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	/*
	* Copyright (c) 2007, 2011, Oracle and/or its affiliates. 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. 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
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.nio.channels;

	import java.nio.ByteBuffer;
	import java.io.IOException;

	/**
	* A byte channel that maintains a current <i>position</i> and allows the
	* position to be changed.
	*
	* <p> A seekable byte channel is connected to an entity, typically a file,
	* that contains a variable-length sequence of bytes that can be read and
	* written. The current position can be {@link #position() <i>queried</i>} and
	* {@link #position(long) <i>modified</i>}. The channel also provides access to
	* the current <i>size</i> of the entity to which the channel is connected. The
	* size increases when bytes are written beyond its current size; the size
	* decreases when it is {@link #truncate <i>truncated</i>}.
	*
	* <p> The {@link #position(long) position} and {@link #truncate truncate} methods
	* which do not otherwise have a value to return are specified to return the
	* channel upon which they are invoked. This allows method invocations to be
	* chained. Implementations of this interface should specialize the return type
	* so that method invocations on the implementation class can be chained.
	*
	* @since 1.7
	* @see java.nio.file.Files#newByteChannel
	*/

	public interface SeekableByteChannel
	extends ByteChannel
	{
	/**
	* Reads a sequence of bytes from this channel into the given buffer.
	*
	* <p> Bytes are read starting at this channel's current position, and
	* then the position is updated with the number of bytes actually read.
	* Otherwise this method behaves exactly as specified in the {@link
	* ReadableByteChannel} interface.
	*/
	@Override
	int read(ByteBuffer dst) throws IOException;

	/**
	* Writes a sequence of bytes to this channel from the given buffer.
	*
	* <p> Bytes are written starting at this channel's current position, unless
	* the channel is connected to an entity such as a file that is opened with
	* the {@link java.nio.file.StandardOpenOption#APPEND APPEND} option, in
	* which case the position is first advanced to the end. The entity to which
	* the channel is connected is grown, if necessary, to accommodate the
	* written bytes, and then the position is updated with the number of bytes
	* actually written. Otherwise this method behaves exactly as specified by
	* the {@link WritableByteChannel} interface.
	*/
	@Override
	int write(ByteBuffer src) throws IOException;

	/**
	* Returns this channel's position.
	*
	* @return This channel's position,
	* a non-negative integer counting the number of bytes
	* from the beginning of the entity to the current position
	*
	* @throws ClosedChannelException
	* If this channel is closed
	* @throws IOException
	* If some other I/O error occurs
	*/
	long position() throws IOException;

	/**
	* Sets this channel's position.
	*
	* <p> Setting the position to a value that is greater than the current size
	* is legal but does not change the size of the entity. A later attempt to
	* read bytes at such a position will immediately return an end-of-file
	* indication. A later attempt to write bytes at such a position will cause
	* the entity to grow to accommodate the new bytes; the values of any bytes
	* between the previous end-of-file and the newly-written bytes are
	* unspecified.
	*
	* <p> Setting the channel's position is not recommended when connected to
	* an entity, typically a file, that is opened with the {@link
	* java.nio.file.StandardOpenOption#APPEND APPEND} option. When opened for
	* append, the position is first advanced to the end before writing.
	*
	* @param newPosition
	* The new position, a non-negative integer counting
	* the number of bytes from the beginning of the entity
	*
	* @return This channel
	*
	* @throws ClosedChannelException
	* If this channel is closed
	* @throws IllegalArgumentException
	* If the new position is negative
	* @throws IOException
	* If some other I/O error occurs
	*/
	SeekableByteChannel position(long newPosition) throws IOException;

	/**
	* Returns the current size of entity to which this channel is connected.
	*
	* @return The current size, measured in bytes
	*
	* @throws ClosedChannelException
	* If this channel is closed
	* @throws IOException
	* If some other I/O error occurs
	*/
	long size() throws IOException;

	/**
	* Truncates the entity, to which this channel is connected, to the given
	* size.
	*
	* <p> If the given size is less than the current size then the entity is
	* truncated, discarding any bytes beyond the new end. If the given size is
	* greater than or equal to the current size then the entity is not modified.
	* In either case, if the current position is greater than the given size
	* then it is set to that size.
	*
	* <p> An implementation of this interface may prohibit truncation when
	* connected to an entity, typically a file, opened with the {@link
	* java.nio.file.StandardOpenOption#APPEND APPEND} option.
	*
	* @param size
	* The new size, a non-negative byte count
	*
	* @return This channel
	*
	* @throws NonWritableChannelException
	* If this channel was not opened for writing
	* @throws ClosedChannelException
	* If this channel is closed
	* @throws IllegalArgumentException
	* If the new size is negative
	* @throws IOException
	* If some other I/O error occurs
	*/
	SeekableByteChannel truncate(long size) throws IOException;
	}

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