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 /**
514 * Finds or creates a method type with some parameter types omitted.
515 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
516 * @param start the index (zero-based) of the first parameter type to remove
517 * @param end the index (greater than {@code start}) of the first parameter type after not to remove
518 * @return the same type, except with the selected parameter(s) removed
519 * @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
520 * or if {@code end} is negative or greater than {@code parameterCount()}
521 * or if {@code start} is greater than {@code end}
522 */
523 public MethodType dropParameterTypes(int start, int end) {
524 int len = ptypes.length;
525 if (!(0 <= start && start <= end && end <= len))
526 throw newIndexOutOfBoundsException("start="+start+" end="+end);
527 if (start == end) return this;
528 Class<?>[] nptypes;
529 if (start == 0) {
530 if (end == len) {
531 // drop all parameters
532 nptypes = NO_PTYPES;
533 } else {
534 // drop initial parameter(s)
535 nptypes = Arrays.copyOfRange(ptypes, end, len);
536 }
537 } else {
538 if (end == len) {
539 // drop trailing parameter(s)
540 nptypes = Arrays.copyOfRange(ptypes, 0, start);
541 } else {
542 int tail = len - end;
543 nptypes = Arrays.copyOfRange(ptypes, 0, start + tail);
544 System.arraycopy(ptypes, end, nptypes, start, tail);
545 }
546 }
547 return makeImpl(rtype, nptypes, true);
548 }
549
550 /**
551 * Finds or creates a method type with a different return type.
552 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
553 * @param nrtype a return parameter type to replace the old one with
554 * @return the same type, except with the return type change
555 * @throws NullPointerException if {@code nrtype} is null
556 */
557 public MethodType changeReturnType(Class<?> nrtype) {
558 if (returnType() == nrtype) return this;
559 return makeImpl(nrtype, ptypes, true);
560 }
561
562 /**
563 * Reports if this type contains a primitive argument or return value.
564 * The return type {@code void} counts as a primitive.
565 * @return true if any of the types are primitives
566 */
567 public boolean hasPrimitives() {
568 return form.hasPrimitives();
569 }
570
571 /**
572 * Reports if this type contains a wrapper argument or return value.
573 * Wrappers are types which box primitive values, such as {@link Integer}.
574 * The reference type {@code java.lang.Void} counts as a wrapper,
575 * if it occurs as a return type.
576 * @return true if any of the types are wrappers
577 */
578 public boolean hasWrappers() {
579 return unwrap() != this;
580 }
581
582 /**
583 * Erases all reference types to {@code Object}.
584 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
585 * All primitive types (including {@code void}) will remain unchanged.
586 * @return a version of the original type with all reference types replaced
587 */
588 public MethodType erase() {
589 return form.erasedType();
590 }
591
592 /**
593 * Erases all reference types to {@code Object}, and all subword types to {@code int}.
594 * This is the reduced type polymorphism used by private methods
595 * such as {@link MethodHandle#invokeBasic invokeBasic}.
596 * @return a version of the original type with all reference and subword types replaced
597 */
598 /*non-public*/ MethodType basicType() {
599 return form.basicType();
600 }
601
602 /**
603 * @return a version of the original type with MethodHandle prepended as the first argument
604 */
605 /*non-public*/ MethodType invokerType() {
606 return insertParameterTypes(0, MethodHandle.class);
607 }
608
609 /**
610 * Converts all types, both reference and primitive, to {@code Object}.
611 * Convenience method for {@link #genericMethodType(int) genericMethodType}.
612 * The expression {@code type.wrap().erase()} produces the same value
613 * as {@code type.generic()}.
614 * @return a version of the original type with all types replaced
615 */
616 public MethodType generic() {
617 return genericMethodType(parameterCount());
618 }
619
620 /*non-public*/ boolean isGeneric() {
621 return this == erase() && !hasPrimitives();
622 }
623
624 /**
625 * Converts all primitive types to their corresponding wrapper types.
626 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
627 * All reference types (including wrapper types) will remain unchanged.
628 * A {@code void} return type is changed to the type {@code java.lang.Void}.
629 * The expression {@code type.wrap().erase()} produces the same value
630 * as {@code type.generic()}.
631 * @return a version of the original type with all primitive types replaced
632 */
633 public MethodType wrap() {
634 return hasPrimitives() ? wrapWithPrims(this) : this;
635 }
636
637 /**
638 * Converts all wrapper types to their corresponding primitive types.
639 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
640 * All primitive types (including {@code void}) will remain unchanged.
641 * A return type of {@code java.lang.Void} is changed to {@code void}.
642 * @return a version of the original type with all wrapper types replaced
643 */
644 public MethodType unwrap() {
645 MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this);
646 return unwrapWithNoPrims(noprims);
647 }
648
649 private static MethodType wrapWithPrims(MethodType pt) {
650 assert(pt.hasPrimitives());
651 MethodType wt = pt.wrapAlt;
652 if (wt == null) {
653 // fill in lazily
654 wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP, MethodTypeForm.WRAP);
655 assert(wt != null);
656 pt.wrapAlt = wt;
657 }
658 return wt;
659 }
660
661 private static MethodType unwrapWithNoPrims(MethodType wt) {
662 assert(!wt.hasPrimitives());
663 MethodType uwt = wt.wrapAlt;
664 if (uwt == null) {
665 // fill in lazily
666 uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP, MethodTypeForm.UNWRAP);
667 if (uwt == null)
668 uwt = wt; // type has no wrappers or prims at all
669 wt.wrapAlt = uwt;
670 }
671 return uwt;
672 }
673
674 /**
675 * Returns the parameter type at the specified index, within this method type.
676 * @param num the index (zero-based) of the desired parameter type
677 * @return the selected parameter type
678 * @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
679 */
680 public Class<?> parameterType(int num) {
681 return ptypes[num];
682 }
683 /**
684 * Returns the number of parameter types in this method type.
685 * @return the number of parameter types
686 */
687 public int parameterCount() {
688 return ptypes.length;
689 }
690 /**
691 * Returns the return type of this method type.
692 * @return the return type
693 */
694 public Class<?> returnType() {
695 return rtype;
696 }
697
698 /**
699 * Presents the parameter types as a list (a convenience method).
700 * The list will be immutable.
701 * @return the parameter types (as an immutable list)
702 */
703 public List<Class<?>> parameterList() {
704 return Collections.unmodifiableList(Arrays.asList(ptypes));
705 }
706
707 /*non-public*/ Class<?> lastParameterType() {
708 int len = ptypes.length;
709 return len == 0 ? void.class : ptypes[len-1];
710 }
711
712 /**
713 * Presents the parameter types as an array (a convenience method).
714 * Changes to the array will not result in changes to the type.
715 * @return the parameter types (as a fresh copy if necessary)
716 */
717 public Class<?>[] parameterArray() {
718 return ptypes.clone();
719 }
720
721 /**
722 * Compares the specified object with this type for equality.
723 * That is, it returns <tt>true</tt> if and only if the specified object
724 * is also a method type with exactly the same parameters and return type.
725 * @param x object to compare
726 * @see Object#equals(Object)
727 */
728 @Override
729 public boolean equals(Object x) {
730 return this == x || x instanceof MethodType && equals((MethodType)x);
731 }
732
733 private boolean equals(MethodType that) {
734 return this.rtype == that.rtype
735 && Arrays.equals(this.ptypes, that.ptypes);
736 }
737
738 /**
739 * Returns the hash code value for this method type.
740 * It is defined to be the same as the hashcode of a List
741 * whose elements are the return type followed by the
742 * parameter types.
743 * @return the hash code value for this method type
744 * @see Object#hashCode()
745 * @see #equals(Object)
746 * @see List#hashCode()
747 */
748 @Override
749 public int hashCode() {
750 int hashCode = 31 + rtype.hashCode();
751 for (Class<?> ptype : ptypes)
752 hashCode = 31*hashCode + ptype.hashCode();
753 return hashCode;
754 }
755
756 /**
757 * Returns a string representation of the method type,
758 * of the form {@code "(PT0,PT1...)RT"}.
759 * The string representation of a method type is a
760 * parenthesis enclosed, comma separated list of type names,
761 * followed immediately by the return type.
762 * <p>
763 * Each type is represented by its
764 * {@link java.lang.Class#getSimpleName simple name}.
765 */
766 @Override
767 public String toString() {
768 StringJoiner sj = new StringJoiner(",", "(",
769 ")" + rtype.getSimpleName());
770 for (int i = 0; i < ptypes.length; i++) {
771 sj.add(ptypes[i].getSimpleName());
772 }
773 return sj.toString();
774 }
775
776
777 /*non-public*/
778 boolean isViewableAs(MethodType newType) {
779 if (!VerifyType.isNullConversion(returnType(), newType.returnType(), true))
780 return false;
781 int argc = parameterCount();
782 if (argc != newType.parameterCount())
783 return false;
784 for (int i = 0; i < argc; i++) {
785 if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i), true))
786 return false;
787 }
788 return true;
789 }
790 /*non-public*/
791 boolean isCastableTo(MethodType newType) {
792 int argc = parameterCount();
793 if (argc != newType.parameterCount())
794 return false;
795 return true;
796 }
797 /*non-public*/
798 boolean isConvertibleTo(MethodType newType) {
799 if (!canConvert(returnType(), newType.returnType()))
800 return false;
801 int argc = parameterCount();
802 if (argc != newType.parameterCount())
803 return false;
804 for (int i = 0; i < argc; i++) {
805 if (!canConvert(newType.parameterType(i), parameterType(i)))
806 return false;
807 }
808 return true;
809 }
810 /*non-public*/
811 static boolean canConvert(Class<?> src, Class<?> dst) {
812 // short-circuit a few cases:
813 if (src == dst || dst == Object.class) return true;
814 // the remainder of this logic is documented in MethodHandle.asType
815 if (src.isPrimitive()) {
816 // can force void to an explicit null, a la reflect.Method.invoke
817 // can also force void to a primitive zero, by analogy
818 if (src == void.class) return true; //or !dst.isPrimitive()?
819 Wrapper sw = Wrapper.forPrimitiveType(src);
820 if (dst.isPrimitive()) {
821 // P->P must widen
822 return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw);
823 } else {
824 // P->R must box and widen
825 return dst.isAssignableFrom(sw.wrapperType());
826 }
827 } else if (dst.isPrimitive()) {
828 // any value can be dropped
829 if (dst == void.class) return true;
830 Wrapper dw = Wrapper.forPrimitiveType(dst);
831 // R->P must be able to unbox (from a dynamically chosen type) and widen
832 // For example:
833 // Byte/Number/Comparable/Object -> dw:Byte -> byte.
834 // Character/Comparable/Object -> dw:Character -> char
835 // Boolean/Comparable/Object -> dw:Boolean -> boolean
836 // This means that dw must be cast-compatible with src.
837 if (src.isAssignableFrom(dw.wrapperType())) {
838 return true;
839 }
840 // The above does not work if the source reference is strongly typed
841 // to a wrapper whose primitive must be widened. For example:
842 // Byte -> unbox:byte -> short/int/long/float/double
843 // Character -> unbox:char -> int/long/float/double
844 if (Wrapper.isWrapperType(src) &&
845 dw.isConvertibleFrom(Wrapper.forWrapperType(src))) {
846 // can unbox from src and then widen to dst
847 return true;
848 }
849 // We have already covered cases which arise due to runtime unboxing
850 // of a reference type which covers several wrapper types:
851 // Object -> cast:Integer -> unbox:int -> long/float/double
852 // Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double
853 // An marginal case is Number -> dw:Character -> char, which would be OK if there were a
854 // subclass of Number which wraps a value that can convert to char.
855 // Since there is none, we don't need an extra check here to cover char or boolean.
856 return false;
857 } else {
858 // R->R always works, since null is always valid dynamically
859 return true;
860 }
861 }
862
863 /// Queries which have to do with the bytecode architecture
864
865 /** Reports the number of JVM stack slots required to invoke a method
866 * of this type. Note that (for historical reasons) the JVM requires
867 * a second stack slot to pass long and double arguments.
868 * So this method returns {@link #parameterCount() parameterCount} plus the
869 * number of long and double parameters (if any).
870 * <p>
871 * This method is included for the benefit of applications that must
872 * generate bytecodes that process method handles and invokedynamic.
873 * @return the number of JVM stack slots for this type's parameters
874 */
875 /*non-public*/ int parameterSlotCount() {
876 return form.parameterSlotCount();
877 }
878
879 /*non-public*/ Invokers invokers() {
880 Invokers inv = invokers;
881 if (inv != null) return inv;
882 invokers = inv = new Invokers(this);
883 return inv;
884 }
885
886 /** Reports the number of JVM stack slots which carry all parameters including and after
887 * the given position, which must be in the range of 0 to
888 * {@code parameterCount} inclusive. Successive parameters are
889 * more shallowly stacked, and parameters are indexed in the bytecodes
890 * according to their trailing edge. Thus, to obtain the depth
891 * in the outgoing call stack of parameter {@code N}, obtain
892 * the {@code parameterSlotDepth} of its trailing edge
893 * at position {@code N+1}.
894 * <p>
895 * Parameters of type {@code long} and {@code double} occupy
896 * two stack slots (for historical reasons) and all others occupy one.
897 * Therefore, the number returned is the number of arguments
898 * <em>including</em> and <em>after</em> the given parameter,
899 * <em>plus</em> the number of long or double arguments
900 * at or after after the argument for the given parameter.
901 * <p>
902 * This method is included for the benefit of applications that must
903 * generate bytecodes that process method handles and invokedynamic.
904 * @param num an index (zero-based, inclusive) within the parameter types
905 * @return the index of the (shallowest) JVM stack slot transmitting the
906 * given parameter
907 * @throws IllegalArgumentException if {@code num} is negative or greater than {@code parameterCount()}
908 */
909 /*non-public*/ int parameterSlotDepth(int num) {
910 if (num < 0 || num > ptypes.length)
911 parameterType(num); // force a range check
912 return form.parameterToArgSlot(num-1);
913 }
914
915 /** Reports the number of JVM stack slots required to receive a return value
916 * from a method of this type.
917 * If the {@link #returnType() return type} is void, it will be zero,
918 * else if the return type is long or double, it will be two, else one.
919 * <p>
920 * This method is included for the benefit of applications that must
921 * generate bytecodes that process method handles and invokedynamic.
922 * @return the number of JVM stack slots (0, 1, or 2) for this type's return value
923 * Will be removed for PFD.
924 */
925 /*non-public*/ int returnSlotCount() {
926 return form.returnSlotCount();
927 }
928
929 /**
930 * Finds or creates an instance of a method type, given the spelling of its bytecode descriptor.
931 * Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
932 * Any class or interface name embedded in the descriptor string
933 * will be resolved by calling {@link ClassLoader#loadClass(java.lang.String)}
934 * on the given loader (or if it is null, on the system class loader).
935 * <p>
936 * Note that it is possible to encounter method types which cannot be
937 * constructed by this method, because their component types are
938 * not all reachable from a common class loader.
939 * <p>
940 * This method is included for the benefit of applications that must
941 * generate bytecodes that process method handles and {@code invokedynamic}.
942 * @param descriptor a bytecode-level type descriptor string "(T...)T"
943 * @param loader the class loader in which to look up the types
944 * @return a method type matching the bytecode-level type descriptor
945 * @throws NullPointerException if the string is null
946 * @throws IllegalArgumentException if the string is not well-formed
947 * @throws TypeNotPresentException if a named type cannot be found
948 */
949 public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader)
950 throws IllegalArgumentException, TypeNotPresentException
951 {
952 if (!descriptor.startsWith("(") || // also generates NPE if needed
953 descriptor.indexOf(')') < 0 ||
954 descriptor.indexOf('.') >= 0)
955 throw newIllegalArgumentException("not a method descriptor: "+descriptor);
956 List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader);
957 Class<?> rtype = types.remove(types.size() - 1);
958 checkSlotCount(types.size());
959 Class<?>[] ptypes = listToArray(types);
960 return makeImpl(rtype, ptypes, true);
961 }
962
963 /**
964 * Produces a bytecode descriptor representation of the method type.
965 * <p>
966 * Note that this is not a strict inverse of {@link #fromMethodDescriptorString fromMethodDescriptorString}.
967 * Two distinct classes which share a common name but have different class loaders
968 * will appear identical when viewed within descriptor strings.
969 * <p>
970 * This method is included for the benefit of applications that must
971 * generate bytecodes that process method handles and {@code invokedynamic}.
972 * {@link #fromMethodDescriptorString(java.lang.String, java.lang.ClassLoader) fromMethodDescriptorString},
973 * because the latter requires a suitable class loader argument.
974 * @return the bytecode type descriptor representation
975 */
976 public String toMethodDescriptorString() {
977 String desc = methodDescriptor;
978 if (desc == null) {
979 desc = BytecodeDescriptor.unparse(this);
980 methodDescriptor = desc;
981 }
982 return desc;
983 }
984
985 /*non-public*/ static String toFieldDescriptorString(Class<?> cls) {
986 return BytecodeDescriptor.unparse(cls);
987 }
988
989 /// Serialization.
990
991 /**
992 * There are no serializable fields for {@code MethodType}.
993 */
994 private static final java.io.ObjectStreamField[] serialPersistentFields = { };
995
996 /**
997 * Save the {@code MethodType} instance to a stream.
998 *
999 * @serialData
1000 * For portability, the serialized format does not refer to named fields.
1001 * Instead, the return type and parameter type arrays are written directly
1002 * from the {@code writeObject} method, using two calls to {@code s.writeObject}
1003 * as follows:
1004 * <blockquote><pre>{@code
1005 s.writeObject(this.returnType());
1006 s.writeObject(this.parameterArray());
1007 * }</pre></blockquote>
1008 * <p>
1009 * The deserialized field values are checked as if they were
1010 * provided to the factory method {@link #methodType(Class,Class[]) methodType}.
1011 * For example, null values, or {@code void} parameter types,
1012 * will lead to exceptions during deserialization.
1013 * @param s the stream to write the object to
1014 * @throws java.io.IOException if there is a problem writing the object
1015 */
1016 private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
1017 s.defaultWriteObject(); // requires serialPersistentFields to be an empty array
1018 s.writeObject(returnType());
1019 s.writeObject(parameterArray());
1020 }
1021
1022 /**
1023 * Reconstitute the {@code MethodType} instance from a stream (that is,
1024 * deserialize it).
1025 * This instance is a scratch object with bogus final fields.
1026 * It provides the parameters to the factory method called by
1027 * {@link #readResolve readResolve}.
1028 * After that call it is discarded.
1029 * @param s the stream to read the object from
1030 * @throws java.io.IOException if there is a problem reading the object
1031 * @throws ClassNotFoundException if one of the component classes cannot be resolved
1032 * @see #MethodType()
1033 * @see #readResolve
1034 * @see #writeObject
1035 */
1036 private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
1037 s.defaultReadObject(); // requires serialPersistentFields to be an empty array
1038
1039 Class<?> returnType = (Class<?>) s.readObject();
1040 Class<?>[] parameterArray = (Class<?>[]) s.readObject();
1041
1042 // Probably this object will never escape, but let's check
1043 // the field values now, just to be sure.
1044 checkRtype(returnType);
1045 checkPtypes(parameterArray);
1046
1047 parameterArray = parameterArray.clone(); // make sure it is unshared
1048 MethodType_init(returnType, parameterArray);
1049 }
1050
1051 /**
1052 * For serialization only.
1053 * Sets the final fields to null, pending {@code Unsafe.putObject}.
1054 */
1055 private MethodType() {
1056 this.rtype = null;
1057 this.ptypes = null;
1058 }
1059 private void MethodType_init(Class<?> rtype, Class<?>[] ptypes) {
1060 // In order to communicate these values to readResolve, we must
1061 // store them into the implementation-specific final fields.
1062 checkRtype(rtype);
1063 checkPtypes(ptypes);
1064 UNSAFE.putObject(this, rtypeOffset, rtype);
1065 UNSAFE.putObject(this, ptypesOffset, ptypes);
1066 }
1067
1068 // Support for resetting final fields while deserializing
1069 private static final long rtypeOffset, ptypesOffset;
1070 static {
1071 try {
1072 rtypeOffset = UNSAFE.objectFieldOffset
1073 (MethodType.class.getDeclaredField("rtype"));
1074 ptypesOffset = UNSAFE.objectFieldOffset
1075 (MethodType.class.getDeclaredField("ptypes"));
1076 } catch (Exception ex) {
1077 throw new Error(ex);
1078 }
1079 }
1080
1081 /**
1082 * Resolves and initializes a {@code MethodType} object
1083 * after serialization.
1084 * @return the fully initialized {@code MethodType} object
1085 */
1086 private Object readResolve() {
1087 // Do not use a trusted path for deserialization:
1088 //return makeImpl(rtype, ptypes, true);
1089 // Verify all operands, and make sure ptypes is unshared:
1090 return methodType(rtype, ptypes);
1091 }
1092
1093 /**
1094 * Simple implementation of weak concurrent intern set.
1095 *
1096 * @param <T> interned type
1097 */
1098 private static class ConcurrentWeakInternSet<T> {
1099
1100 private final ConcurrentMap<WeakEntry<T>, WeakEntry<T>> map;
1101 private final ReferenceQueue<T> stale;
1102
1103 public ConcurrentWeakInternSet() {
1104 this.map = new ConcurrentHashMap<>();
1105 this.stale = new ReferenceQueue<>();
1106 }
1107
1108 /**
1109 * Get the existing interned element.
1110 * This method returns null if no element is interned.
1111 *
1112 * @param elem element to look up
1113 * @return the interned element
1114 */
1115 public T get(T elem) {
1116 if (elem == null) throw new NullPointerException();
1117 expungeStaleElements();
1118
1119 WeakEntry<T> value = map.get(new WeakEntry<>(elem));
1120 if (value != null) {
1121 T res = value.get();
1122 if (res != null) {
1123 return res;
1124 }
1125 }
1126 return null;
1127 }
1128
1129 /**
1130 * Interns the element.
1131 * Always returns non-null element, matching the one in the intern set.
1132 * Under the race against another add(), it can return <i>different</i>
1133 * element, if another thread beats us to interning it.
1134 *
1135 * @param elem element to add
1136 * @return element that was actually added
1137 */
1138 public T add(T elem) {
1139 if (elem == null) throw new NullPointerException();
1140
1141 // Playing double race here, and so spinloop is required.
1142 // First race is with two concurrent updaters.
1143 // Second race is with GC purging weak ref under our feet.
1144 // Hopefully, we almost always end up with a single pass.
1145 T interned;
1146 WeakEntry<T> e = new WeakEntry<>(elem, stale);
1147 do {
1148 expungeStaleElements();
1149 WeakEntry<T> exist = map.putIfAbsent(e, e);
1150 interned = (exist == null) ? elem : exist.get();
1151 } while (interned == null);
1152 return interned;
1153 }
1154
1155 private void expungeStaleElements() {
1156 Reference<? extends T> reference;
1157 while ((reference = stale.poll()) != null) {
1158 map.remove(reference);
1159 }
1160 }
1161
1162 private static class WeakEntry<T> extends WeakReference<T> {
1163
1164 public final int hashcode;
1165
1166 public WeakEntry(T key, ReferenceQueue<T> queue) {
1167 super(key, queue);
1168 hashcode = key.hashCode();
1169 }
1170
1171 public WeakEntry(T key) {
1172 super(key);
1173 hashcode = key.hashCode();
1174 }
1175
1176 @Override
1177 public boolean equals(Object obj) {
1178 if (obj instanceof WeakEntry) {
1179 Object that = ((WeakEntry) obj).get();
1180 Object mine = get();
1181 return (that == null || mine == null) ? (this == obj) : mine.equals(that);
1182 }
1183 return false;
1184 }
1185
1186 @Override
1187 public int hashCode() {
1188 return hashcode;
1189 }
1190
1191 }
1192 }
1193
1194 }