rev 51958 : 8211122: Reduce the number of internal classes made accessible to jdk.unsupported
Reviewed-by: alanb, dfuchs, kvn

   1 /*
   2  * Copyright (c) 2003, 2018, 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 jdk.internal.access.JavaLangAccess;
  31 import jdk.internal.access.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  * &quot;Algorithms for Creating a Time-Based UUID&quot;.
  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         int len = name.length();
 198         if (len > 36) {
 199             throw new IllegalArgumentException("UUID string too large");
 200         }
 201 
 202         int dash1 = name.indexOf('-', 0);
 203         int dash2 = name.indexOf('-', dash1 + 1);
 204         int dash3 = name.indexOf('-', dash2 + 1);
 205         int dash4 = name.indexOf('-', dash3 + 1);
 206         int dash5 = name.indexOf('-', dash4 + 1);
 207 
 208         // For any valid input, dash1 through dash4 will be positive and dash5
 209         // negative, but it's enough to check dash4 and dash5:
 210         // - if dash1 is -1, dash4 will be -1
 211         // - if dash1 is positive but dash2 is -1, dash4 will be -1
 212         // - if dash1 and dash2 is positive, dash3 will be -1, dash4 will be
 213         //   positive, but so will dash5
 214         if (dash4 < 0 || dash5 >= 0) {
 215             throw new IllegalArgumentException("Invalid UUID string: " + name);
 216         }
 217 
 218         long mostSigBits = Long.parseLong(name, 0, dash1, 16) & 0xffffffffL;
 219         mostSigBits <<= 16;
 220         mostSigBits |= Long.parseLong(name, dash1 + 1, dash2, 16) & 0xffffL;
 221         mostSigBits <<= 16;
 222         mostSigBits |= Long.parseLong(name, dash2 + 1, dash3, 16) & 0xffffL;
 223         long leastSigBits = Long.parseLong(name, dash3 + 1, dash4, 16) & 0xffffL;
 224         leastSigBits <<= 48;
 225         leastSigBits |= Long.parseLong(name, dash4 + 1, len, 16) & 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         return jla.fastUUID(leastSigBits, mostSigBits);
 396     }
 397 
 398     /**
 399      * Returns a hash code for this {@code UUID}.
 400      *
 401      * @return  A hash code value for this {@code UUID}
 402      */
 403     public int hashCode() {
 404         long hilo = mostSigBits ^ leastSigBits;
 405         return ((int)(hilo >> 32)) ^ (int) hilo;
 406     }
 407 
 408     /**
 409      * Compares this object to the specified object.  The result is {@code
 410      * true} if and only if the argument is not {@code null}, is a {@code UUID}
 411      * object, has the same variant, and contains the same value, bit for bit,
 412      * as this {@code UUID}.
 413      *
 414      * @param  obj
 415      *         The object to be compared
 416      *
 417      * @return  {@code true} if the objects are the same; {@code false}
 418      *          otherwise
 419      */
 420     public boolean equals(Object obj) {
 421         if ((null == obj) || (obj.getClass() != UUID.class))
 422             return false;
 423         UUID id = (UUID)obj;
 424         return (mostSigBits == id.mostSigBits &&
 425                 leastSigBits == id.leastSigBits);
 426     }
 427 
 428     // Comparison Operations
 429 
 430     /**
 431      * Compares this UUID with the specified UUID.
 432      *
 433      * <p> The first of two UUIDs is greater than the second if the most
 434      * significant field in which the UUIDs differ is greater for the first
 435      * UUID.
 436      *
 437      * @param  val
 438      *         {@code UUID} to which this {@code UUID} is to be compared
 439      *
 440      * @return  -1, 0 or 1 as this {@code UUID} is less than, equal to, or
 441      *          greater than {@code val}
 442      *
 443      */
 444     public int compareTo(UUID val) {
 445         // The ordering is intentionally set up so that the UUIDs
 446         // can simply be numerically compared as two numbers
 447         return (this.mostSigBits < val.mostSigBits ? -1 :
 448                 (this.mostSigBits > val.mostSigBits ? 1 :
 449                  (this.leastSigBits < val.leastSigBits ? -1 :
 450                   (this.leastSigBits > val.leastSigBits ? 1 :
 451                    0))));
 452     }
 453 }
--- EOF ---