- /*
- * @(#)UUID.java 1.14 04/07/12
- *
- * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
- * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
- */
-
- package java.util;
-
- import java.security.*;
- import java.io.IOException;
- import java.io.UnsupportedEncodingException;
-
- /**
- *
- * 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 <tt>UUID</tt>. The bit layout described above is valid only for
- * a <tt>UUID</tt> 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
- * <tt>UUID</tt>. 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 <tt>UUID</tt>s,
- * see the Internet-Draft <a href="http://www.ietf.org/internet-drafts/draft-mealling-uuid-urn-03.txt">UUIDs and GUIDs</a>
- * or the standards body definition at
- * <a href="http://www.iso.ch/cate/d2229.html">ISO/IEC 11578:1996</a>.
- *
- * @version 1.14, 07/12/04
- * @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;
-
- /*
- * The version number associated with this UUID. Computed on demand.
- */
- private transient int version = -1;
-
- /*
- * The variant number associated with this UUID. Computed on demand.
- */
- private transient int variant = -1;
-
- /*
- * The timestamp associated with this UUID. Computed on demand.
- */
- private transient volatile long timestamp = -1;
-
- /*
- * The clock sequence associated with this UUID. Computed on demand.
- */
- private transient int sequence = -1;
-
- /*
- * The node number associated with this UUID. Computed on demand.
- */
- private transient long node = -1;
-
- /*
- * The hashcode of this UUID. Computed on demand.
- */
- private transient int hashCode = -1;
-
- /*
- * The random number generator used by this class to create random
- * based UUIDs.
- */
- private static volatile SecureRandom numberGenerator = null;
-
- // 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;
- 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 <tt>UUID</tt> using the specified data.
- * <tt>mostSigBits</tt> is used for the most significant 64 bits
- * of the <tt>UUID</tt> and <tt>leastSigBits</tt> becomes the
- * least significant 64 bits of the <tt>UUID</tt>.
- *
- * @param mostSigBits
- * @param leastSigBits
- */
- 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</code> is generated using a cryptographically strong
- * pseudo random number generator.
- *
- * @return a randomly generated <tt>UUID</tt>.
- */
- public static UUID randomUUID() {
- SecureRandom ng = numberGenerator;
- if (ng == null) {
- numberGenerator = ng = new SecureRandom();
- }
-
- 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 */
- UUID result = new UUID(randomBytes);
- return new UUID(randomBytes);
- }
-
- /**
- * Static factory to retrieve a type 3 (name based) <tt>UUID</tt> based on
- * the specified byte array.
- *
- * @param name a byte array to be used to construct a <tt>UUID</tt>.
- * @return a <tt>UUID</tt> 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");
- }
- 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 <tt>UUID</tt> from the string standard representation as
- * described in the {@link #toString} method.
- *
- * @param name a string that specifies a <tt>UUID</tt>.
- * @return a <tt>UUID</tt> 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) {
- String[] components = name.split("-");
- if (components.length != 5)
- throw new IllegalArgumentException("Invalid UUID string: "+name);
- for (int i=0; i<5; i++)
- components[i] = "0x"+components[i];
-
- long mostSigBits = Long.decode(components[0]).longValue();
- mostSigBits <<= 16;
- mostSigBits |= Long.decode(components[1]).longValue();
- mostSigBits <<= 16;
- mostSigBits |= Long.decode(components[2]).longValue();
-
- long leastSigBits = Long.decode(components[3]).longValue();
- leastSigBits <<= 48;
- leastSigBits |= Long.decode(components[4]).longValue();
-
- 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 <tt>UUID</tt>. The version
- * number describes how this <tt>UUID</tt> was generated.
- *
- * The version number has the following meaning:<p>
- * <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 <tt>UUID</tt>.
- */
- public int version() {
- if (version < 0) {
- // Version is bits masked by 0x000000000000F000 in MS long
- version = (int)((mostSigBits >> 12) & 0x0f);
- }
- return version;
- }
-
- /**
- * The variant number associated with this <tt>UUID</tt>. The variant
- * number describes the layout of the <tt>UUID</tt>.
- *
- * The variant number has the following meaning:<p>
- * <ul>
- * <li>0 Reserved for NCS backward compatibility
- * <li>2 The Leach-Salz variant (used by this class)
- * <li>6 Reserved, Microsoft Corporation backward compatibility
- * <li>7 Reserved for future definition
- * </ul>
- *
- * @return the variant number of this <tt>UUID</tt>.
- */
- public int variant() {
- if (variant < 0) {
- // This field is composed of a varying number of bits
- if ((leastSigBits >>> 63) == 0) {
- variant = 0;
- } else if ((leastSigBits >>> 62) == 2) {
- variant = 2;
- } else {
- variant = (int)(leastSigBits >>> 61);
- }
- }
- return variant;
- }
-
- /**
- * 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 <tt>UUID</tt>. 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 <tt>UUID</tt> is not a time-based UUID then
- * this method throws UnsupportedOperationException.
- *
- * @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");
- }
- long result = timestamp;
- if (result < 0) {
- result = (mostSigBits & 0x0000000000000FFFL) << 48;
- result |= ((mostSigBits >> 16) & 0xFFFFL) << 32;
- result |= mostSigBits >>> 32;
- timestamp = result;
- }
- return result;
- }
-
- /**
- * 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 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 <tt>UUID</tt>.
- * @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");
- }
- if (sequence < 0) {
- sequence = (int)((leastSigBits & 0x3FFF000000000000L) >>> 48);
- }
- return sequence;
- }
-
- /**
- * 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 <tt>UUID</tt>.
- * @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");
- }
- if (node < 0) {
- node = leastSigBits & 0x0000FFFFFFFFFFFFL;
- }
- return node;
- }
-
- // Object Inherited Methods
-
- /**
- * Returns a <code>String</code> object representing this
- * <code>UUID</code>.
- *
- * <p>The UUID string representation is as described by this BNF :
- * <pre>
- * 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>
- *
- * @return a string representation of this <tt>UUID</tt>.
- */
- 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</code>.
- *
- * @return a hash code value for this <tt>UUID</tt>.
- */
- public int hashCode() {
- if (hashCode == -1) {
- hashCode = (int)((mostSigBits >> 32) ^
- mostSigBits ^
- (leastSigBits >> 32) ^
- leastSigBits);
- }
- return hashCode;
- }
-
- /**
- * Compares this object to the specified object. The result is
- * <tt>true</tt> if and only if the argument is not
- * <tt>null</tt>, is a <tt>UUID</tt> object, has the same variant,
- * and contains the same value, bit for bit, as this <tt>UUID</tt>.
- *
- * @param obj the object to compare with.
- * @return <code>true</code> if the objects are the same;
- * <code>false</code> otherwise.
- */
- public boolean equals(Object obj) {
- if (!(obj instanceof UUID))
- return false;
- if (((UUID)obj).variant() != this.variant())
- 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 follows the second if the most significant
- * field in which the UUIDs differ is greater for the first UUID.
- *
- * @param val <tt>UUID</tt> to which this <tt>UUID</tt> is to be compared.
- * @return -1, 0 or 1 as this <tt>UUID</tt> is less than, equal
- * to, or greater than <tt>val</tt>.
- */
- 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))));
- }
-
- /**
- * Reconstitute the <tt>UUID</tt> instance from a stream (that is,
- * deserialize it). This is necessary to set the transient fields
- * to their correct uninitialized value so they will be recomputed
- * on demand.
- */
- private void readObject(java.io.ObjectInputStream in)
- throws java.io.IOException, ClassNotFoundException {
-
- in.defaultReadObject();
-
- // Set "cached computation" fields to their initial values
- version = -1;
- variant = -1;
- timestamp = -1;
- sequence = -1;
- node = -1;
- hashCode = -1;
- }
- }