/*
* Mojito Distributed Hash Table (Mojito DHT)
* Copyright (C) 2006-2007 LimeWire LLC
*
* 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; either version 2 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 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
package org.limewire.mojito.util;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import org.limewire.mojito.KUID;
import org.limewire.mojito.db.DHTValueEntity;
import org.limewire.mojito.db.DHTValueType;
import org.limewire.mojito.db.Storable;
import org.limewire.mojito.routing.Contact;
import org.limewire.mojito.routing.RouteTable;
import org.limewire.mojito.routing.RouteTable.SelectMode;
import org.limewire.mojito.settings.DatabaseSettings;
import org.limewire.mojito.settings.KademliaSettings;
/**
* Miscellaneous utilities for the Database.
*/
public class DatabaseUtils {
private DatabaseUtils() {}
/**
* Returns the expiration time of the given DHTValue.
*/
public static long getExpirationTime(RouteTable routeTable, DHTValueEntity entity) {
KUID primaryKey = entity.getPrimaryKey();
int k = KademliaSettings.REPLICATION_PARAMETER.getValue();
Collection<Contact> nodes = routeTable.select(primaryKey, k, SelectMode.ALL);
long creationTime = entity.getCreationTime();
long expirationTime = DatabaseSettings.VALUE_EXPIRATION_TIME.getValue();
// If there are less than k Nodes or the local Node is member
// of the k-closest Nodes then use the default expiration time
if (nodes.size() < k || nodes.contains(routeTable.getLocalNode())) {
return creationTime + expirationTime;
// The value expires inversely proportional otherwise by using
// the xor distance
} else {
KUID valueBucketId = routeTable.getBucket(primaryKey).getBucketID();
KUID localBucketId = routeTable.getBucket(routeTable.getLocalNode().getNodeID()).getBucketID();
KUID xor = localBucketId.xor(valueBucketId);
int lowestSetBit = xor.toBigInteger().getLowestSetBit();
float ratio = 0.0f;
if (lowestSetBit >= 0) {
ratio = (float)(KUID.LENGTH_IN_BITS - lowestSetBit) / (float)KUID.LENGTH_IN_BITS;
}
return creationTime + (long)(expirationTime - (expirationTime * ratio));
}
}
/**
* Returns whether or not the given DHTValue has expired.
*/
public static boolean isExpired(RouteTable routeTable, DHTValueEntity entity) {
return System.currentTimeMillis() >= getExpirationTime(routeTable, entity);
}
public static boolean isPublishingRequired(Storable storable) {
return isPublishingRequired(storable.getPublishTime(), storable.getLocationCount());
}
public static boolean isPublishingRequired(long publishingTime, int locationCount) {
if (publishingTime <= 0L || locationCount <= 0) {
return true;
}
long t = ((locationCount
* DatabaseSettings.VALUE_REPUBLISH_INTERVAL.getValue())
/ KademliaSettings.REPLICATION_PARAMETER.getValue());
// Do never republish more than every X minutes
long nextPublishTime = Math.max(t,
DatabaseSettings.MIN_VALUE_REPUBLISH_INTERVAL.getValue());
long time = publishingTime + nextPublishTime;
return System.currentTimeMillis() >= time;
}
public static boolean isDHTValueType(DHTValueType valueType, DHTValueEntity entity) {
return valueType.equals(DHTValueType.ANY)
|| valueType.equals(entity.getValue().getValueType());
}
public static Collection<? extends DHTValueEntity> filter(DHTValueType valueType,
Collection<? extends DHTValueEntity> entities) {
if (valueType.equals(DHTValueType.ANY)) {
return entities;
}
List<DHTValueEntity> filtered = new ArrayList<DHTValueEntity>(entities.size());
for (DHTValueEntity entity : entities) {
if (isDHTValueType(valueType, entity)) {
filtered.add(entity);
}
}
return filtered;
}
public static DHTValueEntity getFirstEntityFor(DHTValueType valueType,
Collection<? extends DHTValueEntity> entities) {
for (DHTValueEntity entity : entities) {
if (isDHTValueType(valueType, entity)) {
return entity;
}
}
return null;
}
}