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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
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	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.
	*/

	abstract class SelectorImpl
	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;

	/**
	* Invoked by selection operations to process the cancelled-key set
	*/
	protected final void processDeregisterQueue() throws IOException {
	assert Thread.holdsLock(this);
	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();
	}
	}
	}
	}

	/**
	* 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);
	}

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