1 /*
2 * Copyright (c) 2008, 2013, 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 sun.invoke.util.Wrapper;
29 import java.lang.ref.WeakReference;
30 import java.lang.ref.Reference;
31 import java.lang.ref.ReferenceQueue;
32 import java.util.Arrays;
33 import java.util.Collections;
34 import java.util.List;
35 import java.util.Objects;
36 import java.util.StringJoiner;
37 import java.util.concurrent.ConcurrentMap;
38 import java.util.concurrent.ConcurrentHashMap;
39 import sun.invoke.util.BytecodeDescriptor;
40 import static java.lang.invoke.MethodHandleStatics.*;
41 import sun.invoke.util.VerifyType;
42
43 /**
44 * A method type represents the arguments and return type accepted and
45 * returned by a method handle, or the arguments and return type passed
46 * and expected by a method handle caller. Method types must be properly
47 * matched between a method handle and all its callers,
48 * and the JVM's operations enforce this matching at, specifically
49 * during calls to {@link MethodHandle#invokeExact MethodHandle.invokeExact}
50 * and {@link MethodHandle#invoke MethodHandle.invoke}, and during execution
51 * of {@code invokedynamic} instructions.
52 * <p>
53 * The structure is a return type accompanied by any number of parameter types.
54 * The types (primitive, {@code void}, and reference) are represented by {@link Class} objects.
55 * (For ease of exposition, we treat {@code void} as if it were a type.
56 * In fact, it denotes the absence of a return type.)
57 * <p>
58 * All instances of {@code MethodType} are immutable.
59 * Two instances are completely interchangeable if they compare equal.
60 * Equality depends on pairwise correspondence of the return and parameter types and on nothing else.
61 * <p>
62 * This type can be created only by factory methods.
63 * All factory methods may cache values, though caching is not guaranteed.
64 * Some factory methods are static, while others are virtual methods which
65 * modify precursor method types, e.g., by changing a selected parameter.
66 * <p>
67 * Factory methods which operate on groups of parameter types
68 * are systematically presented in two versions, so that both Java arrays and
69 * Java lists can be used to work with groups of parameter types.
70 * The query methods {@code parameterArray} and {@code parameterList}
71 * also provide a choice between arrays and lists.
72 * <p>
73 * {@code MethodType} objects are sometimes derived from bytecode instructions
74 * such as {@code invokedynamic}, specifically from the type descriptor strings associated
75 * with the instructions in a class file's constant pool.
76 * <p>
77 * Like classes and strings, method types can also be represented directly
78 * in a class file's constant pool as constants.
79 * A method type may be loaded by an {@code ldc} instruction which refers
80 * to a suitable {@code CONSTANT_MethodType} constant pool entry.
81 * The entry refers to a {@code CONSTANT_Utf8} spelling for the descriptor string.
82 * (For full details on method type constants,
83 * see sections 4.4.8 and 5.4.3.5 of the Java Virtual Machine Specification.)
84 * <p>
85 * When the JVM materializes a {@code MethodType} from a descriptor string,
86 * all classes named in the descriptor must be accessible, and will be loaded.
87 * (But the classes need not be initialized, as is the case with a {@code CONSTANT_Class}.)
88 * This loading may occur at any time before the {@code MethodType} object is first derived.
89 * @author John Rose, JSR 292 EG
90 */
91 public final
92 class MethodType implements java.io.Serializable {
93 private static final long serialVersionUID = 292L; // {rtype, {ptype...}}
94
95 // The rtype and ptypes fields define the structural identity of the method type:
96 private final Class<?> rtype;
97 private final Class<?>[] ptypes;
98
99 // The remaining fields are caches of various sorts:
100 private @Stable MethodTypeForm form; // erased form, plus cached data about primitives
101 private @Stable MethodType wrapAlt; // alternative wrapped/unwrapped version
102 private @Stable Invokers invokers; // cache of handy higher-order adapters
103 private @Stable String methodDescriptor; // cache for toMethodDescriptorString
104
105 /**
106 * Check the given parameters for validity and store them into the final fields.
107 */
108 private MethodType(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {
109 checkRtype(rtype);
110 checkPtypes(ptypes);
111 this.rtype = rtype;
112 // defensively copy the array passed in by the user
113 this.ptypes = trusted ? ptypes : Arrays.copyOf(ptypes, ptypes.length);
114 }
115
116 /**
117 * Construct a temporary unchecked instance of MethodType for use only as a key to the intern table.
118 * Does not check the given parameters for validity, and must be discarded after it is used as a searching key.
119 * The parameters are reversed for this constructor, so that is is not accidentally used.
120 */
121 private MethodType(Class<?>[] ptypes, Class<?> rtype) {
122 this.rtype = rtype;
123 this.ptypes = ptypes;
124 }
125
126 /*trusted*/ MethodTypeForm form() { return form; }
127 /*trusted*/ Class<?> rtype() { return rtype; }
128 /*trusted*/ Class<?>[] ptypes() { return ptypes; }
129
130 void setForm(MethodTypeForm f) { form = f; }
131
132 /** This number, mandated by the JVM spec as 255,
133 * is the maximum number of <em>slots</em>
134 * that any Java method can receive in its argument list.
135 * It limits both JVM signatures and method type objects.
136 * The longest possible invocation will look like
137 * {@code staticMethod(arg1, arg2, ..., arg255)} or
138 * {@code x.virtualMethod(arg1, arg2, ..., arg254)}.
139 */
140 /*non-public*/ static final int MAX_JVM_ARITY = 255; // this is mandated by the JVM spec.
141
142 /** This number is the maximum arity of a method handle, 254.
143 * It is derived from the absolute JVM-imposed arity by subtracting one,
144 * which is the slot occupied by the method handle itself at the
145 * beginning of the argument list used to invoke the method handle.
146 * The longest possible invocation will look like
147 * {@code mh.invoke(arg1, arg2, ..., arg254)}.
148 */
149 // Issue: Should we allow MH.invokeWithArguments to go to the full 255?
150 /*non-public*/ static final int MAX_MH_ARITY = MAX_JVM_ARITY-1; // deduct one for mh receiver
151
152 /** This number is the maximum arity of a method handle invoker, 253.
153 * It is derived from the absolute JVM-imposed arity by subtracting two,
154 * which are the slots occupied by invoke method handle, and the
155 * target method handle, which are both at the beginning of the argument
156 * list used to invoke the target method handle.
157 * The longest possible invocation will look like
158 * {@code invokermh.invoke(targetmh, arg1, arg2, ..., arg253)}.
159 */
160 /*non-public*/ static final int MAX_MH_INVOKER_ARITY = MAX_MH_ARITY-1; // deduct one more for invoker
161
162 private static void checkRtype(Class<?> rtype) {
163 Objects.requireNonNull(rtype);
164 }
165 private static void checkPtype(Class<?> ptype) {
166 Objects.requireNonNull(ptype);
167 if (ptype == void.class)
168 throw newIllegalArgumentException("parameter type cannot be void");
169 }
170 /** Return number of extra slots (count of long/double args). */
171 private static int checkPtypes(Class<?>[] ptypes) {
172 int slots = 0;
173 for (Class<?> ptype : ptypes) {
174 checkPtype(ptype);
175 if (ptype == double.class || ptype == long.class) {
176 slots++;
177 }
178 }
179 checkSlotCount(ptypes.length + slots);
180 return slots;
181 }
182 static void checkSlotCount(int count) {
183 assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0);
184 // MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work:
185 if ((count & MAX_JVM_ARITY) != count)
186 throw newIllegalArgumentException("bad parameter count "+count);
187 }
188 private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) {
189 if (num instanceof Integer) num = "bad index: "+num;
190 return new IndexOutOfBoundsException(num.toString());
191 }
192
193 static final ConcurrentWeakInternSet<MethodType> internTable = new ConcurrentWeakInternSet<>();
194
195 static final Class<?>[] NO_PTYPES = {};
196
197 /**
198 * Finds or creates an instance of the given method type.
199 * @param rtype the return type
200 * @param ptypes the parameter types
201 * @return a method type with the given components
202 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
203 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
204 */
205 public static
206 MethodType methodType(Class<?> rtype, Class<?>[] ptypes) {
207 return makeImpl(rtype, ptypes, false);
208 }
209
210 /**
211 * Finds or creates a method type with the given components.
212 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
213 * @param rtype the return type
214 * @param ptypes the parameter types
215 * @return a method type with the given components
216 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
217 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
218 */
219 public static
220 MethodType methodType(Class<?> rtype, List<Class<?>> ptypes) {
221 boolean notrust = false; // random List impl. could return evil ptypes array
222 return makeImpl(rtype, listToArray(ptypes), notrust);
223 }
224
225 private static Class<?>[] listToArray(List<Class<?>> ptypes) {
226 // sanity check the size before the toArray call, since size might be huge
227 checkSlotCount(ptypes.size());
228 return ptypes.toArray(NO_PTYPES);
229 }
230
231 /**
232 * Finds or creates a method type with the given components.
233 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
234 * The leading parameter type is prepended to the remaining array.
235 * @param rtype the return type
236 * @param ptype0 the first parameter type
237 * @param ptypes the remaining parameter types
238 * @return a method type with the given components
239 * @throws NullPointerException if {@code rtype} or {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is null
240 * @throws IllegalArgumentException if {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is {@code void.class}
241 */
242 public static
243 MethodType methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes) {
244 Class<?>[] ptypes1 = new Class<?>[1+ptypes.length];
245 ptypes1[0] = ptype0;
246 System.arraycopy(ptypes, 0, ptypes1, 1, ptypes.length);
247 return makeImpl(rtype, ptypes1, true);
248 }
249
250 /**
251 * Finds or creates a method type with the given components.
252 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
253 * The resulting method has no parameter types.
254 * @param rtype the return type
255 * @return a method type with the given return value
256 * @throws NullPointerException if {@code rtype} is null
257 */
258 public static
259 MethodType methodType(Class<?> rtype) {
260 return makeImpl(rtype, NO_PTYPES, true);
261 }
262
263 /**
264 * Finds or creates a method type with the given components.
265 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
266 * The resulting method has the single given parameter type.
267 * @param rtype the return type
268 * @param ptype0 the parameter type
269 * @return a method type with the given return value and parameter type
270 * @throws NullPointerException if {@code rtype} or {@code ptype0} is null
271 * @throws IllegalArgumentException if {@code ptype0} is {@code void.class}
272 */
273 public static
274 MethodType methodType(Class<?> rtype, Class<?> ptype0) {
275 return makeImpl(rtype, new Class<?>[]{ ptype0 }, true);
276 }
277
278 /**
279 * Finds or creates a method type with the given components.
280 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
281 * The resulting method has the same parameter types as {@code ptypes},
282 * and the specified return type.
283 * @param rtype the return type
284 * @param ptypes the method type which supplies the parameter types
285 * @return a method type with the given components
286 * @throws NullPointerException if {@code rtype} or {@code ptypes} is null
287 */
288 public static
289 MethodType methodType(Class<?> rtype, MethodType ptypes) {
290 return makeImpl(rtype, ptypes.ptypes, true);
291 }
292
293 /**
294 * Sole factory method to find or create an interned method type.
295 * @param rtype desired return type
296 * @param ptypes desired parameter types
297 * @param trusted whether the ptypes can be used without cloning
298 * @return the unique method type of the desired structure
299 */
300 /*trusted*/ static
301 MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {
302 MethodType mt = internTable.get(new MethodType(ptypes, rtype));
303 if (mt != null)
304 return mt;
305 if (ptypes.length == 0) {
306 ptypes = NO_PTYPES; trusted = true;
307 }
308 mt = new MethodType(rtype, ptypes, trusted);
309 // promote the object to the Real Thing, and reprobe
310 mt.form = MethodTypeForm.findForm(mt);
311 return internTable.add(mt);
312 }
313 private static final MethodType[] objectOnlyTypes = new MethodType[20];
314
315 /**
316 * Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array.
317 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
318 * All parameters and the return type will be {@code Object},
319 * except the final array parameter if any, which will be {@code Object[]}.
320 * @param objectArgCount number of parameters (excluding the final array parameter if any)
321 * @param finalArray whether there will be a trailing array parameter, of type {@code Object[]}
322 * @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments
323 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true)
324 * @see #genericMethodType(int)
325 */
326 public static
327 MethodType genericMethodType(int objectArgCount, boolean finalArray) {
328 MethodType mt;
329 checkSlotCount(objectArgCount);
330 int ivarargs = (!finalArray ? 0 : 1);
331 int ootIndex = objectArgCount*2 + ivarargs;
332 if (ootIndex < objectOnlyTypes.length) {
333 mt = objectOnlyTypes[ootIndex];
334 if (mt != null) return mt;
335 }
336 Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs];
337 Arrays.fill(ptypes, Object.class);
338 if (ivarargs != 0) ptypes[objectArgCount] = Object[].class;
339 mt = makeImpl(Object.class, ptypes, true);
340 if (ootIndex < objectOnlyTypes.length) {
341 objectOnlyTypes[ootIndex] = mt; // cache it here also!
342 }
343 return mt;
344 }
345
346 /**
347 * Finds or creates a method type whose components are all {@code Object}.
348 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
349 * All parameters and the return type will be Object.
350 * @param objectArgCount number of parameters
351 * @return a generally applicable method type, for all calls of the given argument count
352 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255
353 * @see #genericMethodType(int, boolean)
354 */
355 public static
356 MethodType genericMethodType(int objectArgCount) {
357 return genericMethodType(objectArgCount, false);
358 }
359
360 /**
361 * Finds or creates a method type with a single different parameter type.
362 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
363 * @param num the index (zero-based) of the parameter type to change
364 * @param nptype a new parameter type to replace the old one with
365 * @return the same type, except with the selected parameter changed
366 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
367 * @throws IllegalArgumentException if {@code nptype} is {@code void.class}
368 * @throws NullPointerException if {@code nptype} is null
369 */
370 public MethodType changeParameterType(int num, Class<?> nptype) {
371 if (parameterType(num) == nptype) return this;
372 checkPtype(nptype);
373 Class<?>[] nptypes = ptypes.clone();
374 nptypes[num] = nptype;
375 return makeImpl(rtype, nptypes, true);
376 }
377
378 /**
379 * Finds or creates a method type with additional parameter types.
380 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
381 * @param num the position (zero-based) of the inserted parameter type(s)
382 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
383 * @return the same type, except with the selected parameter(s) inserted
384 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
385 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
386 * or if the resulting method type would have more than 255 parameter slots
387 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
388 */
389 public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) {
390 int len = ptypes.length;
391 if (num < 0 || num > len)
392 throw newIndexOutOfBoundsException(num);
393 int ins = checkPtypes(ptypesToInsert);
394 checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins);
395 int ilen = ptypesToInsert.length;
396 if (ilen == 0) return this;
397 Class<?>[] nptypes = Arrays.copyOfRange(ptypes, 0, len+ilen);
398 System.arraycopy(nptypes, num, nptypes, num+ilen, len-num);
399 System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen);
400 return makeImpl(rtype, nptypes, true);
401 }
402
403 /**
404 * Finds or creates a method type with additional parameter types.
405 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
406 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
407 * @return the same type, except with the selected parameter(s) appended
408 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
409 * or if the resulting method type would have more than 255 parameter slots
410 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
411 */
412 public MethodType appendParameterTypes(Class<?>... ptypesToInsert) {
413 return insertParameterTypes(parameterCount(), ptypesToInsert);
414 }
415
416 /**
417 * Finds or creates a method type with additional parameter types.
418 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
419 * @param num the position (zero-based) of the inserted parameter type(s)
420 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
421 * @return the same type, except with the selected parameter(s) inserted
422 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
423 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
424 * or if the resulting method type would have more than 255 parameter slots
425 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
426 */
427 public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) {
428 return insertParameterTypes(num, listToArray(ptypesToInsert));
429 }
430
431 /**
432 * Finds or creates a method type with additional parameter types.
433 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
434 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
435 * @return the same type, except with the selected parameter(s) appended
436 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
437 * or if the resulting method type would have more than 255 parameter slots
438 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
439 */
440 public MethodType appendParameterTypes(List<Class<?>> ptypesToInsert) {
441 return insertParameterTypes(parameterCount(), ptypesToInsert);
442 }
443
444 /**
445 * Finds or creates a method type with modified parameter types.
446 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
447 * @param start the position (zero-based) of the first replaced parameter type(s)
448 * @param end the position (zero-based) after the last replaced parameter type(s)
449 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
450 * @return the same type, except with the selected parameter(s) replaced
451 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
452 * or if {@code end} is negative or greater than {@code parameterCount()}
453 * or if {@code start} is greater than {@code end}
454 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
455 * or if the resulting method type would have more than 255 parameter slots
456 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
457 */
458 /*non-public*/ MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) {
459 if (start == end)
460 return insertParameterTypes(start, ptypesToInsert);
461 int len = ptypes.length;
462 if (!(0 <= start && start <= end && end <= len))
463 throw newIndexOutOfBoundsException("start="+start+" end="+end);
464 int ilen = ptypesToInsert.length;
465 if (ilen == 0)
466 return dropParameterTypes(start, end);
467 return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert);
468 }
469
470 /** Replace the last arrayLength parameter types with the component type of arrayType.
471 * @param arrayType any array type
472 * @param arrayLength the number of parameter types to change
473 * @return the resulting type
474 */
475 /*non-public*/ MethodType asSpreaderType(Class<?> arrayType, int arrayLength) {
476 assert(parameterCount() >= arrayLength);
477 int spreadPos = ptypes.length - arrayLength;
478 if (arrayLength == 0) return this; // nothing to change
479 if (arrayType == Object[].class) {
480 if (isGeneric()) return this; // nothing to change
481 if (spreadPos == 0) {
482 // no leading arguments to preserve; go generic
483 MethodType res = genericMethodType(arrayLength);
484 if (rtype != Object.class) {
485 res = res.changeReturnType(rtype);
486 }
487 return res;
488 }
489 }
490 Class<?> elemType = arrayType.getComponentType();
491 assert(elemType != null);
492 for (int i = spreadPos; i < ptypes.length; i++) {
493 if (ptypes[i] != elemType) {
494 Class<?>[] fixedPtypes = ptypes.clone();
495 Arrays.fill(fixedPtypes, i, ptypes.length, elemType);
496 return methodType(rtype, fixedPtypes);
497 }
498 }
499 return this; // arguments check out; no change
500 }
501
502 /** Return the leading parameter type, which must exist and be a reference.
503 * @return the leading parameter type, after error checks
504 */
505 /*non-public*/ Class<?> leadingReferenceParameter() {
506 Class<?> ptype;
507 if (ptypes.length == 0 ||
508 (ptype = ptypes[0]).isPrimitive())
509 throw newIllegalArgumentException("no leading reference parameter");
510 return ptype;
511 }
512
513 /** Delete the last parameter type and replace it with arrayLength copies of the component type of arrayType.
514 * @param arrayType any array type
515 * @param arrayLength the number of parameter types to insert
516 * @return the resulting type
517 */
518 /*non-public*/ MethodType asCollectorType(Class<?> arrayType, int arrayLength) {
519 assert(parameterCount() >= 1);
520 assert(lastParameterType().isAssignableFrom(arrayType));
521 MethodType res;
522 if (arrayType == Object[].class) {
523 res = genericMethodType(arrayLength);
524 if (rtype != Object.class) {
525 res = res.changeReturnType(rtype);
526 }
527 } else {
528 Class<?> elemType = arrayType.getComponentType();
529 assert(elemType != null);
530 res = methodType(rtype, Collections.nCopies(arrayLength, elemType));
531 }
532 if (ptypes.length == 1) {
533 return res;
534 } else {
535 return res.insertParameterTypes(0, parameterList().subList(0, ptypes.length-1));
536 }
537 }
538
539 /**
540 * Finds or creates a method type with some parameter types omitted.
541 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
542 * @param start the index (zero-based) of the first parameter type to remove
543 * @param end the index (greater than {@code start}) of the first parameter type after not to remove
544 * @return the same type, except with the selected parameter(s) removed
545 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
546 * or if {@code end} is negative or greater than {@code parameterCount()}
547 * or if {@code start} is greater than {@code end}
548 */
549 public MethodType dropParameterTypes(int start, int end) {
550 int len = ptypes.length;
551 if (!(0 <= start && start <= end && end <= len))
552 throw newIndexOutOfBoundsException("start="+start+" end="+end);
553 if (start == end) return this;
554 Class<?>[] nptypes;
555 if (start == 0) {
556 if (end == len) {
557 // drop all parameters
558 nptypes = NO_PTYPES;
559 } else {
560 // drop initial parameter(s)
561 nptypes = Arrays.copyOfRange(ptypes, end, len);
562 }
563 } else {
564 if (end == len) {
565 // drop trailing parameter(s)
566 nptypes = Arrays.copyOfRange(ptypes, 0, start);
567 } else {
568 int tail = len - end;
569 nptypes = Arrays.copyOfRange(ptypes, 0, start + tail);
570 System.arraycopy(ptypes, end, nptypes, start, tail);
571 }
572 }
573 return makeImpl(rtype, nptypes, true);
574 }
575
576 /**
577 * Finds or creates a method type with a different return type.
578 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
579 * @param nrtype a return parameter type to replace the old one with
580 * @return the same type, except with the return type change
581 * @throws NullPointerException if {@code nrtype} is null
582 */
583 public MethodType changeReturnType(Class<?> nrtype) {
584 if (returnType() == nrtype) return this;
585 return makeImpl(nrtype, ptypes, true);
586 }
587
588 /**
589 * Reports if this type contains a primitive argument or return value.
590 * The return type {@code void} counts as a primitive.
591 * @return true if any of the types are primitives
592 */
593 public boolean hasPrimitives() {
594 return form.hasPrimitives();
595 }
596
597 /**
598 * Reports if this type contains a wrapper argument or return value.
599 * Wrappers are types which box primitive values, such as {@link Integer}.
600 * The reference type {@code java.lang.Void} counts as a wrapper,
601 * if it occurs as a return type.
602 * @return true if any of the types are wrappers
603 */
604 public boolean hasWrappers() {
605 return unwrap() != this;
606 }
607
608 /**
609 * Erases all reference types to {@code Object}.
610 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
611 * All primitive types (including {@code void}) will remain unchanged.
612 * @return a version of the original type with all reference types replaced
613 */
614 public MethodType erase() {
615 return form.erasedType();
616 }
617
618 /**
619 * Erases all reference types to {@code Object}, and all subword types to {@code int}.
620 * This is the reduced type polymorphism used by private methods
621 * such as {@link MethodHandle#invokeBasic invokeBasic}.
622 * @return a version of the original type with all reference and subword types replaced
623 */
624 /*non-public*/ MethodType basicType() {
625 return form.basicType();
626 }
627
628 /**
629 * @return a version of the original type with MethodHandle prepended as the first argument
630 */
631 /*non-public*/ MethodType invokerType() {
632 return insertParameterTypes(0, MethodHandle.class);
633 }
634
635 /**
636 * Converts all types, both reference and primitive, to {@code Object}.
637 * Convenience method for {@link #genericMethodType(int) genericMethodType}.
638 * The expression {@code type.wrap().erase()} produces the same value
639 * as {@code type.generic()}.
640 * @return a version of the original type with all types replaced
641 */
642 public MethodType generic() {
643 return genericMethodType(parameterCount());
644 }
645
646 /*non-public*/ boolean isGeneric() {
647 return this == erase() && !hasPrimitives();
648 }
649
650 /**
651 * Converts all primitive types to their corresponding wrapper types.
652 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
653 * All reference types (including wrapper types) will remain unchanged.
654 * A {@code void} return type is changed to the type {@code java.lang.Void}.
655 * The expression {@code type.wrap().erase()} produces the same value
656 * as {@code type.generic()}.
657 * @return a version of the original type with all primitive types replaced
658 */
659 public MethodType wrap() {
660 return hasPrimitives() ? wrapWithPrims(this) : this;
661 }
662
663 /**
664 * Converts all wrapper types to their corresponding primitive types.
665 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
666 * All primitive types (including {@code void}) will remain unchanged.
667 * A return type of {@code java.lang.Void} is changed to {@code void}.
668 * @return a version of the original type with all wrapper types replaced
669 */
670 public MethodType unwrap() {
671 MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this);
672 return unwrapWithNoPrims(noprims);
673 }
674
675 private static MethodType wrapWithPrims(MethodType pt) {
676 assert(pt.hasPrimitives());
677 MethodType wt = pt.wrapAlt;
678 if (wt == null) {
679 // fill in lazily
680 wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP, MethodTypeForm.WRAP);
681 assert(wt != null);
682 pt.wrapAlt = wt;
683 }
684 return wt;
685 }
686
687 private static MethodType unwrapWithNoPrims(MethodType wt) {
688 assert(!wt.hasPrimitives());
689 MethodType uwt = wt.wrapAlt;
690 if (uwt == null) {
691 // fill in lazily
692 uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP, MethodTypeForm.UNWRAP);
693 if (uwt == null)
694 uwt = wt; // type has no wrappers or prims at all
695 wt.wrapAlt = uwt;
696 }
697 return uwt;
698 }
699
700 /**
701 * Returns the parameter type at the specified index, within this method type.
702 * @param num the index (zero-based) of the desired parameter type
703 * @return the selected parameter type
704 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
705 */
706 public Class<?> parameterType(int num) {
707 return ptypes[num];
708 }
709 /**
710 * Returns the number of parameter types in this method type.
711 * @return the number of parameter types
712 */
713 public int parameterCount() {
714 return ptypes.length;
715 }
716 /**
717 * Returns the return type of this method type.
718 * @return the return type
719 */
720 public Class<?> returnType() {
721 return rtype;
722 }
723
724 /**
725 * Presents the parameter types as a list (a convenience method).
726 * The list will be immutable.
727 * @return the parameter types (as an immutable list)
728 */
729 public List<Class<?>> parameterList() {
730 return Collections.unmodifiableList(Arrays.asList(ptypes));
731 }
732
733 /*non-public*/ Class<?> lastParameterType() {
734 int len = ptypes.length;
735 return len == 0 ? void.class : ptypes[len-1];
736 }
737
738 /**
739 * Presents the parameter types as an array (a convenience method).
740 * Changes to the array will not result in changes to the type.
741 * @return the parameter types (as a fresh copy if necessary)
742 */
743 public Class<?>[] parameterArray() {
744 return ptypes.clone();
745 }
746
747 /**
748 * Compares the specified object with this type for equality.
749 * That is, it returns <tt>true</tt> if and only if the specified object
750 * is also a method type with exactly the same parameters and return type.
751 * @param x object to compare
752 * @see Object#equals(Object)
753 */
754 @Override
755 public boolean equals(Object x) {
756 return this == x || x instanceof MethodType && equals((MethodType)x);
757 }
758
759 private boolean equals(MethodType that) {
760 return this.rtype == that.rtype
761 && Arrays.equals(this.ptypes, that.ptypes);
762 }
763
764 /**
765 * Returns the hash code value for this method type.
766 * It is defined to be the same as the hashcode of a List
767 * whose elements are the return type followed by the
768 * parameter types.
769 * @return the hash code value for this method type
770 * @see Object#hashCode()
771 * @see #equals(Object)
772 * @see List#hashCode()
773 */
774 @Override
775 public int hashCode() {
776 int hashCode = 31 + rtype.hashCode();
777 for (Class<?> ptype : ptypes)
778 hashCode = 31*hashCode + ptype.hashCode();
779 return hashCode;
780 }
781
782 /**
783 * Returns a string representation of the method type,
784 * of the form {@code "(PT0,PT1...)RT"}.
785 * The string representation of a method type is a
786 * parenthesis enclosed, comma separated list of type names,
787 * followed immediately by the return type.
788 * <p>
789 * Each type is represented by its
790 * {@link java.lang.Class#getSimpleName simple name}.
791 */
792 @Override
793 public String toString() {
794 StringJoiner sj = new StringJoiner(",", "(",
795 ")" + rtype.getSimpleName());
796 for (int i = 0; i < ptypes.length; i++) {
797 sj.add(ptypes[i].getSimpleName());
798 }
799 return sj.toString();
800 }
801
802 /** True if the old return type can always be viewed (w/o casting) under new return type,
803 * and the new parameters can be viewed (w/o casting) under the old parameter types.
804 */
805 /*non-public*/
806 boolean isViewableAs(MethodType newType, boolean keepInterfaces) {
807 if (!VerifyType.isNullConversion(returnType(), newType.returnType(), keepInterfaces))
808 return false;
809 return parametersAreViewableAs(newType, keepInterfaces);
810 }
811 /** True if the new parameters can be viewed (w/o casting) under the old parameter types. */
812 /*non-public*/
813 boolean parametersAreViewableAs(MethodType newType, boolean keepInterfaces) {
814 if (form == newType.form && form.erasedType == this)
815 return true; // my reference parameters are all Object
816 if (ptypes == newType.ptypes)
817 return true;
818 int argc = parameterCount();
819 if (argc != newType.parameterCount())
820 return false;
821 for (int i = 0; i < argc; i++) {
822 if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i), keepInterfaces))
823 return false;
824 }
825 return true;
826 }
827 /*non-public*/
828 boolean isConvertibleTo(MethodType newType) {
829 MethodTypeForm oldForm = this.form();
830 MethodTypeForm newForm = newType.form();
831 if (oldForm == newForm)
832 // same parameter count, same primitive/object mix
833 return true;
834 if (!canConvert(returnType(), newType.returnType()))
835 return false;
836 Class<?>[] srcTypes = newType.ptypes;
837 Class<?>[] dstTypes = ptypes;
838 if (srcTypes == dstTypes)
839 return true;
840 int argc;
841 if ((argc = srcTypes.length) != dstTypes.length)
842 return false;
843 if (argc <= 1) {
844 if (argc == 1 && !canConvert(srcTypes[0], dstTypes[0]))
845 return false;
846 return true;
847 }
848 if ((oldForm.primitiveParameterCount() == 0 && oldForm.erasedType == this) ||
849 (newForm.primitiveParameterCount() == 0 && newForm.erasedType == newType)) {
850 // Somewhat complicated test to avoid a loop of 2 or more trips.
851 // If either type has only Object parameters, we know we can convert.
852 assert(canConvertParameters(srcTypes, dstTypes));
853 return true;
854 }
855 return canConvertParameters(srcTypes, dstTypes);
856 }
857
858 /** Returns true if MHs.explicitCastArguments produces the same result as MH.asType.
859 * If the type conversion is impossible for either, the result should be false.
860 */
861 /*non-public*/
862 boolean explicitCastEquivalentToAsType(MethodType newType) {
863 if (this == newType) return true;
864 if (!explicitCastEquivalentToAsType(rtype, newType.rtype)) {
865 return false;
866 }
867 Class<?>[] srcTypes = newType.ptypes;
868 Class<?>[] dstTypes = ptypes;
869 if (dstTypes == srcTypes) {
870 return true;
871 }
872 if (dstTypes.length != srcTypes.length) {
873 return false;
874 }
875 for (int i = 0; i < dstTypes.length; i++) {
876 if (!explicitCastEquivalentToAsType(srcTypes[i], dstTypes[i])) {
877 return false;
878 }
879 }
880 return true;
881 }
882
883 /** Reports true if the src can be converted to the dst, by both asType and MHs.eCE,
884 * and with the same effect.
885 * MHs.eCA has the following "upgrades" to MH.asType:
886 * 1. interfaces are unchecked (that is, treated as if aliased to Object)
887 * Therefore, {@code Object->CharSequence} is possible in both cases but has different semantics
888 * 2. the full matrix of primitive-to-primitive conversions is supported
889 * Narrowing like {@code long->byte} and basic-typing like {@code boolean->int}
890 * are not supported by asType, but anything supported by asType is equivalent
891 * with MHs.eCE.
892 * 3a. unboxing conversions can be followed by the full matrix of primitive conversions
893 * 3b. unboxing of null is permitted (creates a zero primitive value)
894 * Most unboxing conversions, like {@code Object->int}, has potentially
895 * different behaviors for asType vs. MHs.eCE, because the dynamic value
896 * might be a wrapper of a type that requires narrowing, like {@code (Object)1L->byte}.
897 * The equivalence is only certain if the static src type is a wrapper,
898 * and the conversion will be a widening one.
899 * Other than interfaces, reference-to-reference conversions are the same.
900 * Boxing primitives to references is the same for both operators.
901 */
902 private static boolean explicitCastEquivalentToAsType(Class<?> src, Class<?> dst) {
903 if (src == dst || dst == Object.class || dst == void.class) return true;
904 if (src.isPrimitive()) {
905 // Could be a prim/prim conversion, where casting is a strict superset.
906 // Or a boxing conversion, which is always to an exact wrapper class.
907 return canConvert(src, dst);
908 } else if (dst.isPrimitive()) {
909 Wrapper dw = Wrapper.forPrimitiveType(dst);
910 // Watch out: If src is Number or Object, we could get dynamic narrowing conversion.
911 // The conversion is known to be widening only if the wrapper type is statically visible.
912 return (Wrapper.isWrapperType(src) &&
913 dw.isConvertibleFrom(Wrapper.forWrapperType(src)));
914 } else {
915 // R->R always works, but we have to avoid a check-cast to an interface.
916 return !dst.isInterface() || dst.isAssignableFrom(src);
917 }
918 }
919
920 private boolean canConvertParameters(Class<?>[] srcTypes, Class<?>[] dstTypes) {
921 for (int i = 0; i < srcTypes.length; i++) {
922 if (!canConvert(srcTypes[i], dstTypes[i])) {
923 return false;
924 }
925 }
926 return true;
927 }
928
929 /*non-public*/
930 static boolean canConvert(Class<?> src, Class<?> dst) {
931 // short-circuit a few cases:
932 if (src == dst || src == Object.class || dst == Object.class) return true;
933 // the remainder of this logic is documented in MethodHandle.asType
934 if (src.isPrimitive()) {
935 // can force void to an explicit null, a la reflect.Method.invoke
936 // can also force void to a primitive zero, by analogy
937 if (src == void.class) return true; //or !dst.isPrimitive()?
938 Wrapper sw = Wrapper.forPrimitiveType(src);
939 if (dst.isPrimitive()) {
940 // P->P must widen
941 return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw);
942 } else {
943 // P->R must box and widen
944 return dst.isAssignableFrom(sw.wrapperType());
945 }
946 } else if (dst.isPrimitive()) {
947 // any value can be dropped
948 if (dst == void.class) return true;
949 Wrapper dw = Wrapper.forPrimitiveType(dst);
950 // R->P must be able to unbox (from a dynamically chosen type) and widen
951 // For example:
952 // Byte/Number/Comparable/Object -> dw:Byte -> byte.
953 // Character/Comparable/Object -> dw:Character -> char
954 // Boolean/Comparable/Object -> dw:Boolean -> boolean
955 // This means that dw must be cast-compatible with src.
956 if (src.isAssignableFrom(dw.wrapperType())) {
957 return true;
958 }
959 // The above does not work if the source reference is strongly typed
960 // to a wrapper whose primitive must be widened. For example:
961 // Byte -> unbox:byte -> short/int/long/float/double
962 // Character -> unbox:char -> int/long/float/double
963 if (Wrapper.isWrapperType(src) &&
964 dw.isConvertibleFrom(Wrapper.forWrapperType(src))) {
965 // can unbox from src and then widen to dst
966 return true;
967 }
968 // We have already covered cases which arise due to runtime unboxing
969 // of a reference type which covers several wrapper types:
970 // Object -> cast:Integer -> unbox:int -> long/float/double
971 // Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double
972 // An marginal case is Number -> dw:Character -> char, which would be OK if there were a
973 // subclass of Number which wraps a value that can convert to char.
974 // Since there is none, we don't need an extra check here to cover char or boolean.
975 return false;
976 } else {
977 // R->R always works, since null is always valid dynamically
978 return true;
979 }
980 }
981
982 /// Queries which have to do with the bytecode architecture
983
984 /** Reports the number of JVM stack slots required to invoke a method
985 * of this type. Note that (for historical reasons) the JVM requires
986 * a second stack slot to pass long and double arguments.
987 * So this method returns {@link #parameterCount() parameterCount} plus the
988 * number of long and double parameters (if any).
989 * <p>
990 * This method is included for the benefit of applications that must
991 * generate bytecodes that process method handles and invokedynamic.
992 * @return the number of JVM stack slots for this type's parameters
993 */
994 /*non-public*/ int parameterSlotCount() {
995 return form.parameterSlotCount();
996 }
997
998 /*non-public*/ Invokers invokers() {
999 Invokers inv = invokers;
1000 if (inv != null) return inv;
1001 invokers = inv = new Invokers(this);
1002 return inv;
1003 }
1004
1005 /** Reports the number of JVM stack slots which carry all parameters including and after
1006 * the given position, which must be in the range of 0 to
1007 * {@code parameterCount} inclusive. Successive parameters are
1008 * more shallowly stacked, and parameters are indexed in the bytecodes
1009 * according to their trailing edge. Thus, to obtain the depth
1010 * in the outgoing call stack of parameter {@code N}, obtain
1011 * the {@code parameterSlotDepth} of its trailing edge
1012 * at position {@code N+1}.
1013 * <p>
1014 * Parameters of type {@code long} and {@code double} occupy
1015 * two stack slots (for historical reasons) and all others occupy one.
1016 * Therefore, the number returned is the number of arguments
1017 * <em>including</em> and <em>after</em> the given parameter,
1018 * <em>plus</em> the number of long or double arguments
1019 * at or after after the argument for the given parameter.
1020 * <p>
1021 * This method is included for the benefit of applications that must
1022 * generate bytecodes that process method handles and invokedynamic.
1023 * @param num an index (zero-based, inclusive) within the parameter types
1024 * @return the index of the (shallowest) JVM stack slot transmitting the
1025 * given parameter
1026 * @throws IllegalArgumentException if {@code num} is negative or greater than {@code parameterCount()}
1027 */
1028 /*non-public*/ int parameterSlotDepth(int num) {
1029 if (num < 0 || num > ptypes.length)
1030 parameterType(num); // force a range check
1031 return form.parameterToArgSlot(num-1);
1032 }
1033
1034 /** Reports the number of JVM stack slots required to receive a return value
1035 * from a method of this type.
1036 * If the {@link #returnType() return type} is void, it will be zero,
1037 * else if the return type is long or double, it will be two, else one.
1038 * <p>
1039 * This method is included for the benefit of applications that must
1040 * generate bytecodes that process method handles and invokedynamic.
1041 * @return the number of JVM stack slots (0, 1, or 2) for this type's return value
1042 * Will be removed for PFD.
1043 */
1044 /*non-public*/ int returnSlotCount() {
1045 return form.returnSlotCount();
1046 }
1047
1048 /**
1049 * Finds or creates an instance of a method type, given the spelling of its bytecode descriptor.
1050 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
1051 * Any class or interface name embedded in the descriptor string
1052 * will be resolved by calling {@link ClassLoader#loadClass(java.lang.String)}
1053 * on the given loader (or if it is null, on the system class loader).
1054 * <p>
1055 * Note that it is possible to encounter method types which cannot be
1056 * constructed by this method, because their component types are
1057 * not all reachable from a common class loader.
1058 * <p>
1059 * This method is included for the benefit of applications that must
1060 * generate bytecodes that process method handles and {@code invokedynamic}.
1061 * @param descriptor a bytecode-level type descriptor string "(T...)T"
1062 * @param loader the class loader in which to look up the types
1063 * @return a method type matching the bytecode-level type descriptor
1064 * @throws NullPointerException if the string is null
1065 * @throws IllegalArgumentException if the string is not well-formed
1066 * @throws TypeNotPresentException if a named type cannot be found
1067 */
1068 public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader)
1069 throws IllegalArgumentException, TypeNotPresentException
1070 {
1071 if (!descriptor.startsWith("(") || // also generates NPE if needed
1072 descriptor.indexOf(')') < 0 ||
1073 descriptor.indexOf('.') >= 0)
1074 throw newIllegalArgumentException("not a method descriptor: "+descriptor);
1075 List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader);
1076 Class<?> rtype = types.remove(types.size() - 1);
1077 checkSlotCount(types.size());
1078 Class<?>[] ptypes = listToArray(types);
1079 return makeImpl(rtype, ptypes, true);
1080 }
1081
1082 /**
1083 * Produces a bytecode descriptor representation of the method type.
1084 * <p>
1085 * Note that this is not a strict inverse of {@link #fromMethodDescriptorString fromMethodDescriptorString}.
1086 * Two distinct classes which share a common name but have different class loaders
1087 * will appear identical when viewed within descriptor strings.
1088 * <p>
1089 * This method is included for the benefit of applications that must
1090 * generate bytecodes that process method handles and {@code invokedynamic}.
1091 * {@link #fromMethodDescriptorString(java.lang.String, java.lang.ClassLoader) fromMethodDescriptorString},
1092 * because the latter requires a suitable class loader argument.
1093 * @return the bytecode type descriptor representation
1094 */
1095 public String toMethodDescriptorString() {
1096 String desc = methodDescriptor;
1097 if (desc == null) {
1098 desc = BytecodeDescriptor.unparse(this);
1099 methodDescriptor = desc;
1100 }
1101 return desc;
1102 }
1103
1104 /*non-public*/ static String toFieldDescriptorString(Class<?> cls) {
1105 return BytecodeDescriptor.unparse(cls);
1106 }
1107
1108 /// Serialization.
1109
1110 /**
1111 * There are no serializable fields for {@code MethodType}.
1112 */
1113 private static final java.io.ObjectStreamField[] serialPersistentFields = { };
1114
1115 /**
1116 * Save the {@code MethodType} instance to a stream.
1117 *
1118 * @serialData
1119 * For portability, the serialized format does not refer to named fields.
1120 * Instead, the return type and parameter type arrays are written directly
1121 * from the {@code writeObject} method, using two calls to {@code s.writeObject}
1122 * as follows:
1123 * <blockquote><pre>{@code
1124 s.writeObject(this.returnType());
1125 s.writeObject(this.parameterArray());
1126 * }</pre></blockquote>
1127 * <p>
1128 * The deserialized field values are checked as if they were
1129 * provided to the factory method {@link #methodType(Class,Class[]) methodType}.
1130 * For example, null values, or {@code void} parameter types,
1131 * will lead to exceptions during deserialization.
1132 * @param s the stream to write the object to
1133 * @throws java.io.IOException if there is a problem writing the object
1134 */
1135 private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
1136 s.defaultWriteObject(); // requires serialPersistentFields to be an empty array
1137 s.writeObject(returnType());
1138 s.writeObject(parameterArray());
1139 }
1140
1141 /**
1142 * Reconstitute the {@code MethodType} instance from a stream (that is,
1143 * deserialize it).
1144 * This instance is a scratch object with bogus final fields.
1145 * It provides the parameters to the factory method called by
1146 * {@link #readResolve readResolve}.
1147 * After that call it is discarded.
1148 * @param s the stream to read the object from
1149 * @throws java.io.IOException if there is a problem reading the object
1150 * @throws ClassNotFoundException if one of the component classes cannot be resolved
1151 * @see #MethodType()
1152 * @see #readResolve
1153 * @see #writeObject
1154 */
1155 private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
1156 s.defaultReadObject(); // requires serialPersistentFields to be an empty array
1157
1158 Class<?> returnType = (Class<?>) s.readObject();
1159 Class<?>[] parameterArray = (Class<?>[]) s.readObject();
1160
1161 // Probably this object will never escape, but let's check
1162 // the field values now, just to be sure.
1163 checkRtype(returnType);
1164 checkPtypes(parameterArray);
1165
1166 parameterArray = parameterArray.clone(); // make sure it is unshared
1167 MethodType_init(returnType, parameterArray);
1168 }
1169
1170 /**
1171 * For serialization only.
1172 * Sets the final fields to null, pending {@code Unsafe.putObject}.
1173 */
1174 private MethodType() {
1175 this.rtype = null;
1176 this.ptypes = null;
1177 }
1178 private void MethodType_init(Class<?> rtype, Class<?>[] ptypes) {
1179 // In order to communicate these values to readResolve, we must
1180 // store them into the implementation-specific final fields.
1181 checkRtype(rtype);
1182 checkPtypes(ptypes);
1183 UNSAFE.putObject(this, rtypeOffset, rtype);
1184 UNSAFE.putObject(this, ptypesOffset, ptypes);
1185 }
1186
1187 // Support for resetting final fields while deserializing
1188 private static final long rtypeOffset, ptypesOffset;
1189 static {
1190 try {
1191 rtypeOffset = UNSAFE.objectFieldOffset
1192 (MethodType.class.getDeclaredField("rtype"));
1193 ptypesOffset = UNSAFE.objectFieldOffset
1194 (MethodType.class.getDeclaredField("ptypes"));
1195 } catch (Exception ex) {
1196 throw new Error(ex);
1197 }
1198 }
1199
1200 /**
1201 * Resolves and initializes a {@code MethodType} object
1202 * after serialization.
1203 * @return the fully initialized {@code MethodType} object
1204 */
1205 private Object readResolve() {
1206 // Do not use a trusted path for deserialization:
1207 //return makeImpl(rtype, ptypes, true);
1208 // Verify all operands, and make sure ptypes is unshared:
1209 return methodType(rtype, ptypes);
1210 }
1211
1212 /**
1213 * Simple implementation of weak concurrent intern set.
1214 *
1215 * @param <T> interned type
1216 */
1217 private static class ConcurrentWeakInternSet<T> {
1218
1219 private final ConcurrentMap<WeakEntry<T>, WeakEntry<T>> map;
1220 private final ReferenceQueue<T> stale;
1221
1222 public ConcurrentWeakInternSet() {
1223 this.map = new ConcurrentHashMap<>();
1224 this.stale = new ReferenceQueue<>();
1225 }
1226
1227 /**
1228 * Get the existing interned element.
1229 * This method returns null if no element is interned.
1230 *
1231 * @param elem element to look up
1232 * @return the interned element
1233 */
1234 public T get(T elem) {
1235 if (elem == null) throw new NullPointerException();
1236 expungeStaleElements();
1237
1238 WeakEntry<T> value = map.get(new WeakEntry<>(elem));
1239 if (value != null) {
1240 T res = value.get();
1241 if (res != null) {
1242 return res;
1243 }
1244 }
1245 return null;
1246 }
1247
1248 /**
1249 * Interns the element.
1250 * Always returns non-null element, matching the one in the intern set.
1251 * Under the race against another add(), it can return <i>different</i>
1252 * element, if another thread beats us to interning it.
1253 *
1254 * @param elem element to add
1255 * @return element that was actually added
1256 */
1257 public T add(T elem) {
1258 if (elem == null) throw new NullPointerException();
1259
1260 // Playing double race here, and so spinloop is required.
1261 // First race is with two concurrent updaters.
1262 // Second race is with GC purging weak ref under our feet.
1263 // Hopefully, we almost always end up with a single pass.
1264 T interned;
1265 WeakEntry<T> e = new WeakEntry<>(elem, stale);
1266 do {
1267 expungeStaleElements();
1268 WeakEntry<T> exist = map.putIfAbsent(e, e);
1269 interned = (exist == null) ? elem : exist.get();
1270 } while (interned == null);
1271 return interned;
1272 }
1273
1274 private void expungeStaleElements() {
1275 Reference<? extends T> reference;
1276 while ((reference = stale.poll()) != null) {
1277 map.remove(reference);
1278 }
1279 }
1280
1281 private static class WeakEntry<T> extends WeakReference<T> {
1282
1283 public final int hashcode;
1284
1285 public WeakEntry(T key, ReferenceQueue<T> queue) {
1286 super(key, queue);
1287 hashcode = key.hashCode();
1288 }
1289
1290 public WeakEntry(T key) {
1291 super(key);
1292 hashcode = key.hashCode();
1293 }
1294
1295 @Override
1296 public boolean equals(Object obj) {
1297 if (obj instanceof WeakEntry) {
1298 Object that = ((WeakEntry) obj).get();
1299 Object mine = get();
1300 return (that == null || mine == null) ? (this == obj) : mine.equals(that);
1301 }
1302 return false;
1303 }
1304
1305 @Override
1306 public int hashCode() {
1307 return hashcode;
1308 }
1309
1310 }
1311 }
1312
1313 }