com.mchange.v2.uid.UidUtils Maven / Gradle / Ivy
/*
* Distributed as part of mchange-commons-java 0.2.11
*
* Copyright (C) 2015 Machinery For Change, Inc.
*
* Author: Steve Waldman
*
* This library is free software; you can redistribute it and/or modify
* it under the terms of EITHER:
*
* 1) The GNU Lesser General Public License (LGPL), version 2.1, as
* published by the Free Software Foundation
*
* OR
*
* 2) The Eclipse Public License (EPL), version 1.0
*
* You may choose which license to accept if you wish to redistribute
* or modify this work. You may offer derivatives of this work
* under the license you have chosen, or you may provide the same
* choice of license which you have been offered here.
*
* This software 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.
*
* You should have received copies of both LGPL v2.1 and EPL v1.0
* along with this software; see the files LICENSE-EPL and LICENSE-LGPL.
* If not, the text of these licenses are currently available at
*
* LGPL v2.1: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
* EPL v1.0: http://www.eclipse.org/org/documents/epl-v10.php
*
*/
package com.mchange.v2.uid;
import java.net.InetAddress;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.security.SecureRandom;
import com.mchange.v2.log.MLevel;
import com.mchange.v2.log.MLog;
import com.mchange.v2.log.MLogger;
public final class UidUtils
{
final static MLogger logger = MLog.getLogger( UidUtils.class );
public final static String VM_ID = generateVmId();
//MT: protected by class lock
private static long within_vm_seq_counter = 0;
private static String generateVmId()
{
DataOutputStream dos = null;
DataInputStream dis = null;
try
{
SecureRandom srand = new SecureRandom();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
dos = new DataOutputStream( baos );
try
{
dos.write( InetAddress.getLocalHost().getAddress() );
}
catch (Exception e)
{
if (logger.isLoggable(MLevel.INFO))
logger.log(MLevel.INFO, "Failed to get local InetAddress for VMID. This is unlikely to matter. At all. We'll add some extra randomness", e);
dos.write( srand.nextInt() );
}
dos.writeLong(System.currentTimeMillis());
dos.write( srand.nextInt() );
int remainder = baos.size() % 4; //if it wasn't a 4 byte inet address
if (remainder > 0)
{
int pad = 4 - remainder;
byte[] pad_bytes = new byte[pad];
srand.nextBytes(pad_bytes);
dos.write(pad_bytes);
}
StringBuffer sb = new StringBuffer(32);
byte[] vmid_bytes = baos.toByteArray();
dis = new DataInputStream(new ByteArrayInputStream( vmid_bytes ) );
for (int i = 0, num_ints = vmid_bytes.length / 4; i < num_ints; ++i)
{
int signed = dis.readInt();
long unsigned = ((long) signed) & 0x00000000FFFFFFFFL;
sb.append(Long.toString(unsigned, Character.MAX_RADIX));
}
return sb.toString();
}
catch (IOException e)
{
if (logger.isLoggable(MLevel.WARNING))
logger.log(MLevel.WARNING,
"Bizarro! IOException while reading/writing from ByteArray-based streams? " +
"We're skipping the VMID thing. It almost certainly doesn't matter, " +
"but please report the error.",
e);
return "";
}
finally
{
// this is like total overkill for byte-array based streams,
// but it's a good habit
try { if (dos != null) dos.close(); }
catch ( IOException e )
{ logger.log(MLevel.WARNING, "Huh? Exception close()ing a byte-array bound OutputStream.", e); }
try { if (dis != null) dis.close(); }
catch ( IOException e )
{ logger.log(MLevel.WARNING, "Huh? Exception close()ing a byte-array bound IntputStream.", e); }
}
}
private synchronized static long nextWithinVmSeq()
{ return ++within_vm_seq_counter; }
public static String allocateWithinVmSequential()
{ return VM_ID + "#" + nextWithinVmSeq(); }
private UidUtils()
{}
}