1 /*
2 * Copyright (c) 2008, 2018, 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
50 import static java.lang.invoke.MethodHandleStatics.UNSAFE;
51 import static java.lang.invoke.MethodHandleStatics.newIllegalArgumentException;
52
53 /**
54 * A method type represents the arguments and return type accepted and
55 * returned by a method handle, or the arguments and return type passed
56 * and expected by a method handle caller. Method types must be properly
57 * matched between a method handle and all its callers,
58 * and the JVM's operations enforce this matching at, specifically
59 * during calls to {@link MethodHandle#invokeExact MethodHandle.invokeExact}
60 * and {@link MethodHandle#invoke MethodHandle.invoke}, and during execution
61 * of {@code invokedynamic} instructions.
62 * <p>
63 * The structure is a return type accompanied by any number of parameter types.
64 * The types (primitive, {@code void}, and reference) are represented by {@link Class} objects.
65 * (For ease of exposition, we treat {@code void} as if it were a type.
66 * In fact, it denotes the absence of a return type.)
67 * <p>
68 * All instances of {@code MethodType} are immutable.
69 * Two instances are completely interchangeable if they compare equal.
70 * Equality depends on pairwise correspondence of the return and parameter types and on nothing else.
71 * <p>
72 * This type can be created only by factory methods.
73 * All factory methods may cache values, though caching is not guaranteed.
74 * Some factory methods are static, while others are virtual methods which
75 * modify precursor method types, e.g., by changing a selected parameter.
76 * <p>
77 * Factory methods which operate on groups of parameter types
78 * are systematically presented in two versions, so that both Java arrays and
79 * Java lists can be used to work with groups of parameter types.
80 * The query methods {@code parameterArray} and {@code parameterList}
81 * also provide a choice between arrays and lists.
82 * <p>
83 * {@code MethodType} objects are sometimes derived from bytecode instructions
84 * such as {@code invokedynamic}, specifically from the type descriptor strings associated
85 * with the instructions in a class file's constant pool.
86 * <p>
87 * Like classes and strings, method types can also be represented directly
88 * in a class file's constant pool as constants.
89 * A method type may be loaded by an {@code ldc} instruction which refers
90 * to a suitable {@code CONSTANT_MethodType} constant pool entry.
91 * The entry refers to a {@code CONSTANT_Utf8} spelling for the descriptor string.
92 * (For full details on method type constants,
93 * see sections 4.4.8 and 5.4.3.5 of the Java Virtual Machine Specification.)
94 * <p>
95 * When the JVM materializes a {@code MethodType} from a descriptor string,
96 * all classes named in the descriptor must be accessible, and will be loaded.
97 * (But the classes need not be initialized, as is the case with a {@code CONSTANT_Class}.)
98 * This loading may occur at any time before the {@code MethodType} object is first derived.
99 * @author John Rose, JSR 292 EG
100 * @since 1.7
101 */
102 public final
103 class MethodType
104 implements Constable,
105 TypeDescriptor.OfMethod<Class<?>, MethodType>,
106 java.io.Serializable {
107 @java.io.Serial
108 private static final long serialVersionUID = 292L; // {rtype, {ptype...}}
109
110 // The rtype and ptypes fields define the structural identity of the method type:
111 private final @Stable Class<?> rtype;
112 private final @Stable Class<?>[] ptypes;
113
114 // The remaining fields are caches of various sorts:
115 private @Stable MethodTypeForm form; // erased form, plus cached data about primitives
116 private @Stable MethodType wrapAlt; // alternative wrapped/unwrapped version
117 private @Stable Invokers invokers; // cache of handy higher-order adapters
118 private @Stable String methodDescriptor; // cache for toMethodDescriptorString
119
120 /**
121 * Constructor that performs no copying or validation.
122 * Should only be called from the factory method makeImpl
123 */
124 private MethodType(Class<?> rtype, Class<?>[] ptypes) {
125 this.rtype = rtype;
126 this.ptypes = ptypes;
127 }
128
129 /*trusted*/ MethodTypeForm form() { return form; }
130 /*trusted*/ Class<?> rtype() { return rtype; }
131 /*trusted*/ Class<?>[] ptypes() { return ptypes; }
132
133 void setForm(MethodTypeForm f) { form = f; }
134
135 /** This number, mandated by the JVM spec as 255,
136 * is the maximum number of <em>slots</em>
137 * that any Java method can receive in its argument list.
138 * It limits both JVM signatures and method type objects.
139 * The longest possible invocation will look like
140 * {@code staticMethod(arg1, arg2, ..., arg255)} or
141 * {@code x.virtualMethod(arg1, arg2, ..., arg254)}.
142 */
143 /*non-public*/ static final int MAX_JVM_ARITY = 255; // this is mandated by the JVM spec.
144
145 /** This number is the maximum arity of a method handle, 254.
146 * It is derived from the absolute JVM-imposed arity by subtracting one,
147 * which is the slot occupied by the method handle itself at the
148 * beginning of the argument list used to invoke the method handle.
149 * The longest possible invocation will look like
150 * {@code mh.invoke(arg1, arg2, ..., arg254)}.
151 */
152 // Issue: Should we allow MH.invokeWithArguments to go to the full 255?
153 /*non-public*/ static final int MAX_MH_ARITY = MAX_JVM_ARITY-1; // deduct one for mh receiver
154
155 /** This number is the maximum arity of a method handle invoker, 253.
156 * It is derived from the absolute JVM-imposed arity by subtracting two,
157 * which are the slots occupied by invoke method handle, and the
158 * target method handle, which are both at the beginning of the argument
159 * list used to invoke the target method handle.
160 * The longest possible invocation will look like
161 * {@code invokermh.invoke(targetmh, arg1, arg2, ..., arg253)}.
162 */
163 /*non-public*/ static final int MAX_MH_INVOKER_ARITY = MAX_MH_ARITY-1; // deduct one more for invoker
164
165 private static void checkRtype(Class<?> rtype) {
166 Objects.requireNonNull(rtype);
167 }
168 private static void checkPtype(Class<?> ptype) {
169 Objects.requireNonNull(ptype);
170 if (ptype == void.class)
171 throw newIllegalArgumentException("parameter type cannot be void");
172 }
173 /** Return number of extra slots (count of long/double args). */
174 private static int checkPtypes(Class<?>[] ptypes) {
175 int slots = 0;
176 for (Class<?> ptype : ptypes) {
177 checkPtype(ptype);
178 if (ptype == double.class || ptype == long.class) {
179 slots++;
180 }
181 }
182 checkSlotCount(ptypes.length + slots);
183 return slots;
184 }
185
186 static {
187 // MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work:
188 assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0);
189 }
190 static void checkSlotCount(int count) {
191 if ((count & MAX_JVM_ARITY) != count)
192 throw newIllegalArgumentException("bad parameter count "+count);
193 }
194 private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) {
195 if (num instanceof Integer) num = "bad index: "+num;
196 return new IndexOutOfBoundsException(num.toString());
197 }
198
199 static final ConcurrentWeakInternSet<MethodType> internTable = new ConcurrentWeakInternSet<>();
200
201 static final Class<?>[] NO_PTYPES = {};
202
203 /**
204 * Finds or creates an instance of the given method type.
205 * @param rtype the return type
206 * @param ptypes the parameter types
207 * @return a method type with the given components
208 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
209 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
210 */
211 public static
212 MethodType methodType(Class<?> rtype, Class<?>[] ptypes) {
213 return makeImpl(rtype, ptypes, false);
214 }
215
216 /**
217 * Finds or creates a method type with the given components.
218 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
219 * @param rtype the return type
220 * @param ptypes the parameter types
221 * @return a method type with the given components
222 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
223 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
224 */
225 public static
226 MethodType methodType(Class<?> rtype, List<Class<?>> ptypes) {
227 boolean notrust = false; // random List impl. could return evil ptypes array
228 return makeImpl(rtype, listToArray(ptypes), notrust);
229 }
230
231 private static Class<?>[] listToArray(List<Class<?>> ptypes) {
232 // sanity check the size before the toArray call, since size might be huge
233 checkSlotCount(ptypes.size());
234 return ptypes.toArray(NO_PTYPES);
235 }
236
237 /**
238 * Finds or creates a method type with the given components.
239 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
240 * The leading parameter type is prepended to the remaining array.
241 * @param rtype the return type
242 * @param ptype0 the first parameter type
243 * @param ptypes the remaining parameter types
244 * @return a method type with the given components
245 * @throws NullPointerException if {@code rtype} or {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is null
246 * @throws IllegalArgumentException if {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is {@code void.class}
247 */
248 public static
249 MethodType methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes) {
250 Class<?>[] ptypes1 = new Class<?>[1+ptypes.length];
251 ptypes1[0] = ptype0;
252 System.arraycopy(ptypes, 0, ptypes1, 1, ptypes.length);
253 return makeImpl(rtype, ptypes1, true);
254 }
255
256 /**
257 * Finds or creates a method type with the given components.
258 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
259 * The resulting method has no parameter types.
260 * @param rtype the return type
261 * @return a method type with the given return value
262 * @throws NullPointerException if {@code rtype} is null
263 */
264 public static
265 MethodType methodType(Class<?> rtype) {
266 return makeImpl(rtype, NO_PTYPES, true);
267 }
268
269 /**
270 * Finds or creates a method type with the given components.
271 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
272 * The resulting method has the single given parameter type.
273 * @param rtype the return type
274 * @param ptype0 the parameter type
275 * @return a method type with the given return value and parameter type
276 * @throws NullPointerException if {@code rtype} or {@code ptype0} is null
277 * @throws IllegalArgumentException if {@code ptype0} is {@code void.class}
278 */
279 public static
280 MethodType methodType(Class<?> rtype, Class<?> ptype0) {
281 return makeImpl(rtype, new Class<?>[]{ ptype0 }, true);
282 }
283
284 /**
285 * Finds or creates a method type with the given components.
286 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
287 * The resulting method has the same parameter types as {@code ptypes},
288 * and the specified return type.
289 * @param rtype the return type
290 * @param ptypes the method type which supplies the parameter types
291 * @return a method type with the given components
292 * @throws NullPointerException if {@code rtype} or {@code ptypes} is null
293 */
294 public static
295 MethodType methodType(Class<?> rtype, MethodType ptypes) {
296 return makeImpl(rtype, ptypes.ptypes, true);
297 }
298
299 /**
300 * Sole factory method to find or create an interned method type.
301 * @param rtype desired return type
302 * @param ptypes desired parameter types
303 * @param trusted whether the ptypes can be used without cloning
304 * @return the unique method type of the desired structure
305 */
306 /*trusted*/ static
307 MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {
308 if (ptypes.length == 0) {
309 ptypes = NO_PTYPES; trusted = true;
310 }
311 MethodType primordialMT = new MethodType(rtype, ptypes);
312 MethodType mt = internTable.get(primordialMT);
313 if (mt != null)
314 return mt;
315
316 // promote the object to the Real Thing, and reprobe
317 MethodType.checkRtype(rtype);
318 if (trusted) {
319 MethodType.checkPtypes(ptypes);
320 mt = primordialMT;
321 } else {
322 // Make defensive copy then validate
323 ptypes = Arrays.copyOf(ptypes, ptypes.length);
324 MethodType.checkPtypes(ptypes);
325 mt = new MethodType(rtype, ptypes);
326 }
327 mt.form = MethodTypeForm.findForm(mt);
328 return internTable.add(mt);
329 }
330 private static final @Stable MethodType[] objectOnlyTypes = new MethodType[20];
331
332 /**
333 * Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array.
334 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
335 * All parameters and the return type will be {@code Object},
336 * except the final array parameter if any, which will be {@code Object[]}.
337 * @param objectArgCount number of parameters (excluding the final array parameter if any)
338 * @param finalArray whether there will be a trailing array parameter, of type {@code Object[]}
339 * @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments
340 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true)
341 * @see #genericMethodType(int)
342 */
343 public static
344 MethodType genericMethodType(int objectArgCount, boolean finalArray) {
345 MethodType mt;
346 checkSlotCount(objectArgCount);
347 int ivarargs = (!finalArray ? 0 : 1);
348 int ootIndex = objectArgCount*2 + ivarargs;
349 if (ootIndex < objectOnlyTypes.length) {
350 mt = objectOnlyTypes[ootIndex];
351 if (mt != null) return mt;
352 }
353 Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs];
354 Arrays.fill(ptypes, Object.class);
355 if (ivarargs != 0) ptypes[objectArgCount] = Object[].class;
356 mt = makeImpl(Object.class, ptypes, true);
357 if (ootIndex < objectOnlyTypes.length) {
358 objectOnlyTypes[ootIndex] = mt; // cache it here also!
359 }
360 return mt;
361 }
362
363 /**
364 * Finds or creates a method type whose components are all {@code Object}.
365 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
366 * All parameters and the return type will be Object.
367 * @param objectArgCount number of parameters
368 * @return a generally applicable method type, for all calls of the given argument count
369 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255
370 * @see #genericMethodType(int, boolean)
371 */
372 public static
373 MethodType genericMethodType(int objectArgCount) {
374 return genericMethodType(objectArgCount, false);
375 }
376
377 /**
378 * Finds or creates a method type with a single different parameter type.
379 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
380 * @param num the index (zero-based) of the parameter type to change
381 * @param nptype a new parameter type to replace the old one with
382 * @return the same type, except with the selected parameter changed
383 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
384 * @throws IllegalArgumentException if {@code nptype} is {@code void.class}
385 * @throws NullPointerException if {@code nptype} is null
386 */
387 public MethodType changeParameterType(int num, Class<?> nptype) {
388 if (parameterType(num) == nptype) return this;
389 checkPtype(nptype);
390 Class<?>[] nptypes = ptypes.clone();
391 nptypes[num] = nptype;
392 return makeImpl(rtype, nptypes, true);
393 }
394
395 /**
396 * Finds or creates a method type with additional parameter types.
397 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
398 * @param num the position (zero-based) of the inserted parameter type(s)
399 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
400 * @return the same type, except with the selected parameter(s) inserted
401 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
402 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
403 * or if the resulting method type would have more than 255 parameter slots
404 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
405 */
406 public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) {
407 int len = ptypes.length;
408 if (num < 0 || num > len)
409 throw newIndexOutOfBoundsException(num);
410 int ins = checkPtypes(ptypesToInsert);
411 checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins);
412 int ilen = ptypesToInsert.length;
413 if (ilen == 0) return this;
414 Class<?>[] nptypes = new Class<?>[len + ilen];
415 if (num > 0) {
416 System.arraycopy(ptypes, 0, nptypes, 0, num);
417 }
418 System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen);
419 if (num < len) {
420 System.arraycopy(ptypes, num, nptypes, num+ilen, len-num);
421 }
422 return makeImpl(rtype, nptypes, true);
423 }
424
425 /**
426 * Finds or creates a method type with additional parameter types.
427 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
428 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
429 * @return the same type, except with the selected parameter(s) appended
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 appendParameterTypes(Class<?>... ptypesToInsert) {
435 return insertParameterTypes(parameterCount(), ptypesToInsert);
436 }
437
438 /**
439 * Finds or creates a method type with additional parameter types.
440 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
441 * @param num the position (zero-based) of the inserted parameter type(s)
442 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
443 * @return the same type, except with the selected parameter(s) inserted
444 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
445 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
446 * or if the resulting method type would have more than 255 parameter slots
447 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
448 */
449 public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) {
450 return insertParameterTypes(num, listToArray(ptypesToInsert));
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(List<Class<?>> ptypesToInsert) {
463 return insertParameterTypes(parameterCount(), ptypesToInsert);
464 }
465
466 /**
467 * Finds or creates a method type with modified parameter types.
468 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
469 * @param start the position (zero-based) of the first replaced parameter type(s)
470 * @param end the position (zero-based) after the last replaced parameter type(s)
471 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
472 * @return the same type, except with the selected parameter(s) replaced
473 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
474 * or if {@code end} is negative or greater than {@code parameterCount()}
475 * or if {@code start} is greater than {@code end}
476 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
477 * or if the resulting method type would have more than 255 parameter slots
478 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
479 */
480 /*non-public*/ MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) {
481 if (start == end)
482 return insertParameterTypes(start, ptypesToInsert);
483 int len = ptypes.length;
484 if (!(0 <= start && start <= end && end <= len))
485 throw newIndexOutOfBoundsException("start="+start+" end="+end);
486 int ilen = ptypesToInsert.length;
487 if (ilen == 0)
488 return dropParameterTypes(start, end);
489 return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert);
490 }
491
492 /** Replace the last arrayLength parameter types with the component type of arrayType.
493 * @param arrayType any array type
494 * @param pos position at which to spread
495 * @param arrayLength the number of parameter types to change
496 * @return the resulting type
497 */
498 /*non-public*/ MethodType asSpreaderType(Class<?> arrayType, int pos, int arrayLength) {
499 assert(parameterCount() >= arrayLength);
500 int spreadPos = pos;
501 if (arrayLength == 0) return this; // nothing to change
502 if (arrayType == Object[].class) {
503 if (isGeneric()) return this; // nothing to change
504 if (spreadPos == 0) {
505 // no leading arguments to preserve; go generic
506 MethodType res = genericMethodType(arrayLength);
507 if (rtype != Object.class) {
508 res = res.changeReturnType(rtype);
509 }
510 return res;
511 }
512 }
513 Class<?> elemType = arrayType.getComponentType();
514 assert(elemType != null);
515 for (int i = spreadPos; i < spreadPos + arrayLength; i++) {
516 if (ptypes[i] != elemType) {
517 Class<?>[] fixedPtypes = ptypes.clone();
518 Arrays.fill(fixedPtypes, i, spreadPos + arrayLength, elemType);
519 return methodType(rtype, fixedPtypes);
520 }
521 }
522 return this; // arguments check out; no change
523 }
524
525 /** Return the leading parameter type, which must exist and be a reference.
526 * @return the leading parameter type, after error checks
527 */
528 /*non-public*/ Class<?> leadingReferenceParameter() {
529 Class<?> ptype;
530 if (ptypes.length == 0 ||
531 (ptype = ptypes[0]).isPrimitive())
532 throw newIllegalArgumentException("no leading reference parameter");
533 return ptype;
534 }
535
536 /** Delete the last parameter type and replace it with arrayLength copies of the component type of arrayType.
537 * @param arrayType any array type
538 * @param pos position at which to insert parameters
539 * @param arrayLength the number of parameter types to insert
540 * @return the resulting type
541 */
542 /*non-public*/ MethodType asCollectorType(Class<?> arrayType, int pos, int arrayLength) {
543 assert(parameterCount() >= 1);
544 assert(pos < ptypes.length);
545 assert(ptypes[pos].isAssignableFrom(arrayType));
546 MethodType res;
547 if (arrayType == Object[].class) {
548 res = genericMethodType(arrayLength);
549 if (rtype != Object.class) {
550 res = res.changeReturnType(rtype);
551 }
552 } else {
553 Class<?> elemType = arrayType.getComponentType();
554 assert(elemType != null);
555 res = methodType(rtype, Collections.nCopies(arrayLength, elemType));
556 }
557 if (ptypes.length == 1) {
558 return res;
559 } else {
560 // insert after (if need be), then before
561 if (pos < ptypes.length - 1) {
562 res = res.insertParameterTypes(arrayLength, Arrays.copyOfRange(ptypes, pos + 1, ptypes.length));
563 }
564 return res.insertParameterTypes(0, Arrays.copyOf(ptypes, pos));
565 }
566 }
567
568 /**
569 * Finds or creates a method type with some parameter types omitted.
570 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
571 * @param start the index (zero-based) of the first parameter type to remove
572 * @param end the index (greater than {@code start}) of the first parameter type after not to remove
573 * @return the same type, except with the selected parameter(s) removed
574 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
575 * or if {@code end} is negative or greater than {@code parameterCount()}
576 * or if {@code start} is greater than {@code end}
577 */
578 public MethodType dropParameterTypes(int start, int end) {
579 int len = ptypes.length;
580 if (!(0 <= start && start <= end && end <= len))
581 throw newIndexOutOfBoundsException("start="+start+" end="+end);
582 if (start == end) return this;
583 Class<?>[] nptypes;
584 if (start == 0) {
585 if (end == len) {
586 // drop all parameters
587 nptypes = NO_PTYPES;
588 } else {
589 // drop initial parameter(s)
590 nptypes = Arrays.copyOfRange(ptypes, end, len);
591 }
592 } else {
593 if (end == len) {
594 // drop trailing parameter(s)
595 nptypes = Arrays.copyOfRange(ptypes, 0, start);
596 } else {
597 int tail = len - end;
598 nptypes = Arrays.copyOfRange(ptypes, 0, start + tail);
599 System.arraycopy(ptypes, end, nptypes, start, tail);
600 }
601 }
602 return makeImpl(rtype, nptypes, true);
603 }
604
605 /**
606 * Finds or creates a method type with a different return type.
607 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
608 * @param nrtype a return parameter type to replace the old one with
609 * @return the same type, except with the return type change
610 * @throws NullPointerException if {@code nrtype} is null
611 */
612 public MethodType changeReturnType(Class<?> nrtype) {
613 if (returnType() == nrtype) return this;
614 return makeImpl(nrtype, ptypes, true);
615 }
616
617 /**
618 * Reports if this type contains a primitive argument or return value.
619 * The return type {@code void} counts as a primitive.
620 * @return true if any of the types are primitives
621 */
622 public boolean hasPrimitives() {
623 return form.hasPrimitives();
624 }
625
626 /**
627 * Reports if this type contains a wrapper argument or return value.
628 * Wrappers are types which box primitive values, such as {@link Integer}.
629 * The reference type {@code java.lang.Void} counts as a wrapper,
630 * if it occurs as a return type.
631 * @return true if any of the types are wrappers
632 */
633 public boolean hasWrappers() {
634 return unwrap() != this;
635 }
636
637 /**
638 * Erases all reference types to {@code Object}.
639 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
640 * All primitive types (including {@code void}) will remain unchanged.
641 * @return a version of the original type with all reference types replaced
642 */
643 public MethodType erase() {
644 return form.erasedType();
645 }
646
647 /**
648 * Erases all reference types to {@code Object}, and all subword types to {@code int}.
649 * This is the reduced type polymorphism used by private methods
650 * such as {@link MethodHandle#invokeBasic invokeBasic}.
651 * @return a version of the original type with all reference and subword types replaced
652 */
653 /*non-public*/ MethodType basicType() {
654 return form.basicType();
655 }
656
657 private static final @Stable Class<?>[] METHOD_HANDLE_ARRAY
658 = new Class<?>[] { MethodHandle.class };
659
660 /**
661 * @return a version of the original type with MethodHandle prepended as the first argument
662 */
663 /*non-public*/ MethodType invokerType() {
664 return insertParameterTypes(0, METHOD_HANDLE_ARRAY);
665 }
666
667 /**
668 * Converts all types, both reference and primitive, to {@code Object}.
669 * Convenience method for {@link #genericMethodType(int) genericMethodType}.
670 * The expression {@code type.wrap().erase()} produces the same value
671 * as {@code type.generic()}.
672 * @return a version of the original type with all types replaced
673 */
674 public MethodType generic() {
675 return genericMethodType(parameterCount());
676 }
677
678 /*non-public*/ boolean isGeneric() {
679 return this == erase() && !hasPrimitives();
680 }
681
682 /**
683 * Converts all primitive types to their corresponding wrapper types.
684 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
685 * All reference types (including wrapper types) will remain unchanged.
686 * A {@code void} return type is changed to the type {@code java.lang.Void}.
687 * The expression {@code type.wrap().erase()} produces the same value
688 * as {@code type.generic()}.
689 * @return a version of the original type with all primitive types replaced
690 */
691 public MethodType wrap() {
692 return hasPrimitives() ? wrapWithPrims(this) : this;
693 }
694
695 /**
696 * Converts all wrapper types to their corresponding primitive types.
697 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
698 * All primitive types (including {@code void}) will remain unchanged.
699 * A return type of {@code java.lang.Void} is changed to {@code void}.
700 * @return a version of the original type with all wrapper types replaced
701 */
702 public MethodType unwrap() {
703 MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this);
704 return unwrapWithNoPrims(noprims);
705 }
706
707 private static MethodType wrapWithPrims(MethodType pt) {
708 assert(pt.hasPrimitives());
709 MethodType wt = pt.wrapAlt;
710 if (wt == null) {
711 // fill in lazily
712 wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP, MethodTypeForm.WRAP);
713 assert(wt != null);
714 pt.wrapAlt = wt;
715 }
716 return wt;
717 }
718
719 private static MethodType unwrapWithNoPrims(MethodType wt) {
720 assert(!wt.hasPrimitives());
721 MethodType uwt = wt.wrapAlt;
722 if (uwt == null) {
723 // fill in lazily
724 uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP, MethodTypeForm.UNWRAP);
725 if (uwt == null)
726 uwt = wt; // type has no wrappers or prims at all
727 wt.wrapAlt = uwt;
728 }
729 return uwt;
730 }
731
732 /**
733 * Returns the parameter type at the specified index, within this method type.
734 * @param num the index (zero-based) of the desired parameter type
735 * @return the selected parameter type
736 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
737 */
738 public Class<?> parameterType(int num) {
739 return ptypes[num];
740 }
741 /**
742 * Returns the number of parameter types in this method type.
743 * @return the number of parameter types
744 */
745 public int parameterCount() {
746 return ptypes.length;
747 }
748 /**
749 * Returns the return type of this method type.
750 * @return the return type
751 */
752 public Class<?> returnType() {
753 return rtype;
754 }
755
756 /**
757 * Presents the parameter types as a list (a convenience method).
758 * The list will be immutable.
759 * @return the parameter types (as an immutable list)
760 */
761 public List<Class<?>> parameterList() {
762 return Collections.unmodifiableList(Arrays.asList(ptypes.clone()));
763 }
764
765 /**
766 * Returns the last parameter type of this method type.
767 * If this type has no parameters, the sentinel value
768 * {@code void.class} is returned instead.
769 * @apiNote
770 * <p>
771 * The sentinel value is chosen so that reflective queries can be
772 * made directly against the result value.
773 * The sentinel value cannot be confused with a real parameter,
774 * since {@code void} is never acceptable as a parameter type.
775 * For variable arity invocation modes, the expression
776 * {@link Class#getComponentType lastParameterType().getComponentType()}
777 * is useful to query the type of the "varargs" parameter.
778 * @return the last parameter type if any, else {@code void.class}
779 * @since 10
780 */
781 public Class<?> lastParameterType() {
782 int len = ptypes.length;
783 return len == 0 ? void.class : ptypes[len-1];
784 }
785
786 /**
787 * Presents the parameter types as an array (a convenience method).
788 * Changes to the array will not result in changes to the type.
789 * @return the parameter types (as a fresh copy if necessary)
790 */
791 public Class<?>[] parameterArray() {
792 return ptypes.clone();
793 }
794
795 /**
796 * Compares the specified object with this type for equality.
797 * That is, it returns {@code true} if and only if the specified object
798 * is also a method type with exactly the same parameters and return type.
799 * @param x object to compare
800 * @see Object#equals(Object)
801 */
802 // This implementation may also return true if x is a WeakEntry containing
803 // a method type that is equal to this. This is an internal implementation
804 // detail to allow for faster method type lookups.
805 // See ConcurrentWeakInternSet.WeakEntry#equals(Object)
806 @Override
807 public boolean equals(Object x) {
808 if (this == x) {
809 return true;
810 }
811 if (x instanceof MethodType) {
812 return equals((MethodType)x);
813 }
814 if (x instanceof ConcurrentWeakInternSet.WeakEntry) {
815 Object o = ((ConcurrentWeakInternSet.WeakEntry)x).get();
816 if (o instanceof MethodType) {
817 return equals((MethodType)o);
818 }
819 }
820 return false;
821 }
822
823 private boolean equals(MethodType that) {
824 return this.rtype == that.rtype
825 && Arrays.equals(this.ptypes, that.ptypes);
826 }
827
828 /**
829 * Returns the hash code value for this method type.
830 * It is defined to be the same as the hashcode of a List
831 * whose elements are the return type followed by the
832 * parameter types.
833 * @return the hash code value for this method type
834 * @see Object#hashCode()
835 * @see #equals(Object)
836 * @see List#hashCode()
837 */
838 @Override
839 public int hashCode() {
840 int hashCode = 31 + rtype.hashCode();
841 for (Class<?> ptype : ptypes)
842 hashCode = 31 * hashCode + ptype.hashCode();
843 return hashCode;
844 }
845
846 /**
847 * Returns a string representation of the method type,
848 * of the form {@code "(PT0,PT1...)RT"}.
849 * The string representation of a method type is a
850 * parenthesis enclosed, comma separated list of type names,
851 * followed immediately by the return type.
852 * <p>
853 * Each type is represented by its
854 * {@link java.lang.Class#getSimpleName simple name}.
855 */
856 @Override
857 public String toString() {
858 StringJoiner sj = new StringJoiner(",", "(",
859 ")" + rtype.getSimpleName());
860 for (int i = 0; i < ptypes.length; i++) {
861 sj.add(ptypes[i].getSimpleName());
862 }
863 return sj.toString();
864 }
865
866 /** True if my parameter list is effectively identical to the given full list,
867 * after skipping the given number of my own initial parameters.
868 * In other words, after disregarding {@code skipPos} parameters,
869 * my remaining parameter list is no longer than the {@code fullList}, and
870 * is equal to the same-length initial sublist of {@code fullList}.
871 */
872 /*non-public*/
873 boolean effectivelyIdenticalParameters(int skipPos, List<Class<?>> fullList) {
874 int myLen = ptypes.length, fullLen = fullList.size();
875 if (skipPos > myLen || myLen - skipPos > fullLen)
876 return false;
877 List<Class<?>> myList = Arrays.asList(ptypes);
878 if (skipPos != 0) {
879 myList = myList.subList(skipPos, myLen);
880 myLen -= skipPos;
881 }
882 if (fullLen == myLen)
883 return myList.equals(fullList);
884 else
885 return myList.equals(fullList.subList(0, myLen));
886 }
887
888 /** True if the old return type can always be viewed (w/o casting) under new return type,
889 * and the new parameters can be viewed (w/o casting) under the old parameter types.
890 */
891 /*non-public*/
892 boolean isViewableAs(MethodType newType, boolean keepInterfaces) {
893 if (!VerifyType.isNullConversion(returnType(), newType.returnType(), keepInterfaces))
894 return false;
895 if (form == newType.form && form.erasedType == this)
896 return true; // my reference parameters are all Object
897 if (ptypes == newType.ptypes)
898 return true;
899 int argc = parameterCount();
900 if (argc != newType.parameterCount())
901 return false;
902 for (int i = 0; i < argc; i++) {
903 if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i), keepInterfaces))
904 return false;
905 }
906 return true;
907 }
908 /*non-public*/
909 boolean isConvertibleTo(MethodType newType) {
910 MethodTypeForm oldForm = this.form();
911 MethodTypeForm newForm = newType.form();
912 if (oldForm == newForm)
913 // same parameter count, same primitive/object mix
914 return true;
915 if (!canConvert(returnType(), newType.returnType()))
916 return false;
917 Class<?>[] srcTypes = newType.ptypes;
918 Class<?>[] dstTypes = ptypes;
919 if (srcTypes == dstTypes)
920 return true;
921 int argc;
922 if ((argc = srcTypes.length) != dstTypes.length)
923 return false;
924 if (argc <= 1) {
925 if (argc == 1 && !canConvert(srcTypes[0], dstTypes[0]))
926 return false;
927 return true;
928 }
929 if ((oldForm.primitiveParameterCount() == 0 && oldForm.erasedType == this) ||
930 (newForm.primitiveParameterCount() == 0 && newForm.erasedType == newType)) {
931 // Somewhat complicated test to avoid a loop of 2 or more trips.
932 // If either type has only Object parameters, we know we can convert.
933 assert(canConvertParameters(srcTypes, dstTypes));
934 return true;
935 }
936 return canConvertParameters(srcTypes, dstTypes);
937 }
938
939 /** Returns true if MHs.explicitCastArguments produces the same result as MH.asType.
940 * If the type conversion is impossible for either, the result should be false.
941 */
942 /*non-public*/
943 boolean explicitCastEquivalentToAsType(MethodType newType) {
944 if (this == newType) return true;
945 if (!explicitCastEquivalentToAsType(rtype, newType.rtype)) {
946 return false;
947 }
948 Class<?>[] srcTypes = newType.ptypes;
949 Class<?>[] dstTypes = ptypes;
950 if (dstTypes == srcTypes) {
951 return true;
952 }
953 assert(dstTypes.length == srcTypes.length);
954 for (int i = 0; i < dstTypes.length; i++) {
955 if (!explicitCastEquivalentToAsType(srcTypes[i], dstTypes[i])) {
956 return false;
957 }
958 }
959 return true;
960 }
961
962 /** Reports true if the src can be converted to the dst, by both asType and MHs.eCE,
963 * and with the same effect.
964 * MHs.eCA has the following "upgrades" to MH.asType:
965 * 1. interfaces are unchecked (that is, treated as if aliased to Object)
966 * Therefore, {@code Object->CharSequence} is possible in both cases but has different semantics
967 * 2. the full matrix of primitive-to-primitive conversions is supported
968 * Narrowing like {@code long->byte} and basic-typing like {@code boolean->int}
969 * are not supported by asType, but anything supported by asType is equivalent
970 * with MHs.eCE.
971 * 3a. unboxing conversions can be followed by the full matrix of primitive conversions
972 * 3b. unboxing of null is permitted (creates a zero primitive value)
973 * Other than interfaces, reference-to-reference conversions are the same.
974 * Boxing primitives to references is the same for both operators.
975 */
976 private static boolean explicitCastEquivalentToAsType(Class<?> src, Class<?> dst) {
977 if (src == dst || dst == Object.class || dst == void.class) return true;
978 if (src.isPrimitive()) {
979 // Could be a prim/prim conversion, where casting is a strict superset.
980 // Or a boxing conversion, which is always to an exact wrapper class.
981 return canConvert(src, dst);
982 } else if (dst.isPrimitive()) {
983 // Unboxing behavior is different between MHs.eCA & MH.asType (see 3b).
984 return false;
985 } else {
986 // R->R always works, but we have to avoid a check-cast to an interface.
987 return !dst.isInterface() || dst.isAssignableFrom(src);
988 }
989 }
990
991 private boolean canConvertParameters(Class<?>[] srcTypes, Class<?>[] dstTypes) {
992 for (int i = 0; i < srcTypes.length; i++) {
993 if (!canConvert(srcTypes[i], dstTypes[i])) {
994 return false;
995 }
996 }
997 return true;
998 }
999
1000 /*non-public*/
1001 static boolean canConvert(Class<?> src, Class<?> dst) {
1002 // short-circuit a few cases:
1003 if (src == dst || src == Object.class || dst == Object.class) return true;
1004 // the remainder of this logic is documented in MethodHandle.asType
1005 if (src.isPrimitive()) {
1006 // can force void to an explicit null, a la reflect.Method.invoke
1007 // can also force void to a primitive zero, by analogy
1008 if (src == void.class) return true; //or !dst.isPrimitive()?
1009 Wrapper sw = Wrapper.forPrimitiveType(src);
1010 if (dst.isPrimitive()) {
1011 // P->P must widen
1012 return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw);
1013 } else {
1014 // P->R must box and widen
1015 return dst.isAssignableFrom(sw.wrapperType());
1016 }
1017 } else if (dst.isPrimitive()) {
1018 // any value can be dropped
1019 if (dst == void.class) return true;
1020 Wrapper dw = Wrapper.forPrimitiveType(dst);
1021 // R->P must be able to unbox (from a dynamically chosen type) and widen
1022 // For example:
1023 // Byte/Number/Comparable/Object -> dw:Byte -> byte.
1024 // Character/Comparable/Object -> dw:Character -> char
1025 // Boolean/Comparable/Object -> dw:Boolean -> boolean
1026 // This means that dw must be cast-compatible with src.
1027 if (src.isAssignableFrom(dw.wrapperType())) {
1028 return true;
1029 }
1030 // The above does not work if the source reference is strongly typed
1031 // to a wrapper whose primitive must be widened. For example:
1032 // Byte -> unbox:byte -> short/int/long/float/double
1033 // Character -> unbox:char -> int/long/float/double
1034 if (Wrapper.isWrapperType(src) &&
1035 dw.isConvertibleFrom(Wrapper.forWrapperType(src))) {
1036 // can unbox from src and then widen to dst
1037 return true;
1038 }
1039 // We have already covered cases which arise due to runtime unboxing
1040 // of a reference type which covers several wrapper types:
1041 // Object -> cast:Integer -> unbox:int -> long/float/double
1042 // Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double
1043 // An marginal case is Number -> dw:Character -> char, which would be OK if there were a
1044 // subclass of Number which wraps a value that can convert to char.
1045 // Since there is none, we don't need an extra check here to cover char or boolean.
1046 return false;
1047 } else {
1048 // R->R always works, since null is always valid dynamically
1049 return true;
1050 }
1051 }
1052
1053 /// Queries which have to do with the bytecode architecture
1054
1055 /** Reports the number of JVM stack slots required to invoke a method
1056 * of this type. Note that (for historical reasons) the JVM requires
1057 * a second stack slot to pass long and double arguments.
1058 * So this method returns {@link #parameterCount() parameterCount} plus the
1059 * number of long and double parameters (if any).
1060 * <p>
1061 * This method is included for the benefit of applications that must
1062 * generate bytecodes that process method handles and invokedynamic.
1063 * @return the number of JVM stack slots for this type's parameters
1064 */
1065 /*non-public*/ int parameterSlotCount() {
1066 return form.parameterSlotCount();
1067 }
1068
1069 /*non-public*/ Invokers invokers() {
1070 Invokers inv = invokers;
1071 if (inv != null) return inv;
1072 invokers = inv = new Invokers(this);
1073 return inv;
1074 }
1075
1076 /** Reports the number of JVM stack slots which carry all parameters including and after
1077 * the given position, which must be in the range of 0 to
1078 * {@code parameterCount} inclusive. Successive parameters are
1079 * more shallowly stacked, and parameters are indexed in the bytecodes
1080 * according to their trailing edge. Thus, to obtain the depth
1081 * in the outgoing call stack of parameter {@code N}, obtain
1082 * the {@code parameterSlotDepth} of its trailing edge
1083 * at position {@code N+1}.
1084 * <p>
1085 * Parameters of type {@code long} and {@code double} occupy
1086 * two stack slots (for historical reasons) and all others occupy one.
1087 * Therefore, the number returned is the number of arguments
1088 * <em>including</em> and <em>after</em> the given parameter,
1089 * <em>plus</em> the number of long or double arguments
1090 * at or after the argument for the given parameter.
1091 * <p>
1092 * This method is included for the benefit of applications that must
1093 * generate bytecodes that process method handles and invokedynamic.
1094 * @param num an index (zero-based, inclusive) within the parameter types
1095 * @return the index of the (shallowest) JVM stack slot transmitting the
1096 * given parameter
1097 * @throws IllegalArgumentException if {@code num} is negative or greater than {@code parameterCount()}
1098 */
1099 /*non-public*/ int parameterSlotDepth(int num) {
1100 if (num < 0 || num > ptypes.length)
1101 parameterType(num); // force a range check
1102 return form.parameterToArgSlot(num-1);
1103 }
1104
1105 /** Reports the number of JVM stack slots required to receive a return value
1106 * from a method of this type.
1107 * If the {@link #returnType() return type} is void, it will be zero,
1108 * else if the return type is long or double, it will be two, else one.
1109 * <p>
1110 * This method is included for the benefit of applications that must
1111 * generate bytecodes that process method handles and invokedynamic.
1112 * @return the number of JVM stack slots (0, 1, or 2) for this type's return value
1113 * Will be removed for PFD.
1114 */
1115 /*non-public*/ int returnSlotCount() {
1116 return form.returnSlotCount();
1117 }
1118
1119 /**
1120 * Finds or creates an instance of a method type, given the spelling of its bytecode descriptor.
1121 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
1122 * Any class or interface name embedded in the descriptor string
1123 * will be resolved by calling {@link ClassLoader#loadClass(java.lang.String)}
1124 * on the given loader (or if it is null, on the system class loader).
1125 * <p>
1126 * Note that it is possible to encounter method types which cannot be
1127 * constructed by this method, because their component types are
1128 * not all reachable from a common class loader.
1129 * <p>
1130 * This method is included for the benefit of applications that must
1131 * generate bytecodes that process method handles and {@code invokedynamic}.
1132 * @param descriptor a bytecode-level type descriptor string "(T...)T"
1133 * @param loader the class loader in which to look up the types
1134 * @return a method type matching the bytecode-level type descriptor
1135 * @throws NullPointerException if the string is null
1136 * @throws IllegalArgumentException if the string is not well-formed
1137 * @throws TypeNotPresentException if a named type cannot be found
1138 */
1139 public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader)
1140 throws IllegalArgumentException, TypeNotPresentException
1141 {
1142 return fromDescriptor(descriptor,
1143 (loader == null) ? ClassLoader.getSystemClassLoader() : loader);
1144 }
1145
1146 /**
1147 * Same as {@link #fromMethodDescriptorString(String, ClassLoader)}, but
1148 * {@code null} ClassLoader means the bootstrap loader is used here.
1149 * <p>
1150 * IMPORTANT: This method is preferable for JDK internal use as it more
1151 * correctly interprets {@code null} ClassLoader than
1152 * {@link #fromMethodDescriptorString(String, ClassLoader)}.
1153 * Use of this method also avoids early initialization issues when system
1154 * ClassLoader is not initialized yet.
1155 */
1156 static MethodType fromDescriptor(String descriptor, ClassLoader loader)
1157 throws IllegalArgumentException, TypeNotPresentException
1158 {
1159 if (!descriptor.startsWith("(") || // also generates NPE if needed
1160 descriptor.indexOf(')') < 0 ||
1161 descriptor.indexOf('.') >= 0)
1162 throw newIllegalArgumentException("not a method descriptor: "+descriptor);
1163 List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader);
1164 Class<?> rtype = types.remove(types.size() - 1);
1165 Class<?>[] ptypes = listToArray(types);
1166 return makeImpl(rtype, ptypes, true);
1167 }
1168
1169 /**
1170 * Produces a bytecode descriptor representation of the method type.
1171 * <p>
1172 * Note that this is not a strict inverse of {@link #fromMethodDescriptorString fromMethodDescriptorString}.
1173 * Two distinct classes which share a common name but have different class loaders
1174 * will appear identical when viewed within descriptor strings.
1175 * <p>
1176 * This method is included for the benefit of applications that must
1177 * generate bytecodes that process method handles and {@code invokedynamic}.
1178 * {@link #fromMethodDescriptorString(java.lang.String, java.lang.ClassLoader) fromMethodDescriptorString},
1179 * because the latter requires a suitable class loader argument.
1180 * @return the bytecode type descriptor representation
1181 */
1182 public String toMethodDescriptorString() {
1183 String desc = methodDescriptor;
1184 if (desc == null) {
1185 desc = BytecodeDescriptor.unparseMethod(this.rtype, this.ptypes);
1186 methodDescriptor = desc;
1187 }
1188 return desc;
1189 }
1190
1191 /**
1192 * Return a field type descriptor string for this type
1193 *
1194 * @return the descriptor string
1195 * @jvms 4.3.2 Field Descriptors
1196 * @since 12
1197 */
1198 @Override
1199 public String descriptorString() {
1200 return toMethodDescriptorString();
1201 }
1202
1203 /*non-public*/ static String toFieldDescriptorString(Class<?> cls) {
1204 return BytecodeDescriptor.unparse(cls);
1205 }
1206
1207 /**
1208 * Return a nominal descriptor for this instance, if one can be
1209 * constructed, or an empty {@link Optional} if one cannot be.
1210 *
1211 * @return An {@link Optional} containing the resulting nominal descriptor,
1212 * or an empty {@link Optional} if one cannot be constructed.
1213 * @since 12
1214 */
1215 @Override
1216 public Optional<MethodTypeDesc> describeConstable() {
1217 try {
1218 return Optional.of(MethodTypeDesc.of(returnType().describeConstable().orElseThrow(),
1219 Stream.of(parameterArray())
1220 .map(p -> p.describeConstable().orElseThrow())
1221 .toArray(ClassDesc[]::new)));
1222 }
1223 catch (NoSuchElementException e) {
1224 return Optional.empty();
1225 }
1226 }
1227
1228 /// Serialization.
1229
1230 /**
1231 * There are no serializable fields for {@code MethodType}.
1232 */
1233 @java.io.Serial
1234 private static final java.io.ObjectStreamField[] serialPersistentFields = { };
1235
1236 /**
1237 * Save the {@code MethodType} instance to a stream.
1238 *
1239 * @serialData
1240 * For portability, the serialized format does not refer to named fields.
1241 * Instead, the return type and parameter type arrays are written directly
1242 * from the {@code writeObject} method, using two calls to {@code s.writeObject}
1243 * as follows:
1244 * <blockquote><pre>{@code
1245 s.writeObject(this.returnType());
1246 s.writeObject(this.parameterArray());
1247 * }</pre></blockquote>
1248 * <p>
1249 * The deserialized field values are checked as if they were
1250 * provided to the factory method {@link #methodType(Class,Class[]) methodType}.
1251 * For example, null values, or {@code void} parameter types,
1252 * will lead to exceptions during deserialization.
1253 * @param s the stream to write the object to
1254 * @throws java.io.IOException if there is a problem writing the object
1255 */
1256 @java.io.Serial
1257 private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
1258 s.defaultWriteObject(); // requires serialPersistentFields to be an empty array
1259 s.writeObject(returnType());
1260 s.writeObject(parameterArray());
1261 }
1262
1263 /**
1264 * Reconstitute the {@code MethodType} instance from a stream (that is,
1265 * deserialize it).
1266 * This instance is a scratch object with bogus final fields.
1267 * It provides the parameters to the factory method called by
1268 * {@link #readResolve readResolve}.
1269 * After that call it is discarded.
1270 * @param s the stream to read the object from
1271 * @throws java.io.IOException if there is a problem reading the object
1272 * @throws ClassNotFoundException if one of the component classes cannot be resolved
1273 * @see #readResolve
1274 * @see #writeObject
1275 */
1276 @java.io.Serial
1277 private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
1278 // Assign temporary defaults in case this object escapes
1279 MethodType_init(void.class, NO_PTYPES);
1280
1281 s.defaultReadObject(); // requires serialPersistentFields to be an empty array
1282
1283 Class<?> returnType = (Class<?>) s.readObject();
1284 Class<?>[] parameterArray = (Class<?>[]) s.readObject();
1285 parameterArray = parameterArray.clone(); // make sure it is unshared
1286
1287 // Assign deserialized values
1288 MethodType_init(returnType, parameterArray);
1289 }
1290
1291 // Initialization of state for deserialization only
1292 private void MethodType_init(Class<?> rtype, Class<?>[] ptypes) {
1293 // In order to communicate these values to readResolve, we must
1294 // store them into the implementation-specific final fields.
1295 checkRtype(rtype);
1296 checkPtypes(ptypes);
1297 UNSAFE.putReference(this, OffsetHolder.rtypeOffset, rtype);
1298 UNSAFE.putReference(this, OffsetHolder.ptypesOffset, ptypes);
1299 }
1300
1301 // Support for resetting final fields while deserializing. Implement Holder
1302 // pattern to make the rarely needed offset calculation lazy.
1303 private static class OffsetHolder {
1304 static final long rtypeOffset
1305 = UNSAFE.objectFieldOffset(MethodType.class, "rtype");
1306
1307 static final long ptypesOffset
1308 = UNSAFE.objectFieldOffset(MethodType.class, "ptypes");
1309 }
1310
1311 /**
1312 * Resolves and initializes a {@code MethodType} object
1313 * after serialization.
1314 * @return the fully initialized {@code MethodType} object
1315 */
1316 @java.io.Serial
1317 private Object readResolve() {
1318 // Do not use a trusted path for deserialization:
1319 // return makeImpl(rtype, ptypes, true);
1320 // Verify all operands, and make sure ptypes is unshared:
1321 try {
1322 return methodType(rtype, ptypes);
1323 } finally {
1324 // Re-assign defaults in case this object escapes
1325 MethodType_init(void.class, NO_PTYPES);
1326 }
1327 }
1328
1329 /**
1330 * Simple implementation of weak concurrent intern set.
1331 *
1332 * @param <T> interned type
1333 */
1334 private static class ConcurrentWeakInternSet<T> {
1335
1336 private final ConcurrentMap<WeakEntry<T>, WeakEntry<T>> map;
1337 private final ReferenceQueue<T> stale;
1338
1339 public ConcurrentWeakInternSet() {
1340 this.map = new ConcurrentHashMap<>(512);
1341 this.stale = new ReferenceQueue<>();
1342 }
1343
1344 /**
1345 * Get the existing interned element.
1346 * This method returns null if no element is interned.
1347 *
1348 * @param elem element to look up
1349 * @return the interned element
1350 */
1351 public T get(T elem) {
1352 if (elem == null) throw new NullPointerException();
1353 expungeStaleElements();
1354
1355 WeakEntry<T> value = map.get(elem);
1356 if (value != null) {
1357 T res = value.get();
1358 if (res != null) {
1359 return res;
1360 }
1361 }
1362 return null;
1363 }
1364
1365 /**
1366 * Interns the element.
1367 * Always returns non-null element, matching the one in the intern set.
1368 * Under the race against another add(), it can return <i>different</i>
1369 * element, if another thread beats us to interning it.
1370 *
1371 * @param elem element to add
1372 * @return element that was actually added
1373 */
1374 public T add(T elem) {
1375 if (elem == null) throw new NullPointerException();
1376
1377 // Playing double race here, and so spinloop is required.
1378 // First race is with two concurrent updaters.
1379 // Second race is with GC purging weak ref under our feet.
1380 // Hopefully, we almost always end up with a single pass.
1381 T interned;
1382 WeakEntry<T> e = new WeakEntry<>(elem, stale);
1383 do {
1384 expungeStaleElements();
1385 WeakEntry<T> exist = map.putIfAbsent(e, e);
1386 interned = (exist == null) ? elem : exist.get();
1387 } while (interned == null);
1388 return interned;
1389 }
1390
1391 private void expungeStaleElements() {
1392 Reference<? extends T> reference;
1393 while ((reference = stale.poll()) != null) {
1394 map.remove(reference);
1395 }
1396 }
1397
1398 private static class WeakEntry<T> extends WeakReference<T> {
1399
1400 public final int hashcode;
1401
1402 public WeakEntry(T key, ReferenceQueue<T> queue) {
1403 super(key, queue);
1404 hashcode = key.hashCode();
1405 }
1406
1407 /**
1408 * This implementation returns {@code true} if {@code obj} is another
1409 * {@code WeakEntry} whose referent is equals to this referent, or
1410 * if {@code obj} is equals to the referent of this. This allows
1411 * lookups to be made without wrapping in a {@code WeakEntry}.
1412 *
1413 * @param obj the object to compare
1414 * @return true if {@code obj} is equals to this or the referent of this
1415 * @see MethodType#equals(Object)
1416 * @see Object#equals(Object)
1417 */
1418 @Override
1419 public boolean equals(Object obj) {
1420 Object mine = get();
1421 if (obj instanceof WeakEntry) {
1422 Object that = ((WeakEntry) obj).get();
1423 return (that == null || mine == null) ? (this == obj) : mine.equals(that);
1424 }
1425 return (mine == null) ? (obj == null) : mine.equals(obj);
1426 }
1427
1428 @Override
1429 public int hashCode() {
1430 return hashcode;
1431 }
1432
1433 }
1434 }
1435
1436 }