UUID


1   /* JFox, the OpenSource J2EE Application Server
2    *
3    * Distributable under GNU LGPL license by gun.org
4    * more details please visit http://www.huihoo.org/jfox
5    */
6   
7   package org.jfox.ioc.util;
8   
9   import java.io.UnsupportedEncodingException  ;
10  import java.security.MessageDigest  ;
11  import java.security.NoSuchAlgorithmException  ;
12  import java.security.SecureRandom  ;
13  
14  /**
15   * derived from JDK 1.5
16   * <p/>
17   * A class that represents an immutable universally unique identifier (UUID).
18   * A UUID represents a 128-bit value.
19   * <p/>
20   * <p>There exist different variants of these global identifiers. The methods
21   * of this class are for manipulating the Leach-Salz variant, although the
22   * constructors allow the creation of any variant of UUID (described below).
23   * <p/>
24   * <p>The layout of a variant 2 (Leach-Salz) UUID is as follows:
25   * <p/>
26   * The most significant long consists of the following unsigned fields:
27   * <pre>
28   * 0xFFFFFFFF00000000 time_low
29   * 0x00000000FFFF0000 time_mid
30   * 0x000000000000F000 version
31   * 0x0000000000000FFF time_hi
32   * </pre>
33   * The least significant long consists of the following unsigned fields:
34   * <pre>
35   * 0xC000000000000000 variant
36   * 0x3FFF000000000000 clock_seq
37   * 0x0000FFFFFFFFFFFF node
38   * </pre>
39   * <p/>
40   * <p>The variant field contains a value which identifies the layout of
41   * the <tt>UUID</tt>. The bit layout described above is valid only for
42   * a <tt>UUID</tt> with a variant value of 2, which indicates the
43   * Leach-Salz variant.
44   * <p/>
45   * <p>The version field holds a value that describes the type of this
46   * <tt>UUID</tt>. There are four different basic types of UUIDs: time-based,
47   * DCE security, name-based, and randomly generated UUIDs. These types
48   * have a version value of 1, 2, 3 and 4, respectively.
49   * <p/>
50   * <p>For more information including algorithms used to create <tt>UUID</tt>s,
51   * see the Internet-Draft <a HREF="http://www.ietf.org/internet-drafts/draft-mealling-uuid-urn-01.txt">UUIDs and GUIDs</a>
52   * or the standards body definition at
53   * <a HREF="http://www.iso.ch/cate/d2229.html">ISO/IEC 11578:1996</a>.
54   *
55   * @version 1.10, 03/19/04
56   * @since JDK1.5
57   */
58  public final class UUID implements java.io.Serializable  , Comparable   {
59  
60      /**
61       * Explicit serialVersionUID for interoperability.
62       */
63      private static final long serialVersionUID = -4856846361193249489L;
64  
65      /*
66       * The most significant 64 bits of this UUID.
67       *
68       * @serial
69       */
70      private final long mostSigBits;
71  
72      /*
73       * The least significant 64 bits of this UUID.
74       *
75       * @serial
76       */
77      private final long leastSigBits;
78  
79      /*
80       * The version number associated with this UUID. Computed on demand.
81       */
82      private transient int version = -1;
83  
84      /*
85       * The variant number associated with this UUID. Computed on demand.
86       */
87      private transient int variant = -1;
88  
89      /*
90       * The timestamp associated with this UUID. Computed on demand.
91       */
92      private transient volatile long timestamp = -1;
93  
94      /*
95       * The clock sequence associated with this UUID. Computed on demand.
96       */
97      private transient int sequence = -1;
98  
99      /*
100      * The node number associated with this UUID. Computed on demand.
101      */
102     private transient long node = -1;
103 
104     /*
105      * The hashcode of this UUID. Computed on demand.
106      */
107     private transient int hashCode = -1;
108 
109     /*
110      * The random number generator used by this class to create random
111      * based UUIDs.
112      */
113     private static volatile SecureRandom   numberGenerator = null;
114 
115     // Constructors and Factories
116 
117     /*
118      * Private constructor which uses a byte array to construct the new UUID.
119      */
120     private UUID(byte[] data) {
121         long msb = 0;
122         long lsb = 0;
123         if(data.length != 16) {
124             throw new IllegalArgumentException  ("data length must be 16.");
125         }
126         for(int i = 0; i < 8; i++)
127             msb = (msb << 8) | (data[i] & 0xff);
128         for(int i = 8; i < 16; i++)
129             lsb = (lsb << 8) | (data[i] & 0xff);
130         this.mostSigBits = msb;
131         this.leastSigBits = lsb;
132     }
133 
134     /**
135      * Constructs a new <tt>UUID</tt> using the specified data.
136      * <tt>mostSigBits</tt> is used for the most significant 64 bits
137      * of the <tt>UUID</tt> and <tt>leastSigBits</tt> becomes the
138      * least significant 64 bits of the <tt>UUID</tt>.
139      *
140      * @param mostSigBits
141      * @param leastSigBits
142      */
143     public UUID(long mostSigBits, long leastSigBits) {
144         this.mostSigBits = mostSigBits;
145         this.leastSigBits = leastSigBits;
146     }
147 
148     /**
149      * Static factory to retrieve a type 4 (pseudo randomly generated) UUID.
150      * <p/>
151      * The <code>UUID</code> is generated using a cryptographically strong
152      * pseudo random number generator.
153      *
154      * @return a randomly generated <tt>UUID</tt>.
155      */
156     public static UUID randomUUID() {
157         SecureRandom   ng = numberGenerator;
158         if(ng == null) {
159             numberGenerator = ng = new SecureRandom  ();
160         }
161 
162         byte[] randomBytes = new byte[16];
163         ng.nextBytes(randomBytes);
164         randomBytes[6] &= 0x0f;  /* clear version        */
165         randomBytes[6] |= 0x40;  /* set to version 4     */
166         randomBytes[8] &= 0x3f;  /* clear variant        */
167         randomBytes[8] |= 0x80;  /* set to IETF variant  */
168         return new UUID(randomBytes);
169     }
170 
171     /**
172      * Static factory to retrieve a type 3 (name based) <tt>UUID</tt> based on
173      * the specified String.
174      *
175      * @param name a string to be used to construct a <tt>UUID</tt>.
176      * @return a <tt>UUID</tt> generated from the specified string.
177      */
178     public static UUID nameUUIDFromString(String   name) {
179         MessageDigest   md;
180         try {
181             md = MessageDigest.getInstance("MD5");
182         }
183         catch(NoSuchAlgorithmException   nsae) {
184             throw new InternalError  ("MD5 not supported");
185         }
186         byte[] md5Bytes;
187         try {
188             md5Bytes = md.digest(name.getBytes("8859_1"));
189         }
190         catch(UnsupportedEncodingException   uee) {
191             throw new InternalError  ("8859_1 not supported");
192         }
193         md5Bytes[6] &= 0x0f;  /* clear version        */
194         md5Bytes[6] |= 0x30;  /* set to version 3     */
195         md5Bytes[8] &= 0x3f;  /* clear variant        */
196         md5Bytes[8] |= 0x80;  /* set to IETF variant  */
197         return new UUID(md5Bytes);
198     }
199 
200     /**
201      * Static factory to retrieve a type 3 (name based) <tt>UUID</tt> based on
202      * the specified byte array.
203      *
204      * @param name a byte array to be used to construct a <tt>UUID</tt>.
205      * @return a <tt>UUID</tt> generated from the specified array.
206      */
207     public static UUID nameUUIDFromBytes(byte[] name) {
208         MessageDigest   md;
209         try {
210             md = MessageDigest.getInstance("MD5");
211         }
212         catch(NoSuchAlgorithmException   nsae) {
213             throw new InternalError  ("MD5 not supported");
214         }
215         byte[] md5Bytes = md.digest(name);
216         md5Bytes[6] &= 0x0f;  /* clear version        */
217         md5Bytes[6] |= 0x30;  /* set to version 3     */
218         md5Bytes[8] &= 0x3f;  /* clear variant        */
219         md5Bytes[8] |= 0x80;  /* set to IETF variant  */
220         return new UUID(md5Bytes);
221     }
222 
223     /**
224      * Creates a <tt>UUID</tt> from the string standard representation as
225      * described in the toString() method.
226      *
227      * @param name a string that specifies a <tt>UUID</tt>.
228      * @return a <tt>UUID</tt> with the specified value.
229      */
230     public static UUID fromString(String   name) {
231         String  [] components = name.split("-");
232         if(components.length != 5)
233             throw new IllegalArgumentException  ("Invalid UUID string: " + name);
234         for(int i = 0; i < 5; i++)
235             components[i] = "0x" + components[i];
236 
237         long mostSigBits = Long.decode(components[0]).longValue();
238         mostSigBits <<= 16;
239         mostSigBits |= Long.decode(components[1]).longValue();
240         mostSigBits <<= 16;
241         mostSigBits |= Long.decode(components[2]).longValue();
242 
243         long leastSigBits = Long.decode(components[3]).longValue();
244         leastSigBits <<= 48;
245         leastSigBits |= Long.decode(components[4]).longValue();
246 
247         return new UUID(mostSigBits, leastSigBits);
248     }
249 
250     // Field Accessor Methods
251 
252     /**
253      * Returns the least significant 64 bits of this UUID's 128 bit value.
254      *
255      * @return the least significant 64 bits of this UUID's 128 bit value.
256      */
257     public long getLeastSignificantBits() {
258         return leastSigBits;
259     }
260 
261     /**
262      * Returns the most significant 64 bits of this UUID's 128 bit value.
263      *
264      * @return the most significant 64 bits of this UUID's 128 bit value.
265      */
266     public long getMostSignificantBits() {
267         return mostSigBits;
268     }
269 
270     /**
271      * The version number associated with this <tt>UUID</tt>. The version
272      * number describes how this <tt>UUID</tt> was generated.
273      * <p/>
274      * The version number has the following meaning:<p>
275      * <ul>
276      * <li>1    Time-based UUID
277      * <li>2    DCE security UUID
278      * <li>3    Name-based UUID
279      * <li>4    Randomly generated UUID
280      * </ul>
281      *
282      * @return the version number of this <tt>UUID</tt>.
283      */
284     public int version() {
285         if(version < 0) {
286             // Version is bits masked by 0x000000000000F000 in MS long
287             version = (int) ((mostSigBits >> 12) & 0x0f);
288         }
289         return version;
290     }
291 
292     /**
293      * The variant number associated with this <tt>UUID</tt>. The variant
294      * number describes the layout of the <tt>UUID</tt>.
295      * <p/>
296      * The variant number has the following meaning:<p>
297      * <ul>
298      * <li>0    Reserved for NCS backward compatibility
299      * <li>2    The Leach-Salz variant (used by this class)
300      * <li>6    Reserved, Microsoft Corporation backward compatibility
301      * <li>7    Reserved for future definition
302      * </ul>
303      *
304      * @return the variant number of this <tt>UUID</tt>.
305      */
306     public int variant() {
307         if(variant < 0) {
308             // This field is composed of a varying number of bits
309             if((leastSigBits >>> 63) == 0) {
310                 variant = 0;
311             }
312             else if((leastSigBits >>> 62) == 2) {
313                 variant = 2;
314             }
315             else {
316                 variant = (int) (leastSigBits >>> 61);
317             }
318         }
319         return variant;
320     }
321 
322     /**
323      * The timestamp value associated with this UUID.
324      * <p/>
325      * <p>The 60 bit timestamp value is constructed from the time_low,
326      * time_mid, and time_hi fields of this <tt>UUID</tt>. The resulting
327      * timestamp is measured in 100-nanosecond units since midnight,
328      * October 15, 1582 UTC.<p>
329      * <p/>
330      * The timestamp value is only meaningful in a time-based UUID, which
331      * has version type 1. If this <tt>UUID</tt> is not a time-based UUID then
332      * this method throws UnsupportedOperationException.
333      *
334      * @throws UnsupportedOperationException if this UUID is not a
335      *                                       version 1 UUID.
336      */
337     public long timestamp() {
338         if(version() != 1) {
339             throw new UnsupportedOperationException  ("Not a time-based UUID");
340         }
341         long result = timestamp;
342         if(result < 0) {
343             result = (mostSigBits & 0x0000000000000FFFL) << 48;
344             result |= ((mostSigBits >> 16) & 0xFFFFL) << 32;
345             result |= mostSigBits >>> 32;
346             timestamp = result;
347         }
348         return result;
349     }
350 
351     /**
352      * The clock sequence value associated with this UUID.
353      * <p/>
354      * <p>The 14 bit clock sequence value is constructed from the clock
355      * sequence field of this UUID. The clock sequence field is used to
356      * guarantee temporal uniqueness in a time-based UUID.<p>
357      * <p/>
358      * The  clockSequence value is only meaningful in a time-based UUID, which
359      * has version type 1. If this UUID is not a time-based UUID then
360      * this method throws UnsupportedOperationException.
361      *
362      * @return the clock sequence of this <tt>UUID</tt>.
363      * @throws UnsupportedOperationException if this UUID is not a
364      *                                       version 1 UUID.
365      */
366     public int clockSequence() {
367         if(version() != 1) {
368             throw new UnsupportedOperationException  ("Not a time-based UUID");
369         }
370         if(sequence < 0) {
371             sequence = (int) ((leastSigBits & 0x3FFF000000000000L) >>> 48);
372         }
373         return sequence;
374     }
375 
376     /**
377      * The node value associated with this UUID.
378      * <p/>
379      * <p>The 48 bit node value is constructed from the node field of
380      * this UUID. This field is intended to hold the IEEE 802 address
381      * of the machine that generated this UUID to guarantee spatial
382      * uniqueness.<p>
383      * <p/>
384      * The node value is only meaningful in a time-based UUID, which
385      * has version type 1. If this UUID is not a time-based UUID then
386      * this method throws UnsupportedOperationException.
387      *
388      * @return the node value of this <tt>UUID</tt>.
389      * @throws UnsupportedOperationException if this UUID is not a
390      *                                       version 1 UUID.
391      */
392     public long node() {
393         if(version() != 1) {
394             throw new UnsupportedOperationException  ("Not a time-based UUID");
395         }
396         if(node < 0) {
397             node = leastSigBits & 0x0000FFFFFFFFFFFFL;
398         }
399         return node;
400     }
401 
402     // Object Inherited Methods
403 
404     /**
405      * Returns a <code>String</code> object representing this
406      * <code>UUID</code>.
407      * <p/>
408      * <p>The UUID string representation is as described by this BNF :
409      * <pre>
410      *  UUID                   = <time_low> "-" <time_mid> "-"
411      *                           <time_high_and_version> "-"
412      *                           <variant_and_sequence> "-"
413      *                           <node>
414      *  time_low               = 4*<hexOctet>
415      *  time_mid               = 2*<hexOctet>
416      *  time_high_and_version  = 2*<hexOctet>
417      *  variant_and_sequence   = 2*<hexOctet>
418      *  node                   = 6*<hexOctet>
419      *  hexOctet               = <hexDigit><hexDigit>
420      *  hexDigit               =
421      *        "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
422      *        | "a" | "b" | "c" | "d" | "e" | "f"
423      *        | "A" | "B" | "C" | "D" | "E" | "F"
424      * </pre>
425      *
426      * @return a string representation of this <tt>UUID</tt>.
427      */
428     public String   toString() {
429         return (digits(mostSigBits >> 32, 8) + "-" +
430                 digits(mostSigBits >> 16, 4) + "-" +
431                 digits(mostSigBits, 4) + "-" +
432                 digits(leastSigBits >> 48, 4) + "-" +
433                 digits(leastSigBits, 12));
434     }
435 
436     /**
437      * Returns val represented by the specified number of hex digits.
438      */
439     private static String   digits(long val, int digits) {
440         long hi = 1L << (digits * 4);
441         return Long.toHexString(hi | (val & (hi - 1))).substring(1);
442     }
443 
444     /**
445      * Returns a hash code for this <code>UUID</code>.
446      *
447      * @return a hash code value for this <tt>UUID</tt>.
448      */
449     public int hashCode() {
450         if(hashCode == -1) {
451             hashCode = (int) ((mostSigBits >> 32) ^
452                     mostSigBits ^
453                     (leastSigBits >> 32) ^
454                     leastSigBits);
455         }
456         return hashCode;
457     }
458 
459     /**
460      * Compares this object to the specified object.  The result is
461      * <tt>true</tt> if and only if the argument is not
462      * <tt>null</tt>, is a <tt>UUID</tt> object, has the same variant,
463      * and contains the same value, bit for bit, as this <tt>UUID</tt>.
464      *
465      * @param obj the object to compare with.
466      * @return <code>true</code> if the objects are the same;
467      *         <code>false</code> otherwise.
468      */
469     public boolean equals(Object   obj) {
470         if(!(obj instanceof UUID))
471             return false;
472         if(((UUID) obj).variant() != this.variant())
473             return false;
474         UUID id = (UUID) obj;
475         return (mostSigBits == id.mostSigBits &&
476                 leastSigBits == id.leastSigBits);
477     }
478 
479     // Comparison Operations
480 
481     /**
482      * Compares this UUID with the specified UUID.
483      * <p/>
484      * <p>The first of two UUIDs follows the second if the most significant
485      * field in which the UUIDs differ is greater for the first UUID.
486      *
487      * @param val <tt>UUID</tt> to which this <tt>UUID</tt> is to be compared.
488      * @return -1, 0 or 1 as this <tt>UUID</tt> is less than, equal
489      *         to, or greater than <tt>val</tt>.
490      */
491     public int compareTo(Object   val) {
492         if(val.getClass() != UUID.class) {
493             return -1;
494         }
495         // The ordering is intentionally set up so that the UUIDs
496         // can simply be numerically compared as two numbers
497         return (this.mostSigBits < ((UUID) val).mostSigBits ? -1 :
498                 (this.mostSigBits > ((UUID) val).mostSigBits ? 1 :
499                 (this.leastSigBits < ((UUID) val).leastSigBits ? -1 :
500                 (this.leastSigBits > ((UUID) val).leastSigBits ? 1 :
501                 0))));
502     }
503 
504     /**
505      * Reconstitute the <tt>UUID</tt> instance from a stream (that is,
506      * deserialize it). This is necessary to set the transient fields
507      * to their correct uninitialized value so they will be recomputed
508      * on demand.
509      */
510     private void readObject(java.io.ObjectInputStream   in)
511             throws java.io.IOException  , ClassNotFoundException   {
512 
513         in.defaultReadObject();
514 
515         // Set "cached computation" fields to their initial values
516         version = -1;
517         variant = -1;
518         timestamp = -1;
519         sequence = -1;
520         node = -1;
521         hashCode = -1;
522     }
523 }
524
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