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	/*
	* Copyright (c) 2003, 2014, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; 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. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* 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.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.util;

	import java.security.*;

	import jdk.internal.misc.JavaLangAccess;
	import jdk.internal.misc.SharedSecrets;

	/**
	* A class that represents an immutable universally unique identifier (UUID).
	* A UUID represents a 128-bit value.
	*
	* <p> There exist different variants of these global identifiers. The methods
	* of this class are for manipulating the Leach-Salz variant, although the
	* constructors allow the creation of any variant of UUID (described below).
	*
	* <p> The layout of a variant 2 (Leach-Salz) UUID is as follows:
	*
	* The most significant long consists of the following unsigned fields:
	* <pre>
	* 0xFFFFFFFF00000000 time_low
	* 0x00000000FFFF0000 time_mid
	* 0x000000000000F000 version
	* 0x0000000000000FFF time_hi
	* </pre>
	* The least significant long consists of the following unsigned fields:
	* <pre>
	* 0xC000000000000000 variant
	* 0x3FFF000000000000 clock_seq
	* 0x0000FFFFFFFFFFFF node
	* </pre>
	*
	* <p> The variant field contains a value which identifies the layout of the
	* {@code UUID}. The bit layout described above is valid only for a {@code
	* UUID} with a variant value of 2, which indicates the Leach-Salz variant.
	*
	* <p> The version field holds a value that describes the type of this {@code
	* UUID}. There are four different basic types of UUIDs: time-based, DCE
	* security, name-based, and randomly generated UUIDs. These types have a
	* version value of 1, 2, 3 and 4, respectively.
	*
	* <p> For more information including algorithms used to create {@code UUID}s,
	* see <a href="http://www.ietf.org/rfc/rfc4122.txt"> <i>RFC 4122: A
	* Universally Unique IDentifier (UUID) URN Namespace</i></a>, section 4.2
	* "Algorithms for Creating a Time-Based UUID".
	*
	* @since 1.5
	*/
	public final class UUID implements java.io.Serializable, Comparable<UUID> {

	/**
	* Explicit serialVersionUID for interoperability.
	*/
	private static final long serialVersionUID = -4856846361193249489L;

	/*
	* 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;

	private static final JavaLangAccess jla = SharedSecrets.getJavaLangAccess();

	/*
	* 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) {
	int len = name.length();
	if (len > 36) {
	throw new IllegalArgumentException("UUID string too large");
	}

	int dash1 = name.indexOf('-', 0);
	int dash2 = name.indexOf('-', dash1 + 1);
	int dash3 = name.indexOf('-', dash2 + 1);
	int dash4 = name.indexOf('-', dash3 + 1);
	int dash5 = name.indexOf('-', dash4 + 1);

	// For any valid input, dash1 through dash4 will be positive and dash5
	// negative, but it's enough to check dash4 and dash5:
	// - if dash1 is -1, dash4 will be -1
	// - if dash1 is positive but dash2 is -1, dash4 will be -1
	// - if dash1 and dash2 is positive, dash3 will be -1, dash4 will be
	// positive, but so will dash5
	if (dash4 < 0 \|\| dash5 >= 0) {
	throw new IllegalArgumentException("Invalid UUID string: " + name);
	}

	long mostSigBits = Long.parseLong(name, 0, dash1, 16) & 0xffffffffL;
	mostSigBits <<= 16;
	mostSigBits \|= Long.parseLong(name, dash1 + 1, dash2, 16) & 0xffffL;
	mostSigBits <<= 16;
	mostSigBits \|= Long.parseLong(name, dash2 + 1, dash3, 16) & 0xffffL;
	long leastSigBits = Long.parseLong(name, dash3 + 1, dash4, 16) & 0xffffL;
	leastSigBits <<= 48;
	leastSigBits \|= Long.parseLong(name, dash4 + 1, len, 16) & 0xffffffffffffL;

	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:
	* <ul>
	* <li>1 Time-based UUID
	* <li>2 DCE security UUID
	* <li>3 Name-based UUID
	* <li>4 Randomly generated UUID
	* </ul>
	*
	* @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:
	* <ul>
	* <li>0 Reserved for NCS backward compatibility
	* <li>2 <a href="http://www.ietf.org/rfc/rfc4122.txt">IETF RFC 4122</a>
	* (Leach-Salz), used by this class
	* <li>6 Reserved, Microsoft Corporation backward compatibility
	* <li>7 Reserved for future definition
	* </ul>
	*
	* @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.
	*
	* <p> 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.
	*
	* <p> 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.
	*
	* @throws UnsupportedOperationException
	* If this UUID is not a version 1 UUID
	* @return The timestamp of this {@code 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.
	*
	* <p> 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.
	*
	* <p> 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.
	*
	* <p> 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.
	*
	* <p> 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}.
	*
	* <p> The UUID string representation is as described by this BNF:
	* <blockquote><pre>
	* {@code
	* UUID = <time_low> "-" <time_mid> "-"
	* <time_high_and_version> "-"
	* <variant_and_sequence> "-"
	* <node>
	* time_low = 4*<hexOctet>
	* time_mid = 2*<hexOctet>
	* time_high_and_version = 2*<hexOctet>
	* variant_and_sequence = 2*<hexOctet>
	* node = 6*<hexOctet>
	* hexOctet = <hexDigit><hexDigit>
	* hexDigit =
	* "0" \| "1" \| "2" \| "3" \| "4" \| "5" \| "6" \| "7" \| "8" \| "9"
	* \| "a" \| "b" \| "c" \| "d" \| "e" \| "f"
	* \| "A" \| "B" \| "C" \| "D" \| "E" \| "F"
	* }</pre></blockquote>
	*
	* @return A string representation of this {@code UUID}
	*/
	public String toString() {
	return jla.fastUUID(leastSigBits, mostSigBits);
	}

	/**
	* 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.
	*
	* <p> 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 (this.mostSigBits < val.mostSigBits ? -1 :
	(this.mostSigBits > val.mostSigBits ? 1 :
	(this.leastSigBits < val.leastSigBits ? -1 :
	(this.leastSigBits > val.leastSigBits ? 1 :
	0))));
	}
	}

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