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 android.compat.Compatibility; 29 import android.compat.annotation.ChangeId; 30 import android.compat.annotation.EnabledSince; 31 32 import dalvik.annotation.compat.VersionCodes; 33 import dalvik.system.VMRuntime; 34 35 import java.security.*; 36 37 // Android-removed: not using JavaLangAccess.fastUUID. 38 // import jdk.internal.misc.JavaLangAccess; 39 // import jdk.internal.misc.SharedSecrets; 40 41 /** 42 * A class that represents an immutable universally unique identifier (UUID). 43 * A UUID represents a 128-bit value. 44 * 45 * <p> There exist different variants of these global identifiers. The methods 46 * of this class are for manipulating the Leach-Salz variant, although the 47 * constructors allow the creation of any variant of UUID (described below). 48 * 49 * <p> The layout of a variant 2 (Leach-Salz) UUID is as follows: 50 * 51 * The most significant long consists of the following unsigned fields: 52 * <pre> 53 * 0xFFFFFFFF00000000 time_low 54 * 0x00000000FFFF0000 time_mid 55 * 0x000000000000F000 version 56 * 0x0000000000000FFF time_hi 57 * </pre> 58 * The least significant long consists of the following unsigned fields: 59 * <pre> 60 * 0xC000000000000000 variant 61 * 0x3FFF000000000000 clock_seq 62 * 0x0000FFFFFFFFFFFF node 63 * </pre> 64 * 65 * <p> The variant field contains a value which identifies the layout of the 66 * {@code UUID}. The bit layout described above is valid only for a {@code 67 * UUID} with a variant value of 2, which indicates the Leach-Salz variant. 68 * 69 * <p> The version field holds a value that describes the type of this {@code 70 * UUID}. There are four different basic types of UUIDs: time-based, DCE 71 * security, name-based, and randomly generated UUIDs. These types have a 72 * version value of 1, 2, 3 and 4, respectively. 73 * 74 * <p> For more information including algorithms used to create {@code UUID}s, 75 * see <a href="http://www.ietf.org/rfc/rfc4122.txt"> <i>RFC 4122: A 76 * Universally Unique IDentifier (UUID) URN Namespace</i></a>, section 4.2 77 * "Algorithms for Creating a Time-Based UUID". 78 * 79 * @since 1.5 80 */ 81 public final class UUID implements java.io.Serializable, Comparable<UUID> { 82 83 /** 84 * Explicit serialVersionUID for interoperability. 85 */ 86 private static final long serialVersionUID = -4856846361193249489L; 87 88 /* 89 * The most significant 64 bits of this UUID. 90 * 91 * @serial 92 */ 93 private final long mostSigBits; 94 95 /* 96 * The least significant 64 bits of this UUID. 97 * 98 * @serial 99 */ 100 private final long leastSigBits; 101 102 // Android-removed: not using JavaLangAccess.fastUUID. 103 // private static final JavaLangAccess jla = SharedSecrets.getJavaLangAccess(); 104 105 /* 106 * The random number generator used by this class to create random 107 * based UUIDs. In a holder class to defer initialization until needed. 108 */ 109 private static class Holder { 110 static final SecureRandom numberGenerator = new SecureRandom(); 111 } 112 113 // Constructors and Factories 114 115 /* 116 * Private constructor which uses a byte array to construct the new UUID. 117 */ UUID(byte[] data)118 private UUID(byte[] data) { 119 long msb = 0; 120 long lsb = 0; 121 assert data.length == 16 : "data must be 16 bytes in length"; 122 for (int i=0; i<8; i++) 123 msb = (msb << 8) | (data[i] & 0xff); 124 for (int i=8; i<16; i++) 125 lsb = (lsb << 8) | (data[i] & 0xff); 126 this.mostSigBits = msb; 127 this.leastSigBits = lsb; 128 } 129 130 /** 131 * Constructs a new {@code UUID} using the specified data. {@code 132 * mostSigBits} is used for the most significant 64 bits of the {@code 133 * UUID} and {@code leastSigBits} becomes the least significant 64 bits of 134 * the {@code UUID}. 135 * 136 * @param mostSigBits 137 * The most significant bits of the {@code UUID} 138 * 139 * @param leastSigBits 140 * The least significant bits of the {@code UUID} 141 */ UUID(long mostSigBits, long leastSigBits)142 public UUID(long mostSigBits, long leastSigBits) { 143 this.mostSigBits = mostSigBits; 144 this.leastSigBits = leastSigBits; 145 } 146 147 /** 148 * Static factory to retrieve a type 4 (pseudo randomly generated) UUID. 149 * 150 * The {@code UUID} is generated using a cryptographically strong pseudo 151 * random number generator. 152 * 153 * @return A randomly generated {@code UUID} 154 */ randomUUID()155 public static UUID randomUUID() { 156 SecureRandom ng = Holder.numberGenerator; 157 158 byte[] randomBytes = new byte[16]; 159 ng.nextBytes(randomBytes); 160 randomBytes[6] &= 0x0f; /* clear version */ 161 randomBytes[6] |= 0x40; /* set to version 4 */ 162 randomBytes[8] &= 0x3f; /* clear variant */ 163 randomBytes[8] |= 0x80; /* set to IETF variant */ 164 return new UUID(randomBytes); 165 } 166 167 /** 168 * Static factory to retrieve a type 3 (name based) {@code UUID} based on 169 * the specified byte array. 170 * 171 * @param name 172 * A byte array to be used to construct a {@code UUID} 173 * 174 * @return A {@code UUID} generated from the specified array 175 */ nameUUIDFromBytes(byte[] name)176 public static UUID nameUUIDFromBytes(byte[] name) { 177 MessageDigest md; 178 try { 179 md = MessageDigest.getInstance("MD5"); 180 } catch (NoSuchAlgorithmException nsae) { 181 throw new InternalError("MD5 not supported", nsae); 182 } 183 byte[] md5Bytes = md.digest(name); 184 md5Bytes[6] &= 0x0f; /* clear version */ 185 md5Bytes[6] |= 0x30; /* set to version 3 */ 186 md5Bytes[8] &= 0x3f; /* clear variant */ 187 md5Bytes[8] |= 0x80; /* set to IETF variant */ 188 return new UUID(md5Bytes); 189 } 190 191 /** 192 * Since Android 14 {@link #fromString} does more strict input argument 193 * validation. 194 * 195 * This flag is enabled for apps targeting Android 14+. 196 * 197 * @hide 198 */ 199 @ChangeId 200 @EnabledSince(targetSdkVersion = VersionCodes.UPSIDE_DOWN_CAKE) 201 public static final long ENABLE_STRICT_VALIDATION = 263076149L; 202 203 /** 204 * Creates a {@code UUID} from the string standard representation as 205 * described in the {@link #toString} method. 206 * 207 * @param name 208 * A string that specifies a {@code UUID} 209 * 210 * @return A {@code UUID} with the specified value 211 * 212 * @throws IllegalArgumentException 213 * If name does not conform to the string representation as 214 * described in {@link #toString} 215 * 216 */ fromString(String name)217 public static UUID fromString(String name) { 218 // BEGIN Android-changed: Java 8 behaviour is more lenient and the new implementation 219 // might break apps (b/254278943). 220 // Using old implementation for apps targeting Android older than U. 221 if (!(VMRuntime.getSdkVersion() >= VersionCodes.UPSIDE_DOWN_CAKE 222 && Compatibility.isChangeEnabled(ENABLE_STRICT_VALIDATION))) { 223 return fromStringJava8(name); 224 } 225 226 return fromStringJava11(name); 227 // END Android-changed: Java 8 behaviour is more lenient and the new implementation 228 // might break apps (b/254278943). 229 } 230 231 /** 232 * Extracted for testing purposes only. 233 * @hide 234 */ fromStringJava11(String name)235 public static UUID fromStringJava11(String name) { 236 int len = name.length(); 237 if (len > 36) { 238 throw new IllegalArgumentException("UUID string too large"); 239 } 240 241 int dash1 = name.indexOf('-', 0); 242 int dash2 = name.indexOf('-', dash1 + 1); 243 int dash3 = name.indexOf('-', dash2 + 1); 244 int dash4 = name.indexOf('-', dash3 + 1); 245 int dash5 = name.indexOf('-', dash4 + 1); 246 247 // For any valid input, dash1 through dash4 will be positive and dash5 248 // negative, but it's enough to check dash4 and dash5: 249 // - if dash1 is -1, dash4 will be -1 250 // - if dash1 is positive but dash2 is -1, dash4 will be -1 251 // - if dash1 and dash2 is positive, dash3 will be -1, dash4 will be 252 // positive, but so will dash5 253 if (dash4 < 0 || dash5 >= 0) { 254 throw new IllegalArgumentException("Invalid UUID string: " + name); 255 } 256 257 long mostSigBits = Long.parseLong(name, 0, dash1, 16) & 0xffffffffL; 258 mostSigBits <<= 16; 259 mostSigBits |= Long.parseLong(name, dash1 + 1, dash2, 16) & 0xffffL; 260 mostSigBits <<= 16; 261 mostSigBits |= Long.parseLong(name, dash2 + 1, dash3, 16) & 0xffffL; 262 long leastSigBits = Long.parseLong(name, dash3 + 1, dash4, 16) & 0xffffL; 263 leastSigBits <<= 48; 264 leastSigBits |= Long.parseLong(name, dash4 + 1, len, 16) & 0xffffffffffffL; 265 266 return new UUID(mostSigBits, leastSigBits); 267 } 268 269 /** 270 * Extracted for testing purposes only. 271 * @hide 272 */ fromStringJava8(String name)273 public static UUID fromStringJava8(String name) { 274 String[] components = name.split("-"); 275 if (components.length != 5) 276 throw new IllegalArgumentException("Invalid UUID string: "+ name); 277 for (int i=0; i<5; i++) 278 components[i] = "0x"+components[i]; 279 280 long mostSigBits = Long.decode(components[0]).longValue(); 281 mostSigBits <<= 16; 282 mostSigBits |= Long.decode(components[1]).longValue(); 283 mostSigBits <<= 16; 284 mostSigBits |= Long.decode(components[2]).longValue(); 285 286 long leastSigBits = Long.decode(components[3]).longValue(); 287 leastSigBits <<= 48; 288 leastSigBits |= Long.decode(components[4]).longValue(); 289 290 return new UUID(mostSigBits, leastSigBits); 291 } 292 293 // Field Accessor Methods 294 295 /** 296 * Returns the least significant 64 bits of this UUID's 128 bit value. 297 * 298 * @return The least significant 64 bits of this UUID's 128 bit value 299 */ getLeastSignificantBits()300 public long getLeastSignificantBits() { 301 return leastSigBits; 302 } 303 304 /** 305 * Returns the most significant 64 bits of this UUID's 128 bit value. 306 * 307 * @return The most significant 64 bits of this UUID's 128 bit value 308 */ getMostSignificantBits()309 public long getMostSignificantBits() { 310 return mostSigBits; 311 } 312 313 /** 314 * The version number associated with this {@code UUID}. The version 315 * number describes how this {@code UUID} was generated. 316 * 317 * The version number has the following meaning: 318 * <ul> 319 * <li>1 Time-based UUID 320 * <li>2 DCE security UUID 321 * <li>3 Name-based UUID 322 * <li>4 Randomly generated UUID 323 * </ul> 324 * 325 * @return The version number of this {@code UUID} 326 */ version()327 public int version() { 328 // Version is bits masked by 0x000000000000F000 in MS long 329 return (int)((mostSigBits >> 12) & 0x0f); 330 } 331 332 /** 333 * The variant number associated with this {@code UUID}. The variant 334 * number describes the layout of the {@code UUID}. 335 * 336 * The variant number has the following meaning: 337 * <ul> 338 * <li>0 Reserved for NCS backward compatibility 339 * <li>2 <a href="http://www.ietf.org/rfc/rfc4122.txt">IETF RFC 4122</a> 340 * (Leach-Salz), used by this class 341 * <li>6 Reserved, Microsoft Corporation backward compatibility 342 * <li>7 Reserved for future definition 343 * </ul> 344 * 345 * @return The variant number of this {@code UUID} 346 */ variant()347 public int variant() { 348 // This field is composed of a varying number of bits. 349 // 0 - - Reserved for NCS backward compatibility 350 // 1 0 - The IETF aka Leach-Salz variant (used by this class) 351 // 1 1 0 Reserved, Microsoft backward compatibility 352 // 1 1 1 Reserved for future definition. 353 return (int) ((leastSigBits >>> (64 - (leastSigBits >>> 62))) 354 & (leastSigBits >> 63)); 355 } 356 357 /** 358 * The timestamp value associated with this UUID. 359 * 360 * <p> The 60 bit timestamp value is constructed from the time_low, 361 * time_mid, and time_hi fields of this {@code UUID}. The resulting 362 * timestamp is measured in 100-nanosecond units since midnight, 363 * October 15, 1582 UTC. 364 * 365 * <p> The timestamp value is only meaningful in a time-based UUID, which 366 * has version type 1. If this {@code UUID} is not a time-based UUID then 367 * this method throws UnsupportedOperationException. 368 * 369 * @throws UnsupportedOperationException 370 * If this UUID is not a version 1 UUID 371 * @return The timestamp of this {@code UUID}. 372 */ timestamp()373 public long timestamp() { 374 if (version() != 1) { 375 throw new UnsupportedOperationException("Not a time-based UUID"); 376 } 377 378 return (mostSigBits & 0x0FFFL) << 48 379 | ((mostSigBits >> 16) & 0x0FFFFL) << 32 380 | mostSigBits >>> 32; 381 } 382 383 /** 384 * The clock sequence value associated with this UUID. 385 * 386 * <p> The 14 bit clock sequence value is constructed from the clock 387 * sequence field of this UUID. The clock sequence field is used to 388 * guarantee temporal uniqueness in a time-based UUID. 389 * 390 * <p> The {@code clockSequence} value is only meaningful in a time-based 391 * UUID, which has version type 1. If this UUID is not a time-based UUID 392 * then this method throws UnsupportedOperationException. 393 * 394 * @return The clock sequence of this {@code UUID} 395 * 396 * @throws UnsupportedOperationException 397 * If this UUID is not a version 1 UUID 398 */ clockSequence()399 public int clockSequence() { 400 if (version() != 1) { 401 throw new UnsupportedOperationException("Not a time-based UUID"); 402 } 403 404 return (int)((leastSigBits & 0x3FFF000000000000L) >>> 48); 405 } 406 407 /** 408 * The node value associated with this UUID. 409 * 410 * <p> The 48 bit node value is constructed from the node field of this 411 * UUID. This field is intended to hold the IEEE 802 address of the machine 412 * that generated this UUID to guarantee spatial uniqueness. 413 * 414 * <p> The node value is only meaningful in a time-based UUID, which has 415 * version type 1. If this UUID is not a time-based UUID then this method 416 * throws UnsupportedOperationException. 417 * 418 * @return The node value of this {@code UUID} 419 * 420 * @throws UnsupportedOperationException 421 * If this UUID is not a version 1 UUID 422 */ node()423 public long node() { 424 if (version() != 1) { 425 throw new UnsupportedOperationException("Not a time-based UUID"); 426 } 427 428 return leastSigBits & 0x0000FFFFFFFFFFFFL; 429 } 430 431 // Object Inherited Methods 432 433 /** 434 * Returns a {@code String} object representing this {@code UUID}. 435 * 436 * <p> The UUID string representation is as described by this BNF: 437 * <blockquote><pre> 438 * {@code 439 * UUID = <time_low> "-" <time_mid> "-" 440 * <time_high_and_version> "-" 441 * <variant_and_sequence> "-" 442 * <node> 443 * time_low = 4*<hexOctet> 444 * time_mid = 2*<hexOctet> 445 * time_high_and_version = 2*<hexOctet> 446 * variant_and_sequence = 2*<hexOctet> 447 * node = 6*<hexOctet> 448 * hexOctet = <hexDigit><hexDigit> 449 * hexDigit = 450 * "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" 451 * | "a" | "b" | "c" | "d" | "e" | "f" 452 * | "A" | "B" | "C" | "D" | "E" | "F" 453 * }</pre></blockquote> 454 * 455 * @return A string representation of this {@code UUID} 456 */ toString()457 public String toString() { 458 // Android-changed: using old implementation. 459 // return jla.fastUUID(leastSigBits, mostSigBits); 460 return (digits(mostSigBits >> 32, 8) + "-" + 461 digits(mostSigBits >> 16, 4) + "-" + 462 digits(mostSigBits, 4) + "-" + 463 digits(leastSigBits >> 48, 4) + "-" + 464 digits(leastSigBits, 12)); 465 } 466 467 /** Returns val represented by the specified number of hex digits. */ digits(long val, int digits)468 private static String digits(long val, int digits) { 469 long hi = 1L << (digits * 4); 470 return Long.toHexString(hi | (val & (hi - 1))).substring(1); 471 } 472 473 /** 474 * Returns a hash code for this {@code UUID}. 475 * 476 * @return A hash code value for this {@code UUID} 477 */ hashCode()478 public int hashCode() { 479 long hilo = mostSigBits ^ leastSigBits; 480 return ((int)(hilo >> 32)) ^ (int) hilo; 481 } 482 483 /** 484 * Compares this object to the specified object. The result is {@code 485 * true} if and only if the argument is not {@code null}, is a {@code UUID} 486 * object, has the same variant, and contains the same value, bit for bit, 487 * as this {@code UUID}. 488 * 489 * @param obj 490 * The object to be compared 491 * 492 * @return {@code true} if the objects are the same; {@code false} 493 * otherwise 494 */ equals(Object obj)495 public boolean equals(Object obj) { 496 if ((null == obj) || (obj.getClass() != UUID.class)) 497 return false; 498 UUID id = (UUID)obj; 499 return (mostSigBits == id.mostSigBits && 500 leastSigBits == id.leastSigBits); 501 } 502 503 // Comparison Operations 504 505 /** 506 * Compares this UUID with the specified UUID. 507 * 508 * <p> The first of two UUIDs is greater than the second if the most 509 * significant field in which the UUIDs differ is greater for the first 510 * UUID. 511 * 512 * @param val 513 * {@code UUID} to which this {@code UUID} is to be compared 514 * 515 * @return -1, 0 or 1 as this {@code UUID} is less than, equal to, or 516 * greater than {@code val} 517 * 518 */ compareTo(UUID val)519 public int compareTo(UUID val) { 520 // The ordering is intentionally set up so that the UUIDs 521 // can simply be numerically compared as two numbers 522 return (this.mostSigBits < val.mostSigBits ? -1 : 523 (this.mostSigBits > val.mostSigBits ? 1 : 524 (this.leastSigBits < val.leastSigBits ? -1 : 525 (this.leastSigBits > val.leastSigBits ? 1 : 526 0)))); 527 } 528 } 529