/*

 * Copyright (c) 2000, 2016, 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.io.FileDescriptor;

import java.io.IOException;

import java.net.*;

import java.nio.ByteBuffer;

import java.nio.channels.*;

import java.nio.channels.spi.*;

import java.util.*;

import sun.net.NetHooks;

import sun.net.ext.ExtendedSocketOptions;

/**

 * An implementation of SocketChannels

 */

class SocketChannelImpl

    extends SocketChannel

    implements SelChImpl

{

    // Used to make native read and write calls

    private static NativeDispatcher nd;

    // Our file descriptor object

    private final FileDescriptor fd;

    // fd value needed for dev/poll. This value will remain valid

    // even after the value in the file descriptor object has been set to -1

    private final int fdVal;

    // IDs of native threads doing reads and writes, for signalling

    private volatile long readerThread;

    private volatile long writerThread;

    // Lock held by current reading or connecting thread

    private final Object readLock = new Object();

    // Lock held by current writing or connecting thread

    private final Object writeLock = new Object();

    // Lock held by any thread that modifies the state fields declared below

    // DO NOT invoke a blocking I/O operation while holding this lock!

    private final Object stateLock = new Object();

    // -- The following fields are protected by stateLock

    // set true when exclusive binding is on and SO_REUSEADDR is emulated

    private boolean isReuseAddress;

    // State, increases monotonically

    private static final int ST_UNINITIALIZED = -1;

    private static final int ST_UNCONNECTED = 0;

    private static final int ST_PENDING = 1;

    private static final int ST_CONNECTED = 2;

    private static final int ST_KILLPENDING = 3;

    private static final int ST_KILLED = 4;

    private int state = ST_UNINITIALIZED;

    // Binding

    private InetSocketAddress localAddress;

    private InetSocketAddress remoteAddress;

    // Input/Output open

    private boolean isInputOpen = true;

    private boolean isOutputOpen = true;

    private boolean readyToConnect = false;

    // Socket adaptor, created on demand

    private Socket socket;

    // -- End of fields protected by stateLock

    // Constructor for normal connecting sockets

    //

    SocketChannelImpl(SelectorProvider sp) throws IOException {

        super(sp);

        this.fd = Net.socket(true);

        this.fdVal = IOUtil.fdVal(fd);

        this.state = ST_UNCONNECTED;

    }

    SocketChannelImpl(SelectorProvider sp,

                      FileDescriptor fd,

                      boolean bound)

        throws IOException

    {

        super(sp);

        this.fd = fd;

        this.fdVal = IOUtil.fdVal(fd);

        this.state = ST_UNCONNECTED;

        if (bound)

            this.localAddress = Net.localAddress(fd);

    }

    // Constructor for sockets obtained from server sockets

    //

    SocketChannelImpl(SelectorProvider sp,

                      FileDescriptor fd, InetSocketAddress remote)

        throws IOException

    {

        super(sp);

        this.fd = fd;

        this.fdVal = IOUtil.fdVal(fd);

        this.state = ST_CONNECTED;

        this.localAddress = Net.localAddress(fd);

        this.remoteAddress = remote;

    }

    public Socket socket() {

        synchronized (stateLock) {

            if (socket == null)

                socket = SocketAdaptor.create(this);

            return socket;

        }

    }

    @Override

    public SocketAddress getLocalAddress() throws IOException {

        synchronized (stateLock) {

            if (!isOpen())

                throw new ClosedChannelException();

            return  Net.getRevealedLocalAddress(localAddress);

        }

    }

    @Override

    public SocketAddress getRemoteAddress() throws IOException {

        synchronized (stateLock) {

            if (!isOpen())

                throw new ClosedChannelException();

            return remoteAddress;

        }

    }

    @Override

    public <T> SocketChannel setOption(SocketOption<T> name, T value)

        throws IOException

    {

        if (name == null)

            throw new NullPointerException();

        if (!supportedOptions().contains(name))

            throw new UnsupportedOperationException("'" + name + "' not supported");

        synchronized (stateLock) {

            if (!isOpen())

                throw new ClosedChannelException();

            if (name == StandardSocketOptions.IP_TOS) {

                ProtocolFamily family = Net.isIPv6Available() ?

                    StandardProtocolFamily.INET6 : StandardProtocolFamily.INET;

                Net.setSocketOption(fd, family, name, value);

                return this;

            }

            if (name == StandardSocketOptions.SO_REUSEADDR && Net.useExclusiveBind()) {

                // SO_REUSEADDR emulated when using exclusive bind

                isReuseAddress = (Boolean)value;

                return this;

            }

            // no options that require special handling

            Net.setSocketOption(fd, Net.UNSPEC, name, value);

            return this;

        }

    }

    @Override

    @SuppressWarnings("unchecked")

    public <T> T getOption(SocketOption<T> name)

        throws IOException

    {

        if (name == null)

            throw new NullPointerException();

        if (!supportedOptions().contains(name))

            throw new UnsupportedOperationException("'" + name + "' not supported");

        synchronized (stateLock) {

            if (!isOpen())

                throw new ClosedChannelException();

            if (name == StandardSocketOptions.SO_REUSEADDR &&

                    Net.useExclusiveBind())

            {

                // SO_REUSEADDR emulated when using exclusive bind

                return (T)Boolean.valueOf(isReuseAddress);

            }

            // special handling for IP_TOS: always return 0 when IPv6

            if (name == StandardSocketOptions.IP_TOS) {

                ProtocolFamily family = Net.isIPv6Available() ?

                    StandardProtocolFamily.INET6 : StandardProtocolFamily.INET;

                return (T) Net.getSocketOption(fd, family, name);

            }

            // no options that require special handling

            return (T) Net.getSocketOption(fd, Net.UNSPEC, name);

        }

    }

    private static class DefaultOptionsHolder {

        static final Set<SocketOption<?>> defaultOptions = defaultOptions();

        private static Set<SocketOption<?>> defaultOptions() {

            HashSet<SocketOption<?>> set = new HashSet<>(8);

            set.add(StandardSocketOptions.SO_SNDBUF);

            set.add(StandardSocketOptions.SO_RCVBUF);

            set.add(StandardSocketOptions.SO_KEEPALIVE);

            set.add(StandardSocketOptions.SO_REUSEADDR);

            if (Net.isReusePortAvailable()) {

                set.add(StandardSocketOptions.SO_REUSEPORT);

            }

            set.add(StandardSocketOptions.SO_LINGER);

            set.add(StandardSocketOptions.TCP_NODELAY);

            // additional options required by socket adaptor

            set.add(StandardSocketOptions.IP_TOS);

            set.add(ExtendedSocketOption.SO_OOBINLINE);

            ExtendedSocketOptions extendedOptions =

                    ExtendedSocketOptions.getInstance();

            set.addAll(extendedOptions.options());

            return Collections.unmodifiableSet(set);

        }

    }

    @Override

    public final Set<SocketOption<?>> supportedOptions() {

        return DefaultOptionsHolder.defaultOptions;

    }

    private boolean ensureReadOpen() throws ClosedChannelException {

        synchronized (stateLock) {

            if (!isOpen())

                throw new ClosedChannelException();

            if (!isConnected())

                throw new NotYetConnectedException();

            if (!isInputOpen)

                return false;

            else

                return true;

        }

    }

    private void ensureWriteOpen() throws ClosedChannelException {

        synchronized (stateLock) {

            if (!isOpen())

                throw new ClosedChannelException();

            if (!isOutputOpen)

                throw new ClosedChannelException();

            if (!isConnected())

                throw new NotYetConnectedException();

        }

    }

    private void readerCleanup() throws IOException {

        synchronized (stateLock) {

            readerThread = 0;

            if (state == ST_KILLPENDING)

                kill();

        }

    }

    private void writerCleanup() throws IOException {

        synchronized (stateLock) {

            writerThread = 0;

            if (state == ST_KILLPENDING)

                kill();

        }

    }

    public int read(ByteBuffer buf) throws IOException {

        if (buf == null)

            throw new NullPointerException();

        synchronized (readLock) {

            if (!ensureReadOpen())

                return -1;

            int n = 0;

            try {

                // Set up the interruption machinery; see

                // AbstractInterruptibleChannel for details

                //

                begin();

                synchronized (stateLock) {

                    if (!isOpen()) {

                    // Either the current thread is already interrupted, so

                    // begin() closed the channel, or another thread closed the

                    // channel since we checked it a few bytecodes ago.  In

                    // either case the value returned here is irrelevant since

                    // the invocation of end() in the finally block will throw

                    // an appropriate exception.

                    //

                        return 0;

                    }

                    // Save this thread so that it can be signalled on those

                    // platforms that require it

                    //

                    readerThread = NativeThread.current();

                }

                // Between the previous test of isOpen() and the return of the

                // IOUtil.read invocation below, this channel might be closed

                // or this thread might be interrupted.  We rely upon the

                // implicit synchronization point in the kernel read() call to

                // make sure that the right thing happens.  In either case the

                // implCloseSelectableChannel method is ultimately invoked in

                // some other thread, so there are three possibilities:

                //

                //   - implCloseSelectableChannel() invokes nd.preClose()

                //     before this thread invokes read(), in which case the

                //     read returns immediately with either EOF or an error,

                //     the latter of which will cause an IOException to be

                //     thrown.

                //

                //   - implCloseSelectableChannel() invokes nd.preClose() after

                //     this thread is blocked in read().  On some operating

                //     systems (e.g., Solaris and Windows) this causes the read

                //     to return immediately with either EOF or an error

                //     indication.

                //

                //   - implCloseSelectableChannel() invokes nd.preClose() after

                //     this thread is blocked in read() but the operating

                //     system (e.g., Linux) doesn't support preemptive close,

                //     so implCloseSelectableChannel() proceeds to signal this

                //     thread, thereby causing the read to return immediately

                //     with IOStatus.INTERRUPTED.

                //

                // In all three cases the invocation of end() in the finally

                // clause will notice that the channel has been closed and

                // throw an appropriate exception (AsynchronousCloseException

                // or ClosedByInterruptException) if necessary.

                //

                // *There is A fourth possibility. implCloseSelectableChannel()

                // invokes nd.preClose(), signals reader/writer thred and quickly

                // moves on to nd.close() in kill(), which does a real close.

                // Then a third thread accepts a new connection, opens file or

                // whatever that causes the released "fd" to be recycled. All

                // above happens just between our last isOpen() check and the

                // next kernel read reached, with the recycled "fd". The solution

                // is to postpone the real kill() if there is a reader or/and

                // writer thread(s) over there "waiting", leave the cleanup/kill

                // to the reader or writer thread. (the preClose() still happens

                // so the connection gets cut off as usual).

                //

                // For socket channels there is the additional wrinkle that

                // asynchronous shutdown works much like asynchronous close,

                // except that the channel is shutdown rather than completely

                // closed.  This is analogous to the first two cases above,

                // except that the shutdown operation plays the role of

                // nd.preClose().

                for (;;) {

                    n = IOUtil.read(fd, buf, -1, nd);

                    if ((n == IOStatus.INTERRUPTED) && isOpen()) {

                        // The system call was interrupted but the channel

                        // is still open, so retry

                        continue;

                    }

                    return IOStatus.normalize(n);

                }

            } finally {

                readerCleanup();        // Clear reader thread

                // The end method, which is defined in our superclass

                // AbstractInterruptibleChannel, resets the interruption

                // machinery.  If its argument is true then it returns

                // normally; otherwise it checks the interrupt and open state

                // of this channel and throws an appropriate exception if

                // necessary.

                //

                // So, if we actually managed to do any I/O in the above try

                // block then we pass true to the end method.  We also pass

                // true if the channel was in non-blocking mode when the I/O

                // operation was initiated but no data could be transferred;

                // this prevents spurious exceptions from being thrown in the

                // rare event that a channel is closed or a thread is

                // interrupted at the exact moment that a non-blocking I/O

                // request is made.

                //

                end(n > 0 || (n == IOStatus.UNAVAILABLE));

                // Extra case for socket channels: Asynchronous shutdown

                //

                synchronized (stateLock) {

                    if ((n <= 0) && (!isInputOpen))

                        return IOStatus.EOF;

                }

                assert IOStatus.check(n);

            }

        }

    }

    public long read(ByteBuffer[] dsts, int offset, int length)

        throws IOException

    {

        if ((offset < 0) || (length < 0) || (offset > dsts.length - length))

            throw new IndexOutOfBoundsException();

        synchronized (readLock) {

            if (!ensureReadOpen())

                return -1;

            long n = 0;

            try {

                begin();

                synchronized (stateLock) {

                    if (!isOpen())

                        return 0;

                    readerThread = NativeThread.current();

                }

                for (;;) {

                    n = IOUtil.read(fd, dsts, offset, length, nd);

                    if ((n == IOStatus.INTERRUPTED) && isOpen())

                        continue;

                    return IOStatus.normalize(n);

                }

            } finally {

                readerCleanup();

                end(n > 0 || (n == IOStatus.UNAVAILABLE));

                synchronized (stateLock) {

                    if ((n <= 0) && (!isInputOpen))

                        return IOStatus.EOF;

                }

                assert IOStatus.check(n);

            }

        }

    }

    public int write(ByteBuffer buf) throws IOException {

        if (buf == null)

            throw new NullPointerException();

        synchronized (writeLock) {

            ensureWriteOpen();

            int n = 0;

            try {

                begin();

                synchronized (stateLock) {

                    if (!isOpen())

                        return 0;

                    writerThread = NativeThread.current();

                }

                for (;;) {

                    n = IOUtil.write(fd, buf, -1, nd);

                    if ((n == IOStatus.INTERRUPTED) && isOpen())

                        continue;

                    return IOStatus.normalize(n);

                }

            } finally {

                writerCleanup();

                end(n > 0 || (n == IOStatus.UNAVAILABLE));

                synchronized (stateLock) {

                    if ((n <= 0) && (!isOutputOpen))

                        throw new AsynchronousCloseException();

                }

                assert IOStatus.check(n);

            }

        }

    }

    public long write(ByteBuffer[] srcs, int offset, int length)

        throws IOException

    {

        if ((offset < 0) || (length < 0) || (offset > srcs.length - length))

            throw new IndexOutOfBoundsException();

        synchronized (writeLock) {

            ensureWriteOpen();

            long n = 0;

            try {

                begin();

                synchronized (stateLock) {

                    if (!isOpen())

                        return 0;

                    writerThread = NativeThread.current();

                }

                for (;;) {

                    n = IOUtil.write(fd, srcs, offset, length, nd);

                    if ((n == IOStatus.INTERRUPTED) && isOpen())

                        continue;

                    return IOStatus.normalize(n);

                }

            } finally {

                writerCleanup();

                end((n > 0) || (n == IOStatus.UNAVAILABLE));