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 * Copyright (c) 2011, 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.SelectionKey;

import java.nio.channels.Selector;

import java.nio.channels.spi.SelectorProvider;

import java.util.ArrayDeque;

import java.util.Deque;

import java.util.HashMap;

import java.util.Map;

import java.util.concurrent.TimeUnit;

import java.util.function.Consumer;

import static sun.nio.ch.KQueue.EVFILT_READ;

import static sun.nio.ch.KQueue.EVFILT_WRITE;

import static sun.nio.ch.KQueue.EV_ADD;

import static sun.nio.ch.KQueue.EV_DELETE;

/**

 * KQueue based Selector implementation for macOS

 */

class KQueueSelectorImpl extends SelectorImpl {

    // maximum number of events to poll in one call to kqueue

    private static final int MAX_KEVENTS = 256;

    // kqueue file descriptor

    private final int kqfd;

    // address of poll array (event list) when polling for pending events

    private final long pollArrayAddress;

    // file descriptors used for interrupt

    private final int fd0;

    private final int fd1;

    // maps file descriptor to selection key, synchronize on selector

    private final Map<Integer, SelectionKeyImpl> fdToKey = new HashMap<>();

    // pending new registrations/updates, queued by setEventOps

    private final Object updateLock = new Object();

    private final Deque<SelectionKeyImpl> updateKeys = new ArrayDeque<>();

    // interrupt triggering and clearing

    private final Object interruptLock = new Object();

    private boolean interruptTriggered;

    // used by updateSelectedKeys to handle cases where the same file

    // descriptor is polled by more than one filter

    private int pollCount;

    KQueueSelectorImpl(SelectorProvider sp) throws IOException {

        super(sp);

        this.kqfd = KQueue.create();

        this.pollArrayAddress = KQueue.allocatePollArray(MAX_KEVENTS);

        try {

            long fds = IOUtil.makePipe(false);

            this.fd0 = (int) (fds >>> 32);

            this.fd1 = (int) fds;

        } catch (IOException ioe) {

            KQueue.freePollArray(pollArrayAddress);

            FileDispatcherImpl.closeIntFD(kqfd);

            throw ioe;

        }

        // register one end of the socket pair for wakeups

        KQueue.register(kqfd, fd0, EVFILT_READ, EV_ADD);

    }

    private void ensureOpen() {

        if (!isOpen())

            throw new ClosedSelectorException();

    }

    @Override

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

        throws IOException

    {

        assert Thread.holdsLock(this);

        long to = Math.min(timeout, Integer.MAX_VALUE);  // max kqueue timeout

        boolean blocking = (to != 0);

        boolean timedPoll = (to > 0);

        int numEntries;

        processUpdateQueue();

        processDeregisterQueue();

        try {

            begin(blocking);

            do {

                long startTime = timedPoll ? System.nanoTime() : 0;

                numEntries = KQueue.poll(kqfd, pollArrayAddress, MAX_KEVENTS, to);

                if (numEntries == IOStatus.INTERRUPTED && timedPoll) {

                    // timed poll interrupted so need to adjust timeout

                    long adjust = System.nanoTime() - startTime;

                    to -= TimeUnit.MILLISECONDS.convert(adjust, TimeUnit.NANOSECONDS);

                    if (to <= 0) {

                        // timeout expired so no retry

                        numEntries = 0;

                    }

                }

            } while (numEntries == IOStatus.INTERRUPTED);

            assert IOStatus.check(numEntries);

        } finally {

            end(blocking);

        }

        processDeregisterQueue();

        return processEvents(numEntries, action);

    }

    /**

     * Process changes to the interest ops.

     */

    private void processUpdateQueue() {

        assert Thread.holdsLock(this);

        synchronized (updateLock) {

            SelectionKeyImpl ski;

            while ((ski = updateKeys.pollFirst()) != null) {

                if (ski.isValid()) {

                    int fd = ski.getFDVal();

                    // add to fdToKey if needed

                    SelectionKeyImpl previous = fdToKey.putIfAbsent(fd, ski);

                    assert (previous == null) || (previous == ski);

                    int newEvents = ski.translateInterestOps();

                    int registeredEvents = ski.registeredEvents();

                    if (newEvents != registeredEvents) {

                        // add or delete interest in read events

                        if ((registeredEvents & Net.POLLIN) != 0) {

                            if ((newEvents & Net.POLLIN) == 0) {

                                KQueue.register(kqfd, fd, EVFILT_READ, EV_DELETE);

                            }

                        } else if ((newEvents & Net.POLLIN) != 0) {

                            KQueue.register(kqfd, fd, EVFILT_READ, EV_ADD);

                        }

                        // add or delete interest in write events

                        if ((registeredEvents & Net.POLLOUT) != 0) {

                            if ((newEvents & Net.POLLOUT) == 0) {

                                KQueue.register(kqfd, fd, EVFILT_WRITE, EV_DELETE);

                            }

                        } else if ((newEvents & Net.POLLOUT) != 0) {

                            KQueue.register(kqfd, fd, EVFILT_WRITE, EV_ADD);

                        }

                        ski.registeredEvents(newEvents);

                    }

                }

            }

        }

    }

    /**

     * Process the polled events.

     * If the interrupt fd has been selected, drain it and clear the interrupt.

     */

    private int processEvents(int numEntries, Consumer<SelectionKey> action)

        throws IOException

    {

        assert Thread.holdsLock(this);

        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 poll

        // count is incremented here and compared against the SelectionKey's

        // "lastPolled" field. This ensures that the ready ops is updated rather

        // than replaced when a file descriptor is polled by both the read and

        // write filter.

        pollCount++;

        for (int i = 0; i < numEntries; i++) {

            long kevent = KQueue.getEvent(pollArrayAddress, i);

            int fd = KQueue.getDescriptor(kevent);

            if (fd == fd0) {

                interrupted = true;

            } else {

                SelectionKeyImpl ski = fdToKey.get(fd);

                if (ski != null) {

                    int rOps = 0;

                    short filter = KQueue.getFilter(kevent);

                    if (filter == EVFILT_READ) {

                        rOps |= Net.POLLIN;

                    } else if (filter == EVFILT_WRITE) {

                        rOps |= Net.POLLOUT;

                    }

                    int updated = processReadyEvents(rOps, ski, action);

                    if (updated > 0 && ski.lastPolled != pollCount) {

                        numKeysUpdated++;

                        ski.lastPolled = pollCount;

                    }

                }

            }

        }

        if (interrupted) {

            clearInterrupt();

        }

        return numKeysUpdated;

    }

    @Override

    protected void implClose() throws IOException {

        assert !isOpen();

        assert Thread.holdsLock(this);

        // prevent further wakeup

        synchronized (interruptLock) {

            interruptTriggered = true;

        }

        FileDispatcherImpl.closeIntFD(kqfd);

        KQueue.freePollArray(pollArrayAddress);

        FileDispatcherImpl.closeIntFD(fd0);

        FileDispatcherImpl.closeIntFD(fd1);

    }

    @Override

    protected void implDereg(SelectionKeyImpl ski) throws IOException {

        assert !ski.isValid();

        assert Thread.holdsLock(this);

        int fd = ski.getFDVal();

        int registeredEvents = ski.registeredEvents();

        if (fdToKey.remove(fd) != null) {

            if (registeredEvents != 0) {

                if ((registeredEvents & Net.POLLIN) != 0)

                    KQueue.register(kqfd, fd, EVFILT_READ, EV_DELETE);

                if ((registeredEvents & Net.POLLOUT) != 0)

                    KQueue.register(kqfd, fd, EVFILT_WRITE, EV_DELETE);

                ski.registeredEvents(0);

            }

        } else {

            assert registeredEvents == 0;

        }

    }

    @Override

    public void setEventOps(SelectionKeyImpl ski) {

        ensureOpen();

        synchronized (updateLock) {

            updateKeys.addLast(ski);

        }

    }

    @Override

    public Selector wakeup() {

        synchronized (interruptLock) {

            if (!interruptTriggered) {

                try {

                    IOUtil.write1(fd1, (byte)0);

                } catch (IOException ioe) {

                    throw new InternalError(ioe);

                }

                interruptTriggered = true;

            }

        }

        return this;

    }

    private void clearInterrupt() throws IOException {

        synchronized (interruptLock) {

            IOUtil.drain(fd0);

            interruptTriggered = false;

        }

    }

}