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 * 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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 *

 * 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.Objects;

import java.util.Set;

import java.util.concurrent.ConcurrentHashMap;

import java.util.function.Consumer;

/**

 * Base Selector implementation class.

 */

    extends AbstractSelector

{

    // The set of keys registered with this Selector

    private final Set<SelectionKey> keys;

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

    private 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

    // used to check for reentrancy

    private boolean inSelect;

    protected SelectorImpl(SelectorProvider sp) {

        super(sp);

        keys = ConcurrentHashMap.newKeySet();

        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;

    }

    /**

     * 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 action  the action to perform, can be null

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

     *                wait indefinitely

     */

    protected abstract int doSelect(Consumer<SelectionKey> action, long timeout)

        throws IOException;

    private int lockAndDoSelect(Consumer<SelectionKey> action, long timeout)

        throws IOException

    {

        synchronized (this) {

            ensureOpen();

            if (inSelect)

                throw new IllegalStateException("select in progress");

            inSelect = true;

            try {

                synchronized (publicSelectedKeys) {

                    return doSelect(action, timeout);

                }

            } finally {

                inSelect = false;

            }

        }

    }

    @Override

    public final int select(long timeout) throws IOException {

        if (timeout < 0)

            throw new IllegalArgumentException("Negative timeout");

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

    }

    @Override

    public final int select() throws IOException {

        return lockAndDoSelect(null, -1);

    }

    @Override

    public final int selectNow() throws IOException {

        return lockAndDoSelect(null, 0);

    }

    @Override

    public final int select(Consumer<SelectionKey> action, long timeout)

        throws IOException

    {

        Objects.requireNonNull(action);

        if (timeout < 0)

            throw new IllegalArgumentException("Negative timeout");

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

    }

    @Override

    public final int select(Consumer<SelectionKey> action) throws IOException {

        Objects.requireNonNull(action);

        return lockAndDoSelect(action, -1);

    }

    @Override

    public final int selectNow(Consumer<SelectionKey> action) throws IOException {

        Objects.requireNonNull(action);

        return lockAndDoSelect(action, 0);

    }

    /**

     * Invoked by implCloseSelector to close the selector.

     */

    protected abstract void implClose() throws IOException;

    @Override

    public final void implCloseSelector() throws IOException {

        wakeup();

        synchronized (this) {

            implClose();

            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();

            }

        }

    }

    @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 (if needed) before adding to key set

        implRegister(k);

        // add to the selector's key set, removing it immediately if the selector

        // is closed. The key is not in the channel's key set at this point but

        // it may be observed by a thread iterating over the selector's key set.

        keys.add(k);

        try {

            k.interestOps(ops);

        } catch (ClosedSelectorException e) {

            assert ch.keyFor(this) == null;

            keys.remove(k);

            k.cancel();

            throw e;

        }

        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();

    }

    /**

     * Removes the key from the selector

     */

    protected abstract void implDereg(SelectionKeyImpl ski) throws IOException;

    /**

     */

    protected final void processDeregisterQueue() throws IOException {

        assert Thread.holdsLock(this);

        assert Thread.holdsLock(publicSelectedKeys);

            }

        }

    }

    /**

     * Invoked by selection operations to handle ready events. If an action

     * is specified then it is invoked to handle the key, otherwise the key

     * is added to the selected-key set (or updated when it is already in the

     * set).

     */

    protected final int processReadyEvents(int rOps,

                                           SelectionKeyImpl ski,

                                           Consumer<SelectionKey> action) {

        if (action != null) {

            ski.translateAndSetReadyOps(rOps);

            if ((ski.nioReadyOps() & ski.nioInterestOps()) != 0) {

                action.accept(ski);

                ensureOpen();

                return 1;

            }

        } else {

            assert Thread.holdsLock(publicSelectedKeys);

            if (selectedKeys.contains(ski)) {

                if (ski.translateAndUpdateReadyOps(rOps)) {

                    return 1;

                }

            } else {

                ski.translateAndSetReadyOps(rOps);

                if ((ski.nioReadyOps() & ski.nioInterestOps()) != 0) {

                    selectedKeys.add(ski);

                    return 1;

                }

            }

        }

        return 0;

    }

    /**

     * Invoked by interestOps to ensure the interest ops are updated at the

     * next selection operation.

     */

    protected abstract void setEventOps(SelectionKeyImpl ski);

}