1 /*
  2  * Copyright (c) 2017, 2022, 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 jdk.internal.value.PrimitiveClass;
 29 
 30 import java.lang.invoke.ConstantCallSite;
 31 import java.lang.invoke.MethodHandle;
 32 import java.lang.invoke.MethodHandles;
 33 import java.lang.invoke.MethodType;
 34 import java.lang.invoke.StringConcatFactory;
 35 import java.lang.invoke.TypeDescriptor;
 36 import java.security.AccessController;
 37 import java.security.PrivilegedAction;
 38 import java.util.ArrayList;
 39 import java.util.Arrays;
 40 import java.util.HashMap;
 41 import java.util.List;
 42 import java.util.Objects;
 43 
 44 import static java.util.Objects.requireNonNull;
 45 
 46 /**
 47  * Bootstrap methods for state-driven implementations of core methods,
 48  * including {@link Object#equals(Object)}, {@link Object#hashCode()}, and
 49  * {@link Object#toString()}.  These methods may be used, for example, by
 50  * Java compiler implementations to implement the bodies of {@link Object}
 51  * methods for record classes.
 52  *
 53  * @since 16
 54  */
 55 public class ObjectMethods {
 56 
 57     private ObjectMethods() { }
 58 
 59     private static final int MAX_STRING_CONCAT_SLOTS = 20;
 60 
 61     private static final MethodType DESCRIPTOR_MT = MethodType.methodType(MethodType.class);
 62     private static final MethodType NAMES_MT = MethodType.methodType(List.class);
 63     private static final MethodHandle FALSE = MethodHandles.constant(boolean.class, false);
 64     private static final MethodHandle TRUE = MethodHandles.constant(boolean.class, true);
 65     private static final MethodHandle ZERO = MethodHandles.constant(int.class, 0);
 66     private static final MethodHandle CLASS_IS_INSTANCE;
 67     private static final MethodHandle OBJECT_EQUALS;
 68     private static final MethodHandle OBJECTS_EQUALS;
 69     private static final MethodHandle OBJECTS_HASHCODE;
 70     private static final MethodHandle OBJECTS_TOSTRING;
 71     private static final MethodHandle OBJECT_EQ;
 72     private static final MethodHandle OBJECT_HASHCODE;
 73     private static final MethodHandle OBJECT_TO_STRING;
 74     private static final MethodHandle STRING_FORMAT;
 75     private static final MethodHandle HASH_COMBINER;
 76 
 77     /* package-private */
 78     static final HashMap<Class<?>, MethodHandle> primitiveEquals = new HashMap<>();
 79 
 80     private static final HashMap<Class<?>, MethodHandle> primitiveHashers = new HashMap<>();
 81     private static final HashMap<Class<?>, MethodHandle> primitiveToString = new HashMap<>();
 82 
 83     static {
 84         try {
 85             Class<ObjectMethods> OBJECT_METHODS_CLASS = ObjectMethods.class;
 86             MethodHandles.Lookup publicLookup = MethodHandles.publicLookup();
 87             MethodHandles.Lookup lookup = MethodHandles.lookup();
 88 
 89             @SuppressWarnings("removal")
 90             ClassLoader loader = AccessController.doPrivileged(new PrivilegedAction<ClassLoader>() {
 91                 @Override public ClassLoader run() { return ClassLoader.getPlatformClassLoader(); }
 92             });
 93 
 94             CLASS_IS_INSTANCE = publicLookup.findVirtual(Class.class, "isInstance",
 95                                                          MethodType.methodType(boolean.class, Object.class));
 96             OBJECT_EQUALS = publicLookup.findVirtual(Object.class, "equals",
 97                                                      MethodType.methodType(boolean.class, Object.class));
 98             OBJECT_HASHCODE = publicLookup.findVirtual(Object.class, "hashCode",
 99                                                        MethodType.fromMethodDescriptorString("()I", loader));
100             OBJECT_TO_STRING = publicLookup.findVirtual(Object.class, "toString",
101                                                         MethodType.methodType(String.class));
102             STRING_FORMAT = publicLookup.findStatic(String.class, "format",
103                                                     MethodType.methodType(String.class, String.class, Object[].class));
104             OBJECTS_EQUALS = publicLookup.findStatic(Objects.class, "equals",
105                                                      MethodType.methodType(boolean.class, Object.class, Object.class));
106             OBJECTS_HASHCODE = publicLookup.findStatic(Objects.class, "hashCode",
107                                                        MethodType.methodType(int.class, Object.class));
108             OBJECTS_TOSTRING = publicLookup.findStatic(Objects.class, "toString",
109                                                        MethodType.methodType(String.class, Object.class));
110 
111             OBJECT_EQ = lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
112                                           MethodType.methodType(boolean.class, Object.class, Object.class));
113             HASH_COMBINER = lookup.findStatic(OBJECT_METHODS_CLASS, "hashCombiner",
114                                               MethodType.fromMethodDescriptorString("(II)I", loader));
115 
116             primitiveEquals.put(byte.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
117                                                               MethodType.fromMethodDescriptorString("(BB)Z", loader)));
118             primitiveEquals.put(short.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
119                                                                MethodType.fromMethodDescriptorString("(SS)Z", loader)));
120             primitiveEquals.put(char.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
121                                                               MethodType.fromMethodDescriptorString("(CC)Z", loader)));
122             primitiveEquals.put(int.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
123                                                              MethodType.fromMethodDescriptorString("(II)Z", loader)));
124             primitiveEquals.put(long.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
125                                                               MethodType.fromMethodDescriptorString("(JJ)Z", loader)));
126             primitiveEquals.put(float.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
127                                                                MethodType.fromMethodDescriptorString("(FF)Z", loader)));
128             primitiveEquals.put(double.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
129                                                                 MethodType.fromMethodDescriptorString("(DD)Z", loader)));
130             primitiveEquals.put(boolean.class, lookup.findStatic(OBJECT_METHODS_CLASS, "eq",
131                                                                  MethodType.fromMethodDescriptorString("(ZZ)Z", loader)));
132 
133             primitiveHashers.put(byte.class, lookup.findStatic(Byte.class, "hashCode",
134                                                                MethodType.fromMethodDescriptorString("(B)I", loader)));
135             primitiveHashers.put(short.class, lookup.findStatic(Short.class, "hashCode",
136                                                                 MethodType.fromMethodDescriptorString("(S)I", loader)));
137             primitiveHashers.put(char.class, lookup.findStatic(Character.class, "hashCode",
138                                                                MethodType.fromMethodDescriptorString("(C)I", loader)));
139             primitiveHashers.put(int.class, lookup.findStatic(Integer.class, "hashCode",
140                                                               MethodType.fromMethodDescriptorString("(I)I", loader)));
141             primitiveHashers.put(long.class, lookup.findStatic(Long.class, "hashCode",
142                                                                MethodType.fromMethodDescriptorString("(J)I", loader)));
143             primitiveHashers.put(float.class, lookup.findStatic(Float.class, "hashCode",
144                                                                 MethodType.fromMethodDescriptorString("(F)I", loader)));
145             primitiveHashers.put(double.class, lookup.findStatic(Double.class, "hashCode",
146                                                                  MethodType.fromMethodDescriptorString("(D)I", loader)));
147             primitiveHashers.put(boolean.class, lookup.findStatic(Boolean.class, "hashCode",
148                                                                   MethodType.fromMethodDescriptorString("(Z)I", loader)));
149 
150             primitiveToString.put(byte.class, lookup.findStatic(Byte.class, "toString",
151                                                                 MethodType.methodType(String.class, byte.class)));
152             primitiveToString.put(short.class, lookup.findStatic(Short.class, "toString",
153                                                                  MethodType.methodType(String.class, short.class)));
154             primitiveToString.put(char.class, lookup.findStatic(Character.class, "toString",
155                                                                 MethodType.methodType(String.class, char.class)));
156             primitiveToString.put(int.class, lookup.findStatic(Integer.class, "toString",
157                                                                MethodType.methodType(String.class, int.class)));
158             primitiveToString.put(long.class, lookup.findStatic(Long.class, "toString",
159                                                                 MethodType.methodType(String.class, long.class)));
160             primitiveToString.put(float.class, lookup.findStatic(Float.class, "toString",
161                                                                  MethodType.methodType(String.class, float.class)));
162             primitiveToString.put(double.class, lookup.findStatic(Double.class, "toString",
163                                                                   MethodType.methodType(String.class, double.class)));
164             primitiveToString.put(boolean.class, lookup.findStatic(Boolean.class, "toString",
165                                                                    MethodType.methodType(String.class, boolean.class)));
166         }
167         catch (ReflectiveOperationException e) {
168             throw new RuntimeException(e);
169         }
170     }
171 
172     private static int hashCombiner(int x, int y) {
173         return x*31 + y;
174     }
175 
176     private static boolean eq(Object a, Object b) { return a == b; }
177     private static boolean eq(byte a, byte b) { return a == b; }
178     private static boolean eq(short a, short b) { return a == b; }
179     private static boolean eq(char a, char b) { return a == b; }
180     private static boolean eq(int a, int b) { return a == b; }
181     private static boolean eq(long a, long b) { return a == b; }
182     private static boolean eq(float a, float b) { return Float.compare(a, b) == 0; }
183     private static boolean eq(double a, double b) { return Double.compare(a, b) == 0; }
184     private static boolean eq(boolean a, boolean b) { return a == b; }
185 
186     /** Get the method handle for combining two values of a given type */
187     private static MethodHandle equalator(Class<?> clazz) {
188         return (clazz.isPrimitive()
189                 ? primitiveEquals.get(clazz)
190                 : OBJECTS_EQUALS.asType(MethodType.methodType(boolean.class, clazz, clazz)));
191     }
192 
193     /** Get the hasher for a value of a given type */
194     private static MethodHandle hasher(Class<?> clazz) {
195         return (clazz.isPrimitive()
196                 ? primitiveHashers.get(clazz)
197                 : OBJECTS_HASHCODE.asType(MethodType.methodType(int.class, clazz)));
198     }
199 
200     /** Get the stringifier for a value of a given type */
201     private static MethodHandle stringifier(Class<?> clazz) {
202         return (clazz.isPrimitive()
203                 ? primitiveToString.get(clazz)
204                 : OBJECTS_TOSTRING.asType(MethodType.methodType(String.class, clazz)));
205     }
206 
207     /**
208      * Generates a method handle for the {@code equals} method for a given data class
209      * @param receiverClass   the data class
210      * @param getters         the list of getters
211      * @return the method handle
212      */
213     private static MethodHandle makeEquals(Class<?> receiverClass,
214                                           List<MethodHandle> getters) {
215         MethodType rr = MethodType.methodType(boolean.class, receiverClass, receiverClass);
216         MethodType ro = MethodType.methodType(boolean.class, receiverClass, Object.class);
217         MethodHandle instanceFalse = MethodHandles.dropArguments(FALSE, 0, receiverClass, Object.class); // (RO)Z
218         MethodHandle instanceTrue = MethodHandles.dropArguments(TRUE, 0, receiverClass, Object.class); // (RO)Z
219         MethodHandle isSameObject = OBJECT_EQ.asType(ro); // (RO)Z
220         MethodHandle isInstance = MethodHandles.dropArguments(CLASS_IS_INSTANCE.bindTo(receiverClass), 0, receiverClass); // (RO)Z
221         MethodHandle accumulator = MethodHandles.dropArguments(TRUE, 0, receiverClass, receiverClass); // (RR)Z
222 
223         for (MethodHandle getter : getters) {
224             MethodHandle equalator = equalator(getter.type().returnType()); // (TT)Z
225             MethodHandle thisFieldEqual = MethodHandles.filterArguments(equalator, 0, getter, getter); // (RR)Z
226             accumulator = MethodHandles.guardWithTest(thisFieldEqual, accumulator, instanceFalse.asType(rr));
227         }
228 
229         return MethodHandles.guardWithTest(isSameObject,
230                                            instanceTrue,
231                                            MethodHandles.guardWithTest(isInstance, accumulator.asType(ro), instanceFalse));
232     }
233 
234     /**
235      * Generates a method handle for the {@code hashCode} method for a given data class
236      * @param receiverClass   the data class
237      * @param getters         the list of getters
238      * @return the method handle
239      */
240     private static MethodHandle makeHashCode(Class<?> receiverClass,
241                                             List<MethodHandle> getters) {
242         MethodHandle accumulator = MethodHandles.dropArguments(ZERO, 0, receiverClass); // (R)I
243 
244         // @@@ Use loop combinator instead?
245         for (MethodHandle getter : getters) {
246             MethodHandle hasher = hasher(getter.type().returnType()); // (T)I
247             MethodHandle hashThisField = MethodHandles.filterArguments(hasher, 0, getter);    // (R)I
248             MethodHandle combineHashes = MethodHandles.filterArguments(HASH_COMBINER, 0, accumulator, hashThisField); // (RR)I
249             accumulator = MethodHandles.permuteArguments(combineHashes, accumulator.type(), 0, 0); // adapt (R)I to (RR)I
250         }
251 
252         return accumulator;
253     }
254 
255     /**
256      * Generates a method handle for the {@code toString} method for a given data class
257      * @param receiverClass   the data class
258      * @param simpleName      the simple name of the record class
259      * @param getters         the list of getters
260      * @param names           the names
261      * @return the method handle
262      */
263     private static MethodHandle makeToString(MethodHandles.Lookup lookup,
264                                             Class<?> receiverClass,
265                                             String simpleName,
266                                             MethodHandle[] getters,
267                                             List<String> names) {
268         assert getters.length == names.size();
269         if (getters.length == 0) {
270             // special case
271             MethodHandle emptyRecordCase = MethodHandles.constant(String.class, simpleName + "[]");
272             emptyRecordCase = MethodHandles.dropArguments(emptyRecordCase, 0, receiverClass); // (R)S
273             return emptyRecordCase;
274         }
275 
276         boolean firstTime = true;
277         MethodHandle[] mhs;
278         List<List<MethodHandle>> splits;
279         MethodHandle[] toSplit = getters;
280         int namesIndex = 0;
281         do {
282             /* StringConcatFactory::makeConcatWithConstants can only deal with 200 slots, longs and double occupy two
283              * the rest 1 slot, we need to chop the current `getters` into chunks, it could be that for records with
284              * a lot of components that we need to do a couple of iterations. The main difference between the first
285              * iteration and the rest would be on the recipe
286              */
287             splits = split(toSplit);
288             mhs = new MethodHandle[splits.size()];
289             for (int splitIndex = 0; splitIndex < splits.size(); splitIndex++) {
290                 String recipe = "";
291                 if (firstTime && splitIndex == 0) {
292                     recipe = simpleName + "[";
293                 }
294                 for (int i = 0; i < splits.get(splitIndex).size(); i++) {
295                     recipe += firstTime ? names.get(namesIndex) + "=" + "\1" : "\1";
296                     if (firstTime && namesIndex != names.size() - 1) {
297                         recipe += ", ";
298                     }
299                     namesIndex++;
300                 }
301                 if (firstTime && splitIndex == splits.size() - 1) {
302                     recipe += "]";
303                 }
304                 Class<?>[] concatTypeArgs = new Class<?>[splits.get(splitIndex).size()];
305                 // special case: no need to create another getters if there is only one split
306                 MethodHandle[] currentSplitGetters = new MethodHandle[splits.get(splitIndex).size()];
307                 for (int j = 0; j < splits.get(splitIndex).size(); j++) {
308                     concatTypeArgs[j] = splits.get(splitIndex).get(j).type().returnType();
309                     currentSplitGetters[j] = splits.get(splitIndex).get(j);
310                 }
311                 MethodType concatMT = MethodType.methodType(String.class, concatTypeArgs);
312                 try {
313                     mhs[splitIndex] = StringConcatFactory.makeConcatWithConstants(
314                             lookup, "",
315                             concatMT,
316                             recipe,
317                             new Object[0]
318                     ).getTarget();
319                     mhs[splitIndex] = MethodHandles.filterArguments(mhs[splitIndex], 0, currentSplitGetters);
320                     // this will spread the receiver class across all the getters
321                     mhs[splitIndex] = MethodHandles.permuteArguments(
322                             mhs[splitIndex],
323                             MethodType.methodType(String.class, receiverClass),
324                             new int[splits.get(splitIndex).size()]
325                     );
326                 } catch (Throwable t) {
327                     throw new RuntimeException(t);
328                 }
329             }
330             toSplit = mhs;
331             firstTime = false;
332         } while (splits.size() > 1);
333         return mhs[0];
334     }
335 
336     /**
337      * Chops the getters into smaller chunks according to the maximum number of slots
338      * StringConcatFactory::makeConcatWithConstants can chew
339      * @param getters the current getters
340      * @return chunks that won't surpass the maximum number of slots StringConcatFactory::makeConcatWithConstants can chew
341      */
342     private static List<List<MethodHandle>> split(MethodHandle[] getters) {
343         List<List<MethodHandle>> splits = new ArrayList<>();
344 
345         int slots = 0;
346 
347         // Need to peel, so that neither call has more than acceptable number
348         // of slots for the arguments.
349         List<MethodHandle> cArgs = new ArrayList<>();
350         for (MethodHandle methodHandle : getters) {
351             Class<?> returnType = methodHandle.type().returnType();
352             int needSlots = (returnType == long.class || returnType == double.class) ? 2 : 1;
353             if (slots + needSlots > MAX_STRING_CONCAT_SLOTS) {
354                 splits.add(cArgs);
355                 cArgs = new ArrayList<>();
356                 slots = 0;
357             }
358             cArgs.add(methodHandle);
359             slots += needSlots;
360         }
361 
362         // Flush the tail slice
363         if (!cArgs.isEmpty()) {
364             splits.add(cArgs);
365         }
366 
367         return splits;
368     }
369 
370     /**
371      * Bootstrap method to generate the {@link Object#equals(Object)},
372      * {@link Object#hashCode()}, and {@link Object#toString()} methods, based
373      * on a description of the component names and accessor methods, for either
374      * {@code invokedynamic} call sites or dynamic constant pool entries.
375      *
376      * For more detail on the semantics of the generated methods see the specification
377      * of {@link java.lang.Record#equals(Object)}, {@link java.lang.Record#hashCode()} and
378      * {@link java.lang.Record#toString()}.
379      *
380      *
381      * @param lookup       Every bootstrap method is expected to have a {@code lookup}
382      *                     which usually represents a lookup context with the
383      *                     accessibility privileges of the caller. This is because
384      *                     {@code invokedynamic} call sites always provide a {@code lookup}
385      *                     to the corresponding bootstrap method, but this method just
386      *                     ignores the {@code lookup} parameter
387      * @param methodName   the name of the method to generate, which must be one of
388      *                     {@code "equals"}, {@code "hashCode"}, or {@code "toString"}
389      * @param type         a {@link MethodType} corresponding the descriptor type
390      *                     for the method, which must correspond to the descriptor
391      *                     for the corresponding {@link Object} method, if linking
392      *                     an {@code invokedynamic} call site, or the
393      *                     constant {@code MethodHandle.class}, if linking a
394      *                     dynamic constant
395      * @param recordClass  the record class hosting the record components
396      * @param names        the list of component names, joined into a string
397      *                     separated by ";", or the empty string if there are no
398      *                     components. This parameter is ignored if the {@code methodName}
399      *                     parameter is {@code "equals"} or {@code "hashCode"}
400      * @param getters      method handles for the accessor methods for the components
401      * @return             a call site if invoked by indy, or a method handle
402      *                     if invoked by a condy
403      * @throws IllegalArgumentException if the bootstrap arguments are invalid
404      *                                  or inconsistent
405      * @throws NullPointerException if any argument is {@code null} or if any element
406      *                              in the {@code getters} array is {@code null}
407      * @throws Throwable if any exception is thrown during call site construction
408      */
409     public static Object bootstrap(MethodHandles.Lookup lookup, String methodName, TypeDescriptor type,
410                                    Class<?> recordClass,
411                                    String names,
412                                    MethodHandle... getters) throws Throwable {
413         requireNonNull(lookup);
414         requireNonNull(methodName);
415         requireNonNull(type);
416         requireNonNull(recordClass);
417         requireNonNull(names);
418         requireNonNull(getters);
419         Arrays.stream(getters).forEach(Objects::requireNonNull);
420         MethodType methodType;
421         Class<?> receiverType = PrimitiveClass.isPrimitiveClass(recordClass)
422                 ? PrimitiveClass.asValueType(recordClass) : recordClass;
423         if (type instanceof MethodType mt) {
424             methodType = mt;
425             if (mt.parameterType(0) != receiverType) {
426                 throw new IllegalArgumentException("Bad method type: " + mt);
427             }
428         } else {
429             methodType = null;
430             if (!MethodHandle.class.equals(type))
431                 throw new IllegalArgumentException(type.toString());
432         }
433         List<MethodHandle> getterList = List.of(getters);
434         for (MethodHandle getter : getterList) {
435             if (getter.type().parameterType(0) != receiverType) {
436                 throw new IllegalArgumentException("Bad receiver type: " + getter);
437             }
438         }
439         MethodHandle handle = switch (methodName) {
440             case "equals"   -> {
441                 if (methodType != null && !methodType.equals(MethodType.methodType(boolean.class, receiverType, Object.class)))
442                     throw new IllegalArgumentException("Bad method type: " + methodType);
443                 yield makeEquals(receiverType, getterList);
444             }
445             case "hashCode" -> {
446                 if (methodType != null && !methodType.equals(MethodType.methodType(int.class, receiverType)))
447                     throw new IllegalArgumentException("Bad method type: " + methodType);
448                 yield makeHashCode(receiverType, getterList);
449             }
450             case "toString" -> {
451                 if (methodType != null && !methodType.equals(MethodType.methodType(String.class, receiverType)))
452                     throw new IllegalArgumentException("Bad method type: " + methodType);
453                 List<String> nameList = "".equals(names) ? List.of() : List.of(names.split(";"));
454                 if (nameList.size() != getterList.size())
455                     throw new IllegalArgumentException("Name list and accessor list do not match");
456                 yield makeToString(lookup, receiverType, recordClass.getSimpleName(), getters, nameList);
457             }
458             default -> throw new IllegalArgumentException(methodName);
459         };
460         return methodType != null ? new ConstantCallSite(handle) : handle;
461     }
462 }