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	/*
	* Copyright (c) 2008, 2011, 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.fs;

	import java.nio.file.*;
	import java.util.*;

	/**
	* Base implementation class for watch keys.
	*/

	abstract class AbstractWatchKey implements WatchKey {

	/**
	* Maximum size of event list (in the future this may be tunable)
	*/
	static final int MAX_EVENT_LIST_SIZE = 512;

	/**
	* Special event to signal overflow
	*/
	static final Event<Object> OVERFLOW_EVENT =
	new Event<Object>(StandardWatchEventKinds.OVERFLOW, null);

	/**
	* Possible key states
	*/
	private static enum State { READY, SIGNALLED };

	// reference to watcher
	private final AbstractWatchService watcher;

	// reference to the original directory
	private final Path dir;

	// key state
	private State state;

	// pending events
	private List<WatchEvent<?>> events;

	// maps a context to the last event for the context (iff the last queued
	// event for the context is an ENTRY_MODIFY event).
	private Map<Object,WatchEvent<?>> lastModifyEvents;

	protected AbstractWatchKey(Path dir, AbstractWatchService watcher) {
	this.watcher = watcher;
	this.dir = dir;
	this.state = State.READY;
	this.events = new ArrayList<>();
	this.lastModifyEvents = new HashMap<>();
	}

	final AbstractWatchService watcher() {
	return watcher;
	}

	/**
	* Return the original watchable (Path)
	*/
	@Override
	public Path watchable() {
	return dir;
	}

	/**
	* Enqueues this key to the watch service
	*/
	final void signal() {
	synchronized (this) {
	if (state == State.READY) {
	state = State.SIGNALLED;
	watcher.enqueueKey(this);
	}
	}
	}

	/**
	* Adds the event to this key and signals it.
	*/
	@SuppressWarnings("unchecked")
	final void signalEvent(WatchEvent.Kind<?> kind, Object context) {
	boolean isModify = (kind == StandardWatchEventKinds.ENTRY_MODIFY);
	synchronized (this) {
	int size = events.size();
	if (size > 0) {
	// if the previous event is an OVERFLOW event or this is a
	// repeated event then we simply increment the counter
	WatchEvent<?> prev = events.get(size-1);
	if ((prev.kind() == StandardWatchEventKinds.OVERFLOW) \|\|
	((kind == prev.kind() &&
	Objects.equals(context, prev.context()))))
	{
	((Event<?>)prev).increment();
	return;
	}

	// if this is a modify event and the last entry for the context
	// is a modify event then we simply increment the count
	if (!lastModifyEvents.isEmpty()) {
	if (isModify) {
	WatchEvent<?> ev = lastModifyEvents.get(context);
	if (ev != null) {
	assert ev.kind() == StandardWatchEventKinds.ENTRY_MODIFY;
	((Event<?>)ev).increment();
	return;
	}
	} else {
	// not a modify event so remove from the map as the
	// last event will no longer be a modify event.
	lastModifyEvents.remove(context);
	}
	}

	// if the list has reached the limit then drop pending events
	// and queue an OVERFLOW event
	if (size >= MAX_EVENT_LIST_SIZE) {
	kind = StandardWatchEventKinds.OVERFLOW;
	isModify = false;
	context = null;
	}
	}

	// non-repeated event
	Event<Object> ev =
	new Event<>((WatchEvent.Kind<Object>)kind, context);
	if (isModify) {
	lastModifyEvents.put(context, ev);
	} else if (kind == StandardWatchEventKinds.OVERFLOW) {
	// drop all pending events
	events.clear();
	lastModifyEvents.clear();
	}
	events.add(ev);
	signal();
	}
	}

	@Override
	public final List<WatchEvent<?>> pollEvents() {
	synchronized (this) {
	List<WatchEvent<?>> result = events;
	events = new ArrayList<>();
	lastModifyEvents.clear();
	return result;
	}
	}

	@Override
	public final boolean reset() {
	synchronized (this) {
	if (state == State.SIGNALLED && isValid()) {
	if (events.isEmpty()) {
	state = State.READY;
	} else {
	// pending events so re-queue key
	watcher.enqueueKey(this);
	}
	}
	return isValid();
	}
	}

	/**
	* WatchEvent implementation
	*/
	private static class Event<T> implements WatchEvent<T> {
	private final WatchEvent.Kind<T> kind;
	private final T context;

	// synchronize on watch key to access/increment count
	private int count;

	Event(WatchEvent.Kind<T> type, T context) {
	this.kind = type;
	this.context = context;
	this.count = 1;
	}

	@Override
	public WatchEvent.Kind<T> kind() {
	return kind;
	}

	@Override
	public T context() {
	return context;
	}

	@Override
	public int count() {
	return count;
	}

	// for repeated events
	void increment() {
	count++;
	}
	}
	}

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