com.groupon.uuid.UUID Maven / Gradle / Ivy
/*
Copyright (c) 2013, Groupon, Inc.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
Neither the name of GROUPON nor the names of its contributors may be
used to endorse or promote products derived from this software without
specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.groupon.uuid;
import java.lang.management.ManagementFactory;
import java.net.NetworkInterface;
import java.security.MessageDigest;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;
import java.util.Random;
import java.util.TimeZone;
import java.util.concurrent.atomic.AtomicInteger;
/**
* See README.md for more information
*/
public final class UUID {
public static final int PID = processId();
public static final byte[] MAC = macAddress();
private static final int MAX_PID = 65536;
private static final int INCREMENT = 198491317;
private static final char VERSION = 'b';
private static final int VERSION_DEC = mapToByte(VERSION, '0');
private static final AtomicInteger COUNTER = new AtomicInteger(new Random(System.nanoTime()).nextInt());
private static final char[] HEX =
{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
private static boolean sequential = false;
private final byte[] content;
/**
* Constructor that generates a new UUID using the current process id, MAC address, and timestamp
*/
public UUID() {
long time = new Date().getTime();
content = new byte[16];
if (!sequential) {
// atomically add a large prime number to the count and get the previous value
int count = COUNTER.addAndGet(INCREMENT);
// switch the order of the count in 4 bit segments and place into content
content[0] = (byte) (((count & 0xF) << 4) | ((count & 0xF0) >> 4));
content[1] = (byte) (((count & 0xF00) >> 4) | ((count & 0xF000) >> 12));
content[2] = (byte) (((count & 0xF0000) >> 12) | ((count & 0xF00000) >> 20));
content[3] = (byte) (((count & 0xF000000) >> 20) | ((count & 0xF0000000) >> 28));
}
else {
int count = COUNTER.addAndGet(1);
// get the count in order and place into content
content[0] = (byte) (count >> 24);
content[1] = (byte) (count >> 16);
content[2] = (byte) (count >> 8);
content[3] = (byte) (count);
}
// copy pid to content
content[4] = (byte) (PID >> 8);
content[5] = (byte) (PID);
// place UUID version (hex 'b') in first four bits and piece of mac address in
// the second four bits
content[6] = (byte) (VERSION_DEC | (0xF & MAC[2]));
// copy rest of mac address into content
content[7] = MAC[3];
content[8] = MAC[4];
content[9] = MAC[5];
// copy timestamp into content
content[10] = (byte) (time >> 40);
content[11] = (byte) (time >> 32);
content[12] = (byte) (time >> 24);
content[13] = (byte) (time >> 16);
content[14] = (byte) (time >> 8);
content[15] = (byte) (time);
}
/**
* Constructor that takes a byte array as this UUID's content
* @param bytes UUID content
*/
public UUID(byte[] bytes) {
if (bytes.length != 16)
throw new RuntimeException("Attempted to parse malformed UUID: " + Arrays.toString(bytes));
content = Arrays.copyOf(bytes, 16);
}
public UUID(String id) {
id = id.trim();
if (id.length() != 36)
throw new RuntimeException("Attempted to parse malformed UUID: " + id);
content = new byte[16];
char[] chars = id.toCharArray();
content[0] = mapToByte(chars[0], chars[1]);
content[1] = mapToByte(chars[2], chars[3]);
content[2] = mapToByte(chars[4], chars[5]);
content[3] = mapToByte(chars[6], chars[7]);
content[4] = mapToByte(chars[9], chars[10]);
content[5] = mapToByte(chars[11], chars[12]);
content[6] = mapToByte(chars[14], chars[15]);
content[7] = mapToByte(chars[16], chars[17]);
content[8] = mapToByte(chars[19], chars[20]);
content[9] = mapToByte(chars[21], chars[22]);
content[10] = mapToByte(chars[24], chars[25]);
content[11] = mapToByte(chars[26], chars[27]);
content[12] = mapToByte(chars[28], chars[29]);
content[13] = mapToByte(chars[30], chars[31]);
content[14] = mapToByte(chars[32], chars[33]);
content[15] = mapToByte(chars[34], chars[35]);
}
/**
* Toggle uuid generator into sequential mode, so the random segment is in order and increases by one
*/
public static void useSequentialIds() {
if (!sequential) {
// get string that changes every 10 minutes
TimeZone tz = TimeZone.getTimeZone("UTC");
DateFormat df = new SimpleDateFormat("yyyyMMddHHmm");
df.setTimeZone(tz);
String date = df.format(new Date()).substring(0, 11);
// run an md5 hash of the string, no reason this needs to be secure
byte[] digest;
try {
MessageDigest md = MessageDigest.getInstance("MD5");
digest = md.digest(date.getBytes("UTF-8"));
}
catch (Exception e) {
throw new RuntimeException("Could not create hash of date for the sequential counter", e);
}
// create integer from first 4 bytes of md5 hash
int x;
x = ((int)digest[0] & 0xFF);
x |= ((int)digest[1] & 0xFF) << 8;
x |= ((int)digest[2] & 0xFF) << 16;
x |= ((int)digest[3] & 0xFF) << 24;
COUNTER.set(x);
}
sequential = true;
}
/**
* Toggle uuid generator into variable mode, so the random segment is in reverse order and
* increases by a large increment. This is the default mode.
*/
public static void useVariableIds() {
sequential = false;
}
/**
* map hex character to 4 bit number
* @param x hex character
* @return four bit number representing offset from '0'
*/
private static int intValue(char x) {
if (x >= '0' && x <= '9')
return x - '0';
if (x >= 'a' && x <= 'f')
return x - 'a' + 10;
if (x >= 'A' && x <= 'F')
return x - 'A' + 10;
throw new RuntimeException("Error parsing UUID at character: " + x);
}
/**
* map two hex characters to 4 bit numbers and combine them
* @param a hex character 1
* @param b hex character 2
* @return single byte value of combined characters
*/
private static byte mapToByte(char a, char b) {
int ai = intValue(a);
int bi = intValue(b);
return (byte) ((ai << 4) | bi);
}
/**
* copy the content of this UUID, so that it can't be changed, and return it
* @return raw byte array of UUID
*/
public byte[] getBytes() {
return Arrays.copyOf(content, 16);
}
@Override
public String toString() {
char[] id = new char[36];
// split each byte into 4 bit numbers and map to hex characters
id[0] = HEX[(content[0] & 0xF0) >> 4];
id[1] = HEX[(content[0] & 0x0F)];
id[2] = HEX[(content[1] & 0xF0) >> 4];
id[3] = HEX[(content[1] & 0x0F)];
id[4] = HEX[(content[2] & 0xF0) >> 4];
id[5] = HEX[(content[2] & 0x0F)];
id[6] = HEX[(content[3] & 0xF0) >> 4];
id[7] = HEX[(content[3] & 0x0F)];
id[8] = '-';
id[9] = HEX[(content[4] & 0xF0) >> 4];
id[10] = HEX[(content[4] & 0x0F)];
id[11] = HEX[(content[5] & 0xF0) >> 4];
id[12] = HEX[(content[5] & 0x0F)];
id[13] = '-';
id[14] = HEX[(content[6] & 0xF0) >> 4];
id[15] = HEX[(content[6] & 0x0F)];
id[16] = HEX[(content[7] & 0xF0) >> 4];
id[17] = HEX[(content[7] & 0x0F)];
id[18] = '-';
id[19] = HEX[(content[8] & 0xF0) >> 4];
id[20] = HEX[(content[8] & 0x0F)];
id[21] = HEX[(content[9] & 0xF0) >> 4];
id[22] = HEX[(content[9] & 0x0F)];
id[23] = '-';
id[24] = HEX[(content[10] & 0xF0) >> 4];
id[25] = HEX[(content[10] & 0x0F)];
id[26] = HEX[(content[11] & 0xF0) >> 4];
id[27] = HEX[(content[11] & 0x0F)];
id[28] = HEX[(content[12] & 0xF0) >> 4];
id[29] = HEX[(content[12] & 0x0F)];
id[30] = HEX[(content[13] & 0xF0) >> 4];
id[31] = HEX[(content[13] & 0x0F)];
id[32] = HEX[(content[14] & 0xF0) >> 4];
id[33] = HEX[(content[14] & 0x0F)];
id[34] = HEX[(content[15] & 0xF0) >> 4];
id[35] = HEX[(content[15] & 0x0F)];
return new String(id);
}
/**
* extract version field as a hex char from raw UUID bytes
* @return version char
*/
public char getVersion() {
return HEX[(content[6] & 0xF0) >> 4];
}
/**
* extract process id from raw UUID bytes and return as int
* @return id of process that generated the UUID, or -1 for unrecognized format
*/
public int getProcessId() {
if (getVersion() != VERSION)
return -1;
return ((content[4] & 0xFF) << 8) | (content[5] & 0xFF);
}
/**
* extract timestamp from raw UUID bytes and return as int
* @return millisecond UTC timestamp from generation of the UUID, or null for unrecognized format
*/
public Date getTimestamp() {
if (getVersion() != VERSION)
return null;
long time;
time = ((long)content[10] & 0xFF) << 40;
time |= ((long)content[11] & 0xFF) << 32;
time |= ((long)content[12] & 0xFF) << 24;
time |= ((long)content[13] & 0xFF) << 16;
time |= ((long)content[14] & 0xFF) << 8;
time |= ((long)content[15] & 0xFF);
return new Date(time);
}
/**
* extract MAC address fragment from raw UUID bytes, setting missing values to 0,
* thus the first 2 and a half bytes will be 0, followed by 3 and a half bytes
* of the active MAC address when the UUID was generated
* @return byte array of UUID fragment, or null for unrecognized format
*/
public byte[] getMacFragment() {
if (getVersion() != 'b')
return null;
byte[] x = new byte[6];
x[0] = 0;
x[1] = 0;
x[2] = (byte) (content[6] & 0xF);
x[3] = content[7];
x[4] = content[8];
x[5] = content[9];
return x;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
UUID that = (UUID) o;
if (this.content.length != that.content.length)
return false;
for (int i = 0; i < this.content.length; i++)
if (this.content[i] != that.content[i])
return false;
return true;
}
@Override
public int hashCode() {
return Arrays.hashCode(content);
}
private static byte[] macAddress() {
try {
byte[] mac = NetworkInterface.getNetworkInterfaces().nextElement().getHardwareAddress();
// if the machine is not connected to a network it has no active MAC address
if (mac == null)
mac = new byte[] {0, 0, 0, 0, 0, 0};
return mac;
} catch (Exception e) {
throw new RuntimeException("Could not get MAC address");
}
}
// pulled from http://stackoverflow.com/questions/35842/how-can-a-java-program-get-its-own-process-id
private static int processId() {
// Note: may fail in some JVM implementations
// something like '@', at least in SUN / Oracle JVMs
final String jvmName = ManagementFactory.getRuntimeMXBean().getName();
final int index = jvmName.indexOf('@');
if (index < 1)
throw new RuntimeException("Could not get PID");
try {
return Integer.parseInt(jvmName.substring(0, index)) % MAX_PID;
} catch (NumberFormatException e) {
throw new RuntimeException("Could not get PID");
}
}
}
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