1 /*

     2  * Copyright (c) 2003, 2014, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package java.util;

    27 

    28 import java.security.*;

    29 

    30 import sun.misc.JavaLangAccess;

    31 import sun.misc.SharedSecrets;

    32 

    33 /**

    34  * A class that represents an immutable universally unique identifier (UUID).

    35  * A UUID represents a 128-bit value.

    36  *

    37  * <p> There exist different variants of these global identifiers.  The methods

    38  * of this class are for manipulating the Leach-Salz variant, although the

    39  * constructors allow the creation of any variant of UUID (described below).

    40  *

    41  * <p> The layout of a variant 2 (Leach-Salz) UUID is as follows:

    42  *

    43  * The most significant long consists of the following unsigned fields:

    44  * <pre>

    45  * 0xFFFFFFFF00000000 time_low

    46  * 0x00000000FFFF0000 time_mid

    47  * 0x000000000000F000 version

    48  * 0x0000000000000FFF time_hi

    49  * </pre>

    50  * The least significant long consists of the following unsigned fields:

    51  * <pre>

    52  * 0xC000000000000000 variant

    53  * 0x3FFF000000000000 clock_seq

    54  * 0x0000FFFFFFFFFFFF node

    55  * </pre>

    56  *

    57  * <p> The variant field contains a value which identifies the layout of the

    58  * {@code UUID}.  The bit layout described above is valid only for a {@code

    59  * UUID} with a variant value of 2, which indicates the Leach-Salz variant.

    60  *

    61  * <p> The version field holds a value that describes the type of this {@code

    62  * UUID}.  There are four different basic types of UUIDs: time-based, DCE

    63  * security, name-based, and randomly generated UUIDs.  These types have a

    64  * version value of 1, 2, 3 and 4, respectively.

    65  *

    66  * <p> For more information including algorithms used to create {@code UUID}s,

    67  * see <a href="http://www.ietf.org/rfc/rfc4122.txt"> <i>RFC&nbsp;4122: A

    68  * Universally Unique IDentifier (UUID) URN Namespace</i></a>, section 4.2

    69  * "Algorithms for Creating a Time-Based UUID".

    70  *

    71  * @since   1.5

    72  */

    73 public final class UUID implements java.io.Serializable, Comparable<UUID> {

    74 

    75     /**

    76      * Explicit serialVersionUID for interoperability.

    77      */

    78     private static final long serialVersionUID = -4856846361193249489L;

    79 

    80     /*

    81      * The most significant 64 bits of this UUID.

    82      *

    83      * @serial

    84      */

    85     private final long mostSigBits;

    86 

    87     /*

    88      * The least significant 64 bits of this UUID.

    89      *

    90      * @serial

    91      */

    92     private final long leastSigBits;

    93 

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

    95 

    96     /*

    97      * The random number generator used by this class to create random

    98      * based UUIDs. In a holder class to defer initialization until needed.

    99      */

   100     private static class Holder {

   101         static final SecureRandom numberGenerator = new SecureRandom();

   102     }

   103 

   104     // Constructors and Factories

   105 

   106     /*

   107      * Private constructor which uses a byte array to construct the new UUID.

   108      */

   109     private UUID(byte[] data) {

   110         long msb = 0;

   111         long lsb = 0;

   112         assert data.length == 16 : "data must be 16 bytes in length";

   113         for (int i=0; i<8; i++)

   114             msb = (msb << 8) | (data[i] & 0xff);

   115         for (int i=8; i<16; i++)

   116             lsb = (lsb << 8) | (data[i] & 0xff);

   117         this.mostSigBits = msb;

   118         this.leastSigBits = lsb;

   119     }

   120 

   121     /**

   122      * Constructs a new {@code UUID} using the specified data.  {@code

   123      * mostSigBits} is used for the most significant 64 bits of the {@code

   124      * UUID} and {@code leastSigBits} becomes the least significant 64 bits of

   125      * the {@code UUID}.

   126      *

   127      * @param  mostSigBits

   128      *         The most significant bits of the {@code UUID}

   129      *

   130      * @param  leastSigBits

   131      *         The least significant bits of the {@code UUID}

   132      */

   133     public UUID(long mostSigBits, long leastSigBits) {

   134         this.mostSigBits = mostSigBits;

   135         this.leastSigBits = leastSigBits;

   136     }

   137 

   138     /**

   139      * Static factory to retrieve a type 4 (pseudo randomly generated) UUID.

   140      *

   141      * The {@code UUID} is generated using a cryptographically strong pseudo

   142      * random number generator.

   143      *

   144      * @return  A randomly generated {@code UUID}

   145      */

   146     public static UUID randomUUID() {

   147         SecureRandom ng = Holder.numberGenerator;

   148 

   149         byte[] randomBytes = new byte[16];

   150         ng.nextBytes(randomBytes);

   151         randomBytes[6]  &= 0x0f;  /* clear version        */

   152         randomBytes[6]  |= 0x40;  /* set to version 4     */

   153         randomBytes[8]  &= 0x3f;  /* clear variant        */

   154         randomBytes[8]  |= 0x80;  /* set to IETF variant  */

   155         return new UUID(randomBytes);

   156     }

   157 

   158     /**

   159      * Static factory to retrieve a type 3 (name based) {@code UUID} based on

   160      * the specified byte array.

   161      *

   162      * @param  name

   163      *         A byte array to be used to construct a {@code UUID}

   164      *

   165      * @return  A {@code UUID} generated from the specified array

   166      */

   167     public static UUID nameUUIDFromBytes(byte[] name) {

   168         MessageDigest md;

   169         try {

   170             md = MessageDigest.getInstance("MD5");

   171         } catch (NoSuchAlgorithmException nsae) {

   172             throw new InternalError("MD5 not supported", nsae);

   173         }

   174         byte[] md5Bytes = md.digest(name);

   175         md5Bytes[6]  &= 0x0f;  /* clear version        */

   176         md5Bytes[6]  |= 0x30;  /* set to version 3     */

   177         md5Bytes[8]  &= 0x3f;  /* clear variant        */

   178         md5Bytes[8]  |= 0x80;  /* set to IETF variant  */

   179         return new UUID(md5Bytes);

   180     }

   181 

   182     /**

   183      * Creates a {@code UUID} from the string standard representation as

   184      * described in the {@link #toString} method.

   185      *

   186      * @param  name

   187      *         A string that specifies a {@code UUID}

   188      *

   189      * @return  A {@code UUID} with the specified value

   190      *

   191      * @throws  IllegalArgumentException

   192      *          If name does not conform to the string representation as

   193      *          described in {@link #toString}

   194      *

   195      */

   196     public static UUID fromString(String name) {

   197         if (name.length() > 36) {

   198             throw new IllegalArgumentException("UUID string too large");

   199         }

   200 

   201         int dash1 = name.indexOf('-', 0);

   202         int dash2 = name.indexOf('-', dash1 + 1);

   203         int dash3 = name.indexOf('-', dash2 + 1);

   204         int dash4 = name.indexOf('-', dash3 + 1);

   205         int dash5 = name.indexOf('-', dash4 + 1);

   206 

   207         // For any valid input, dash1 through dash4 will be positive and dash5

   208         // negative, but it's enough to check dash4 and dash5:

   209         // - if dash1 is -1, dash4 will be -1

   210         // - if dash1 is positive but dash2 is -1, dash4 will be -1

   211         // - if dash1 and dash2 is positive, dash3 will be -1, dash4 will be

   212         //   positive, but so will dash5

   213         if (dash4 < 0 || dash5 >= 0) {

   214             throw new IllegalArgumentException("Invalid UUID string: " + name);

   215         }

   216 

   217         long mostSigBits = Long.parseLong(name, 16, 0, dash1) & 0xffffffffL;

   218         mostSigBits <<= 16;

   219         mostSigBits |= Long.parseLong(name, 16, dash1 + 1, dash2) & 0xffffL;

   220         mostSigBits <<= 16;

   221         mostSigBits |= Long.parseLong(name, 16, dash2 + 1, dash3) & 0xffffL;

   222 

   223         long leastSigBits = Long.parseLong(name, 16, dash3 + 1, dash4) & 0xffffL;

   224         leastSigBits <<= 48;

   225         leastSigBits |= Long.parseLong(name, 16, dash4 + 1) & 0xffffffffffffL;

   226 

   227         return new UUID(mostSigBits, leastSigBits);

   228     }

   229 

   230     // Field Accessor Methods

   231 

   232     /**

   233      * Returns the least significant 64 bits of this UUID's 128 bit value.

   234      *

   235      * @return  The least significant 64 bits of this UUID's 128 bit value

   236      */

   237     public long getLeastSignificantBits() {

   238         return leastSigBits;

   239     }

   240 

   241     /**

   242      * Returns the most significant 64 bits of this UUID's 128 bit value.

   243      *

   244      * @return  The most significant 64 bits of this UUID's 128 bit value

   245      */

   246     public long getMostSignificantBits() {

   247         return mostSigBits;

   248     }

   249 

   250     /**

   251      * The version number associated with this {@code UUID}.  The version

   252      * number describes how this {@code UUID} was generated.

   253      *

   254      * The version number has the following meaning:

   255      * <ul>

   256      * <li>1    Time-based UUID

   257      * <li>2    DCE security UUID

   258      * <li>3    Name-based UUID

   259      * <li>4    Randomly generated UUID

   260      * </ul>

   261      *

   262      * @return  The version number of this {@code UUID}

   263      */

   264     public int version() {

   265         // Version is bits masked by 0x000000000000F000 in MS long

   266         return (int)((mostSigBits >> 12) & 0x0f);

   267     }

   268 

   269     /**

   270      * The variant number associated with this {@code UUID}.  The variant

   271      * number describes the layout of the {@code UUID}.

   272      *

   273      * The variant number has the following meaning:

   274      * <ul>

   275      * <li>0    Reserved for NCS backward compatibility

   276      * <li>2    <a href="http://www.ietf.org/rfc/rfc4122.txt">IETF&nbsp;RFC&nbsp;4122</a>

   277      * (Leach-Salz), used by this class

   278      * <li>6    Reserved, Microsoft Corporation backward compatibility

   279      * <li>7    Reserved for future definition

   280      * </ul>

   281      *

   282      * @return  The variant number of this {@code UUID}

   283      */

   284     public int variant() {

   285         // This field is composed of a varying number of bits.

   286         // 0    -    -    Reserved for NCS backward compatibility

   287         // 1    0    -    The IETF aka Leach-Salz variant (used by this class)

   288         // 1    1    0    Reserved, Microsoft backward compatibility

   289         // 1    1    1    Reserved for future definition.

   290         return (int) ((leastSigBits >>> (64 - (leastSigBits >>> 62)))

   291                       & (leastSigBits >> 63));

   292     }

   293 

   294     /**

   295      * The timestamp value associated with this UUID.

   296      *

   297      * <p> The 60 bit timestamp value is constructed from the time_low,

   298      * time_mid, and time_hi fields of this {@code UUID}.  The resulting

   299      * timestamp is measured in 100-nanosecond units since midnight,

   300      * October 15, 1582 UTC.

   301      *

   302      * <p> The timestamp value is only meaningful in a time-based UUID, which

   303      * has version type 1.  If this {@code UUID} is not a time-based UUID then

   304      * this method throws UnsupportedOperationException.

   305      *

   306      * @throws UnsupportedOperationException

   307      *         If this UUID is not a version 1 UUID

   308      * @return The timestamp of this {@code UUID}.

   309      */

   310     public long timestamp() {

   311         if (version() != 1) {

   312             throw new UnsupportedOperationException("Not a time-based UUID");

   313         }

   314 

   315         return (mostSigBits & 0x0FFFL) << 48

   316              | ((mostSigBits >> 16) & 0x0FFFFL) << 32

   317              | mostSigBits >>> 32;

   318     }

   319 

   320     /**

   321      * The clock sequence value associated with this UUID.

   322      *

   323      * <p> The 14 bit clock sequence value is constructed from the clock

   324      * sequence field of this UUID.  The clock sequence field is used to

   325      * guarantee temporal uniqueness in a time-based UUID.

   326      *

   327      * <p> The {@code clockSequence} value is only meaningful in a time-based

   328      * UUID, which has version type 1.  If this UUID is not a time-based UUID

   329      * then this method throws UnsupportedOperationException.

   330      *

   331      * @return  The clock sequence of this {@code UUID}

   332      *

   333      * @throws  UnsupportedOperationException

   334      *          If this UUID is not a version 1 UUID

   335      */

   336     public int clockSequence() {

   337         if (version() != 1) {

   338             throw new UnsupportedOperationException("Not a time-based UUID");

   339         }

   340 

   341         return (int)((leastSigBits & 0x3FFF000000000000L) >>> 48);

   342     }

   343 

   344     /**

   345      * The node value associated with this UUID.

   346      *

   347      * <p> The 48 bit node value is constructed from the node field of this

   348      * UUID.  This field is intended to hold the IEEE 802 address of the machine

   349      * that generated this UUID to guarantee spatial uniqueness.

   350      *

   351      * <p> The node value is only meaningful in a time-based UUID, which has

   352      * version type 1.  If this UUID is not a time-based UUID then this method

   353      * throws UnsupportedOperationException.

   354      *

   355      * @return  The node value of this {@code UUID}

   356      *

   357      * @throws  UnsupportedOperationException

   358      *          If this UUID is not a version 1 UUID

   359      */

   360     public long node() {

   361         if (version() != 1) {

   362             throw new UnsupportedOperationException("Not a time-based UUID");

   363         }

   364 

   365         return leastSigBits & 0x0000FFFFFFFFFFFFL;

   366     }

   367 

   368     // Object Inherited Methods

   369 

   370     /**

   371      * Returns a {@code String} object representing this {@code UUID}.

   372      *

   373      * <p> The UUID string representation is as described by this BNF:

   374      * <blockquote><pre>

   375      * {@code

   376      * UUID                   = <time_low> "-" <time_mid> "-"

   377      *                          <time_high_and_version> "-"

   378      *                          <variant_and_sequence> "-"

   379      *                          <node>

   380      * time_low               = 4*<hexOctet>

   381      * time_mid               = 2*<hexOctet>

   382      * time_high_and_version  = 2*<hexOctet>

   383      * variant_and_sequence   = 2*<hexOctet>

   384      * node                   = 6*<hexOctet>

   385      * hexOctet               = <hexDigit><hexDigit>

   386      * hexDigit               =

   387      *       "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"

   388      *       | "a" | "b" | "c" | "d" | "e" | "f"

   389      *       | "A" | "B" | "C" | "D" | "E" | "F"

   390      * }</pre></blockquote>

   391      *

   392      * @return  A string representation of this {@code UUID}

   393      */

   394     public String toString() {

   395         char[] chars = new char[36];

   396         jla.formatUnsignedLong(mostSigBits >> 32, 4, chars, 0, 8);

   397         chars[8] = '-';

   398         jla.formatUnsignedLong(mostSigBits >> 16, 4, chars, 9, 4);

   399         chars[13] = '-';

   400         jla.formatUnsignedLong(mostSigBits, 4, chars, 14, 4);

   401         chars[18] = '-';

   402         jla.formatUnsignedLong(leastSigBits >> 48, 4, chars, 19, 4);

   403         chars[23] = '-';

   404         jla.formatUnsignedLong(leastSigBits, 4, chars, 24, 12);

   405         return jla.newStringUnsafe(chars);

   406     }

   407 

   408     /**

   409      * Returns a hash code for this {@code UUID}.

   410      *

   411      * @return  A hash code value for this {@code UUID}

   412      */

   413     public int hashCode() {

   414         long hilo = mostSigBits ^ leastSigBits;

   415         return ((int)(hilo >> 32)) ^ (int) hilo;

   416     }

   417 

   418     /**

   419      * Compares this object to the specified object.  The result is {@code

   420      * true} if and only if the argument is not {@code null}, is a {@code UUID}

   421      * object, has the same variant, and contains the same value, bit for bit,

   422      * as this {@code UUID}.

   423      *

   424      * @param  obj

   425      *         The object to be compared

   426      *

   427      * @return  {@code true} if the objects are the same; {@code false}

   428      *          otherwise

   429      */

   430     public boolean equals(Object obj) {

   431         if ((null == obj) || (obj.getClass() != UUID.class))

   432             return false;

   433         UUID id = (UUID)obj;

   434         return (mostSigBits == id.mostSigBits &&

   435                 leastSigBits == id.leastSigBits);

   436     }

   437 

   438     // Comparison Operations

   439 

   440     /**

   441      * Compares this UUID with the specified UUID.

   442      *

   443      * <p> The first of two UUIDs is greater than the second if the most

   444      * significant field in which the UUIDs differ is greater for the first

   445      * UUID.

   446      *

   447      * @param  val

   448      *         {@code UUID} to which this {@code UUID} is to be compared

   449      *

   450      * @return  -1, 0 or 1 as this {@code UUID} is less than, equal to, or

   451      *          greater than {@code val}

   452      *

   453      */

   454     public int compareTo(UUID val) {

   455         // The ordering is intentionally set up so that the UUIDs

   456         // can simply be numerically compared as two numbers

   457         return (this.mostSigBits < val.mostSigBits ? -1 :

   458                 (this.mostSigBits > val.mostSigBits ? 1 :

   459                  (this.leastSigBits < val.leastSigBits ? -1 :

   460                   (this.leastSigBits > val.leastSigBits ? 1 :

   461                    0))));

   462     }

   463 }