/*

 * 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.concurrent.*;

import java.io.IOException;

import java.io.FileDescriptor;

import java.net.InetSocketAddress;

import java.util.concurrent.atomic.AtomicBoolean;

import java.security.AccessControlContext;

import java.security.AccessController;

import java.security.PrivilegedAction;

/**

 * Unix implementation of AsynchronousServerSocketChannel

 */

class UnixAsynchronousServerSocketChannelImpl

    extends AsynchronousServerSocketChannelImpl

    implements Port.PollableChannel

{

    private final static NativeDispatcher nd = new SocketDispatcher();

    private final Port port;

    private final int fdVal;

    // flag to indicate an accept is outstanding

    private final AtomicBoolean accepting = new AtomicBoolean();

    private void enableAccept() {

        accepting.set(false);

    }

    // used to ensure that the context for an asynchronous accept is visible

    // the pooled thread that handles the I/O event

    private final Object updateLock = new Object();

    // pending accept

    private PendingFuture<AsynchronousSocketChannel,Object> pendingAccept;

    // context for permission check when security manager set

    private AccessControlContext acc;

    UnixAsynchronousServerSocketChannelImpl(Port port)

        throws IOException

    {

        super(port);

        try {

            IOUtil.configureBlocking(fd, false);

        } catch (IOException x) {

            nd.close(fd);  // prevent leak

            throw x;

        }

        this.port = port;

        this.fdVal = IOUtil.fdVal(fd);

        // add mapping from file descriptor to this channel

        port.register(fdVal, this);

    }

    // returns and clears the result of a pending accept

    private PendingFuture<AsynchronousSocketChannel,Object> grabPendingAccept() {

        synchronized (updateLock) {

            PendingFuture<AsynchronousSocketChannel,Object> result = pendingAccept;

            pendingAccept = null;

            return result;

        }

    }

    @Override

    void implClose() throws IOException {

        // remove the mapping

        port.unregister(fdVal);

        // close file descriptor

        nd.close(fd);

        // if there is a pending accept then complete it

        final PendingFuture<AsynchronousSocketChannel,Object> result =

            grabPendingAccept();

        if (result != null) {

            // discard the stack trace as otherwise it may appear that implClose

            // has thrown the exception.

            AsynchronousCloseException x = new AsynchronousCloseException();

            x.setStackTrace(new StackTraceElement[0]);

            result.setFailure(x);

            // invoke by submitting task rather than directly

            Invoker.invokeIndirectly(result.handler(), result);

        }

    }

    @Override

    public AsynchronousChannelGroupImpl group() {

        return port;

    }

    /**

     * Invoked by event handling thread when listener socket is polled

     */

    @Override

    public void onEvent(int events) {

        PendingFuture<AsynchronousSocketChannel,Object> result = grabPendingAccept();

        if (result == null)

            return; // may have been grabbed by asynchronous close

        // attempt to accept connection

        FileDescriptor newfd = new FileDescriptor();

        InetSocketAddress[] isaa = new InetSocketAddress[1];

        boolean accepted = false;

        try {

            begin();

            int n = accept0(this.fd, newfd, isaa);

            // spurious wakeup, is this possible?

            if (n == IOStatus.UNAVAILABLE) {

                synchronized (updateLock) {

                    this.pendingAccept = result;

                }

                port.startPoll(fdVal, Port.POLLIN);

                return;

            }

            // connection accepted

            accepted = true;

        } catch (Throwable x) {

            if (x instanceof ClosedChannelException)

                x = new AsynchronousCloseException();

            enableAccept();

            result.setFailure(x);

        } finally {

            end();

        }

        // Connection accepted so finish it when not holding locks.

        AsynchronousSocketChannel child = null;

        if (accepted) {

            try {

                child = finishAccept(newfd, isaa[0], acc);

                enableAccept();

                result.setResult(child);

            } catch (Throwable x) {

                enableAccept();

                if (!(x instanceof IOException) && !(x instanceof SecurityException))

                    x = new IOException(x);

                result.setFailure(x);

            }

        }

        // if an async cancel has already cancelled the operation then

        // close the new channel so as to free resources

        if (child != null && result.isCancelled()) {

            try {

                child.close();

            } catch (IOException ignore) { }

        }

        // invoke the handler

        Invoker.invoke(result.handler(), result);

    }

    /**

     * Completes the accept by creating the AsynchronousSocketChannel for

     * the given file descriptor and remote address. If this method completes

     * with an IOException or SecurityException then the channel/file descriptor

     * will be closed.

     */

    private AsynchronousSocketChannel finishAccept(FileDescriptor newfd,

                                                   final InetSocketAddress remote,

                                                   AccessControlContext acc)

        throws IOException, SecurityException

    {

        AsynchronousSocketChannel ch = null;

        try {

            ch = new UnixAsynchronousSocketChannelImpl(port, newfd, remote);

        } catch (IOException x) {

            nd.close(newfd);

            throw x;

        }

        // permission check must always be in initiator's context

        try {

            if (acc != null) {

                AccessController.doPrivileged(new PrivilegedAction<Void>() {

                    public Void run() {

                        SecurityManager sm = System.getSecurityManager();

                        if (sm != null) {

                            sm.checkAccept(remote.getAddress().getHostAddress(),

                                           remote.getPort());

                        }

                        return null;

                    }

                }, acc);

            } else {

                SecurityManager sm = System.getSecurityManager();

                if (sm != null) {

                    sm.checkAccept(remote.getAddress().getHostAddress(),

                                   remote.getPort());

                }

            }

        } catch (SecurityException x) {

            try {

                ch.close();

            } catch (IOException ignore) { }

            throw x;

        }

        return ch;

    }

    @Override

    @SuppressWarnings("unchecked")

    public <A> Future<AsynchronousSocketChannel> accept(A attachment,

        final CompletionHandler<AsynchronousSocketChannel,? super A> handler)

    {

        // complete immediately if channel is closed

        if (!isOpen()) {

            CompletedFuture<AsynchronousSocketChannel,A> result = CompletedFuture

                .withFailure(this, new ClosedChannelException(), attachment);

            Invoker.invokeIndirectly(handler, result);

            return result;

        }

        if (localAddress == null)

            throw new NotYetBoundException();

        // cancel was invoked with pending accept so connection may have been

        // dropped.

        if (isAcceptKilled())

            throw new RuntimeException("Accept not allowed due cancellation");

        // check and set flag to prevent concurrent accepting

        if (!accepting.compareAndSet(false, true))

            throw new AcceptPendingException();

        // attempt accept

        AbstractFuture<AsynchronousSocketChannel,A> result = null;

        FileDescriptor newfd = new FileDescriptor();

        InetSocketAddress[] isaa = new InetSocketAddress[1];

        try {

            begin();

            int n = accept0(this.fd, newfd, isaa);

            if (n == IOStatus.UNAVAILABLE) {

                // no connection to accept

                result = new PendingFuture<AsynchronousSocketChannel,A>(this, handler, attachment);

                // need calling context when there is security manager as

                // permission check may be done in a different thread without

                // any application call frames on the stack

                synchronized (this) {

                    this.acc = (System.getSecurityManager() == null) ?

                        null : AccessController.getContext();

                    this.pendingAccept =

                        (PendingFuture<AsynchronousSocketChannel,Object>)result;

                }

                // register for connections

                port.startPoll(fdVal, Port.POLLIN);

                return result;

            }

        } catch (Throwable x) {

            // accept failed

            if (x instanceof ClosedChannelException)

                x = new AsynchronousCloseException();

            result = CompletedFuture.withFailure(this, x, attachment);

        } finally {

            end();

        }

        // connection accepted immediately

        if (result == null) {

            try {

                AsynchronousSocketChannel ch = finishAccept(newfd, isaa[0], null);

                result = CompletedFuture.withResult(this, ch, attachment);

            } catch (Throwable x) {

                result = CompletedFuture.withFailure(this, x, attachment);

            }

        }

        // re-enable accepting and invoke handler

        enableAccept();

        Invoker.invokeIndirectly(handler, result);

        return result;

    }

    // -- Native methods --

    private static native void initIDs();

    // Accepts a new connection, setting the given file descriptor to refer to

    // the new socket and setting isaa[0] to the socket's remote address.

    // Returns 1 on success, or IOStatus.UNAVAILABLE.

    //

    private native int accept0(FileDescriptor ssfd, FileDescriptor newfd,

                               InetSocketAddress[] isaa)

        throws IOException;

    static {

        Util.load();

        initIDs();

    }

}