/*

 * Copyright (c) 2008, 2009, 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

 * questions.

 */

package sun.nio.ch;

import java.nio.ByteBuffer;

import java.nio.channels.*;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Future;

import java.util.concurrent.locks.*;

import java.io.FileDescriptor;

import java.io.IOException;

/**

 * Base implementation of AsynchronousFileChannel.

 */

abstract class AsynchronousFileChannelImpl

    extends AsynchronousFileChannel

{

    // close support

    protected final ReadWriteLock closeLock = new ReentrantReadWriteLock();

    protected volatile boolean closed;

    // file descriptor

    protected final FileDescriptor fdObj;

    // indicates if open for reading/writing

    protected final boolean reading;

    protected final boolean writing;

    // associated Executor

    protected final ExecutorService executor;

    protected AsynchronousFileChannelImpl(FileDescriptor fdObj,

                                          boolean reading,

                                          boolean writing,

                                          ExecutorService executor)

    {

        this.fdObj = fdObj;

        this.reading = reading;

        this.writing = writing;

        this.executor = executor;

    }

    final ExecutorService executor() {

        return executor;

    }

    @Override

    public final boolean isOpen() {

        return !closed;

    }

    /**

     * Marks the beginning of an I/O operation.

     *

     * @throws  ClosedChannelException  If channel is closed

     */

    protected final void begin() throws IOException {

        closeLock.readLock().lock();

        if (closed)

            throw new ClosedChannelException();

    }

    /**

     * Marks the end of an I/O operation.

     */

    protected final void end() {

        closeLock.readLock().unlock();

    }

    /**

     * Marks end of I/O operation

     */

    protected final void end(boolean completed) throws IOException {

        end();

        if (!completed && !isOpen())

            throw new AsynchronousCloseException();

    }

    // -- file locking --

    abstract <A> Future<FileLock> implLock(long position,

                                           long size,

                                           boolean shared,

                                           A attachment,

                                           CompletionHandler<FileLock,? super A> handler);

    @Override

    public final Future<FileLock> lock(long position,

                                       long size,

                                       boolean shared)

    {

        return implLock(position, size, shared, null, null);

    }

    @Override

    public final <A> void lock(long position,

                               long size,

                               boolean shared,

                               A attachment,

                               CompletionHandler<FileLock,? super A> handler)

    {

        if (handler == null)

            throw new NullPointerException("'handler' is null");

        implLock(position, size, shared, attachment, handler);

    }

    private volatile FileLockTable fileLockTable;

    final void ensureFileLockTableInitialized() throws IOException {

        if (fileLockTable == null) {

            synchronized (this) {

                if (fileLockTable == null) {

                    fileLockTable = FileLockTable.newSharedFileLockTable(this, fdObj);

                }

            }

        }

    }

    final void invalidateAllLocks() throws IOException {

        if (fileLockTable != null) {

            for (FileLock fl: fileLockTable.removeAll()) {

                synchronized (fl) {

                    if (fl.isValid()) {

                        FileLockImpl fli = (FileLockImpl)fl;

                        implRelease(fli);

                        fli.invalidate();

                    }

                }

            }

        }

    }

    /**

     * Adds region to lock table

     */

    protected final FileLockImpl addToFileLockTable(long position, long size, boolean shared) {

        final FileLockImpl fli;

        try {

            // like begin() but returns null instead of exception

            closeLock.readLock().lock();

            if (closed)

                return null;

            try {

                ensureFileLockTableInitialized();

            } catch (IOException x) {

                // should not happen

                throw new AssertionError(x);

            }

            fli = new FileLockImpl(this, position, size, shared);

            // may throw OverlappedFileLockException

            fileLockTable.add(fli);

        } finally {

            end();

        }

        return fli;

    }

    protected final void removeFromFileLockTable(FileLockImpl fli) {

        fileLockTable.remove(fli);

    }

    /**

     * Releases the given file lock.

     */

    protected abstract void implRelease(FileLockImpl fli) throws IOException;

    /**

     * Invoked by FileLockImpl to release the given file lock and remove it

     * from the lock table.

     */

    final void release(FileLockImpl fli) throws IOException {

        try {

            begin();

            implRelease(fli);

            removeFromFileLockTable(fli);

        } finally {

            end();

        }

    }

    // -- reading and writing --

    abstract <A> Future<Integer> implRead(ByteBuffer dst,

                                         long position,

                                         A attachment,

                                         CompletionHandler<Integer,? super A> handler);

    @Override

    public final Future<Integer> read(ByteBuffer dst, long position) {

        return implRead(dst, position, null, null);

    }

    @Override

    public final <A> void read(ByteBuffer dst,

                               long position,

                               A attachment,

                               CompletionHandler<Integer,? super A> handler)

    {

        if (handler == null)

            throw new NullPointerException("'handler' is null");

        implRead(dst, position, attachment, handler);

    }

    abstract <A> Future<Integer> implWrite(ByteBuffer src,

                                           long position,

                                           A attachment,

                                           CompletionHandler<Integer,? super A> handler);

    @Override

    public final Future<Integer> write(ByteBuffer src, long position) {

        return implWrite(src, position, null, null);

    }

    @Override

    public final <A> void write(ByteBuffer src,

                                long position,

                                A attachment,

                                CompletionHandler<Integer,? super A> handler)

    {

        if (handler == null)

            throw new NullPointerException("'handler' is null");

        implWrite(src, position, attachment, handler);

    }

}