/*

 * Copyright 2008-2009 Sun Microsystems, Inc.  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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package sun.nio.ch;

import java.nio.channels.*;

import java.util.*;

import sun.misc.Unsafe;

/**

 * Maintains a mapping of pending I/O requests (identified by the address of

 * an OVERLAPPED structure) to Futures.

 */

class PendingIoCache {

    private static final Unsafe unsafe = Unsafe.getUnsafe();

    private static final int addressSize = unsafe.addressSize();

    private static int dependsArch(int value32, int value64) {

        return (addressSize == 4) ? value32 : value64;

    }

    /*

     * typedef struct _OVERLAPPED {

     *     DWORD  Internal;

     *     DWORD  InternalHigh;

     *     DWORD  Offset;

     *     DWORD  OffsetHigh;

     *     HANDLE hEvent;

     * } OVERLAPPED;

     */

    private static final int SIZEOF_OVERLAPPED = dependsArch(20, 32);

    // set to true when closed

    private boolean closed;

    // set to true when thread is waiting for all I/O operations to complete

    private boolean closePending;

    // maps OVERLAPPED to PendingFuture

    private final Map<Long,PendingFuture> pendingIoMap =

        new HashMap<Long,PendingFuture>();

    // per-channel cache of OVERLAPPED structures

    private long[] overlappedCache = new long[4];

    private int overlappedCacheCount = 0;

    PendingIoCache() {

    }

    long add(PendingFuture<?,?> result) {

        synchronized (this) {

            if (closed)

                throw new AssertionError("Should not get here");

            long ov;

            if (overlappedCacheCount > 0) {

                ov = overlappedCache[--overlappedCacheCount];

            } else {

                ov = unsafe.allocateMemory(SIZEOF_OVERLAPPED);

            }

            pendingIoMap.put(ov, result);

            return ov;

        }

    }

    @SuppressWarnings("unchecked")

    <V,A> PendingFuture<V,A> remove(long overlapped) {

        synchronized (this) {

            PendingFuture<V,A> res = pendingIoMap.remove(overlapped);

            if (res != null) {

                if (overlappedCacheCount < overlappedCache.length) {

                    overlappedCache[overlappedCacheCount++] = overlapped;

                } else {

                    // cache full or channel closing

                    unsafe.freeMemory(overlapped);

                }

                // notify closing thread.

                if (closePending) {

                    this.notifyAll();

                }

            }

            return res;

        }

    }

    void close() {

        synchronized (this) {

            if (closed)

                return;

            // handle the case that where there are I/O operations that have

            // not completed.

            if (!pendingIoMap.isEmpty())

                clearPendingIoMap();

            // release memory for any cached OVERLAPPED structures

            while (overlappedCacheCount > 0) {

                unsafe.freeMemory( overlappedCache[--overlappedCacheCount] );

            }

            // done

            closed = true;

        }

    }

    private void clearPendingIoMap() {

        assert Thread.holdsLock(this);

        // wait up to 50ms for the I/O operations to complete

        closePending = true;

        try {

            this.wait(50);

        } catch (InterruptedException x) { }

        closePending = false;

        if (pendingIoMap.isEmpty())

            return;

        // cause all pending I/O operations to fail

        // simulate the failure of all pending I/O operations.

        for (Long ov: pendingIoMap.keySet()) {

            PendingFuture<?,?> result = pendingIoMap.get(ov);

            assert !result.isDone();

            // make I/O port aware of the stale OVERLAPPED structure

            Iocp iocp = (Iocp)((Groupable)result.channel()).group();

            iocp.makeStale(ov);

            // execute a task that invokes the result handler's failed method

            final Iocp.ResultHandler rh = (Iocp.ResultHandler)result.getContext();

            Runnable task = new Runnable() {

                public void run() {

                    rh.failed(-1, new AsynchronousCloseException());

                }

            };

            iocp.executeOnPooledThread(task);

        }

        pendingIoMap.clear();

    }

}