90 lines
3.1 KiB
Java
90 lines
3.1 KiB
Java
/*
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* Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.java2d;
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import java.lang.ref.Reference;
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import java.util.concurrent.ConcurrentLinkedQueue;
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/**
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* This ReentrantContextProvider implementation uses one ConcurrentLinkedQueue
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* to store all ReentrantContext instances (thread and its child contexts)
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*
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* Note: this implementation keeps less contexts in memory depending on the
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* concurrent active threads in contrary to a ThreadLocal provider. However,
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* it is slower in highly concurrent workloads.
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*
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* @param <K> ReentrantContext subclass
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*/
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public abstract class ReentrantContextProviderCLQ<K extends ReentrantContext>
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extends ReentrantContextProvider<K>
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{
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// ReentrantContext queue to store all contexts
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private final ConcurrentLinkedQueue<Reference<K>> ctxQueue
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= new ConcurrentLinkedQueue<Reference<K>>();
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/**
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* Create a new ReentrantContext provider using the given reference type
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* among hard, soft or weak based using a ConcurrentLinkedQueue storage
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*
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* @param refType reference type
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*/
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public ReentrantContextProviderCLQ(final int refType) {
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super(refType);
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}
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/**
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* Give a ReentrantContext instance for the current thread
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*
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* @return ReentrantContext instance
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*/
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@Override
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public final K acquire() {
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K ctx = null;
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// Drain queue if all referent are null:
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Reference<K> ref = null;
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while ((ctx == null) && ((ref = ctxQueue.poll()) != null)) {
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ctx = ref.get();
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}
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if (ctx == null) {
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// create a new ReentrantContext if none is available
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ctx = newContext();
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ctx.usage = USAGE_CLQ;
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}
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return ctx;
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}
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/**
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* Restore the given ReentrantContext instance for reuse
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*
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* @param ctx ReentrantContext instance
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*/
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@Override
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public final void release(final K ctx) {
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if (ctx.usage == USAGE_CLQ) {
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ctxQueue.offer(getOrCreateReference(ctx));
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}
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}
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}
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