com.bigdata.striterator.ChunkedResolvingIterator Maven / Gradle / Ivy
/*
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
[email protected]
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 Jun 26, 2008
*/
package com.bigdata.striterator;
import java.util.Arrays;
import cutthecrap.utils.striterators.ICloseableIterator;
/**
* Converts the type of the source iterator using {@link #resolve(Object)}.
*
* Note: This class correctly passes {@link ICloseableIterator#close()} through
* to the source iterator.
*
* @author Bryan Thompson
* @version $Id$
*
* @param
* The generic type of the elements visited by the [S]ource iterator.
* @param
* The generic type of the [E]lements visited by this iterator.
*/
abstract public class ChunkedResolvingIterator implements IChunkedOrderedIterator {
private final IChunkedOrderedIterator src;
private final IKeyOrder keyOrder;
/**
* Ctor variant when resolving changes the sort order such that the resolved
* elements would need to be sorted to put them into a known order.
*
* @param src
* The source iterator.
*/
public ChunkedResolvingIterator(final IChunkedOrderedIterator src) {
this(src, null/* keyOrder */);
}
/**
* Ctor variant when (a) you KNOW the sort order for the source iterator and
* (b) the source elements and the resolved elements have the same natural
* sort order (so the sort order is naturally preserved when the elements
* are resolved).
*
* @param src
* The source iterator.
* @param keyOrder
* The sort order for the resolved elements.
*/
public ChunkedResolvingIterator(final IChunkedOrderedIterator src,
final IKeyOrder keyOrder) {
if (src == null)
throw new IllegalArgumentException();
this.src = src;
this.keyOrder = keyOrder;
}
@Override
public IKeyOrder getKeyOrder() {
return keyOrder;
}
@Override
public boolean hasNext() {
return src.hasNext();
}
@Override
public E next() {
return resolve( src.next() );
}
@Override
@SuppressWarnings("unchecked")
public E[] nextChunk() {
final S[] a = src.nextChunk();
E[] b = null;
for (int i = 0; i < a.length; i++) {
final E e = resolve(a[i]);
if (b == null) {
/*
* Dynamically instantiation an array of the same component type
* as the objects that we are visiting.
*/
b = (E[]) java.lang.reflect.Array.newInstance(e.getClass(),
a.length);
}
b[i] = e;
}
return b;
}
@Override
public E[] nextChunk(final IKeyOrder 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;
}
@Override
public void remove() {
src.remove();
}
@Override
public void close() {
src.close();
}
/**
* Resolve an element visited by the source iterator into an element of the
* type visitable by this iterator.
*
* @param e
* An element visited by the source iterator.
*
* @return The element to be visited by this iterator.
*/
abstract protected E resolve(S e);
}