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. 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 package sun.java2d; 26 27 import java.lang.ref.Reference; 28 import java.util.concurrent.ConcurrentLinkedQueue; 29 30 /** 31 * This ReentrantContextProvider implementation uses one ConcurrentLinkedQueue 32 * to store all ReentrantContext instances (thread and its child contexts) 33 * 34 * Note: this implementation keeps less contexts in memory depending on the 35 * concurrent active threads in contrary to a ThreadLocal provider. However, 36 * it is slower in highly concurrent workloads. 37 * 38 * @param <K> ReentrantContext subclass 39 */ 40 public abstract class ReentrantContextProviderCLQ<K extends ReentrantContext> 41 extends ReentrantContextProvider<K> 42 { 43 // ReentrantContext queue to store all contexts 44 private final ConcurrentLinkedQueue<Reference<K>> ctxQueue 45 = new ConcurrentLinkedQueue<Reference<K>>(); 46 47 /** 48 * Create a new ReentrantContext provider using the given reference type 49 * among hard, soft or weak based using a ConcurrentLinkedQueue storage 50 * 51 * @param refType reference type 52 */ 53 public ReentrantContextProviderCLQ(final int refType) { 54 super(refType); 55 } 56 57 /** 58 * Give a ReentrantContext instance for the current thread 59 * 60 * @return ReentrantContext instance 61 */ 62 @Override 63 public final K acquire() { 64 K ctx = null; 65 // Drain queue if all referent are null: 66 Reference<K> ref = null; 67 while ((ctx == null) && ((ref = ctxQueue.poll()) != null)) { 68 ctx = ref.get(); 69 } 70 if (ctx == null) { 71 // create a new ReentrantContext if none is available 72 ctx = newContext(); 73 ctx.usage = USAGE_CLQ; 74 } 75 return ctx; 76 } 77 78 /** 79 * Restore the given ReentrantContext instance for reuse 80 * 81 * @param ctx ReentrantContext instance 82 */ 83 @Override 84 public final void release(final K ctx) { 85 if (ctx.usage == USAGE_CLQ) { 86 ctxQueue.offer(getOrCreateReference(ctx)); 87 } 88 } 89 }