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