/*

 * Copyright (c) 2000, 2017, 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.net.SocketException;

import java.nio.channels.ClosedSelectorException;

import java.nio.channels.IllegalSelectorException;

import java.nio.channels.SelectionKey;

import java.nio.channels.Selector;

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.Set;

/**

 * Base Selector implementation class.

 */

public abstract class SelectorImpl

    extends AbstractSelector

{

    // The set of keys with data ready for an operation

    protected Set<SelectionKey> selectedKeys;

    // The set of keys registered with this Selector

    protected HashSet<SelectionKey> keys;

    // Public views of the key sets

    private Set<SelectionKey> publicKeys;             // Immutable

    private Set<SelectionKey> publicSelectedKeys;     // Removal allowed, but not addition

    protected SelectorImpl(SelectorProvider sp) {

        super(sp);

        keys = new HashSet<>();

        selectedKeys = new HashSet<>();

        publicKeys = Collections.unmodifiableSet(keys);

        publicSelectedKeys = Util.ungrowableSet(selectedKeys);

    }

    public Set<SelectionKey> keys() {

        if (!isOpen())

            throw new ClosedSelectorException();

        return publicKeys;

    }

    public Set<SelectionKey> selectedKeys() {

        if (!isOpen())

            throw new ClosedSelectorException();

        return publicSelectedKeys;

    }

    protected abstract int doSelect(long timeout) throws IOException;

    private int lockAndDoSelect(long timeout) throws IOException {

        synchronized (this) {

            if (!isOpen())

                throw new ClosedSelectorException();

            synchronized (publicKeys) {

                synchronized (publicSelectedKeys) {

                    return doSelect(timeout);

                }

            }

        }

    }

    public int select(long timeout)

        throws IOException

    {

        if (timeout < 0)

            throw new IllegalArgumentException("Negative timeout");

        return lockAndDoSelect((timeout == 0) ? -1 : timeout);

    }

    public int select() throws IOException {

        return select(0);

    }

    public int selectNow() throws IOException {

        return lockAndDoSelect(0);

    }

    public void implCloseSelector() throws IOException {

        wakeup();

        synchronized (this) {

            synchronized (publicKeys) {

                synchronized (publicSelectedKeys) {

                    implClose();

                }

            }

        }

    }

    protected abstract void implClose() throws IOException;

    public void putEventOps(SelectionKeyImpl sk, int ops) { }

    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);

        synchronized (publicKeys) {

            implRegister(k);

        }

        k.interestOps(ops);

        return k;

    }

    protected abstract void implRegister(SelectionKeyImpl ski);

    void processDeregisterQueue() throws IOException {

        // Precondition: Synchronized on this, keys, and selectedKeys

        Set<SelectionKey> cks = cancelledKeys();

        synchronized (cks) {

            if (!cks.isEmpty()) {

                Iterator<SelectionKey> i = cks.iterator();

                while (i.hasNext()) {

                    SelectionKeyImpl ski = (SelectionKeyImpl)i.next();

                    try {

                        implDereg(ski);

                    } catch (SocketException se) {

                        throw new IOException("Error deregistering key", se);

                    } finally {

                        i.remove();

                    }

                }

            }

        }

    }

    protected abstract void implDereg(SelectionKeyImpl ski) throws IOException;

    public abstract Selector wakeup();

}