/*
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program 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 for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Aug 7, 2008
*/
package com.bigdata.striterator;
import java.util.Arrays;
import java.util.Iterator;
import java.util.NoSuchElementException;
import cutthecrap.utils.striterators.ICloseableIterator;
/**
* Element-at-a-time filter with generics.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
* @param <I>
* The generic type of the iterator.
* @param <E>
* The generic type of the elements visited by the iterator.
*/
abstract public class Filter<I extends Iterator<E>,E> implements IFilter<I,E,E> {
/**
*
*/
private static final long serialVersionUID = 1L;
private final int chunkSize;
protected Object state;
public Filter() {
this( null );
}
public Filter(Object state) {
this(IChunkedIterator.DEFAULT_CHUNK_SIZE, state);
}
public Filter(int chunkSize, Object state) {
this.chunkSize = chunkSize;
this.state = state;
}
// @SuppressWarnings("unchecked")
public IChunkedIterator<E> filter(I src) {
return new FilteredIterator<I, E>(chunkSize, src, this);
}
/**
* Return <code>true</code> iff the element should be visited.
*
* @param e
* The element.
*/
abstract protected boolean isValid(E e);
/**
* Applies filter to the source iterator.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
* @param <I>
* @param <E>
*/
private static class FilteredIterator<I extends Iterator<E>, E> implements
IChunkedIterator<E> {
/** The source iterator. */
private final I src;
/** The filter. */
private final Filter<I, E> filter;
/** One step lookahead. */
private E next;
/** The chunk size. */
private final int chunkSize;
/** <code>null</code> unless the source iterator is ordered. */
private final IKeyOrder<E> keyOrder;
/**
* @param chunkSize The chunk size.
* @param src
* The source iterator.
* @param filter
* The filter.
*/
public FilteredIterator(int chunkSize, I src, Filter<I, E> filter) {
this.chunkSize = chunkSize;
this.src = src;
this.filter = filter;
if(src instanceof IChunkedOrderedIterator<?>) {
keyOrder = ((IChunkedOrderedIterator<E>) src).getKeyOrder();
} else {
keyOrder = null;
}
}
public boolean hasNext() {
if (next != null)
return true;
while(src.hasNext()) {
final E e = src.next();
if(filter.isValid(e)) {
next = e;
return true;
}
}
return false;
}
public E next() {
if (!hasNext())
throw new NoSuchElementException();
final E tmp = next;
next = null;
return tmp;
}
/**
* Not supported since the one-step lookahead means that we would have
* to delete the previous element from the source.
*/
public void remove() {
throw new UnsupportedOperationException();
}
/**
* The next chunk of elements in whatever order the were visited by
* {@link #next()}.
*/
@SuppressWarnings("unchecked")
public E[] nextChunk() {
if (!hasNext()) {
throw new NoSuchElementException();
}
int n = 0;
E[] chunk = null;
while (hasNext() && n < chunkSize) {
E t = next();
if (chunk == null) {
/*
* Dynamically instantiation an array of the same component type
* as the objects that we are visiting.
*/
chunk = (E[]) java.lang.reflect.Array.newInstance(t.getClass(),
chunkSize);
}
// add to this chunk.
chunk[n++] = t;
}
if (n != chunkSize) {
// make it dense.
E[] tmp = (E[])java.lang.reflect.Array.newInstance(
// chunk[0].getClass(),
chunk.getClass().getComponentType(),//
n);
System.arraycopy(chunk, 0, tmp, 0, n);
chunk = tmp;
}
return chunk;
}
/**
* The {@link IKeyOrder} iff the source iterator implements
* {@link IChunkedOrderedIterator}.
*/
public IKeyOrder<E> getKeyOrder() {
return keyOrder;
}
public E[] nextChunk(IKeyOrder<E> keyOrder) {
if (keyOrder == null)
throw new IllegalArgumentException();
final E[] chunk = nextChunk();
if (!keyOrder.equals(getKeyOrder())) {
// sort into the required order.
Arrays.sort(chunk, 0, chunk.length, keyOrder.getComparator());
}
return chunk;
}
public void close() {
if(src instanceof ICloseableIterator<?>) {
((ICloseableIterator<E>)src).close();
}
}
}
}