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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.io.IOException;
  import java.nio.channels.spi.*;
  
  
  /**
   * A pair of channels that implements a unidirectional pipe.
   *
   * <p> A pipe consists of a pair of channels: A writable {@link
   * SinkChannel sink} channel and a readable {@link SourceChannel source}
   * channel.  Once some bytes are written to the sink channel they can be read
   * from source channel in exactlyAthe order in which they were written.
   *
   * <p> Whether or not a thread writing bytes to a pipe will block until another
   * thread reads those bytes, or some previously-written bytes, from the pipe is
   * system-dependent and therefore unspecified.  Many pipe implementations will
   * buffer up to a certain number of bytes between the sink and source channels,
   * but such buffering should not be assumed.  </p>
   *
   *
   * @author Mark Reinhold
   * @author JSR-51 Expert Group
   * @since 1.4
   */
  
  public abstract class Pipe {
  
      /**
       * A channel representing the readable end of a {@link Pipe}.
       *
       * @since 1.4
       */
      public static abstract class SourceChannel
          extends AbstractSelectableChannel
          implements ReadableByteChannel, ScatteringByteChannel
      {
          /**
           * Constructs a new instance of this class.
           *
           * @param  provider
           *         The selector provider
           */
          protected SourceChannel(SelectorProvider provider) {
              super(provider);
          }
  
          /**
           * Returns an operation set identifying this channel's supported
           * operations.
           *
           * <p> Pipe-source channels only support reading, so this method
           * returns {@link SelectionKey#OP_READ}.  </p>
           *
           * @return  The valid-operation set
           */
          public final int validOps() {
              return SelectionKey.OP_READ;
          }
  
      }
  
      /**
       * A channel representing the writable end of a {@link Pipe}.
       *
       * @since 1.4
       */
      public static abstract class SinkChannel
          extends AbstractSelectableChannel
          implements WritableByteChannel, GatheringByteChannel
      {
          /**
           * Initializes a new instance of this class.
           *
           * @param  provider
           *         The selector provider
           */
          protected SinkChannel(SelectorProvider provider) {
              super(provider);
          }
  
          /**
           * Returns an operation set identifying this channel's supported
           * operations.
           *
           * <p> Pipe-sink channels only support writing, so this method returns
           * {@link SelectionKey#OP_WRITE}.  </p>
           *
           * @return  The valid-operation set
           */
          public final int validOps() {
              return SelectionKey.OP_WRITE;
          }
  
      }
  
      /**
       * Initializes a new instance of this class.
       */
      protected Pipe() { }
  
      /**
       * Returns this pipe's source channel.
       *
       * @return  This pipe's source channel
       */
      public abstract SourceChannel source();
  
      /**
       * Returns this pipe's sink channel.
       *
       * @return  This pipe's sink channel
       */
      public abstract SinkChannel sink();
  
      /**
       * Opens a pipe.
       *
       * <p> The new pipe is created by invoking the {@link
       * SelectorProvider#openPipe openPipe} method of the
       * system-wide default {@link SelectorProvider}
       * object.  </p>
       *
       * @return  A new pipe
       *
       * @throws  IOException
       *          If an I/O error occurs
       */
      public static Pipe open() throws IOException {
          return SelectorProvider.provider().openPipe();
      }
  
  }
  