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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package java.nio.channels;

import java.nio.ByteBuffer;

import java.util.concurrent.Future;

/**

 * An asynchronous channel that can read and write bytes.

 *

 * <p> Some channels may not allow more than one read or write to be outstanding

 * at any given time. If a thread invokes a read method before a previous read

 * operation has completed then a {@link ReadPendingException} will be thrown.

 * Similarly, if a write method is invoked before a previous write has completed

 * then {@link WritePendingException} is thrown. Whether or not other kinds of

 * I/O operations may proceed concurrently with a read operation depends upon

 * the type of the channel.

 *

 * <p> Note that {@link java.nio.ByteBuffer ByteBuffers} are not safe for use by

 * multiple concurrent threads. When a read or write operation is initiated then

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

 * operation completes.

 *

 * @see Channels#newInputStream(AsynchronousByteChannel)

 * @see Channels#newOutputStream(AsynchronousByteChannel)

 *

 * @since 1.7

 */

public interface AsynchronousByteChannel

    extends AsynchronousChannel

{

    /**

     * Reads a sequence of bytes from this channel into the given buffer.

     *

     * <p> This method initiates an asynchronous read operation to read a

     * sequence of bytes from this channel into the given buffer. The {@code

     * handler} parameter is a completion handler that is invoked when the read

     * operation completes (or fails). The result passed to the completion

     * handler is the number of bytes read or {@code -1} if no bytes could be

     * read because the channel has reached end-of-stream.

     *

     * <p> The read operation may read up to <i>r</i> bytes from the channel,

     * where <i>r</i> is the number of bytes remaining in the buffer, that is,

     * {@code dst.remaining()} at the time that the read is attempted. Where

     * <i>r</i> is 0, the read operation completes immediately with a result of

     * {@code 0} without initiating an I/O operation.

     *

     * <p> Suppose that a byte sequence of length <i>n</i> is read, where

     * {@code 0}&nbsp;{@code <}&nbsp;<i>n</i>&nbsp;{@code <=}&nbsp;<i>r</i>.

     * This byte sequence will be transferred into the buffer so that the first

     * byte in the sequence is at index <i>p</i> and the last byte is at index

     * <i>p</i>&nbsp;{@code +}&nbsp;<i>n</i>&nbsp;{@code -}&nbsp;{@code 1},

     * where <i>p</i> is the buffer's position at the moment the read is

     * performed. Upon completion the buffer's position will be equal to

     * <i>p</i>&nbsp;{@code +}&nbsp;<i>n</i>; its limit will not have changed.

     *

     * <p> Buffers are not safe for use by multiple concurrent threads so care

     * should be taken to not access the buffer until the operation has

     * completed.

     *

     * <p> This method may be invoked at any time. Some channel types may not

     * allow more than one read to be outstanding at any given time. If a thread

     * initiates a read operation before a previous read operation has

     * completed then a {@link ReadPendingException} will be thrown.

     *

     * @param   <A>

     *          The type of the attachment

     * @param   dst

     *          The buffer into which bytes are to be transferred

     * @param   attachment

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

     * @param   handler

     *          The completion handler

     *

     * @throws  IllegalArgumentException

     *          If the buffer is read-only

     * @throws  ReadPendingException

     *          If the channel does not allow more than one read to be outstanding

     *          and a previous read has not completed

     * @throws  ShutdownChannelGroupException

     *          If the channel is associated with a {@link AsynchronousChannelGroup

     *          group} that has terminated

     */

    <A> void read(ByteBuffer dst,

                  A attachment,

                  CompletionHandler<Integer,? super A> handler);

    /**

     * Reads a sequence of bytes from this channel into the given buffer.

     *

     * <p> This method initiates an asynchronous read operation to read a

     * sequence of bytes from this channel into the given buffer. The method

     * behaves in exactly the same manner as the {@link

     * #read(ByteBuffer,Object,CompletionHandler)

     * read(ByteBuffer,Object,CompletionHandler)} method except that instead

     * of specifying a completion handler, this method returns a {@code Future}

     * representing the pending result. The {@code Future}'s {@link Future#get()

     * get} method returns the number of bytes read or {@code -1} if no bytes

     * could be read because the channel has reached end-of-stream.

     *

     * @param   dst

     *          The buffer into which bytes are to be transferred

     *

     * @return  A Future representing the result of the operation

     *

     * @throws  IllegalArgumentException

     *          If the buffer is read-only

     * @throws  ReadPendingException

     *          If the channel does not allow more than one read to be outstanding

     *          and a previous read has not completed

     */

    Future<Integer> read(ByteBuffer dst);

    /**

     * Writes a sequence of bytes to this channel from the given buffer.

     *

     * <p> This method initiates an asynchronous write operation to write a

     * sequence of bytes to this channel from the given buffer. The {@code

     * handler} parameter is a completion handler that is invoked when the write

     * operation completes (or fails). The result passed to the completion

     * handler is the number of bytes written.

     *

     * <p> The write operation may write up to <i>r</i> bytes to the channel,

     * where <i>r</i> is the number of bytes remaining in the buffer, that is,

     * {@code src.remaining()} at the time that the write is attempted. Where

     * <i>r</i> is 0, the write operation completes immediately with a result of

     * {@code 0} without initiating an I/O operation.

     *

     * <p> Suppose that a byte sequence of length <i>n</i> is written, where

     * {@code 0}&nbsp;{@code <}&nbsp;<i>n</i>&nbsp;{@code <=}&nbsp;<i>r</i>.

     * This byte sequence will be transferred from the buffer starting at index

     * <i>p</i>, where <i>p</i> is the buffer's position at the moment the

     * write is performed; the index of the last byte written will be

     * <i>p</i>&nbsp;{@code +}&nbsp;<i>n</i>&nbsp;{@code -}&nbsp;{@code 1}.

     * Upon completion the buffer's position will be equal to

     * <i>p</i>&nbsp;{@code +}&nbsp;<i>n</i>; its limit will not have changed.

     *

     * <p> Buffers are not safe for use by multiple concurrent threads so care

     * should be taken to not access the buffer until the operation has

     * completed.

     *

     * <p> This method may be invoked at any time. Some channel types may not

     * allow more than one write to be outstanding at any given time. If a thread

     * initiates a write operation before a previous write operation has

     * completed then a {@link WritePendingException} will be thrown.

     *

     * @param   <A>

     *          The type of the attachment

     * @param   src

     *          The buffer from which bytes are to be retrieved

     * @param   attachment

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

     * @param   handler

     *          The completion handler object

     *

     * @throws  WritePendingException

     *          If the channel does not allow more than one write to be outstanding

     *          and a previous write has not completed

     * @throws  ShutdownChannelGroupException

     *          If the channel is associated with a {@link AsynchronousChannelGroup

     *          group} that has terminated

     */

    <A> void write(ByteBuffer src,

                   A attachment,

                   CompletionHandler<Integer,? super A> handler);

    /**

     * Writes a sequence of bytes to this channel from the given buffer.

     *

     * <p> This method initiates an asynchronous write operation to write a

     * sequence of bytes to this channel from the given buffer. The method

     * behaves in exactly the same manner as the {@link

     * #write(ByteBuffer,Object,CompletionHandler)

     * write(ByteBuffer,Object,CompletionHandler)} method except that instead

     * of specifying a completion handler, this method returns a {@code Future}

     * representing the pending result. The {@code Future}'s {@link Future#get()

     * get} method returns the number of bytes written.

     *

     * @param   src

     *          The buffer from which bytes are to be retrieved

     *

     * @return A Future representing the result of the operation

     *

     * @throws  WritePendingException

     *          If the channel does not allow more than one write to be outstanding

     *          and a previous write has not completed

     */

    Future<Integer> write(ByteBuffer src);

}