/*

 * Copyright (c) 2005, 2012, 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

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 */

package sun.nio.ch;

import java.io.IOException;

import java.nio.channels.*;

import java.nio.channels.spi.*;

import java.util.*;

import sun.misc.*;

/**

 * An implementation of Selector for Linux 2.6+ kernels that uses

 * the epoll event notification facility.

 */

class EPollSelectorImpl

    extends SelectorImpl

{

    // File descriptors used for interrupt

    protected int fd0;

    protected int fd1;

    // The poll object

    EPollArrayWrapper pollWrapper;

    // Maps from file descriptors to keys

    private Map<Integer,SelectionKeyImpl> fdToKey;

    // True if this Selector has been closed

    private volatile boolean closed = false;

    // Lock for interrupt triggering and clearing

    private final Object interruptLock = new Object();

    private boolean interruptTriggered = false;

    /**

     * Package private constructor called by factory method in

     * the abstract superclass Selector.

     */

    EPollSelectorImpl(SelectorProvider sp) throws IOException {

        super(sp);

        long pipeFds = IOUtil.makePipe(false);

        fd0 = (int) (pipeFds >>> 32);

        fd1 = (int) pipeFds;

        pollWrapper = new EPollArrayWrapper();

        pollWrapper.initInterrupt(fd0, fd1);

        fdToKey = new HashMap<>();

    }

    protected int doSelect(long timeout) throws IOException {

        if (closed)

            throw new ClosedSelectorException();

        processDeregisterQueue();

        try {

            begin();

            pollWrapper.poll(timeout);

        } finally {

            end();

        }

        processDeregisterQueue();

        int numKeysUpdated = updateSelectedKeys();

        if (pollWrapper.interrupted()) {

            // Clear the wakeup pipe

            pollWrapper.putEventOps(pollWrapper.interruptedIndex(), 0);

            synchronized (interruptLock) {

                pollWrapper.clearInterrupted();

                IOUtil.drain(fd0);

                interruptTriggered = false;

            }

        }

        return numKeysUpdated;

    }

    /**

     * Update the keys whose fd's have been selected by the epoll.

     * Add the ready keys to the ready queue.

     */

    private int updateSelectedKeys() {

        int entries = pollWrapper.updated;

        int numKeysUpdated = 0;

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

            int nextFD = pollWrapper.getDescriptor(i);

            SelectionKeyImpl ski = fdToKey.get(Integer.valueOf(nextFD));

            // ski is null in the case of an interrupt

            if (ski != null) {

                int rOps = pollWrapper.getEventOps(i);

                if (selectedKeys.contains(ski)) {

                    if (ski.channel.translateAndSetReadyOps(rOps, ski)) {

                        numKeysUpdated++;

                    }

                } else {

                    ski.channel.translateAndSetReadyOps(rOps, ski);

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

                        selectedKeys.add(ski);

                        numKeysUpdated++;

                    }

                }

            }

        }

        return numKeysUpdated;

    }

    protected void implClose() throws IOException {

        if (closed)

            return;

        closed = true;

        // prevent further wakeup

        synchronized (interruptLock) {

            interruptTriggered = true;

        }

        FileDispatcherImpl.closeIntFD(fd0);

        FileDispatcherImpl.closeIntFD(fd1);

        pollWrapper.closeEPollFD();

        // it is possible

        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();

        }

        fd0 = -1;

        fd1 = -1;

    }

    protected void implRegister(SelectionKeyImpl ski) {

        if (closed)

            throw new ClosedSelectorException();

        SelChImpl ch = ski.channel;

        int fd = Integer.valueOf(ch.getFDVal());

        fdToKey.put(fd, ski);

        pollWrapper.add(fd);

        keys.add(ski);

    }

    protected void implDereg(SelectionKeyImpl ski) throws IOException {

        assert (ski.getIndex() >= 0);

        SelChImpl ch = ski.channel;

        int fd = ch.getFDVal();

        fdToKey.remove(Integer.valueOf(fd));

        pollWrapper.remove(fd);

        ski.setIndex(-1);

        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();

        SelChImpl ch = ski.channel;

        pollWrapper.setInterest(ch.getFDVal(), ops);

    }

    public Selector wakeup() {

        synchronized (interruptLock) {

            if (!interruptTriggered) {

                pollWrapper.interrupt();

                interruptTriggered = true;

            }

        }

        return this;

    }

}