/*

 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package sun.java2d;

import java.lang.ref.Reference;

/**

* This ReentrantContextProvider implementation uses a ThreadLocal to hold

 * the first ReentrantContext per thread and a ReentrantContextProviderCLQ to

 * store child ReentrantContext instances needed during recursion.

 *

 * Note: this implementation may keep up to one context in memory per thread.

 * Child contexts for recursive uses are stored in the queue using a WEAK

 * reference by default unless specified in the 2 argument constructor.

 *

 * @param <K> ReentrantContext subclass

 */

public abstract class ReentrantContextProviderTL<K extends ReentrantContext>

    extends ReentrantContextProvider<K>

{

    // Thread-local storage:

    private final ThreadLocal<Reference<K>> ctxTL

        = new ThreadLocal<Reference<K>>();

    // ReentrantContext CLQ provider for child contexts:

    private final ReentrantContextProviderCLQ<K> ctxProviderCLQ;

    /**

     * Create a new ReentrantContext provider using the given reference type

     * among hard, soft or weak.

     * It uses weak reference for the child contexts.

     *

     * @param refType reference type

     */

    public ReentrantContextProviderTL(final int refType) {

        this(refType, REF_WEAK);

    }

    /**

     * Create a new ReentrantContext provider using the given reference types

     * among hard, soft or weak

     *

     * @param refTypeTL reference type used by ThreadLocal

     * @param refTypeCLQ reference type used by ReentrantContextProviderCLQ

     */

    public ReentrantContextProviderTL(final int refTypeTL, final int refTypeCLQ)

    {

        super(refTypeTL);

        final ReentrantContextProviderTL<K> parent = this;

        this.ctxProviderCLQ = new ReentrantContextProviderCLQ<K>(refTypeCLQ) {

            @Override

            protected K newContext() {

                return parent.newContext();

            }

        };

    }

    /**

     * Give a ReentrantContext instance for the current thread

     *

     * @return ReentrantContext instance

     */

    @Override

    public final K acquire() {

        K ctx = null;

        final Reference<K> ref = ctxTL.get();

        if (ref != null) {

            ctx = ref.get();

        }

        if (ctx == null) {

            // create a new ReentrantContext if none is available

            ctx = newContext();

            // update thread local reference:

            ctxTL.set(getOrCreateReference(ctx));

        }

        // Check reentrance:

        if (ctx.usage == USAGE_TL_INACTIVE) {

           ctx.usage = USAGE_TL_IN_USE;

        } else {

            // get or create another ReentrantContext from CLQ provider:

            ctx = ctxProviderCLQ.acquire();

        }

        return ctx;

    }

    /**

     * Restore the given ReentrantContext instance for reuse

     *

     * @param ctx ReentrantContext instance

     */

    @Override

    public final void release(final K ctx) {

        if (ctx.usage == USAGE_TL_IN_USE) {

           ctx.usage = USAGE_TL_INACTIVE;

        } else {

            ctxProviderCLQ.release(ctx);

        }

    }

}