1 /*
2 * Copyright (c) 2003, 2012, 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 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 * Provides access to String's non-public constructor that does not copy the char[]
82 */
83 private static final JavaLangAccess JAVA_LANG_ACCESS
84 = SharedSecrets.getJavaLangAccess();
85
86 /*
87 * The most significant 64 bits of this UUID.
88 *
89 * @serial
90 */
91 private final long mostSigBits;
92
93 /*
94 * The least significant 64 bits of this UUID.
95 *
96 * @serial
97 */
98 private final long leastSigBits;
99
100 /*
101 * The random number generator used by this class to create random
102 * based UUIDs. In a holder class to defer initialization until needed.
103 */
104 private static class Holder {
105 static final SecureRandom numberGenerator = new SecureRandom();
106 }
107
108 // Constructors and Factories
109
110 /*
111 * Private constructor which uses a byte array to construct the new UUID.
112 */
113 private UUID(byte[] data) {
114 long msb = 0;
115 long lsb = 0;
116 assert data.length == 16 : "data must be 16 bytes in length";
117 for (int i=0; i<8; i++)
118 msb = (msb << 8) | (data[i] & 0xff);
119 for (int i=8; i<16; i++)
120 lsb = (lsb << 8) | (data[i] & 0xff);
121 this.mostSigBits = msb;
122 this.leastSigBits = lsb;
123 }
124
125 /**
126 * Constructs a new {@code UUID} using the specified data. {@code
127 * mostSigBits} is used for the most significant 64 bits of the {@code
128 * UUID} and {@code leastSigBits} becomes the least significant 64 bits of
129 * the {@code UUID}.
130 *
131 * @param mostSigBits
132 * The most significant bits of the {@code UUID}
133 *
134 * @param leastSigBits
135 * The least significant bits of the {@code UUID}
136 */
137 public UUID(long mostSigBits, long leastSigBits) {
138 this.mostSigBits = mostSigBits;
139 this.leastSigBits = leastSigBits;
140 }
141
142 /**
143 * Static factory to retrieve a type 4 (pseudo randomly generated) UUID.
144 *
145 * The {@code UUID} is generated using a cryptographically strong pseudo
146 * random number generator.
147 *
148 * @return A randomly generated {@code UUID}
149 */
150 public static UUID randomUUID() {
151 SecureRandom ng = Holder.numberGenerator;
152
153 byte[] randomBytes = new byte[16];
154 ng.nextBytes(randomBytes);
155 randomBytes[6] &= 0x0f; /* clear version */
156 randomBytes[6] |= 0x40; /* set to version 4 */
157 randomBytes[8] &= 0x3f; /* clear variant */
158 randomBytes[8] |= 0x80; /* set to IETF variant */
159 return new UUID(randomBytes);
160 }
161
162 /**
163 * Static factory to retrieve a type 3 (name based) {@code UUID} based on
164 * the specified byte array.
165 *
166 * @param name
167 * A byte array to be used to construct a {@code UUID}
168 *
169 * @return A {@code UUID} generated from the specified array
170 */
171 public static UUID nameUUIDFromBytes(byte[] name) {
172 MessageDigest md;
173 try {
174 md = MessageDigest.getInstance("MD5");
175 } catch (NoSuchAlgorithmException nsae) {
176 throw new InternalError("MD5 not supported", nsae);
177 }
178 byte[] md5Bytes = md.digest(name);
179 md5Bytes[6] &= 0x0f; /* clear version */
180 md5Bytes[6] |= 0x30; /* set to version 3 */
181 md5Bytes[8] &= 0x3f; /* clear variant */
182 md5Bytes[8] |= 0x80; /* set to IETF variant */
183 return new UUID(md5Bytes);
184 }
185
186 /**
187 * Creates a {@code UUID} from the string standard representation as
188 * described in the {@link #toString} method.
189 *
190 * @param str
191 * A string that specifies a {@code UUID}
192 *
193 * @return A {@code UUID} with the specified value
194 *
195 * @throws IllegalArgumentException
196 * If name does not conform to the string representation as
197 * described in {@link #toString}
198 *
199 */
200 public static UUID fromString(String str) {
201 int dashCount = 4;
202 int [] dashPos = new int [6];
203 dashPos[0] = -1;
204 dashPos[5] = str.length();
205
206 for (int i = str.length()-1; i >= 0; i--) {
207 if (str.charAt(i) == '-') {
208 if (dashCount == 0) {
209 throw new IllegalArgumentException("Invalid UUID string: " + str);
210 }
211 dashPos[dashCount--] = i;
212 }
213 }
214
215 if (dashCount > 0) {
216 throw new IllegalArgumentException("Invalid UUID string: " + str);
217 }
218
219 long mostSigBits = decode(str, dashPos, 0) & 0xffffffffL;
220 mostSigBits <<= 16;
221 mostSigBits |= decode(str, dashPos, 1) & 0xffffL;
222 mostSigBits <<= 16;
223 mostSigBits |= decode(str, dashPos, 2) & 0xffffL;
224
225 long leastSigBits = decode(str, dashPos, 3) & 0xffffL;
226 leastSigBits <<= 48;
227 leastSigBits |= decode(str, dashPos, 4) & 0xffffffffffffL;
228
229 return new UUID(mostSigBits, leastSigBits);
230 }
231
232 private static long decode(final String str, final int [] dashPos, final int field) {
233 int start = dashPos[field]+1;
234 int end = dashPos[field+1];
235 if (start >= end) {
236 throw new IllegalArgumentException("Invalid UUID string: " + str);
237 }
238 return decodeLongHexString(str, start, end);
239 }
240
241 private static final int NUM_ALPHA_DIFF = 'A' - '9' - 1;
242 private static final int LOWER_UPPER_DIFF = 'a' - 'A';
243
244 /**
245 * Given a hexadecimal string, decode a portion into a long.
246 * @param str the string to decode
247 * @param start the start of the substring to decode
248 * @param end the end of the substring to decode
249 */
250 public static long decodeLongHexString(CharSequence str, int start, int end)
251 {
252 long curr = 0;
253 for (int i = start; i < end; i++) {
254 int x = getNibbleFromHexChar(str.charAt(i));
255 curr <<= 4;
256 if (curr < 0) {
257 throw new NumberFormatException("long overflow");
258 }
259 curr |= x;
260 }
261 return curr;
262 }
263
264 /**
265 * Given a hexadecimal digit, return the decimal value.
266 * @param c the character to decode
267 */
268 public static int getNibbleFromHexChar(final char c)
269 {
270 int x = c - '0';
271 if (x > 9) {
272 x -= NUM_ALPHA_DIFF; // difference between '9' and 'A'
273 if (x > 15) {
274 x -= LOWER_UPPER_DIFF; // difference between 'a' and 'A'
275 }
276 if (x < 10) {
277 throw new IllegalArgumentException(c + " is not a valid character for a hex string");
278 }
279 }
280
281 if (x < 0 || x > 15) {
282 throw new IllegalArgumentException(c + " is not a valid character for a hex string");
283 }
284
285 return x;
286 }
287
288 // Field Accessor Methods
289
290 /**
291 * Returns the least significant 64 bits of this UUID's 128 bit value.
292 *
293 * @return The least significant 64 bits of this UUID's 128 bit value
294 */
295 public long getLeastSignificantBits() {
296 return leastSigBits;
297 }
298
299 /**
300 * Returns the most significant 64 bits of this UUID's 128 bit value.
301 *
302 * @return The most significant 64 bits of this UUID's 128 bit value
303 */
304 public long getMostSignificantBits() {
305 return mostSigBits;
306 }
307
308 /**
309 * The version number associated with this {@code UUID}. The version
310 * number describes how this {@code UUID} was generated.
311 *
312 * The version number has the following meaning:
313 * <p><ul>
314 * <li>1 Time-based UUID
315 * <li>2 DCE security UUID
316 * <li>3 Name-based UUID
317 * <li>4 Randomly generated UUID
318 * </ul>
319 *
320 * @return The version number of this {@code UUID}
321 */
322 public int version() {
323 // Version is bits masked by 0x000000000000F000 in MS long
324 return (int)((mostSigBits >> 12) & 0x0f);
325 }
326
327 /**
328 * The variant number associated with this {@code UUID}. The variant
329 * number describes the layout of the {@code UUID}.
330 *
331 * The variant number has the following meaning:
332 * <p><ul>
333 * <li>0 Reserved for NCS backward compatibility
334 * <li>2 <a href="http://www.ietf.org/rfc/rfc4122.txt">IETF RFC 4122</a>
335 * (Leach-Salz), used by this class
336 * <li>6 Reserved, Microsoft Corporation backward compatibility
337 * <li>7 Reserved for future definition
338 * </ul>
339 *
340 * @return The variant number of this {@code UUID}
341 */
342 public int variant() {
343 // This field is composed of a varying number of bits.
344 // 0 - - Reserved for NCS backward compatibility
345 // 1 0 - The IETF aka Leach-Salz variant (used by this class)
346 // 1 1 0 Reserved, Microsoft backward compatibility
347 // 1 1 1 Reserved for future definition.
348 return (int) ((leastSigBits >>> (64 - (leastSigBits >>> 62)))
349 & (leastSigBits >> 63));
350 }
351
352 /**
353 * The timestamp value associated with this UUID.
354 *
355 * <p> The 60 bit timestamp value is constructed from the time_low,
356 * time_mid, and time_hi fields of this {@code UUID}. The resulting
357 * timestamp is measured in 100-nanosecond units since midnight,
358 * October 15, 1582 UTC.
359 *
360 * <p> The timestamp value is only meaningful in a time-based UUID, which
361 * has version type 1. If this {@code UUID} is not a time-based UUID then
362 * this method throws UnsupportedOperationException.
363 *
364 * @throws UnsupportedOperationException
365 * If this UUID is not a version 1 UUID
366 */
367 public long timestamp() {
368 if (version() != 1) {
369 throw new UnsupportedOperationException("Not a time-based UUID");
370 }
371
372 return (mostSigBits & 0x0FFFL) << 48
373 | ((mostSigBits >> 16) & 0x0FFFFL) << 32
374 | mostSigBits >>> 32;
375 }
376
377 /**
378 * The clock sequence value associated with this UUID.
379 *
380 * <p> The 14 bit clock sequence value is constructed from the clock
381 * sequence field of this UUID. The clock sequence field is used to
382 * guarantee temporal uniqueness in a time-based UUID.
383 *
384 * <p> The {@code clockSequence} value is only meaningful in a time-based
385 * UUID, which has version type 1. If this UUID is not a time-based UUID
386 * then this method throws UnsupportedOperationException.
387 *
388 * @return The clock sequence of this {@code UUID}
389 *
390 * @throws UnsupportedOperationException
391 * If this UUID is not a version 1 UUID
392 */
393 public int clockSequence() {
394 if (version() != 1) {
395 throw new UnsupportedOperationException("Not a time-based UUID");
396 }
397
398 return (int)((leastSigBits & 0x3FFF000000000000L) >>> 48);
399 }
400
401 /**
402 * The node value associated with this UUID.
403 *
404 * <p> The 48 bit node value is constructed from the node field of this
405 * UUID. This field is intended to hold the IEEE 802 address of the machine
406 * that generated this UUID to guarantee spatial uniqueness.
407 *
408 * <p> The node value is only meaningful in a time-based UUID, which has
409 * version type 1. If this UUID is not a time-based UUID then this method
410 * throws UnsupportedOperationException.
411 *
412 * @return The node value of this {@code UUID}
413 *
414 * @throws UnsupportedOperationException
415 * If this UUID is not a version 1 UUID
416 */
417 public long node() {
418 if (version() != 1) {
419 throw new UnsupportedOperationException("Not a time-based UUID");
420 }
421
422 return leastSigBits & 0x0000FFFFFFFFFFFFL;
423 }
424
425 // Object Inherited Methods
426
427 /**
428 * Returns a {@code String} object representing this {@code UUID}.
429 *
430 * <p> The UUID string representation is as described by this BNF:
431 * <blockquote><pre>
432 * {@code
433 * UUID = <time_low> "-" <time_mid> "-"
434 * <time_high_and_version> "-"
435 * <variant_and_sequence> "-"
436 * <node>
437 * time_low = 4*<hexOctet>
438 * time_mid = 2*<hexOctet>
439 * time_high_and_version = 2*<hexOctet>
440 * variant_and_sequence = 2*<hexOctet>
441 * node = 6*<hexOctet>
442 * hexOctet = <hexDigit><hexDigit>
443 * hexDigit =
444 * "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
445 * | "a" | "b" | "c" | "d" | "e" | "f"
446 * | "A" | "B" | "C" | "D" | "E" | "F"
447 * }</pre></blockquote>
448 *
449 * @return A string representation of this {@code UUID}
450 */
451 public String toString()
452 {
453 return toString(getMostSignificantBits(), getLeastSignificantBits());
454 }
455
456 /**
457 * Returns a {@code String} object representing a UUID passed in as
458 * two longs. Usually you will use {@link #toString()} instead.
459 * @param msb the most significant bytes
460 * @param lsb the least significant bytes
461 */
462 private static String toString(long msb, long lsb)
463 {
464 char[] uuidChars = new char[36];
465
466 digits(uuidChars, 0, 8, msb >> 32);
467 uuidChars[8] = '-';
468 digits(uuidChars, 9, 4, msb >> 16);
469 uuidChars[13] = '-';
470 digits(uuidChars, 14, 4, msb);
471 uuidChars[18] = '-';
472 digits(uuidChars, 19, 4, lsb >> 48);
473 uuidChars[23] = '-';
474 digits(uuidChars, 24, 12, lsb);
475
476 return JAVA_LANG_ACCESS.createStringSharedChars(uuidChars);
477 }
478
479 private static void digits(char[] dest, int offset, int digits, long val) {
480 long mask = 1L << (digits * 4);
481 JAVA_LANG_ACCESS.formatUnsignedLong(mask | (val & (mask - 1)), 4, dest, offset, digits);
482 }
483
484 /**
485 * Returns a hash code for this {@code UUID}.
486 *
487 * @return A hash code value for this {@code UUID}
488 */
489 public int hashCode() {
490 long hilo = mostSigBits ^ leastSigBits;
491 return ((int)(hilo >> 32)) ^ (int) hilo;
492 }
493
494 /**
495 * Compares this object to the specified object. The result is {@code
496 * true} if and only if the argument is not {@code null}, is a {@code UUID}
497 * object, has the same variant, and contains the same value, bit for bit,
498 * as this {@code UUID}.
499 *
500 * @param obj
501 * The object to be compared
502 *
503 * @return {@code true} if the objects are the same; {@code false}
504 * otherwise
505 */
506 public boolean equals(Object obj) {
507 if ((null == obj) || (obj.getClass() != UUID.class))
508 return false;
509 UUID id = (UUID)obj;
510 return (mostSigBits == id.mostSigBits &&
511 leastSigBits == id.leastSigBits);
512 }
513
514 // Comparison Operations
515
516 /**
517 * Compares this UUID with the specified UUID.
518 *
519 * <p> The first of two UUIDs is greater than the second if the most
520 * significant field in which the UUIDs differ is greater for the first
521 * UUID.
522 *
523 * @param val
524 * {@code UUID} to which this {@code UUID} is to be compared
525 *
526 * @return -1, 0 or 1 as this {@code UUID} is less than, equal to, or
527 * greater than {@code val}
528 *
529 */
530 public int compareTo(UUID val) {
531 // The ordering is intentionally set up so that the UUIDs
532 // can simply be numerically compared as two numbers
533 return (this.mostSigBits < val.mostSigBits ? -1 :
534 (this.mostSigBits > val.mostSigBits ? 1 :
535 (this.leastSigBits < val.leastSigBits ? -1 :
536 (this.leastSigBits > val.leastSigBits ? 1 :
537 0))));
538 }
539 }