/*
* Copyright (c) 2013, OpenCloudDB/MyCAT and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software;Designed and Developed mainly by many Chinese
* opensource volunteers. you can redistribute it and/or modify it under the
* terms of the GNU General Public License version 2 only, as published by the
* Free Software Foundation.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Any questions about this component can be directed to it's project Web address
* https://code.google.com/p/opencloudb/.
*
*/
package org.opencloudb.util;
/**
* @author mycat
*/
public class RandomUtil {
private static final byte[] bytes = { '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', 'q', 'w', 'e', 'r', 't',
'y', 'u', 'i', 'o', 'p', 'a', 's', 'd', 'f', 'g', 'h', 'j', 'k', 'l', 'z', 'x', 'c', 'v', 'b', 'n', 'm',
'Q', 'W', 'E', 'R', 'T', 'Y', 'U', 'I', 'O', 'P', 'A', 'S', 'D', 'F', 'G', 'H', 'J', 'K', 'L', 'Z', 'X',
'C', 'V', 'B', 'N', 'M' };
private static final long multiplier = 0x5DEECE66DL;
private static final long addend = 0xBL;
private static final long mask = (1L << 48) - 1;
private static final long integerMask = (1L << 33) - 1;
private static final long seedUniquifier = 8682522807148012L;
private static long seed;
static {
long s = seedUniquifier + System.nanoTime();
s = (s ^ multiplier) & mask;
seed = s;
}
public static final byte[] randomBytes(int size) {
byte[] bb = bytes;
byte[] ab = new byte[size];
for (int i = 0; i < size; i++) {
ab[i] = randomByte(bb);
}
return ab;
}
private static byte randomByte(byte[] b) {
int ran = (int) ((next() & integerMask) >>> 16);
return b[ran % b.length];
}
private static long next() {
long oldSeed = seed;
long nextSeed = 0L;
do {
nextSeed = (oldSeed * multiplier + addend) & mask;
} while (oldSeed == nextSeed);
seed = nextSeed;
return nextSeed;
}
}