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