--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/nio/channels/AsynchronousSocketChannel.java Sun Feb 15 12:25:54 2009 +0000
@@ -0,0 +1,670 @@
+/*
+ * 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,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * 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.nio.ByteBuffer;
+
+/**
+ * An asynchronous channel for stream-oriented connecting sockets.
+ *
+ * <p> Asynchronous socket channels are created in one of two ways. A newly-created
+ * {@code AsynchronousSocketChannel} is created by invoking one of the {@link
+ * #open open} methods defined by this class. A newly-created channel is open but
+ * not yet connected. A connected {@code AsynchronousSocketChannel} is created
+ * when a connection is made to the socket of an {@link AsynchronousServerSocketChannel}.
+ * It is not possible to create an asynchronous socket channel for an arbitrary,
+ * pre-existing {@link java.net.Socket socket}.
+ *
+ * <p> A newly-created channel is connected by invoking its {@link #connect connect}
+ * method; once connected, a channel remains connected until it is closed. Whether
+ * or not a socket channel is connected may be determined by invoking its {@link
+ * #getRemoteAddress getRemoteAddress} method. An attempt to invoke an I/O
+ * operation upon an unconnected channel will cause a {@link NotYetConnectedException}
+ * to be thrown.
+ *
+ * <p> Channels of this type are safe for use by multiple concurrent threads.
+ * They support concurrent reading and writing, though at most one read operation
+ * and one write operation can be outstanding at any time.
+ * If a thread initiates a read operation before a previous read operation has
+ * completed then a {@link ReadPendingException} will be thrown. Similarly, an
+ * attempt to initiate a write operation before a previous write has completed
+ * will throw a {@link WritePendingException}.
+ *
+ * <p> Socket options are configured using the {@link #setOption(SocketOption,Object)
+ * setOption} method. Asynchronous socket channels support 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_KEEPALIVE SO_KEEPALIVE} </td>
+ * <td> Keep connection alive </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#TCP_NODELAY TCP_NODELAY} </td>
+ * <td> Disable the Nagle algorithm </td>
+ * </tr>
+ * </table>
+ * </blockquote>
+ * Additional (implementation specific) options may also be supported.
+ *
+ * <h4>Timeouts</h4>
+ *
+ * <p> The {@link #read(ByteBuffer,long,TimeUnit,Object,CompletionHandler) read}
+ * and {@link #write(ByteBuffer,long,TimeUnit,Object,CompletionHandler) write}
+ * methods defined by this class allow a timeout to be specified when initiating
+ * a read or write operation. If the timeout elapses before an operation completes
+ * then the operation completes with the exception {@link
+ * InterruptedByTimeoutException}. A timeout may leave the channel, or the
+ * underlying connection, in an inconsistent state. Where the implementation
+ * cannot guarantee that bytes have not been read from the channel then it puts
+ * the channel into an implementation specific <em>error state</em>. A subsequent
+ * attempt to initiate a {@code read} operation causes an unspecified runtime
+ * exception to be thrown. Similarly if a {@code write} operation times out and
+ * the implementation cannot guarantee bytes have not been written to the
+ * channel then further attempts to {@code write} to the channel cause an
+ * unspecified runtime exception to be thrown. When a timeout elapses then the
+ * state of the {@link ByteBuffer}, or the sequence of buffers, for the I/O
+ * operation is not defined. Buffers should be discarded or at least care must
+ * be taken to ensure that the buffers are not accessed while the channel remains
+ * open.
+ *
+ * @since 1.7
+ */
+
+public abstract class AsynchronousSocketChannel
+ implements AsynchronousByteChannel, NetworkChannel
+{
+ private final AsynchronousChannelProvider provider;
+
+ /**
+ * Initializes a new instance of this class.
+ */
+ protected AsynchronousSocketChannel(AsynchronousChannelProvider provider) {
+ this.provider = provider;
+ }
+
+ /**
+ * Returns the provider that created this channel.
+ */
+ public final AsynchronousChannelProvider provider() {
+ return provider;
+ }
+
+ /**
+ * Opens an asynchronous socket channel.
+ *
+ * <p> The new channel is created by invoking the {@link
+ * AsynchronousChannelProvider#openAsynchronousSocketChannel
+ * openAsynchronousSocketChannel} method on the {@link
+ * AsynchronousChannelProvider} that created the group. If the group parameter
+ * is {@code null} then the resulting channel is created by the system-wide
+ * default provider, and bound to the <em>default group</em>.
+ *
+ * @param group
+ * The group to which the newly constructed channel should be bound,
+ * or {@code null} for the default group
+ *
+ * @return A new asynchronous socket channel
+ *
+ * @throws ShutdownChannelGroupException
+ * If the channel group is shutdown
+ * @throws IOException
+ * If an I/O error occurs
+ */
+ public static AsynchronousSocketChannel open(AsynchronousChannelGroup group)
+ throws IOException
+ {
+ AsynchronousChannelProvider provider = (group == null) ?
+ AsynchronousChannelProvider.provider() : group.provider();
+ return provider.openAsynchronousSocketChannel(group);
+ }
+
+ /**
+ * Opens an asynchronous socket channel.
+ *
+ * <p> This method returns an asynchronous socket channel that is bound to
+ * the <em>default group</em>.This method is equivalent to evaluating the
+ * expression:
+ * <blockquote><pre>
+ * open((AsynchronousChannelGroup)null);
+ * </pre></blockquote>
+ *
+ * @return A new asynchronous socket channel
+ *
+ * @throws IOException
+ * If an I/O error occurs
+ */
+ public static AsynchronousSocketChannel open()
+ throws IOException
+ {
+ return open(null);
+ }
+
+
+ // -- socket options and related --
+
+ /**
+ * @throws ConnectionPendingException
+ * If a connection operation is already in progress on this channel
+ * @throws AlreadyBoundException {@inheritDoc}
+ * @throws UnsupportedAddressTypeException {@inheritDoc}
+ * @throws ClosedChannelException {@inheritDoc}
+ * @throws IOException {@inheritDoc}
+ */
+ @Override
+ public abstract AsynchronousSocketChannel bind(SocketAddress local)
+ throws IOException;
+
+ /**
+ * @throws IllegalArgumentException {@inheritDoc}
+ * @throws ClosedChannelException {@inheritDoc}
+ * @throws IOException {@inheritDoc}
+ */
+ @Override
+ public abstract <T> AsynchronousSocketChannel setOption(SocketOption<T> name, T value)
+ throws IOException;
+
+ /**
+ * Shutdown the connection for reading without closing the channel.
+ *
+ * <p> Once shutdown for reading then further reads on the channel will
+ * return {@code -1}, the end-of-stream indication. If the input side of the
+ * connection is already shutdown then invoking this method has no effect.
+ * The effect on an outstanding read operation is system dependent and
+ * therefore not specified. The effect, if any, when there is data in the
+ * socket receive buffer that has not been read, or data arrives subsequently,
+ * is also system dependent.
+ *
+ * @return The channel
+ *
+ * @throws NotYetConnectedException
+ * If this channel is not yet connected
+ * @throws ClosedChannelException
+ * If this channel is closed
+ * @throws IOException
+ * If some other I/O error occurs
+ */
+ public abstract AsynchronousSocketChannel shutdownInput() throws IOException;
+
+ /**
+ * Shutdown the connection for writing without closing the channel.
+ *
+ * <p> Once shutdown for writing then further attempts to write to the
+ * channel will throw {@link ClosedChannelException}. If the output side of
+ * the connection is already shutdown then invoking this method has no
+ * effect. The effect on an outstanding write operation is system dependent
+ * and therefore not specified.
+ *
+ * @return The channel
+ *
+ * @throws NotYetConnectedException
+ * If this channel is not yet connected
+ * @throws ClosedChannelException
+ * If this channel is closed
+ * @throws IOException
+ * If some other I/O error occurs
+ */
+ public abstract AsynchronousSocketChannel shutdownOutput() throws IOException;
+
+ // -- state --
+
+ /**
+ * Returns the remote address to which this channel's socket is connected.
+ *
+ * <p> Where the channel is bound and 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;
+
+ // -- asynchronous operations --
+
+ /**
+ * Connects this channel.
+ *
+ * <p> This method initiates an operation to connect this channel, returning
+ * a {@code Future} representing the pending result of the operation. If
+ * the connection is successfully established then the {@code Future}'s
+ * {@link Future#get() get} method will return {@code null}. If the
+ * connection cannot be established then the channel is closed. In that case,
+ * invoking the {@code get} method throws {@link
+ * java.util.concurrent.ExecutionException} with an {@code IOException} as
+ * the cause.
+ *
+ * <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.
+ *
+ * @param remote
+ * The remote address to which this channel is to be connected
+ * @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 AlreadyConnectedException
+ * If this channel is already connected
+ * @throws ConnectionPendingException
+ * If a connection operation is already in progress on this channel
+ * @throws ShutdownChannelGroupException
+ * If a handler is specified, and the channel group is shutdown
+ * @throws SecurityException
+ * If a security manager has been installed
+ * and it does not permit access to the given remote endpoint
+ *
+ * @see #getRemoteAddress
+ */
+ public abstract <A> Future<Void> connect(SocketAddress remote,
+ A attachment,
+ CompletionHandler<Void,? super A> handler);
+
+ /**
+ * Connects this channel.
+ *
+ * <p> This method is equivalent to invoking {@link
+ * #connect(SocketAddress,Object,CompletionHandler)} with the {@code attachment}
+ * and handler parameters set to {@code null}.
+ *
+ * @param remote
+ * The remote address to which this channel is to be connected
+ *
+ * @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 AlreadyConnectedException
+ * If this channel is already connected
+ * @throws ConnectionPendingException
+ * If a connection operation is already in progress on this channel
+ * @throws SecurityException
+ * If a security manager has been installed
+ * and it does not permit access to the given remote endpoint
+ */
+ public final Future<Void> connect(SocketAddress remote) {
+ return connect(remote, null, null);
+ }
+
+ /**
+ * Reads a sequence of bytes from this channel into the given buffer.
+ *
+ * <p> This method initiates the reading of a sequence of bytes from this
+ * channel into the given buffer, returning a {@code Future} representing
+ * the pending result of the operation. The {@code Future}'s {@link
+ * Future#get() get} method returns the number of bytes read or {@code -1}
+ * if all bytes have been read and channel has reached end-of-stream.
+ *
+ * <p> If a timeout is specified and the timeout elapses before the operation
+ * completes then the operation completes with the exception {@link
+ * InterruptedByTimeoutException}. Where a timeout occurs, and the
+ * implementation cannot guarantee that bytes have not been read, or will not
+ * be read from the channel into the given buffer, then further attempts to
+ * read from the channel will cause an unspecific runtime exception to be
+ * thrown.
+ *
+ * <p> Otherwise this method works in the same manner as the {@link
+ * AsynchronousByteChannel#read(ByteBuffer,Object,CompletionHandler)}
+ * method.
+ *
+ * @param dst
+ * The buffer into which bytes are 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 {@code timeout} parameter is negative or the buffer is
+ * read-only
+ * @throws ReadPendingException
+ * If a read operation is already in progress on this channel
+ * @throws NotYetConnectedException
+ * If this channel is not yet connected
+ * @throws ShutdownChannelGroupException
+ * If a handler is specified, and the channel group is shutdown
+ */
+ public abstract <A> Future<Integer> read(ByteBuffer dst,
+ long timeout,
+ TimeUnit unit,
+ A attachment,
+ CompletionHandler<Integer,? super A> handler);
+
+ /**
+ * @throws IllegalArgumentException {@inheritDoc}
+ * @throws ReadPendingException {@inheritDoc}
+ * @throws NotYetConnectedException
+ * If this channel is not yet connected
+ * @throws ShutdownChannelGroupException
+ * If a handler is specified, and the channel group is shutdown
+ */
+ @Override
+ public final <A> Future<Integer> read(ByteBuffer dst,
+ A attachment,
+ CompletionHandler<Integer,? super A> handler)
+ {
+ return read(dst, 0L, TimeUnit.MILLISECONDS, attachment, handler);
+ }
+
+ /**
+ * @throws IllegalArgumentException {@inheritDoc}
+ * @throws ReadPendingException {@inheritDoc}
+ * @throws NotYetConnectedException
+ * If this channel is not yet connected
+ */
+ @Override
+ public final Future<Integer> read(ByteBuffer dst) {
+ return read(dst, 0L, TimeUnit.MILLISECONDS, null, null);
+ }
+
+ /**
+ * Reads a sequence of bytes from this channel into a subsequence of the
+ * given buffers. This operation, sometimes called a <em>scattering read</em>,
+ * is often useful when implementing network protocols that group data into
+ * segments consisting of one or more fixed-length headers followed by a
+ * variable-length body.
+ *
+ * <p> This method initiates a read of up to <i>r</i> bytes from this channel,
+ * where <i>r</i> is the total number of bytes remaining in the specified
+ * subsequence of the given buffer array, that is,
+ *
+ * <blockquote><pre>
+ * dsts[offset].remaining()
+ * + dsts[offset+1].remaining()
+ * + ... + dsts[offset+length-1].remaining()</pre></blockquote>
+ *
+ * at the moment that the read is attempted.
+ *
+ * <p> Suppose that a byte sequence of length <i>n</i> is read, where
+ * <tt>0</tt> <tt><</tt> <i>n</i> <tt><=</tt> <i>r</i>.
+ * Up to the first <tt>dsts[offset].remaining()</tt> bytes of this sequence
+ * are transferred into buffer <tt>dsts[offset]</tt>, up to the next
+ * <tt>dsts[offset+1].remaining()</tt> bytes are transferred into buffer
+ * <tt>dsts[offset+1]</tt>, and so forth, until the entire byte sequence
+ * is transferred into the given buffers. As many bytes as possible are
+ * transferred into each buffer, hence the final position of each updated
+ * buffer, except the last updated buffer, is guaranteed to be equal to
+ * that buffer's limit. The underlying operating system may impose a limit
+ * on the number of buffers that may be used in an I/O operation. Where the
+ * number of buffers (with bytes remaining), exceeds this limit, then the
+ * I/O operation is performed with the maximum number of buffers allowed by
+ * the operating system.
+ *
+ * <p> The return value from this method is a {@code Future} representing
+ * the pending result of the operation. The {@code Future}'s {@link
+ * Future#get() get} method returns the number of bytes read or {@code -1L}
+ * if all bytes have been read and the channel has reached end-of-stream.
+ *
+ * <p> If a timeout is specified and the timeout elapses before the operation
+ * completes then it completes with the exception {@link
+ * InterruptedByTimeoutException}. Where a timeout occurs, and the
+ * implementation cannot guarantee that bytes have not been read, or will not
+ * be read from the channel into the given buffers, then further attempts to
+ * read from the channel will cause an unspecific runtime exception to be
+ * thrown.
+ *
+ * @param dsts
+ * The buffers into which bytes are to be transferred
+ * @param offset
+ * The offset within the buffer array of the first buffer into which
+ * bytes are to be transferred; must be non-negative and no larger than
+ * {@code dsts.length}
+ * @param length
+ * The maximum number of buffers to be accessed; must be non-negative
+ * and no larger than {@code dsts.length - offset}
+ * @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 IndexOutOfBoundsException
+ * If the pre-conditions for the {@code offset} and {@code length}
+ * parameter aren't met
+ * @throws IllegalArgumentException
+ * If the {@code timeout} parameter is negative, or a buffer is
+ * read-only
+ * @throws ReadPendingException
+ * If a read operation is already in progress on this channel
+ * @throws NotYetConnectedException
+ * If this channel is not yet connected
+ * @throws ShutdownChannelGroupException
+ * If a handler is specified, and the channel group is shutdown
+ */
+ public abstract <A> Future<Long> read(ByteBuffer[] dsts,
+ int offset,
+ int length,
+ long timeout,
+ TimeUnit unit,
+ A attachment,
+ CompletionHandler<Long,? super A> handler);
+
+ /**
+ * Writes a sequence of bytes to this channel from the given buffer.
+ *
+ * <p> This method initiates the writing of a sequence of bytes to this channel
+ * from the given buffer, returning a {@code Future} representing the
+ * pending result of the operation. The {@code Future}'s {@link Future#get()
+ * get} method will return the number of bytes written.
+ *
+ * <p> If a timeout is specified and the timeout elapses before the operation
+ * completes then it completes with the exception {@link
+ * InterruptedByTimeoutException}. Where a timeout occurs, and the
+ * implementation cannot guarantee that bytes have not been written, or will
+ * not be written to the channel from the given buffer, then further attempts
+ * to write to the channel will cause an unspecific runtime exception to be
+ * thrown.
+ *
+ * <p> Otherwise this method works in the same manner as the {@link
+ * AsynchronousByteChannel#write(ByteBuffer,Object,CompletionHandler)}
+ * method.
+ *
+ * @param src
+ * The buffer from which bytes are to be retrieved
+ * @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 {@code timeout} parameter is negative
+ * @throws WritePendingException
+ * If a write operation is already in progress on this channel
+ * @throws NotYetConnectedException
+ * If this channel is not yet connected
+ * @throws ShutdownChannelGroupException
+ * If a handler is specified, and the channel group is shutdown
+ */
+ public abstract <A> Future<Integer> write(ByteBuffer src,
+ long timeout,
+ TimeUnit unit,
+ A attachment,
+ CompletionHandler<Integer,? super A> handler);
+
+ /**
+ * @throws WritePendingException {@inheritDoc}
+ * @throws NotYetConnectedException
+ * If this channel is not yet connected
+ * @throws ShutdownChannelGroupException
+ * If a handler is specified, and the channel group is shutdown
+ */
+ @Override
+ public final <A> Future<Integer> write(ByteBuffer src,
+ A attachment,
+ CompletionHandler<Integer,? super A> handler)
+
+ {
+ return write(src, 0L, TimeUnit.MILLISECONDS, attachment, handler);
+ }
+
+ /**
+ * @throws WritePendingException {@inheritDoc}
+ * @throws NotYetConnectedException
+ * If this channel is not yet connected
+ */
+ @Override
+ public final Future<Integer> write(ByteBuffer src) {
+ return write(src, 0L, TimeUnit.MILLISECONDS, null, null);
+ }
+
+ /**
+ * Writes a sequence of bytes to this channel from a subsequence of the given
+ * buffers. This operation, sometimes called a <em>gathering write</em>, is
+ * often useful when implementing network protocols that group data into
+ * segments consisting of one or more fixed-length headers followed by a
+ * variable-length body.
+ *
+ * <p> This method initiates a write of up to <i>r</i> bytes to this channel,
+ * where <i>r</i> is the total number of bytes remaining in the specified
+ * subsequence of the given buffer array, that is,
+ *
+ * <blockquote><pre>
+ * srcs[offset].remaining()
+ * + srcs[offset+1].remaining()
+ * + ... + srcs[offset+length-1].remaining()</pre></blockquote>
+ *
+ * at the moment that the write is attempted.
+ *
+ * <p> Suppose that a byte sequence of length <i>n</i> is written, where
+ * <tt>0</tt> <tt><</tt> <i>n</i> <tt><=</tt> <i>r</i>.
+ * Up to the first <tt>srcs[offset].remaining()</tt> bytes of this sequence
+ * are written from buffer <tt>srcs[offset]</tt>, up to the next
+ * <tt>srcs[offset+1].remaining()</tt> bytes are written from buffer
+ * <tt>srcs[offset+1]</tt>, and so forth, until the entire byte sequence is
+ * written. As many bytes as possible are written from each buffer, hence
+ * the final position of each updated buffer, except the last updated
+ * buffer, is guaranteed to be equal to that buffer's limit. The underlying
+ * operating system may impose a limit on the number of buffers that may be
+ * used in an I/O operation. Where the number of buffers (with bytes
+ * remaining), exceeds this limit, then the I/O operation is performed with
+ * the maximum number of buffers allowed by the operating system.
+ *
+ * <p> The return value from this method is a {@code Future} representing
+ * the pending result of the operation. The {@code Future}'s {@link
+ * Future#get() get} method will return the number of bytes written.
+ *
+ * <p> If a timeout is specified and the timeout elapses before the operation
+ * completes then it completes with the exception {@link
+ * InterruptedByTimeoutException}. Where a timeout occurs, and the
+ * implementation cannot guarantee that bytes have not been written, or will
+ * not be written to the channel from the given buffers, then further attempts
+ * to write to the channel will cause an unspecific runtime exception to be
+ * thrown.
+ *
+ * @param srcs
+ * The buffers from which bytes are to be retrieved
+ * @param offset
+ * The offset within the buffer array of the first buffer from which
+ * bytes are to be retrieved; must be non-negative and no larger
+ * than {@code srcs.length}
+ * @param length
+ * The maximum number of buffers to be accessed; must be non-negative
+ * and no larger than {@code srcs.length - offset}
+ * @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 IndexOutOfBoundsException
+ * If the pre-conditions for the {@code offset} and {@code length}
+ * parameter aren't met
+ * @throws IllegalArgumentException
+ * If the {@code timeout} parameter is negative
+ * @throws WritePendingException
+ * If a write operation is already in progress on this channel
+ * @throws NotYetConnectedException
+ * If this channel is not yet connected
+ * @throws ShutdownChannelGroupException
+ * If a handler is specified, and the channel group is shutdown
+ */
+ public abstract <A> Future<Long> write(ByteBuffer[] srcs,
+ int offset,
+ int length,
+ long timeout,
+ TimeUnit unit,
+ A attachment,
+ CompletionHandler<Long,? super A> handler);
+}