com.bigdata.striterator.ChunkedWrappedIterator 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 Nov 11, 2007
*/
package com.bigdata.striterator;
import java.util.Arrays;
import java.util.Iterator;
import java.util.NoSuchElementException;
import org.apache.log4j.Logger;
import com.bigdata.relation.accesspath.IElementFilter;
import cutthecrap.utils.striterators.Filter;
import cutthecrap.utils.striterators.ICloseableIterator;
import cutthecrap.utils.striterators.Striterator;
/**
* Converts an Iterator into chunked iterator.
*
* @author Bryan Thompson
* @version $Id$
*/
public class ChunkedWrappedIterator implements IChunkedOrderedIterator {
private static transient final Logger log = Logger.getLogger(ChunkedWrappedIterator.class);
private volatile boolean open = true;
private final Class elementClass;
/**
* The source iterator supplied by the caller. If this is an
* {@link ICloseableIterator} then {@link #close()} will drill through and
* close the source as well.
*/
private final Iterator realSource;
/**
* If a filter was specified to the constructor, then this is an iterator
* that filters the {@link #realSource}.
*/
private final Iterator src;
private final int chunkSize;
private final IKeyOrder keyOrder;
// /** Optional filter applied to the source iterator. */
// private final IElementFilter filter;
private long nchunks = 0L;
private long nelements = 0L;
/**
* Create an iterator that reads from the source.
*
* @param src
* The source iterator.
*/
public ChunkedWrappedIterator(final Iterator src) {
this(src, DEFAULT_CHUNK_SIZE);
}
public ChunkedWrappedIterator(final Iterator src, final int chunkSize) {
this(src, chunkSize, null/* elementClass */);
}
public ChunkedWrappedIterator(final Iterator src, final int chunkSize,
Class elementClass) {
this(src, chunkSize, elementClass, null/* keyOrder */, null/* filter */);
}
public ChunkedWrappedIterator(final Iterator src, final int chunkSize,
final IKeyOrder keyOrder, final IElementFilter filter) {
this(src, chunkSize, null/* elementClass */, keyOrder, filter);
}
/**
* Create an iterator that reads from the source.
*
* @param src
* The source iterator.
* @param chunkSize
* The desired chunk size.
* @param elementClass
* The class for the array component type (optional, but the
* default will use the runtime type of the first element of the
* array which can be too restrictive).
* @param keyOrder
* The order in which the elements will be visited by the source
* iterator if known and null otherwise.
* @param filter
* Optional filter. When non-null only elements
* accepted by the filter will be visited by this iterator.
*/
@SuppressWarnings("unchecked")
public ChunkedWrappedIterator(final Iterator src, final int chunkSize,
final Class elementClass, final IKeyOrder keyOrder,
final IElementFilter filter) {
if (src == null)
throw new IllegalArgumentException();
if (chunkSize <= 0)
throw new IllegalArgumentException();
this.elementClass = elementClass;
this.realSource = src;
/*
* If a filter was specified then use a Striterator to filter the source
* iterator such that it includes only those SPOs that match the filter.
*/
this.src = (filter == null //
? src //
: new Striterator(src).addFilter(new Filter(){
private static final long serialVersionUID = 1L;
@Override
public boolean isValid(final Object arg0) {
return filter.isValid((E) arg0);
}}
)
);
this.chunkSize = chunkSize;
this.keyOrder = keyOrder;
// this.filter = filter;
}
@Override
public void close() {
if (open) {
open = false;
if (realSource instanceof ICloseableIterator) {
((ICloseableIterator) realSource).close();
}
if (log.isInfoEnabled())
log.info("#chunks=" + nchunks + ", #elements=" + nelements);
}
}
/**
* Return true if there are elements in the source iterator.
*/
@Override
public boolean hasNext() {
if(open && src.hasNext())
return true;
/*
* Explicit close() so we close the source also when this iterator is
* exhausted.
*
* @see https://sourceforge.net/apps/trac/bigdata/ticket/361
*/
close();
return false;
}
/**
* The next element from the source iterator.
*/
@Override
public E next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
final E e = src.next();
nelements++;
return e;
}
/**
* The next chunk of elements in whatever order the were visited by
* {@link #next()}.
*/
@Override
@SuppressWarnings("unchecked")
public E[] nextChunk() {
if (!hasNext()) {
throw new NoSuchElementException();
}
int n = 0;
E[] chunk = null;
while (open && src.hasNext() && n < chunkSize) {
final E t = src.next();
if (chunk == null) {
/*
* Dynamically instantiate an array of the same component type
* as the objects that we are visiting.
*/
chunk = (E[]) java.lang.reflect.Array.newInstance(
(elementClass != null ? elementClass : 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((elementClass != null ? elementClass
: chunk[0].getClass()), n);
System.arraycopy(chunk, 0, tmp, 0, n);
chunk = tmp;
}
nchunks++;
nelements += n;
if (log.isDebugEnabled())
log.debug("#chunks=" + nchunks + ", chunkSize=" + chunk.length
+ ", #elements=" + nelements);
return chunk;
}
/**
* Delegated to the source iterator.
*/
@Override
public void remove() {
src.remove();
}
@Override
public IKeyOrder getKeyOrder() {
return keyOrder;
}
@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;
}
}
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