/*
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.Iterator;
import java.util.NoSuchElementException;
import cutthecrap.utils.striterators.ICloseableIterator;
/**
* Merge sort of two iterators with duplicates suppressed. The elements must be
* comparable. Each source iterator must deliver its elements in a total
* ordering in order for the aggregate iterator to maintain a total ordering.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*/
public class MergeFilter<I extends Iterator<E>, E extends Comparable<E>>
implements IFilter<I, E, E> {
private static final long serialVersionUID = -3593674406822688011L;
private final int chunkSize;
private final I src2;
public MergeFilter(final I src2) {
this( IChunkedIterator.DEFAULT_CHUNK_SIZE, src2 );
}
public MergeFilter(final int chunkSize, final I src2) {
if (chunkSize <= 0)
throw new IllegalArgumentException();
if (src2 == null)
throw new IllegalArgumentException();
this.chunkSize = chunkSize;
this.src2 = src2;
}
@Override
@SuppressWarnings({ "unchecked", "rawtypes" })
public I filter(final I src) {
return (I) new MergedIterator(chunkSize, src, src2);
}
/**
* Reads on two iterators visiting elements in some natural order and visits
* their order preserving merge (no duplicates).
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
* @param <E>
*/
private static class MergedIterator<I extends Iterator<E>, E extends Comparable<E>>
implements IChunkedIterator<E> {
private final int chunkSize;
private final I src1;
private final I src2;
public MergedIterator(final int chunkSize, final I src1, final I src2) {
this.chunkSize = chunkSize;
this.src1 = src1;
this.src2 = src2;
}
@Override
public void close() {
if(src1 instanceof ICloseableIterator) {
((ICloseableIterator<?>)src1).close();
}
if(src2 instanceof ICloseableIterator) {
((ICloseableIterator<?>)src2).close();
}
}
@Override
public boolean hasNext() {
return tmp1 != null || tmp2 != null || src1.hasNext()
|| src2.hasNext();
}
private E tmp1;
private E tmp2;
@Override
public E next() {
if (!hasNext())
throw new NoSuchElementException();
if (tmp1 == null && src1.hasNext()) {
tmp1 = src1.next();
}
if (tmp2 == null && src2.hasNext()) {
tmp2 = src2.next();
}
if (tmp1 == null) {
// src1 is exhausted so deliver from src2.
final E tmp = tmp2;
tmp2 = null;
return tmp;
}
if (tmp2 == null) {
// src2 is exhausted so deliver from src1.
final E tmp = tmp1;
tmp1 = null;
return tmp;
}
final int cmp = tmp1.compareTo(tmp2);
if (cmp == 0) {
final E tmp = tmp1;
tmp1 = tmp2 = null;
return tmp;
} else if (cmp < 0) {
final E tmp = tmp1;
tmp1 = null;
return tmp;
} else {
final E tmp = tmp2;
tmp2 = null;
return tmp;
}
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
/**
* The next chunk of elements in whatever order they were visited by
* {@link #next()}.
*/
@Override
@SuppressWarnings("unchecked")
public E[] nextChunk() {
if (!hasNext()) {
throw new NoSuchElementException();
}
int n = 0;
E[] chunk = null;
while (hasNext() && n < chunkSize) {
final 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.
final 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;
}
}
}