/*
* $Header$
* $Revision: 982 $
* $Date: 2006-12-08 18:42:51 +1000 (Fri, 08 Dec 2006) $
*
* ====================================================================
*
* The Apache Software License, Version 1.1
*
* Copyright (c) 2003-2009 The JRDF Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. 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.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* the JRDF Project (http://jrdf.sf.net/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The JRDF Project" and "JRDF" must not be used to endorse
* or promote products derived from this software without prior written
* permission. For written permission, please contact
* newmana@users.sourceforge.net.
*
* 5. Products derived from this software may not be called "JRDF"
* nor may "JRDF" appear in their names without prior written
* permission of the JRDF Project.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 APACHE SOFTWARE FOUNDATION OR
* ITS 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.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the JRDF Project. For more
* information on JRDF, please see <http://jrdf.sourceforge.net/>.
*
*/
package org.jrdf.graph.local.iterator;
import org.jrdf.graph.Literal;
import org.jrdf.graph.Node;
import org.jrdf.graph.Resource;
import org.jrdf.graph.local.ResourceFactory;
import org.jrdf.graph.local.index.longindex.LongIndex;
import org.jrdf.graph.local.index.nodepool.NodePool;
import org.jrdf.util.ClosableIterator;
import static org.jrdf.util.param.ParameterUtil.checkNotNull;
import java.util.NoSuchElementException;
public abstract class ResourceIterator<E> implements ClosableIterator<E> {
protected final LongIndex longIndex012;
protected final ResourceFactory resourceFactory;
protected ClosableIterator<Long[]> iterator012; //spo iterator
protected ClosableIterator<Long[]> iterator201; //osp iterator
protected Resource nextResource;
protected boolean firstTime = true;
protected NodePool nodePool;
private boolean hasClosed;
public ResourceIterator(final LongIndex[] newLongIndexes, final ResourceFactory newResourceFactory,
final NodePool newNodePool) {
checkNotNull(newLongIndexes, newResourceFactory, newNodePool);
resourceFactory = newResourceFactory;
longIndex012 = newLongIndexes[0];
iterator201 = newLongIndexes[2].iterator();
iterator012 = newLongIndexes[0].iterator();
nodePool = newNodePool;
nextResource = getNextNode();
}
public boolean close() {
if (!hasClosed) {
iterator201.close();
iterator012.close();
}
hasClosed = true;
return true;
}
public boolean hasNext() {
boolean hasNext = nextResource != null;
if (!hasNext) {
close();
}
return hasNext;
}
private Resource getNextNode() {
Resource resource = null;
if (iterator201.hasNext()) {
resource = getNextOSPElement();
if (resource == null) {
return getNextNode();
}
}
if (iterator012.hasNext()) {
resource = getNextSPOElement();
}
if (resource == null) {
close();
}
return resource;
}
/**
* Get the next object element from the OSP index.
*
* @return next object in the osp index.
*/
private Resource getNextOSPElement() {
while (iterator201.hasNext()) {
//Long index = iterator201.next().getKey();
final Long nodeId = getNextNodeId(iterator201);
//check the SPO does not contain the given index and that we haven't reached the end of iterator
if (nodeId != -1 && !longIndex012.contains(nodeId)) {
final Node node = nodePool.getNodeById(nodeId);
//check node is not a literal
if (!(node instanceof Literal)) {
return resourceFactory.createResource(node);
}
}
}
return null;
}
/**
* Get the next subject element in the SPO index.
*
* @return next element in the SPO index.
*/
private Resource getNextSPOElement() {
final Long index = getNextNodeId(iterator012);
if (index != -1) {
final Node node = nodePool.getNodeById(index);
return resourceFactory.createResource(node);
}
return null;
}
public void remove() {
throw new UnsupportedOperationException();
}
protected Resource getNextResource() {
//for the first time retrieve the current one as well as the next one
final Resource resource;
if (nextResource == null) {
throw new NoSuchElementException();
} else {
resource = nextResource;
nextResource = getNextNode();
}
return resource;
}
/**
* Provides a customizable way in which to filter out resource nodes based on type.
*
* @param iterator iterators over the index.
* @return the next node identifier.
*/
protected abstract long getNextNodeId(ClosableIterator<Long[]> iterator);
}