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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

 * Pipe.SinkChannel sink} channel and a readable {@link Pipe.SourceChannel source}

 * channel.  Once some bytes are written to the sink channel they can be read

 * from the source channel in exactly the 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 abstract static 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 abstract static 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

     * java.nio.channels.spi.SelectorProvider#openPipe openPipe} method of the

     * system-wide default {@link java.nio.channels.spi.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();

    }

}