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* 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
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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} {@code <} <i>n</i> {@code <=} <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> {@code +} <i>n</i> {@code -} {@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> {@code +} <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} {@code <} <i>n</i> {@code <=} <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> {@code +} <i>n</i> {@code -} {@code 1}.
* Upon completion the buffer's position will be equal to
* <i>p</i> {@code +} <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);
}