On Sunday, September 8, 2002, at 11:52 , Dmitri Colebatch wrote:
> unjustifyable desire to have a relatively easy way of identifying rows.
Right. Why do it the easy way, when you can make it complicate :-)
> UUIDs are definately quicker from a performance pov.... I'll eventually
> come around (o:
Attached is some lame code to get you started.
Cheers,
PA.
//
// ===========================================================================
//
// Title: SZUUID.java
// Description: [Description]
// Author: Raphael Szwarc <[EMAIL PROTECTED]>
// Creation Date: Sat Sep 08 2001
// Legal: Copyright (C) 2001 Raphael Szwarc. All Rights Reserved.
//
// This file contains Original Code and/or Modifications of Original Code
// as defined in and that are subject to the Rapha�l Szwarc Public Source
// License Version 1.0 (the 'License'). You may not use this file except in
// compliance with the License.
//
// Please obtain a copy of the License at <[EMAIL PROTECTED]> and read it
// before using this file.
//
// The Original Code and all software distributed under the License are
// distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
// EXPRESS OR IMPLIED, AND Rapha�l Szwarc HEREBY DISCLAIMS ALL SUCH WARRANTIES,
// INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
//
// Please see the License for the specific language governing rights and
// limitations under the License.
//
// ---------------------------------------------------------------------------
//
package alt.dev.szfoundation;
import java.net.InetAddress;
import java.util.zip.Checksum;
import java.util.zip.CRC32;
import java.util.Arrays;
public final class SZUUID extends Object
{
// ===========================================================================
// Constant(s)
// ---------------------------------------------------------------------------
public static final int Length = 16; //
LoTime-HiTime-Unique-Sequence-Node
private static final int LoTimeIndex = 0; // int -> 4 bytes
private static final int HiTimeIndex = 4; // short -> 2 bytes
private static final int UniqueIndex = 6; // int -> 4 bytes
private static final int SequenceIndex = 10; // short -> 2 bytes
private static final int NodeIndex = 12; // int -> 4 bytes
// ===========================================================================
// Class variable(s)
// ---------------------------------------------------------------------------
private static final int _unique = new Object().hashCode(); // new
Object().hashCode()
private static short _sequence = Short.MIN_VALUE; //
_sequence++
private static int _node = 0; //
InetAddress.getLocalHost().getAddress().hashCode()
private static final Checksum _checksum = new CRC32();
// ===========================================================================
// Instance variable(s)
// ---------------------------------------------------------------------------
// ===========================================================================
// Constructor method(s)
// ---------------------------------------------------------------------------
private SZUUID()
{
super();
}
// ===========================================================================
// Class initialization method(s)
// ---------------------------------------------------------------------------
static
{
try
{
_node = InetAddress.getLocalHost().getAddress().hashCode();
}
catch (Exception anException)
{
SZLog.error( anException );
}
}
// ===========================================================================
// Class method(s)
// ---------------------------------------------------------------------------
public static byte[] uuid()
{
return SZUUID.uuidWithTime( System.currentTimeMillis() );
}
public static byte[] uuidWithTime(long aTime)
{
byte[] anUUID = new byte[ SZUUID.Length ];
int loTime = (int) aTime;
short hiTime = (short) ( aTime >>> 32 );
synchronized ( SZUUID.class )
{
if ( _sequence == Short.MAX_VALUE )
{
_sequence = Short.MIN_VALUE;
}
_sequence += 1;
}
SZByte.writeIntToBytes( anUUID, LoTimeIndex, loTime );
SZByte.writeShortToBytes( anUUID, HiTimeIndex, hiTime );
SZByte.writeIntToBytes( anUUID, UniqueIndex, _unique );
SZByte.writeShortToBytes( anUUID, SequenceIndex, _sequence );
SZByte.writeIntToBytes( anUUID, NodeIndex, _node );
return anUUID;
}
public static long timeWithUUID(byte[] anUUID)
{
if ( ( anUUID != null ) && ( anUUID.length == SZUUID.Length ) )
{
int loTime = SZByte.readIntFromBytes( anUUID, LoTimeIndex
);
short hiTime = SZByte.readShortFromBytes( anUUID,
HiTimeIndex );
long aTime = ( ( long ) hiTime ) << 32 | ( ( ( long )
loTime ) & 0xFFFFFFFFL );
return aTime;
}
throw new IllegalArgumentException( "SZUUID.timeWithUUID: invalid
uuid." );
}
public static int hashCode(byte[] anUUID)
{
if ( ( anUUID != null ) && ( anUUID.length == SZUUID.Length ) )
{
_checksum.reset();
_checksum.update( anUUID, 0, SZUUID.Length );
return (int) _checksum.getValue();
}
throw new IllegalArgumentException( "SZUUID.hashCode: invalid uuid." );
}
public static boolean equals(byte[] anUUID, byte[] anotherUUID)
{
if ( ( anUUID != null ) && ( anUUID.length == SZUUID.Length ) )
{
return Arrays.equals( anUUID, anotherUUID );
}
throw new IllegalArgumentException( "SZUUID.equals: invalid uuid." );
}
// ===========================================================================
// Instance method(s)
// ---------------------------------------------------------------------------
}
