type.
608 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
609 * @param nrtype a return parameter type to replace the old one with
610 * @return the same type, except with the return type change
611 * @throws NullPointerException if {@code nrtype} is null
612 */
613 public MethodType changeReturnType(Class<?> nrtype) {
614 if (returnType() == nrtype) return this;
615 return makeImpl(nrtype, ptypes, true);
616 }
617
618 /**
619 * Reports if this type contains a primitive argument or return value.
620 * The return type {@code void} counts as a primitive.
621 * @return true if any of the types are primitives
622 */
623 public boolean hasPrimitives() {
624 return form.hasPrimitives();
625 }
626
627 /**
628 * Reports if this type contains a wrapper argument or return value.
629 * Wrappers are types which box primitive values, such as {@link Integer}.
630 * The reference type {@code java.lang.Void} counts as a wrapper,
631 * if it occurs as a return type.
632 * @return true if any of the types are wrappers
633 */
634 public boolean hasWrappers() {
635 return unwrap() != this;
636 }
637
638 /**
639 * Erases all reference types to {@code Object}.
640 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
641 * All primitive types (including {@code void}) will remain unchanged.
642 * @return a version of the original type with all reference types replaced
643 */
644 public MethodType erase() {
645 return form.erasedType();
646 }
647
648 /**
649 * Erases all reference types to {@code Object}, and all subword types to {@code int}.
650 * This is the reduced type polymorphism used by private methods
651 * such as {@link MethodHandle#invokeBasic invokeBasic}.
652 * @return a version of the original type with all reference and subword types replaced
653 */
654 /*non-public*/
655 MethodType basicType() {
656 return form.basicType();
657 }
658
659 private static final @Stable Class<?>[] METHOD_HANDLE_ARRAY
660 = new Class<?>[] { MethodHandle.class };
661
662 /**
663 * @return a version of the original type with MethodHandle prepended as the first argument
664 */
665 /*non-public*/
666 MethodType invokerType() {
667 return insertParameterTypes(0, METHOD_HANDLE_ARRAY);
668 }
669
670 /**
671 * Converts all types, both reference and primitive, to {@code Object}.
672 * Convenience method for {@link #genericMethodType(int) genericMethodType}.
673 * The expression {@code type.wrap().erase()} produces the same value
674 * as {@code type.generic()}.
675 * @return a version of the original type with all types replaced
676 */
677 public MethodType generic() {
678 return genericMethodType(parameterCount());
679 }
680
681 /*non-public*/
682 boolean isGeneric() {
683 return this == erase() && !hasPrimitives();
684 }
685
686 /**
687 * Converts all primitive types to their corresponding wrapper types.
688 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
689 * All reference types (including wrapper types) will remain unchanged.
690 * A {@code void} return type is changed to the type {@code java.lang.Void}.
691 * The expression {@code type.wrap().erase()} produces the same value
692 * as {@code type.generic()}.
693 * @return a version of the original type with all primitive types replaced
694 */
695 public MethodType wrap() {
696 return hasPrimitives() ? wrapWithPrims(this) : this;
697 }
698
699 /**
700 * Converts all wrapper types to their corresponding primitive types.
701 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
702 * All primitive types (including {@code void}) will remain unchanged.
703 * A return type of {@code java.lang.Void} is changed to {@code void}.
704 * @return a version of the original type with all wrapper types replaced
705 */
706 public MethodType unwrap() {
707 MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this);
708 return unwrapWithNoPrims(noprims);
709 }
710
711 private static MethodType wrapWithPrims(MethodType pt) {
712 assert(pt.hasPrimitives());
713 MethodType wt = pt.wrapAlt;
714 if (wt == null) {
715 // fill in lazily
716 wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP, MethodTypeForm.WRAP);
717 assert(wt != null);
718 pt.wrapAlt = wt;
719 }
720 return wt;
721 }
722
723 private static MethodType unwrapWithNoPrims(MethodType wt) {
724 assert(!wt.hasPrimitives());
725 MethodType uwt = wt.wrapAlt;
726 if (uwt == null) {
727 // fill in lazily
728 uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP, MethodTypeForm.UNWRAP);
729 if (uwt == null)
730 uwt = wt; // type has no wrappers or prims at all
731 wt.wrapAlt = uwt;
732 }
733 return uwt;
734 }
735
736 /**
737 * Returns the parameter type at the specified index, within this method type.
738 * @param num the index (zero-based) of the desired parameter type
739 * @return the selected parameter type
740 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
741 */
742 public Class<?> parameterType(int num) {
743 return ptypes[num];
744 }
745 /**
746 * Returns the number of parameter types in this method type.
747 * @return the number of parameter types
748 */
749 public int parameterCount() {
750 return ptypes.length;
751 }
752 /**
753 * Returns the return type of this method type.
754 * @return the return type
755 */
756 public Class<?> returnType() {
757 return rtype;
758 }
759
760 /**
761 * Presents the parameter types as a list (a convenience method).
762 * The list will be immutable.
763 * @return the parameter types (as an immutable list)
764 */
765 public List<Class<?>> parameterList() {
766 return Collections.unmodifiableList(Arrays.asList(ptypes.clone()));
767 }
768
769 /**
770 * Returns the last parameter type of this method type.
771 * If this type has no parameters, the sentinel value
772 * {@code void.class} is returned instead.
773 * @apiNote
774 * <p>
775 * The sentinel value is chosen so that reflective queries can be
776 * made directly against the result value.
777 * The sentinel value cannot be confused with a real parameter,
778 * since {@code void} is never acceptable as a parameter type.
779 * For variable arity invocation modes, the expression
780 * {@link Class#getComponentType lastParameterType().getComponentType()}
781 * is useful to query the type of the "varargs" parameter.
782 * @return the last parameter type if any, else {@code void.class}
783 * @since 10
784 */
785 public Class<?> lastParameterType() {
786 int len = ptypes.length;
787 return len == 0 ? void.class : ptypes[len-1];
788 }
789
790 /**
791 * Presents the parameter types as an array (a convenience method).
792 * Changes to the array will not result in changes to the type.
793 * @return the parameter types (as a fresh copy if necessary)
794 */
795 public Class<?>[] parameterArray() {
796 return ptypes.clone();
797 }
798
799 /**
800 * Compares the specified object with this type for equality.
801 * That is, it returns {@code true} if and only if the specified object
802 * is also a method type with exactly the same parameters and return type.
803 * @param x object to compare
804 * @see Object#equals(Object)
805 */
806 // This implementation may also return true if x is a WeakEntry containing
807 // a method type that is equal to this. This is an internal implementation
808 // detail to allow for faster method type lookups.
809 // See ConcurrentWeakInternSet.WeakEntry#equals(Object)
810 @Override
811 public boolean equals(Object x) {
812 if (this == x) {
813 return true;
814 }
815 if (x instanceof MethodType) {
816 return equals((MethodType)x);
817 }
818 if (x instanceof ConcurrentWeakInternSet.WeakEntry) {
819 Object o = ((ConcurrentWeakInternSet.WeakEntry)x).get();
820 if (o instanceof MethodType) {
821 return equals((MethodType)o);
822 }
823 }
824 return false;
825 }
826
827 private boolean equals(MethodType that) {
828 return this.rtype == that.rtype
829 && Arrays.equals(this.ptypes, that.ptypes);
830 }
831
832 /**
833 * Returns the hash code value for this method type.
834 * It is defined to be the same as the hashcode of a List
835 * whose elements are the return type followed by the
836 * parameter types.
837 * @return the hash code value for this method type
838 * @see Object#hashCode()
839 * @see #equals(Object)
840 * @see List#hashCode()
841 */
842 @Override
843 public int hashCode() {
844 int hashCode = 31 + rtype.hashCode();
845 for (Class<?> ptype : ptypes)
846 hashCode = 31 * hashCode + ptype.hashCode();
847 return hashCode;
848 }
849
850 /**
851 * Returns a string representation of the method type,
852 * of the form {@code "(PT0,PT1...)RT"}.
853 * The string representation of a method type is a
854 * parenthesis enclosed, comma separated list of type names,
855 * followed immediately by the return type.
856 * <p>
857 * Each type is represented by its
858 * {@link java.lang.Class#getSimpleName simple name}.
859 */
860 @Override
861 public String toString() {
862 StringJoiner sj = new StringJoiner(",", "(",
863 ")" + rtype.getSimpleName());
864 for (int i = 0; i < ptypes.length; i++) {
865 sj.add(ptypes[i].getSimpleName());
866 }
867 return sj.toString();
868 }
869
870 /** True if my parameter list is effectively identical to the given full list,
871 * after skipping the given number of my own initial parameters.
872 * In other words, after disregarding {@code skipPos} parameters,
873 * my remaining parameter list is no longer than the {@code fullList}, and
874 * is equal to the same-length initial sublist of {@code fullList}.
875 */
876 /*non-public*/
877 boolean effectivelyIdenticalParameters(int skipPos, List<Class<?>> fullList) {
878 int myLen = ptypes.length, fullLen = fullList.size();
879 if (skipPos > myLen || myLen - skipPos > fullLen)
880 return false;
881 List<Class<?>> myList = Arrays.asList(ptypes);
882 if (skipPos != 0) {
883 myList = myList.subList(skipPos, myLen);
884 myLen -= skipPos;
885 }
886 if (fullLen == myLen)
887 return myList.equals(fullList);
888 else
889 return myList.equals(fullList.subList(0, myLen));
890 }
891
892 /** True if the old return type can always be viewed (w/o casting) under new return type,
893 * and the new parameters can be viewed (w/o casting) under the old parameter types.
894 */
895 /*non-public*/
896 boolean isViewableAs(MethodType newType, boolean keepInterfaces) {
897 if (!VerifyType.isNullConversion(returnType(), newType.returnType(), keepInterfaces))
898 return false;
899 if (form == newType.form && form.erasedType == this)
900 return true; // my reference parameters are all Object
901 if (ptypes == newType.ptypes)
902 return true;
903 int argc = parameterCount();
904 if (argc != newType.parameterCount())
905 return false;
906 for (int i = 0; i < argc; i++) {
907 if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i), keepInterfaces))
908 return false;
909 }
910 return true;
911 }
912 /*non-public*/
913 boolean isConvertibleTo(MethodType newType) {
914 MethodTypeForm oldForm = this.form();
915 MethodTypeForm newForm = newType.form();
916 if (oldForm == newForm)
917 // same parameter count, same primitive/object mix
918 return true;
919 if (!canConvert(returnType(), newType.returnType()))
920 return false;
921 Class<?>[] srcTypes = newType.ptypes;
922 Class<?>[] dstTypes = ptypes;
923 if (srcTypes == dstTypes)
924 return true;
925 int argc;
926 if ((argc = srcTypes.length) != dstTypes.length)
927 return false;
928 if (argc <= 1) {
929 if (argc == 1 && !canConvert(srcTypes[0], dstTypes[0]))
930 return false;
931 return true;
932 }
933 if ((!oldForm.hasPrimitives() && oldForm.erasedType == this) ||
934 (!newForm.hasPrimitives() && newForm.erasedType == newType)) {
935 // Somewhat complicated test to avoid a loop of 2 or more trips.
936 // If either type has only Object parameters, we know we can convert.
937 assert(canConvertParameters(srcTypes, dstTypes));
938 return true;
939 }
940 return canConvertParameters(srcTypes, dstTypes);
941 }
942
943 /** Returns true if MHs.explicitCastArguments produces the same result as MH.asType.
944 * If the type conversion is impossible for either, the result should be false.
945 */
946 /*non-public*/
947 boolean explicitCastEquivalentToAsType(MethodType newType) {
948 if (this == newType) return true;
949 if (!explicitCastEquivalentToAsType(rtype, newType.rtype)) {
950 return false;
951 }
952 Class<?>[] srcTypes = newType.ptypes;
953 Class<?>[] dstTypes = ptypes;
954 if (dstTypes == srcTypes) {
955 return true;
956 }
957 assert(dstTypes.length == srcTypes.length);
958 for (int i = 0; i < dstTypes.length; i++) {
959 if (!explicitCastEquivalentToAsType(srcTypes[i], dstTypes[i])) {
960 return false;
961 }
962 }
963 return true;
964 }
965
966 /** Reports true if the src can be converted to the dst, by both asType and MHs.eCE,
967 * and with the same effect.
968 * MHs.eCA has the following "upgrades" to MH.asType:
969 * 1. interfaces are unchecked (that is, treated as if aliased to Object)
970 * Therefore, {@code Object->CharSequence} is possible in both cases but has different semantics
971 * 2. the full matrix of primitive-to-primitive conversions is supported
972 * Narrowing like {@code long->byte} and basic-typing like {@code boolean->int}
973 * are not supported by asType, but anything supported by asType is equivalent
974 * with MHs.eCE.
975 * 3a. unboxing conversions can be followed by the full matrix of primitive conversions
976 * 3b. unboxing of null is permitted (creates a zero primitive value)
977 * Other than interfaces, reference-to-reference conversions are the same.
978 * Boxing primitives to references is the same for both operators.
979 */
980 private static boolean explicitCastEquivalentToAsType(Class<?> src, Class<?> dst) {
981 if (src == dst || dst == Object.class || dst == void.class) return true;
982 if (src.isPrimitive()) {
983 // Could be a prim/prim conversion, where casting is a strict superset.
984 // Or a boxing conversion, which is always to an exact wrapper class.
985 return canConvert(src, dst);
986 } else if (dst.isPrimitive()) {
987 // Unboxing behavior is different between MHs.eCA & MH.asType (see 3b).
988 return false;
989 } else {
990 // R->R always works, but we have to avoid a check-cast to an interface.
991 return !dst.isInterface() || dst.isAssignableFrom(src);
992 }
993 }
994
995 private boolean canConvertParameters(Class<?>[] srcTypes, Class<?>[] dstTypes) {
996 for (int i = 0; i < srcTypes.length; i++) {
997 if (!canConvert(srcTypes[i], dstTypes[i])) {
998 return false;
999 }
1000 }
1001 return true;
1002 }
1003
1004 /*non-public*/
1005 static boolean canConvert(Class<?> src, Class<?> dst) {
1006 // short-circuit a few cases:
1007 if (src == dst || src == Object.class || dst == Object.class) return true;
1008 // the remainder of this logic is documented in MethodHandle.asType
1009 if (src.isPrimitive()) {
1010 // can force void to an explicit null, a la reflect.Method.invoke
1011 // can also force void to a primitive zero, by analogy
1012 if (src == void.class) return true; //or !dst.isPrimitive()?
1013 Wrapper sw = Wrapper.forPrimitiveType(src);
1014 if (dst.isPrimitive()) {
1015 // P->P must widen
1016 return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw);
1017 } else {
1018 // P->R must box and widen
1019 return dst.isAssignableFrom(sw.wrapperType());
1020 }
1021 } else if (dst.isPrimitive()) {
1022 // any value can be dropped
1023 if (dst == void.class) return true;
1024 Wrapper dw = Wrapper.forPrimitiveType(dst);
1025 // R->P must be able to unbox (from a dynamically chosen type) and widen
1026 // For example:
1027 // Byte/Number/Comparable/Object -> dw:Byte -> byte.
1028 // Character/Comparable/Object -> dw:Character -> char
1029 // Boolean/Comparable/Object -> dw:Boolean -> boolean
1030 // This means that dw must be cast-compatible with src.
1031 if (src.isAssignableFrom(dw.wrapperType())) {
1032 return true;
1033 }
1034 // The above does not work if the source reference is strongly typed
1035 // to a wrapper whose primitive must be widened. For example:
1036 // Byte -> unbox:byte -> short/int/long/float/double
1037 // Character -> unbox:char -> int/long/float/double
1038 if (Wrapper.isWrapperType(src) &&
1039 dw.isConvertibleFrom(Wrapper.forWrapperType(src))) {
1040 // can unbox from src and then widen to dst
1041 return true;
1042 }
1043 // We have already covered cases which arise due to runtime unboxing
1044 // of a reference type which covers several wrapper types:
1045 // Object -> cast:Integer -> unbox:int -> long/float/double
1046 // Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double
1047 // An marginal case is Number -> dw:Character -> char, which would be OK if there were a
1048 // subclass of Number which wraps a value that can convert to char.
1049 // Since there is none, we don't need an extra check here to cover char or boolean.
1050 return false;
1051 } else {
1052 // R->R always works, since null is always valid dynamically
1053 return true;
1054 }
1055 }
1056
1057 /// Queries which have to do with the bytecode architecture
1058
1059 /** Reports the number of JVM stack slots required to invoke a method
1060 * of this type. Note that (for historical reasons) the JVM requires
1061 * a second stack slot to pass long and double arguments.
1062 * So this method returns {@link #parameterCount() parameterCount} plus the
1063 * number of long and double parameters (if any).
1064 * <p>
1065 * This method is included for the benefit of applications that must
1066 * generate bytecodes that process method handles and invokedynamic.
1067 * @return the number of JVM stack slots for this type's parameters
1068 */
1069 /*non-public*/
1070 int parameterSlotCount() {
1071 return form.parameterSlotCount();
1072 }
1073
1074 /*non-public*/
1075 Invokers invokers() {
1076 Invokers inv = invokers;
1077 if (inv != null) return inv;
1078 invokers = inv = new Invokers(this);
1079 return inv;
1080 }
1081
1082 /**
1083 * Finds or creates an instance of a method type, given the spelling of its bytecode descriptor.
1084 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
1085 * Any class or interface name embedded in the descriptor string will be
1086 * resolved by the given loader (or if it is null, on the system class loader).
1087 * <p>
1088 * Note that it is possible to encounter method types which cannot be
1089 * constructed by this method, because their component types are
1090 * not all reachable from a common class loader.
1091 * <p>
1092 * This method is included for the benefit of applications that must
1093 * generate bytecodes that process method handles and {@code invokedynamic}.
1094 * @param descriptor a bytecode-level type descriptor string "(T...)T"
1095 * @param loader the class loader in which to look up the types
1096 * @return a method type matching the bytecode-level type descriptor
1097 * @throws NullPointerException if the string is null
1098 * @throws IllegalArgumentException if the string is not well-formed
1099 * @throws TypeNotPresentException if a named type cannot be found
1100 * @throws SecurityException if the security manager is present and
1101 * {@code loader} is {@code null} and the caller does not have the
1102 * {@link RuntimePermission}{@code ("getClassLoader")}
1103 */
1104 public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader)
1105 throws IllegalArgumentException, TypeNotPresentException
1106 {
1107 if (loader == null) {
1108 SecurityManager sm = System.getSecurityManager();
1109 if (sm != null) {
1110 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
1111 }
1112 }
1113 return fromDescriptor(descriptor,
1114 (loader == null) ? ClassLoader.getSystemClassLoader() : loader);
1115 }
1116
1117 /**
1118 * Same as {@link #fromMethodDescriptorString(String, ClassLoader)}, but
1119 * {@code null} ClassLoader means the bootstrap loader is used here.
1120 * <p>
1121 * IMPORTANT: This method is preferable for JDK internal use as it more
1122 * correctly interprets {@code null} ClassLoader than
1123 * {@link #fromMethodDescriptorString(String, ClassLoader)}.
1124 * Use of this method also avoids early initialization issues when system
1125 * ClassLoader is not initialized yet.
1126 */
1127 static MethodType fromDescriptor(String descriptor, ClassLoader loader)
1128 throws IllegalArgumentException, TypeNotPresentException
1129 {
1130 if (!descriptor.startsWith("(") || // also generates NPE if needed
1131 descriptor.indexOf(')') < 0 ||
1132 descriptor.indexOf('.') >= 0)
1133 throw newIllegalArgumentException("not a method descriptor: "+descriptor);
1134 List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader);
1135 Class<?> rtype = types.remove(types.size() - 1);
1136 Class<?>[] ptypes = listToArray(types);
1137 return makeImpl(rtype, ptypes, true);
1138 }
1139
1140 /**
1141 * Produces a bytecode descriptor representation of the method type.
1142 * <p>
1143 * Note that this is not a strict inverse of {@link #fromMethodDescriptorString fromMethodDescriptorString}.
1144 * Two distinct classes which share a common name but have different class loaders
1145 * will appear identical when viewed within descriptor strings.
1146 * <p>
1147 * This method is included for the benefit of applications that must
1148 * generate bytecodes that process method handles and {@code invokedynamic}.
1149 * {@link #fromMethodDescriptorString(java.lang.String, java.lang.ClassLoader) fromMethodDescriptorString},
1150 * because the latter requires a suitable class loader argument.
1151 * @return the bytecode type descriptor representation
1152 */
1153 public String toMethodDescriptorString() {
1154 String desc = methodDescriptor;
1155 if (desc == null) {
1156 desc = BytecodeDescriptor.unparseMethod(this.rtype, this.ptypes);
1157 methodDescriptor = desc;
1158 }
1159 return desc;
1160 }
1161
1162 /**
1163 * Return a field type descriptor string for this type
1164 *
1165 * @return the descriptor string
1166 * @jvms 4.3.2 Field Descriptors
1167 * @since 12
1168 */
1169 @Override
1170 public String descriptorString() {
1171 return toMethodDescriptorString();
1172 }
1173
1174 /*non-public*/
1175 static String toFieldDescriptorString(Class<?> cls) {
1176 return BytecodeDescriptor.unparse(cls);
1177 }
1178
1179 /**
1180 * Return a nominal descriptor for this instance, if one can be
1181 * constructed, or an empty {@link Optional} if one cannot be.
1182 *
1183 * @return An {@link Optional} containing the resulting nominal descriptor,
1184 * or an empty {@link Optional} if one cannot be constructed.
1185 * @since 12
1186 */
1187 @Override
1188 public Optional<MethodTypeDesc> describeConstable() {
1189 try {
1190 return Optional.of(MethodTypeDesc.of(returnType().describeConstable().orElseThrow(),
1191 Stream.of(parameterArray())
1192 .map(p -> p.describeConstable().orElseThrow())
1193 .toArray(ClassDesc[]::new)));
1194 }
1195 catch (NoSuchElementException e) {
1196 return Optional.empty();
1197 }
1198 }
1199
1200 /// Serialization.
1201
1202 /**
1203 * There are no serializable fields for {@code MethodType}.
1204 */
1205 @java.io.Serial
1206 private static final java.io.ObjectStreamField[] serialPersistentFields = { };
1207
1208 /**
1209 * Save the {@code MethodType} instance to a stream.
1210 *
1211 * @serialData
1212 * For portability, the serialized format does not refer to named fields.
1213 * Instead, the return type and parameter type arrays are written directly
1214 * from the {@code writeObject} method, using two calls to {@code s.writeObject}
1215 * as follows:
1216 * <blockquote><pre>{@code
1217 s.writeObject(this.returnType());
1218 s.writeObject(this.parameterArray());
1219 * }</pre></blockquote>
1220 * <p>
1221 * The deserialized field values are checked as if they were
1222 * provided to the factory method {@link #methodType(Class,Class[]) methodType}.
1223 * For example, null values, or {@code void} parameter types,
1224 * will lead to exceptions during deserialization.
1225 * @param s the stream to write the object to
1226 * @throws java.io.IOException if there is a problem writing the object
1227 */
1228 @java.io.Serial
1229 private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
1230 s.defaultWriteObject(); // requires serialPersistentFields to be an empty array
1231 s.writeObject(returnType());
1232 s.writeObject(parameterArray());
1233 }
1234
1235 /**
1236 * Reconstitute the {@code MethodType} instance from a stream (that is,
1237 * deserialize it).
1238 * This instance is a scratch object with bogus final fields.
1239 * It provides the parameters to the factory method called by
1240 * {@link #readResolve readResolve}.
1241 * After that call it is discarded.
1242 * @param s the stream to read the object from
1243 * @throws java.io.IOException if there is a problem reading the object
1244 * @throws ClassNotFoundException if one of the component classes cannot be resolved
1245 * @see #readResolve
1246 * @see #writeObject
1247 */
1248 @java.io.Serial
1249 private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
1250 // Assign temporary defaults in case this object escapes
1251 MethodType_init(void.class, NO_PTYPES);
1252
1253 s.defaultReadObject(); // requires serialPersistentFields to be an empty array
1254
1255 Class<?> returnType = (Class<?>) s.readObject();
1256 Class<?>[] parameterArray = (Class<?>[]) s.readObject();
1257 parameterArray = parameterArray.clone(); // make sure it is unshared
1258
1259 // Assign deserialized values
1260 MethodType_init(returnType, parameterArray);
1261 }
1262
1263 // Initialization of state for deserialization only
1264 private void MethodType_init(Class<?> rtype, Class<?>[] ptypes) {
1265 // In order to communicate these values to readResolve, we must
1266 // store them into the implementation-specific final fields.
1267 checkRtype(rtype);
1268 checkPtypes(ptypes);
1269 UNSAFE.putReference(this, OffsetHolder.rtypeOffset, rtype);
1270 UNSAFE.putReference(this, OffsetHolder.ptypesOffset, ptypes);
1271 }
1272
1273 // Support for resetting final fields while deserializing. Implement Holder
1274 // pattern to make the rarely needed offset calculation lazy.
1275 private static class OffsetHolder {
1276 static final long rtypeOffset
1277 = UNSAFE.objectFieldOffset(MethodType.class, "rtype");
1278
1279 static final long ptypesOffset
1280 = UNSAFE.objectFieldOffset(MethodType.class, "ptypes");
1281 }
1282
1283 /**
1284 * Resolves and initializes a {@code MethodType} object
1285 * after serialization.
1286 * @return the fully initialized {@code MethodType} object
1287 */
1288 @java.io.Serial
1289 private Object readResolve() {
1290 // Do not use a trusted path for deserialization:
1291 // return makeImpl(rtype, ptypes, true);
1292 // Verify all operands, and make sure ptypes is unshared:
1293 try {
1294 return methodType(rtype, ptypes);
1295 } finally {
1296 // Re-assign defaults in case this object escapes
1297 MethodType_init(void.class, NO_PTYPES);
1298 }
1299 }
1300
1301 /**
1302 * Simple implementation of weak concurrent intern set.
1303 *
1304 * @param <T> interned type
1305 */
1306 private static class ConcurrentWeakInternSet<T> {
1307
1308 private final ConcurrentMap<WeakEntry<T>, WeakEntry<T>> map;
1309 private final ReferenceQueue<T> stale;
1310
1311 public ConcurrentWeakInternSet() {
1312 this.map = new ConcurrentHashMap<>(512);
1313 this.stale = new ReferenceQueue<>();
1314 }
1315
1316 /**
1317 * Get the existing interned element.
1318 * This method returns null if no element is interned.
1319 *
1320 * @param elem element to look up
1321 * @return the interned element
1322 */
1323 public T get(T elem) {
1324 if (elem == null) throw new NullPointerException();
1325 expungeStaleElements();
1326
1327 WeakEntry<T> value = map.get(elem);
1328 if (value != null) {
1329 T res = value.get();
1330 if (res != null) {
1331 return res;
1332 }
1333 }
1334 return null;
1335 }
1336
1337 /**
1338 * Interns the element.
1339 * Always returns non-null element, matching the one in the intern set.
1340 * Under the race against another add(), it can return <i>different</i>
1341 * element, if another thread beats us to interning it.
1342 *
1343 * @param elem element to add
1344 * @return element that was actually added
1345 */
1346 public T add(T elem) {
1347 if (elem == null) throw new NullPointerException();
1348
1349 // Playing double race here, and so spinloop is required.
1350 // First race is with two concurrent updaters.
1351 // Second race is with GC purging weak ref under our feet.
1352 // Hopefully, we almost always end up with a single pass.
1353 T interned;
1354 WeakEntry<T> e = new WeakEntry<>(elem, stale);
1355 do {
1356 expungeStaleElements();
1357 WeakEntry<T> exist = map.putIfAbsent(e, e);
1358 interned = (exist == null) ? elem : exist.get();
1359 } while (interned == null);
1360 return interned;
1361 }
1362
1363 private void expungeStaleElements() {
1364 Reference<? extends T> reference;
1365 while ((reference = stale.poll()) != null) {
1366 map.remove(reference);
1367 }
1368 }
1369
1370 private static class WeakEntry<T> extends WeakReference<T> {
1371
1372 public final int hashcode;
1373
1374 public WeakEntry(T key, ReferenceQueue<T> queue) {
1375 super(key, queue);
1376 hashcode = key.hashCode();
1377 }
1378
1379 /**
1380 * This implementation returns {@code true} if {@code obj} is another
1381 * {@code WeakEntry} whose referent is equals to this referent, or
1382 * if {@code obj} is equals to the referent of this. This allows
1383 * lookups to be made without wrapping in a {@code WeakEntry}.
1384 *
1385 * @param obj the object to compare
1386 * @return true if {@code obj} is equals to this or the referent of this
1387 * @see MethodType#equals(Object)
1388 * @see Object#equals(Object)
1389 */
1390 @Override
1391 public boolean equals(Object obj) {
1392 Object mine = get();
1393 if (obj instanceof WeakEntry) {
1394 Object that = ((WeakEntry) obj).get();
1395 return (that == null || mine == null) ? (this == obj) : mine.equals(that);
1396 }
1397 return (mine == null) ? (obj == null) : mine.equals(obj);
1398 }
1399
1400 @Override
1401 public int hashCode() {
1402 return hashcode;
1403 }
1404
1405 }
1406 }
1407
1408 }