com.bigdata.striterator.Appender 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 Aug 7, 2008
*/
package com.bigdata.striterator;
import java.util.Iterator;
import java.util.NoSuchElementException;
import cutthecrap.utils.striterators.ICloseableIterator;
/**
* Appender pattern tacks on another iterator when the source iterator is
* exhausted.
*
* @author Bryan Thompson
* @version $Id$
*/
public class Appender,E> implements IFilter {
private static final long serialVersionUID = 1307691066685808103L;
private final int chunkSize;
private final I src2;
public Appender(final I src2) {
this(IChunkedIterator.DEFAULT_CHUNK_SIZE, src2);
}
public Appender(final int chunkSize, final I src2) {
if (chunkSize <= 0)
throw new IllegalArgumentException();
if (src2 == null)
throw new IllegalArgumentException();
this.chunkSize = chunkSize;
this.src2 = src2;
}
@SuppressWarnings({ "rawtypes", "unchecked" })
public I filter(final I src) {
return (I) new AppendingIterator(chunkSize, src, src2);
}
/**
* Appending iterator implementation.
*
* @author Bryan Thompson
* @version $Id$
* @param
* @param
*/
private static class AppendingIterator, E>
implements IChunkedIterator {
private final int chunkSize;
private final I src1;
private final I src2;
/**
* Initially set to the value supplied to the ctor. When that source is
* exhausted, this is set to {@link #src2}. When the second source is
* exhausted then the total iterator is exhausted.
*/
private I src;
private boolean firstSource = true;
public AppendingIterator(final int chunkSize, final I src, final I src2) {
this.chunkSize = chunkSize;
this.src = src;
this.src1 = src;
this.src2 = src2;
}
@Override
public boolean hasNext() {
if (src == null) {
// exhausted.
return false;
}
if (src.hasNext())
return true;
if (firstSource) {
// start on the 2nd source.
src = src2;
firstSource = false;
} else {
// exhausted.
src = null;
}
return hasNext();
}
@Override
public E next() {
if (src == null)
// exhausted.
throw new NoSuchElementException();
return src.next();
}
@Override
public void remove() {
if (src == null)
throw new IllegalStateException();
src.remove();
}
@Override
public void close() {
// exhausted.
src = null;
if (src1 instanceof ICloseableIterator) {
((ICloseableIterator) src1).close();
}
if (src2 instanceof ICloseableIterator) {
((ICloseableIterator) src2).close();
}
}
/**
* 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;
}
}
}
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