1 /*
2 * Copyright (c) 2008, 2012, 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.concurrent.ConcurrentMap;
36 import java.util.concurrent.ConcurrentHashMap;
37 import sun.invoke.util.BytecodeDescriptor;
38 import static java.lang.invoke.MethodHandleStatics.*;
39 import sun.invoke.util.VerifyType;
40
41 /**
42 * A method type represents the arguments and return type accepted and
43 * returned by a method handle, or the arguments and return type passed
44 * and expected by a method handle caller. Method types must be properly
45 * matched between a method handle and all its callers,
46 * and the JVM's operations enforce this matching at, specifically
47 * during calls to {@link MethodHandle#invokeExact MethodHandle.invokeExact}
48 * and {@link MethodHandle#invoke MethodHandle.invoke}, and during execution
49 * of {@code invokedynamic} instructions.
50 * <p>
51 * The structure is a return type accompanied by any number of parameter types.
52 * The types (primitive, {@code void}, and reference) are represented by {@link Class} objects.
53 * (For ease of exposition, we treat {@code void} as if it were a type.
54 * In fact, it denotes the absence of a return type.)
55 * <p>
56 * All instances of {@code MethodType} are immutable.
57 * Two instances are completely interchangeable if they compare equal.
58 * Equality depends on pairwise correspondence of the return and parameter types and on nothing else.
59 * <p>
60 * This type can be created only by factory methods.
61 * All factory methods may cache values, though caching is not guaranteed.
62 * Some factory methods are static, while others are virtual methods which
63 * modify precursor method types, e.g., by changing a selected parameter.
64 * <p>
65 * Factory methods which operate on groups of parameter types
66 * are systematically presented in two versions, so that both Java arrays and
67 * Java lists can be used to work with groups of parameter types.
68 * The query methods {@code parameterArray} and {@code parameterList}
69 * also provide a choice between arrays and lists.
70 * <p>
71 * {@code MethodType} objects are sometimes derived from bytecode instructions
72 * such as {@code invokedynamic}, specifically from the type descriptor strings associated
73 * with the instructions in a class file's constant pool.
74 * <p>
75 * Like classes and strings, method types can also be represented directly
76 * in a class file's constant pool as constants.
77 * A method type may be loaded by an {@code ldc} instruction which refers
78 * to a suitable {@code CONSTANT_MethodType} constant pool entry.
79 * The entry refers to a {@code CONSTANT_Utf8} spelling for the descriptor string.
80 * For more details, see the <a href="package-summary.html#mtcon">package summary</a>.
81 * <p>
82 * When the JVM materializes a {@code MethodType} from a descriptor string,
83 * all classes named in the descriptor must be accessible, and will be loaded.
84 * (But the classes need not be initialized, as is the case with a {@code CONSTANT_Class}.)
85 * This loading may occur at any time before the {@code MethodType} object is first derived.
86 * @author John Rose, JSR 292 EG
87 */
88 public final
89 class MethodType implements java.io.Serializable {
90 private static final long serialVersionUID = 292L; // {rtype, {ptype...}}
91
92 // The rtype and ptypes fields define the structural identity of the method type:
93 private final Class<?> rtype;
94 private final Class<?>[] ptypes;
95
96 // The remaining fields are caches of various sorts:
97 private MethodTypeForm form; // erased form, plus cached data about primitives
98 private MethodType wrapAlt; // alternative wrapped/unwrapped version
99 private Invokers invokers; // cache of handy higher-order adapters
100
101 /**
102 * Check the given parameters for validity and store them into the final fields.
103 */
104 private MethodType(Class<?> rtype, Class<?>[] ptypes) {
105 checkRtype(rtype);
106 checkPtypes(ptypes);
107 this.rtype = rtype;
108 this.ptypes = ptypes;
109 }
110
111 /*trusted*/ MethodTypeForm form() { return form; }
112 /*trusted*/ Class<?> rtype() { return rtype; }
113 /*trusted*/ Class<?>[] ptypes() { return ptypes; }
114
115 void setForm(MethodTypeForm f) { form = f; }
116
117 /** This number, mandated by the JVM spec as 255,
118 * is the maximum number of <em>slots</em>
119 * that any Java method can receive in its argument list.
120 * It limits both JVM signatures and method type objects.
121 * The longest possible invocation will look like
122 * {@code staticMethod(arg1, arg2, ..., arg255)} or
123 * {@code x.virtualMethod(arg1, arg2, ..., arg254)}.
124 */
125 /*non-public*/ static final int MAX_JVM_ARITY = 255; // this is mandated by the JVM spec.
126
127 /** This number is the maximum arity of a method handle, 254.
128 * It is derived from the absolute JVM-imposed arity by subtracting one,
129 * which is the slot occupied by the method handle itself at the
130 * beginning of the argument list used to invoke the method handle.
131 * The longest possible invocation will look like
132 * {@code mh.invoke(arg1, arg2, ..., arg254)}.
133 */
134 // Issue: Should we allow MH.invokeWithArguments to go to the full 255?
135 /*non-public*/ static final int MAX_MH_ARITY = MAX_JVM_ARITY-1; // deduct one for mh receiver
136
137 /** This number is the maximum arity of a method handle invoker, 253.
138 * It is derived from the absolute JVM-imposed arity by subtracting two,
139 * which are the slots occupied by invoke method handle, and the the
140 * target method handle, which are both at the beginning of the argument
141 * list used to invoke the target method handle.
142 * The longest possible invocation will look like
143 * {@code invokermh.invoke(targetmh, arg1, arg2, ..., arg253)}.
144 */
145 /*non-public*/ static final int MAX_MH_INVOKER_ARITY = MAX_MH_ARITY-1; // deduct one more for invoker
146
147 private static void checkRtype(Class<?> rtype) {
148 rtype.equals(rtype); // null check
149 }
150 private static int checkPtype(Class<?> ptype) {
151 ptype.getClass(); //NPE
152 if (ptype == void.class)
153 throw newIllegalArgumentException("parameter type cannot be void");
154 if (ptype == double.class || ptype == long.class) return 1;
155 return 0;
156 }
157 /** Return number of extra slots (count of long/double args). */
158 private static int checkPtypes(Class<?>[] ptypes) {
159 int slots = 0;
160 for (Class<?> ptype : ptypes) {
161 slots += checkPtype(ptype);
162 }
163 checkSlotCount(ptypes.length + slots);
164 return slots;
165 }
166 static void checkSlotCount(int count) {
167 assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0);
168 // MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work:
169 if ((count & MAX_JVM_ARITY) != count)
170 throw newIllegalArgumentException("bad parameter count "+count);
171 }
172 private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) {
173 if (num instanceof Integer) num = "bad index: "+num;
174 return new IndexOutOfBoundsException(num.toString());
175 }
176
177 static final ConcurrentWeakInternSet<MethodType> internTable = new ConcurrentWeakInternSet<>();
178
179 static final Class<?>[] NO_PTYPES = {};
180
181 /**
182 * Finds or creates an instance of the given method type.
183 * @param rtype the return type
184 * @param ptypes the parameter types
185 * @return a method type with the given components
186 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
187 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
188 */
189 public static
190 MethodType methodType(Class<?> rtype, Class<?>[] ptypes) {
191 return makeImpl(rtype, ptypes, false);
192 }
193
194 /**
195 * Finds or creates a method type with the given components.
196 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
197 * @param rtype the return type
198 * @param ptypes the parameter types
199 * @return a method type with the given components
200 * @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
201 * @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
202 */
203 public static
204 MethodType methodType(Class<?> rtype, List<Class<?>> ptypes) {
205 boolean notrust = false; // random List impl. could return evil ptypes array
206 return makeImpl(rtype, listToArray(ptypes), notrust);
207 }
208
209 private static Class<?>[] listToArray(List<Class<?>> ptypes) {
210 // sanity check the size before the toArray call, since size might be huge
211 checkSlotCount(ptypes.size());
212 return ptypes.toArray(NO_PTYPES);
213 }
214
215 /**
216 * Finds or creates a method type with the given components.
217 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
218 * The leading parameter type is prepended to the remaining array.
219 * @param rtype the return type
220 * @param ptype0 the first parameter type
221 * @param ptypes the remaining parameter types
222 * @return a method type with the given components
223 * @throws NullPointerException if {@code rtype} or {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is null
224 * @throws IllegalArgumentException if {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is {@code void.class}
225 */
226 public static
227 MethodType methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes) {
228 Class<?>[] ptypes1 = new Class<?>[1+ptypes.length];
229 ptypes1[0] = ptype0;
230 System.arraycopy(ptypes, 0, ptypes1, 1, ptypes.length);
231 return makeImpl(rtype, ptypes1, true);
232 }
233
234 /**
235 * Finds or creates a method type with the given components.
236 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
237 * The resulting method has no parameter types.
238 * @param rtype the return type
239 * @return a method type with the given return value
240 * @throws NullPointerException if {@code rtype} is null
241 */
242 public static
243 MethodType methodType(Class<?> rtype) {
244 return makeImpl(rtype, NO_PTYPES, true);
245 }
246
247 /**
248 * Finds or creates a method type with the given components.
249 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
250 * The resulting method has the single given parameter type.
251 * @param rtype the return type
252 * @param ptype0 the parameter type
253 * @return a method type with the given return value and parameter type
254 * @throws NullPointerException if {@code rtype} or {@code ptype0} is null
255 * @throws IllegalArgumentException if {@code ptype0} is {@code void.class}
256 */
257 public static
258 MethodType methodType(Class<?> rtype, Class<?> ptype0) {
259 return makeImpl(rtype, new Class<?>[]{ ptype0 }, true);
260 }
261
262 /**
263 * Finds or creates a method type with the given components.
264 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
265 * The resulting method has the same parameter types as {@code ptypes},
266 * and the specified return type.
267 * @param rtype the return type
268 * @param ptypes the method type which supplies the parameter types
269 * @return a method type with the given components
270 * @throws NullPointerException if {@code rtype} or {@code ptypes} is null
271 */
272 public static
273 MethodType methodType(Class<?> rtype, MethodType ptypes) {
274 return makeImpl(rtype, ptypes.ptypes, true);
275 }
276
277 /**
278 * Sole factory method to find or create an interned method type.
279 * @param rtype desired return type
280 * @param ptypes desired parameter types
281 * @param trusted whether the ptypes can be used without cloning
282 * @return the unique method type of the desired structure
283 */
284 /*trusted*/ static
285 MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {
286 if (ptypes.length == 0) {
287 ptypes = NO_PTYPES; trusted = true;
288 }
289 MethodType mt1 = new MethodType(rtype, ptypes);
290 MethodType mt0 = internTable.get(mt1);
291 if (mt0 != null)
292 return mt0;
293 if (!trusted)
294 // defensively copy the array passed in by the user
295 mt1 = new MethodType(rtype, ptypes.clone());
296 // promote the object to the Real Thing, and reprobe
297 MethodTypeForm form = MethodTypeForm.findForm(mt1);
298 mt1.form = form;
299 return internTable.add(mt1);
300 }
301 private static final MethodType[] objectOnlyTypes = new MethodType[20];
302
303 /**
304 * Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array.
305 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
306 * All parameters and the return type will be {@code Object},
307 * except the final array parameter if any, which will be {@code Object[]}.
308 * @param objectArgCount number of parameters (excluding the final array parameter if any)
309 * @param finalArray whether there will be a trailing array parameter, of type {@code Object[]}
310 * @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments
311 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true)
312 * @see #genericMethodType(int)
313 */
314 public static
315 MethodType genericMethodType(int objectArgCount, boolean finalArray) {
316 MethodType mt;
317 checkSlotCount(objectArgCount);
318 int ivarargs = (!finalArray ? 0 : 1);
319 int ootIndex = objectArgCount*2 + ivarargs;
320 if (ootIndex < objectOnlyTypes.length) {
321 mt = objectOnlyTypes[ootIndex];
322 if (mt != null) return mt;
323 }
324 Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs];
325 Arrays.fill(ptypes, Object.class);
326 if (ivarargs != 0) ptypes[objectArgCount] = Object[].class;
327 mt = makeImpl(Object.class, ptypes, true);
328 if (ootIndex < objectOnlyTypes.length) {
329 objectOnlyTypes[ootIndex] = mt; // cache it here also!
330 }
331 return mt;
332 }
333
334 /**
335 * Finds or creates a method type whose components are all {@code Object}.
336 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
337 * All parameters and the return type will be Object.
338 * @param objectArgCount number of parameters
339 * @return a generally applicable method type, for all calls of the given argument count
340 * @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255
341 * @see #genericMethodType(int, boolean)
342 */
343 public static
344 MethodType genericMethodType(int objectArgCount) {
345 return genericMethodType(objectArgCount, false);
346 }
347
348 /**
349 * Finds or creates a method type with a single different parameter type.
350 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
351 * @param num the index (zero-based) of the parameter type to change
352 * @param nptype a new parameter type to replace the old one with
353 * @return the same type, except with the selected parameter changed
354 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
355 * @throws IllegalArgumentException if {@code nptype} is {@code void.class}
356 * @throws NullPointerException if {@code nptype} is null
357 */
358 public MethodType changeParameterType(int num, Class<?> nptype) {
359 if (parameterType(num) == nptype) return this;
360 checkPtype(nptype);
361 Class<?>[] nptypes = ptypes.clone();
362 nptypes[num] = nptype;
363 return makeImpl(rtype, nptypes, true);
364 }
365
366 /**
367 * Finds or creates a method type with additional parameter types.
368 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
369 * @param num the position (zero-based) of the inserted parameter type(s)
370 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
371 * @return the same type, except with the selected parameter(s) inserted
372 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
373 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
374 * or if the resulting method type would have more than 255 parameter slots
375 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
376 */
377 public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) {
378 int len = ptypes.length;
379 if (num < 0 || num > len)
380 throw newIndexOutOfBoundsException(num);
381 int ins = checkPtypes(ptypesToInsert);
382 checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins);
383 int ilen = ptypesToInsert.length;
384 if (ilen == 0) return this;
385 Class<?>[] nptypes = Arrays.copyOfRange(ptypes, 0, len+ilen);
386 System.arraycopy(nptypes, num, nptypes, num+ilen, len-num);
387 System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen);
388 return makeImpl(rtype, nptypes, true);
389 }
390
391 /**
392 * Finds or creates a method type with additional parameter types.
393 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
394 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
395 * @return the same type, except with the selected parameter(s) appended
396 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
397 * or if the resulting method type would have more than 255 parameter slots
398 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
399 */
400 public MethodType appendParameterTypes(Class<?>... ptypesToInsert) {
401 return insertParameterTypes(parameterCount(), ptypesToInsert);
402 }
403
404 /**
405 * Finds or creates a method type with additional parameter types.
406 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
407 * @param num the position (zero-based) of the inserted parameter type(s)
408 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
409 * @return the same type, except with the selected parameter(s) inserted
410 * @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
411 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
412 * or if the resulting method type would have more than 255 parameter slots
413 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
414 */
415 public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) {
416 return insertParameterTypes(num, listToArray(ptypesToInsert));
417 }
418
419 /**
420 * Finds or creates a method type with additional parameter types.
421 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
422 * @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
423 * @return the same type, except with the selected parameter(s) appended
424 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
425 * or if the resulting method type would have more than 255 parameter slots
426 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
427 */
428 public MethodType appendParameterTypes(List<Class<?>> ptypesToInsert) {
429 return insertParameterTypes(parameterCount(), ptypesToInsert);
430 }
431
432 /**
433 * Finds or creates a method type with modified parameter types.
434 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
435 * @param start the position (zero-based) of the first replaced parameter type(s)
436 * @param end the position (zero-based) after the last replaced parameter type(s)
437 * @param ptypesToInsert zero or more new parameter types to insert into the parameter list
438 * @return the same type, except with the selected parameter(s) replaced
439 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
440 * or if {@code end} is negative or greater than {@code parameterCount()}
441 * or if {@code start} is greater than {@code end}
442 * @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
443 * or if the resulting method type would have more than 255 parameter slots
444 * @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
445 */
446 /*non-public*/ MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) {
447 if (start == end)
448 return insertParameterTypes(start, ptypesToInsert);
449 int len = ptypes.length;
450 if (!(0 <= start && start <= end && end <= len))
451 throw newIndexOutOfBoundsException("start="+start+" end="+end);
452 int ilen = ptypesToInsert.length;
453 if (ilen == 0)
454 return dropParameterTypes(start, end);
455 return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert);
456 }
457
458 /**
459 * Finds or creates a method type with some parameter types omitted.
460 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
461 * @param start the index (zero-based) of the first parameter type to remove
462 * @param end the index (greater than {@code start}) of the first parameter type after not to remove
463 * @return the same type, except with the selected parameter(s) removed
464 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
465 * or if {@code end} is negative or greater than {@code parameterCount()}
466 * or if {@code start} is greater than {@code end}
467 */
468 public MethodType dropParameterTypes(int start, int end) {
469 int len = ptypes.length;
470 if (!(0 <= start && start <= end && end <= len))
471 throw newIndexOutOfBoundsException("start="+start+" end="+end);
472 if (start == end) return this;
473 Class<?>[] nptypes;
474 if (start == 0) {
475 if (end == len) {
476 // drop all parameters
477 nptypes = NO_PTYPES;
478 } else {
479 // drop initial parameter(s)
480 nptypes = Arrays.copyOfRange(ptypes, end, len);
481 }
482 } else {
483 if (end == len) {
484 // drop trailing parameter(s)
485 nptypes = Arrays.copyOfRange(ptypes, 0, start);
486 } else {
487 int tail = len - end;
488 nptypes = Arrays.copyOfRange(ptypes, 0, start + tail);
489 System.arraycopy(ptypes, end, nptypes, start, tail);
490 }
491 }
492 return makeImpl(rtype, nptypes, true);
493 }
494
495 /**
496 * Finds or creates a method type with a different return type.
497 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
498 * @param nrtype a return parameter type to replace the old one with
499 * @return the same type, except with the return type change
500 * @throws NullPointerException if {@code nrtype} is null
501 */
502 public MethodType changeReturnType(Class<?> nrtype) {
503 if (returnType() == nrtype) return this;
504 return makeImpl(nrtype, ptypes, true);
505 }
506
507 /**
508 * Reports if this type contains a primitive argument or return value.
509 * The return type {@code void} counts as a primitive.
510 * @return true if any of the types are primitives
511 */
512 public boolean hasPrimitives() {
513 return form.hasPrimitives();
514 }
515
516 /**
517 * Reports if this type contains a wrapper argument or return value.
518 * Wrappers are types which box primitive values, such as {@link Integer}.
519 * The reference type {@code java.lang.Void} counts as a wrapper,
520 * if it occurs as a return type.
521 * @return true if any of the types are wrappers
522 */
523 public boolean hasWrappers() {
524 return unwrap() != this;
525 }
526
527 /**
528 * Erases all reference types to {@code Object}.
529 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
530 * All primitive types (including {@code void}) will remain unchanged.
531 * @return a version of the original type with all reference types replaced
532 */
533 public MethodType erase() {
534 return form.erasedType();
535 }
536
537 /**
538 * Erases all reference types to {@code Object}, and all subword types to {@code int}.
539 * This is the reduced type polymorphism used by private methods
540 * such as {@link MethodHandle#invokeBasic invokeBasic}.
541 * @return a version of the original type with all reference and subword types replaced
542 */
543 /*non-public*/ MethodType basicType() {
544 return form.basicType();
545 }
546
547 /**
548 * @return a version of the original type with MethodHandle prepended as the first argument
549 */
550 /*non-public*/ MethodType invokerType() {
551 return insertParameterTypes(0, MethodHandle.class);
552 }
553
554 /**
555 * Converts all types, both reference and primitive, to {@code Object}.
556 * Convenience method for {@link #genericMethodType(int) genericMethodType}.
557 * The expression {@code type.wrap().erase()} produces the same value
558 * as {@code type.generic()}.
559 * @return a version of the original type with all types replaced
560 */
561 public MethodType generic() {
562 return genericMethodType(parameterCount());
563 }
564
565 /**
566 * Converts all primitive types to their corresponding wrapper types.
567 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
568 * All reference types (including wrapper types) will remain unchanged.
569 * A {@code void} return type is changed to the type {@code java.lang.Void}.
570 * The expression {@code type.wrap().erase()} produces the same value
571 * as {@code type.generic()}.
572 * @return a version of the original type with all primitive types replaced
573 */
574 public MethodType wrap() {
575 return hasPrimitives() ? wrapWithPrims(this) : this;
576 }
577
578 /**
579 * Converts all wrapper types to their corresponding primitive types.
580 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
581 * All primitive types (including {@code void}) will remain unchanged.
582 * A return type of {@code java.lang.Void} is changed to {@code void}.
583 * @return a version of the original type with all wrapper types replaced
584 */
585 public MethodType unwrap() {
586 MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this);
587 return unwrapWithNoPrims(noprims);
588 }
589
590 private static MethodType wrapWithPrims(MethodType pt) {
591 assert(pt.hasPrimitives());
592 MethodType wt = pt.wrapAlt;
593 if (wt == null) {
594 // fill in lazily
595 wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP, MethodTypeForm.WRAP);
596 assert(wt != null);
597 pt.wrapAlt = wt;
598 }
599 return wt;
600 }
601
602 private static MethodType unwrapWithNoPrims(MethodType wt) {
603 assert(!wt.hasPrimitives());
604 MethodType uwt = wt.wrapAlt;
605 if (uwt == null) {
606 // fill in lazily
607 uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP, MethodTypeForm.UNWRAP);
608 if (uwt == null)
609 uwt = wt; // type has no wrappers or prims at all
610 wt.wrapAlt = uwt;
611 }
612 return uwt;
613 }
614
615 /**
616 * Returns the parameter type at the specified index, within this method type.
617 * @param num the index (zero-based) of the desired parameter type
618 * @return the selected parameter type
619 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
620 */
621 public Class<?> parameterType(int num) {
622 return ptypes[num];
623 }
624 /**
625 * Returns the number of parameter types in this method type.
626 * @return the number of parameter types
627 */
628 public int parameterCount() {
629 return ptypes.length;
630 }
631 /**
632 * Returns the return type of this method type.
633 * @return the return type
634 */
635 public Class<?> returnType() {
636 return rtype;
637 }
638
639 /**
640 * Presents the parameter types as a list (a convenience method).
641 * The list will be immutable.
642 * @return the parameter types (as an immutable list)
643 */
644 public List<Class<?>> parameterList() {
645 return Collections.unmodifiableList(Arrays.asList(ptypes));
646 }
647
648 /*non-public*/ Class<?> lastParameterType() {
649 int len = ptypes.length;
650 return len == 0 ? void.class : ptypes[len-1];
651 }
652
653 /**
654 * Presents the parameter types as an array (a convenience method).
655 * Changes to the array will not result in changes to the type.
656 * @return the parameter types (as a fresh copy if necessary)
657 */
658 public Class<?>[] parameterArray() {
659 return ptypes.clone();
660 }
661
662 /**
663 * Compares the specified object with this type for equality.
664 * That is, it returns <tt>true</tt> if and only if the specified object
665 * is also a method type with exactly the same parameters and return type.
666 * @param x object to compare
667 * @see Object#equals(Object)
668 */
669 @Override
670 public boolean equals(Object x) {
671 return this == x || x instanceof MethodType && equals((MethodType)x);
672 }
673
674 private boolean equals(MethodType that) {
675 return this.rtype == that.rtype
676 && Arrays.equals(this.ptypes, that.ptypes);
677 }
678
679 /**
680 * Returns the hash code value for this method type.
681 * It is defined to be the same as the hashcode of a List
682 * whose elements are the return type followed by the
683 * parameter types.
684 * @return the hash code value for this method type
685 * @see Object#hashCode()
686 * @see #equals(Object)
687 * @see List#hashCode()
688 */
689 @Override
690 public int hashCode() {
691 int hashCode = 31 + rtype.hashCode();
692 for (Class<?> ptype : ptypes)
693 hashCode = 31*hashCode + ptype.hashCode();
694 return hashCode;
695 }
696
697 /**
698 * Returns a string representation of the method type,
699 * of the form {@code "(PT0,PT1...)RT"}.
700 * The string representation of a method type is a
701 * parenthesis enclosed, comma separated list of type names,
702 * followed immediately by the return type.
703 * <p>
704 * Each type is represented by its
705 * {@link java.lang.Class#getSimpleName simple name}.
706 */
707 @Override
708 public String toString() {
709 StringBuilder sb = new StringBuilder();
710 sb.append("(");
711 for (int i = 0; i < ptypes.length; i++) {
712 if (i > 0) sb.append(",");
713 sb.append(ptypes[i].getSimpleName());
714 }
715 sb.append(")");
716 sb.append(rtype.getSimpleName());
717 return sb.toString();
718 }
719
720
721 /*non-public*/
722 boolean isViewableAs(MethodType newType) {
723 if (!VerifyType.isNullConversion(returnType(), newType.returnType()))
724 return false;
725 int argc = parameterCount();
726 if (argc != newType.parameterCount())
727 return false;
728 for (int i = 0; i < argc; i++) {
729 if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i)))
730 return false;
731 }
732 return true;
733 }
734 /*non-public*/
735 boolean isCastableTo(MethodType newType) {
736 int argc = parameterCount();
737 if (argc != newType.parameterCount())
738 return false;
739 return true;
740 }
741 /*non-public*/
742 boolean isConvertibleTo(MethodType newType) {
743 if (!canConvert(returnType(), newType.returnType()))
744 return false;
745 int argc = parameterCount();
746 if (argc != newType.parameterCount())
747 return false;
748 for (int i = 0; i < argc; i++) {
749 if (!canConvert(newType.parameterType(i), parameterType(i)))
750 return false;
751 }
752 return true;
753 }
754 /*non-public*/
755 static boolean canConvert(Class<?> src, Class<?> dst) {
756 // short-circuit a few cases:
757 if (src == dst || dst == Object.class) return true;
758 // the remainder of this logic is documented in MethodHandle.asType
759 if (src.isPrimitive()) {
760 // can force void to an explicit null, a la reflect.Method.invoke
761 // can also force void to a primitive zero, by analogy
762 if (src == void.class) return true; //or !dst.isPrimitive()?
763 Wrapper sw = Wrapper.forPrimitiveType(src);
764 if (dst.isPrimitive()) {
765 // P->P must widen
766 return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw);
767 } else {
768 // P->R must box and widen
769 return dst.isAssignableFrom(sw.wrapperType());
770 }
771 } else if (dst.isPrimitive()) {
772 // any value can be dropped
773 if (dst == void.class) return true;
774 Wrapper dw = Wrapper.forPrimitiveType(dst);
775 // R->P must be able to unbox (from a dynamically chosen type) and widen
776 // For example:
777 // Byte/Number/Comparable/Object -> dw:Byte -> byte.
778 // Character/Comparable/Object -> dw:Character -> char
779 // Boolean/Comparable/Object -> dw:Boolean -> boolean
780 // This means that dw must be cast-compatible with src.
781 if (src.isAssignableFrom(dw.wrapperType())) {
782 return true;
783 }
784 // The above does not work if the source reference is strongly typed
785 // to a wrapper whose primitive must be widened. For example:
786 // Byte -> unbox:byte -> short/int/long/float/double
787 // Character -> unbox:char -> int/long/float/double
788 if (Wrapper.isWrapperType(src) &&
789 dw.isConvertibleFrom(Wrapper.forWrapperType(src))) {
790 // can unbox from src and then widen to dst
791 return true;
792 }
793 // We have already covered cases which arise due to runtime unboxing
794 // of a reference type which covers several wrapper types:
795 // Object -> cast:Integer -> unbox:int -> long/float/double
796 // Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double
797 // An marginal case is Number -> dw:Character -> char, which would be OK if there were a
798 // subclass of Number which wraps a value that can convert to char.
799 // Since there is none, we don't need an extra check here to cover char or boolean.
800 return false;
801 } else {
802 // R->R always works, since null is always valid dynamically
803 return true;
804 }
805 }
806
807 /// Queries which have to do with the bytecode architecture
808
809 /** Reports the number of JVM stack slots required to invoke a method
810 * of this type. Note that (for historical reasons) the JVM requires
811 * a second stack slot to pass long and double arguments.
812 * So this method returns {@link #parameterCount() parameterCount} plus the
813 * number of long and double parameters (if any).
814 * <p>
815 * This method is included for the benfit of applications that must
816 * generate bytecodes that process method handles and invokedynamic.
817 * @return the number of JVM stack slots for this type's parameters
818 */
819 /*non-public*/ int parameterSlotCount() {
820 return form.parameterSlotCount();
821 }
822
823 /*non-public*/ Invokers invokers() {
824 Invokers inv = invokers;
825 if (inv != null) return inv;
826 invokers = inv = new Invokers(this);
827 return inv;
828 }
829
830 /** Reports the number of JVM stack slots which carry all parameters including and after
831 * the given position, which must be in the range of 0 to
832 * {@code parameterCount} inclusive. Successive parameters are
833 * more shallowly stacked, and parameters are indexed in the bytecodes
834 * according to their trailing edge. Thus, to obtain the depth
835 * in the outgoing call stack of parameter {@code N}, obtain
836 * the {@code parameterSlotDepth} of its trailing edge
837 * at position {@code N+1}.
838 * <p>
839 * Parameters of type {@code long} and {@code double} occupy
840 * two stack slots (for historical reasons) and all others occupy one.
841 * Therefore, the number returned is the number of arguments
842 * <em>including</em> and <em>after</em> the given parameter,
843 * <em>plus</em> the number of long or double arguments
844 * at or after after the argument for the given parameter.
845 * <p>
846 * This method is included for the benfit of applications that must
847 * generate bytecodes that process method handles and invokedynamic.
848 * @param num an index (zero-based, inclusive) within the parameter types
849 * @return the index of the (shallowest) JVM stack slot transmitting the
850 * given parameter
851 * @throws IllegalArgumentException if {@code num} is negative or greater than {@code parameterCount()}
852 */
853 /*non-public*/ int parameterSlotDepth(int num) {
854 if (num < 0 || num > ptypes.length)
855 parameterType(num); // force a range check
856 return form.parameterToArgSlot(num-1);
857 }
858
859 /** Reports the number of JVM stack slots required to receive a return value
860 * from a method of this type.
861 * If the {@link #returnType() return type} is void, it will be zero,
862 * else if the return type is long or double, it will be two, else one.
863 * <p>
864 * This method is included for the benfit of applications that must
865 * generate bytecodes that process method handles and invokedynamic.
866 * @return the number of JVM stack slots (0, 1, or 2) for this type's return value
867 * Will be removed for PFD.
868 */
869 /*non-public*/ int returnSlotCount() {
870 return form.returnSlotCount();
871 }
872
873 /**
874 * Finds or creates an instance of a method type, given the spelling of its bytecode descriptor.
875 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
876 * Any class or interface name embedded in the descriptor string
877 * will be resolved by calling {@link ClassLoader#loadClass(java.lang.String)}
878 * on the given loader (or if it is null, on the system class loader).
879 * <p>
880 * Note that it is possible to encounter method types which cannot be
881 * constructed by this method, because their component types are
882 * not all reachable from a common class loader.
883 * <p>
884 * This method is included for the benfit of applications that must
885 * generate bytecodes that process method handles and {@code invokedynamic}.
886 * @param descriptor a bytecode-level type descriptor string "(T...)T"
887 * @param loader the class loader in which to look up the types
888 * @return a method type matching the bytecode-level type descriptor
889 * @throws NullPointerException if the string is null
890 * @throws IllegalArgumentException if the string is not well-formed
891 * @throws TypeNotPresentException if a named type cannot be found
892 */
893 public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader)
894 throws IllegalArgumentException, TypeNotPresentException
895 {
896 if (!descriptor.startsWith("(") || // also generates NPE if needed
897 descriptor.indexOf(')') < 0 ||
898 descriptor.indexOf('.') >= 0)
899 throw new IllegalArgumentException("not a method descriptor: "+descriptor);
900 List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader);
901 Class<?> rtype = types.remove(types.size() - 1);
902 checkSlotCount(types.size());
903 Class<?>[] ptypes = listToArray(types);
904 return makeImpl(rtype, ptypes, true);
905 }
906
907 /**
908 * Produces a bytecode descriptor representation of the method type.
909 * <p>
910 * Note that this is not a strict inverse of {@link #fromMethodDescriptorString fromMethodDescriptorString}.
911 * Two distinct classes which share a common name but have different class loaders
912 * will appear identical when viewed within descriptor strings.
913 * <p>
914 * This method is included for the benfit of applications that must
915 * generate bytecodes that process method handles and {@code invokedynamic}.
916 * {@link #fromMethodDescriptorString(java.lang.String, java.lang.ClassLoader) fromMethodDescriptorString},
917 * because the latter requires a suitable class loader argument.
918 * @return the bytecode type descriptor representation
919 */
920 public String toMethodDescriptorString() {
921 return BytecodeDescriptor.unparse(this);
922 }
923
924 /*non-public*/ static String toFieldDescriptorString(Class<?> cls) {
925 return BytecodeDescriptor.unparse(cls);
926 }
927
928 /// Serialization.
929
930 /**
931 * There are no serializable fields for {@code MethodType}.
932 */
933 private static final java.io.ObjectStreamField[] serialPersistentFields = { };
934
935 /**
936 * Save the {@code MethodType} instance to a stream.
937 *
938 * @serialData
939 * For portability, the serialized format does not refer to named fields.
940 * Instead, the return type and parameter type arrays are written directly
941 * from the {@code writeObject} method, using two calls to {@code s.writeObject}
942 * as follows:
943 * <blockquote><pre>
944 s.writeObject(this.returnType());
945 s.writeObject(this.parameterArray());
946 * </pre></blockquote>
947 * <p>
948 * The deserialized field values are checked as if they were
949 * provided to the factory method {@link #methodType(Class,Class[]) methodType}.
950 * For example, null values, or {@code void} parameter types,
951 * will lead to exceptions during deserialization.
952 * @param s the stream to write the object to
953 * @throws java.io.IOException if there is a problem writing the object
954 */
955 private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
956 s.defaultWriteObject(); // requires serialPersistentFields to be an empty array
957 s.writeObject(returnType());
958 s.writeObject(parameterArray());
959 }
960
961 /**
962 * Reconstitute the {@code MethodType} instance from a stream (that is,
963 * deserialize it).
964 * This instance is a scratch object with bogus final fields.
965 * It provides the parameters to the factory method called by
966 * {@link #readResolve readResolve}.
967 * After that call it is discarded.
968 * @param s the stream to read the object from
969 * @throws java.io.IOException if there is a problem reading the object
970 * @throws ClassNotFoundException if one of the component classes cannot be resolved
971 * @see #MethodType()
972 * @see #readResolve
973 * @see #writeObject
974 */
975 private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
976 s.defaultReadObject(); // requires serialPersistentFields to be an empty array
977
978 Class<?> returnType = (Class<?>) s.readObject();
979 Class<?>[] parameterArray = (Class<?>[]) s.readObject();
980
981 // Probably this object will never escape, but let's check
982 // the field values now, just to be sure.
983 checkRtype(returnType);
984 checkPtypes(parameterArray);
985
986 parameterArray = parameterArray.clone(); // make sure it is unshared
987 MethodType_init(returnType, parameterArray);
988 }
989
990 /**
991 * For serialization only.
992 * Sets the final fields to null, pending {@code Unsafe.putObject}.
993 */
994 private MethodType() {
995 this.rtype = null;
996 this.ptypes = null;
997 }
998 private void MethodType_init(Class<?> rtype, Class<?>[] ptypes) {
999 // In order to communicate these values to readResolve, we must
1000 // store them into the implementation-specific final fields.
1001 checkRtype(rtype);
1002 checkPtypes(ptypes);
1003 UNSAFE.putObject(this, rtypeOffset, rtype);
1004 UNSAFE.putObject(this, ptypesOffset, ptypes);
1005 }
1006
1007 // Support for resetting final fields while deserializing
1008 private static final long rtypeOffset, ptypesOffset;
1009 static {
1010 try {
1011 rtypeOffset = UNSAFE.objectFieldOffset
1012 (MethodType.class.getDeclaredField("rtype"));
1013 ptypesOffset = UNSAFE.objectFieldOffset
1014 (MethodType.class.getDeclaredField("ptypes"));
1015 } catch (Exception ex) {
1016 throw new Error(ex);
1017 }
1018 }
1019
1020 /**
1021 * Resolves and initializes a {@code MethodType} object
1022 * after serialization.
1023 * @return the fully initialized {@code MethodType} object
1024 */
1025 private Object readResolve() {
1026 // Do not use a trusted path for deserialization:
1027 //return makeImpl(rtype, ptypes, true);
1028 // Verify all operands, and make sure ptypes is unshared:
1029 return methodType(rtype, ptypes);
1030 }
1031
1032 /**
1033 * Simple implementation of weak concurrent intern set.
1034 *
1035 * @param <T> interned type
1036 */
1037 private static class ConcurrentWeakInternSet<T> {
1038
1039 private final ConcurrentMap<WeakEntry<T>, WeakEntry<T>> map;
1040 private final ReferenceQueue<T> stale;
1041
1042 public ConcurrentWeakInternSet() {
1043 this.map = new ConcurrentHashMap<>();
1044 this.stale = new ReferenceQueue<>();
1045 }
1046
1047 /**
1048 * Get the existing interned element.
1049 * This method returns null if no element is interned.
1050 *
1051 * @param elem element to look up
1052 * @return the interned element
1053 */
1054 public T get(T elem) {
1055 if (elem == null) throw new NullPointerException();
1056 expungeStaleElements();
1057
1058 WeakEntry<T> value = map.get(new WeakEntry<>(elem));
1059 if (value != null) {
1060 T res = value.get();
1061 if (res != null) {
1062 return res;
1063 }
1064 }
1065 return null;
1066 }
1067
1068 /**
1069 * Interns the element.
1070 * Always returns non-null element, matching the one in the intern set.
1071 * Under the race against another add(), it can return <i>different</i>
1072 * element, if another thread beats us to interning it.
1073 *
1074 * @param elem element to add
1075 * @return element that was actually added
1076 */
1077 public T add(T elem) {
1078 if (elem == null) throw new NullPointerException();
1079
1080 // Playing double race here, and so spinloop is required.
1081 // First race is with two concurrent updaters.
1082 // Second race is with GC purging weak ref under our feet.
1083 // Hopefully, we almost always end up with a single pass.
1084 T interned;
1085 WeakEntry<T> e = new WeakEntry<>(elem, stale);
1086 do {
1087 expungeStaleElements();
1088 WeakEntry<T> exist = map.putIfAbsent(e, e);
1089 interned = (exist == null) ? elem : exist.get();
1090 } while (interned == null);
1091 return interned;
1092 }
1093
1094 private void expungeStaleElements() {
1095 Reference<? extends T> reference;
1096 while ((reference = stale.poll()) != null) {
1097 map.remove(reference);
1098 }
1099 }
1100
1101 private static class WeakEntry<T> extends WeakReference<T> {
1102
1103 public final int hashcode;
1104
1105 public WeakEntry(T key, ReferenceQueue<T> queue) {
1106 super(key, queue);
1107 hashcode = key.hashCode();
1108 }
1109
1110 public WeakEntry(T key) {
1111 super(key);
1112 hashcode = key.hashCode();
1113 }
1114
1115 @Override
1116 public boolean equals(Object obj) {
1117 if (obj instanceof WeakEntry) {
1118 Object that = ((WeakEntry) obj).get();
1119 Object mine = get();
1120 return (that == null || mine == null) ? (this == obj) : mine.equals(that);
1121 }
1122 return false;
1123 }
1124
1125 @Override
1126 public int hashCode() {
1127 return hashcode;
1128 }
1129
1130 }
1131 }
1132
1133 }