001 //$HeadURL: svn+ssh://rbezema@svn.wald.intevation.org/deegree/base/branches/2.2_testing/src/org/deegree/framework/util/BasicUUIDFactory.java $
002 /*
003 *
004 This class orginaly has been part of the apache derby project. It has
005 slightly been changed to match the requirements of deegree.
006
007 Derby - Class org.apache.derby.impl.services.uuid.BasicUUIDFactory
008
009 Copyright 1997, 2004 The Apache Software Foundation or its licensors, as applicable.
010
011 Licensed under the Apache License, Version 2.0 (the "License");
012 you may not use this file except in compliance with the License.
013 You may obtain a copy of the License at
014
015 http://www.apache.org/licenses/LICENSE-2.0
016
017 Unless required by applicable law or agreed to in writing, software
018 distributed under the License is distributed on an "AS IS" BASIS,
019 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
020 See the License for the specific language governing permissions and
021 limitations under the License.
022
023 */
024 package org.deegree.framework.util;
025
026 /**
027 *
028 * A hack implementation of something similar to a DCE UUID generator. Generates unique 128-bit
029 * numbers based on the current machine's internet address, the current time, and a sequence number.
030 * This implementation should be made to conform to the DCE specification. ("DEC/HP, Network
031 * Computing Architecture, Remote Procedure Call Runtime Extensions Specification, version OSF
032 * TX1.0.11," Steven Miller, July 23, 1992. This is part of the OSF DCE Documentation. Chapter 10
033 * describes the UUID generation algorithm.)
034 * <P>
035 * Some known deficiencies:
036 * <ul>
037 * <li> Rather than using the 48-bit hardware network address, it uses the 32-bit IP address. IP
038 * addresses are not guaranteed to be unique.
039 * <li> There is no provision for generating a suitably unique number if no IP address is available.
040 * <li> Two processes running on this machine which start their respective UUID services within a
041 * millisecond of one another may generate duplicate UUIDS.
042 * </ul>
043 * <P>
044 * However, the intention is that UUIDs generated from this class will be unique with respect to
045 * UUIDs generated by other DCE UUID generators.
046 *
047 * @deprecated use
048 * @see UUID
049 *
050 */
051
052 public final class BasicUUIDFactory {
053 /*
054 * * Fields of BasicUUIDFactory.
055 */
056
057 private long majorId; // 48 bits only
058
059 private long timemillis;
060
061 public BasicUUIDFactory() {
062
063 majorId = Runtime.getRuntime().freeMemory();
064
065 majorId &= 0x0000ffffffffffffL;
066 resetCounters();
067 }
068
069 public BasicUUIDFactory( long majorId ) {
070
071 this.majorId = majorId;
072
073 this.majorId &= 0x0000ffffffffffffL;
074 resetCounters();
075 }
076
077 //
078 // Constants and fields for computing the sequence number. We started out with monotonically
079 // increasing sequence numbers but realized that this causes collisions at the
080 // ends of BTREEs built on UUID columns. So now we have a random number
081 // generator. We generate these numbers using a technique from Knuth
082 // "Seminumerical Algorithms," section 3.2 (Generating Uniform Random Numbers).
083 // The formula is:
084 //
085 // next = ( (MULTIPLIER * current) + STEP ) % MODULUS
086 //
087 // Here
088 //
089 // MODULUS = int size.
090 // MULTIPLIER = fairly close to the square root of MODULUS to force the
091 // sequence number to jump around. satisifies the rule that
092 // (MULTIPLIER-1) is divisible by 4 and by all the primes which
093 // divide MODULUS.
094 // STEP = a large number that keeps the sequence number jumping around.
095 // must be relatively prime to MODULUS.
096 // INITIAL_VALUE = a number guaranteeing that the first couple sequence numbers
097 // won't be monotonically increasing.
098 //
099 // The sequence numbers should jump around and cycle through all numbers which fit in an int.
100
101 private static final long MODULUS = ( 1L << 32 );
102
103 private static final long MULTIPLIER = ( ( 1L << 14 ) + 1 );
104
105 private static final long STEP = ( ( 1L << 27 ) + 1 );
106
107 private static final long INITIAL_VALUE = ( 2551218188L );
108
109 private long currentValue;
110
111 /*
112 * * Methods of UUID
113 */
114
115 /**
116 * Generate a new UUID.
117 *
118 * @see UUIDFactory#createUUID
119 */
120 public synchronized UUID createUUID() {
121 long cv = currentValue = ( ( MULTIPLIER * currentValue ) + STEP ) % MODULUS;
122 if ( cv == INITIAL_VALUE ) {
123 bumpMajor();
124 }
125 int sequence = (int) cv;
126
127 return new BasicUUID( majorId, timemillis, sequence );
128 }
129
130 /**
131 * Recreate a UUID previously generated UUID value.
132 *
133 * @see UUIDFactory#recreateUUID
134 */
135 public UUID recreateUUID( String uuidstring ) {
136 return new BasicUUID( uuidstring );
137 }
138
139 /**
140 * @see UUIDFactory#recreateUUID
141 */
142 public UUID recreateUUID( byte[] b ) {
143 return new BasicUUID( b );
144 }
145
146 private void bumpMajor() {
147
148 // 48 bits only
149 majorId = ( majorId + 1L ) & 0x0000ffffffffffffL;
150 if ( majorId == 0L )
151 resetCounters();
152
153 }
154
155 private void resetCounters() {
156 timemillis = System.currentTimeMillis();
157 currentValue = INITIAL_VALUE;
158 }
159 }