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 * Copyright (c) 2011, 2015, 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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/*
 * KQueueSelectorImpl.java
 * Implementation of Selector using FreeBSD / Mac OS X kqueues
 * Derived from Sun's DevPollSelectorImpl
 */

package sun.nio.ch;

import java.io.IOException;
import java.io.FileDescriptor;
import java.nio.channels.*;
import java.nio.channels.spi.*;
import java.util.*;
import sun.misc.*;

class KQueueSelectorImpl
    extends SelectorImpl
{
    // File descriptors used for interrupt
    protected int fd0;
    protected int fd1;

    // The kqueue manipulator
    KQueueArrayWrapper kqueueWrapper;

    // Count of registered descriptors (including interrupt)
    private int totalChannels;

    // Map from a file descriptor to an entry containing the selection key
    private HashMap<Integer,MapEntry> fdMap;

    // True if this Selector has been closed
    private boolean closed = false;

    // Lock for interrupt triggering and clearing
    private Object interruptLock = new Object();
    private boolean interruptTriggered = false;

    // used by updateSelectedKeys to handle cases where the same file
    // descriptor is polled by more than one filter
    private long updateCount;

    // Used to map file descriptors to a selection key and "update count"
    // (see updateSelectedKeys for usage).
    private static class MapEntry {
        SelectionKeyImpl ski;
        long updateCount;
        MapEntry(SelectionKeyImpl ski) {
            this.ski = ski;
        }
    }

    
Package private constructor called by factory method in
the abstract superclass Selector.
/**
     * Package private constructor called by factory method in
     * the abstract superclass Selector.
     */
    KQueueSelectorImpl(SelectorProvider sp) {
        super(sp);
        long fds = IOUtil.makePipe(false);
        fd0 = (int)(fds >>> 32);
        fd1 = (int)fds;
        try {
            kqueueWrapper = new KQueueArrayWrapper();
            kqueueWrapper.initInterrupt(fd0, fd1);
            fdMap = new HashMap<>();
            totalChannels = 1;
        } catch (Throwable t) {
            try {
                FileDispatcherImpl.closeIntFD(fd0);
            } catch (IOException ioe0) {
                t.addSuppressed(ioe0);
            }
            try {
                FileDispatcherImpl.closeIntFD(fd1);
            } catch (IOException ioe1) {
                t.addSuppressed(ioe1);
            }
            throw t;
        }
    }


    protected int doSelect(long timeout)
        throws IOException
    {
        int entries = 0;
        if (closed)
            throw new ClosedSelectorException();
        processDeregisterQueue();
        try {
            begin();
            entries = kqueueWrapper.poll(timeout);
        } finally {
            end();
        }
        processDeregisterQueue();
        return updateSelectedKeys(entries);
    }

    
Update the keys whose fd's have been selected by kqueue.
Add the ready keys to the selected key set.
If the interrupt fd has been selected, drain it and clear the interrupt.
/**
     * Update the keys whose fd's have been selected by kqueue.
     * Add the ready keys to the selected key set.
     * If the interrupt fd has been selected, drain it and clear the interrupt.
     */
    private int updateSelectedKeys(int entries)
        throws IOException
    {
        int numKeysUpdated = 0;
        boolean interrupted = false;

        // A file descriptor may be registered with kqueue with more than one
        // filter and so there may be more than one event for a fd. The update
        // count in the MapEntry tracks when the fd was last updated and this
        // ensures that the ready ops are updated rather than replaced by a
        // second or subsequent event.
        updateCount++;

        for (int i = 0; i < entries; i++) {
            int nextFD = kqueueWrapper.getDescriptor(i);
            if (nextFD == fd0) {
                interrupted = true;
            } else {
                MapEntry me = fdMap.get(Integer.valueOf(nextFD));

                // entry is null in the case of an interrupt
                if (me != null) {
                    int rOps = kqueueWrapper.getReventOps(i);
                    SelectionKeyImpl ski = me.ski;
                    if (selectedKeys.contains(ski)) {
                        // first time this file descriptor has been encountered on this
                        // update?
                        if (me.updateCount != updateCount) {
                            if (ski.channel.translateAndSetReadyOps(rOps, ski)) {
                                numKeysUpdated++;
                                me.updateCount = updateCount;
                            }
                        } else {
                            // ready ops have already been set on this update
                            ski.channel.translateAndUpdateReadyOps(rOps, ski);
                        }
                    } else {
                        ski.channel.translateAndSetReadyOps(rOps, ski);
                        if ((ski.nioReadyOps() & ski.nioInterestOps()) != 0) {
                            selectedKeys.add(ski);
                            numKeysUpdated++;
                            me.updateCount = updateCount;
                        }
                    }
                }
            }
        }

        if (interrupted) {
            // Clear the wakeup pipe
            synchronized (interruptLock) {
                IOUtil.drain(fd0);
                interruptTriggered = false;
            }
        }
        return numKeysUpdated;
    }


    protected void implClose() throws IOException {
        if (!closed) {
            closed = true;

            // prevent further wakeup
            synchronized (interruptLock) {
                interruptTriggered = true;
            }

            FileDispatcherImpl.closeIntFD(fd0);
            FileDispatcherImpl.closeIntFD(fd1);
            if (kqueueWrapper != null) {
                kqueueWrapper.close();
                kqueueWrapper = null;
                selectedKeys = null;

                // 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();
                    i.remove();
                }
                totalChannels = 0;
            }
            fd0 = -1;
            fd1 = -1;
        }
    }


    protected void implRegister(SelectionKeyImpl ski) {
        if (closed)
            throw new ClosedSelectorException();
        int fd = IOUtil.fdVal(ski.channel.getFD());
        fdMap.put(Integer.valueOf(fd), new MapEntry(ski));
        totalChannels++;
        keys.add(ski);
    }


    protected void implDereg(SelectionKeyImpl ski) throws IOException {
        int fd = ski.channel.getFDVal();
        fdMap.remove(Integer.valueOf(fd));
        kqueueWrapper.release(ski.channel);
        totalChannels--;
        keys.remove(ski);
        selectedKeys.remove(ski);
        deregister((AbstractSelectionKey)ski);
        SelectableChannel selch = ski.channel();
        if (!selch.isOpen() && !selch.isRegistered())
            ((SelChImpl)selch).kill();
    }


    public void putEventOps(SelectionKeyImpl ski, int ops) {
        if (closed)
            throw new ClosedSelectorException();
        kqueueWrapper.setInterest(ski.channel, ops);
    }


    public Selector wakeup() {
        synchronized (interruptLock) {
            if (!interruptTriggered) {
                kqueueWrapper.interrupt();
                interruptTriggered = true;
            }
        }
        return this;
    }
}