libjava/java/rmi/server/UID.java

   1 /* UID.java --
   2    Copyright (c) 1996, 1997, 1998, 1999, 2004 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package java.rmi.server;
  40
  41 import java.io.DataInput;
  42 import java.io.DataOutput;
  43 import java.io.IOException;
  44 import java.io.Serializable;
  45
  46 public final class UID implements Serializable
  47 {
  48 private static final long serialVersionUID = 1086053664494604050L;
  49
  50 private static final Object lock = UID.class;
  51 private static long baseTime = System.currentTimeMillis();
  52 private static short nextCount = Short.MIN_VALUE;
  53 // This is sun's algorithm - don't ask me why ...
  54 private static final int uniqueNr = (new Object()).hashCode();
  55
  56 private int unique;
  57 private long time;
  58 private short count;
  59
  60 /**
  61  * This is sun's algorithm - don't ask me why ...
  62  */
  63 public UID() {
  64         synchronized (lock) {
  65                 if (nextCount == Short.MAX_VALUE) {
  66                         long newtime;
  67                         for (;;) {
  68                                 newtime = System.currentTimeMillis();
  69                                 if (newtime - baseTime > 1000) {
  70                                         break;
  71                                 }
  72                                 try {
  73                                         Thread.sleep(1000);
  74                                 }
  75                                 catch (InterruptedException _) {
  76                                 }
  77                         }
  78                         baseTime = newtime;
  79                         nextCount = Short.MIN_VALUE;
  80                 }
  81                 count = nextCount++;
  82                 unique = uniqueNr;
  83                 time = baseTime;
  84         }
  85 }
  86
  87 public UID(short num) {
  88         unique = (int)num;
  89         time = 0;
  90         count = 0;
  91 }
  92
  93 public int hashCode() {
  94         return (unique);
  95 }
  96
  97 public boolean equals(Object obj) {
  98         if (obj instanceof UID) {
  99                 UID uid = (UID)obj;
 100                 if (this.unique == uid.unique &&
 101                     this.time == uid.time &&
 102                     this.count == uid.count) {
 103                         return (true);
 104                 }
 105         }
 106         return (false);
 107 }
 108
 109 public String toString() {
 110         return ("[UID: " + unique + "," + time + "," + count + "]");
 111 }
 112
 113 public void write(DataOutput out) throws IOException {
 114         out.writeInt(unique);
 115         out.writeLong(time);
 116         out.writeShort(count);
 117 }
 118
 119 public static UID read(DataInput in) throws IOException {
 120         UID id = new UID();
 121         id.unique = in.readInt();
 122         id.time = in.readLong();
 123         id.count = in.readShort();
 124         return (id);
 125 }
 126
 127 }