/*
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 Apr 21, 2009
*/
package com.bigdata.relation.accesspath;
import cern.colt.GenericSorting;
import cern.colt.Swapper;
import cern.colt.function.IntComparator;
/**
* Utility for merge sort of chunks. Merge sorts are used when two or more
* ordered chunks have been combined into a single chunk. Since the source
* chunks were already ordered, the merge sort is less expensive than performing
* a full sort on the combined chunk.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*/
public class ChunkMergeSortHelper {
/**
* In place merge sort.
*
* @param <E>
* The generic type of the elements in the chunk.
* @param chunk
* The chunk.
*/
public static <E> void mergeSort(final E[] chunk) {
if (chunk == null)
throw new IllegalArgumentException();
if (chunk.length == 0)
return;
GenericSorting.mergeSort(
0, // fromIndex
chunk.length, // toIndex
new MyIntComparator((Comparable[]) chunk),
new MySwapper((Object[]) chunk));
return;
}
/**
* Implementation for data in an array whose element type implements
* {@link Comparable}.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
*/
final static private class MyIntComparator implements IntComparator {
@SuppressWarnings("rawtypes")
private final Comparable[] a;
@SuppressWarnings("rawtypes")
public MyIntComparator(final Comparable[] a) {
this.a = a;
}
@SuppressWarnings("unchecked")
public int compare(final int o1, final int o2) {
return a[o1].compareTo(a[o2]);
}
}
/**
* Implementation swaps object references in an array.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
*/
final static private class MySwapper implements Swapper {
private final Object[] a;
public MySwapper(final Object[] a) {
this.a = a;
}
public void swap(final int i, final int j) {
final Object t = a[i];
a[i] = a[j];
a[j] = t;
}
}
}