1 /*
2 * Copyright (c) 2016, 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.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24 package java.lang.reflect;
25
26 import jdk.internal.loader.BootLoader;
27 import jdk.internal.misc.JavaLangAccess;
28 import jdk.internal.misc.SharedSecrets;
29
30 import java.util.Iterator;
31 import java.util.Objects;
32 import java.util.concurrent.ConcurrentHashMap;
33 import java.util.function.BiFunction;
34 import java.util.function.Supplier;
35
36 /**
37 * AbstractClassLoaderValue is a superclass of root-{@link ClassLoaderValue}
38 * and {@link Sub sub}-ClassLoaderValue.
39 *
40 * @param <CLV> the type of concrete ClassLoaderValue (this type)
41 * @param <V> the type of values associated with ClassLoaderValue
42 */
43 abstract class AbstractClassLoaderValue<CLV extends AbstractClassLoaderValue<CLV, V>, V> {
44
45 /**
46 * Sole constructor.
47 */
48 AbstractClassLoaderValue() {}
49
50 /**
51 * Returns the key component of this ClassLoaderValue. The key component of
52 * the root-{@link ClassLoaderValue} is the ClassLoaderValue itself,
53 * while the key component of a {@link #sub(Object) sub}-ClassLoaderValue
54 * is what was given to construct it.
55 *
56 * @return the key component of this ClassLoaderValue.
57 */
58 public abstract Object key();
59
60 /**
61 * Constructs new sub-ClassLoaderValue of this ClassLoaderValue with given
62 * key component.
63 *
64 * @param key the key component of the sub-ClassLoaderValue.
65 * @param <K> the type of the key component.
66 * @return a sub-ClassLoaderValue of this ClassLoaderValue for given key
67 */
68 public <K> Sub<K> sub(K key) {
69 return new Sub<>(key);
70 }
71
72 /**
73 * Returns {@code true} if this ClassLoaderValue is equal to given {@code clv}
74 * or if this ClassLoaderValue was derived from given {@code clv} by a chain
75 * of {@link #sub(Object)} invocations.
76 *
77 * @param clv the ClassLoaderValue to test this against
78 * @return if this ClassLoaderValue is equal to given {@code clv} or
79 * its descendant
80 */
81 public abstract boolean isEqualOrDescendantOf(AbstractClassLoaderValue<?, V> clv);
82
83 /**
84 * Returns the value associated with this ClassLoaderValue and given ClassLoader
85 * or {@code null} if there is none.
86 *
87 * @param cl the ClassLoader for the associated value
88 * @return the value associated with this ClassLoaderValue and given ClassLoader
89 * or {@code null} if there is none.
90 */
91 public V get(ClassLoader cl) {
92 Object val = AbstractClassLoaderValue.<CLV>map(cl).get(this);
93 try {
94 return extractValue(val);
95 } catch (Memoizer.RecursiveInvocationException e) {
96 // propagate recursive get() for the same key that is just
97 // being calculated in computeIfAbsent()
98 throw e;
99 } catch (Throwable t) {
100 // don't propagate exceptions thrown from Memoizer - pretend
101 // that there was no entry
102 // (computeIfAbsent invocation will try to remove it anyway)
103 return null;
104 }
105 }
106
107 /**
108 * Associates given value {@code v} with this ClassLoaderValue and given
109 * ClassLoader and returns {@code null} if there was no previously associated
110 * value or does nothing and returns previously associated value if there
111 * was one.
112 *
113 * @param cl the ClassLoader for the associated value
114 * @param v the value to associate
115 * @return previously associated value or null if there was none
116 */
117 public V putIfAbsent(ClassLoader cl, V v) {
118 ConcurrentHashMap<CLV, Object> map = map(cl);
119 @SuppressWarnings("unchecked")
120 CLV clv = (CLV) this;
121 while (true) {
122 try {
123 Object val = map.putIfAbsent(clv, v);
124 return extractValue(val);
125 } catch (Memoizer.RecursiveInvocationException e) {
126 // propagate RecursiveInvocationException for the same key that
127 // is just being calculated in computeIfAbsent
128 throw e;
129 } catch (Throwable t) {
130 // don't propagate exceptions thrown from foreign Memoizer -
131 // pretend that there was no entry and retry
132 // (foreign computeIfAbsent invocation will try to remove it anyway)
133 }
134 // TODO:
135 // Thread.onSpinLoop(); // when available
136 }
137 }
138
139 /**
140 * Removes the value associated with this ClassLoaderValue and given
141 * ClassLoader if the associated value is equal to given value {@code v} and
142 * returns {@code true} or does nothing and returns {@code false} if there is
143 * no currently associated value or it is not equal to given value {@code v}.
144 *
145 * @param cl the ClassLoader for the associated value
146 * @param v the value to compare with currently associated value
147 * @return {@code true} if the association was removed or {@code false} if not
148 */
149 public boolean remove(ClassLoader cl, Object v) {
150 return AbstractClassLoaderValue.<CLV>map(cl).remove(this, v);
151 }
152
153 /**
154 * Returns the value associated with this ClassLoaderValue and given
155 * ClassLoader if there is one or computes the value by invoking given
156 * {@code mappingFunction}, associates it and returns it.
157 * <p>
158 * Computation and association of the computed value is performed atomically
159 * by the 1st thread that requests a particular association while holding a
160 * lock associated with this ClassLoaderValue and given ClassLoader.
161 * Nested calls from the {@code mappingFunction} to {@link #get},
162 * {@link #putIfAbsent} or {@link #computeIfAbsent} for the same association
163 * are not allowed and throw {@link IllegalStateException}. Nested call to
164 * {@link #remove} for the same association is allowed but will always return
165 * {@code false} regardless of passed-in comparison value. Nested calls for
166 * other association(s) are allowed, but care should be taken to avoid
167 * deadlocks. When two threads perform nested computations of the overlapping
168 * set of associations they should always request them in the same order.
169 *
170 * @param cl the ClassLoader for the associated value
171 * @param mappingFunction the function to compute the value
172 * @return the value associated with given ClassLoader and key components.
173 * @throws IllegalStateException if a direct or indirect invocation from
174 * within given {@code mappingFunction} that
175 * computes the value of a particular association
176 * to {@link #get}, {@link #putIfAbsent} or
177 * {@link #computeIfAbsent}
178 * for the same association is attempted.
179 */
180 public V computeIfAbsent(ClassLoader cl,
181 BiFunction<
182 ? super ClassLoader,
183 ? super CLV,
184 ? extends V
185 > mappingFunction) throws IllegalStateException {
186 ConcurrentHashMap<CLV, Object> map = map(cl);
187 @SuppressWarnings("unchecked")
188 CLV clv = (CLV) this;
189 Memoizer<CLV, V> mv = null;
190 while (true) {
191 Object val = (mv == null) ? map.get(clv) : map.putIfAbsent(clv, mv);
192 if (val == null) {
193 if (mv == null) {
194 // create Memoizer lazily when 1st needed and restart loop
195 mv = new Memoizer<>(cl, clv, mappingFunction);
196 continue;
197 }
198 // mv != null, therefore sv == null was a result of successful
199 // putIfAbsent
200 try {
201 // trigger Memoizer to compute the value
202 V v = mv.get();
203 // attempt to replace our Memoizer with the value
204 map.replace(clv, mv, v);
205 // return computed value
206 return v;
207 } catch (Throwable t) {
208 // our Memoizer has thrown, attempt to remove it
209 map.remove(clv, mv);
210 // propagate exception because it's from our Memoizer
211 throw t;
212 }
213 } else {
214 try {
215 return extractValue(val);
216 } catch (Memoizer.RecursiveInvocationException e) {
217 // propagate recursive attempts to calculate the same
218 // value as being calculated at the moment
219 throw e;
220 } catch (Throwable t) {
221 // don't propagate exceptions thrown from foreign Memoizer -
222 // pretend that there was no entry and retry
223 // (foreign computeIfAbsent invocation will try to remove it anyway)
224 }
225 }
226 // TODO:
227 // Thread.onSpinLoop(); // when available
228 }
229 }
230
231 /**
232 * Removes all values associated with given ClassLoader {@code cl} and
233 * {@link #isEqualOrDescendantOf(AbstractClassLoaderValue) this or descendants}
234 * of this ClassLoaderValue.
235 * This is not an atomic operation. Other threads may see some associations
236 * be already removed and others still present while this method is executing.
237 * <p>
238 * The sole intention of this method is to cleanup after a unit test that
239 * tests ClassLoaderValue directly. It is not intended for use in
240 * actual algorithms.
241 *
242 * @param cl the associated ClassLoader of the values to be removed
243 */
244 public void removeAll(ClassLoader cl) {
245 ConcurrentHashMap<CLV, Object> map = map(cl);
246 for (Iterator<CLV> i = map.keySet().iterator(); i.hasNext(); ) {
247 if (i.next().isEqualOrDescendantOf(this)) {
248 i.remove();
249 }
250 }
251 }
252
253 private static final JavaLangAccess JLA = SharedSecrets.getJavaLangAccess();
254
255 /**
256 * @return a ConcurrentHashMap for given ClassLoader
257 */
258 @SuppressWarnings("unchecked")
259 private static <CLV extends AbstractClassLoaderValue<CLV, ?>>
260 ConcurrentHashMap<CLV, Object> map(ClassLoader cl) {
261 return (ConcurrentHashMap<CLV, Object>)
262 (cl == null
263 ? BootLoader.getClassLoaderValueMap()
264 : JLA.createOrGetClassLoaderValueMap(cl)
265 );
266 }
267
268 /**
269 * @return value extracted from the {@link Memoizer} if given
270 * {@code memoizerOrValue} parameter is a {@code Memoizer} or
271 * just return given parameter.
272 */
273 @SuppressWarnings("unchecked")
274 private V extractValue(Object memoizerOrValue) {
275 if (memoizerOrValue instanceof Memoizer) {
276 return ((Memoizer<?, V>) memoizerOrValue).get();
277 } else {
278 return (V) memoizerOrValue;
279 }
280 }
281
282 /**
283 * A memorizing supplier that invokes given {@code mappingFunction} just once
284 * and then returns memorized result or throws memorized exception.
285 * If given mappingFunction returns null, it is converted to NullPointerException,
286 * thrown from the Memoizer's {@link #get()} method and memorized.
287 * If the Memoizer is invoked recursively from the given {@code mappingFunction},
288 * {@link RecursiveInvocationException} is thrown, but not memorized.
289 * The in-flight call to the {@link #get()} can still complete successfully if
290 * such exception is handled by the mappingFunction.
291 */
292 private static final class Memoizer<CLV extends AbstractClassLoaderValue<CLV, V>, V>
293 implements Supplier<V> {
294
295 private final ClassLoader cl;
296 private final CLV clv;
297 private final BiFunction<? super ClassLoader, ? super CLV, ? extends V>
298 mappingFunction;
299
300 private volatile V v;
301 private volatile Throwable t;
302 private boolean inCall;
303
304 Memoizer(ClassLoader cl,
305 CLV clv,
306 BiFunction<? super ClassLoader, ? super CLV, ? extends V>
307 mappingFunction
308 ) {
309 this.cl = cl;
310 this.clv = clv;
311 this.mappingFunction = mappingFunction;
312 }
313
314 @Override
315 public V get() throws RecursiveInvocationException {
316 V v = this.v;
317 if (v != null) return v;
318 Throwable t = this.t;
319 if (t == null) {
320 synchronized (this) {
321 if ((v = this.v) == null && (t = this.t) == null) {
322 if (inCall) {
323 throw new RecursiveInvocationException();
324 }
325 inCall = true;
326 try {
327 this.v = v = Objects.requireNonNull(
328 mappingFunction.apply(cl, clv));
329 } catch (Throwable x) {
330 this.t = t = x;
331 } finally {
332 inCall = false;
333 }
334 }
335 }
336 }
337 if (v != null) return v;
338 if (t instanceof Error) {
339 throw (Error) t;
340 } else if (t instanceof RuntimeException) {
341 throw (RuntimeException) t;
342 } else {
343 throw new UndeclaredThrowableException(t);
344 }
345 }
346
347 static class RecursiveInvocationException extends IllegalStateException {
348 private static final long serialVersionUID = 1L;
349
350 RecursiveInvocationException() {
351 super("Recursive call");
352 }
353 }
354 }
355
356 /**
357 * sub-ClassLoaderValue is an inner class of {@link AbstractClassLoaderValue}
358 * and also a subclass of it. It can therefore be instantiated as an inner
359 * class of either an instance of root-{@link ClassLoaderValue} or another
360 * instance of itself. This enables composing type-safe compound keys of
361 * arbitrary length:
362 * <pre>{@code
363 * ClassLoaderValue<V> clv = new ClassLoaderValue<>();
364 * ClassLoaderValue<V>.Sub<K1>.Sub<K2>.Sub<K3> clv_k123 =
365 * clv.sub(k1).sub(k2).sub(k3);
366 * }</pre>
367 * From which individual components are accessible in a type-safe way:
368 * <pre>{@code
369 * K1 k1 = clv_k123.parent().parent().key();
370 * K2 k2 = clv_k123.parent().key();
371 * K3 k3 = clv_k123.key();
372 * }</pre>
373 * This allows specifying non-capturing lambdas for the mapping function of
374 * {@link #computeIfAbsent(ClassLoader, BiFunction)} operation that can
375 * access individual key components from passed-in
376 * sub-[sub-...]ClassLoaderValue instance in a type-safe way.
377 *
378 * @param <K> the type of {@link #key()} component contained in the
379 * sub-ClassLoaderValue.
380 */
381 final class Sub<K> extends AbstractClassLoaderValue<Sub<K>, V> {
382
383 private final K key;
384
385 Sub(K key) {
386 this.key = key;
387 }
388
389 /**
390 * @return the parent ClassLoaderValue this sub-ClassLoaderValue
391 * has been {@link #sub(Object) derived} from.
392 */
393 public AbstractClassLoaderValue<CLV, V> parent() {
394 return AbstractClassLoaderValue.this;
395 }
396
397 /**
398 * @return the key component of this sub-ClassLoaderValue.
399 */
400 @Override
401 public K key() {
402 return key;
403 }
404
405 /**
406 * sub-ClassLoaderValue is a descendant of given {@code clv} if it is
407 * either equal to it or if its {@link #parent() parent} is a
408 * descendant of given {@code clv}.
409 */
410 @Override
411 public boolean isEqualOrDescendantOf(AbstractClassLoaderValue<?, V> clv) {
412 return equals(Objects.requireNonNull(clv)) ||
413 parent().isEqualOrDescendantOf(clv);
414 }
415
416 @Override
417 public boolean equals(Object o) {
418 if (this == o) return true;
419 if (!(o instanceof Sub)) return false;
420 @SuppressWarnings("unchecked")
421 Sub<?> that = (Sub<?>) o;
422 return this.parent().equals(that.parent()) &&
423 Objects.equals(this.key, that.key);
424 }
425
426 @Override
427 public int hashCode() {
428 return 31 * parent().hashCode() +
429 Objects.hashCode(key);
430 }
431 }
432 }