1 /*
2 * Copyright (c) 2008, 2020, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang.invoke;
27
28 import java.lang.constant.ClassDesc;
29 import java.lang.constant.Constable;
30 import java.lang.constant.MethodTypeDesc;
31 import java.lang.ref.Reference;
32 import java.lang.ref.ReferenceQueue;
33 import java.lang.ref.WeakReference;
34 import java.util.Arrays;
35 import java.util.Collections;
36 import java.util.List;
37 import java.util.NoSuchElementException;
38 import java.util.Objects;
39 import java.util.Optional;
40 import java.util.StringJoiner;
41 import java.util.concurrent.ConcurrentHashMap;
42 import java.util.concurrent.ConcurrentMap;
43 import java.util.stream.Stream;
44
45 import jdk.internal.vm.annotation.Stable;
46 import sun.invoke.util.BytecodeDescriptor;
47 import sun.invoke.util.VerifyType;
48 import sun.invoke.util.Wrapper;
49 import sun.security.util.SecurityConstants;
50
51 import static java.lang.invoke.MethodHandleStatics.UNSAFE;
52 import static java.lang.invoke.MethodHandleStatics.newIllegalArgumentException;
53 import static java.lang.invoke.MethodType.fromDescriptor;
54
55 /**
56 * A method type represents the arguments and return type accepted and
57 * returned by a method handle, or the arguments and return type passed
58 * and expected by a method handle caller. Method types must be properly
59 * matched between a method handle and all its callers,
60 * and the JVM's operations enforce this matching at, specifically
61 * during calls to {@link MethodHandle#invokeExact MethodHandle.invokeExact}
62 * and {@link MethodHandle#invoke MethodHandle.invoke}, and during execution
63 * of {@code invokedynamic} instructions.
64 * <p>
65 * The structure is a return type accompanied by any number of parameter types.
66 * The types (primitive, {@code void}, and reference) are represented by {@link Class} objects.
67 * (For ease of exposition, we treat {@code void} as if it were a type.
68 * In fact, it denotes the absence of a return type.)
69 * <p>
70 * All instances of {@code MethodType} are immutable.
71 * Two instances are completely interchangeable if they compare equal.
72 * Equality depends on pairwise correspondence of the return and parameter types and on nothing else.
73 * <p>
74 * This type can be created only by factory methods.
75 * All factory methods may cache values, though caching is not guaranteed.
76 * Some factory methods are static, while others are virtual methods which
77 * modify precursor method types, e.g., by changing a selected parameter.
78 * <p>
79 * Factory methods which operate on groups of parameter types
80 * are systematically presented in two versions, so that both Java arrays and
81 * Java lists can be used to work with groups of parameter types.
82 * The query methods {@code parameterArray} and {@code parameterList}
83 * also provide a choice between arrays and lists.
84 * <p>
85 * {@code MethodType} objects are sometimes derived from bytecode instructions
86 * such as {@code invokedynamic}, specifically from the type descriptor strings associated
87 * with the instructions in a class file's constant pool.
88 * <p>
89 * Like classes and strings, method types can also be represented directly
90 * in a class file's constant pool as constants.
91 * A method type may be loaded by an {@code ldc} instruction which refers
92 * to a suitable {@code CONSTANT_MethodType} constant pool entry.
93 * The entry refers to a {@code CONSTANT_Utf8} spelling for the descriptor string.
94 * (For full details on method type constants, see sections {@jvms
95 * 4.4.8} and {@jvms 5.4.3.5} of the Java Virtual Machine
96 * Specification.)
97 * <p>
98 * When the JVM materializes a {@code MethodType} from a descriptor string,
99 * all classes named in the descriptor must be accessible, and will be loaded.
100 * (But the classes need not be initialized, as is the case with a {@code CONSTANT_Class}.)
101 * This loading may occur at any time before the {@code MethodType} object is first derived.
102 * <p>
103 * <b><a id="descriptor">Nominal Descriptors</a></b>
104 * <p>
105 * A {@code MethodType} can be described in {@linkplain MethodTypeDesc nominal form}
106 * if and only if all of the parameter types and return type can be described
107 * with a {@link Class#describeConstable() nominal descriptor} represented by
108 * {@link ClassDesc}. If a method type can be described norminally, then:
109 * <ul>
110 * <li>The method type has a {@link MethodTypeDesc nominal descriptor}
111 * returned by {@link #describeConstable() MethodType::describeConstable}.</li>
112 * <li>The descriptor string returned by
113 * {@link #descriptorString() MethodType::descriptorString} or
114 * {@link #toMethodDescriptorString() MethodType::toMethodDescriptorString}
115 * for the method type is a valid type descriptor (JVMS {@jvms 4.3.3}).</li>
116 * </ul>
117 * <p>
118 * If any of the parameter types or return type cannot be described
119 * nominally, i.e. {@link Class#describeConstable() Class::describeConstable}
120 * returns an empty optional for that type,
121 * then the method type cannot be described in nominal form:
122 * <ul>
123 * <li>The method type has no {@link MethodTypeDesc nominal descriptor} and
124 * {@link #describeConstable() MethodType::describeConstable} returns
125 * an empty optional.</li>
126 * <li>The descriptor string returned by
127 * {@link #descriptorString() MethodType::descriptorString} or
128 * {@link #toMethodDescriptorString() MethodType::toMethodDescriptorString}
129 * for the method type is not a valid type descriptor string.</li>
130 * </ul>
131 *
132 * @author John Rose, JSR 292 EG
133 * @since 1.7
134 */
135 public final
136 class MethodType
137 implements Constable,
138 TypeDescriptor.OfMethod<Class<?>, MethodType>,
139 java.io.Serializable {
140 @java.io.Serial
141 private static final long serialVersionUID = 292L; // {rtype, {ptype...}}
142
143 // The rtype and ptypes fields define the structural identity of the method type:
144 private final @Stable Class<?> rtype;
145 private final @Stable Class<?>[] ptypes;
146
147 // The remaining fields are caches of various sorts:
148 private @Stable MethodTypeForm form; // erased form, plus cached data about primitives
149 private @Stable MethodType wrapAlt; // alternative wrapped/unwrapped version
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 private static void checkRtype(Class<?> rtype) {
202 Objects.requireNonNull(rtype);
203 }
204 private static void checkPtype(Class<?> ptype) {
205 Objects.requireNonNull(ptype);
206 if (ptype == void.class)
207 throw newIllegalArgumentException("parameter type cannot be void");
208 }
209 /** Return number of extra slots (count of long/double args). */
210 private static int checkPtypes(Class<?>[] ptypes) {
211 int slots = 0;
212 for (Class<?> ptype : ptypes) {
213 checkPtype(ptype);
214 if (ptype == double.class || ptype == long.class) {
215 slots++;
216 }
217 }
218 checkSlotCount(ptypes.length + slots);
219 return slots;
220 }
221
222 static {
223 // MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work:
224 assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0);
225 }
226 static void checkSlotCount(int count) {
227 if ((count & MAX_JVM_ARITY) != count)
228 throw newIllegalArgumentException("bad parameter count "+count);
229 }
230 private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) {
231 if (num instanceof Integer) num = "bad index: "+num;
232 return new IndexOutOfBoundsException(num.toString());
233 }
234
235 static final ConcurrentWeakInternSet<MethodType> internTable = new ConcurrentWeakInternSet<>();
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 makeImpl(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 makeImpl(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 Class<?>[] ptypes1 = new Class<?>[1+ptypes.length];
284 ptypes1[0] = ptype0;
285 System.arraycopy(ptypes, 0, ptypes1, 1, ptypes.length);
286 return makeImpl(rtype, ptypes1, true);
287 }
288
289 /**
290 * Finds or creates a method type with the given components.
291 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
292 * The resulting method has no parameter types.
293 * @param rtype the return type
294 * @return a method type with the given return value
295 * @throws NullPointerException if {@code rtype} is null
296 */
297 public static MethodType methodType(Class<?> rtype) {
298 return makeImpl(rtype, NO_PTYPES, true);
299 }
300
301 /**
302 * Finds or creates a method type with the given components.
303 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
304 * The resulting method has the single given parameter type.
305 * @param rtype the return type
306 * @param ptype0 the parameter type
307 * @return a method type with the given return value and parameter type
308 * @throws NullPointerException if {@code rtype} or {@code ptype0} is null
309 * @throws IllegalArgumentException if {@code ptype0} is {@code void.class}
310 */
311 public static MethodType methodType(Class<?> rtype, Class<?> ptype0) {
312 return makeImpl(rtype, new Class<?>[]{ ptype0 }, true);
313 }
314
315 /**
316 * Finds or creates a method type with the given components.
317 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
318 * The resulting method has the same parameter types as {@code ptypes},
319 * and the specified return type.
320 * @param rtype the return type
321 * @param ptypes the method type which supplies the parameter types
322 * @return a method type with the given components
323 * @throws NullPointerException if {@code rtype} or {@code ptypes} is null
324 */
325 public static MethodType methodType(Class<?> rtype, MethodType ptypes) {
326 return makeImpl(rtype, ptypes.ptypes, true);
327 }
328
329 /**
330 * Sole factory method to find or create an interned method type.
331 * @param rtype desired return type
332 * @param ptypes desired parameter types
333 * @param trusted whether the ptypes can be used without cloning
334 * @return the unique method type of the desired structure
335 */
336 /*trusted*/
337 static MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {
338 if (ptypes.length == 0) {
339 ptypes = NO_PTYPES; trusted = true;
340 }
341 MethodType primordialMT = new MethodType(rtype, ptypes);
342 MethodType mt = internTable.get(primordialMT);
343 if (mt != null)
344 return mt;
345
346 // promote the object to the Real Thing, and reprobe
347 MethodType.checkRtype(rtype);
348 if (trusted) {
349 MethodType.checkPtypes(ptypes);
350 mt = primordialMT;
351 } else {
352 // Make defensive copy then validate
353 ptypes = Arrays.copyOf(ptypes, ptypes.length);
354 MethodType.checkPtypes(ptypes);
355 mt = new MethodType(rtype, ptypes);
356 }
357 mt.form = MethodTypeForm.findForm(mt);
358 return internTable.add(mt);
359 }
360 private static final @Stable MethodType[] objectOnlyTypes = new MethodType[20];
361
362 /**
363 * Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array.
364 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
365 * All parameters and the return type will be {@code Object},
366 * except the final array parameter if any, which will be {@code Object[]}.
367 * @param objectArgCount number of parameters (excluding the final array parameter if any)
368 * @param finalArray whether there will be a trailing array parameter, of type {@code Object[]}
369 * @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments
370 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true)
371 * @see #genericMethodType(int)
372 */
373 public static MethodType genericMethodType(int objectArgCount, boolean finalArray) {
374 MethodType mt;
375 checkSlotCount(objectArgCount);
376 int ivarargs = (!finalArray ? 0 : 1);
377 int ootIndex = objectArgCount*2 + ivarargs;
378 if (ootIndex < objectOnlyTypes.length) {
379 mt = objectOnlyTypes[ootIndex];
380 if (mt != null) return mt;
381 }
382 Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs];
383 Arrays.fill(ptypes, Object.class);
384 if (ivarargs != 0) ptypes[objectArgCount] = Object[].class;
385 mt = makeImpl(Object.class, ptypes, true);
386 if (ootIndex < objectOnlyTypes.length) {
387 objectOnlyTypes[ootIndex] = mt; // cache it here also!
388 }
389 return mt;
390 }
391
392 /**
393 * Finds or creates a method type whose components are all {@code Object}.
394 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
395 * All parameters and the return type will be Object.
396 * @param objectArgCount number of parameters
397 * @return a generally applicable method type, for all calls of the given argument count
398 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255
399 * @see #genericMethodType(int, boolean)
400 */
401 public static MethodType genericMethodType(int objectArgCount) {
402 return genericMethodType(objectArgCount, false);
403 }
404
405 /**
406 * Finds or creates a method type with a single different parameter type.
407 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
408 * @param num the index (zero-based) of the parameter type to change
409 * @param nptype a new parameter type to replace the old one with
410 * @return the same type, except with the selected parameter changed
411 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
412 * @throws IllegalArgumentException if {@code nptype} is {@code void.class}
413 * @throws NullPointerException if {@code nptype} is null
414 */
415 public MethodType changeParameterType(int num, Class<?> nptype) {
416 if (parameterType(num) == nptype) return this;
417 checkPtype(nptype);
418 Class<?>[] nptypes = ptypes.clone();
419 nptypes[num] = nptype;
420 return makeImpl(rtype, nptypes, true);
421 }
422
423 /**
424 * Finds or creates a method type with additional parameter types.
425 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
426 * @param num the position (zero-based) of the inserted parameter type(s)
427 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
428 * @return the same type, except with the selected parameter(s) inserted
429 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
430 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
431 * or if the resulting method type would have more than 255 parameter slots
432 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
433 */
434 public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) {
435 int len = ptypes.length;
436 if (num < 0 || num > len)
437 throw newIndexOutOfBoundsException(num);
438 int ins = checkPtypes(ptypesToInsert);
439 checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins);
440 int ilen = ptypesToInsert.length;
441 if (ilen == 0) return this;
442 Class<?>[] nptypes = new Class<?>[len + ilen];
443 if (num > 0) {
444 System.arraycopy(ptypes, 0, nptypes, 0, num);
445 }
446 System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen);
447 if (num < len) {
448 System.arraycopy(ptypes, num, nptypes, num+ilen, len-num);
449 }
450 return makeImpl(rtype, nptypes, true);
451 }
452
453 /**
454 * Finds or creates a method type with additional parameter types.
455 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
456 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
457 * @return the same type, except with the selected parameter(s) appended
458 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
459 * or if the resulting method type would have more than 255 parameter slots
460 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
461 */
462 public MethodType appendParameterTypes(Class<?>... ptypesToInsert) {
463 return insertParameterTypes(parameterCount(), ptypesToInsert);
464 }
465
466 /**
467 * Finds or creates a method type with additional parameter types.
468 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
469 * @param num the position (zero-based) of the inserted parameter type(s)
470 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
471 * @return the same type, except with the selected parameter(s) inserted
472 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
473 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
474 * or if the resulting method type would have more than 255 parameter slots
475 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
476 */
477 public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) {
478 return insertParameterTypes(num, listToArray(ptypesToInsert));
479 }
480
481 /**
482 * Finds or creates a method type with additional parameter types.
483 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
484 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
485 * @return the same type, except with the selected parameter(s) appended
486 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
487 * or if the resulting method type would have more than 255 parameter slots
488 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
489 */
490 public MethodType appendParameterTypes(List<Class<?>> ptypesToInsert) {
491 return insertParameterTypes(parameterCount(), ptypesToInsert);
492 }
493
494 /**
495 * Finds or creates a method type with modified parameter types.
496 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
497 * @param start the position (zero-based) of the first replaced parameter type(s)
498 * @param end the position (zero-based) after the last replaced parameter type(s)
499 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
500 * @return the same type, except with the selected parameter(s) replaced
501 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
502 * or if {@code end} is negative or greater than {@code parameterCount()}
503 * or if {@code start} is greater than {@code end}
504 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
505 * or if the resulting method type would have more than 255 parameter slots
506 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
507 */
508 /*non-public*/
509 MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) {
510 if (start == end)
511 return insertParameterTypes(start, ptypesToInsert);
512 int len = ptypes.length;
513 if (!(0 <= start && start <= end && end <= len))
514 throw newIndexOutOfBoundsException("start="+start+" end="+end);
515 int ilen = ptypesToInsert.length;
516 if (ilen == 0)
517 return dropParameterTypes(start, end);
518 return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert);
519 }
520
521 /** Replace the last arrayLength parameter types with the component type of arrayType.
522 * @param arrayType any array type
523 * @param pos position at which to spread
524 * @param arrayLength the number of parameter types to change
525 * @return the resulting type
526 */
527 /*non-public*/
528 MethodType asSpreaderType(Class<?> arrayType, int pos, int arrayLength) {
529 assert(parameterCount() >= arrayLength);
530 int spreadPos = pos;
531 if (arrayLength == 0) return this; // nothing to change
532 if (arrayType == Object[].class) {
533 if (isGeneric()) return this; // nothing to change
534 if (spreadPos == 0) {
535 // no leading arguments to preserve; go generic
536 MethodType res = genericMethodType(arrayLength);
537 if (rtype != Object.class) {
538 res = res.changeReturnType(rtype);
539 }
540 return res;
541 }
542 }
543 Class<?> elemType = arrayType.getComponentType();
544 assert(elemType != null);
545 for (int i = spreadPos; i < spreadPos + arrayLength; i++) {
546 if (ptypes[i] != elemType) {
547 Class<?>[] fixedPtypes = ptypes.clone();
548 Arrays.fill(fixedPtypes, i, spreadPos + arrayLength, elemType);
549 return methodType(rtype, fixedPtypes);
550 }
551 }
552 return this; // arguments check out; no change
553 }
554
555 /** Return the leading parameter type, which must exist and be a reference.
556 * @return the leading parameter type, after error checks
557 */
558 /*non-public*/
559 Class<?> leadingReferenceParameter() {
560 Class<?> ptype;
561 if (ptypes.length == 0 ||
562 (ptype = ptypes[0]).isPrimitive())
563 throw newIllegalArgumentException("no leading reference parameter");
564 return ptype;
565 }
566
567 /** Delete the last parameter type and replace it with arrayLength copies of the component type of arrayType.
568 * @param arrayType any array type
569 * @param pos position at which to insert parameters
570 * @param arrayLength the number of parameter types to insert
571 * @return the resulting type
572 */
573 /*non-public*/
574 MethodType asCollectorType(Class<?> arrayType, int pos, int arrayLength) {
575 assert(parameterCount() >= 1);
576 assert(pos < ptypes.length);
577 assert(ptypes[pos].isAssignableFrom(arrayType));
578 MethodType res;
579 if (arrayType == Object[].class) {
580 res = genericMethodType(arrayLength);
581 if (rtype != Object.class) {
582 res = res.changeReturnType(rtype);
583 }
584 } else {
585 Class<?> elemType = arrayType.getComponentType();
586 assert(elemType != null);
587 res = methodType(rtype, Collections.nCopies(arrayLength, elemType));
588 }
589 if (ptypes.length == 1) {
590 return res;
591 } else {
592 // insert after (if need be), then before
593 if (pos < ptypes.length - 1) {
594 res = res.insertParameterTypes(arrayLength, Arrays.copyOfRange(ptypes, pos + 1, ptypes.length));
595 }
596 return res.insertParameterTypes(0, Arrays.copyOf(ptypes, pos));
597 }
598 }
599
600 /**
601 * Finds or creates a method type with some parameter types omitted.
602 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
603 * @param start the index (zero-based) of the first parameter type to remove
604 * @param end the index (greater than {@code start}) of the first parameter type after not to remove
605 * @return the same type, except with the selected parameter(s) removed
606 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
607 * or if {@code end} is negative or greater than {@code parameterCount()}
608 * or if {@code start} is greater than {@code end}
609 */
610 public MethodType dropParameterTypes(int start, int end) {
611 int len = ptypes.length;
612 if (!(0 <= start && start <= end && end <= len))
613 throw newIndexOutOfBoundsException("start="+start+" end="+end);
614 if (start == end) return this;
615 Class<?>[] nptypes;
616 if (start == 0) {
617 if (end == len) {
618 // drop all parameters
619 nptypes = NO_PTYPES;
620 } else {
621 // drop initial parameter(s)
622 nptypes = Arrays.copyOfRange(ptypes, end, len);
623 }
624 } else {
625 if (end == len) {
626 // drop trailing parameter(s)
627 nptypes = Arrays.copyOfRange(ptypes, 0, start);
628 } else {
629 int tail = len - end;
630 nptypes = Arrays.copyOfRange(ptypes, 0, start + tail);
631 System.arraycopy(ptypes, end, nptypes, start, tail);
632 }
633 }
634 return makeImpl(rtype, nptypes, true);
635 }
636
637 /**
638 * Finds or creates a method type with a different return type.
639 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
640 * @param nrtype a return parameter type to replace the old one with
641 * @return the same type, except with the return type change
642 * @throws NullPointerException if {@code nrtype} is null
643 */
644 public MethodType changeReturnType(Class<?> nrtype) {
645 if (returnType() == nrtype) return this;
646 return makeImpl(nrtype, ptypes, true);
647 }
648
649 /**
650 * Reports if this type contains a primitive argument or return value.
651 * The return type {@code void} counts as a primitive.
652 * @return true if any of the types are primitives
653 */
654 public boolean hasPrimitives() {
655 return form.hasPrimitives();
656 }
657
658 /**
659 * Reports if this type contains a wrapper argument or return value.
660 * Wrappers are types which box primitive values, such as {@link Integer}.
661 * The reference type {@code java.lang.Void} counts as a wrapper,
662 * if it occurs as a return type.
663 * @return true if any of the types are wrappers
664 */
665 public boolean hasWrappers() {
666 return unwrap() != this;
667 }
668
669 /**
670 * Erases all reference types to {@code Object}.
671 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
672 * All primitive types (including {@code void}) will remain unchanged.
673 * @return a version of the original type with all reference types replaced
674 */
675 public MethodType erase() {
676 return form.erasedType();
677 }
678
679 /**
680 * Erases all reference types to {@code Object}, and all subword types to {@code int}.
681 * This is the reduced type polymorphism used by private methods
682 * such as {@link MethodHandle#invokeBasic invokeBasic}.
683 * @return a version of the original type with all reference and subword types replaced
684 */
685 /*non-public*/
686 MethodType basicType() {
687 return form.basicType();
688 }
689
690 private static final @Stable Class<?>[] METHOD_HANDLE_ARRAY
691 = new Class<?>[] { MethodHandle.class };
692
693 /**
694 * @return a version of the original type with MethodHandle prepended as the first argument
695 */
696 /*non-public*/
697 MethodType invokerType() {
698 return insertParameterTypes(0, METHOD_HANDLE_ARRAY);
699 }
700
701 /**
702 * Converts all types, both reference and primitive, to {@code Object}.
703 * Convenience method for {@link #genericMethodType(int) genericMethodType}.
704 * The expression {@code type.wrap().erase()} produces the same value
705 * as {@code type.generic()}.
706 * @return a version of the original type with all types replaced
707 */
708 public MethodType generic() {
709 return genericMethodType(parameterCount());
710 }
711
712 /*non-public*/
713 boolean isGeneric() {
714 return this == erase() && !hasPrimitives();
715 }
716
717 /**
718 * Converts all primitive types to their corresponding wrapper types.
719 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
720 * All reference types (including wrapper types) will remain unchanged.
721 * A {@code void} return type is changed to the type {@code java.lang.Void}.
722 * The expression {@code type.wrap().erase()} produces the same value
723 * as {@code type.generic()}.
724 * @return a version of the original type with all primitive types replaced
725 */
726 public MethodType wrap() {
727 return hasPrimitives() ? wrapWithPrims(this) : this;
728 }
729
730 /**
731 * Converts all wrapper types to their corresponding primitive types.
732 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
733 * All primitive types (including {@code void}) will remain unchanged.
734 * A return type of {@code java.lang.Void} is changed to {@code void}.
735 * @return a version of the original type with all wrapper types replaced
736 */
737 public MethodType unwrap() {
738 MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this);
739 return unwrapWithNoPrims(noprims);
740 }
741
742 private static MethodType wrapWithPrims(MethodType pt) {
743 assert(pt.hasPrimitives());
744 MethodType wt = pt.wrapAlt;
745 if (wt == null) {
746 // fill in lazily
747 wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP, MethodTypeForm.WRAP);
748 assert(wt != null);
749 pt.wrapAlt = wt;
750 }
751 return wt;
752 }
753
754 private static MethodType unwrapWithNoPrims(MethodType wt) {
755 assert(!wt.hasPrimitives());
756 MethodType uwt = wt.wrapAlt;
757 if (uwt == null) {
758 // fill in lazily
759 uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP, MethodTypeForm.UNWRAP);
760 if (uwt == null)
761 uwt = wt; // type has no wrappers or prims at all
762 wt.wrapAlt = uwt;
763 }
764 return uwt;
765 }
766
767 /**
768 * Returns the parameter type at the specified index, within this method type.
769 * @param num the index (zero-based) of the desired parameter type
770 * @return the selected parameter type
771 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
772 */
773 public Class<?> parameterType(int num) {
774 return ptypes[num];
775 }
776 /**
777 * Returns the number of parameter types in this method type.
778 * @return the number of parameter types
779 */
780 public int parameterCount() {
781 return ptypes.length;
782 }
783 /**
784 * Returns the return type of this method type.
785 * @return the return type
786 */
787 public Class<?> returnType() {
788 return rtype;
789 }
790
791 /**
792 * Presents the parameter types as a list (a convenience method).
793 * The list will be immutable.
794 * @return the parameter types (as an immutable list)
795 */
796 public List<Class<?>> parameterList() {
797 return Collections.unmodifiableList(Arrays.asList(ptypes.clone()));
798 }
799
800 /**
801 * Returns the last parameter type of this method type.
802 * If this type has no parameters, the sentinel value
803 * {@code void.class} is returned instead.
804 * @apiNote
805 * <p>
806 * The sentinel value is chosen so that reflective queries can be
807 * made directly against the result value.
808 * The sentinel value cannot be confused with a real parameter,
809 * since {@code void} is never acceptable as a parameter type.
810 * For variable arity invocation modes, the expression
811 * {@link Class#getComponentType lastParameterType().getComponentType()}
812 * is useful to query the type of the "varargs" parameter.
813 * @return the last parameter type if any, else {@code void.class}
814 * @since 10
815 */
816 public Class<?> lastParameterType() {
817 int len = ptypes.length;
818 return len == 0 ? void.class : ptypes[len-1];
819 }
820
821 /**
822 * Presents the parameter types as an array (a convenience method).
823 * Changes to the array will not result in changes to the type.
824 * @return the parameter types (as a fresh copy if necessary)
825 */
826 public Class<?>[] parameterArray() {
827 return ptypes.clone();
828 }
829
830 /**
831 * Compares the specified object with this type for equality.
832 * That is, it returns {@code true} if and only if the specified object
833 * is also a method type with exactly the same parameters and return type.
834 * @param x object to compare
835 * @see Object#equals(Object)
836 */
837 // This implementation may also return true if x is a WeakEntry containing
838 // a method type that is equal to this. This is an internal implementation
839 // detail to allow for faster method type lookups.
840 // See ConcurrentWeakInternSet.WeakEntry#equals(Object)
841 @Override
842 public boolean equals(Object x) {
843 if (this == x) {
844 return true;
845 }
846 if (x instanceof MethodType) {
847 return equals((MethodType)x);
848 }
849 if (x instanceof ConcurrentWeakInternSet.WeakEntry) {
850 Object o = ((ConcurrentWeakInternSet.WeakEntry)x).get();
851 if (o instanceof MethodType) {
852 return equals((MethodType)o);
853 }
854 }
855 return false;
856 }
857
858 private boolean equals(MethodType that) {
859 return this.rtype == that.rtype
860 && Arrays.equals(this.ptypes, that.ptypes);
861 }
862
863 /**
864 * Returns the hash code value for this method type.
865 * It is defined to be the same as the hashcode of a List
866 * whose elements are the return type followed by the
867 * parameter types.
868 * @return the hash code value for this method type
869 * @see Object#hashCode()
870 * @see #equals(Object)
871 * @see List#hashCode()
872 */
873 @Override
874 public int hashCode() {
875 int hashCode = 31 + rtype.hashCode();
876 for (Class<?> ptype : ptypes)
877 hashCode = 31 * hashCode + ptype.hashCode();
878 return hashCode;
879 }
880
881 /**
882 * Returns a string representation of the method type,
883 * of the form {@code "(PT0,PT1...)RT"}.
884 * The string representation of a method type is a
885 * parenthesis enclosed, comma separated list of type names,
886 * followed immediately by the return type.
887 * <p>
888 * Each type is represented by its
889 * {@link java.lang.Class#getSimpleName simple name}.
890 */
891 @Override
892 public String toString() {
893 StringJoiner sj = new StringJoiner(",", "(",
894 ")" + rtype.getSimpleName());
895 for (int i = 0; i < ptypes.length; i++) {
896 sj.add(ptypes[i].getSimpleName());
897 }
898 return sj.toString();
899 }
900
901 /** True if my parameter list is effectively identical to the given full list,
902 * after skipping the given number of my own initial parameters.
903 * In other words, after disregarding {@code skipPos} parameters,
904 * my remaining parameter list is no longer than the {@code fullList}, and
905 * is equal to the same-length initial sublist of {@code fullList}.
906 */
907 /*non-public*/
908 boolean effectivelyIdenticalParameters(int skipPos, List<Class<?>> fullList) {
909 int myLen = ptypes.length, fullLen = fullList.size();
910 if (skipPos > myLen || myLen - skipPos > fullLen)
911 return false;
912 List<Class<?>> myList = Arrays.asList(ptypes);
913 if (skipPos != 0) {
914 myList = myList.subList(skipPos, myLen);
915 myLen -= skipPos;
916 }
917 if (fullLen == myLen)
918 return myList.equals(fullList);
919 else
920 return myList.equals(fullList.subList(0, myLen));
921 }
922
923 /** True if the old return type can always be viewed (w/o casting) under new return type,
924 * and the new parameters can be viewed (w/o casting) under the old parameter types.
925 */
926 /*non-public*/
927 boolean isViewableAs(MethodType newType, boolean keepInterfaces) {
928 if (!VerifyType.isNullConversion(returnType(), newType.returnType(), keepInterfaces))
929 return false;
930 if (form == newType.form && form.erasedType == this)
931 return true; // my reference parameters are all Object
932 if (ptypes == newType.ptypes)
933 return true;
934 int argc = parameterCount();
935 if (argc != newType.parameterCount())
936 return false;
937 for (int i = 0; i < argc; i++) {
938 if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i), keepInterfaces))
939 return false;
940 }
941 return true;
942 }
943 /*non-public*/
944 boolean isConvertibleTo(MethodType newType) {
945 MethodTypeForm oldForm = this.form();
946 MethodTypeForm newForm = newType.form();
947 if (oldForm == newForm)
948 // same parameter count, same primitive/object mix
949 return true;
950 if (!canConvert(returnType(), newType.returnType()))
951 return false;
952 Class<?>[] srcTypes = newType.ptypes;
953 Class<?>[] dstTypes = ptypes;
954 if (srcTypes == dstTypes)
955 return true;
956 int argc;
957 if ((argc = srcTypes.length) != dstTypes.length)
958 return false;
959 if (argc <= 1) {
960 if (argc == 1 && !canConvert(srcTypes[0], dstTypes[0]))
961 return false;
962 return true;
963 }
964 if ((!oldForm.hasPrimitives() && oldForm.erasedType == this) ||
965 (!newForm.hasPrimitives() && newForm.erasedType == newType)) {
966 // Somewhat complicated test to avoid a loop of 2 or more trips.
967 // If either type has only Object parameters, we know we can convert.
968 assert(canConvertParameters(srcTypes, dstTypes));
969 return true;
970 }
971 return canConvertParameters(srcTypes, dstTypes);
972 }
973
974 /** Returns true if MHs.explicitCastArguments produces the same result as MH.asType.
975 * If the type conversion is impossible for either, the result should be false.
976 */
977 /*non-public*/
978 boolean explicitCastEquivalentToAsType(MethodType newType) {
979 if (this == newType) return true;
980 if (!explicitCastEquivalentToAsType(rtype, newType.rtype)) {
981 return false;
982 }
983 Class<?>[] srcTypes = newType.ptypes;
984 Class<?>[] dstTypes = ptypes;
985 if (dstTypes == srcTypes) {
986 return true;
987 }
988 assert(dstTypes.length == srcTypes.length);
989 for (int i = 0; i < dstTypes.length; i++) {
990 if (!explicitCastEquivalentToAsType(srcTypes[i], dstTypes[i])) {
991 return false;
992 }
993 }
994 return true;
995 }
996
997 /** Reports true if the src can be converted to the dst, by both asType and MHs.eCE,
998 * and with the same effect.
999 * MHs.eCA has the following "upgrades" to MH.asType:
1000 * 1. interfaces are unchecked (that is, treated as if aliased to Object)
1001 * Therefore, {@code Object->CharSequence} is possible in both cases but has different semantics
1002 * 2. the full matrix of primitive-to-primitive conversions is supported
1003 * Narrowing like {@code long->byte} and basic-typing like {@code boolean->int}
1004 * are not supported by asType, but anything supported by asType is equivalent
1005 * with MHs.eCE.
1006 * 3a. unboxing conversions can be followed by the full matrix of primitive conversions
1007 * 3b. unboxing of null is permitted (creates a zero primitive value)
1008 * Other than interfaces, reference-to-reference conversions are the same.
1009 * Boxing primitives to references is the same for both operators.
1010 */
1011 private static boolean explicitCastEquivalentToAsType(Class<?> src, Class<?> dst) {
1012 if (src == dst || dst == Object.class || dst == void.class) return true;
1013 if (src.isPrimitive()) {
1014 // Could be a prim/prim conversion, where casting is a strict superset.
1015 // Or a boxing conversion, which is always to an exact wrapper class.
1016 return canConvert(src, dst);
1017 } else if (dst.isPrimitive()) {
1018 // Unboxing behavior is different between MHs.eCA & MH.asType (see 3b).
1019 return false;
1020 } else {
1021 // R->R always works, but we have to avoid a check-cast to an interface.
1022 return !dst.isInterface() || dst.isAssignableFrom(src);
1023 }
1024 }
1025
1026 private boolean canConvertParameters(Class<?>[] srcTypes, Class<?>[] dstTypes) {
1027 for (int i = 0; i < srcTypes.length; i++) {
1028 if (!canConvert(srcTypes[i], dstTypes[i])) {
1029 return false;
1030 }
1031 }
1032 return true;
1033 }
1034
1035 /*non-public*/
1036 static boolean canConvert(Class<?> src, Class<?> dst) {
1037 // short-circuit a few cases:
1038 if (src == dst || src == Object.class || dst == Object.class) return true;
1039 // the remainder of this logic is documented in MethodHandle.asType
1040 if (src.isPrimitive()) {
1041 // can force void to an explicit null, a la reflect.Method.invoke
1042 // can also force void to a primitive zero, by analogy
1043 if (src == void.class) return true; //or !dst.isPrimitive()?
1044 Wrapper sw = Wrapper.forPrimitiveType(src);
1045 if (dst.isPrimitive()) {
1046 // P->P must widen
1047 return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw);
1048 } else {
1049 // P->R must box and widen
1050 return dst.isAssignableFrom(sw.wrapperType());
1051 }
1052 } else if (dst.isPrimitive()) {
1053 // any value can be dropped
1054 if (dst == void.class) return true;
1055 Wrapper dw = Wrapper.forPrimitiveType(dst);
1056 // R->P must be able to unbox (from a dynamically chosen type) and widen
1057 // For example:
1058 // Byte/Number/Comparable/Object -> dw:Byte -> byte.
1059 // Character/Comparable/Object -> dw:Character -> char
1060 // Boolean/Comparable/Object -> dw:Boolean -> boolean
1061 // This means that dw must be cast-compatible with src.
1062 if (src.isAssignableFrom(dw.wrapperType())) {
1063 return true;
1064 }
1065 // The above does not work if the source reference is strongly typed
1066 // to a wrapper whose primitive must be widened. For example:
1067 // Byte -> unbox:byte -> short/int/long/float/double
1068 // Character -> unbox:char -> int/long/float/double
1069 if (Wrapper.isWrapperType(src) &&
1070 dw.isConvertibleFrom(Wrapper.forWrapperType(src))) {
1071 // can unbox from src and then widen to dst
1072 return true;
1073 }
1074 // We have already covered cases which arise due to runtime unboxing
1075 // of a reference type which covers several wrapper types:
1076 // Object -> cast:Integer -> unbox:int -> long/float/double
1077 // Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double
1078 // An marginal case is Number -> dw:Character -> char, which would be OK if there were a
1079 // subclass of Number which wraps a value that can convert to char.
1080 // Since there is none, we don't need an extra check here to cover char or boolean.
1081 return false;
1082 } else {
1083 // R->R always works, since null is always valid dynamically
1084 return true;
1085 }
1086 }
1087
1088 /// Queries which have to do with the bytecode architecture
1089
1090 /** Reports the number of JVM stack slots required to invoke a method
1091 * of this type. Note that (for historical reasons) the JVM requires
1092 * a second stack slot to pass long and double arguments.
1093 * So this method returns {@link #parameterCount() parameterCount} plus the
1094 * number of long and double parameters (if any).
1095 * <p>
1096 * This method is included for the benefit of applications that must
1097 * generate bytecodes that process method handles and invokedynamic.
1098 * @return the number of JVM stack slots for this type's parameters
1099 */
1100 /*non-public*/
1101 int parameterSlotCount() {
1102 return form.parameterSlotCount();
1103 }
1104
1105 /*non-public*/
1106 Invokers invokers() {
1107 Invokers inv = invokers;
1108 if (inv != null) return inv;
1109 invokers = inv = new Invokers(this);
1110 return inv;
1111 }
1112
1113 /**
1114 * Finds or creates an instance of a method type, given the spelling of its bytecode descriptor.
1115 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
1116 * Any class or interface name embedded in the descriptor string will be
1117 * resolved by the given loader (or if it is null, on the system class loader).
1118 * <p>
1119 * Note that it is possible to encounter method types which cannot be
1120 * constructed by this method, because their component types are
1121 * not all reachable from a common class loader.
1122 * <p>
1123 * This method is included for the benefit of applications that must
1124 * generate bytecodes that process method handles and {@code invokedynamic}.
1125 * @param descriptor a bytecode-level type descriptor string "(T...)T"
1126 * @param loader the class loader in which to look up the types
1127 * @return a method type matching the bytecode-level type descriptor
1128 * @throws NullPointerException if the string is null
1129 * @throws IllegalArgumentException if the string is not well-formed
1130 * @throws TypeNotPresentException if a named type cannot be found
1131 * @throws SecurityException if the security manager is present and
1132 * {@code loader} is {@code null} and the caller does not have the
1133 * {@link RuntimePermission}{@code ("getClassLoader")}
1134 */
1135 public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader)
1136 throws IllegalArgumentException, TypeNotPresentException
1137 {
1138 if (loader == null) {
1139 SecurityManager sm = System.getSecurityManager();
1140 if (sm != null) {
1141 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
1142 }
1143 }
1144 return fromDescriptor(descriptor,
1145 (loader == null) ? ClassLoader.getSystemClassLoader() : loader);
1146 }
1147
1148 /**
1149 * Same as {@link #fromMethodDescriptorString(String, ClassLoader)}, but
1150 * {@code null} ClassLoader means the bootstrap loader is used here.
1151 * <p>
1152 * IMPORTANT: This method is preferable for JDK internal use as it more
1153 * correctly interprets {@code null} ClassLoader than
1154 * {@link #fromMethodDescriptorString(String, ClassLoader)}.
1155 * Use of this method also avoids early initialization issues when system
1156 * ClassLoader is not initialized yet.
1157 */
1158 static MethodType fromDescriptor(String descriptor, ClassLoader loader)
1159 throws IllegalArgumentException, TypeNotPresentException
1160 {
1161 if (!descriptor.startsWith("(") || // also generates NPE if needed
1162 descriptor.indexOf(')') < 0 ||
1163 descriptor.indexOf('.') >= 0)
1164 throw newIllegalArgumentException("not a method descriptor: "+descriptor);
1165 List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader);
1166 Class<?> rtype = types.remove(types.size() - 1);
1167 Class<?>[] ptypes = listToArray(types);
1168 return makeImpl(rtype, ptypes, true);
1169 }
1170
1171 /**
1172 * Returns a descriptor string for the method type. This method
1173 * is equivalent to calling {@link #descriptorString() MethodType::descriptorString}.
1174 *
1175 * <p>
1176 * Note that this is not a strict inverse of {@link #fromMethodDescriptorString fromMethodDescriptorString}.
1177 * Two distinct classes which share a common name but have different class loaders
1178 * will appear identical when viewed within descriptor strings.
1179 * <p>
1180 * This method is included for the benefit of applications that must
1181 * generate bytecodes that process method handles and {@code invokedynamic}.
1182 * {@link #fromMethodDescriptorString(java.lang.String, java.lang.ClassLoader) fromMethodDescriptorString},
1183 * because the latter requires a suitable class loader argument.
1184 * @return the descriptor string for this method type
1185 * @jvms 4.3.3 Method Descriptors
1186 * @see <a href="#descriptor">Nominal Descriptor for {@code MethodType}</a>
1187 */
1188 public String toMethodDescriptorString() {
1189 String desc = methodDescriptor;
1190 if (desc == null) {
1191 desc = BytecodeDescriptor.unparseMethod(this.rtype, this.ptypes);
1192 methodDescriptor = desc;
1193 }
1194 return desc;
1195 }
1196
1197 /**
1198 * Returns a descriptor string for this method type.
1199 *
1200 * <p>
1201 * If this method type can be <a href="#descriptor">described nominally</a>,
1202 * then the result is a method type descriptor string (JVMS {@jvms 4.3.3}).
1203 * {@link MethodTypeDesc MethodTypeDesc} for this method type
1204 * can be produced by calling {@link MethodTypeDesc#ofDescriptor(String)
1205 * MethodTypeDesc::ofDescriptor} with the result descriptor string.
1206 * <p>
1207 * If this method type cannot be <a href="#descriptor">described nominally</a>
1208 * and the result is a string of the form:
1209 * <blockquote>{@code "(<parameter-descriptors>)<return-descriptor>"}</blockquote>
1210 * where {@code <parameter-descriptors>} is the concatenation of the
1211 * {@linkplain Class#descriptorString() descriptor string} of all
1212 * of the parameter types and the {@linkplain Class#descriptorString() descriptor string}
1213 * of the return type. No {@link java.lang.constant.MethodTypeDesc MethodTypeDesc}
1214 * can be produced from the result string.
1215 *
1216 * @return the descriptor string for this method type
1217 * @since 12
1218 * @jvms 4.3.3 Method Descriptors
1219 * @see <a href="#descriptor">Nominal Descriptor for {@code MethodType}</a>
1220 */
1221 @Override
1222 public String descriptorString() {
1223 return toMethodDescriptorString();
1224 }
1225
1226 /*non-public*/
1227 static String toFieldDescriptorString(Class<?> cls) {
1228 return BytecodeDescriptor.unparse(cls);
1229 }
1230
1231 /**
1232 * Returns a nominal descriptor for this instance, if one can be
1233 * constructed, or an empty {@link Optional} if one cannot be.
1234 *
1235 * @return An {@link Optional} containing the resulting nominal descriptor,
1236 * or an empty {@link Optional} if one cannot be constructed.
1237 * @since 12
1238 * @see <a href="#descriptor">Nominal Descriptor for {@code MethodType}</a>
1239 */
1240 @Override
1241 public Optional<MethodTypeDesc> describeConstable() {
1242 try {
1243 return Optional.of(MethodTypeDesc.of(returnType().describeConstable().orElseThrow(),
1244 Stream.of(parameterArray())
1245 .map(p -> p.describeConstable().orElseThrow())
1246 .toArray(ClassDesc[]::new)));
1247 }
1248 catch (NoSuchElementException e) {
1249 return Optional.empty();
1250 }
1251 }
1252
1253 /// Serialization.
1254
1255 /**
1256 * There are no serializable fields for {@code MethodType}.
1257 */
1258 @java.io.Serial
1259 private static final java.io.ObjectStreamField[] serialPersistentFields = { };
1260
1261 /**
1262 * Save the {@code MethodType} instance to a stream.
1263 *
1264 * @serialData
1265 * For portability, the serialized format does not refer to named fields.
1266 * Instead, the return type and parameter type arrays are written directly
1267 * from the {@code writeObject} method, using two calls to {@code s.writeObject}
1268 * as follows:
1269 * <blockquote><pre>{@code
1270 s.writeObject(this.returnType());
1271 s.writeObject(this.parameterArray());
1272 * }</pre></blockquote>
1273 * <p>
1274 * The deserialized field values are checked as if they were
1275 * provided to the factory method {@link #methodType(Class,Class[]) methodType}.
1276 * For example, null values, or {@code void} parameter types,
1277 * will lead to exceptions during deserialization.
1278 * @param s the stream to write the object to
1279 * @throws java.io.IOException if there is a problem writing the object
1280 */
1281 @java.io.Serial
1282 private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
1283 s.defaultWriteObject(); // requires serialPersistentFields to be an empty array
1284 s.writeObject(returnType());
1285 s.writeObject(parameterArray());
1286 }
1287
1288 /**
1289 * Reconstitute the {@code MethodType} instance from a stream (that is,
1290 * deserialize it).
1291 * This instance is a scratch object with bogus final fields.
1292 * It provides the parameters to the factory method called by
1293 * {@link #readResolve readResolve}.
1294 * After that call it is discarded.
1295 * @param s the stream to read the object from
1296 * @throws java.io.IOException if there is a problem reading the object
1297 * @throws ClassNotFoundException if one of the component classes cannot be resolved
1298 * @see #readResolve
1299 * @see #writeObject
1300 */
1301 @java.io.Serial
1302 private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
1303 // Assign temporary defaults in case this object escapes
1304 MethodType_init(void.class, NO_PTYPES);
1305
1306 s.defaultReadObject(); // requires serialPersistentFields to be an empty array
1307
1308 Class<?> returnType = (Class<?>) s.readObject();
1309 Class<?>[] parameterArray = (Class<?>[]) s.readObject();
1310 parameterArray = parameterArray.clone(); // make sure it is unshared
1311
1312 // Assign deserialized values
1313 MethodType_init(returnType, parameterArray);
1314 }
1315
1316 // Initialization of state for deserialization only
1317 private void MethodType_init(Class<?> rtype, Class<?>[] ptypes) {
1318 // In order to communicate these values to readResolve, we must
1319 // store them into the implementation-specific final fields.
1320 checkRtype(rtype);
1321 checkPtypes(ptypes);
1322 UNSAFE.putReference(this, OffsetHolder.rtypeOffset, rtype);
1323 UNSAFE.putReference(this, OffsetHolder.ptypesOffset, ptypes);
1324 }
1325
1326 // Support for resetting final fields while deserializing. Implement Holder
1327 // pattern to make the rarely needed offset calculation lazy.
1328 private static class OffsetHolder {
1329 static final long rtypeOffset
1330 = UNSAFE.objectFieldOffset(MethodType.class, "rtype");
1331
1332 static final long ptypesOffset
1333 = UNSAFE.objectFieldOffset(MethodType.class, "ptypes");
1334 }
1335
1336 /**
1337 * Resolves and initializes a {@code MethodType} object
1338 * after serialization.
1339 * @return the fully initialized {@code MethodType} object
1340 */
1341 @java.io.Serial
1342 private Object readResolve() {
1343 // Do not use a trusted path for deserialization:
1344 // return makeImpl(rtype, ptypes, true);
1345 // Verify all operands, and make sure ptypes is unshared:
1346 try {
1347 return methodType(rtype, ptypes);
1348 } finally {
1349 // Re-assign defaults in case this object escapes
1350 MethodType_init(void.class, NO_PTYPES);
1351 }
1352 }
1353
1354 /**
1355 * Simple implementation of weak concurrent intern set.
1356 *
1357 * @param <T> interned type
1358 */
1359 private static class ConcurrentWeakInternSet<T> {
1360
1361 private final ConcurrentMap<WeakEntry<T>, WeakEntry<T>> map;
1362 private final ReferenceQueue<T> stale;
1363
1364 public ConcurrentWeakInternSet() {
1365 this.map = new ConcurrentHashMap<>(512);
1366 this.stale = new ReferenceQueue<>();
1367 }
1368
1369 /**
1370 * Get the existing interned element.
1371 * This method returns null if no element is interned.
1372 *
1373 * @param elem element to look up
1374 * @return the interned element
1375 */
1376 public T get(T elem) {
1377 if (elem == null) throw new NullPointerException();
1378 expungeStaleElements();
1379
1380 WeakEntry<T> value = map.get(elem);
1381 if (value != null) {
1382 T res = value.get();
1383 if (res != null) {
1384 return res;
1385 }
1386 }
1387 return null;
1388 }
1389
1390 /**
1391 * Interns the element.
1392 * Always returns non-null element, matching the one in the intern set.
1393 * Under the race against another add(), it can return <i>different</i>
1394 * element, if another thread beats us to interning it.
1395 *
1396 * @param elem element to add
1397 * @return element that was actually added
1398 */
1399 public T add(T elem) {
1400 if (elem == null) throw new NullPointerException();
1401
1402 // Playing double race here, and so spinloop is required.
1403 // First race is with two concurrent updaters.
1404 // Second race is with GC purging weak ref under our feet.
1405 // Hopefully, we almost always end up with a single pass.
1406 T interned;
1407 WeakEntry<T> e = new WeakEntry<>(elem, stale);
1408 do {
1409 expungeStaleElements();
1410 WeakEntry<T> exist = map.putIfAbsent(e, e);
1411 interned = (exist == null) ? elem : exist.get();
1412 } while (interned == null);
1413 return interned;
1414 }
1415
1416 private void expungeStaleElements() {
1417 Reference<? extends T> reference;
1418 while ((reference = stale.poll()) != null) {
1419 map.remove(reference);
1420 }
1421 }
1422
1423 private static class WeakEntry<T> extends WeakReference<T> {
1424
1425 public final int hashcode;
1426
1427 public WeakEntry(T key, ReferenceQueue<T> queue) {
1428 super(key, queue);
1429 hashcode = key.hashCode();
1430 }
1431
1432 /**
1433 * This implementation returns {@code true} if {@code obj} is another
1434 * {@code WeakEntry} whose referent is equal to this referent, or
1435 * if {@code obj} is equal to the referent of this. This allows
1436 * lookups to be made without wrapping in a {@code WeakEntry}.
1437 *
1438 * @param obj the object to compare
1439 * @return true if {@code obj} is equal to this or the referent of this
1440 * @see MethodType#equals(Object)
1441 * @see Object#equals(Object)
1442 */
1443 @Override
1444 public boolean equals(Object obj) {
1445 Object mine = get();
1446 if (obj instanceof WeakEntry) {
1447 Object that = ((WeakEntry) obj).get();
1448 return (that == null || mine == null) ? (this == obj) : mine.equals(that);
1449 }
1450 return (mine == null) ? (obj == null) : mine.equals(obj);
1451 }
1452
1453 @Override
1454 public int hashCode() {
1455 return hashcode;
1456 }
1457
1458 }
1459 }
1460
1461 }