/**
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 Nov 17, 2006
*/
package com.bigdata.btree;
import com.bigdata.btree.data.IAbstractNodeData;
/**
* A persistent object.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*/
abstract public class PO implements IIdentityAccess, IDirty {
/**
* The persistent identity (defined when the object is actually
* persisted).
*/
transient protected long identity = NULL;
/**
* True iff the object is deleted.
*/
transient protected boolean deleted = false;
/**
* @todo Historically, a mutable node was always non-persistent. With the
* introduction of coding of nodes and leaves for transient B+Trees on
* eviction from the write retention queue, those nodes and leaves
* become read-only when they are coded without becoming persistent.
* While {@link IAbstractNodeData#isCoded()} currently reflects the
* same distinction as {@link IAbstractNodeData#isReadOnly()}, that
* might not always be the case. For example, it is possible to have
* mutable coded node/leaf impls.
* <p>
* There are a number of asserts for this which are violated by the
* change to support coding of nodes and leaves for the transient
* B+Tree. Often, those asserts need to test
* {@link IAbstractNodeData#isReadOnly()} instead, since that reflects
* the concern that the node/leaf is not mutable.
*/
final public boolean isPersistent() {
return identity != NULL;
}
final public boolean isDeleted() {
return deleted;
}
final public long getIdentity() throws IllegalStateException {
if (identity == NULL) {
throw new IllegalStateException();
}
return identity;
}
/**
* Used by the store to set the persistent identity.
*
* Note: This method should not be public.
*
* @param identity
* The identity.
*
* @throws IllegalStateException
* If the identity is already defined.
*/
// Note: public since also used by the htree package
public void setIdentity(final long key) throws IllegalStateException {
if (key == NULL) {
throw new IllegalArgumentException();
}
if (this.identity != NULL) {
throw new IllegalStateException("Object already persistent");
}
if( this.deleted) {
throw new IllegalStateException("Object is deleted");
}
this.identity = key;
}
/**
* New objects are considered to be dirty. When an object is
* deserialized from the store the dirty flag MUST be explicitly
* cleared.
*/
transient protected boolean dirty = true;
final public boolean isDirty() {
return dirty;
}
final public void setDirty(final boolean dirty) {
this.dirty = dirty;
}
/**
* Extends the basic behavior to display the persistent identity of the
* object iff the object is persistent and to mark objects that have been
* deleted.
*/
public String toString() {
return toShortString();
}
/**
* Returns a short representation of the class, identity (if assigned), the
* object instance, and whether or not the {@link PO} is deleted.
*/
public String toShortString() {
final String s;
if (identity != NULL) {
s = super.toString() + "#" + identity;
} else {
s = super.toString();
}
if (deleted) {
return s + "(deleted)";
} else {
return s;
}
}
/**
* Returns a string that may be used to indent a dump of the nodes in
* the tree.
*
* @param height
* The height.
*
* @return A string suitable for indent at that height.
*/
protected static String indent(final int height) {
if( height == -1 ) {
// The height is not defined.
return "";
}
return ws.substring(0, Math.min(ws.length(), height * 4));
}
private static final transient String ws = " ";
}