/*
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 Jun 20, 2008
*/
package com.bigdata.relation.accesspath;
/**
* A thread-safe buffer backed by a fixed capacity array. Concrete
* implementations must empty the buffer in {@link #flush(int, Object[])}.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*/
abstract public class AbstractArrayBuffer<E> implements IBuffer<E> {
// protected static final Logger log = Logger.getLogger(AbstractArrayBuffer.class);
//
// protected static final boolean INFO = log.isInfoEnabled();
//
// protected static final boolean DEBUG = log.isDebugEnabled();
/**
* The capacity of the backing buffer.
*/
protected final int capacity;
/**
* The component type of the backing byte, used when a new instance is
* allocated.
*/
protected final Class cls;
/**
* An optional filter for keeping elements out of the buffer.
*/
protected final IElementFilter<E> filter;
protected int size;
protected E[] buffer;
/**
* @param capacity
* The capacity of the backing buffer.
* @param cls
* Array instances of this component type will be allocated.
* @param filter
* An optional filter for keeping elements out of the buffer.
*/
protected AbstractArrayBuffer(final int capacity, final Class cls,
final IElementFilter<E> filter) {
if (capacity <= 0)
throw new IllegalArgumentException();
if (cls == null)
throw new IllegalArgumentException();
this.capacity = capacity;
this.cls = cls;
this.filter = filter;
}
/**
* If {@link #size()} reports zero(0).
*/
public boolean isEmpty() {
return size == 0;
}
/**
* The approximate #of elements in the buffer.
*/
public int size() {
return size;
}
/**
* Filters elements allowed into the buffer.
*
* @param e
* Some element.
*
* @return <code>true</code> iff the buffer accepts the element.
*/
protected boolean accept(final E e) {
if (filter != null) {
if(!filter.isValid(e)) {
// rejected by the filter.
// if(DEBUG) {
//
// log.debug("rejected: element="+e+", filter="+filter);
//
// }
return false;
}
}
return true;
}
@SuppressWarnings("unchecked")
public void add(final E e) {
if (e == null)
throw new IllegalArgumentException();
// if(DEBUG) {
//
// log.debug("element="+e);
//
// }
if (accept(e)) {
synchronized (this) {
if (buffer == null) {
buffer = (E[]) java.lang.reflect.Array.newInstance(cls,
capacity);
} else if (size == buffer.length) {
flush();
}
// try {
buffer[size++] = e;
// } catch (ArrayStoreException ex) {
// throw new RuntimeException("bufferClass="
// + buffer.getClass()
// + "["
// + buffer.getClass().getComponentType()
// + "]"
// + ", e.class="
// + e.getClass()
// + (e.getClass().getComponentType() != null ? "["
// + e.getClass().getComponentType() + "]"
// : ""));
// }
}
}
}
synchronized public long flush() {
if (size > 0) {
// if (INFO) {
//
// log.info("flushing buffer with " + size + " elements");
//
// }
final long nwritten = flush(size, buffer);
counter += nwritten;
// if (INFO) {
//
// log.info("wrote " + nwritten + " elements, cumulative total="
// + counter);
//
// }
clearBuffer();
}
return counter;
}
private long counter = 0L;
synchronized public void reset() {
// if(INFO) {
//
// log.info("Resetting buffer state and counter.");
//
// }
clearBuffer();
counter = 0L;
}
/** Clear hard references from the buffer for better GC. */
private void clearBuffer() {
for (int i = 0; i < size; i++) {
buffer[i] = null;
}
// the buffer is now empty.
size = 0;
}
/**
* This method is automatically invoked if the buffer is flushed and it is
* non-empty. The implementation is required to dispose of the contents of
* the buffer. The caller is already synchronized on <i>this</i> so no
* further synchronization is necessary. It is assumed that the contents of
* the buffer have been safely disposed of when this method returns.
*
* @param n
* The #of elements in the array.
* @param a
* The array of elements.
*
* @return The #of elements that were modified in the backing relation when
* the buffer was flushed (unlike {@link #flush()}, this is not a
* cumulative counter, but the #of modified elements in the relation
* for this operation only).
*/
abstract protected long flush(int n, E[] a);
}