/*
*
* * Copyright 2014 Orient Technologies LTD (info(at)orientechnologies.com)
* *
* * Licensed under the Apache License, Version 2.0 (the "License");
* * you may not use this file except in compliance with the License.
* * You may obtain a copy of the License at
* *
* * http://www.apache.org/licenses/LICENSE-2.0
* *
* * Unless required by applicable law or agreed to in writing, software
* * distributed under the License is distributed on an "AS IS" BASIS,
* * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* * See the License for the specific language governing permissions and
* * limitations under the License.
* *
* * For more information: http://www.orientechnologies.com
*
*/
package com.orientechnologies.orient.core.storage.cache;
import java.security.SecureRandom;
public class OSnowFlakeIdGen implements OWriteCacheIdGen {
private long lastTs;
private final SecureRandom rnd;
private int sequenceCounter = 1;
private byte[] rndBytes = new byte[2];
public OSnowFlakeIdGen() {
rnd = new SecureRandom();
}
@Override
public synchronized int nextId() {
int id;
if (sequenceCounter < 15)
sequenceCounter++;
else
sequenceCounter = 1;
lastTs = System.currentTimeMillis();
rnd.nextBytes(rndBytes);
id = composeId();
// This id is used for generate fileId that in case of ridBag cannot be negative.
if (id < 0)
id *= -1;
return id;
}
private int composeId() {
return ((rndBytes[0] & 0xFF) << 24) | ((rndBytes[1] & 0xFF) << 16) | (((int) (lastTs & 0xFFF)) << 4) | (sequenceCounter & 0xF);
}
}