/*

 * 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.channels.*;

import java.util.concurrent.*;

import java.nio.ByteBuffer;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.io.FileDescriptor;

import java.io.IOException;

/**

 * "Portable" implementation of AsynchronousFileChannel for use on operating

 * systems that don't support asynchronous file I/O.

 */

public class SimpleAsynchronousFileChannelImpl

    extends AsynchronousFileChannelImpl

{

    // lazy initialization of default thread pool for file I/O

    private static class DefaultExecutorHolder {

        static final ExecutorService defaultExecutor =

            ThreadPool.createDefault().executor();

    }

    // Used to make native read and write calls

    private static final FileDispatcher nd = new FileDispatcherImpl();

    // Thread-safe set of IDs of native threads, for signalling

    private final NativeThreadSet threads = new NativeThreadSet(2);

    SimpleAsynchronousFileChannelImpl(FileDescriptor fdObj,

                                      boolean reading,

                                      boolean writing,

                                      ExecutorService executor)

    {

        super(fdObj, reading, writing, executor);

    }

    public static AsynchronousFileChannel open(FileDescriptor fdo,

                                               boolean reading,

                                               boolean writing,

                                               ThreadPool pool)

    {

        // Executor is either default or based on pool parameters

        ExecutorService executor = (pool == null) ?

            DefaultExecutorHolder.defaultExecutor : pool.executor();

        return new SimpleAsynchronousFileChannelImpl(fdo, reading, writing, executor);

    }

    @Override

    public void close() throws IOException {

        // mark channel as closed

        synchronized (fdObj) {

            if (closed)

                return;     // already closed

            closed = true;

            // from this point on, if another thread invokes the begin() method

            // then it will throw ClosedChannelException

        }

        // Invalidate and release any locks that we still hold

        invalidateAllLocks();

        // signal any threads blocked on this channel

        nd.preClose(fdObj);

        threads.signalAndWait();

        // wait until all async I/O operations have completely gracefully

        closeLock.writeLock().lock();

        try {

            // do nothing

        } finally {

            closeLock.writeLock().unlock();

        }

        // close file

        nd.close(fdObj);

    }

    @Override

    public long size() throws IOException {

        int ti = threads.add();

        try {

            long n = 0L;

            try {

                begin();

                do {

                    n = nd.size(fdObj);

                } while ((n == IOStatus.INTERRUPTED) && isOpen());

                return n;

            } finally {

                end(n >= 0L);

            }

        } finally {

            threads.remove(ti);

        }

    }

    @Override

    public AsynchronousFileChannel truncate(long size) throws IOException {

        if (size < 0L)

            throw new IllegalArgumentException("Negative size");

        if (!writing)

            throw new NonWritableChannelException();

        int ti = threads.add();

        try {

            long n = 0L;

            try {

                begin();

                do {

                    n = nd.size(fdObj);

                } while ((n == IOStatus.INTERRUPTED) && isOpen());

                // truncate file if 'size' less than current size

                if (size < n && isOpen()) {

                    do {

                        n = nd.truncate(fdObj, size);

                    } while ((n == IOStatus.INTERRUPTED) && isOpen());

                }

                return this;

            } finally {

                end(n > 0);

            }

        } finally {

            threads.remove(ti);

        }

    }

    @Override

    public void force(boolean metaData) throws IOException {

        int ti = threads.add();

        try {

            int n = 0;

            try {

                begin();

                do {

                    n = nd.force(fdObj, metaData);

                } while ((n == IOStatus.INTERRUPTED) && isOpen());

            } finally {

                end(n >= 0);

            }

        } finally {

            threads.remove(ti);

        }

    }

    @Override

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

                                  final long size,

                                  final boolean shared,

                                  final A attachment,

                                  final CompletionHandler<FileLock,? super A> handler)

    {

        if (shared && !reading)

            throw new NonReadableChannelException();

        if (!shared && !writing)

            throw new NonWritableChannelException();

        // add to lock table

        final FileLockImpl fli = addToFileLockTable(position, size, shared);

        if (fli == null) {

            Throwable exc = new ClosedChannelException();

            if (handler == null)

                return CompletedFuture.withFailure(exc);

            Invoker.invokeIndirectly(handler, attachment, null, exc, executor);

            return null;

        }

        final PendingFuture<FileLock,A> result = (handler == null) ?

            new PendingFuture<FileLock,A>(this) : null;

        Runnable task = new Runnable() {

            public void run() {

                Throwable exc = null;

                int ti = threads.add();

                try {

                    int n;

                    try {

                        begin();

                        do {

                            n = nd.lock(fdObj, true, position, size, shared);

                        } while ((n == FileDispatcher.INTERRUPTED) && isOpen());

                        if (n != FileDispatcher.LOCKED || !isOpen()) {

                            throw new AsynchronousCloseException();

                        }

                    } catch (IOException x) {

                        removeFromFileLockTable(fli);

                        if (!isOpen())

                            x = new AsynchronousCloseException();

                        exc = x;

                    } finally {

                        end();

                    }

                } finally {

                    threads.remove(ti);

                }

                if (handler == null) {

                    result.setResult(fli, exc);

                } else {

                    Invoker.invokeUnchecked(handler, attachment, fli, exc);

                }

            }

        };

        boolean executed = false;

        try {

            executor.execute(task);

            executed = true;

        } finally {

            if (!executed) {

                // rollback

                removeFromFileLockTable(fli);

            }

        }

        return result;

    }

    @Override

    public FileLock tryLock(long position, long size, boolean shared)

        throws IOException

    {

        if (shared && !reading)

            throw new NonReadableChannelException();

        if (!shared && !writing)

            throw new NonWritableChannelException();

        // add to lock table

        FileLockImpl fli = addToFileLockTable(position, size, shared);

        if (fli == null)

            throw new ClosedChannelException();

        int ti = threads.add();

        boolean gotLock = false;

        try {

            begin();

            int n;

            do {

                n = nd.lock(fdObj, false, position, size, shared);

            } while ((n == FileDispatcher.INTERRUPTED) && isOpen());

            if (n == FileDispatcher.LOCKED && isOpen()) {

                gotLock = true;

                return fli;    // lock acquired

            }

            if (n == FileDispatcher.NO_LOCK)

                return null;    // locked by someone else

            if (n == FileDispatcher.INTERRUPTED)

                throw new AsynchronousCloseException();

            // should not get here

            throw new AssertionError();

        } finally {

            if (!gotLock)

                removeFromFileLockTable(fli);

            end();

            threads.remove(ti);

        }

    }

    @Override

    protected void implRelease(FileLockImpl fli) throws IOException {

        nd.release(fdObj, fli.position(), fli.size());

    }

    @Override

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

                                 final long position,

                                 final A attachment,

                                 final CompletionHandler<Integer,? super A> handler)

    {

        if (position < 0)

            throw new IllegalArgumentException("Negative position");

        if (!reading)

            throw new NonReadableChannelException();

        if (dst.isReadOnly())

            throw new IllegalArgumentException("Read-only buffer");

        // complete immediately if channel closed or no space remaining

        if (!isOpen() || (dst.remaining() == 0)) {

            Throwable exc = (isOpen()) ? null : new ClosedChannelException();

            if (handler == null)

                return CompletedFuture.withResult(0, exc);

            Invoker.invokeIndirectly(handler, attachment, 0, exc, executor);

            return null;

        }

        final PendingFuture<Integer,A> result = (handler == null) ?

            new PendingFuture<Integer,A>(this) : null;

        Runnable task = new Runnable() {

            public void run() {

                int n = 0;

                Throwable exc = null;

                int ti = threads.add();

                try {

                    begin();

                    do {

                        n = IOUtil.read(fdObj, dst, position, nd, null);

                    } while ((n == IOStatus.INTERRUPTED) && isOpen());

                    if (n < 0 && !isOpen())

                        throw new AsynchronousCloseException();

                } catch (IOException x) {

                    if (!isOpen())

                        x = new AsynchronousCloseException();

                    exc = x;

                } finally {

                    end();

                    threads.remove(ti);

                }

                if (handler == null) {

                    result.setResult(n, exc);

                } else {

                    Invoker.invokeUnchecked(handler, attachment, n, exc);

                }

            }

        };

        executor.execute(task);

        return result;

    }

    @Override

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

                                  final long position,

                                  final A attachment,

                                  final CompletionHandler<Integer,? super A> handler)

    {

        if (position < 0)

            throw new IllegalArgumentException("Negative position");

        if (!writing)

            throw new NonWritableChannelException();

        // complete immediately if channel is closed or no bytes remaining

        if (!isOpen() || (src.remaining() == 0)) {

            Throwable exc = (isOpen()) ? null : new ClosedChannelException();

            if (handler == null)

                return CompletedFuture.withResult(0, exc);

            Invoker.invokeIndirectly(handler, attachment, 0, exc, executor);

            return null;

        }

        final PendingFuture<Integer,A> result = (handler == null) ?

            new PendingFuture<Integer,A>(this) : null;

        Runnable task = new Runnable() {

            public void run() {

                int n = 0;

                Throwable exc = null;

                int ti = threads.add();

                try {

                    begin();

                    do {

                        n = IOUtil.write(fdObj, src, position, nd, null);

                    } while ((n == IOStatus.INTERRUPTED) && isOpen());

                    if (n < 0 && !isOpen())

                        throw new AsynchronousCloseException();

                } catch (IOException x) {

                    if (!isOpen())

                        x = new AsynchronousCloseException();

                    exc = x;

                } finally {

                    end();

                    threads.remove(ti);

                }

                if (handler == null) {

                    result.setResult(n, exc);

                } else {

                    Invoker.invokeUnchecked(handler, attachment, n, exc);

                }

            }

        };

        executor.execute(task);

        return result;

    }

}