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.util.Arrays;
32 import java.util.Collections;
33 import java.util.function.Supplier;
34 import java.util.List;
35 import java.util.Map;
36 import java.util.NoSuchElementException;
37 import java.util.Objects;
38 import java.util.Optional;
39 import java.util.StringJoiner;
40 import java.util.concurrent.ConcurrentHashMap;
41 import java.util.stream.Stream;
42
43 import jdk.internal.util.ReferencedKeySet;
44 import jdk.internal.util.ReferenceKey;
45 import jdk.internal.vm.annotation.Stable;
46 import sun.invoke.util.BytecodeDescriptor;
47 import sun.invoke.util.VerifyType;
48 import sun.invoke.util.Wrapper;
49 import sun.security.util.SecurityConstants;
50
51 import static java.lang.invoke.MethodHandleStatics.UNSAFE;
52 import static java.lang.invoke.MethodHandleStatics.newIllegalArgumentException;
53
54 /**
55 * A method type represents the arguments and return type accepted and
56 * returned by a method handle, or the arguments and return type passed
57 * and expected by a method handle caller. Method types must be properly
58 * matched between a method handle and all its callers,
59 * and the JVM's operations enforce this matching at, specifically
60 * during calls to {@link MethodHandle#invokeExact MethodHandle.invokeExact}
61 * and {@link MethodHandle#invoke MethodHandle.invoke}, and during execution
62 * of {@code invokedynamic} instructions.
63 * <p>
64 * The structure is a return type accompanied by any number of parameter types.
65 * The types (primitive, {@code void}, and reference) are represented by {@link Class} objects.
66 * (For ease of exposition, we treat {@code void} as if it were a type.
67 * In fact, it denotes the absence of a return type.)
68 * <p>
69 * All instances of {@code MethodType} are immutable.
70 * Two instances are completely interchangeable if they compare equal.
71 * Equality depends on pairwise correspondence of the return and parameter types and on nothing else.
72 * <p>
73 * This type can be created only by factory methods.
74 * All factory methods may cache values, though caching is not guaranteed.
75 * Some factory methods are static, while others are virtual methods which
76 * modify precursor method types, e.g., by changing a selected parameter.
77 * <p>
78 * Factory methods which operate on groups of parameter types
79 * are systematically presented in two versions, so that both Java arrays and
80 * Java lists can be used to work with groups of parameter types.
81 * The query methods {@code parameterArray} and {@code parameterList}
82 * also provide a choice between arrays and lists.
83 * <p>
84 * {@code MethodType} objects are sometimes derived from bytecode instructions
85 * such as {@code invokedynamic}, specifically from the type descriptor strings associated
86 * with the instructions in a class file's constant pool.
87 * <p>
88 * Like classes and strings, method types can also be represented directly
89 * in a class file's constant pool as constants.
90 * A method type may be loaded by an {@code ldc} instruction which refers
91 * to a suitable {@code CONSTANT_MethodType} constant pool entry.
92 * The entry refers to a {@code CONSTANT_Utf8} spelling for the descriptor string.
93 * (For full details on method type constants, see sections {@jvms
94 * 4.4.8} and {@jvms 5.4.3.5} of the Java Virtual Machine
95 * Specification.)
96 * <p>
97 * When the JVM materializes a {@code MethodType} from a descriptor string,
98 * all classes named in the descriptor must be accessible, and will be loaded.
99 * (But the classes need not be initialized, as is the case with a {@code CONSTANT_Class}.)
100 * This loading may occur at any time before the {@code MethodType} object is first derived.
101 * <p>
102 * <b><a id="descriptor">Nominal Descriptors</a></b>
103 * <p>
104 * A {@code MethodType} can be described in {@linkplain MethodTypeDesc nominal form}
105 * if and only if all of the parameter types and return type can be described
106 * with a {@link Class#describeConstable() nominal descriptor} represented by
107 * {@link ClassDesc}. If a method type can be described nominally, then:
108 * <ul>
109 * <li>The method type has a {@link MethodTypeDesc nominal descriptor}
110 * returned by {@link #describeConstable() MethodType::describeConstable}.</li>
111 * <li>The descriptor string returned by
112 * {@link #descriptorString() MethodType::descriptorString} or
113 * {@link #toMethodDescriptorString() MethodType::toMethodDescriptorString}
114 * for the method type is a method descriptor (JVMS {@jvms 4.3.3}).</li>
115 * </ul>
116 * <p>
117 * If any of the parameter types or return type cannot be described
118 * nominally, i.e. {@link Class#describeConstable() Class::describeConstable}
119 * returns an empty optional for that type,
120 * then the method type cannot be described nominally:
121 * <ul>
122 * <li>The method type has no {@link MethodTypeDesc nominal descriptor} and
123 * {@link #describeConstable() MethodType::describeConstable} returns
124 * an empty optional.</li>
125 * <li>The descriptor string returned by
126 * {@link #descriptorString() MethodType::descriptorString} or
127 * {@link #toMethodDescriptorString() MethodType::toMethodDescriptorString}
128 * for the method type is not a type descriptor.</li>
129 * </ul>
130 *
131 * @author John Rose, JSR 292 EG
132 * @since 1.7
133 */
134 public final
135 class MethodType
136 implements Constable,
137 TypeDescriptor.OfMethod<Class<?>, MethodType>,
138 java.io.Serializable {
139 @java.io.Serial
140 private static final long serialVersionUID = 292L; // {rtype, {ptype...}}
141
142 // The rtype and ptypes fields define the structural identity of the method type:
143 private final @Stable Class<?> rtype;
144 private final @Stable Class<?>[] ptypes;
145
146 // The remaining fields are caches of various sorts:
147 private @Stable MethodTypeForm form; // erased form, plus cached data about primitives
148 private @Stable Object wrapAlt; // alternative wrapped/unwrapped version and
149 // private communication for readObject and readResolve
150 private @Stable Invokers invokers; // cache of handy higher-order adapters
151 private @Stable String methodDescriptor; // cache for toMethodDescriptorString
152
153 /**
154 * Constructor that performs no copying or validation.
155 * Should only be called from the factory method makeImpl
156 */
157 private MethodType(Class<?> rtype, Class<?>[] ptypes) {
158 this.rtype = rtype;
159 this.ptypes = ptypes;
160 }
161
162 /*trusted*/ MethodTypeForm form() { return form; }
163 /*trusted*/ Class<?> rtype() { return rtype; }
164 /*trusted*/ Class<?>[] ptypes() { return ptypes; }
165
166 void setForm(MethodTypeForm f) { form = f; }
167
168 /** This number, mandated by the JVM spec as 255,
169 * is the maximum number of <em>slots</em>
170 * that any Java method can receive in its argument list.
171 * It limits both JVM signatures and method type objects.
172 * The longest possible invocation will look like
173 * {@code staticMethod(arg1, arg2, ..., arg255)} or
174 * {@code x.virtualMethod(arg1, arg2, ..., arg254)}.
175 */
176 /*non-public*/
177 static final int MAX_JVM_ARITY = 255; // this is mandated by the JVM spec.
178
179 /** This number is the maximum arity of a method handle, 254.
180 * It is derived from the absolute JVM-imposed arity by subtracting one,
181 * which is the slot occupied by the method handle itself at the
182 * beginning of the argument list used to invoke the method handle.
183 * The longest possible invocation will look like
184 * {@code mh.invoke(arg1, arg2, ..., arg254)}.
185 */
186 // Issue: Should we allow MH.invokeWithArguments to go to the full 255?
187 /*non-public*/
188 static final int MAX_MH_ARITY = MAX_JVM_ARITY-1; // deduct one for mh receiver
189
190 /** This number is the maximum arity of a method handle invoker, 253.
191 * It is derived from the absolute JVM-imposed arity by subtracting two,
192 * which are the slots occupied by invoke method handle, and the
193 * target method handle, which are both at the beginning of the argument
194 * list used to invoke the target method handle.
195 * The longest possible invocation will look like
196 * {@code invokermh.invoke(targetmh, arg1, arg2, ..., arg253)}.
197 */
198 /*non-public*/
199 static final int MAX_MH_INVOKER_ARITY = MAX_MH_ARITY-1; // deduct one more for invoker
200
201 /** Return number of extra slots (count of long/double args). */
202 private static int checkPtypes(Class<?>[] ptypes) {
203 int slots = 0;
204 for (Class<?> ptype : ptypes) {
205 Objects.requireNonNull(ptype);
206 if (ptype == void.class)
207 throw newIllegalArgumentException("parameter type cannot be void");
208 if (ptype == double.class || ptype == long.class) {
209 slots++;
210 }
211 }
212 checkSlotCount(ptypes.length + slots);
213 return slots;
214 }
215
216 static {
217 // MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work:
218 assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0);
219 }
220 static void checkSlotCount(int count) {
221 if ((count & MAX_JVM_ARITY) != count)
222 throw newIllegalArgumentException("bad parameter count "+count);
223 }
224 private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) {
225 if (num instanceof Integer) num = "bad index: "+num;
226 return new IndexOutOfBoundsException(num.toString());
227 }
228
229 static final ReferencedKeySet<MethodType> internTable =
230 ReferencedKeySet.create(false, true, new Supplier<>() {
231 @Override
232 public Map<ReferenceKey<MethodType>, ReferenceKey<MethodType>> get() {
233 return new ConcurrentHashMap<>(512);
234 }
235 });
236
237 static final Class<?>[] NO_PTYPES = {};
238
239 /**
240 * Finds or creates an instance of the given method type.
241 * @param rtype the return type
242 * @param ptypes the parameter types
243 * @return a method type with the given components
244 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
245 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
246 */
247 public static MethodType methodType(Class<?> rtype, Class<?>[] ptypes) {
248 return methodType(rtype, ptypes, false);
249 }
250
251 /**
252 * Finds or creates a method type with the given components.
253 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
254 * @param rtype the return type
255 * @param ptypes the parameter types
256 * @return a method type with the given components
257 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
258 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
259 */
260 public static MethodType methodType(Class<?> rtype, List<Class<?>> ptypes) {
261 boolean notrust = false; // random List impl. could return evil ptypes array
262 return methodType(rtype, listToArray(ptypes), notrust);
263 }
264
265 private static Class<?>[] listToArray(List<Class<?>> ptypes) {
266 // sanity check the size before the toArray call, since size might be huge
267 checkSlotCount(ptypes.size());
268 return ptypes.toArray(NO_PTYPES);
269 }
270
271 /**
272 * Finds or creates a method type with the given components.
273 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
274 * The leading parameter type is prepended to the remaining array.
275 * @param rtype the return type
276 * @param ptype0 the first parameter type
277 * @param ptypes the remaining parameter types
278 * @return a method type with the given components
279 * @throws NullPointerException if {@code rtype} or {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is null
280 * @throws IllegalArgumentException if {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is {@code void.class}
281 */
282 public static MethodType methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes) {
283 int len = ptypes.length;
284 if (rtype == Object.class && ptype0 == Object.class) {
285 if (len == 0) {
286 return genericMethodType(1, false);
287 }
288 if (isAllObject(ptypes, len - 1)) {
289 Class<?> lastParam = ptypes[len - 1];
290 if (lastParam == Object.class) {
291 return genericMethodType(len + 1, false);
292 } else if (lastParam == Object[].class) {
293 return genericMethodType(len, true);
294 }
295 }
296 }
297 Class<?>[] ptypes1 = new Class<?>[1 + len];
298 ptypes1[0] = ptype0;
299 System.arraycopy(ptypes, 0, ptypes1, 1, len);
300 return makeImpl(rtype, ptypes1, true);
301 }
302
303 /**
304 * Finds or creates a method type with the given components.
305 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
306 * The resulting method has no parameter types.
307 * @param rtype the return type
308 * @return a method type with the given return value
309 * @throws NullPointerException if {@code rtype} is null
310 */
311 public static MethodType methodType(Class<?> rtype) {
312 if (rtype == Object.class) {
313 return genericMethodType(0, false);
314 }
315 return makeImpl(rtype, NO_PTYPES, true);
316 }
317
318 /**
319 * Finds or creates a method type with the given components.
320 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
321 * The resulting method has the single given parameter type.
322 * @param rtype the return type
323 * @param ptype0 the parameter type
324 * @return a method type with the given return value and parameter type
325 * @throws NullPointerException if {@code rtype} or {@code ptype0} is null
326 * @throws IllegalArgumentException if {@code ptype0} is {@code void.class}
327 */
328 public static MethodType methodType(Class<?> rtype, Class<?> ptype0) {
329 if (rtype == Object.class) {
330 if (ptype0 == Object.class) {
331 return genericMethodType(1, false);
332 } else if (ptype0 == Object[].class) {
333 return genericMethodType(0, true);
334 }
335 }
336 return makeImpl(rtype, new Class<?>[]{ ptype0 }, true);
337 }
338
339 /**
340 * Finds or creates a method type with the given components.
341 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
342 * The resulting method has the same parameter types as {@code ptypes},
343 * and the specified return type.
344 * @param rtype the return type
345 * @param ptypes the method type which supplies the parameter types
346 * @return a method type with the given components
347 * @throws NullPointerException if {@code rtype} or {@code ptypes} is null
348 */
349 public static MethodType methodType(Class<?> rtype, MethodType ptypes) {
350 return methodType(rtype, ptypes.ptypes, true);
351 }
352
353 private static boolean isAllObject(Class<?>[] ptypes, int to) {
354 for (int i = 0; i < to; i++) {
355 if (ptypes[i] != Object.class) {
356 return false;
357 }
358 }
359 return true;
360 }
361
362 /*trusted*/
363 static MethodType methodType(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {
364 if (rtype == Object.class) {
365 int last = ptypes.length - 1;
366 if (last < 0) {
367 return genericMethodType(0, false);
368 }
369 if (isAllObject(ptypes, last)) {
370 Class<?> lastParam = ptypes[last];
371 if (lastParam == Object.class) {
372 return genericMethodType(last + 1, false);
373 } else if (lastParam == Object[].class) {
374 return genericMethodType(last, true);
375 }
376 }
377 }
378 return makeImpl(rtype, ptypes, trusted);
379 }
380
381 /**
382 * Sole factory method to find or create an interned method type. Will perform
383 * input validation on behalf of factory methods
384 *
385 * @param rtype desired return type
386 * @param ptypes desired parameter types
387 * @param trusted whether the ptypes can be used without cloning
388 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
389 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
390 * @return the unique method type of the desired structure
391 */
392 private static MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {
393 if (ptypes.length == 0) {
394 ptypes = NO_PTYPES; trusted = true;
395 }
396 MethodType primordialMT = new MethodType(rtype, ptypes);
397 MethodType mt = internTable.get(primordialMT);
398 if (mt != null)
399 return mt;
400
401 // promote the object to the Real Thing, and reprobe
402 Objects.requireNonNull(rtype);
403 if (trusted) {
404 MethodType.checkPtypes(ptypes);
405 mt = primordialMT;
406 } else {
407 // Make defensive copy then validate
408 ptypes = Arrays.copyOf(ptypes, ptypes.length);
409 MethodType.checkPtypes(ptypes);
410 mt = new MethodType(rtype, ptypes);
411 }
412 mt.form = MethodTypeForm.findForm(mt);
413 return internTable.intern(mt);
414 }
415 private static final @Stable MethodType[] objectOnlyTypes = new MethodType[20];
416
417 /**
418 * Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array.
419 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
420 * All parameters and the return type will be {@code Object},
421 * except the final array parameter if any, which will be {@code Object[]}.
422 * @param objectArgCount number of parameters (excluding the final array parameter if any)
423 * @param finalArray whether there will be a trailing array parameter, of type {@code Object[]}
424 * @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments
425 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true)
426 * @see #genericMethodType(int)
427 */
428 public static MethodType genericMethodType(int objectArgCount, boolean finalArray) {
429 MethodType mt;
430 checkSlotCount(objectArgCount);
431 int ivarargs = (!finalArray ? 0 : 1);
432 int ootIndex = objectArgCount*2 + ivarargs;
433 if (ootIndex < objectOnlyTypes.length) {
434 mt = objectOnlyTypes[ootIndex];
435 if (mt != null) return mt;
436 }
437 Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs];
438 Arrays.fill(ptypes, Object.class);
439 if (ivarargs != 0) ptypes[objectArgCount] = Object[].class;
440 mt = makeImpl(Object.class, ptypes, true);
441 if (ootIndex < objectOnlyTypes.length) {
442 objectOnlyTypes[ootIndex] = mt; // cache it here also!
443 }
444 return mt;
445 }
446
447 /**
448 * Finds or creates a method type whose components are all {@code Object}.
449 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
450 * All parameters and the return type will be Object.
451 * @param objectArgCount number of parameters
452 * @return a generally applicable method type, for all calls of the given argument count
453 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255
454 * @see #genericMethodType(int, boolean)
455 */
456 public static MethodType genericMethodType(int objectArgCount) {
457 return genericMethodType(objectArgCount, false);
458 }
459
460 /**
461 * Finds or creates a method type with a single different parameter type.
462 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
463 * @param num the index (zero-based) of the parameter type to change
464 * @param nptype a new parameter type to replace the old one with
465 * @return the same type, except with the selected parameter changed
466 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
467 * @throws IllegalArgumentException if {@code nptype} is {@code void.class}
468 * @throws NullPointerException if {@code nptype} is null
469 */
470 public MethodType changeParameterType(int num, Class<?> nptype) {
471 if (parameterType(num) == nptype) return this;
472 Class<?>[] nptypes = ptypes.clone();
473 nptypes[num] = nptype;
474 return makeImpl(rtype, nptypes, true);
475 }
476
477 /**
478 * Finds or creates a method type with additional parameter types.
479 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
480 * @param num the position (zero-based) of the inserted parameter type(s)
481 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
482 * @return the same type, except with the selected parameter(s) inserted
483 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
484 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
485 * or if the resulting method type would have more than 255 parameter slots
486 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
487 */
488 public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) {
489 int len = ptypes.length;
490 if (num < 0 || num > len)
491 throw newIndexOutOfBoundsException(num);
492 int ins = checkPtypes(ptypesToInsert);
493 checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins);
494 int ilen = ptypesToInsert.length;
495 if (ilen == 0) return this;
496 Class<?>[] nptypes = new Class<?>[len + ilen];
497 if (num > 0) {
498 System.arraycopy(ptypes, 0, nptypes, 0, num);
499 }
500 System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen);
501 if (num < len) {
502 System.arraycopy(ptypes, num, nptypes, num+ilen, len-num);
503 }
504 return makeImpl(rtype, nptypes, true);
505 }
506
507 /**
508 * Finds or creates a method type with additional parameter types.
509 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
510 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
511 * @return the same type, except with the selected parameter(s) appended
512 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
513 * or if the resulting method type would have more than 255 parameter slots
514 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
515 */
516 public MethodType appendParameterTypes(Class<?>... ptypesToInsert) {
517 return insertParameterTypes(parameterCount(), ptypesToInsert);
518 }
519
520 /**
521 * Finds or creates a method type with additional parameter types.
522 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
523 * @param num the position (zero-based) of the inserted parameter type(s)
524 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
525 * @return the same type, except with the selected parameter(s) inserted
526 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
527 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
528 * or if the resulting method type would have more than 255 parameter slots
529 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
530 */
531 public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) {
532 return insertParameterTypes(num, listToArray(ptypesToInsert));
533 }
534
535 /**
536 * Finds or creates a method type with additional parameter types.
537 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
538 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
539 * @return the same type, except with the selected parameter(s) appended
540 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
541 * or if the resulting method type would have more than 255 parameter slots
542 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
543 */
544 public MethodType appendParameterTypes(List<Class<?>> ptypesToInsert) {
545 return insertParameterTypes(parameterCount(), ptypesToInsert);
546 }
547
548 /**
549 * Finds or creates a method type with modified parameter types.
550 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
551 * @param start the position (zero-based) of the first replaced parameter type(s)
552 * @param end the position (zero-based) after the last replaced parameter type(s)
553 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
554 * @return the same type, except with the selected parameter(s) replaced
555 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
556 * or if {@code end} is negative or greater than {@code parameterCount()}
557 * or if {@code start} is greater than {@code end}
558 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
559 * or if the resulting method type would have more than 255 parameter slots
560 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
561 */
562 /*non-public*/
563 MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) {
564 if (start == end)
565 return insertParameterTypes(start, ptypesToInsert);
566 int len = ptypes.length;
567 if (!(0 <= start && start <= end && end <= len))
568 throw newIndexOutOfBoundsException("start="+start+" end="+end);
569 int ilen = ptypesToInsert.length;
570 if (ilen == 0)
571 return dropParameterTypes(start, end);
572 return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert);
573 }
574
575 /** Replace the last arrayLength parameter types with the component type of arrayType.
576 * @param arrayType any array type
577 * @param pos position at which to spread
578 * @param arrayLength the number of parameter types to change
579 * @return the resulting type
580 */
581 /*non-public*/
582 MethodType asSpreaderType(Class<?> arrayType, int pos, int arrayLength) {
583 assert(parameterCount() >= arrayLength);
584 int spreadPos = pos;
585 if (arrayLength == 0) return this; // nothing to change
586 if (arrayType == Object[].class) {
587 if (isGeneric()) return this; // nothing to change
588 if (spreadPos == 0) {
589 // no leading arguments to preserve; go generic
590 MethodType res = genericMethodType(arrayLength);
591 if (rtype != Object.class) {
592 res = res.changeReturnType(rtype);
593 }
594 return res;
595 }
596 }
597 Class<?> elemType = arrayType.getComponentType();
598 assert(elemType != null);
599 for (int i = spreadPos; i < spreadPos + arrayLength; i++) {
600 if (ptypes[i] != elemType) {
601 Class<?>[] fixedPtypes = ptypes.clone();
602 Arrays.fill(fixedPtypes, i, spreadPos + arrayLength, elemType);
603 return methodType(rtype, fixedPtypes);
604 }
605 }
606 return this; // arguments check out; no change
607 }
608
609 /** Return the leading parameter type, which must exist and be a reference.
610 * @return the leading parameter type, after error checks
611 */
612 /*non-public*/
613 Class<?> leadingReferenceParameter() {
614 Class<?> ptype;
615 if (ptypes.length == 0 ||
616 (ptype = ptypes[0]).isPrimitive())
617 throw newIllegalArgumentException("no leading reference parameter");
618 return ptype;
619 }
620
621 /** Delete the last parameter type and replace it with arrayLength copies of the component type of arrayType.
622 * @param arrayType any array type
623 * @param pos position at which to insert parameters
624 * @param arrayLength the number of parameter types to insert
625 * @return the resulting type
626 */
627 /*non-public*/
628 MethodType asCollectorType(Class<?> arrayType, int pos, int arrayLength) {
629 assert(parameterCount() >= 1);
630 assert(pos < ptypes.length);
631 assert(ptypes[pos].isAssignableFrom(arrayType));
632 MethodType res;
633 if (arrayType == Object[].class) {
634 res = genericMethodType(arrayLength);
635 if (rtype != Object.class) {
636 res = res.changeReturnType(rtype);
637 }
638 } else {
639 Class<?> elemType = arrayType.getComponentType();
640 assert(elemType != null);
641 res = methodType(rtype, Collections.nCopies(arrayLength, elemType));
642 }
643 if (ptypes.length == 1) {
644 return res;
645 } else {
646 // insert after (if need be), then before
647 if (pos < ptypes.length - 1) {
648 res = res.insertParameterTypes(arrayLength, Arrays.copyOfRange(ptypes, pos + 1, ptypes.length));
649 }
650 return res.insertParameterTypes(0, Arrays.copyOf(ptypes, pos));
651 }
652 }
653
654 /**
655 * Finds or creates a method type with some parameter types omitted.
656 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
657 * @param start the index (zero-based) of the first parameter type to remove
658 * @param end the index (greater than {@code start}) of the first parameter type after not to remove
659 * @return the same type, except with the selected parameter(s) removed
660 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
661 * or if {@code end} is negative or greater than {@code parameterCount()}
662 * or if {@code start} is greater than {@code end}
663 */
664 public MethodType dropParameterTypes(int start, int end) {
665 int len = ptypes.length;
666 if (!(0 <= start && start <= end && end <= len))
667 throw newIndexOutOfBoundsException("start="+start+" end="+end);
668 if (start == end) return this;
669 Class<?>[] nptypes;
670 if (start == 0) {
671 if (end == len) {
672 // drop all parameters
673 nptypes = NO_PTYPES;
674 } else {
675 // drop initial parameter(s)
676 nptypes = Arrays.copyOfRange(ptypes, end, len);
677 }
678 } else {
679 if (end == len) {
680 // drop trailing parameter(s)
681 nptypes = Arrays.copyOfRange(ptypes, 0, start);
682 } else {
683 int tail = len - end;
684 nptypes = Arrays.copyOfRange(ptypes, 0, start + tail);
685 System.arraycopy(ptypes, end, nptypes, start, tail);
686 }
687 }
688 return methodType(rtype, nptypes, true);
689 }
690
691 /**
692 * Finds or creates a method type with a different return type.
693 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
694 * @param nrtype a return parameter type to replace the old one with
695 * @return the same type, except with the return type change
696 * @throws NullPointerException if {@code nrtype} is null
697 */
698 public MethodType changeReturnType(Class<?> nrtype) {
699 if (returnType() == nrtype) return this;
700 return methodType(nrtype, ptypes, true);
701 }
702
703 /**
704 * Reports if this type contains a primitive argument or return value.
705 * The return type {@code void} counts as a primitive.
706 * @return true if any of the types are primitives
707 */
708 public boolean hasPrimitives() {
709 return form.hasPrimitives();
710 }
711
712 /**
713 * Reports if this type contains a wrapper argument or return value.
714 * Wrappers are types which box primitive values, such as {@link Integer}.
715 * The reference type {@code java.lang.Void} counts as a wrapper,
716 * if it occurs as a return type.
717 * @return true if any of the types are wrappers
718 */
719 public boolean hasWrappers() {
720 return unwrap() != this;
721 }
722
723 /**
724 * Erases all reference types to {@code Object}.
725 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
726 * All primitive types (including {@code void}) will remain unchanged.
727 * @return a version of the original type with all reference types replaced
728 */
729 public MethodType erase() {
730 return form.erasedType();
731 }
732
733 /**
734 * Erases all reference types to {@code Object}, and all subword types to {@code int}.
735 * This is the reduced type polymorphism used by private methods
736 * such as {@link MethodHandle#invokeBasic invokeBasic}.
737 * @return a version of the original type with all reference and subword types replaced
738 */
739 /*non-public*/
740 MethodType basicType() {
741 return form.basicType();
742 }
743
744 private static final @Stable Class<?>[] METHOD_HANDLE_ARRAY
745 = new Class<?>[] { MethodHandle.class };
746
747 /**
748 * @return a version of the original type with MethodHandle prepended as the first argument
749 */
750 /*non-public*/
751 MethodType invokerType() {
752 return insertParameterTypes(0, METHOD_HANDLE_ARRAY);
753 }
754
755 /**
756 * Converts all types, both reference and primitive, to {@code Object}.
757 * Convenience method for {@link #genericMethodType(int) genericMethodType}.
758 * The expression {@code type.wrap().erase()} produces the same value
759 * as {@code type.generic()}.
760 * @return a version of the original type with all types replaced
761 */
762 public MethodType generic() {
763 return genericMethodType(parameterCount());
764 }
765
766 /*non-public*/
767 boolean isGeneric() {
768 return this == erase() && !hasPrimitives();
769 }
770
771 /**
772 * Converts all primitive types to their corresponding wrapper types.
773 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
774 * All reference types (including wrapper types) will remain unchanged.
775 * A {@code void} return type is changed to the type {@code java.lang.Void}.
776 * The expression {@code type.wrap().erase()} produces the same value
777 * as {@code type.generic()}.
778 * @return a version of the original type with all primitive types replaced
779 */
780 public MethodType wrap() {
781 return hasPrimitives() ? wrapWithPrims(this) : this;
782 }
783
784 /**
785 * Converts all wrapper types to their corresponding primitive types.
786 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
787 * All primitive types (including {@code void}) will remain unchanged.
788 * A return type of {@code java.lang.Void} is changed to {@code void}.
789 * @return a version of the original type with all wrapper types replaced
790 */
791 public MethodType unwrap() {
792 MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this);
793 return unwrapWithNoPrims(noprims);
794 }
795
796 private static MethodType wrapWithPrims(MethodType pt) {
797 assert(pt.hasPrimitives());
798 MethodType wt = (MethodType)pt.wrapAlt;
799 if (wt == null) {
800 // fill in lazily
801 wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP);
802 assert(wt != null);
803 pt.wrapAlt = wt;
804 }
805 return wt;
806 }
807
808 private static MethodType unwrapWithNoPrims(MethodType wt) {
809 assert(!wt.hasPrimitives());
810 MethodType uwt = (MethodType)wt.wrapAlt;
811 if (uwt == null) {
812 // fill in lazily
813 uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP);
814 if (uwt == null)
815 uwt = wt; // type has no wrappers or prims at all
816 wt.wrapAlt = uwt;
817 }
818 return uwt;
819 }
820
821 /**
822 * Returns the parameter type at the specified index, within this method type.
823 * @param num the index (zero-based) of the desired parameter type
824 * @return the selected parameter type
825 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
826 */
827 public Class<?> parameterType(int num) {
828 return ptypes[num];
829 }
830 /**
831 * Returns the number of parameter types in this method type.
832 * @return the number of parameter types
833 */
834 public int parameterCount() {
835 return ptypes.length;
836 }
837 /**
838 * Returns the return type of this method type.
839 * @return the return type
840 */
841 public Class<?> returnType() {
842 return rtype;
843 }
844
845 /**
846 * Presents the parameter types as a list (a convenience method).
847 * The list will be immutable.
848 * @return the parameter types (as an immutable list)
849 */
850 public List<Class<?>> parameterList() {
851 return List.of(ptypes);
852 }
853
854 /**
855 * Returns the last parameter type of this method type.
856 * If this type has no parameters, the sentinel value
857 * {@code void.class} is returned instead.
858 * @apiNote
859 * <p>
860 * The sentinel value is chosen so that reflective queries can be
861 * made directly against the result value.
862 * The sentinel value cannot be confused with a real parameter,
863 * since {@code void} is never acceptable as a parameter type.
864 * For variable arity invocation modes, the expression
865 * {@link Class#getComponentType lastParameterType().getComponentType()}
866 * is useful to query the type of the "varargs" parameter.
867 * @return the last parameter type if any, else {@code void.class}
868 * @since 10
869 */
870 public Class<?> lastParameterType() {
871 int len = ptypes.length;
872 return len == 0 ? void.class : ptypes[len-1];
873 }
874
875 /**
876 * Presents the parameter types as an array (a convenience method).
877 * Changes to the array will not result in changes to the type.
878 * @return the parameter types (as a fresh copy if necessary)
879 */
880 public Class<?>[] parameterArray() {
881 return ptypes.clone();
882 }
883
884 /**
885 * Compares the specified object with this type for equality.
886 * That is, it returns {@code true} if and only if the specified object
887 * is also a method type with exactly the same parameters and return type.
888 * @param x object to compare
889 * @see Object#equals(Object)
890 */
891 @Override
892 public boolean equals(Object x) {
893 if (this == x) {
894 return true;
895 }
896 if (x instanceof MethodType mt) {
897 return equals(mt);
898 }
899 return false;
900 }
901
902 private boolean equals(MethodType that) {
903 return this.rtype == that.rtype
904 && Arrays.equals(this.ptypes, that.ptypes);
905 }
906
907 /**
908 * Returns the hash code value for this method type.
909 * It is defined to be the same as the hashcode of a List
910 * whose elements are the return type followed by the
911 * parameter types.
912 * @return the hash code value for this method type
913 * @see Object#hashCode()
914 * @see #equals(Object)
915 * @see List#hashCode()
916 */
917 @Override
918 public int hashCode() {
919 int hashCode = 31 + rtype.hashCode();
920 for (Class<?> ptype : ptypes)
921 hashCode = 31 * hashCode + ptype.hashCode();
922 return hashCode;
923 }
924
925 /**
926 * Returns a string representation of the method type,
927 * of the form {@code "(PT0,PT1...)RT"}.
928 * The string representation of a method type is a
929 * parenthesis enclosed, comma separated list of type names,
930 * followed immediately by the return type.
931 * <p>
932 * Each type is represented by its
933 * {@link java.lang.Class#getSimpleName simple name}.
934 */
935 @Override
936 public String toString() {
937 StringJoiner sj = new StringJoiner(",", "(",
938 ")" + rtype.getSimpleName());
939 for (int i = 0; i < ptypes.length; i++) {
940 sj.add(ptypes[i].getSimpleName());
941 }
942 return sj.toString();
943 }
944
945 /** True if my parameter list is effectively identical to the given full list,
946 * after skipping the given number of my own initial parameters.
947 * In other words, after disregarding {@code skipPos} parameters,
948 * my remaining parameter list is no longer than the {@code fullList}, and
949 * is equal to the same-length initial sublist of {@code fullList}.
950 */
951 /*non-public*/
952 boolean effectivelyIdenticalParameters(int skipPos, List<Class<?>> fullList) {
953 int myLen = ptypes.length, fullLen = fullList.size();
954 if (skipPos > myLen || myLen - skipPos > fullLen)
955 return false;
956 List<Class<?>> myList = Arrays.asList(ptypes);
957 if (skipPos != 0) {
958 myList = myList.subList(skipPos, myLen);
959 myLen -= skipPos;
960 }
961 if (fullLen == myLen)
962 return myList.equals(fullList);
963 else
964 return myList.equals(fullList.subList(0, myLen));
965 }
966
967 /** True if the old return type can always be viewed (w/o casting) under new return type,
968 * and the new parameters can be viewed (w/o casting) under the old parameter types.
969 */
970 /*non-public*/
971 boolean isViewableAs(MethodType newType, boolean keepInterfaces) {
972 if (!VerifyType.isNullConversion(returnType(), newType.returnType(), keepInterfaces))
973 return false;
974 if (form == newType.form && form.erasedType == this)
975 return true; // my reference parameters are all Object
976 if (ptypes == newType.ptypes)
977 return true;
978 int argc = parameterCount();
979 if (argc != newType.parameterCount())
980 return false;
981 for (int i = 0; i < argc; i++) {
982 if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i), keepInterfaces))
983 return false;
984 }
985 return true;
986 }
987 /*non-public*/
988 boolean isConvertibleTo(MethodType newType) {
989 MethodTypeForm oldForm = this.form();
990 MethodTypeForm newForm = newType.form();
991 if (oldForm == newForm)
992 // same parameter count, same primitive/object mix
993 return true;
994 if (!canConvert(returnType(), newType.returnType()))
995 return false;
996 Class<?>[] srcTypes = newType.ptypes;
997 Class<?>[] dstTypes = ptypes;
998 if (srcTypes == dstTypes)
999 return true;
1000 int argc;
1001 if ((argc = srcTypes.length) != dstTypes.length)
1002 return false;
1003 if (argc <= 1) {
1004 if (argc == 1 && !canConvert(srcTypes[0], dstTypes[0]))
1005 return false;
1006 return true;
1007 }
1008 if ((!oldForm.hasPrimitives() && oldForm.erasedType == this) ||
1009 (!newForm.hasPrimitives() && newForm.erasedType == newType)) {
1010 // Somewhat complicated test to avoid a loop of 2 or more trips.
1011 // If either type has only Object parameters, we know we can convert.
1012 assert(canConvertParameters(srcTypes, dstTypes));
1013 return true;
1014 }
1015 return canConvertParameters(srcTypes, dstTypes);
1016 }
1017
1018 /** Returns true if MHs.explicitCastArguments produces the same result as MH.asType.
1019 * If the type conversion is impossible for either, the result should be false.
1020 */
1021 /*non-public*/
1022 boolean explicitCastEquivalentToAsType(MethodType newType) {
1023 if (this == newType) return true;
1024 if (!explicitCastEquivalentToAsType(rtype, newType.rtype)) {
1025 return false;
1026 }
1027 Class<?>[] srcTypes = newType.ptypes;
1028 Class<?>[] dstTypes = ptypes;
1029 if (dstTypes == srcTypes) {
1030 return true;
1031 }
1032 assert(dstTypes.length == srcTypes.length);
1033 for (int i = 0; i < dstTypes.length; i++) {
1034 if (!explicitCastEquivalentToAsType(srcTypes[i], dstTypes[i])) {
1035 return false;
1036 }
1037 }
1038 return true;
1039 }
1040
1041 /** Reports true if the src can be converted to the dst, by both asType and MHs.eCE,
1042 * and with the same effect.
1043 * MHs.eCA has the following "upgrades" to MH.asType:
1044 * 1. interfaces are unchecked (that is, treated as if aliased to Object)
1045 * Therefore, {@code Object->CharSequence} is possible in both cases but has different semantics
1046 * 2. the full matrix of primitive-to-primitive conversions is supported
1047 * Narrowing like {@code long->byte} and basic-typing like {@code boolean->int}
1048 * are not supported by asType, but anything supported by asType is equivalent
1049 * with MHs.eCE.
1050 * 3a. unboxing conversions can be followed by the full matrix of primitive conversions
1051 * 3b. unboxing of null is permitted (creates a zero primitive value)
1052 * Other than interfaces, reference-to-reference conversions are the same.
1053 * Boxing primitives to references is the same for both operators.
1054 */
1055 private static boolean explicitCastEquivalentToAsType(Class<?> src, Class<?> dst) {
1056 if (src == dst || dst == Object.class || dst == void.class) return true;
1057 if (src.isPrimitive()) {
1058 // Could be a prim/prim conversion, where casting is a strict superset.
1059 // Or a boxing conversion, which is always to an exact wrapper class.
1060 return canConvert(src, dst);
1061 } else if (dst.isPrimitive()) {
1062 // Unboxing behavior is different between MHs.eCA & MH.asType (see 3b).
1063 return false;
1064 } else {
1065 // R->R always works, but we have to avoid a check-cast to an interface.
1066 return !dst.isInterface() || dst.isAssignableFrom(src);
1067 }
1068 }
1069
1070 private boolean canConvertParameters(Class<?>[] srcTypes, Class<?>[] dstTypes) {
1071 for (int i = 0; i < srcTypes.length; i++) {
1072 if (!canConvert(srcTypes[i], dstTypes[i])) {
1073 return false;
1074 }
1075 }
1076 return true;
1077 }
1078
1079 /*non-public*/
1080 static boolean canConvert(Class<?> src, Class<?> dst) {
1081 // short-circuit a few cases:
1082 if (src == dst || src == Object.class || dst == Object.class) return true;
1083 // the remainder of this logic is documented in MethodHandle.asType
1084 if (src.isPrimitive()) {
1085 // can force void to an explicit null, a la reflect.Method.invoke
1086 // can also force void to a primitive zero, by analogy
1087 if (src == void.class) return true; //or !dst.isPrimitive()?
1088 Wrapper sw = Wrapper.forPrimitiveType(src);
1089 if (dst.isPrimitive()) {
1090 // P->P must widen
1091 return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw);
1092 } else {
1093 // P->R must box and widen
1094 return dst.isAssignableFrom(sw.wrapperType());
1095 }
1096 } else if (dst.isPrimitive()) {
1097 // any value can be dropped
1098 if (dst == void.class) return true;
1099 Wrapper dw = Wrapper.forPrimitiveType(dst);
1100 // R->P must be able to unbox (from a dynamically chosen type) and widen
1101 // For example:
1102 // Byte/Number/Comparable/Object -> dw:Byte -> byte.
1103 // Character/Comparable/Object -> dw:Character -> char
1104 // Boolean/Comparable/Object -> dw:Boolean -> boolean
1105 // This means that dw must be cast-compatible with src.
1106 if (src.isAssignableFrom(dw.wrapperType())) {
1107 return true;
1108 }
1109 // The above does not work if the source reference is strongly typed
1110 // to a wrapper whose primitive must be widened. For example:
1111 // Byte -> unbox:byte -> short/int/long/float/double
1112 // Character -> unbox:char -> int/long/float/double
1113 if (Wrapper.isWrapperType(src) &&
1114 dw.isConvertibleFrom(Wrapper.forWrapperType(src))) {
1115 // can unbox from src and then widen to dst
1116 return true;
1117 }
1118 // We have already covered cases which arise due to runtime unboxing
1119 // of a reference type which covers several wrapper types:
1120 // Object -> cast:Integer -> unbox:int -> long/float/double
1121 // Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double
1122 // An marginal case is Number -> dw:Character -> char, which would be OK if there were a
1123 // subclass of Number which wraps a value that can convert to char.
1124 // Since there is none, we don't need an extra check here to cover char or boolean.
1125 return false;
1126 } else {
1127 // R->R always works, since null is always valid dynamically
1128 return true;
1129 }
1130 }
1131
1132 //--- Queries which have to do with the bytecode architecture
1133
1134 /** Reports the number of JVM stack slots required to invoke a method
1135 * of this type. Note that (for historical reasons) the JVM requires
1136 * a second stack slot to pass long and double arguments.
1137 * So this method returns {@link #parameterCount() parameterCount} plus the
1138 * number of long and double parameters (if any).
1139 * <p>
1140 * This method is included for the benefit of applications that must
1141 * generate bytecodes that process method handles and invokedynamic.
1142 * @return the number of JVM stack slots for this type's parameters
1143 */
1144 /*non-public*/
1145 int parameterSlotCount() {
1146 return form.parameterSlotCount();
1147 }
1148
1149 /*non-public*/
1150 Invokers invokers() {
1151 Invokers inv = invokers;
1152 if (inv != null) return inv;
1153 invokers = inv = new Invokers(this);
1154 return inv;
1155 }
1156
1157 /**
1158 * Finds or creates an instance of a method type of the given method descriptor
1159 * (JVMS {@jvms 4.3.3}). This method is a convenience method for
1160 * {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
1161 * Any class or interface name embedded in the descriptor string will be
1162 * resolved by the given loader (or if it is {@code null}, on the system class loader).
1163 *
1164 * @apiNote
1165 * It is possible to encounter method types that have valid descriptors but
1166 * cannot be constructed by this method, because their component types are
1167 * not visible from a common class loader.
1168 * <p>
1169 * This method is included for the benefit of applications that must
1170 * generate bytecodes that process method handles and {@code invokedynamic}.
1171 * @param descriptor a method descriptor string
1172 * @param loader the class loader in which to look up the types
1173 * @return a method type of the given method descriptor
1174 * @throws NullPointerException if the string is {@code null}
1175 * @throws IllegalArgumentException if the string is not a method descriptor
1176 * @throws TypeNotPresentException if a named type cannot be found
1177 * @throws SecurityException if the security manager is present and
1178 * {@code loader} is {@code null} and the caller does not have the
1179 * {@link RuntimePermission}{@code ("getClassLoader")}
1180 * @jvms 4.3.3 Method Descriptors
1181 */
1182 public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader)
1183 throws IllegalArgumentException, TypeNotPresentException
1184 {
1185 if (loader == null) {
1186 @SuppressWarnings("removal")
1187 SecurityManager sm = System.getSecurityManager();
1188 if (sm != null) {
1189 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
1190 }
1191 }
1192 return fromDescriptor(descriptor,
1193 (loader == null) ? ClassLoader.getSystemClassLoader() : loader);
1194 }
1195
1196 /**
1197 * Same as {@link #fromMethodDescriptorString(String, ClassLoader)}, but
1198 * {@code null} ClassLoader means the bootstrap loader is used here.
1199 * <p>
1200 * IMPORTANT: This method is preferable for JDK internal use as it more
1201 * correctly interprets {@code null} ClassLoader than
1202 * {@link #fromMethodDescriptorString(String, ClassLoader)}.
1203 * Use of this method also avoids early initialization issues when system
1204 * ClassLoader is not initialized yet.
1205 */
1206 static MethodType fromDescriptor(String descriptor, ClassLoader loader)
1207 throws IllegalArgumentException, TypeNotPresentException
1208 {
1209 if (!descriptor.startsWith("(") || // also generates NPE if needed
1210 descriptor.indexOf(')') < 0 ||
1211 descriptor.indexOf('.') >= 0)
1212 throw newIllegalArgumentException("not a method descriptor: "+descriptor);
1213 List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader);
1214 Class<?> rtype = types.remove(types.size() - 1);
1215 Class<?>[] ptypes = listToArray(types);
1216 return methodType(rtype, ptypes, true);
1217 }
1218
1219 /**
1220 * {@return the descriptor string for this method type} This method
1221 * is equivalent to calling {@link #descriptorString() MethodType::descriptorString}.
1222 *
1223 * @apiNote
1224 * This is not a strict inverse of {@link #fromMethodDescriptorString
1225 * fromMethodDescriptorString} which requires a method type descriptor
1226 * (JVMS {@jvms 4.3.3}) and a suitable class loader argument.
1227 * Two distinct {@code MethodType} objects can have an identical
1228 * descriptor string as distinct classes can have the same name
1229 * but different class loaders.
1230 *
1231 * <p>
1232 * This method is included for the benefit of applications that must
1233 * generate bytecodes that process method handles and {@code invokedynamic}.
1234 * @jvms 4.3.3 Method Descriptors
1235 * @see <a href="#descriptor">Nominal Descriptor for {@code MethodType}</a>
1236 */
1237 public String toMethodDescriptorString() {
1238 String desc = methodDescriptor;
1239 if (desc == null) {
1240 desc = BytecodeDescriptor.unparseMethod(this.rtype, this.ptypes);
1241 methodDescriptor = desc;
1242 }
1243 return desc;
1244 }
1245
1246 /**
1247 * {@return the descriptor string for this method type}
1248 *
1249 * <p>
1250 * If this method type can be {@linkplain ##descriptor described nominally},
1251 * then the result is a method type descriptor (JVMS {@jvms 4.3.3}).
1252 * {@link MethodTypeDesc MethodTypeDesc} for this method type
1253 * can be produced by calling {@link MethodTypeDesc#ofDescriptor(String)
1254 * MethodTypeDesc::ofDescriptor} with the result descriptor string.
1255 * <p>
1256 * If this method type cannot be {@linkplain ##descriptor described nominally}
1257 * and the result is a string of the form:
1258 * <blockquote>{@code "(<parameter-descriptors>)<return-descriptor>"}</blockquote>
1259 * where {@code <parameter-descriptors>} is the concatenation of the
1260 * {@linkplain Class#descriptorString() descriptor string} of all
1261 * of the parameter types and the {@linkplain Class#descriptorString() descriptor string}
1262 * of the return type. No {@link java.lang.constant.MethodTypeDesc MethodTypeDesc}
1263 * can be produced from the result string.
1264 *
1265 * @since 12
1266 * @jvms 4.3.3 Method Descriptors
1267 * @see <a href="#descriptor">Nominal Descriptor for {@code MethodType}</a>
1268 */
1269 @Override
1270 public String descriptorString() {
1271 return toMethodDescriptorString();
1272 }
1273
1274 /*non-public*/
1275 static String toFieldDescriptorString(Class<?> cls) {
1276 return BytecodeDescriptor.unparse(cls);
1277 }
1278
1279 /**
1280 * Returns a nominal descriptor for this instance, if one can be
1281 * constructed, or an empty {@link Optional} if one cannot be.
1282 *
1283 * @return An {@link Optional} containing the resulting nominal descriptor,
1284 * or an empty {@link Optional} if one cannot be constructed.
1285 * @since 12
1286 * @see <a href="#descriptor">Nominal Descriptor for {@code MethodType}</a>
1287 */
1288 @Override
1289 public Optional<MethodTypeDesc> describeConstable() {
1290 var retDesc = returnType().describeConstable();
1291 if (retDesc.isEmpty())
1292 return Optional.empty();
1293
1294 if (parameterCount() == 0)
1295 return Optional.of(MethodTypeDesc.of(retDesc.get()));
1296
1297 var params = new ClassDesc[parameterCount()];
1298 for (int i = 0; i < params.length; i++) {
1299 var paramDesc = parameterType(i).describeConstable();
1300 if (paramDesc.isEmpty())
1301 return Optional.empty();
1302 params[i] = paramDesc.get();
1303 }
1304 return Optional.of(MethodTypeDesc.of(retDesc.get(), params));
1305 }
1306
1307 //--- Serialization.
1308
1309 /**
1310 * There are no serializable fields for {@code MethodType}.
1311 */
1312 @java.io.Serial
1313 private static final java.io.ObjectStreamField[] serialPersistentFields = { };
1314
1315 /**
1316 * Save the {@code MethodType} instance to a stream.
1317 *
1318 * @serialData
1319 * For portability, the serialized format does not refer to named fields.
1320 * Instead, the return type and parameter type arrays are written directly
1321 * from the {@code writeObject} method, using two calls to {@code s.writeObject}
1322 * as follows:
1323 * <blockquote><pre>{@code
1324 s.writeObject(this.returnType());
1325 s.writeObject(this.parameterArray());
1326 * }</pre></blockquote>
1327 * <p>
1328 * The deserialized field values are checked as if they were
1329 * provided to the factory method {@link #methodType(Class,Class[]) methodType}.
1330 * For example, null values, or {@code void} parameter types,
1331 * will lead to exceptions during deserialization.
1332 * @param s the stream to write the object to
1333 * @throws java.io.IOException if there is a problem writing the object
1334 */
1335 @java.io.Serial
1336 private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
1337 s.defaultWriteObject(); // requires serialPersistentFields to be an empty array
1338 s.writeObject(returnType());
1339 s.writeObject(parameterArray());
1340 }
1341
1342 /**
1343 * Reconstitute the {@code MethodType} instance from a stream (that is,
1344 * deserialize it).
1345 * This instance is a scratch object with bogus final fields.
1346 * It provides the parameters to the factory method called by
1347 * {@link #readResolve readResolve}.
1348 * After that call it is discarded.
1349 * @param s the stream to read the object from
1350 * @throws java.io.IOException if there is a problem reading the object
1351 * @throws ClassNotFoundException if one of the component classes cannot be resolved
1352 * @see #readResolve
1353 * @see #writeObject
1354 */
1355 @java.io.Serial
1356 private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
1357 // Assign defaults in case this object escapes
1358 UNSAFE.putReference(this, OffsetHolder.rtypeOffset, void.class);
1359 UNSAFE.putReference(this, OffsetHolder.ptypesOffset, NO_PTYPES);
1360
1361 s.defaultReadObject(); // requires serialPersistentFields to be an empty array
1362
1363 Class<?> returnType = (Class<?>) s.readObject();
1364 Class<?>[] parameterArray = (Class<?>[]) s.readObject();
1365
1366 // Verify all operands, and make sure ptypes is unshared
1367 // Cache the new MethodType for readResolve
1368 wrapAlt = new MethodType[]{MethodType.methodType(returnType, parameterArray)};
1369 }
1370
1371 // Support for resetting final fields while deserializing. Implement Holder
1372 // pattern to make the rarely needed offset calculation lazy.
1373 private static class OffsetHolder {
1374 static final long rtypeOffset
1375 = UNSAFE.objectFieldOffset(MethodType.class, "rtype");
1376
1377 static final long ptypesOffset
1378 = UNSAFE.objectFieldOffset(MethodType.class, "ptypes");
1379 }
1380
1381 /**
1382 * Resolves and initializes a {@code MethodType} object
1383 * after serialization.
1384 * @return the fully initialized {@code MethodType} object
1385 */
1386 @java.io.Serial
1387 private Object readResolve() {
1388 // Do not use a trusted path for deserialization:
1389 // return makeImpl(rtype, ptypes, true);
1390 // Verify all operands, and make sure ptypes is unshared:
1391 // Return a new validated MethodType for the rtype and ptypes passed from readObject.
1392 MethodType mt = ((MethodType[])wrapAlt)[0];
1393 wrapAlt = null;
1394 return mt;
1395 }
1396 }