/*

 * Copyright 2007-2009 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,

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 * have any questions.

 */

package java.nio.channels;

import java.nio.channels.spi.*;

import java.util.concurrent.TimeUnit;

import java.util.concurrent.Future;

import java.io.IOException;

import java.net.SocketOption;

import java.net.SocketAddress;

import java.net.ProtocolFamily;

import java.nio.ByteBuffer;

/**

 * An asynchronous channel for datagram-oriented sockets.

 *

 * <p> An asynchronous datagram channel is created by invoking one of the {@link

 * #open open} methods defined by this class. It is not possible to create a channel

 * for an arbitrary, pre-existing datagram socket. A newly-created asynchronous

 * datagram channel is open but not connected. It need not be connected in order

 * for the {@link #send send} and {@link #receive receive} methods to be used.

 * A datagram channel may be connected, by invoking its {@link #connect connect}

 * method, in order to avoid the overhead of the security checks that are otherwise

 * performed as part of every send and receive operation when a security manager

 * is set. The channel must be connected in order to use the {@link #read read}

 * and {@link #write write} methods, since those methods do not accept or return

 * socket addresses. Once connected, an asynchronous datagram channel remains

 * connected until it is disconnected or closed.

 *

 * <p> Socket options are configured using the {@link #setOption(SocketOption,Object)

 * setOption} method. An asynchronous datagram channel to an Internet Protocol

 * (IP) socket supports the following options:

 * <blockquote>

 * <table border>

 *   <tr>

 *     <th>Option Name</th>

 *     <th>Description</th>

 *   </tr>

 *   <tr>

 *     <td> {@link java.net.StandardSocketOption#SO_SNDBUF SO_SNDBUF} </td>

 *     <td> The size of the socket send buffer </td>

 *   </tr>

 *   <tr>

 *     <td> {@link java.net.StandardSocketOption#SO_RCVBUF SO_RCVBUF} </td>

 *     <td> The size of the socket receive buffer </td>

 *   </tr>

 *   <tr>

 *     <td> {@link java.net.StandardSocketOption#SO_REUSEADDR SO_REUSEADDR} </td>

 *     <td> Re-use address </td>

 *   </tr>

 *   <tr>

 *     <td> {@link java.net.StandardSocketOption#SO_BROADCAST SO_BROADCAST} </td>

 *     <td> Allow transmission of broadcast datagrams </td>

 *   </tr>

 *   <tr>

 *     <td> {@link java.net.StandardSocketOption#IP_TOS IP_TOS} </td>

 *     <td> The Type of Service (ToS) octet in the Internet Protocol (IP) header </td>

 *   </tr>

 *   <tr>

 *     <td> {@link java.net.StandardSocketOption#IP_MULTICAST_IF IP_MULTICAST_IF} </td>

 *     <td> The network interface for Internet Protocol (IP) multicast datagrams </td>

 *   </tr>

 *   <tr>

 *     <td> {@link java.net.StandardSocketOption#IP_MULTICAST_TTL

 *       IP_MULTICAST_TTL} </td>

 *     <td> The <em>time-to-live</em> for Internet Protocol (IP) multicast

 *       datagrams </td>

 *   </tr>

 *   <tr>

 *     <td> {@link java.net.StandardSocketOption#IP_MULTICAST_LOOP

 *       IP_MULTICAST_LOOP} </td>

 *     <td> Loopback for Internet Protocol (IP) multicast datagrams </td>

 *   </tr>

 * </table>

 * </blockquote>

 * Additional (implementation specific) options may also be supported.

 *

 * <p> Asynchronous datagram channels allow more than one read/receive and

 * write/send to be oustanding at any given time.

 *

 * <p> <b>Usage Example:</b>

 * <pre>

 *  final AsynchronousDatagramChannel dc = AsynchronousDatagramChannel.open()

 *      .bind(new InetSocketAddress(4000));

 *

 *  // print the source address of all packets that we receive

 *  dc.receive(buffer, buffer, new CompletionHandler<SocketAddress,ByteBuffer>() {

 *      public void completed(SocketAddress sa, ByteBuffer buffer) {

 *          try {

 *               System.out.println(sa);

 *

 *               buffer.clear();

 *               dc.receive(buffer, buffer, this);

 *           } catch (...) { ... }

 *      }

 *      public void failed(Throwable exc, ByteBuffer buffer) {

 *          ...

 *      }

 *      public void cancelled(ByteBuffer buffer) {

 *          ...

 *      }

 *  });

 * </pre>

 *

 * @since 1.7

 */

public abstract class AsynchronousDatagramChannel

    implements AsynchronousByteChannel, MulticastChannel

{

    private final AsynchronousChannelProvider provider;

    /**

     * Initializes a new instance of this class.

     */

    protected AsynchronousDatagramChannel(AsynchronousChannelProvider provider) {

        this.provider = provider;

    }

    /**

     * Returns the provider that created this channel.

     */

    public final AsynchronousChannelProvider provider() {

        return provider;

    }

    /**

     * Opens an asynchronous datagram channel.

     *

     * <p> The new channel is created by invoking the {@link

     * java.nio.channels.spi.AsynchronousChannelProvider#openAsynchronousDatagramChannel

     * openAsynchronousDatagramChannel} method on the {@link

     * java.nio.channels.spi.AsynchronousChannelProvider} object that created

     * the given group (or the default provider where {@code group} is {@code

     * null}).

     *

     * <p> The {@code family} parameter is used to specify the {@link ProtocolFamily}.

     * If the datagram channel is to be used for Internet Protocol {@link

     * MulticastChannel multicasting} then this parameter should correspond to

     * the address type of the multicast groups that this channel will join.

     *

     * @param   family

     *          The protocol family, or {@code null} to use the default protocol

     *          family

     * @param   group

     *          The group to which the newly constructed channel should be bound,

     *          or {@code null} for the default group

     *

     * @return  A new asynchronous datagram channel

     *

     * @throws  UnsupportedOperationException

     *          If the specified protocol family is not supported. For example,

     *          suppose the parameter is specified as {@link

     *          java.net.StandardProtocolFamily#INET6 INET6} but IPv6 is not

     *          enabled on the platform.

     * @throws  ShutdownChannelGroupException

     *          The specified group is shutdown

     * @throws  IOException

     *          If an I/O error occurs

     */

    public static AsynchronousDatagramChannel open(ProtocolFamily family,

                                                   AsynchronousChannelGroup group)

        throws IOException

    {

        AsynchronousChannelProvider provider = (group == null) ?

            AsynchronousChannelProvider.provider() : group.provider();

        return provider.openAsynchronousDatagramChannel(family, group);

    }

    /**

     * Opens an asynchronous datagram channel.

     *

     * <p> This method returns an asynchronous datagram channel that is

     * bound to the <em>default group</em>. This method is equivalent to evaluating

     * the expression:

     * <blockquote><pre>

     * open((ProtocolFamily)null, (AsynchronousChannelGroup)null);

     * </pre></blockquote>

     *

     * @return  A new asynchronous datagram channel

     *

     * @throws  IOException

     *          If an I/O error occurs

     */

    public static AsynchronousDatagramChannel open()

        throws IOException

    {

        return open(null, null);

    }

    // -- Socket-specific operations --

    /**

     * @throws  AlreadyBoundException               {@inheritDoc}

     * @throws  UnsupportedAddressTypeException     {@inheritDoc}

     * @throws  ClosedChannelException              {@inheritDoc}

     * @throws  IOException                         {@inheritDoc}

     * @throws  SecurityException

     *          If a security manager has been installed and its {@link

     *          SecurityManager#checkListen checkListen} method denies the

     *          operation

     */

    @Override

    public abstract AsynchronousDatagramChannel bind(SocketAddress local)

        throws IOException;

    /**

     * @throws  IllegalArgumentException                {@inheritDoc}

     * @throws  ClosedChannelException                  {@inheritDoc}

     * @throws  IOException                             {@inheritDoc}

     */

    @Override

    public abstract <T> AsynchronousDatagramChannel setOption(SocketOption<T> name, T value)

        throws IOException;

    /**

     * Returns the remote address to which this channel is connected.

     *

     * <p> Where the channel is connected to an Internet Protocol socket address

     * then the return value from this method is of type {@link

     * java.net.InetSocketAddress}.

     *

     * @return  The remote address; {@code null} if the channel's socket is not

     *          connected

     *

     * @throws  ClosedChannelException

     *          If the channel is closed

     * @throws  IOException

     *          If an I/O error occurs

     */

    public abstract SocketAddress getRemoteAddress() throws IOException;

    /**

     * Connects this channel's socket.

     *

     * <p> The channel's socket is configured so that it only receives

     * datagrams from, and sends datagrams to, the given remote <i>peer</i>

     * address.  Once connected, datagrams may not be received from or sent to

     * any other address.  A datagram socket remains connected until it is

     * explicitly disconnected or until it is closed.

     *

     * <p> This method performs exactly the same security checks as the {@link

     * java.net.DatagramSocket#connect connect} method of the {@link

     * java.net.DatagramSocket} class.  That is, if a security manager has been

     * installed then this method verifies that its {@link

     * java.lang.SecurityManager#checkAccept checkAccept} and {@link

     * java.lang.SecurityManager#checkConnect checkConnect} methods permit

     * datagrams to be received from and sent to, respectively, the given

     * remote address.

     *

     * <p> This method may be invoked at any time. Whether it has any effect

     * on outstanding read or write operations is implementation specific and

     * therefore not specified.

     *

     * @param  remote

     *         The remote address to which this channel is to be connected

     *

     * @return  This datagram channel

     *

     * @throws  ClosedChannelException

     *          If this channel is closed

     *

     * @throws  SecurityException

     *          If a security manager has been installed

     *          and it does not permit access to the given remote address

     *

     * @throws  IOException

     *          If some other I/O error occurs

     */

    public abstract AsynchronousDatagramChannel connect(SocketAddress remote)

        throws IOException;

    /**

     * Disconnects this channel's socket.

     *

     * <p> The channel's socket is configured so that it can receive datagrams

     * from, and sends datagrams to, any remote address so long as the security

     * manager, if installed, permits it.

     *

     * <p> This method may be invoked at any time. Whether it has any effect

     * on outstanding read or write operations is implementation specific and

     * therefore not specified.

     *

     * @return  This datagram channel

     *

     * @throws  IOException

     *          If some other I/O error occurs

     */

    public abstract AsynchronousDatagramChannel disconnect() throws IOException;

    /**

     * Receives a datagram via this channel.

     *

     * <p> This method initiates the receiving of a datagram, returning a

     * {@code Future} representing the pending result of the operation.

     * The {@code Future}'s {@link Future#get() get} method returns

     * the source address of the datagram upon successful completion.

     *

     * <p> The datagram is transferred into the given byte buffer starting at

     * its current position, as if by a regular {@link AsynchronousByteChannel#read

     * read} operation. If there are fewer bytes remaining in the buffer

     * than are required to hold the datagram then the remainder of the datagram

     * is silently discarded.

     *

     * <p> If a timeout is specified and the timeout elapses before the operation

     * completes then the operation completes with the exception {@link

     * InterruptedByTimeoutException}. When a timeout elapses then the state of

     * the {@link ByteBuffer} is not defined. The buffers should be discarded or

     * at least care must be taken to ensure that the buffer is not accessed

     * while the channel remains open.

     *

     * <p> When a security manager has been installed and the channel is not

     * connected, then it verifies that the source's address and port number are

     * permitted by the security manager's {@link SecurityManager#checkAccept

     * checkAccept} method. The permission check is performed with privileges that

     * are restricted by the calling context of this method. If the permission

     * check fails then the operation completes with a {@link SecurityException}.

     * The overhead of this security check can be avoided by first connecting the

     * socket via the {@link #connect connect} method.

     *

     * @param   dst

     *          The buffer into which the datagram is to be transferred

     * @param   timeout

     *          The timeout, or {@code 0L} for no timeout

     * @param   unit

     *          The time unit of the {@code timeout} argument

     * @param   attachment

     *          The object to attach to the I/O operation; can be {@code null}

     * @param   handler

     *          The handler for consuming the result; can be {@code null}

     *

     * @return  a {@code Future} object representing the pending result

     *

     * @throws  IllegalArgumentException

     *          If the timeout is negative or the buffer is read-only

     * @throws  ShutdownChannelGroupException

     *          If a handler is specified, and the channel group is shutdown

     */

    public abstract <A> Future<SocketAddress> receive(ByteBuffer dst,

                                                      long timeout,

                                                      TimeUnit unit,

                                                      A attachment,

                                                      CompletionHandler<SocketAddress,? super A> handler);

    /**

     * Receives a datagram via this channel.

     *

     * <p> This method initiates the receiving of a datagram, returning a

     * {@code Future} representing the pending result of the operation.

     * The {@code Future}'s {@link Future#get() get} method returns

     * the source address of the datagram upon successful completion.

     *

     * <p> This method is equivalent to invoking {@link

     * #receive(ByteBuffer,long,TimeUnit,Object,CompletionHandler)} with a

     * timeout of {@code 0L}.

     *

     * @param   dst

     *          The buffer into which the datagram is to be transferred

     * @param   attachment

     *          The object to attach to the I/O operation; can be {@code null}

     * @param   handler

     *          The handler for consuming the result; can be {@code null}

     *

     * @return  a {@code Future} object representing the pending result

     *

     * @throws  IllegalArgumentException

     *          If the buffer is read-only

     * @throws  ShutdownChannelGroupException

     *          If a handler is specified, and the channel group is shutdown

     */

    public final <A> Future<SocketAddress> receive(ByteBuffer dst,

                                                   A attachment,

                                                   CompletionHandler<SocketAddress,? super A> handler)

    {

        return receive(dst, 0L, TimeUnit.MILLISECONDS, attachment, handler);

    }

    /**

     * Receives a datagram via this channel.

     *

     * <p> This method initiates the receiving of a datagram, returning a

     * {@code Future} representing the pending result of the operation.

     * The {@code Future}'s {@link Future#get() get} method returns

     * the source address of the datagram upon successful completion.

     *

     * <p> This method is equivalent to invoking {@link

     * #receive(ByteBuffer,long,TimeUnit,Object,CompletionHandler)} with a

     * timeout of {@code 0L}, and an attachment and completion handler

     * of {@code null}.

     *

     * @param   dst

     *          The buffer into which the datagram is to be transferred

     *

     * @return  a {@code Future} object representing the pending result

     *

     * @throws  IllegalArgumentException

     *          If the buffer is read-only

     */

    public final <A> Future<SocketAddress> receive(ByteBuffer dst) {

        return receive(dst, 0L, TimeUnit.MILLISECONDS, null, null);

    }

    /**

     * Sends a datagram via this channel.

     *

     * <p> This method initiates sending of a datagram, returning a

     * {@code Future} representing the pending result of the operation.

     * The operation sends the remaining bytes in the given buffer as a single

     * datagram to the given target address. The result of the operation, obtained

     * by invoking the {@code Future}'s {@link Future#get() get}

     * method, is the number of bytes sent.

     *

     * <p> The datagram is transferred from the byte buffer as if by a regular

     * {@link AsynchronousByteChannel#write write} operation.

     *

     * <p> If a timeout is specified and the timeout elapses before the operation

     * completes then the operation completes with the exception {@link

     * InterruptedByTimeoutException}. When a timeout elapses then the state of

     * the {@link ByteBuffer} is not defined. The buffers should be discarded or

     * at least care must be taken to ensure that the buffer is not accessed

     * while the channel remains open.

     *

     * <p> If there is a security manager installed and the the channel is not

     * connected then this method verifies that the target address and port number

     * are permitted by the security manager's {@link SecurityManager#checkConnect

     * checkConnect} method.  The overhead of this security check can be avoided

     * by first connecting the socket via the {@link #connect connect} method.

     *

     * @param   src

     *          The buffer containing the datagram to be sent

     * @param   target

     *          The address to which the datagram is to be sent

     * @param   timeout

     *          The timeout, or {@code 0L} for no timeout

     * @param   unit

     *          The time unit of the {@code timeout} argument

     * @param   attachment

     *          The object to attach to the I/O operation; can be {@code null}

     * @param   handler

     *          The handler for consuming the result; can be {@code null}

     *

     * @return  a {@code Future} object representing the pending result

     *

     * @throws  UnresolvedAddressException

     *          If the given remote address is not fully resolved

     * @throws  UnsupportedAddressTypeException

     *          If the type of the given remote address is not supported

     * @throws  IllegalArgumentException

     *          If the timeout is negative, or if the channel's socket is

     *          connected to an address that is not equal to {@code target}

     * @throws  SecurityException

     *          If a security manager has been installed and it does not permit

     *          datagrams to be sent to the given address

     * @throws  ShutdownChannelGroupException

     *          If a handler is specified, and the channel group is shutdown

     */

    public abstract <A> Future<Integer> send(ByteBuffer src,

                                             SocketAddress target,

                                             long timeout,

                                             TimeUnit unit,

                                             A attachment,

                                             CompletionHandler<Integer,? super A> handler);

    /**

     * Sends a datagram via this channel.

     *

     * <p> This method initiates sending of a datagram, returning a

     * {@code Future} representing the pending result of the operation.

     * The operation sends the remaining bytes in the given buffer as a single

     * datagram to the given target address. The result of the operation, obtained

     * by invoking the {@code Future}'s {@link Future#get() get}

     * method, is the number of bytes sent.

     *

     * <p> This method is equivalent to invoking {@link

     * #send(ByteBuffer,SocketAddress,long,TimeUnit,Object,CompletionHandler)}

     * with a timeout of {@code 0L}.

     *

     * @param   src

     *          The buffer containing the datagram to be sent

     * @param   target

     *          The address to which the datagram is to be sent

     * @param   attachment

     *          The object to attach to the I/O operation; can be {@code null}

     * @param   handler

     *          The handler for consuming the result; can be {@code null}

     *

     * @return  a {@code Future} object representing the pending result

     *

     * @throws  UnresolvedAddressException

     *          If the given remote address is not fully resolved

     * @throws  UnsupportedAddressTypeException

     *          If the type of the given remote address is not supported

     * @throws  IllegalArgumentException

     *          If the channel's socket is connected and is connected to an

     *          address that is not equal to {@code target}

     * @throws  SecurityException

     *          If a security manager has been installed and it does not permit

     *          datagrams to be sent to the given address

     * @throws  ShutdownChannelGroupException

     *          If a handler is specified, and the channel group is shutdown

     */

    public final <A> Future<Integer> send(ByteBuffer src,

                                          SocketAddress target,

                                          A attachment,

                                          CompletionHandler<Integer,? super A> handler)

    {