1 /*
2 * Copyright (c) 2008, 2023, 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.function.Supplier;
37 import java.util.List;
38 import java.util.Map;
39 import java.util.NoSuchElementException;
40 import java.util.Objects;
41 import java.util.Optional;
42 import java.util.StringJoiner;
43 import java.util.concurrent.ConcurrentHashMap;
44 import java.util.concurrent.ConcurrentMap;
45 import java.util.stream.Stream;
46
47 import jdk.internal.util.ReferencedKeySet;
48 import jdk.internal.util.ReferenceKey;
49 import jdk.internal.vm.annotation.Stable;
50 import sun.invoke.util.BytecodeDescriptor;
51 import sun.invoke.util.VerifyType;
52 import sun.invoke.util.Wrapper;
53 import sun.security.util.SecurityConstants;
54
55 import static java.lang.invoke.MethodHandleStatics.UNSAFE;
56 import static java.lang.invoke.MethodHandleStatics.newIllegalArgumentException;
57
58 /**
59 * A method type represents the arguments and return type accepted and
60 * returned by a method handle, or the arguments and return type passed
61 * and expected by a method handle caller. Method types must be properly
62 * matched between a method handle and all its callers,
63 * and the JVM's operations enforce this matching at, specifically
64 * during calls to {@link MethodHandle#invokeExact MethodHandle.invokeExact}
65 * and {@link MethodHandle#invoke MethodHandle.invoke}, and during execution
66 * of {@code invokedynamic} instructions.
67 * <p>
68 * The structure is a return type accompanied by any number of parameter types.
69 * The types (primitive, {@code void}, and reference) are represented by {@link Class} objects.
70 * (For ease of exposition, we treat {@code void} as if it were a type.
71 * In fact, it denotes the absence of a return type.)
72 * <p>
73 * All instances of {@code MethodType} are immutable.
74 * Two instances are completely interchangeable if they compare equal.
75 * Equality depends on pairwise correspondence of the return and parameter types and on nothing else.
76 * <p>
77 * This type can be created only by factory methods.
78 * All factory methods may cache values, though caching is not guaranteed.
79 * Some factory methods are static, while others are virtual methods which
80 * modify precursor method types, e.g., by changing a selected parameter.
81 * <p>
82 * Factory methods which operate on groups of parameter types
83 * are systematically presented in two versions, so that both Java arrays and
84 * Java lists can be used to work with groups of parameter types.
85 * The query methods {@code parameterArray} and {@code parameterList}
86 * also provide a choice between arrays and lists.
87 * <p>
88 * {@code MethodType} objects are sometimes derived from bytecode instructions
89 * such as {@code invokedynamic}, specifically from the type descriptor strings associated
90 * with the instructions in a class file's constant pool.
91 * <p>
92 * Like classes and strings, method types can also be represented directly
93 * in a class file's constant pool as constants.
94 * A method type may be loaded by an {@code ldc} instruction which refers
95 * to a suitable {@code CONSTANT_MethodType} constant pool entry.
96 * The entry refers to a {@code CONSTANT_Utf8} spelling for the descriptor string.
97 * (For full details on method type constants, see sections {@jvms
98 * 4.4.8} and {@jvms 5.4.3.5} of the Java Virtual Machine
99 * Specification.)
100 * <p>
101 * When the JVM materializes a {@code MethodType} from a descriptor string,
102 * all classes named in the descriptor must be accessible, and will be loaded.
103 * (But the classes need not be initialized, as is the case with a {@code CONSTANT_Class}.)
104 * This loading may occur at any time before the {@code MethodType} object is first derived.
105 * <p>
106 * <b><a id="descriptor">Nominal Descriptors</a></b>
107 * <p>
108 * A {@code MethodType} can be described in {@linkplain MethodTypeDesc nominal form}
109 * if and only if all of the parameter types and return type can be described
110 * with a {@link Class#describeConstable() nominal descriptor} represented by
111 * {@link ClassDesc}. If a method type can be described nominally, then:
112 * <ul>
113 * <li>The method type has a {@link MethodTypeDesc nominal descriptor}
114 * returned by {@link #describeConstable() MethodType::describeConstable}.</li>
115 * <li>The descriptor string returned by
116 * {@link #descriptorString() MethodType::descriptorString} or
117 * {@link #toMethodDescriptorString() MethodType::toMethodDescriptorString}
118 * for the method type is a method descriptor (JVMS {@jvms 4.3.3}).</li>
119 * </ul>
120 * <p>
121 * If any of the parameter types or return type cannot be described
122 * nominally, i.e. {@link Class#describeConstable() Class::describeConstable}
123 * returns an empty optional for that type,
124 * then the method type cannot be described nominally:
125 * <ul>
126 * <li>The method type has no {@link MethodTypeDesc nominal descriptor} and
127 * {@link #describeConstable() MethodType::describeConstable} returns
128 * an empty optional.</li>
129 * <li>The descriptor string returned by
130 * {@link #descriptorString() MethodType::descriptorString} or
131 * {@link #toMethodDescriptorString() MethodType::toMethodDescriptorString}
132 * for the method type is not a type descriptor.</li>
133 * </ul>
134 *
135 * @author John Rose, JSR 292 EG
136 * @since 1.7
137 */
138 public final
139 class MethodType
140 implements Constable,
141 TypeDescriptor.OfMethod<Class<?>, MethodType>,
142 java.io.Serializable {
143 @java.io.Serial
144 private static final long serialVersionUID = 292L; // {rtype, {ptype...}}
145
146 // The rtype and ptypes fields define the structural identity of the method type:
147 private final @Stable Class<?> rtype;
148 private final @Stable Class<?>[] ptypes;
149
150 // The remaining fields are caches of various sorts:
151 private @Stable MethodTypeForm form; // erased form, plus cached data about primitives
152 private @Stable Object wrapAlt; // alternative wrapped/unwrapped version and
153 // private communication for readObject and readResolve
154 private @Stable Invokers invokers; // cache of handy higher-order adapters
155 private @Stable String methodDescriptor; // cache for toMethodDescriptorString
156
157 /**
158 * Constructor that performs no copying or validation.
159 * Should only be called from the factory method makeImpl
160 */
161 private MethodType(Class<?> rtype, Class<?>[] ptypes) {
162 this.rtype = rtype;
163 this.ptypes = ptypes;
164 }
165
166 /*trusted*/ MethodTypeForm form() { return form; }
167 /*trusted*/ Class<?> rtype() { return rtype; }
168 /*trusted*/ Class<?>[] ptypes() { return ptypes; }
169
170 void setForm(MethodTypeForm f) { form = f; }
171
172 /** This number, mandated by the JVM spec as 255,
173 * is the maximum number of <em>slots</em>
174 * that any Java method can receive in its argument list.
175 * It limits both JVM signatures and method type objects.
176 * The longest possible invocation will look like
177 * {@code staticMethod(arg1, arg2, ..., arg255)} or
178 * {@code x.virtualMethod(arg1, arg2, ..., arg254)}.
179 */
180 /*non-public*/
181 static final int MAX_JVM_ARITY = 255; // this is mandated by the JVM spec.
182
183 /** This number is the maximum arity of a method handle, 254.
184 * It is derived from the absolute JVM-imposed arity by subtracting one,
185 * which is the slot occupied by the method handle itself at the
186 * beginning of the argument list used to invoke the method handle.
187 * The longest possible invocation will look like
188 * {@code mh.invoke(arg1, arg2, ..., arg254)}.
189 */
190 // Issue: Should we allow MH.invokeWithArguments to go to the full 255?
191 /*non-public*/
192 static final int MAX_MH_ARITY = MAX_JVM_ARITY-1; // deduct one for mh receiver
193
194 /** This number is the maximum arity of a method handle invoker, 253.
195 * It is derived from the absolute JVM-imposed arity by subtracting two,
196 * which are the slots occupied by invoke method handle, and the
197 * target method handle, which are both at the beginning of the argument
198 * list used to invoke the target method handle.
199 * The longest possible invocation will look like
200 * {@code invokermh.invoke(targetmh, arg1, arg2, ..., arg253)}.
201 */
202 /*non-public*/
203 static final int MAX_MH_INVOKER_ARITY = MAX_MH_ARITY-1; // deduct one more for invoker
204
205 /** Return number of extra slots (count of long/double args). */
206 private static int checkPtypes(Class<?>[] ptypes) {
207 int slots = 0;
208 for (Class<?> ptype : ptypes) {
209 Objects.requireNonNull(ptype);
210 if (ptype == void.class)
211 throw newIllegalArgumentException("parameter type cannot be void");
212 if (ptype == double.class || ptype == long.class) {
213 slots++;
214 }
215 }
216 checkSlotCount(ptypes.length + slots);
217 return slots;
218 }
219
220 static {
221 // MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work:
222 assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0);
223 }
224 static void checkSlotCount(int count) {
225 if ((count & MAX_JVM_ARITY) != count)
226 throw newIllegalArgumentException("bad parameter count "+count);
227 }
228 private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) {
229 if (num instanceof Integer) num = "bad index: "+num;
230 return new IndexOutOfBoundsException(num.toString());
231 }
232
233 static final ReferencedKeySet<MethodType> internTable =
234 ReferencedKeySet.create(false, true, new Supplier<>() {
235 @Override
236 public Map<ReferenceKey<MethodType>, ReferenceKey<MethodType>> get() {
237 return new ConcurrentHashMap<>(512);
238 }
239 });
240
241 static final Class<?>[] NO_PTYPES = {};
242
243 /**
244 * Finds or creates an instance of the given method type.
245 * @param rtype the return type
246 * @param ptypes the parameter types
247 * @return a method type with the given components
248 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
249 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
250 */
251 public static MethodType methodType(Class<?> rtype, Class<?>[] ptypes) {
252 return methodType(rtype, ptypes, false);
253 }
254
255 /**
256 * Finds or creates a method type with the given components.
257 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
258 * @param rtype the return type
259 * @param ptypes the parameter types
260 * @return a method type with the given components
261 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
262 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
263 */
264 public static MethodType methodType(Class<?> rtype, List<Class<?>> ptypes) {
265 boolean notrust = false; // random List impl. could return evil ptypes array
266 return methodType(rtype, listToArray(ptypes), notrust);
267 }
268
269 private static Class<?>[] listToArray(List<Class<?>> ptypes) {
270 // sanity check the size before the toArray call, since size might be huge
271 checkSlotCount(ptypes.size());
272 return ptypes.toArray(NO_PTYPES);
273 }
274
275 /**
276 * Finds or creates a method type with the given components.
277 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
278 * The leading parameter type is prepended to the remaining array.
279 * @param rtype the return type
280 * @param ptype0 the first parameter type
281 * @param ptypes the remaining parameter types
282 * @return a method type with the given components
283 * @throws NullPointerException if {@code rtype} or {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is null
284 * @throws IllegalArgumentException if {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is {@code void.class}
285 */
286 public static MethodType methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes) {
287 int len = ptypes.length;
288 if (rtype == Object.class && ptype0 == Object.class) {
289 if (len == 0) {
290 return genericMethodType(1, false);
291 }
292 if (isAllObject(ptypes, len - 1)) {
293 Class<?> lastParam = ptypes[len - 1];
294 if (lastParam == Object.class) {
295 return genericMethodType(len + 1, false);
296 } else if (lastParam == Object[].class) {
297 return genericMethodType(len, true);
298 }
299 }
300 }
301 Class<?>[] ptypes1 = new Class<?>[1 + len];
302 ptypes1[0] = ptype0;
303 System.arraycopy(ptypes, 0, ptypes1, 1, len);
304 return makeImpl(rtype, ptypes1, true);
305 }
306
307 /**
308 * Finds or creates a method type with the given components.
309 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
310 * The resulting method has no parameter types.
311 * @param rtype the return type
312 * @return a method type with the given return value
313 * @throws NullPointerException if {@code rtype} is null
314 */
315 public static MethodType methodType(Class<?> rtype) {
316 if (rtype == Object.class) {
317 return genericMethodType(0, false);
318 }
319 return makeImpl(rtype, NO_PTYPES, true);
320 }
321
322 /**
323 * Finds or creates a method type with the given components.
324 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
325 * The resulting method has the single given parameter type.
326 * @param rtype the return type
327 * @param ptype0 the parameter type
328 * @return a method type with the given return value and parameter type
329 * @throws NullPointerException if {@code rtype} or {@code ptype0} is null
330 * @throws IllegalArgumentException if {@code ptype0} is {@code void.class}
331 */
332 public static MethodType methodType(Class<?> rtype, Class<?> ptype0) {
333 if (rtype == Object.class) {
334 if (ptype0 == Object.class) {
335 return genericMethodType(1, false);
336 } else if (ptype0 == Object[].class) {
337 return genericMethodType(0, true);
338 }
339 }
340 return makeImpl(rtype, new Class<?>[]{ ptype0 }, true);
341 }
342
343 /**
344 * Finds or creates a method type with the given components.
345 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
346 * The resulting method has the same parameter types as {@code ptypes},
347 * and the specified return type.
348 * @param rtype the return type
349 * @param ptypes the method type which supplies the parameter types
350 * @return a method type with the given components
351 * @throws NullPointerException if {@code rtype} or {@code ptypes} is null
352 */
353 public static MethodType methodType(Class<?> rtype, MethodType ptypes) {
354 return methodType(rtype, ptypes.ptypes, true);
355 }
356
357 private static boolean isAllObject(Class<?>[] ptypes, int to) {
358 for (int i = 0; i < to; i++) {
359 if (ptypes[i] != Object.class) {
360 return false;
361 }
362 }
363 return true;
364 }
365
366 /*trusted*/
367 static MethodType methodType(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {
368 if (rtype == Object.class) {
369 int last = ptypes.length - 1;
370 if (last < 0) {
371 return genericMethodType(0, false);
372 }
373 if (isAllObject(ptypes, last)) {
374 Class<?> lastParam = ptypes[last];
375 if (lastParam == Object.class) {
376 return genericMethodType(last + 1, false);
377 } else if (lastParam == Object[].class) {
378 return genericMethodType(last, true);
379 }
380 }
381 }
382 return makeImpl(rtype, ptypes, trusted);
383 }
384
385 /**
386 * Sole factory method to find or create an interned method type. Will perform
387 * input validation on behalf of factory methods
388 *
389 * @param rtype desired return type
390 * @param ptypes desired parameter types
391 * @param trusted whether the ptypes can be used without cloning
392 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
393 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
394 * @return the unique method type of the desired structure
395 */
396 private static MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {
397 if (ptypes.length == 0) {
398 ptypes = NO_PTYPES; trusted = true;
399 }
400 MethodType primordialMT = new MethodType(rtype, ptypes);
401 MethodType mt = internTable.get(primordialMT);
402 if (mt != null)
403 return mt;
404
405 // promote the object to the Real Thing, and reprobe
406 Objects.requireNonNull(rtype);
407 if (trusted) {
408 MethodType.checkPtypes(ptypes);
409 mt = primordialMT;
410 } else {
411 // Make defensive copy then validate
412 ptypes = Arrays.copyOf(ptypes, ptypes.length);
413 MethodType.checkPtypes(ptypes);
414 mt = new MethodType(rtype, ptypes);
415 }
416 mt.form = MethodTypeForm.findForm(mt);
417 return internTable.intern(mt);
418 }
419 private static final @Stable MethodType[] objectOnlyTypes = new MethodType[20];
420
421 /**
422 * Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array.
423 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
424 * All parameters and the return type will be {@code Object},
425 * except the final array parameter if any, which will be {@code Object[]}.
426 * @param objectArgCount number of parameters (excluding the final array parameter if any)
427 * @param finalArray whether there will be a trailing array parameter, of type {@code Object[]}
428 * @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments
429 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true)
430 * @see #genericMethodType(int)
431 */
432 public static MethodType genericMethodType(int objectArgCount, boolean finalArray) {
433 MethodType mt;
434 checkSlotCount(objectArgCount);
435 int ivarargs = (!finalArray ? 0 : 1);
436 int ootIndex = objectArgCount*2 + ivarargs;
437 if (ootIndex < objectOnlyTypes.length) {
438 mt = objectOnlyTypes[ootIndex];
439 if (mt != null) return mt;
440 }
441 Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs];
442 Arrays.fill(ptypes, Object.class);
443 if (ivarargs != 0) ptypes[objectArgCount] = Object[].class;
444 mt = makeImpl(Object.class, ptypes, true);
445 if (ootIndex < objectOnlyTypes.length) {
446 objectOnlyTypes[ootIndex] = mt; // cache it here also!
447 }
448 return mt;
449 }
450
451 /**
452 * Finds or creates a method type whose components are all {@code Object}.
453 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
454 * All parameters and the return type will be Object.
455 * @param objectArgCount number of parameters
456 * @return a generally applicable method type, for all calls of the given argument count
457 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255
458 * @see #genericMethodType(int, boolean)
459 */
460 public static MethodType genericMethodType(int objectArgCount) {
461 return genericMethodType(objectArgCount, false);
462 }
463
464 /**
465 * Finds or creates a method type with a single different parameter type.
466 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
467 * @param num the index (zero-based) of the parameter type to change
468 * @param nptype a new parameter type to replace the old one with
469 * @return the same type, except with the selected parameter changed
470 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
471 * @throws IllegalArgumentException if {@code nptype} is {@code void.class}
472 * @throws NullPointerException if {@code nptype} is null
473 */
474 public MethodType changeParameterType(int num, Class<?> nptype) {
475 if (parameterType(num) == nptype) return this;
476 Class<?>[] nptypes = ptypes.clone();
477 nptypes[num] = nptype;
478 return makeImpl(rtype, nptypes, true);
479 }
480
481 /**
482 * Finds or creates a method type with additional parameter types.
483 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
484 * @param num the position (zero-based) of the inserted parameter type(s)
485 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
486 * @return the same type, except with the selected parameter(s) inserted
487 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
488 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
489 * or if the resulting method type would have more than 255 parameter slots
490 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
491 */
492 public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) {
493 int len = ptypes.length;
494 if (num < 0 || num > len)
495 throw newIndexOutOfBoundsException(num);
496 int ins = checkPtypes(ptypesToInsert);
497 checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins);
498 int ilen = ptypesToInsert.length;
499 if (ilen == 0) return this;
500 Class<?>[] nptypes = new Class<?>[len + ilen];
501 if (num > 0) {
502 System.arraycopy(ptypes, 0, nptypes, 0, num);
503 }
504 System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen);
505 if (num < len) {
506 System.arraycopy(ptypes, num, nptypes, num+ilen, len-num);
507 }
508 return makeImpl(rtype, nptypes, true);
509 }
510
511 /**
512 * Finds or creates a method type with additional parameter types.
513 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
514 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
515 * @return the same type, except with the selected parameter(s) appended
516 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
517 * or if the resulting method type would have more than 255 parameter slots
518 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
519 */
520 public MethodType appendParameterTypes(Class<?>... ptypesToInsert) {
521 return insertParameterTypes(parameterCount(), ptypesToInsert);
522 }
523
524 /**
525 * Finds or creates a method type with additional parameter types.
526 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
527 * @param num the position (zero-based) of the inserted parameter type(s)
528 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
529 * @return the same type, except with the selected parameter(s) inserted
530 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
531 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
532 * or if the resulting method type would have more than 255 parameter slots
533 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
534 */
535 public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) {
536 return insertParameterTypes(num, listToArray(ptypesToInsert));
537 }
538
539 /**
540 * Finds or creates a method type with additional parameter types.
541 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
542 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
543 * @return the same type, except with the selected parameter(s) appended
544 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
545 * or if the resulting method type would have more than 255 parameter slots
546 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
547 */
548 public MethodType appendParameterTypes(List<Class<?>> ptypesToInsert) {
549 return insertParameterTypes(parameterCount(), ptypesToInsert);
550 }
551
552 /**
553 * Finds or creates a method type with modified parameter types.
554 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
555 * @param start the position (zero-based) of the first replaced parameter type(s)
556 * @param end the position (zero-based) after the last replaced parameter type(s)
557 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
558 * @return the same type, except with the selected parameter(s) replaced
559 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
560 * or if {@code end} is negative or greater than {@code parameterCount()}
561 * or if {@code start} is greater than {@code end}
562 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
563 * or if the resulting method type would have more than 255 parameter slots
564 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
565 */
566 /*non-public*/
567 MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) {
568 if (start == end)
569 return insertParameterTypes(start, ptypesToInsert);
570 int len = ptypes.length;
571 if (!(0 <= start && start <= end && end <= len))
572 throw newIndexOutOfBoundsException("start="+start+" end="+end);
573 int ilen = ptypesToInsert.length;
574 if (ilen == 0)
575 return dropParameterTypes(start, end);
576 return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert);
577 }
578
579 /** Replace the last arrayLength parameter types with the component type of arrayType.
580 * @param arrayType any array type
581 * @param pos position at which to spread
582 * @param arrayLength the number of parameter types to change
583 * @return the resulting type
584 */
585 /*non-public*/
586 MethodType asSpreaderType(Class<?> arrayType, int pos, int arrayLength) {
587 assert(parameterCount() >= arrayLength);
588 int spreadPos = pos;
589 if (arrayLength == 0) return this; // nothing to change
590 if (arrayType == Object[].class) {
591 if (isGeneric()) return this; // nothing to change
592 if (spreadPos == 0) {
593 // no leading arguments to preserve; go generic
594 MethodType res = genericMethodType(arrayLength);
595 if (rtype != Object.class) {
596 res = res.changeReturnType(rtype);
597 }
598 return res;
599 }
600 }
601 Class<?> elemType = arrayType.getComponentType();
602 assert(elemType != null);
603 for (int i = spreadPos; i < spreadPos + arrayLength; i++) {
604 if (ptypes[i] != elemType) {
605 Class<?>[] fixedPtypes = ptypes.clone();
606 Arrays.fill(fixedPtypes, i, spreadPos + arrayLength, elemType);
607 return methodType(rtype, fixedPtypes);
608 }
609 }
610 return this; // arguments check out; no change
611 }
612
613 /** Return the leading parameter type, which must exist and be a reference.
614 * @return the leading parameter type, after error checks
615 */
616 /*non-public*/
617 Class<?> leadingReferenceParameter() {
618 Class<?> ptype;
619 if (ptypes.length == 0 ||
620 (ptype = ptypes[0]).isPrimitive())
621 throw newIllegalArgumentException("no leading reference parameter");
622 return ptype;
623 }
624
625 /** Delete the last parameter type and replace it with arrayLength copies of the component type of arrayType.
626 * @param arrayType any array type
627 * @param pos position at which to insert parameters
628 * @param arrayLength the number of parameter types to insert
629 * @return the resulting type
630 */
631 /*non-public*/
632 MethodType asCollectorType(Class<?> arrayType, int pos, int arrayLength) {
633 assert(parameterCount() >= 1);
634 assert(pos < ptypes.length);
635 assert(ptypes[pos].isAssignableFrom(arrayType));
636 MethodType res;
637 if (arrayType == Object[].class) {
638 res = genericMethodType(arrayLength);
639 if (rtype != Object.class) {
640 res = res.changeReturnType(rtype);
641 }
642 } else {
643 Class<?> elemType = arrayType.getComponentType();
644 assert(elemType != null);
645 res = methodType(rtype, Collections.nCopies(arrayLength, elemType));
646 }
647 if (ptypes.length == 1) {
648 return res;
649 } else {
650 // insert after (if need be), then before
651 if (pos < ptypes.length - 1) {
652 res = res.insertParameterTypes(arrayLength, Arrays.copyOfRange(ptypes, pos + 1, ptypes.length));
653 }
654 return res.insertParameterTypes(0, Arrays.copyOf(ptypes, pos));
655 }
656 }
657
658 /**
659 * Finds or creates a method type with some parameter types omitted.
660 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
661 * @param start the index (zero-based) of the first parameter type to remove
662 * @param end the index (greater than {@code start}) of the first parameter type after not to remove
663 * @return the same type, except with the selected parameter(s) removed
664 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
665 * or if {@code end} is negative or greater than {@code parameterCount()}
666 * or if {@code start} is greater than {@code end}
667 */
668 public MethodType dropParameterTypes(int start, int end) {
669 int len = ptypes.length;
670 if (!(0 <= start && start <= end && end <= len))
671 throw newIndexOutOfBoundsException("start="+start+" end="+end);
672 if (start == end) return this;
673 Class<?>[] nptypes;
674 if (start == 0) {
675 if (end == len) {
676 // drop all parameters
677 nptypes = NO_PTYPES;
678 } else {
679 // drop initial parameter(s)
680 nptypes = Arrays.copyOfRange(ptypes, end, len);
681 }
682 } else {
683 if (end == len) {
684 // drop trailing parameter(s)
685 nptypes = Arrays.copyOfRange(ptypes, 0, start);
686 } else {
687 int tail = len - end;
688 nptypes = Arrays.copyOfRange(ptypes, 0, start + tail);
689 System.arraycopy(ptypes, end, nptypes, start, tail);
690 }
691 }
692 return methodType(rtype, nptypes, true);
693 }
694
695 /**
696 * Finds or creates a method type with a different return type.
697 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
698 * @param nrtype a return parameter type to replace the old one with
699 * @return the same type, except with the return type change
700 * @throws NullPointerException if {@code nrtype} is null
701 */
702 public MethodType changeReturnType(Class<?> nrtype) {
703 if (returnType() == nrtype) return this;
704 return methodType(nrtype, ptypes, true);
705 }
706
707 /**
708 * Reports if this type contains a primitive argument or return value.
709 * The return type {@code void} counts as a primitive.
710 * @return true if any of the types are primitives
711 */
712 public boolean hasPrimitives() {
713 return form.hasPrimitives();
714 }
715
716 /**
717 * Reports if this type contains a wrapper argument or return value.
718 * Wrappers are types which box primitive values, such as {@link Integer}.
719 * The reference type {@code java.lang.Void} counts as a wrapper,
720 * if it occurs as a return type.
721 * @return true if any of the types are wrappers
722 */
723 public boolean hasWrappers() {
724 return unwrap() != this;
725 }
726
727 /**
728 * Erases all reference types to {@code Object}.
729 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
730 * All primitive types (including {@code void}) will remain unchanged.
731 * @return a version of the original type with all reference types replaced
732 */
733 public MethodType erase() {
734 return form.erasedType();
735 }
736
737 /**
738 * Erases all reference types to {@code Object}, and all subword types to {@code int}.
739 * This is the reduced type polymorphism used by private methods
740 * such as {@link MethodHandle#invokeBasic invokeBasic}.
741 * @return a version of the original type with all reference and subword types replaced
742 */
743 /*non-public*/
744 MethodType basicType() {
745 return form.basicType();
746 }
747
748 private static final @Stable Class<?>[] METHOD_HANDLE_ARRAY
749 = new Class<?>[] { MethodHandle.class };
750
751 /**
752 * @return a version of the original type with MethodHandle prepended as the first argument
753 */
754 /*non-public*/
755 MethodType invokerType() {
756 return insertParameterTypes(0, METHOD_HANDLE_ARRAY);
757 }
758
759 /**
760 * Converts all types, both reference and primitive, to {@code Object}.
761 * Convenience method for {@link #genericMethodType(int) genericMethodType}.
762 * The expression {@code type.wrap().erase()} produces the same value
763 * as {@code type.generic()}.
764 * @return a version of the original type with all types replaced
765 */
766 public MethodType generic() {
767 return genericMethodType(parameterCount());
768 }
769
770 /*non-public*/
771 boolean isGeneric() {
772 return this == erase() && !hasPrimitives();
773 }
774
775 /**
776 * Converts all primitive types to their corresponding wrapper types.
777 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
778 * All reference types (including wrapper types) will remain unchanged.
779 * A {@code void} return type is changed to the type {@code java.lang.Void}.
780 * The expression {@code type.wrap().erase()} produces the same value
781 * as {@code type.generic()}.
782 * @return a version of the original type with all primitive types replaced
783 */
784 public MethodType wrap() {
785 return hasPrimitives() ? wrapWithPrims(this) : this;
786 }
787
788 /**
789 * Converts all wrapper types to their corresponding primitive types.
790 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
791 * All primitive types (including {@code void}) will remain unchanged.
792 * A return type of {@code java.lang.Void} is changed to {@code void}.
793 * @return a version of the original type with all wrapper types replaced
794 */
795 public MethodType unwrap() {
796 MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this);
797 return unwrapWithNoPrims(noprims);
798 }
799
800 private static MethodType wrapWithPrims(MethodType pt) {
801 assert(pt.hasPrimitives());
802 MethodType wt = (MethodType)pt.wrapAlt;
803 if (wt == null) {
804 // fill in lazily
805 wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP);
806 assert(wt != null);
807 pt.wrapAlt = wt;
808 }
809 return wt;
810 }
811
812 private static MethodType unwrapWithNoPrims(MethodType wt) {
813 assert(!wt.hasPrimitives());
814 MethodType uwt = (MethodType)wt.wrapAlt;
815 if (uwt == null) {
816 // fill in lazily
817 uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP);
818 if (uwt == null)
819 uwt = wt; // type has no wrappers or prims at all
820 wt.wrapAlt = uwt;
821 }
822 return uwt;
823 }
824
825 /**
826 * Returns the parameter type at the specified index, within this method type.
827 * @param num the index (zero-based) of the desired parameter type
828 * @return the selected parameter type
829 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
830 */
831 public Class<?> parameterType(int num) {
832 return ptypes[num];
833 }
834 /**
835 * Returns the number of parameter types in this method type.
836 * @return the number of parameter types
837 */
838 public int parameterCount() {
839 return ptypes.length;
840 }
841 /**
842 * Returns the return type of this method type.
843 * @return the return type
844 */
845 public Class<?> returnType() {
846 return rtype;
847 }
848
849 /**
850 * Presents the parameter types as a list (a convenience method).
851 * The list will be immutable.
852 * @return the parameter types (as an immutable list)
853 */
854 public List<Class<?>> parameterList() {
855 return List.of(ptypes);
856 }
857
858 /**
859 * Returns the last parameter type of this method type.
860 * If this type has no parameters, the sentinel value
861 * {@code void.class} is returned instead.
862 * @apiNote
863 * <p>
864 * The sentinel value is chosen so that reflective queries can be
865 * made directly against the result value.
866 * The sentinel value cannot be confused with a real parameter,
867 * since {@code void} is never acceptable as a parameter type.
868 * For variable arity invocation modes, the expression
869 * {@link Class#getComponentType lastParameterType().getComponentType()}
870 * is useful to query the type of the "varargs" parameter.
871 * @return the last parameter type if any, else {@code void.class}
872 * @since 10
873 */
874 public Class<?> lastParameterType() {
875 int len = ptypes.length;
876 return len == 0 ? void.class : ptypes[len-1];
877 }
878
879 /**
880 * Presents the parameter types as an array (a convenience method).
881 * Changes to the array will not result in changes to the type.
882 * @return the parameter types (as a fresh copy if necessary)
883 */
884 public Class<?>[] parameterArray() {
885 return ptypes.clone();
886 }
887
888 /**
889 * Compares the specified object with this type for equality.
890 * That is, it returns {@code true} if and only if the specified object
891 * is also a method type with exactly the same parameters and return type.
892 * @param x object to compare
893 * @see Object#equals(Object)
894 */
895 @Override
896 public boolean equals(Object x) {
897 if (this == x) {
898 return true;
899 }
900 if (x instanceof MethodType mt) {
901 return equals(mt);
902 }
903 return false;
904 }
905
906 private boolean equals(MethodType that) {
907 return this.rtype == that.rtype
908 && Arrays.equals(this.ptypes, that.ptypes);
909 }
910
911 /**
912 * Returns the hash code value for this method type.
913 * It is defined to be the same as the hashcode of a List
914 * whose elements are the return type followed by the
915 * parameter types.
916 * @return the hash code value for this method type
917 * @see Object#hashCode()
918 * @see #equals(Object)
919 * @see List#hashCode()
920 */
921 @Override
922 public int hashCode() {
923 int hashCode = 31 + rtype.hashCode();
924 for (Class<?> ptype : ptypes)
925 hashCode = 31 * hashCode + ptype.hashCode();
926 return hashCode;
927 }
928
929 /**
930 * Returns a string representation of the method type,
931 * of the form {@code "(PT0,PT1...)RT"}.
932 * The string representation of a method type is a
933 * parenthesis enclosed, comma separated list of type names,
934 * followed immediately by the return type.
935 * <p>
936 * Each type is represented by its
937 * {@link java.lang.Class#getSimpleName simple name}.
938 */
939 @Override
940 public String toString() {
941 StringJoiner sj = new StringJoiner(",", "(",
942 ")" + rtype.getSimpleName());
943 for (int i = 0; i < ptypes.length; i++) {
944 sj.add(ptypes[i].getSimpleName());
945 }
946 return sj.toString();
947 }
948
949 /** True if my parameter list is effectively identical to the given full list,
950 * after skipping the given number of my own initial parameters.
951 * In other words, after disregarding {@code skipPos} parameters,
952 * my remaining parameter list is no longer than the {@code fullList}, and
953 * is equal to the same-length initial sublist of {@code fullList}.
954 */
955 /*non-public*/
956 boolean effectivelyIdenticalParameters(int skipPos, List<Class<?>> fullList) {
957 int myLen = ptypes.length, fullLen = fullList.size();
958 if (skipPos > myLen || myLen - skipPos > fullLen)
959 return false;
960 List<Class<?>> myList = Arrays.asList(ptypes);
961 if (skipPos != 0) {
962 myList = myList.subList(skipPos, myLen);
963 myLen -= skipPos;
964 }
965 if (fullLen == myLen)
966 return myList.equals(fullList);
967 else
968 return myList.equals(fullList.subList(0, myLen));
969 }
970
971 /** True if the old return type can always be viewed (w/o casting) under new return type,
972 * and the new parameters can be viewed (w/o casting) under the old parameter types.
973 */
974 /*non-public*/
975 boolean isViewableAs(MethodType newType, boolean keepInterfaces) {
976 if (!VerifyType.isNullConversion(returnType(), newType.returnType(), keepInterfaces))
977 return false;
978 if (form == newType.form && form.erasedType == this)
979 return true; // my reference parameters are all Object
980 if (ptypes == newType.ptypes)
981 return true;
982 int argc = parameterCount();
983 if (argc != newType.parameterCount())
984 return false;
985 for (int i = 0; i < argc; i++) {
986 if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i), keepInterfaces))
987 return false;
988 }
989 return true;
990 }
991 /*non-public*/
992 boolean isConvertibleTo(MethodType newType) {
993 MethodTypeForm oldForm = this.form();
994 MethodTypeForm newForm = newType.form();
995 if (oldForm == newForm)
996 // same parameter count, same primitive/object mix
997 return true;
998 if (!canConvert(returnType(), newType.returnType()))
999 return false;
1000 Class<?>[] srcTypes = newType.ptypes;
1001 Class<?>[] dstTypes = ptypes;
1002 if (srcTypes == dstTypes)
1003 return true;
1004 int argc;
1005 if ((argc = srcTypes.length) != dstTypes.length)
1006 return false;
1007 if (argc <= 1) {
1008 if (argc == 1 && !canConvert(srcTypes[0], dstTypes[0]))
1009 return false;
1010 return true;
1011 }
1012 if ((!oldForm.hasPrimitives() && oldForm.erasedType == this) ||
1013 (!newForm.hasPrimitives() && newForm.erasedType == newType)) {
1014 // Somewhat complicated test to avoid a loop of 2 or more trips.
1015 // If either type has only Object parameters, we know we can convert.
1016 assert(canConvertParameters(srcTypes, dstTypes));
1017 return true;
1018 }
1019 return canConvertParameters(srcTypes, dstTypes);
1020 }
1021
1022 /** Returns true if MHs.explicitCastArguments produces the same result as MH.asType.
1023 * If the type conversion is impossible for either, the result should be false.
1024 */
1025 /*non-public*/
1026 boolean explicitCastEquivalentToAsType(MethodType newType) {
1027 if (this == newType) return true;
1028 if (!explicitCastEquivalentToAsType(rtype, newType.rtype)) {
1029 return false;
1030 }
1031 Class<?>[] srcTypes = newType.ptypes;
1032 Class<?>[] dstTypes = ptypes;
1033 if (dstTypes == srcTypes) {
1034 return true;
1035 }
1036 assert(dstTypes.length == srcTypes.length);
1037 for (int i = 0; i < dstTypes.length; i++) {
1038 if (!explicitCastEquivalentToAsType(srcTypes[i], dstTypes[i])) {
1039 return false;
1040 }
1041 }
1042 return true;
1043 }
1044
1045 /** Reports true if the src can be converted to the dst, by both asType and MHs.eCE,
1046 * and with the same effect.
1047 * MHs.eCA has the following "upgrades" to MH.asType:
1048 * 1. interfaces are unchecked (that is, treated as if aliased to Object)
1049 * Therefore, {@code Object->CharSequence} is possible in both cases but has different semantics
1050 * 2. the full matrix of primitive-to-primitive conversions is supported
1051 * Narrowing like {@code long->byte} and basic-typing like {@code boolean->int}
1052 * are not supported by asType, but anything supported by asType is equivalent
1053 * with MHs.eCE.
1054 * 3a. unboxing conversions can be followed by the full matrix of primitive conversions
1055 * 3b. unboxing of null is permitted (creates a zero primitive value)
1056 * Other than interfaces, reference-to-reference conversions are the same.
1057 * Boxing primitives to references is the same for both operators.
1058 */
1059 private static boolean explicitCastEquivalentToAsType(Class<?> src, Class<?> dst) {
1060 if (src == dst || dst == Object.class || dst == void.class) return true;
1061 if (src.isPrimitive()) {
1062 // Could be a prim/prim conversion, where casting is a strict superset.
1063 // Or a boxing conversion, which is always to an exact wrapper class.
1064 return canConvert(src, dst);
1065 } else if (dst.isPrimitive()) {
1066 // Unboxing behavior is different between MHs.eCA & MH.asType (see 3b).
1067 return false;
1068 } else {
1069 // R->R always works, but we have to avoid a check-cast to an interface.
1070 return !dst.isInterface() || dst.isAssignableFrom(src);
1071 }
1072 }
1073
1074 private boolean canConvertParameters(Class<?>[] srcTypes, Class<?>[] dstTypes) {
1075 for (int i = 0; i < srcTypes.length; i++) {
1076 if (!canConvert(srcTypes[i], dstTypes[i])) {
1077 return false;
1078 }
1079 }
1080 return true;
1081 }
1082
1083 /*non-public*/
1084 static boolean canConvert(Class<?> src, Class<?> dst) {
1085 // short-circuit a few cases:
1086 if (src == dst || src == Object.class || dst == Object.class) return true;
1087 // the remainder of this logic is documented in MethodHandle.asType
1088 if (src.isPrimitive()) {
1089 // can force void to an explicit null, a la reflect.Method.invoke
1090 // can also force void to a primitive zero, by analogy
1091 if (src == void.class) return true; //or !dst.isPrimitive()?
1092 Wrapper sw = Wrapper.forPrimitiveType(src);
1093 if (dst.isPrimitive()) {
1094 // P->P must widen
1095 return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw);
1096 } else {
1097 // P->R must box and widen
1098 return dst.isAssignableFrom(sw.wrapperType());
1099 }
1100 } else if (dst.isPrimitive()) {
1101 // any value can be dropped
1102 if (dst == void.class) return true;
1103 Wrapper dw = Wrapper.forPrimitiveType(dst);
1104 // R->P must be able to unbox (from a dynamically chosen type) and widen
1105 // For example:
1106 // Byte/Number/Comparable/Object -> dw:Byte -> byte.
1107 // Character/Comparable/Object -> dw:Character -> char
1108 // Boolean/Comparable/Object -> dw:Boolean -> boolean
1109 // This means that dw must be cast-compatible with src.
1110 if (src.isAssignableFrom(dw.wrapperType())) {
1111 return true;
1112 }
1113 // The above does not work if the source reference is strongly typed
1114 // to a wrapper whose primitive must be widened. For example:
1115 // Byte -> unbox:byte -> short/int/long/float/double
1116 // Character -> unbox:char -> int/long/float/double
1117 if (Wrapper.isWrapperType(src) &&
1118 dw.isConvertibleFrom(Wrapper.forWrapperType(src))) {
1119 // can unbox from src and then widen to dst
1120 return true;
1121 }
1122 // We have already covered cases which arise due to runtime unboxing
1123 // of a reference type which covers several wrapper types:
1124 // Object -> cast:Integer -> unbox:int -> long/float/double
1125 // Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double
1126 // An marginal case is Number -> dw:Character -> char, which would be OK if there were a
1127 // subclass of Number which wraps a value that can convert to char.
1128 // Since there is none, we don't need an extra check here to cover char or boolean.
1129 return false;
1130 } else {
1131 // R->R always works, since null is always valid dynamically
1132 return true;
1133 }
1134 }
1135
1136 /// Queries which have to do with the bytecode architecture
1137
1138 /** Reports the number of JVM stack slots required to invoke a method
1139 * of this type. Note that (for historical reasons) the JVM requires
1140 * a second stack slot to pass long and double arguments.
1141 * So this method returns {@link #parameterCount() parameterCount} plus the
1142 * number of long and double parameters (if any).
1143 * <p>
1144 * This method is included for the benefit of applications that must
1145 * generate bytecodes that process method handles and invokedynamic.
1146 * @return the number of JVM stack slots for this type's parameters
1147 */
1148 /*non-public*/
1149 int parameterSlotCount() {
1150 return form.parameterSlotCount();
1151 }
1152
1153 /*non-public*/
1154 Invokers invokers() {
1155 Invokers inv = invokers;
1156 if (inv != null) return inv;
1157 invokers = inv = new Invokers(this);
1158 return inv;
1159 }
1160
1161 /**
1162 * Finds or creates an instance of a method type of the given method descriptor
1163 * (JVMS {@jvms 4.3.3}). This method is a convenience method for
1164 * {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
1165 * Any class or interface name embedded in the descriptor string will be
1166 * resolved by the given loader (or if it is {@code null}, on the system class loader).
1167 *
1168 * @apiNote
1169 * It is possible to encounter method types that have valid descriptors but
1170 * cannot be constructed by this method, because their component types are
1171 * not visible from a common class loader.
1172 * <p>
1173 * This method is included for the benefit of applications that must
1174 * generate bytecodes that process method handles and {@code invokedynamic}.
1175 * @param descriptor a method descriptor string
1176 * @param loader the class loader in which to look up the types
1177 * @return a method type of the given method descriptor
1178 * @throws NullPointerException if the string is {@code null}
1179 * @throws IllegalArgumentException if the string is not a method descriptor
1180 * @throws TypeNotPresentException if a named type cannot be found
1181 * @throws SecurityException if the security manager is present and
1182 * {@code loader} is {@code null} and the caller does not have the
1183 * {@link RuntimePermission}{@code ("getClassLoader")}
1184 * @jvms 4.3.3 Method Descriptors
1185 */
1186 public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader)
1187 throws IllegalArgumentException, TypeNotPresentException
1188 {
1189 if (loader == null) {
1190 @SuppressWarnings("removal")
1191 SecurityManager sm = System.getSecurityManager();
1192 if (sm != null) {
1193 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
1194 }
1195 }
1196 return fromDescriptor(descriptor,
1197 (loader == null) ? ClassLoader.getSystemClassLoader() : loader);
1198 }
1199
1200 /**
1201 * Same as {@link #fromMethodDescriptorString(String, ClassLoader)}, but
1202 * {@code null} ClassLoader means the bootstrap loader is used here.
1203 * <p>
1204 * IMPORTANT: This method is preferable for JDK internal use as it more
1205 * correctly interprets {@code null} ClassLoader than
1206 * {@link #fromMethodDescriptorString(String, ClassLoader)}.
1207 * Use of this method also avoids early initialization issues when system
1208 * ClassLoader is not initialized yet.
1209 */
1210 static MethodType fromDescriptor(String descriptor, ClassLoader loader)
1211 throws IllegalArgumentException, TypeNotPresentException
1212 {
1213 if (!descriptor.startsWith("(") || // also generates NPE if needed
1214 descriptor.indexOf(')') < 0 ||
1215 descriptor.indexOf('.') >= 0)
1216 throw newIllegalArgumentException("not a method descriptor: "+descriptor);
1217 List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader);
1218 Class<?> rtype = types.remove(types.size() - 1);
1219 Class<?>[] ptypes = listToArray(types);
1220 return methodType(rtype, ptypes, true);
1221 }
1222
1223 /**
1224 * {@return the descriptor string for this method type} This method
1225 * is equivalent to calling {@link #descriptorString() MethodType::descriptorString}.
1226 *
1227 * @apiNote
1228 * This is not a strict inverse of {@link #fromMethodDescriptorString
1229 * fromMethodDescriptorString} which requires a method type descriptor
1230 * (JVMS {@jvms 4.3.3}) and a suitable class loader argument.
1231 * Two distinct {@code MethodType} objects can have an identical
1232 * descriptor string as distinct classes can have the same name
1233 * but different class loaders.
1234 *
1235 * <p>
1236 * This method is included for the benefit of applications that must
1237 * generate bytecodes that process method handles and {@code invokedynamic}.
1238 * @jvms 4.3.3 Method Descriptors
1239 * @see <a href="#descriptor">Nominal Descriptor for {@code MethodType}</a>
1240 */
1241 public String toMethodDescriptorString() {
1242 String desc = methodDescriptor;
1243 if (desc == null) {
1244 desc = BytecodeDescriptor.unparseMethod(this.rtype, this.ptypes);
1245 methodDescriptor = desc;
1246 }
1247 return desc;
1248 }
1249
1250 /**
1251 * {@return the descriptor string for this method type}
1252 *
1253 * <p>
1254 * If this method type can be {@linkplain ##descriptor described nominally},
1255 * then the result is a method type descriptor (JVMS {@jvms 4.3.3}).
1256 * {@link MethodTypeDesc MethodTypeDesc} for this method type
1257 * can be produced by calling {@link MethodTypeDesc#ofDescriptor(String)
1258 * MethodTypeDesc::ofDescriptor} with the result descriptor string.
1259 * <p>
1260 * If this method type cannot be {@linkplain ##descriptor described nominally}
1261 * and the result is a string of the form:
1262 * <blockquote>{@code "(<parameter-descriptors>)<return-descriptor>"}</blockquote>
1263 * where {@code <parameter-descriptors>} is the concatenation of the
1264 * {@linkplain Class#descriptorString() descriptor string} of all
1265 * of the parameter types and the {@linkplain Class#descriptorString() descriptor string}
1266 * of the return type. No {@link java.lang.constant.MethodTypeDesc MethodTypeDesc}
1267 * can be produced from the result string.
1268 *
1269 * @since 12
1270 * @jvms 4.3.3 Method Descriptors
1271 * @see <a href="#descriptor">Nominal Descriptor for {@code MethodType}</a>
1272 */
1273 @Override
1274 public String descriptorString() {
1275 return toMethodDescriptorString();
1276 }
1277
1278 /*non-public*/
1279 static String toFieldDescriptorString(Class<?> cls) {
1280 return BytecodeDescriptor.unparse(cls);
1281 }
1282
1283 /**
1284 * Returns a nominal descriptor for this instance, if one can be
1285 * constructed, or an empty {@link Optional} if one cannot be.
1286 *
1287 * @return An {@link Optional} containing the resulting nominal descriptor,
1288 * or an empty {@link Optional} if one cannot be constructed.
1289 * @since 12
1290 * @see <a href="#descriptor">Nominal Descriptor for {@code MethodType}</a>
1291 */
1292 @Override
1293 public Optional<MethodTypeDesc> describeConstable() {
1294 try {
1295 return Optional.of(MethodTypeDesc.of(returnType().describeConstable().orElseThrow(),
1296 Stream.of(parameterArray())
1297 .map(p -> p.describeConstable().orElseThrow())
1298 .toArray(ClassDesc[]::new)));
1299 }
1300 catch (NoSuchElementException e) {
1301 return Optional.empty();
1302 }
1303 }
1304
1305 /// Serialization.
1306
1307 /**
1308 * There are no serializable fields for {@code MethodType}.
1309 */
1310 @java.io.Serial
1311 private static final java.io.ObjectStreamField[] serialPersistentFields = { };
1312
1313 /**
1314 * Save the {@code MethodType} instance to a stream.
1315 *
1316 * @serialData
1317 * For portability, the serialized format does not refer to named fields.
1318 * Instead, the return type and parameter type arrays are written directly
1319 * from the {@code writeObject} method, using two calls to {@code s.writeObject}
1320 * as follows:
1321 * <blockquote><pre>{@code
1322 s.writeObject(this.returnType());
1323 s.writeObject(this.parameterArray());
1324 * }</pre></blockquote>
1325 * <p>
1326 * The deserialized field values are checked as if they were
1327 * provided to the factory method {@link #methodType(Class,Class[]) methodType}.
1328 * For example, null values, or {@code void} parameter types,
1329 * will lead to exceptions during deserialization.
1330 * @param s the stream to write the object to
1331 * @throws java.io.IOException if there is a problem writing the object
1332 */
1333 @java.io.Serial
1334 private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
1335 s.defaultWriteObject(); // requires serialPersistentFields to be an empty array
1336 s.writeObject(returnType());
1337 s.writeObject(parameterArray());
1338 }
1339
1340 /**
1341 * Reconstitute the {@code MethodType} instance from a stream (that is,
1342 * deserialize it).
1343 * This instance is a scratch object with bogus final fields.
1344 * It provides the parameters to the factory method called by
1345 * {@link #readResolve readResolve}.
1346 * After that call it is discarded.
1347 * @param s the stream to read the object from
1348 * @throws java.io.IOException if there is a problem reading the object
1349 * @throws ClassNotFoundException if one of the component classes cannot be resolved
1350 * @see #readResolve
1351 * @see #writeObject
1352 */
1353 @java.io.Serial
1354 private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
1355 // Assign defaults in case this object escapes
1356 UNSAFE.putReference(this, OffsetHolder.rtypeOffset, void.class);
1357 UNSAFE.putReference(this, OffsetHolder.ptypesOffset, NO_PTYPES);
1358
1359 s.defaultReadObject(); // requires serialPersistentFields to be an empty array
1360
1361 Class<?> returnType = (Class<?>) s.readObject();
1362 Class<?>[] parameterArray = (Class<?>[]) s.readObject();
1363
1364 // Verify all operands, and make sure ptypes is unshared
1365 // Cache the new MethodType for readResolve
1366 wrapAlt = new MethodType[]{MethodType.methodType(returnType, parameterArray)};
1367 }
1368
1369 // Support for resetting final fields while deserializing. Implement Holder
1370 // pattern to make the rarely needed offset calculation lazy.
1371 private static class OffsetHolder {
1372 static final long rtypeOffset
1373 = UNSAFE.objectFieldOffset(MethodType.class, "rtype");
1374
1375 static final long ptypesOffset
1376 = UNSAFE.objectFieldOffset(MethodType.class, "ptypes");
1377 }
1378
1379 /**
1380 * Resolves and initializes a {@code MethodType} object
1381 * after serialization.
1382 * @return the fully initialized {@code MethodType} object
1383 */
1384 @java.io.Serial
1385 private Object readResolve() {
1386 // Do not use a trusted path for deserialization:
1387 // return makeImpl(rtype, ptypes, true);
1388 // Verify all operands, and make sure ptypes is unshared:
1389 // Return a new validated MethodType for the rtype and ptypes passed from readObject.
1390 MethodType mt = ((MethodType[])wrapAlt)[0];
1391 wrapAlt = null;
1392 return mt;
1393 }
1394 }