/*
 * Copyright (c) 2001, 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

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.lang.ref.SoftReference;
import sun.net.ResourceManager;


An implementation of DatagramChannels.
/**
 * An implementation of DatagramChannels.
 */

class DatagramChannelImpl
    extends DatagramChannel
    implements SelChImpl
{

    // Used to make native read and write calls
    private static NativeDispatcher nd = new DatagramDispatcher();

    // Our file descriptor
    FileDescriptor fd = null;

    // 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
    int fdVal;

    // IDs of native threads doing reads and writes, for signalling
    private volatile long readerThread = 0;
    private volatile long writerThread = 0;

    // Cached InetAddress and port for unconnected DatagramChannels
    // used by receive0
    private InetAddress cachedSenderInetAddress = null;
    private int cachedSenderPort = 0;

    // 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

    // State (does not necessarily increase monotonically)
    private static final int ST_UNINITIALIZED = -1;
    private static int ST_UNCONNECTED = 0;
    private static int ST_CONNECTED = 1;
    private static final int ST_KILLED = 2;
    private int state = ST_UNINITIALIZED;

    // Binding
    private InetSocketAddress localAddress = null;
    InetSocketAddress remoteAddress = null;

    // Options
    private SocketOpts.IP options = null;

    // Our socket adaptor, if any
    private DatagramSocket socket = null;

    // -- End of fields protected by stateLock


    public DatagramChannelImpl(SelectorProvider sp)
        throws IOException
    {
        super(sp);
        ResourceManager.beforeUdpCreate();
        try {
            this.fd = Net.socket(false);
            this.fdVal = IOUtil.fdVal(fd);
            this.state = ST_UNCONNECTED;
        } catch (IOException ioe) {
            ResourceManager.afterUdpClose();
            throw ioe;
        }
    }

    public DatagramChannelImpl(SelectorProvider sp, FileDescriptor fd)
        throws IOException
    {
        super(sp);
        this.fd = fd;
        this.fdVal = IOUtil.fdVal(fd);
        this.state = ST_UNCONNECTED;
    }

    public DatagramSocket socket() {
        synchronized (stateLock) {
            if (socket == null)
                socket = DatagramSocketAdaptor.create(this);
            return socket;
        }
    }

    private void ensureOpen() throws ClosedChannelException {
        if (!isOpen())
            throw new ClosedChannelException();
    }

    private SocketAddress sender;       // Set by receive0 (## ugh)

    public SocketAddress receive(ByteBuffer dst) throws IOException {
        if (dst.isReadOnly())
            throw new IllegalArgumentException("Read-only buffer");
        if (dst == null)
            throw new NullPointerException();
        synchronized (readLock) {
            ensureOpen();
            // If socket is not bound then behave as if nothing received
            if (!isBound())             // ## NotYetBoundException ??
                return null;
            int n = 0;
            ByteBuffer bb = null;
            try {
                begin();
                if (!isOpen())
                    return null;
                SecurityManager security = System.getSecurityManager();
                readerThread = NativeThread.current();
                if (isConnected() || (security == null)) {
                    do {
                        n = receive(fd, dst);
                    } while ((n == IOStatus.INTERRUPTED) && isOpen());
                    if (n == IOStatus.UNAVAILABLE)
                        return null;
                } else {
                    bb = Util.getTemporaryDirectBuffer(dst.remaining());
                    for (;;) {
                        do {
                            n = receive(fd, bb);
                        } while ((n == IOStatus.INTERRUPTED) && isOpen());
                        if (n == IOStatus.UNAVAILABLE)
                            return null;
                        InetSocketAddress isa = (InetSocketAddress)sender;
                        try {
                            security.checkAccept(
                                isa.getAddress().getHostAddress(),
                                isa.getPort());
                        } catch (SecurityException se) {
                            // Ignore packet
                            bb.clear();
                            n = 0;
                            continue;
                        }
                        bb.flip();
                        dst.put(bb);
                        break;
                    }
                }
                return sender;
            } finally {
                if (bb != null)
                    Util.releaseTemporaryDirectBuffer(bb);
                readerThread = 0;
                end((n > 0) || (n == IOStatus.UNAVAILABLE));
                assert IOStatus.check(n);
            }
        }
    }

    private int receive(FileDescriptor fd, ByteBuffer dst)
        throws IOException
    {
        int pos = dst.position();
        int lim = dst.limit();
        assert (pos <= lim);
        int rem = (pos <= lim ? lim - pos : 0);
        if (dst instanceof DirectBuffer && rem > 0)
            return receiveIntoNativeBuffer(fd, dst, rem, pos);

        // Substitute a native buffer. If the supplied buffer is empty
        // we must instead use a nonempty buffer, otherwise the call
        // will not block waiting for a datagram on some platforms.
        int newSize = Math.max(rem, 1);
        ByteBuffer bb = null;
        try {
            bb = Util.getTemporaryDirectBuffer(newSize);
            int n = receiveIntoNativeBuffer(fd, bb, newSize, 0);
            bb.flip();
            if (n > 0 && rem > 0)
                dst.put(bb);
            return n;
        } finally {
            Util.releaseTemporaryDirectBuffer(bb);
        }
    }

    private int receiveIntoNativeBuffer(FileDescriptor fd, ByteBuffer bb,
                                        int rem, int pos)
        throws IOException
    {
        int n = receive0(fd, ((DirectBuffer)bb).address() + pos, rem,
                         isConnected());
        if (n > 0)
            bb.position(pos + n);
        return n;
    }

    public int send(ByteBuffer src, SocketAddress target)
        throws IOException
    {
        if (src == null)
            throw new NullPointerException();

        synchronized (writeLock) {
            ensureOpen();
            InetSocketAddress isa = Net.checkAddress(target);
            InetAddress ia = isa.getAddress();
            if (ia == null)
                throw new IOException("Target address not resolved");
            synchronized (stateLock) {
                if (!isConnected()) {
                    if (target == null)
                        throw new NullPointerException();
                    SecurityManager sm = System.getSecurityManager();
                    if (sm != null) {
                        if (ia.isMulticastAddress()) {
                            sm.checkMulticast(ia);
                        } else {
                            sm.checkConnect(ia.getHostAddress(),
                                            isa.getPort());
                        }
                    }
                } else { // Connected case; Check address then write
                    if (!target.equals(remoteAddress)) {
                        throw new IllegalArgumentException(
                            "Connected address not equal to target address");
                    }
                    return write(src);
                }
            }

            int n = 0;
            try {
                begin();
                if (!isOpen())
                    return 0;
                writerThread = NativeThread.current();
                do {
                    n = send(fd, src, isa);
                } while ((n == IOStatus.INTERRUPTED) && isOpen());
                return IOStatus.normalize(n);
            } finally {
                writerThread = 0;
                end((n > 0) || (n == IOStatus.UNAVAILABLE));
                assert IOStatus.check(n);
            }
        }
    }

    private int send(FileDescriptor fd, ByteBuffer src, InetSocketAddress target)
        throws IOException
    {
        if (src instanceof DirectBuffer)
            return sendFromNativeBuffer(fd, src, target);

        // Substitute a native buffer
        int pos = src.position();
        int lim = src.limit();
        assert (pos <= lim);
        int rem = (pos <= lim ? lim - pos : 0);

        ByteBuffer bb = null;
        try {
            bb = Util.getTemporaryDirectBuffer(rem);
            bb.put(src);
            bb.flip();
            // Do not update src until we see how many bytes were written
            src.position(pos);

            int n = sendFromNativeBuffer(fd, bb, target);
            if (n > 0) {
                // now update src
                src.position(pos + n);
            }
            return n;
        } finally {
            Util.releaseTemporaryDirectBuffer(bb);
        }
    }

    private int sendFromNativeBuffer(FileDescriptor fd, ByteBuffer bb,
                                     InetSocketAddress target)
        throws IOException
    {
        int pos = bb.position();
        int lim = bb.limit();
        assert (pos <= lim);
        int rem = (pos <= lim ? lim - pos : 0);

        int written = send0(fd, ((DirectBuffer)bb).address() + pos,
                            rem, target.getAddress(), target.getPort());
        if (written > 0)
            bb.position(pos + written);
        return written;
    }

    public int read(ByteBuffer buf) throws IOException {
        if (buf == null)
            throw new NullPointerException();
        synchronized (readLock) {
            synchronized (stateLock) {
                ensureOpen();
                if (!isConnected())
                    throw new NotYetConnectedException();
            }
            int n = 0;
            try {
                begin();
                if (!isOpen())
                    return 0;
                readerThread = NativeThread.current();
                do {
                    n = IOUtil.read(fd, buf, -1, nd, readLock);
                } while ((n == IOStatus.INTERRUPTED) && isOpen());
                return IOStatus.normalize(n);
            } finally {
                readerThread = 0;
                end((n > 0) || (n == IOStatus.UNAVAILABLE));
                assert IOStatus.check(n);
            }
        }
    }

    private long read0(ByteBuffer[] bufs) throws IOException {
        if (bufs == null)
            throw new NullPointerException();
        synchronized (readLock) {
            synchronized (stateLock) {
                ensureOpen();
                if (!isConnected())
                    throw new NotYetConnectedException();
            }
            long n = 0;
            try {
                begin();
                if (!isOpen())
                    return 0;
                readerThread = NativeThread.current();
                do {
                    n = IOUtil.read(fd, bufs, nd);
                } while ((n == IOStatus.INTERRUPTED) && isOpen());
                return IOStatus.normalize(n);
            } finally {
                readerThread = 0;
                end((n > 0) || (n == IOStatus.UNAVAILABLE));
                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();
        // ## Fix IOUtil.write so that we can avoid this array copy
        return read0(Util.subsequence(dsts, offset, length));
    }

    public int write(ByteBuffer buf) throws IOException {
        if (buf == null)
            throw new NullPointerException();
        synchronized (writeLock) {
            synchronized (stateLock) {
                ensureOpen();
                if (!isConnected())
                    throw new NotYetConnectedException();
            }
            int n = 0;
            try {
                begin();
                if (!isOpen())
                    return 0;
                writerThread = NativeThread.current();
                do {
                    n = IOUtil.write(fd, buf, -1, nd, writeLock);
                } while ((n == IOStatus.INTERRUPTED) && isOpen());
                return IOStatus.normalize(n);
            } finally {
                writerThread = 0;
                end((n > 0) || (n == IOStatus.UNAVAILABLE));
                assert IOStatus.check(n);
            }
        }
    }

    private long write0(ByteBuffer[] bufs) throws IOException {
        if (bufs == null)
            throw new NullPointerException();
        synchronized (writeLock) {
            synchronized (stateLock) {
                ensureOpen();
                if (!isConnected())
                    throw new NotYetConnectedException();
            }
            long n = 0;
            try {
                begin();
                if (!isOpen())
                    return 0;
                writerThread = NativeThread.current();
                do {
                    n = IOUtil.write(fd, bufs, nd);
                } while ((n == IOStatus.INTERRUPTED) && isOpen());
                return IOStatus.normalize(n);
            } finally {
                writerThread = 0;
                end((n > 0) || (n == IOStatus.UNAVAILABLE));
                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();
        // ## Fix IOUtil.write so that we can avoid this array copy
        return write0(Util.subsequence(srcs, offset, length));
    }

    protected void implConfigureBlocking(boolean block) throws IOException {
        IOUtil.configureBlocking(fd, block);
    }

    public SocketOpts options() {
        synchronized (stateLock) {
            if (options == null) {
                SocketOptsImpl.Dispatcher d
                    = new SocketOptsImpl.Dispatcher() {
                            int getInt(int opt) throws IOException {
                                return Net.getIntOption(fd, opt);
                            }
                            void setInt(int opt, int arg)
                                throws IOException
                            {
                                Net.setIntOption(fd, opt, arg);
                            }
                            boolean getIsBoundCondition()
                            {
                                return localAddress != null;
                            }
                        };
                options = new SocketOptsImpl.IP(d);
            }
            return options;
        }
    }

    public boolean isBound() {
        return Net.localPortNumber(fd) != 0;
    }

    public SocketAddress localAddress() {
        synchronized (stateLock) {
            if (isConnected() && (localAddress == null)) {
                // Socket was not bound before connecting,
                // so ask what the address turned out to be
                localAddress = Net.localAddress(fd);
            }
            SecurityManager sm = System.getSecurityManager();
            if (sm != null) {
                InetSocketAddress isa = (InetSocketAddress)localAddress;
                sm.checkConnect(isa.getAddress().getHostAddress(), -1);
            }
            return Net.getRevealedLocalAddress(localAddress);
        }
    }

    public SocketAddress remoteAddress() {
        synchronized (stateLock) {
            return remoteAddress;
        }
    }

    public void bind(SocketAddress local) throws IOException {
        synchronized (readLock) {
            synchronized (writeLock) {
                synchronized (stateLock) {
                    ensureOpen();
                    if (isBound())
                        throw new AlreadyBoundException();
                    InetSocketAddress isa = Net.checkAddress(local);
                    SecurityManager sm = System.getSecurityManager();
                    if (sm != null)
                        sm.checkListen(isa.getPort());
                    Net.bind(fd, isa.getAddress(), isa.getPort());
                    localAddress = Net.localAddress(fd);

                    // flush any packets already received.
                    boolean blocking = false;
                    synchronized (blockingLock()) {
                        try {
                            blocking = isBlocking();
                            // remainder of each packet thrown away
                            ByteBuffer tmpBuf = ByteBuffer.allocate(1);
                            if (blocking) {
                                configureBlocking(false);
                            }
                            do {
                                tmpBuf.clear();
                            } while (receive(tmpBuf) != null);
                        } finally {
                            if (blocking) {
                                configureBlocking(true);
                            }
                        }
                    }
                }
            }
        }
    }

    public boolean isConnected() {
        synchronized (stateLock) {
            return (state == ST_CONNECTED);
        }
    }

    void ensureOpenAndUnconnected() throws IOException { // package-private
        synchronized (stateLock) {
            if (!isOpen())
                throw new ClosedChannelException();
            if (state != ST_UNCONNECTED)
                throw new IllegalStateException("Connect already invoked");
        }
    }

    @Override
    public DatagramChannel connect(SocketAddress sa) throws IOException {
        int trafficClass = 0;
        int localPort = 0;

        synchronized(readLock) {
            synchronized(writeLock) {
                synchronized (stateLock) {
                    ensureOpenAndUnconnected();
                    InetSocketAddress isa = Net.checkAddress(sa);
                    SecurityManager sm = System.getSecurityManager();
                    if (sm != null)
                        sm.checkConnect(isa.getAddress().getHostAddress(),
                                        isa.getPort());
                    int n = Net.connect(fd,
                                        isa.getAddress(),
                                        isa.getPort(),
                                        trafficClass);
                    if (n <= 0)
                        throw new Error();      // Can't happen

                    // Connection succeeded; disallow further invocation
                    state = ST_CONNECTED;
                    remoteAddress = isa;
                    sender = isa;
                    cachedSenderInetAddress = isa.getAddress();
                    cachedSenderPort = isa.getPort();
                }
            }
        }
        return this;
    }

    public DatagramChannel disconnect() throws IOException {
        synchronized(readLock) {
            synchronized(writeLock) {
                synchronized (stateLock) {
                    if (!isConnected() || !isOpen())
                        return this;
                    InetSocketAddress isa = remoteAddress;
                    SecurityManager sm = System.getSecurityManager();
                    if (sm != null)
                        sm.checkConnect(isa.getAddress().getHostAddress(),
                                        isa.getPort());
                    disconnect0(fd);
                    remoteAddress = null;
                    state = ST_UNCONNECTED;
                }
            }
        }
        return this;
    }

    protected void implCloseSelectableChannel() throws IOException {
        synchronized (stateLock) {
            nd.preClose(fd);
            ResourceManager.afterUdpClose();
            long th;
            if ((th = readerThread) != 0)
                NativeThread.signal(th);
            if ((th = writerThread) != 0)
                NativeThread.signal(th);
            if (!isRegistered())
                kill();
        }
    }

    public void kill() throws IOException {
        synchronized (stateLock) {
            if (state == ST_KILLED)
                return;
            if (state == ST_UNINITIALIZED) {
                state = ST_KILLED;
                return;
            }
            assert !isOpen() && !isRegistered();
            nd.close(fd);
            state = ST_KILLED;
        }
    }

    protected void finalize() throws IOException {
        // fd is null if constructor threw exception
        if (fd != null)
            close();
    }

    
Translates native poll revent set into a ready operation set
/**
     * Translates native poll revent set into a ready operation set
     */
    public boolean translateReadyOps(int ops, int initialOps,
                                     SelectionKeyImpl sk) {
        int intOps = sk.nioInterestOps(); // Do this just once, it synchronizes
        int oldOps = sk.nioReadyOps();
        int newOps = initialOps;

        if ((ops & PollArrayWrapper.POLLNVAL) != 0) {
            // This should only happen if this channel is pre-closed while a
            // selection operation is in progress
            // ## Throw an error if this channel has not been pre-closed
            return false;
        }

        if ((ops & (PollArrayWrapper.POLLERR
                    | PollArrayWrapper.POLLHUP)) != 0) {
            newOps = intOps;
            sk.nioReadyOps(newOps);
            return (newOps & ~oldOps) != 0;
        }

        if (((ops & PollArrayWrapper.POLLIN) != 0) &&
            ((intOps & SelectionKey.OP_READ) != 0))
            newOps |= SelectionKey.OP_READ;

        if (((ops & PollArrayWrapper.POLLOUT) != 0) &&
            ((intOps & SelectionKey.OP_WRITE) != 0))
            newOps |= SelectionKey.OP_WRITE;

        sk.nioReadyOps(newOps);
        return (newOps & ~oldOps) != 0;
    }

    public boolean translateAndUpdateReadyOps(int ops, SelectionKeyImpl sk) {
        return translateReadyOps(ops, sk.nioReadyOps(), sk);
    }

    public boolean translateAndSetReadyOps(int ops, SelectionKeyImpl sk) {
        return translateReadyOps(ops, 0, sk);
    }

    
Translates an interest operation set into a native poll event set
/**
     * Translates an interest operation set into a native poll event set
     */
    public void translateAndSetInterestOps(int ops, SelectionKeyImpl sk) {
        int newOps = 0;

        if ((ops & SelectionKey.OP_READ) != 0)
            newOps |= PollArrayWrapper.POLLIN;
        if ((ops & SelectionKey.OP_WRITE) != 0)
            newOps |= PollArrayWrapper.POLLOUT;
        if ((ops & SelectionKey.OP_CONNECT) != 0)
            newOps |= PollArrayWrapper.POLLIN;
        sk.selector.putEventOps(sk, newOps);
    }

    public FileDescriptor getFD() {
        return fd;
    }

    public int getFDVal() {
        return fdVal;
    }


    // -- Native methods --

    private static native void initIDs();

    private static native void disconnect0(FileDescriptor fd)
        throws IOException;

    private native int receive0(FileDescriptor fd, long address, int len,
                                boolean connected)
        throws IOException;

    private native int send0(FileDescriptor fd, long address,
                             int len, InetAddress addr, int port)
        throws IOException;

    static {
        IOUtil.load();
        initIDs();
    }

}