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 * Copyright (c) 2000, 2018, 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.nio.ch;

import java.io.IOException;

import java.nio.channels.ClosedSelectorException;

import java.nio.channels.IllegalSelectorException;

import java.nio.channels.SelectableChannel;

import java.nio.channels.SelectionKey;

import java.nio.channels.spi.AbstractSelectableChannel;

import java.nio.channels.spi.AbstractSelector;

import java.nio.channels.spi.SelectorProvider;

import java.util.Collections;

import java.util.HashSet;

import java.util.Iterator;

import java.util.Set;

/**

 * Base Selector implementation class.

 */

public abstract class SelectorImpl

    extends AbstractSelector

{

    // The set of keys registered with this Selector

    protected final Set<SelectionKey> keys;

    // The set of keys with data ready for an operation

    protected final Set<SelectionKey> selectedKeys;

    // Public views of the key sets

    private final Set<SelectionKey> publicKeys;             // Immutable

    private final Set<SelectionKey> publicSelectedKeys;     // Removal allowed, but not addition

    protected SelectorImpl(SelectorProvider sp) {

        super(sp);

        keys = new HashSet<>();

        selectedKeys = new HashSet<>();

        publicKeys = Collections.unmodifiableSet(keys);

        publicSelectedKeys = Util.ungrowableSet(selectedKeys);

    }

    private void ensureOpen() {

        if (!isOpen())

            throw new ClosedSelectorException();

    }

    @Override

    public final Set<SelectionKey> keys() {

        ensureOpen();

        return publicKeys;

    }

    @Override

    public final Set<SelectionKey> selectedKeys() {

        ensureOpen();

        return publicSelectedKeys;

    }

    /**

     * Returns the public view of the key sets

     */

    protected final Set<SelectionKey> nioKeys() {

        return publicKeys;

    }

    protected final Set<SelectionKey> nioSelectedKeys() {

        return publicSelectedKeys;

    }

    /**

     * Marks the beginning of a select operation that might block

     */

    protected final void begin(boolean blocking) {

        if (blocking) begin();

    }

    /**

     * Marks the end of a select operation that may have blocked

     */

    protected final void end(boolean blocking) {

        if (blocking) end();

    }

    /**

     * Selects the keys for channels that are ready for I/O operations.

     *

     * @param timeout timeout in milliseconds to wait, 0 to not wait, -1 to

     *                wait indefinitely

     */

    protected abstract int doSelect(long timeout) throws IOException;

    private int lockAndDoSelect(long timeout) throws IOException {

        synchronized (this) {

            ensureOpen();

            synchronized (publicKeys) {

                synchronized (publicSelectedKeys) {

                    return doSelect(timeout);

                }

            }

        }

    }

    @Override

    public final int select(long timeout)

        throws IOException

    {

        if (timeout < 0)

            throw new IllegalArgumentException("Negative timeout");

        return lockAndDoSelect((timeout == 0) ? -1 : timeout);

    }

    @Override

    public final int select() throws IOException {

        return select(0);

    }

    @Override

    public final int selectNow() throws IOException {

        return lockAndDoSelect(0);

    }

    @Override

    public final void implCloseSelector() throws IOException {

        wakeup();

        synchronized (this) {

            implClose();

            synchronized (publicKeys) {

                synchronized (publicSelectedKeys) {

                    // Deregister channels

                    Iterator<SelectionKey> i = keys.iterator();

                    while (i.hasNext()) {

                        SelectionKeyImpl ski = (SelectionKeyImpl)i.next();

                        deregister(ski);

                        SelectableChannel selch = ski.channel();

                        if (!selch.isOpen() && !selch.isRegistered())

                            ((SelChImpl)selch).kill();

                        selectedKeys.remove(ski);

                        i.remove();

                    }

                    assert selectedKeys.isEmpty() && keys.isEmpty();

                }

            }

        }

    }

    protected abstract void implClose() throws IOException;

    @Override

    protected final SelectionKey register(AbstractSelectableChannel ch,

                                          int ops,

                                          Object attachment)

    {

        if (!(ch instanceof SelChImpl))

            throw new IllegalSelectorException();

        SelectionKeyImpl k = new SelectionKeyImpl((SelChImpl)ch, this);

        k.attach(attachment);

        // register with selector (if needed) before adding to key set

        implRegister(k);

        synchronized (publicKeys) {

            keys.add(k);

        }

        k.interestOps(ops);

        return k;

    }

    /**

     * Register the key in the selector.

     *

     * The default implementation checks if the selector is open. It should

     * be overridden by selector implementations as needed.

     */

    protected void implRegister(SelectionKeyImpl ski) {

        ensureOpen();

    }

    protected abstract void implDereg(SelectionKeyImpl ski) throws IOException;

    protected final void processDeregisterQueue() throws IOException {

        assert Thread.holdsLock(this);

        assert Thread.holdsLock(publicKeys);

        assert Thread.holdsLock(publicSelectedKeys);

        Set<SelectionKey> cks = cancelledKeys();

        synchronized (cks) {

            if (!cks.isEmpty()) {

                Iterator<SelectionKey> i = cks.iterator();

                while (i.hasNext()) {

                    SelectionKeyImpl ski = (SelectionKeyImpl)i.next();

                    i.remove();

                    // remove the key from the selector

                    implDereg(ski);

                    selectedKeys.remove(ski);

                    keys.remove(ski);

                    // remove from channel's key set

                    deregister(ski);

                    SelectableChannel ch = ski.channel();

                    if (!ch.isOpen() && !ch.isRegistered())

                        ((SelChImpl)ch).kill();

                }

            }

        }

    }

    /**

     * Change the event set in the selector

     */

    protected abstract void setEventOps(SelectionKeyImpl ski);

}