1 /*
2 * Copyright (c) 2017, 2025, 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.runtime;
27
28 import java.lang.invoke.ConstantCallSite;
29 import java.lang.invoke.MethodHandle;
30 import java.lang.invoke.MethodHandles;
31 import java.lang.invoke.MethodType;
32 import java.lang.invoke.StringConcatFactory;
33 import java.lang.invoke.TypeDescriptor;
34 import java.util.ArrayList;
35 import java.util.Arrays;
36 import java.util.HashMap;
37 import java.util.List;
38 import java.util.Objects;
39
40 import static java.util.Objects.requireNonNull;
41
42 /**
43 * Bootstrap methods for state-driven implementations of core methods,
44 * including {@link Object#equals(Object)}, {@link Object#hashCode()}, and
45 * {@link Object#toString()}. These methods may be used, for example, by
46 * Java compiler implementations to implement the bodies of {@link Object}
47 * methods for record classes.
48 *
49 * @since 16
50 */
51 public final class ObjectMethods {
52
53 private ObjectMethods() { }
54
55 private static final int MAX_STRING_CONCAT_SLOTS = 20;
56
57 private static final MethodHandle FALSE = MethodHandles.zero(boolean.class);
58 private static final MethodHandle TRUE = MethodHandles.constant(boolean.class, true);
59 private static final MethodHandle ZERO = MethodHandles.zero(int.class);
60 private static final MethodHandle CLASS_IS_INSTANCE;
61 private static final MethodHandle OBJECTS_EQUALS;
62 private static final MethodHandle OBJECTS_HASHCODE;
63 private static final MethodHandle OBJECTS_TOSTRING;
64 private static final MethodHandle OBJECT_EQ;
65 private static final MethodHandle HASH_COMBINER;
66
67 /* package-private */
68 static final HashMap<Class<?>, MethodHandle> primitiveEquals = new HashMap<>();
69
70 private static final HashMap<Class<?>, MethodHandle> primitiveHashers = new HashMap<>();
71 private static final HashMap<Class<?>, MethodHandle> primitiveToString = new HashMap<>();
72
73 static {
74 try {
75 Class<ObjectMethods> OBJECT_METHODS_CLASS = ObjectMethods.class;
76 MethodHandles.Lookup publicLookup = MethodHandles.publicLookup();
77 MethodHandles.Lookup lookup = MethodHandles.lookup();
78
79 CLASS_IS_INSTANCE = publicLookup.findVirtual(Class.class, "isInstance",
80 MethodType.methodType(boolean.class, Object.class));
81 OBJECTS_EQUALS = publicLookup.findStatic(Objects.class, "equals",
82 MethodType.methodType(boolean.class, Object.class, Object.class));
83 OBJECTS_HASHCODE = publicLookup.findStatic(Objects.class, "hashCode",
84 MethodType.methodType(int.class, Object.class));
85 OBJECTS_TOSTRING = publicLookup.findStatic(Objects.class, "toString",
86 MethodType.methodType(String.class, Object.class));
87
88 OBJECT_EQ = lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
89 MethodType.methodType(boolean.class, Object.class, Object.class));
90 HASH_COMBINER = lookup.findStatic(OBJECT_METHODS_CLASS, "hashCombiner",
91 MethodType.methodType(int.class, int.class, int.class));
92
93 primitiveEquals.put(byte.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
94 MethodType.methodType(boolean.class, byte.class, byte.class)));
95 primitiveEquals.put(short.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
96 MethodType.methodType(boolean.class, short.class, short.class)));
97 primitiveEquals.put(char.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
98 MethodType.methodType(boolean.class, char.class, char.class)));
99 primitiveEquals.put(int.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
100 MethodType.methodType(boolean.class, int.class, int.class)));
101 primitiveEquals.put(long.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
102 MethodType.methodType(boolean.class, long.class, long.class)));
103 primitiveEquals.put(float.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
104 MethodType.methodType(boolean.class, float.class, float.class)));
105 primitiveEquals.put(double.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
106 MethodType.methodType(boolean.class, double.class, double.class)));
107 primitiveEquals.put(boolean.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
108 MethodType.methodType(boolean.class, boolean.class, boolean.class)));
109
110 primitiveHashers.put(byte.class, lookup.findStatic(Byte.class, "hashCode",
111 MethodType.methodType(int.class, byte.class)));
112 primitiveHashers.put(short.class, lookup.findStatic(Short.class, "hashCode",
113 MethodType.methodType(int.class, short.class)));
114 primitiveHashers.put(char.class, lookup.findStatic(Character.class, "hashCode",
115 MethodType.methodType(int.class, char.class)));
116 primitiveHashers.put(int.class, lookup.findStatic(Integer.class, "hashCode",
117 MethodType.methodType(int.class, int.class)));
118 primitiveHashers.put(long.class, lookup.findStatic(Long.class, "hashCode",
119 MethodType.methodType(int.class, long.class)));
120 primitiveHashers.put(float.class, lookup.findStatic(Float.class, "hashCode",
121 MethodType.methodType(int.class, float.class)));
122 primitiveHashers.put(double.class, lookup.findStatic(Double.class, "hashCode",
123 MethodType.methodType(int.class, double.class)));
124 primitiveHashers.put(boolean.class, lookup.findStatic(Boolean.class, "hashCode",
125 MethodType.methodType(int.class, boolean.class)));
126
127 primitiveToString.put(byte.class, lookup.findStatic(Byte.class, "toString",
128 MethodType.methodType(String.class, byte.class)));
129 primitiveToString.put(short.class, lookup.findStatic(Short.class, "toString",
130 MethodType.methodType(String.class, short.class)));
131 primitiveToString.put(char.class, lookup.findStatic(Character.class, "toString",
132 MethodType.methodType(String.class, char.class)));
133 primitiveToString.put(int.class, lookup.findStatic(Integer.class, "toString",
134 MethodType.methodType(String.class, int.class)));
135 primitiveToString.put(long.class, lookup.findStatic(Long.class, "toString",
136 MethodType.methodType(String.class, long.class)));
137 primitiveToString.put(float.class, lookup.findStatic(Float.class, "toString",
138 MethodType.methodType(String.class, float.class)));
139 primitiveToString.put(double.class, lookup.findStatic(Double.class, "toString",
140 MethodType.methodType(String.class, double.class)));
141 primitiveToString.put(boolean.class, lookup.findStatic(Boolean.class, "toString",
142 MethodType.methodType(String.class, boolean.class)));
143 }
144 catch (ReflectiveOperationException e) {
145 throw new RuntimeException(e);
146 }
147 }
148
149 private static int hashCombiner(int x, int y) {
150 return x*31 + y;
151 }
152
153 private static boolean eq(Object a, Object b) { return a == b; }
154 private static boolean eq(byte a, byte b) { return a == b; }
155 private static boolean eq(short a, short b) { return a == b; }
156 private static boolean eq(char a, char b) { return a == b; }
157 private static boolean eq(int a, int b) { return a == b; }
158 private static boolean eq(long a, long b) { return a == b; }
159 private static boolean eq(float a, float b) { return Float.compare(a, b) == 0; }
160 private static boolean eq(double a, double b) { return Double.compare(a, b) == 0; }
161 private static boolean eq(boolean a, boolean b) { return a == b; }
162
163 /** Get the method handle for combining two values of a given type */
164 private static MethodHandle equalator(Class<?> clazz) {
165 return (clazz.isPrimitive()
166 ? primitiveEquals.get(clazz)
167 : OBJECTS_EQUALS.asType(MethodType.methodType(boolean.class, clazz, clazz)));
168 }
169
170 /** Get the hasher for a value of a given type */
171 private static MethodHandle hasher(Class<?> clazz) {
172 return (clazz.isPrimitive()
173 ? primitiveHashers.get(clazz)
174 : OBJECTS_HASHCODE.asType(MethodType.methodType(int.class, clazz)));
175 }
176
177 /** Get the stringifier for a value of a given type */
178 private static MethodHandle stringifier(Class<?> clazz) {
179 return (clazz.isPrimitive()
180 ? primitiveToString.get(clazz)
181 : OBJECTS_TOSTRING.asType(MethodType.methodType(String.class, clazz)));
182 }
183
184 /**
185 * Generates a method handle for the {@code equals} method for a given data class
186 * @param receiverClass the data class
187 * @param getters the list of getters
188 * @return the method handle
189 */
190 private static MethodHandle makeEquals(Class<?> receiverClass,
191 List<MethodHandle> getters) {
192 MethodType rr = MethodType.methodType(boolean.class, receiverClass, receiverClass);
193 MethodType ro = MethodType.methodType(boolean.class, receiverClass, Object.class);
194 MethodHandle instanceFalse = MethodHandles.dropArguments(FALSE, 0, receiverClass, Object.class); // (RO)Z
195 MethodHandle instanceTrue = MethodHandles.dropArguments(TRUE, 0, receiverClass, Object.class); // (RO)Z
196 MethodHandle isSameObject = OBJECT_EQ.asType(ro); // (RO)Z
197 MethodHandle isInstance = MethodHandles.dropArguments(CLASS_IS_INSTANCE.bindTo(receiverClass), 0, receiverClass); // (RO)Z
198 MethodHandle accumulator = MethodHandles.dropArguments(TRUE, 0, receiverClass, receiverClass); // (RR)Z
199
200 for (MethodHandle getter : getters) {
201 MethodHandle equalator = equalator(getter.type().returnType()); // (TT)Z
202 MethodHandle thisFieldEqual = MethodHandles.filterArguments(equalator, 0, getter, getter); // (RR)Z
203 accumulator = MethodHandles.guardWithTest(thisFieldEqual, accumulator, instanceFalse.asType(rr));
204 }
205
206 return MethodHandles.guardWithTest(isSameObject,
207 instanceTrue,
208 MethodHandles.guardWithTest(isInstance, accumulator.asType(ro), instanceFalse));
209 }
210
211 /**
212 * Generates a method handle for the {@code hashCode} method for a given data class
213 * @param receiverClass the data class
214 * @param getters the list of getters
215 * @return the method handle
216 */
217 private static MethodHandle makeHashCode(Class<?> receiverClass,
218 List<MethodHandle> getters) {
219 MethodHandle accumulator = MethodHandles.dropArguments(ZERO, 0, receiverClass); // (R)I
220
221 // @@@ Use loop combinator instead?
222 for (MethodHandle getter : getters) {
223 MethodHandle hasher = hasher(getter.type().returnType()); // (T)I
224 MethodHandle hashThisField = MethodHandles.filterArguments(hasher, 0, getter); // (R)I
225 MethodHandle combineHashes = MethodHandles.filterArguments(HASH_COMBINER, 0, accumulator, hashThisField); // (RR)I
226 accumulator = MethodHandles.permuteArguments(combineHashes, accumulator.type(), 0, 0); // adapt (R)I to (RR)I
227 }
228
229 return accumulator;
230 }
231
232 /**
233 * Generates a method handle for the {@code toString} method for a given data class
234 * @param receiverClass the data class
235 * @param getters the list of getters
236 * @param names the names
237 * @return the method handle
238 */
239 private static MethodHandle makeToString(MethodHandles.Lookup lookup,
240 Class<?> receiverClass,
241 MethodHandle[] getters,
242 List<String> names) {
243 assert getters.length == names.size();
244 if (getters.length == 0) {
245 // special case
246 MethodHandle emptyRecordCase = MethodHandles.constant(String.class, receiverClass.getSimpleName() + "[]");
247 emptyRecordCase = MethodHandles.dropArguments(emptyRecordCase, 0, receiverClass); // (R)S
248 return emptyRecordCase;
249 }
250
251 boolean firstTime = true;
252 MethodHandle[] mhs;
253 List<List<MethodHandle>> splits;
254 MethodHandle[] toSplit = getters;
255 int namesIndex = 0;
256 do {
257 /* StringConcatFactory::makeConcatWithConstants can only deal with 200 slots, longs and double occupy two
258 * the rest 1 slot, we need to chop the current `getters` into chunks, it could be that for records with
259 * a lot of components that we need to do a couple of iterations. The main difference between the first
260 * iteration and the rest would be on the recipe
261 */
262 splits = split(toSplit);
263 mhs = new MethodHandle[splits.size()];
264 for (int splitIndex = 0; splitIndex < splits.size(); splitIndex++) {
265 String recipe = "";
266 if (firstTime && splitIndex == 0) {
267 recipe = receiverClass.getSimpleName() + "[";
268 }
269 for (int i = 0; i < splits.get(splitIndex).size(); i++) {
270 recipe += firstTime ? names.get(namesIndex) + "=" + "\1" : "\1";
271 if (firstTime && namesIndex != names.size() - 1) {
272 recipe += ", ";
273 }
274 namesIndex++;
275 }
276 if (firstTime && splitIndex == splits.size() - 1) {
277 recipe += "]";
278 }
279 Class<?>[] concatTypeArgs = new Class<?>[splits.get(splitIndex).size()];
280 // special case: no need to create another getters if there is only one split
281 MethodHandle[] currentSplitGetters = new MethodHandle[splits.get(splitIndex).size()];
282 for (int j = 0; j < splits.get(splitIndex).size(); j++) {
283 concatTypeArgs[j] = splits.get(splitIndex).get(j).type().returnType();
284 currentSplitGetters[j] = splits.get(splitIndex).get(j);
285 }
286 MethodType concatMT = MethodType.methodType(String.class, concatTypeArgs);
287 try {
288 mhs[splitIndex] = StringConcatFactory.makeConcatWithConstants(
289 lookup, "",
290 concatMT,
291 recipe,
292 new Object[0]
293 ).getTarget();
294 mhs[splitIndex] = MethodHandles.filterArguments(mhs[splitIndex], 0, currentSplitGetters);
295 // this will spread the receiver class across all the getters
296 mhs[splitIndex] = MethodHandles.permuteArguments(
297 mhs[splitIndex],
298 MethodType.methodType(String.class, receiverClass),
299 new int[splits.get(splitIndex).size()]
300 );
301 } catch (Throwable t) {
302 throw new RuntimeException(t);
303 }
304 }
305 toSplit = mhs;
306 firstTime = false;
307 } while (splits.size() > 1);
308 return mhs[0];
309 }
310
311 /**
312 * Chops the getters into smaller chunks according to the maximum number of slots
313 * StringConcatFactory::makeConcatWithConstants can chew
314 * @param getters the current getters
315 * @return chunks that won't surpass the maximum number of slots StringConcatFactory::makeConcatWithConstants can chew
316 */
317 private static List<List<MethodHandle>> split(MethodHandle[] getters) {
318 List<List<MethodHandle>> splits = new ArrayList<>();
319
320 int slots = 0;
321
322 // Need to peel, so that neither call has more than acceptable number
323 // of slots for the arguments.
324 List<MethodHandle> cArgs = new ArrayList<>();
325 for (MethodHandle methodHandle : getters) {
326 Class<?> returnType = methodHandle.type().returnType();
327 int needSlots = (returnType == long.class || returnType == double.class) ? 2 : 1;
328 if (slots + needSlots > MAX_STRING_CONCAT_SLOTS) {
329 splits.add(cArgs);
330 cArgs = new ArrayList<>();
331 slots = 0;
332 }
333 cArgs.add(methodHandle);
334 slots += needSlots;
335 }
336
337 // Flush the tail slice
338 if (!cArgs.isEmpty()) {
339 splits.add(cArgs);
340 }
341
342 return splits;
343 }
344
345 /**
346 * Bootstrap method to generate the {@link Object#equals(Object)},
347 * {@link Object#hashCode()}, and {@link Object#toString()} methods, based
348 * on a description of the component names and accessor methods, for either
349 * {@code invokedynamic} call sites or dynamic constant pool entries.
350 *
351 * For more detail on the semantics of the generated methods see the specification
352 * of {@link java.lang.Record#equals(Object)}, {@link java.lang.Record#hashCode()} and
353 * {@link java.lang.Record#toString()}.
354 *
355 *
356 * @param lookup Every bootstrap method is expected to have a {@code lookup}
357 * which usually represents a lookup context with the
358 * accessibility privileges of the caller. This is because
359 * {@code invokedynamic} call sites always provide a {@code lookup}
360 * to the corresponding bootstrap method, but this method just
361 * ignores the {@code lookup} parameter
362 * @param methodName the name of the method to generate, which must be one of
363 * {@code "equals"}, {@code "hashCode"}, or {@code "toString"}
364 * @param type a {@link MethodType} corresponding the descriptor type
365 * for the method, which must correspond to the descriptor
366 * for the corresponding {@link Object} method, if linking
367 * an {@code invokedynamic} call site, or the
368 * constant {@code MethodHandle.class}, if linking a
369 * dynamic constant
370 * @param recordClass the record class hosting the record components
371 * @param names the list of component names, joined into a string
372 * separated by ";", or the empty string if there are no
373 * components. This parameter is ignored if the {@code methodName}
374 * parameter is {@code "equals"} or {@code "hashCode"}
375 * @param getters method handles for the accessor methods for the components
376 * @return a call site if invoked by indy, or a method handle
377 * if invoked by a condy
378 * @throws IllegalArgumentException if the bootstrap arguments are invalid
379 * or inconsistent
380 * @throws NullPointerException if any argument is {@code null} or if any element
381 * in the {@code getters} array is {@code null}
382 * @throws Throwable if any exception is thrown during call site construction
383 */
384 public static Object bootstrap(MethodHandles.Lookup lookup, String methodName, TypeDescriptor type,
385 Class<?> recordClass,
386 String names,
387 MethodHandle... getters) throws Throwable {
388 requireNonNull(lookup);
389 requireNonNull(methodName);
390 requireNonNull(type);
391 requireNonNull(recordClass);
392 requireNonNull(names);
393 requireNonNull(getters);
394 Arrays.stream(getters).forEach(Objects::requireNonNull);
395 MethodType methodType;
396 if (type instanceof MethodType mt) {
397 methodType = mt;
398 if (mt.parameterType(0) != recordClass) {
399 throw new IllegalArgumentException("Bad method type: " + mt);
400 }
401 } else {
402 methodType = null;
403 if (!MethodHandle.class.equals(type))
404 throw new IllegalArgumentException(type.toString());
405 }
406 List<MethodHandle> getterList = List.of(getters);
407 for (MethodHandle getter : getterList) {
408 if (getter.type().parameterType(0) != recordClass) {
409 throw new IllegalArgumentException("Bad receiver type: " + getter);
410 }
411 }
412 MethodHandle handle = switch (methodName) {
413 case "equals" -> {
414 if (methodType != null && !methodType.equals(MethodType.methodType(boolean.class, recordClass, Object.class)))
415 throw new IllegalArgumentException("Bad method type: " + methodType);
416 yield makeEquals(recordClass, getterList);
417 }
418 case "hashCode" -> {
419 if (methodType != null && !methodType.equals(MethodType.methodType(int.class, recordClass)))
420 throw new IllegalArgumentException("Bad method type: " + methodType);
421 yield makeHashCode(recordClass, getterList);
422 }
423 case "toString" -> {
424 if (methodType != null && !methodType.equals(MethodType.methodType(String.class, recordClass)))
425 throw new IllegalArgumentException("Bad method type: " + methodType);
426 List<String> nameList = "".equals(names) ? List.of() : List.of(names.split(";"));
427 if (nameList.size() != getterList.size())
428 throw new IllegalArgumentException("Name list and accessor list do not match");
429 yield makeToString(lookup, recordClass, getters, nameList);
430 }
431 default -> throw new IllegalArgumentException(methodName);
432 };
433 return methodType != null ? new ConstantCallSite(handle) : handle;
434 }
435 }