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 * 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,

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 *

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package java.nio.channels.spi;

import java.lang.invoke.MethodHandles;

import java.lang.invoke.VarHandle;

import java.nio.channels.SelectionKey;

import java.nio.channels.Selector;

import sun.nio.ch.SelectionKeyImpl;

import sun.nio.ch.SelectorImpl;

/**

 * Base implementation class for selection keys.

 *

 * <p> This class tracks the validity of the key and implements cancellation.

 *

 * @author Mark Reinhold

 * @author JSR-51 Expert Group

 * @since 1.4

 */

public abstract class AbstractSelectionKey

    extends SelectionKey

{

    private static final VarHandle INVALID;

    static {

        try {

            MethodHandles.Lookup l = MethodHandles.lookup();

            INVALID = l.findVarHandle(AbstractSelectionKey.class, "invalid", boolean.class);

        } catch (Exception e) {

            throw new InternalError(e);

        }

    }

    /**

     * Initializes a new instance of this class.

     */

    protected AbstractSelectionKey() { }

    private volatile boolean invalid;

    public final boolean isValid() {

        return !invalid;

    }

    void invalidate() {                                 // package-private

        invalid = true;

    }

    /**

     * Cancels this key.

     *

     * <p> If this key has not yet been cancelled then it is added to its

     * selector's cancelled-key set while synchronized on that set.  </p>

     */

    public final void cancel() {

        boolean changed = (boolean) INVALID.compareAndSet(this, false, true);

        if (changed) {

            Selector sel = selector();

            if (sel instanceof SelectorImpl) {

                // queue cancelled key directly

                ((SelectorImpl) sel).cancel((SelectionKeyImpl) this);

            } else {

                ((AbstractSelector) sel).cancel(this);

            }

        }

    }

}