1 /* 2 * Copyright (c) 2021, 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.ref; 27 28 /** 29 * An implementation of a ReferenceQueue that uses native monitors. 30 * The use of java.util.concurrent.lock locks interacts with various mechanisms, 31 * such as virtual threads and ForkJoinPool, that might not be appropriate for some 32 * low-level mechanisms, in particular MethodType's weak intern set. 33 */ 34 final class NativeReferenceQueue<T> extends ReferenceQueue<T> { 35 public NativeReferenceQueue() { 36 super(0); 37 } 38 39 private static class Lock { }; 40 private final Lock lock = new Lock(); 41 42 @Override 43 void signal() { 44 lock.notifyAll(); 45 } 46 @Override 47 void await() throws InterruptedException { 48 lock.wait(); 49 } 50 51 @Override 52 void await(long timeoutMillis) throws InterruptedException { 53 lock.wait(timeoutMillis); 54 } 55 56 @Override 57 boolean enqueue(Reference<? extends T> r) { 58 synchronized(lock) { 59 return enqueue0(r); 60 } 61 } 62 63 @Override 64 public Reference<? extends T> poll() { 65 if (headIsNull()) 66 return null; 67 68 synchronized(lock) { 69 return poll0(); 70 } 71 } 72 73 @Override 74 public Reference<? extends T> remove(long timeout) 75 throws IllegalArgumentException, InterruptedException { 76 if (timeout < 0) 77 throw new IllegalArgumentException("Negative timeout value"); 78 if (timeout == 0) 79 return remove(); 80 81 synchronized(lock) { 82 return remove0(timeout); 83 } 84 } 85 86 @Override 87 public Reference<? extends T> remove() throws InterruptedException { 88 synchronized(lock) { 89 return remove0(); 90 } 91 } 92 }