/*

 * Copyright (c) 2008, 2011, 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.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 boolean acceptPending;

    private CompletionHandler<AsynchronousSocketChannel,Object> acceptHandler;

    private Object acceptAttachment;

    private PendingFuture<AsynchronousSocketChannel,Object> acceptFuture;

    // context for permission check when security manager set

    private AccessControlContext acceptAcc;

    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);

    }

    @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

        CompletionHandler<AsynchronousSocketChannel,Object> handler;

        Object att;

        PendingFuture<AsynchronousSocketChannel,Object> future;

        synchronized (updateLock) {

            if (!acceptPending)

                return;  // no pending accept

            acceptPending = false;

            handler = acceptHandler;

            att = acceptAttachment;

            future = acceptFuture;

        }

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

        // has thrown the exception.

        AsynchronousCloseException x = new AsynchronousCloseException();

        x.setStackTrace(new StackTraceElement[0]);

        if (handler == null) {

            future.setFailure(x);

        } else {

            // invoke by submitting task rather than directly

            Invoker.invokeIndirectly(this, handler, att, null, x);

        }

    }

    @Override

    public AsynchronousChannelGroupImpl group() {

        return port;

    }

    /**

     * Invoked by event handling thread when listener socket is polled

     */

    @Override

    public void onEvent(int events, boolean mayInvokeDirect) {

        synchronized (updateLock) {

            if (!acceptPending)

                return;  // may have been grabbed by asynchronous close

            acceptPending = false;

        }

        // attempt to accept connection

        FileDescriptor newfd = new FileDescriptor();

        InetSocketAddress[] isaa = new InetSocketAddress[1];

        Throwable exc = null;

        try {

            begin();

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

            // spurious wakeup, is this possible?

            if (n == IOStatus.UNAVAILABLE) {

                synchronized (updateLock) {

                    acceptPending = true;

                }

                port.startPoll(fdVal, Port.POLLIN);

                return;

            }

        } catch (Throwable x) {

            if (x instanceof ClosedChannelException)

                x = new AsynchronousCloseException();

            exc = x;

        } finally {

            end();

        }

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

        AsynchronousSocketChannel child = null;

        if (exc == null) {

            try {

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

            } catch (Throwable x) {

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

                    x = new IOException(x);

                exc = x;

            }

        }

        // copy field befores accept is re-renabled

        CompletionHandler<AsynchronousSocketChannel,Object> handler = acceptHandler;

        Object att = acceptAttachment;

        PendingFuture<AsynchronousSocketChannel,Object> future = acceptFuture;

        // re-enable accepting and invoke handler

        enableAccept();

        if (handler == null) {

            future.setResult(child, exc);

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

            // close the new channel so as to free resources

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

                try {

                    child.close();

                } catch (IOException ignore) { }

            }

        } else {

            Invoker.invoke(this, handler, att, child, exc);

        }

    }

    /**

     * 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 (Throwable suppressed) {

                x.addSuppressed(suppressed);

            }

            throw x;

        }

        return ch;

    }

    @Override

    Future<AsynchronousSocketChannel> implAccept(Object att,

        CompletionHandler<AsynchronousSocketChannel,Object> handler)

    {

        // complete immediately if channel is closed

        if (!isOpen()) {

            Throwable e = new ClosedChannelException();

            if (handler == null) {

                return CompletedFuture.withFailure(e);

            } else {

                Invoker.invoke(this, handler, att, null, e);

                return null;

            }

        }

        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

        FileDescriptor newfd = new FileDescriptor();

        InetSocketAddress[] isaa = new InetSocketAddress[1];

        Throwable exc = null;

        try {

            begin();

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

            if (n == IOStatus.UNAVAILABLE) {

                // 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

                PendingFuture<AsynchronousSocketChannel,Object> result = null;

                synchronized (updateLock) {

                    if (handler == null) {

                        this.acceptHandler = null;

                        result = new PendingFuture<AsynchronousSocketChannel,Object>(this);

                        this.acceptFuture = result;

                    } else {

                        this.acceptHandler = handler;

                        this.acceptAttachment = att;

                    }

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

                        null : AccessController.getContext();

                    this.acceptPending = true;

                }

                // register for connections

                port.startPoll(fdVal, Port.POLLIN);

                return result;

            }

        } catch (Throwable x) {

            // accept failed

            if (x instanceof ClosedChannelException)

                x = new AsynchronousCloseException();

            exc = x;

        } finally {

            end();

        }

        AsynchronousSocketChannel child = null;

        if (exc == null) {

            // connection accepted immediately

            try {

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

            } catch (Throwable x) {

                exc = x;

            }

        }

        // re-enable accepting before invoking handler

        enableAccept();

        if (handler == null) {

            return CompletedFuture.withResult(child, exc);

        } else {

            Invoker.invokeIndirectly(this, handler, att, child, exc);

            return null;

        }

    }

    // -- 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();

    }

}