/*
* Created on 03-Feb-2005
* Created by Paul Gardner
* Copyright (C) 2004, 2005, 2006 Aelitis, All Rights Reserved.
*
* 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* AELITIS, SAS au capital de 46,603.30 euros
* 8 Allee Lenotre, La Grille Royale, 78600 Le Mesnil le Roi, France.
*
*/
package com.aelitis.azureus.core.dht.db.impl;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.util.*;
import org.gudy.azureus2.core3.util.ByteFormatter;
import org.gudy.azureus2.core3.util.Debug;
import org.gudy.azureus2.core3.util.HashWrapper;
import org.gudy.azureus2.core3.util.SystemTime;
// import org.gudy.azureus2.core3.util.SHA1Hasher;
import com.aelitis.azureus.core.dht.*;
import com.aelitis.azureus.core.dht.impl.DHTLog;
import com.aelitis.azureus.core.dht.transport.DHTTransportContact;
import com.aelitis.azureus.core.util.bloom.BloomFilter;
import com.aelitis.azureus.core.util.bloom.BloomFilterFactory;
/**
* @author parg
*
*/
public class
DHTDBMapping
{
private static final boolean TRACE_ADDS = false;
private DHTDBImpl db;
private HashWrapper key;
private ShortHash short_key;
private DHTStorageKey adapter_key;
// maps are access order, most recently used at tail, so we cycle values
private Map<HashWrapper,DHTDBValueImpl> direct_originator_map_may_be_null;
private Map<HashWrapper,DHTDBValueImpl> indirect_originator_value_map = createLinkedMap();
private int hits;
private int direct_data_size;
private int indirect_data_size;
private int local_size;
private byte diversification_state = DHT.DT_NONE;
private static final int IP_COUNT_BLOOM_SIZE_INCREASE_CHUNK = 50;
// 4 bit filter - counts up to 15
private Object ip_count_bloom_filter;
protected
DHTDBMapping(
DHTDBImpl _db,
HashWrapper _key,
boolean _local )
{
db = _db;
key = _key;
short_key = new ShortHash( key.getBytes());
try{
if ( db.getAdapter() != null ){
adapter_key = db.getAdapter().keyCreated( key, _local );
if ( adapter_key != null ){
diversification_state = adapter_key.getDiversificationType();
}
}
}catch( Throwable e ){
Debug.printStackTrace(e);
}
}
protected Map<HashWrapper,DHTDBValueImpl>
createLinkedMap()
{
return( new LinkedHashMap<HashWrapper,DHTDBValueImpl>(1, 0.75f, true ));
}
protected HashWrapper
getKey()
{
return( key );
}
protected ShortHash
getShortKey()
{
return( short_key );
}
protected void
updateLocalContact(
DHTTransportContact contact )
{
// pull out all the local values, reset the originator and then
// re-add them
if ( direct_originator_map_may_be_null == null ){
return;
}
List<DHTDBValueImpl> changed = new ArrayList<DHTDBValueImpl>();
Iterator<DHTDBValueImpl> it = direct_originator_map_may_be_null.values().iterator();
while( it.hasNext()){
DHTDBValueImpl value = it.next();
if ( value.isLocal()){
value.setOriginatorAndSender( contact );
changed.add( value );
direct_data_size -= value.getValue().length;
local_size -= value.getValue().length;
it.remove();
informDeleted( value );
}
}
for (int i=0;i<changed.size();i++){
add(changed.get(i));
}
}
// All values have
// 1) a key
// 2) a value
// 3) an originator (the contact who originally published it)
// 4) a sender (the contact who sent it, could be diff for caches)
// rethink time :P
// a) for a value where sender + originator are the same we store a single value
// b) where sender + originator differ we store an entry per originator/value pair as the
// send can legitimately forward multiple values but their originator should differ
// c) the code that adds values is responsible for not accepting values that are either
// to "far away" from our ID, or that are cache-forwards from a contact "too far"
// away.
// for a given key
// c) we only allow up to 8 entries per sending IP address (excluding port)
// d) if multiple entries have the same value the value is only returned once
// e) only the originator can delete an entry
// a) prevents a single sender from filling up the mapping with garbage
// b) prevents the same key->value mapping being held multiple times when sent by different caches
// c) prevents multiple senders from same IP filling up, but supports multiple machines behind NAT
// d) optimises responses.
// Note that we can't trust the originator value in cache forwards, we therefore
// need to prevent someone from overwriting a valid originator->value1 mapping
// with an invalid originator->value2 mapping - that is we can't use uniqueness of
// originator
// a value can be "volatile" - this means that the cacher can ping the originator
// periodically and delete the value if it is dead
// the aim here is to
// 1) reduce ability for single contacts to spam the key while supporting up to 8
// contacts on a given IP (assuming NAT is being used)
// 2) stop one contact deleting or overwriting another contact's entry
// 3) support garbage collection for contacts that don't delete entries on exit
// TODO: we should enforce a max-values-per-sender restriction to stop a sender from spamming
// lots of keys - however, for a small DHT we need to be careful
protected void
add(
DHTDBValueImpl new_value )
{
// don't replace a closer cache value with a further away one. in particular
// we have to avoid the case where the original publisher of a key happens to
// be close to it and be asked by another node to cache it!
DHTTransportContact originator = new_value.getOriginator();
DHTTransportContact sender = new_value.getSender();
HashWrapper originator_id = new HashWrapper( originator.getID());
boolean direct = Arrays.equals( originator.getID(), sender.getID());
if ( direct ){
// direct contact from the originator is straight forward
addDirectValue( originator_id, new_value );
// remove any indirect values we might already have for this
Iterator<Map.Entry<HashWrapper,DHTDBValueImpl>> it = indirect_originator_value_map.entrySet().iterator();
List<HashWrapper> to_remove = new ArrayList<HashWrapper>();
while( it.hasNext()){
Map.Entry<HashWrapper,DHTDBValueImpl> entry = it.next();
HashWrapper existing_key = entry.getKey();
DHTDBValueImpl existing_value = entry.getValue();
if ( Arrays.equals( existing_value.getOriginator().getID(), originator.getID())){
to_remove.add( existing_key );
}
}
for (int i=0;i<to_remove.size();i++){
removeIndirectValue((HashWrapper)to_remove.get(i));
}
}else{
// not direct. if we have a value already for this originator then
// we drop the value as the originator originated one takes precedence
if ( direct_originator_map_may_be_null != null &&
direct_originator_map_may_be_null.get( originator_id ) != null ){
return;
}
// rule (b) - one entry per originator/value pair
HashWrapper originator_value_id = getOriginatorValueID( new_value );
DHTDBValueImpl existing_value = indirect_originator_value_map.get( originator_value_id );
if ( existing_value != null ){
addIndirectValue( originator_value_id, new_value );
//System.out.println( " replacing existing" );
}else{
// only add new values if not diversified
if ( diversification_state == DHT.DT_NONE ){
addIndirectValue( originator_value_id, new_value );
}
}
}
}
private HashWrapper
getOriginatorValueID(
DHTDBValueImpl value )
{
DHTTransportContact originator = value.getOriginator();
byte[] originator_id = originator.getID();
// relaxed this due to problems caused by multiple publishes by an originator
// with the same key but variant values (e.g. seed/peer counts). Seeing as we
// only accept cache-forwards from contacts that are "close" enough to us to
// be performing such a forward, the DOS possibilities here are limited (a nasty
// contact can only trash originator values for things it happens to be close to)
return( new HashWrapper( originator_id ));
/*
byte[] value_bytes = value.getValue();
byte[] x = new byte[originator_id.length + value_bytes.length];
System.arraycopy( originator_id, 0, x, 0, originator_id.length );
System.arraycopy( value_bytes, 0, x, originator_id.length, value_bytes.length );
HashWrapper originator_value_id = new HashWrapper( new SHA1Hasher().calculateHash( x ));
return( originator_value_id );
*/
}
protected void
addHit()
{
hits++;
}
protected int
getHits()
{
return( hits );
}
protected int
getIndirectSize()
{
return( indirect_data_size );
}
protected int
getDirectSize()
{
// our direct count includes local so remove that here
return( direct_data_size - local_size );
}
protected int
getLocalSize()
{
return( local_size );
}
protected DHTDBValueImpl[]
get(
DHTTransportContact by_who,
int max,
byte flags )
{
if ((flags & DHT.FLAG_STATS) != 0 ){
if ( adapter_key != null ){
try{
ByteArrayOutputStream baos = new ByteArrayOutputStream(64);
DataOutputStream dos = new DataOutputStream( baos );
adapter_key.serialiseStats( dos );
dos.close();
return(
new DHTDBValueImpl[]{
new DHTDBValueImpl(
SystemTime.getCurrentTime(),
baos.toByteArray(),
0,
db.getLocalContact(),
db.getLocalContact(),
true,
DHT.FLAG_STATS,
0,
DHT.REP_FACT_DEFAULT )});
}catch( Throwable e ){
Debug.printStackTrace(e);
}
}
return( new DHTDBValueImpl[0] );
}
List<DHTDBValueImpl> res = new ArrayList<DHTDBValueImpl>();
Set<HashWrapper> duplicate_check = new HashSet<HashWrapper>();
Map<HashWrapper,DHTDBValueImpl>[] maps = new Map[]{ direct_originator_map_may_be_null, indirect_originator_value_map };
for (int i=0;i<maps.length;i++){
Map<HashWrapper,DHTDBValueImpl> map = maps[i];
if ( map == null ){
continue;
}
List<HashWrapper> keys_used = new ArrayList<HashWrapper>();
Iterator<Map.Entry<HashWrapper,DHTDBValueImpl>> it = map.entrySet().iterator();
while( it.hasNext() && ( max==0 || res.size()< max )){
Map.Entry<HashWrapper,DHTDBValueImpl> entry = it.next();
HashWrapper entry_key = entry.getKey();
DHTDBValueImpl entry_value = entry.getValue();
HashWrapper x = new HashWrapper( entry_value.getValue());
if ( duplicate_check.contains( x )){
continue;
}
duplicate_check.add( x );
// zero length values imply deleted values so don't return them
if ( entry_value.getValue().length > 0 ){
res.add( entry_value );
keys_used.add( entry_key );
}
}
// now update the access order so values get cycled
for (int j=0;j<keys_used.size();j++){
map.get( keys_used.get(j));
}
}
informRead( by_who );
DHTDBValueImpl[] v = new DHTDBValueImpl[res.size()];
res.toArray( v );
return( v );
}
protected DHTDBValueImpl
get(
DHTTransportContact originator )
{
// local get
if ( direct_originator_map_may_be_null == null ){
return( null );
}
HashWrapper originator_id = new HashWrapper( originator.getID());
DHTDBValueImpl res = (DHTDBValueImpl)direct_originator_map_may_be_null.get( originator_id );
return( res );
}
protected DHTDBValueImpl
remove(
DHTTransportContact originator )
{
// local remove
HashWrapper originator_id = new HashWrapper( originator.getID());
DHTDBValueImpl res = removeDirectValue( originator_id );
return( res );
}
protected int
getValueCount()
{
if ( direct_originator_map_may_be_null == null ){
return( indirect_originator_value_map.size());
}
return( direct_originator_map_may_be_null.size() + indirect_originator_value_map.size());
}
protected int
getDirectValueCount()
{
if ( direct_originator_map_may_be_null == null ){
return( 0 );
}
return( direct_originator_map_may_be_null.size());
}
protected int
getIndirectValueCount()
{
return( indirect_originator_value_map.size());
}
protected Iterator<DHTDBValueImpl>
getValues()
{
return( new valueIterator( true, true ));
}
protected Iterator<DHTDBValueImpl>
getDirectValues()
{
return( new valueIterator( true, false ));
}
protected Iterator<DHTDBValueImpl>
getIndirectValues()
{
return( new valueIterator( false, true ));
}
protected byte
getDiversificationType()
{
return( diversification_state );
}
protected void
addDirectValue(
HashWrapper value_key,
DHTDBValueImpl value )
{
if ( direct_originator_map_may_be_null == null ){
direct_originator_map_may_be_null = createLinkedMap();
}
DHTDBValueImpl old = (DHTDBValueImpl)direct_originator_map_may_be_null.put( value_key, value );
if ( old != null ){
int old_version = old.getVersion();
int new_version = value.getVersion();
if ( old_version != -1 && new_version != -1 && old_version >= new_version ){
if ( old_version == new_version ){
if ( TRACE_ADDS ){
System.out.println( "addDirect[reset]:" + old.getString() + "/" + value.getString());
}
old.reset(); // update store time as this means we don't need to republish
// as someone else has just done it
}else{
// its important to ignore old versions as a peer's increasing version sequence may
// have been reset and if this is the case we want the "future" values to timeout
if ( TRACE_ADDS ){
System.out.println( "addDirect[ignore]:" + old.getString() + "/" + value.getString());
}
}
// put the old value back!
direct_originator_map_may_be_null.put( value_key, old );
return;
}
if ( TRACE_ADDS ){
System.out.println( "addDirect:" + old.getString() + "/" + value.getString());
}
direct_data_size -= old.getValue().length;
if ( old.isLocal()){
local_size -= old.getValue().length;
}
}else{
if ( TRACE_ADDS ){
System.out.println( "addDirect:[new]" + value.getString());
}
}
direct_data_size += value.getValue().length;
if ( value.isLocal()){
local_size += value.getValue().length;
}
if ( old == null ){
informAdded( value );
}else{
informUpdated( old, value );
}
}
protected DHTDBValueImpl
removeDirectValue(
HashWrapper value_key )
{
if ( direct_originator_map_may_be_null == null ){
return( null );
}
DHTDBValueImpl old = (DHTDBValueImpl)direct_originator_map_may_be_null.remove( value_key );
if ( old != null ){
direct_data_size -= old.getValue().length;
if ( old.isLocal()){
local_size -= old.getValue().length;
}
informDeleted( old );
}
return( old );
}
protected void
addIndirectValue(
HashWrapper value_key,
DHTDBValueImpl value )
{
DHTDBValueImpl old = (DHTDBValueImpl)indirect_originator_value_map.put( value_key, value );
if ( old != null ){
// discard updates that are older than current value
int old_version = old.getVersion();
int new_version = value.getVersion();
if ( old_version != -1 && new_version != -1 && old_version >= new_version ){
if ( old_version == new_version ){
if ( TRACE_ADDS ){
System.out.println( "addIndirect[reset]:" + old.getString() + "/" + value.getString());
}
old.reset(); // update store time as this means we don't need to republish
// as someone else has just done it
}else{
if ( TRACE_ADDS ){
System.out.println( "addIndirect[ignore]:" + old.getString() + "/" + value.getString());
}
}
// put the old value back!
indirect_originator_value_map.put( value_key, old );
return;
}
// vague backwards compatability - if the creation date of the "new" value is significantly
// less than the old then we ignore it (given that creation date is adjusted for time-skew you can
// see the problem with this approach...)
if ( old_version == -1 || new_version == -1 ){
if ( old.getCreationTime() > value.getCreationTime() + 30000 ){
if ( TRACE_ADDS ){
System.out.println( "backward compat: ignoring store: " + old.getString() + "/" + value.getString());
}
// put the old value back!
indirect_originator_value_map.put( value_key, old );
return;
}
}
if ( TRACE_ADDS ){
System.out.println( "addIndirect:" + old.getString() + "/" + value.getString());
}
indirect_data_size -= old.getValue().length;
if ( old.isLocal()){
local_size -= old.getValue().length;
}
}else{
if ( TRACE_ADDS ){
System.out.println( "addIndirect:[new]" + value.getString());
}
}
indirect_data_size += value.getValue().length;
if ( value.isLocal()){
local_size += value.getValue().length;
}
if ( old == null ){
informAdded( value );
}else{
informUpdated( old, value );
}
}
protected DHTDBValueImpl
removeIndirectValue(
HashWrapper value_key )
{
DHTDBValueImpl old = (DHTDBValueImpl)indirect_originator_value_map.remove( value_key );
if ( old != null ){
indirect_data_size -= old.getValue().length;
if ( old.isLocal()){
local_size -= old.getValue().length;
}
informDeleted( old );
}
return( old );
}
protected void
destroy()
{
try{
if ( adapter_key != null ){
Iterator<DHTDBValueImpl> it = getValues();
while( it.hasNext()){
it.next();
it.remove();
}
db.getAdapter().keyDeleted( adapter_key );
}
}catch( Throwable e ){
Debug.printStackTrace(e);
}
}
private void
informDeleted(
DHTDBValueImpl value )
{
boolean direct =
(!value.isLocal())&&
Arrays.equals( value.getOriginator().getID(), value.getSender().getID());
if ( direct ){
removeFromBloom( value );
}
try{
if ( adapter_key != null ){
db.getAdapter().valueDeleted( adapter_key, value );
diversification_state = adapter_key.getDiversificationType();
}
}catch( Throwable e ){
Debug.printStackTrace(e);
}
}
private void
informAdded(
DHTDBValueImpl value )
{
boolean direct =
(!value.isLocal()) &&
Arrays.equals( value.getOriginator().getID(), value.getSender().getID());
if ( direct ){
addToBloom( value );
}
try{
if ( adapter_key != null ){
db.getAdapter().valueAdded( adapter_key, value );
diversification_state = adapter_key.getDiversificationType();
}
}catch( Throwable e ){
Debug.printStackTrace(e);
}
}
private void
informUpdated(
DHTDBValueImpl old_value,
DHTDBValueImpl new_value)
{
boolean old_direct =
(!old_value.isLocal()) &&
Arrays.equals( old_value.getOriginator().getID(), old_value.getSender().getID());
boolean new_direct =
(!new_value.isLocal()) &&
Arrays.equals( new_value.getOriginator().getID(), new_value.getSender().getID());
if ( new_direct && !old_direct ){
addToBloom( new_value );
}
try{
if ( adapter_key != null ){
db.getAdapter().valueUpdated( adapter_key, old_value, new_value );
diversification_state = adapter_key.getDiversificationType();
}
}catch( Throwable e ){
Debug.printStackTrace(e);
}
}
private void
informRead(
DHTTransportContact contact ){
try{
if ( adapter_key != null && contact != null ){
db.getAdapter().keyRead( adapter_key, contact );
diversification_state = adapter_key.getDiversificationType();
}
}catch( Throwable e ){
Debug.printStackTrace(e);
}
}
protected void
addToBloom(
DHTDBValueImpl value )
{
// we don't check for flooding on indirect stores as this could be used to force a
// direct store to be bounced (flood a node with indirect stores before the direct
// store occurs)
DHTTransportContact originator = value.getOriginator();
byte[] address_bytes = originator.getAddress().getAddress().getAddress();
// System.out.println( "addToBloom: existing=" + ip_count_bloom_filter );
if ( ip_count_bloom_filter == null ){
ip_count_bloom_filter = address_bytes;
return;
}
BloomFilter filter;
if ( ip_count_bloom_filter instanceof byte[] ){
byte[] existing_address = (byte[])ip_count_bloom_filter;
ip_count_bloom_filter = filter = BloomFilterFactory.createAddRemove4Bit( IP_COUNT_BLOOM_SIZE_INCREASE_CHUNK );
filter.add( existing_address );
}else{
filter = (BloomFilter)ip_count_bloom_filter;
}
int hit_count = filter.add( address_bytes );
if ( DHTLog.LOCAL_BLOOM_TRACE ){
System.out.println( "direct local add from " + originator.getAddress() + ", hit count = " + hit_count );
}
// allow up to 10% bloom filter utilisation
if ( filter.getSize() / filter.getEntryCount() < 10 ){
rebuildIPBloomFilter( true );
}
if ( hit_count >= 15 ){
db.banContact( originator, "local flood on '" + DHTLog.getFullString( key.getBytes()) + "'" );
}
}
protected void
removeFromBloom(
DHTDBValueImpl value )
{
DHTTransportContact originator = value.getOriginator();
if ( ip_count_bloom_filter == null ){
return;
}
byte[] address_bytes = originator.getAddress().getAddress().getAddress();
if ( ip_count_bloom_filter instanceof byte[] ){
byte[] existing_address = (byte[])ip_count_bloom_filter;
if ( Arrays.equals( address_bytes, existing_address )){
ip_count_bloom_filter = null;
}
return;
}
BloomFilter filter = (BloomFilter)ip_count_bloom_filter;
int hit_count = filter.remove( address_bytes );
if ( DHTLog.LOCAL_BLOOM_TRACE ){
System.out.println( "direct local remove from " + originator.getAddress() + ", hit count = " + hit_count );
}
}
protected void
rebuildIPBloomFilter(
boolean increase_size )
{
BloomFilter new_filter;
int old_size;
if ( ip_count_bloom_filter instanceof BloomFilter ){
old_size = ((BloomFilter)ip_count_bloom_filter).getSize();
}else{
old_size = IP_COUNT_BLOOM_SIZE_INCREASE_CHUNK;
}
if ( increase_size ){
new_filter = BloomFilterFactory.createAddRemove4Bit( old_size + IP_COUNT_BLOOM_SIZE_INCREASE_CHUNK );
}else{
new_filter = BloomFilterFactory.createAddRemove4Bit( old_size );
}
try{
// only do flood prevention on direct stores as we can't trust the originator
// details for indirect and this can be used to DOS a direct store later
Iterator<DHTDBValueImpl> it = getDirectValues();
int max_hits = 0;
while( it.hasNext()){
DHTDBValueImpl val = it.next();
if ( !val.isLocal()){
// logger.log( " adding " + val.getOriginator().getAddress());
int hits = new_filter.add( val.getOriginator().getAddress().getAddress().getAddress());
if ( hits > max_hits ){
max_hits = hits;
}
}
}
if ( DHTLog.LOCAL_BLOOM_TRACE ){
db.log( "Rebuilt local IP bloom filter, size = " + new_filter.getSize() + ", entries =" + new_filter.getEntryCount()+", max hits = " + max_hits );
}
}finally{
ip_count_bloom_filter = new_filter;
}
}
protected void
print()
{
int entries;
if ( ip_count_bloom_filter == null ){
entries = 0;
}else if ( ip_count_bloom_filter instanceof byte[] ){
entries = 1;
}else{
entries = ((BloomFilter)ip_count_bloom_filter).getEntryCount();
}
System.out.println(
ByteFormatter.encodeString( key.getBytes()) + ": " +
"dir=" + (direct_originator_map_may_be_null==null?0:direct_originator_map_may_be_null.size()) + "," +
"indir=" + indirect_originator_value_map.size() + "," +
"bloom=" + entries );
System.out.println( " indirect" );
Iterator<DHTDBValueImpl> it = getIndirectValues();
while( it.hasNext()){
DHTDBValueImpl val = (DHTDBValueImpl)it.next();
System.out.println( " " + val.getOriginator().getString() + ": " + new String( val.getValue()));
}
}
protected class
valueIterator
implements Iterator<DHTDBValueImpl>
{
private List<Map<HashWrapper,DHTDBValueImpl>> maps = new ArrayList<Map<HashWrapper,DHTDBValueImpl>>(2);
private int map_index = 0;
private Map<HashWrapper,DHTDBValueImpl> map;
private Iterator<DHTDBValueImpl> it;
private DHTDBValueImpl value;
protected
valueIterator(
boolean direct,
boolean indirect )
{
if ( direct && direct_originator_map_may_be_null != null ){
maps.add( direct_originator_map_may_be_null );
}
if ( indirect ){
maps.add( indirect_originator_value_map );
}
}
public boolean
hasNext()
{
if ( it != null && it.hasNext()){
return( true );
}
while( map_index < maps.size() ){
map = maps.get(map_index++);
it = map.values().iterator();
if ( it.hasNext()){
return( true );
}
}
return( false );
}
public DHTDBValueImpl
next()
{
if ( hasNext()){
value = (DHTDBValueImpl)it.next();
return( value );
}
throw( new NoSuchElementException());
}
public void
remove()
{
if ( it == null ){
throw( new IllegalStateException());
}
if ( value != null ){
if( value.isLocal()){
local_size -= value.getValue().length;
}
if ( map == indirect_originator_value_map ){
indirect_data_size -= value.getValue().length;
}else{
direct_data_size -= value.getValue().length;
}
// remove before informing
it.remove();
informDeleted( value );
value = null;
}else{
throw( new IllegalStateException());
}
}
}
public static class
ShortHash
{
private byte[] bytes;
private int hash_code;
protected
ShortHash(
byte[] _bytes )
{
bytes = _bytes;
int hc = 0;
for (int i=0; i<DHTDBImpl.QUERY_STORE_REQUEST_ENTRY_SIZE; i++) {
hc = 31*hc + bytes[i];
}
hash_code = hc;
}
public final boolean
equals(
Object o)
{
if( !( o instanceof ShortHash )){
return false;
}
ShortHash other = (ShortHash)o;
byte[] other_hash = other.bytes;
for ( int i=0;i<DHTDBImpl.QUERY_STORE_REQUEST_ENTRY_SIZE;i++){
if ( bytes[i] != other_hash[i] ){
return( false );
}
}
return( true );
}
public int
hashCode()
{
return( hash_code );
}
}
}