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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.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;
  }
  