/**
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
*/
package com.bigdata.journal;
import java.io.File;
import java.nio.ByteBuffer;
/**
* Transient buffer strategy uses a direct buffer but never writes on disk.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*
* @see BufferMode#Transient
*/
public class TransientBufferStrategy extends BasicBufferStrategy {
/**
* The root blocks.
*/
final private IRootBlockView rootBlocks[] = new IRootBlockView[2];
/**
* Either zero (0) or one (1).
*/
private int currentRootBlock = 0;
/**
* Note: I have not observed much performance gain from the use of a direct
* buffer for the transient mode. Further, there is a BUG related to release
* of direct {@link ByteBuffer}s so they are NOT in general recommended
* here.
*/
TransientBufferStrategy(int offsetBits,long initialExtent, long maximumExtent,
boolean useDirectBuffers) {
super( maximumExtent,
offsetBits,
0, // nextOffset
0, // headerSize
initialExtent, //
BufferMode.Transient, //
(useDirectBuffers //
? ByteBuffer.allocateDirect((int) initialExtent)//
: ByteBuffer.allocate((int) initialExtent)//
),
false// readOnly
);
}
public void deleteResources() {
if( isOpen() ) {
throw new IllegalStateException();
}
// NOP.
}
public void force(boolean metadata) {
// NOP.
}
/**
* Always returns <code>null</code>.
*/
public File getFile() {
return null;
}
final public boolean isStable() {
return false;
}
public boolean isFullyBuffered() {
return true;
}
public void writeRootBlock(final IRootBlockView rootBlock,
final ForceEnum forceOnCommit) {
if (rootBlock == null)
throw new IllegalArgumentException();
currentRootBlock = rootBlock.isRootBlock0() ? 0 : 1;
rootBlocks[currentRootBlock] = rootBlock;
}
/**
* There is no header.
*
* @return ZERO (0).
*/
final public int getHeaderSize() {
return 0;
}
public ByteBuffer readRootBlock(boolean rootBlock0) {
return rootBlocks[rootBlock0 ? 0 : 1].asReadOnlyBuffer();
}
/**
* Protocol support for HAWrite
*/
public void setNextOffset(long lastOffset) {
// void
}}