/*

 * Copyright 2000-2001 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 java.nio.channels;

import java.io.IOException;

import java.net.Socket;

import java.net.SocketAddress;

import java.nio.ByteBuffer;

import java.nio.channels.spi.*;

/**

 * A selectable channel for stream-oriented connecting sockets.

 *

 * <p> Socket channels are not a complete abstraction of connecting network

 * sockets.  Binding, shutdown, and the manipulation of socket options must be

 * done through an associated {@link java.net.Socket} object obtained by

 * invoking the {@link #socket() socket} method.  It is not possible to create

 * a channel for an arbitrary, pre-existing socket, nor is it possible to

 * specify the {@link java.net.SocketImpl} object to be used by a socket

 * associated with a socket channel.

 *

 * <p> A socket channel is created by invoking one of the {@link #open open}

 * methods of this class.  A newly-created socket channel is open but not yet

 * connected.  An attempt to invoke an I/O operation upon an unconnected

 * channel will cause a {@link NotYetConnectedException} to be thrown.  A

 * socket channel can be connected by invoking its {@link #connect connect}

 * method; once connected, a socket channel remains connected until it is

 * closed.  Whether or not a socket channel is connected may be determined by

 * invoking its {@link #isConnected isConnected} method.

 *

 * <p> Socket channels support <i>non-blocking connection:</i>&nbsp;A socket

 * channel may be created and the process of establishing the link to the

 * remote socket may be initiated via the {@link #connect connect} method for

 * later completion by the {@link #finishConnect finishConnect} method.

 * Whether or not a connection operation is in progress may be determined by

 * invoking the {@link #isConnectionPending isConnectionPending} method.

 *

 * <p> The input and output sides of a socket channel may independently be

 * <i>shut down</i> without actually closing the channel.  Shutting down the

 * input side of a channel by invoking the {@link java.net.Socket#shutdownInput

 * shutdownInput} method of an associated socket object will cause further

 * reads on the channel to return <tt>-1</tt>, the end-of-stream indication.

 * Shutting down the output side of the channel by invoking the {@link

 * java.net.Socket#shutdownOutput shutdownOutput} method of an associated

 * socket object will cause further writes on the channel to throw a {@link

 * ClosedChannelException}.

 *

 * <p> Socket channels support <i>asynchronous shutdown,</i> which is similar

 * to the asynchronous close operation specified in the {@link Channel} class.

 * If the input side of a socket is shut down by one thread while another

 * thread is blocked in a read operation on the socket's channel, then the read

 * operation in the blocked thread will complete without reading any bytes and

 * will return <tt>-1</tt>.  If the output side of a socket is shut down by one

 * thread while another thread is blocked in a write operation on the socket's

 * channel, then the blocked thread will receive an {@link

 * AsynchronousCloseException}.

 *

 * <p> Socket channels are safe for use by multiple concurrent threads.  They

 * support concurrent reading and writing, though at most one thread may be

 * reading and at most one thread may be writing at any given time.  The {@link

 * #connect connect} and {@link #finishConnect finishConnect} methods are

 * mutually synchronized against each other, and an attempt to initiate a read

 * or write operation while an invocation of one of these methods is in

 * progress will block until that invocation is complete.  </p>

 *

 *

 * @author Mark Reinhold

 * @author JSR-51 Expert Group

 * @since 1.4

 */

public abstract class SocketChannel

    extends AbstractSelectableChannel

    implements ByteChannel, ScatteringByteChannel, GatheringByteChannel

{

    /**

     * Initializes a new instance of this class.

     */

    protected SocketChannel(SelectorProvider provider) {

        super(provider);

    }

    /**

     * Opens a socket channel.

     *

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

     * java.nio.channels.spi.SelectorProvider#openSocketChannel

     * openSocketChannel} method of the system-wide default {@link

     * java.nio.channels.spi.SelectorProvider} object.  </p>

     *

     * @return  A new socket channel

     *

     * @throws  IOException

     *          If an I/O error occurs

     */

    public static SocketChannel open() throws IOException {

        return SelectorProvider.provider().openSocketChannel();

    }

    /**

     * Opens a socket channel and connects it to a remote address.

     *

     * <p> This convenience method works as if by invoking the {@link #open()}

     * method, invoking the {@link #connect(SocketAddress) connect} method upon

     * the resulting socket channel, passing it <tt>remote</tt>, and then

     * returning that channel.  </p>

     *

     * @param  remote

     *         The remote address to which the new channel is to be connected

     *

     * @throws  AsynchronousCloseException

     *          If another thread closes this channel

     *          while the connect operation is in progress

     *

     * @throws  ClosedByInterruptException

     *          If another thread interrupts the current thread

     *          while the connect operation is in progress, thereby

     *          closing the channel and setting the current thread's

     *          interrupt status

     *

     * @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  SecurityException

     *          If a security manager has been installed

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

     *

     * @throws  IOException

     *          If some other I/O error occurs

     */

    public static SocketChannel open(SocketAddress remote)

        throws IOException

    {

        SocketChannel sc = open();

        try {

            sc.connect(remote);

        } finally {

            if (!sc.isConnected()) {

                try { sc.close(); } catch (IOException x) { }

            }

        }

        assert sc.isConnected();

        return sc;

    }

    /**

     * Returns an operation set identifying this channel's supported

     * operations.

     *

     * <p> Socket channels support connecting, reading, and writing, so this

     * method returns <tt>(</tt>{@link SelectionKey#OP_CONNECT}

     * <tt>|</tt>&nbsp;{@link SelectionKey#OP_READ} <tt>|</tt>&nbsp;{@link

     * SelectionKey#OP_WRITE}<tt>)</tt>.  </p>

     *

     * @return  The valid-operation set

     */

    public final int validOps() {

        return (SelectionKey.OP_READ

                | SelectionKey.OP_WRITE

                | SelectionKey.OP_CONNECT);

    }

    // -- Socket-specific operations --

    /**

     * Retrieves a socket associated with this channel.

     *

     * <p> The returned object will not declare any public methods that are not

     * declared in the {@link java.net.Socket} class.  </p>

     *

     * @return  A socket associated with this channel

     */

    public abstract Socket socket();

    /**

     * Tells whether or not this channel's network socket is connected.  </p>

     *

     * @return  <tt>true</tt> if, and only if, this channel's network socket

     *          is connected

     */

    public abstract boolean isConnected();

    /**

     * Tells whether or not a connection operation is in progress on this

     * channel.  </p>

     *

     * @return  <tt>true</tt> if, and only if, a connection operation has been

     *          initiated on this channel but not yet completed by invoking the

     *          {@link #finishConnect finishConnect} method

     */

    public abstract boolean isConnectionPending();

    /**

     * Connects this channel's socket.

     *

     * <p> If this channel is in non-blocking mode then an invocation of this

     * method initiates a non-blocking connection operation.  If the connection

     * is established immediately, as can happen with a local connection, then

     * this method returns <tt>true</tt>.  Otherwise this method returns

     * <tt>false</tt> and the connection operation must later be completed by

     * invoking the {@link #finishConnect finishConnect} method.

     *

     * <p> If this channel is in blocking mode then an invocation of this

     * method will block until the connection is established or an I/O error

     * occurs.

     *

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

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

     * installed then this method verifies that its {@link

     * java.lang.SecurityManager#checkConnect checkConnect} method permits

     * connecting to the address and port number of the given remote endpoint.

     *

     * <p> This method may be invoked at any time.  If a read or write

     * operation upon this channel is invoked while an invocation of this

     * method is in progress then that operation will first block until this

     * invocation is complete.  If a connection attempt is initiated but fails,

     * that is, if an invocation of this method throws a checked exception,

     * then the channel will be closed.  </p>

     *

     * @param  remote

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

     *

     * @return  <tt>true</tt> if a connection was established,

     *          <tt>false</tt> if this channel is in non-blocking mode

     *          and the connection operation is in progress

     *

     * @throws  AlreadyConnectedException

     *          If this channel is already connected

     *

     * @throws  ConnectionPendingException

     *          If a non-blocking connection operation is already in progress

     *          on this channel

     *

     * @throws  ClosedChannelException

     *          If this channel is closed

     *

     * @throws  AsynchronousCloseException

     *          If another thread closes this channel

     *          while the connect operation is in progress

     *

     * @throws  ClosedByInterruptException

     *          If another thread interrupts the current thread

     *          while the connect operation is in progress, thereby

     *          closing the channel and setting the current thread's

     *          interrupt status

     *

     * @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  SecurityException

     *          If a security manager has been installed

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

     *

     * @throws  IOException

     *          If some other I/O error occurs

     */

    public abstract boolean connect(SocketAddress remote) throws IOException;

    /**

     * Finishes the process of connecting a socket channel.

     *

     * <p> A non-blocking connection operation is initiated by placing a socket

     * channel in non-blocking mode and then invoking its {@link #connect

     * connect} method.  Once the connection is established, or the attempt has

     * failed, the socket channel will become connectable and this method may

     * be invoked to complete the connection sequence.  If the connection

     * operation failed then invoking this method will cause an appropriate

     * {@link java.io.IOException} to be thrown.

     *

     * <p> If this channel is already connected then this method will not block

     * and will immediately return <tt>true</tt>.  If this channel is in

     * non-blocking mode then this method will return <tt>false</tt> if the

     * connection process is not yet complete.  If this channel is in blocking

     * mode then this method will block until the connection either completes

     * or fails, and will always either return <tt>true</tt> or throw a checked

     * exception describing the failure.

     *

     * <p> This method may be invoked at any time.  If a read or write

     * operation upon this channel is invoked while an invocation of this

     * method is in progress then that operation will first block until this

     * invocation is complete.  If a connection attempt fails, that is, if an

     * invocation of this method throws a checked exception, then the channel

     * will be closed.  </p>

     *

     * @return  <tt>true</tt> if, and only if, this channel's socket is now

     *          connected

     *

     * @throws  NoConnectionPendingException

     *          If this channel is not connected and a connection operation

     *          has not been initiated

     *

     * @throws  ClosedChannelException

     *          If this channel is closed

     *

     * @throws  AsynchronousCloseException

     *          If another thread closes this channel

     *          while the connect operation is in progress

     *

     * @throws  ClosedByInterruptException

     *          If another thread interrupts the current thread

     *          while the connect operation is in progress, thereby

     *          closing the channel and setting the current thread's

     *          interrupt status

     *

     * @throws  IOException

     *          If some other I/O error occurs

     */

    public abstract boolean finishConnect() throws IOException;

    // -- ByteChannel operations --

    /**

     * @throws  NotYetConnectedException

     *          If this channel is not yet connected

     */

    public abstract int read(ByteBuffer dst) throws IOException;

    /**

     * @throws  NotYetConnectedException

     *          If this channel is not yet connected

     */

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

        throws IOException;

    /**

     * @throws  NotYetConnectedException

     *          If this channel is not yet connected

     */

    public final long read(ByteBuffer[] dsts) throws IOException {

        return read(dsts, 0, dsts.length);

    }

    /**

     * @throws  NotYetConnectedException

     *          If this channel is not yet connected

     */

    public abstract int write(ByteBuffer src) throws IOException;

    /**

     * @throws  NotYetConnectedException

     *          If this channel is not yet connected

     */

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

        throws IOException;

    /**

     * @throws  NotYetConnectedException

     *          If this channel is not yet connected

     */

    public final long write(ByteBuffer[] srcs) throws IOException {

        return write(srcs, 0, srcs.length);

    }

}