/*
* Created on 13-May-2005
* Created by Paul Gardner
* Copyright (C) 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.util.bloom.impl;
public class
BloomFilterAddRemove4Bit
extends BloomFilterImpl
{
private byte[] map;
public
BloomFilterAddRemove4Bit(
int _max_entries )
{
super( _max_entries );
// 4 bits per entry
map = new byte[(getMaxEntries()+1)/2];
}
protected int
trimValue(
int value )
{
if ( value < 0 ){
return( 0 );
}else if ( value > 15 ){
return( 15 );
}else{
return( value );
}
}
protected int
getValue(
int index )
{
byte b = map[index/2];
if ( index % 2 == 0 ){
return(( b&0x0f ) & 0xff );
}else{
return(((b>>4)&0x0f) & 0xff );
}
}
protected int
incValue(
int index )
{
int original_value = getValue( index );
if ( original_value >= 15 ){
return( 15 );
}
setValue( index, (byte)(original_value+1) );
return( original_value );
}
protected int
decValue(
int index )
{
int original_value = getValue( index );
if ( original_value <= 0 ){
return( 0 );
}
setValue( index, (byte)(original_value-1));
return( original_value );
}
private void
setValue(
int index,
byte value )
{
byte b = map[index/2];
if ( index % 2 == 0 ){
b = (byte)((b&0xf0) | value );
}else{
b = (byte)((b&0x0f) | (value<<4)&0xf0 );
}
// System.out.println( "setValue[" + index + "]:" + Integer.toHexString( map[index/2]&0xff) + "->" + Integer.toHexString( b&0xff ));
map[index/2] = b;
}
}
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