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package de.lmu.ifi.dbs.elki.database.ids.integer;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2011
Ludwig-Maximilians-Universität München
Lehr- und Forschungseinheit für Datenbanksysteme
ELKI Development Team
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
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 Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.util.ArrayList;
import java.util.BitSet;
import de.lmu.ifi.dbs.elki.database.ids.DBID;
import de.lmu.ifi.dbs.elki.database.ids.DBIDFactory;
import de.lmu.ifi.dbs.elki.database.ids.DBIDRange;
import de.lmu.ifi.dbs.elki.logging.Logging;
/**
* Slightly more advanced DBID management, that allows reuse of DBIDs.
*
* @author Erich Schubert
*
* @apiviz.stereotype factory
* @apiviz.uses IntegerDBID oneway - - «create»
* @apiviz.uses IntegerDBIDPair oneway - - «create»
* @apiviz.uses IntegerDBIDRange oneway - - «create»
*/
public class ReusingDBIDFactory extends SimpleDBIDFactory {
/**
* Logging for error messages.
*/
private static final Logging logger = Logging.getLogger(ReusingDBIDFactory.class);
/**
* Bit set to keep track of dynamic DBIDs
*/
BitSet dynamicUsed = new BitSet();
/**
* Keep track of the lowest unused dynamic DBID
*/
int dynamicStart = 0;
// TODO: add an offset, to save keeping long bit sets of 1s for heavy dynamic use?
/**
* Returned range allocations
*/
ArrayList<IntegerDBIDRange> returnedAllocations = new ArrayList<IntegerDBIDRange>();
/**
* Constructor
*/
public ReusingDBIDFactory() {
super();
}
@Override
public synchronized DBID generateSingleDBID() {
dynamicStart = dynamicUsed.nextClearBit(dynamicStart);
dynamicUsed.set(dynamicStart);
return DBIDFactory.FACTORY.importInteger(-(dynamicStart + 1));
}
@Override
public synchronized void deallocateSingleDBID(DBID id) {
if (id.getIntegerID() >= 0) {
logger.warning("Single DBID returned is from a range allocation!");
return;
}
int pos = - id.getIntegerID() - 1;
dynamicUsed.clear(pos);
dynamicStart = Math.min(dynamicStart, pos);
}
@Override
public synchronized DBIDRange generateStaticDBIDRange(int size) {
for (int i = 0; i < returnedAllocations.size(); i++) {
IntegerDBIDRange alloc = returnedAllocations.get(i);
if (alloc.size() == size) {
returnedAllocations.remove(i);
return alloc;
}
}
for (int i = 0; i < returnedAllocations.size(); i++) {
IntegerDBIDRange alloc = returnedAllocations.get(i);
if (alloc.size() > size) {
IntegerDBIDRange retalloc = new IntegerDBIDRange(alloc.start, size);
alloc = new IntegerDBIDRange(alloc.start + size, alloc.size() - size);
returnedAllocations.set(i, alloc);
return retalloc;
}
}
return super.generateStaticDBIDRange(size);
}
@Override
public synchronized void deallocateDBIDRange(DBIDRange range) {
// TODO: catch an eventual cast exception?
returnedAllocations.add((IntegerDBIDRange)range);
}
}
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