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package io.geewit.utils.uuid;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
/**
* 来自 JDK {@link java.util.UUID} 去掉 ‘-’
*
* @author geewit
* @since 2015-05-18
*/
@SuppressWarnings({"unused"})
public class UUID implements java.io.Serializable, Comparable {
private static final long serialVersionUID = 1L;
/*
* The most significant 64 bits of this UUID.
*
* @serial
*/
private final long mostSigBits;
/*
* The least significant 64 bits of this UUID.
*
* @serial
*/
private final long leastSigBits;
/*
* The random number generator used by this class to create random
* based UUIDs. In a holder class to defer initialization until needed.
*/
private static class Holder {
static final SecureRandom numberGenerator = new SecureRandom();
}
// Constructors and Factories
/*
* Private constructor which uses a byte array to construct the new UUID.
*/
private UUID(byte[] data) {
long msb = 0;
long lsb = 0;
assert data.length == 16 : "data must be 16 bytes in length";
for (int i = 0; i < 8; i++) {
msb = (msb << 8) | (data[i] & 0xff);
}
for (int i = 8; i < 16; i++) {
lsb = (lsb << 8) | (data[i] & 0xff);
}
this.mostSigBits = msb;
this.leastSigBits = lsb;
}
/**
* Constructs a new {@code UUID} using the specified data. {@code
* mostSigBits} is used for the most significant 64 bits of the {@code
* UUID} and {@code leastSigBits} becomes the least significant 64 bits of
* the {@code UUID}.
*
* @param mostSigBits The most significant bits of the {@code UUID}
* @param leastSigBits The least significant bits of the {@code UUID}
*/
public UUID(long mostSigBits, long leastSigBits) {
this.mostSigBits = mostSigBits;
this.leastSigBits = leastSigBits;
}
/**
* Static factory to retrieve a type 4 (pseudo randomly generated) UUID.
*
* The {@code UUID} is generated using a cryptographically strong pseudo
* random number generator.
*
* @return A randomly generated {@code UUID}
*/
public static UUID randomUUID() {
SecureRandom ng = Holder.numberGenerator;
byte[] randomBytes = new byte[16];
ng.nextBytes(randomBytes);
randomBytes[6] &= 0x0f; /* clear version */
randomBytes[6] |= 0x40; /* set to version 4 */
randomBytes[8] &= 0x3f; /* clear variant */
randomBytes[8] |= 0x80; /* set to IETF variant */
return new UUID(randomBytes);
}
/**
* Static factory to retrieve a type 3 (name based) {@code UUID} based on
* the specified byte array.
*
* @param name A byte array to be used to construct a {@code UUID}
* @return A {@code UUID} generated from the specified array
*/
public static UUID nameUUIDFromBytes(byte[] name) {
MessageDigest md;
try {
md = MessageDigest.getInstance("MD5");
} catch (NoSuchAlgorithmException nsae) {
throw new InternalError("MD5 not supported", nsae);
}
byte[] md5Bytes = md.digest(name);
md5Bytes[6] &= 0x0f; /* clear version */
md5Bytes[6] |= 0x30; /* set to version 3 */
md5Bytes[8] &= 0x3f; /* clear variant */
md5Bytes[8] |= 0x80; /* set to IETF variant */
return new UUID(md5Bytes);
}
/**
* Creates a {@code UUID} from the string standard representation as
* described in the {@link #toString} method.
*
* @param name A string that specifies a {@code UUID}
* @return A {@code UUID} with the specified value
* @throws IllegalArgumentException If name does not conform to the string representation as
* described in {@link #toString}
*/
public static UUID fromString(String name) {
if(name.length() != 32) {
throw new IllegalArgumentException("Invalid UUID string: " + name);
}
String[] components = new String[5];
for (int i = 0; i < 5; i++) {
switch (i) {
case 0: {
components[i] = "0x" + name.substring(0, 8);
break;
}
case 1: {
components[i] = "0x" + name.substring(8, 12);
break;
}
case 2: {
components[i] = "0x" + name.substring(12, 16);
break;
}
case 3: {
components[i] = "0x" + name.substring(16, 20);
break;
}
case 4: {
components[i] = "0x" + name.substring(20, 32);
break;
}
}
}
long mostSigBits = Long.decode(components[0]);
mostSigBits <<= 16;
mostSigBits |= Long.decode(components[1]);
mostSigBits <<= 16;
mostSigBits |= Long.decode(components[2]);
long leastSigBits = Long.decode(components[3]);
leastSigBits <<= 48;
leastSigBits |= Long.decode(components[4]);
return new UUID(mostSigBits, leastSigBits);
}
// Field Accessor Methods
/**
* Returns the least significant 64 bits of this UUID's 128 bit value.
*
* @return The least significant 64 bits of this UUID's 128 bit value
*/
public long getLeastSignificantBits() {
return leastSigBits;
}
/**
* Returns the most significant 64 bits of this UUID's 128 bit value.
*
* @return The most significant 64 bits of this UUID's 128 bit value
*/
public long getMostSignificantBits() {
return mostSigBits;
}
/**
* The version number associated with this {@code UUID}. The version
* number describes how this {@code UUID} was generated.
*
* The version number has the following meaning:
*
* - 1 Time-based UUID
*
- 2 DCE security UUID
*
- 3 Name-based UUID
*
- 4 Randomly generated UUID
*
*
* @return The version number of this {@code UUID}
*/
public int version() {
// Version is bits masked by 0x000000000000F000 in MS long
return (int) ((mostSigBits >> 12) & 0x0f);
}
/**
* The variant number associated with this {@code UUID}. The variant
* number describes the layout of the {@code UUID}.
*
* The variant number has the following meaning:
*
* - 0 Reserved for NCS backward compatibility
*
- 2 IETF RFC 4122
* (Leach-Salz), used by this class
*
- 6 Reserved, Microsoft Corporation backward compatibility
*
- 7 Reserved for future definition
*
*
* @return The variant number of this {@code UUID}
*/
public int variant() {
// This field is composed of a varying number of bits.
// 0 - - Reserved for NCS backward compatibility
// 1 0 - The IETF aka Leach-Salz variant (used by this class)
// 1 1 0 Reserved, Microsoft backward compatibility
// 1 1 1 Reserved for future definition.
return (int) ((leastSigBits >>> (64 - (leastSigBits >>> 62)))
& (leastSigBits >> 63));
}
/**
* The timestamp value associated with this UUID.
*
* The 60 bit timestamp value is constructed from the time_low,
* time_mid, and time_hi fields of this {@code UUID}. The resulting
* timestamp is measured in 100-nanosecond units since midnight,
* October 15, 1582 UTC.
*
*
The timestamp value is only meaningful in a time-based UUID, which
* has version type 1. If this {@code UUID} is not a time-based UUID then
* this method throws UnsupportedOperationException.
*
* @return The timestamp of this {@code UUID}.
* @throws UnsupportedOperationException If this UUID is not a version 1 UUID
*/
public long timestamp() {
if (version() != 1) {
throw new UnsupportedOperationException("Not a time-based UUID");
}
return (mostSigBits & 0x0FFFL) << 48
| ((mostSigBits >> 16) & 0x0FFFFL) << 32
| mostSigBits >>> 32;
}
/**
* The clock sequence value associated with this UUID.
*
*
The 14 bit clock sequence value is constructed from the clock
* sequence field of this UUID. The clock sequence field is used to
* guarantee temporal uniqueness in a time-based UUID.
*
*
The {@code clockSequence} value is only meaningful in a time-based
* UUID, which has version type 1. If this UUID is not a time-based UUID
* then this method throws UnsupportedOperationException.
*
* @return The clock sequence of this {@code UUID}
* @throws UnsupportedOperationException If this UUID is not a version 1 UUID
*/
public int clockSequence() {
if (version() != 1) {
throw new UnsupportedOperationException("Not a time-based UUID");
}
return (int) ((leastSigBits & 0x3FFF000000000000L) >>> 48);
}
/**
* The node value associated with this UUID.
*
*
The 48 bit node value is constructed from the node field of this
* UUID. This field is intended to hold the IEEE 802 address of the machine
* that generated this UUID to guarantee spatial uniqueness.
*
*
The node value is only meaningful in a time-based UUID, which has
* version type 1. If this UUID is not a time-based UUID then this method
* throws UnsupportedOperationException.
*
* @return The node value of this {@code UUID}
* @throws UnsupportedOperationException If this UUID is not a version 1 UUID
*/
public long node() {
if (version() != 1) {
throw new UnsupportedOperationException("Not a time-based UUID");
}
return leastSigBits & 0x0000FFFFFFFFFFFFL;
}
// Object Inherited Methods
/**
* Returns a {@code String} object representing this {@code UUID}.
*
*
The UUID string representation is as described by this BNF:
*
* {@code
* UUID = "-" "-"
* "-"
* "-"
*
* time_low = 4*
* time_mid = 2*
* time_high_and_version = 2*
* variant_and_sequence = 2*
* node = 6*
* hexOctet =
* hexDigit =
* "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
* | "a" | "b" | "c" | "d" | "e" | "f"
* | "A" | "B" | "C" | "D" | "E" | "F"
* }
*
* @return A string representation of this {@code UUID}
*/
public String toString() {
return (digits(mostSigBits >> 32, 8) +
digits(mostSigBits >> 16, 4) +
digits(mostSigBits, 4) +
digits(leastSigBits >> 48, 4) +
digits(leastSigBits, 12));
}
/**
* Returns val represented by the specified number of hex digits.
*/
private static String digits(long val, int digits) {
long hi = 1L << (digits * 4);
return Long.toHexString(hi | (val & (hi - 1))).substring(1);
}
/**
* Returns a hash code for this {@code UUID}.
*
* @return A hash code value for this {@code UUID}
*/
public int hashCode() {
long hilo = mostSigBits ^ leastSigBits;
return ((int) (hilo >> 32)) ^ (int) hilo;
}
/**
* Compares this object to the specified object. The result is {@code
* true} if and only if the argument is not {@code null}, is a {@code UUID}
* object, has the same variant, and contains the same value, bit for bit,
* as this {@code UUID}.
*
* @param obj The object to be compared
* @return {@code true} if the objects are the same; {@code false}
* otherwise
*/
public boolean equals(Object obj) {
if ((null == obj) || (obj.getClass() != UUID.class)) {
return false;
}
UUID id = (UUID) obj;
return mostSigBits == id.mostSigBits &&
leastSigBits == id.leastSigBits;
}
// Comparison Operations
/**
* Compares this UUID with the specified UUID.
*
* The first of two UUIDs is greater than the second if the most
* significant field in which the UUIDs differ is greater for the first
* UUID.
*
* @param val {@code UUID} to which this {@code UUID} is to be compared
* @return -1, 0 or 1 as this {@code UUID} is less than, equal to, or
* greater than {@code val}
*/
public int compareTo(UUID val) {
// The ordering is intentionally set up so that the UUIDs
// can simply be numerically compared as two numbers
return Long.compare(this.leastSigBits, val.leastSigBits);
}
}