/*
* Copyright (c) 2002-2009, The DSpace Foundation. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of the DSpace Foundation nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
* TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
* USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*/
package org.dspace.checker;
/**
* <p>
* BitstreamDispatchers are strategy objects that hand bitstream ids out to
* workers. Implementations must be threadsafe.
* </p>
*
* <p>
* The rationale behind the use of the Sentinel pattern (rather than the more
* traditional iterator pattern or a cursor c.f. java.sql.ResultSet): -
* </p>
* <ol>
* <li>To make it easy to make implementations thread safe - multithreaded
* invocation of the dispatchers is seen as a next step use case. In simple
* terms, this requires that a single method does all the work.</li>
* <li>Shouldn't an exception as the sentinel, as reaching the end of a loop is
* not an exceptional condition.</li>
* </ol>
*
*
* @author Jim Downing
* @author Grace Carpenter
* @author Nathan Sarr
*
*/
public interface BitstreamDispatcher
{
/**
* This value should be returned by <code>next()</code> to indicate that
* there are no more values.
*/
public static int SENTINEL = -1;
/**
* Returns the next id for checking, or a sentinel value if there are no
* more to check.
*
* @return the next bitstream id, or BitstreamDispatcher.SENTINEL if there
* isn't another value
*
*/
public int next();
}