KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > org > hsqldb > NumberSequence


1 /* Copyright (c) 2001-2005, The HSQL Development Group
2  * All rights reserved.
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions are met:
6  *
7  * Redistributions of source code must retain the above copyright notice, this
8  * list of conditions and the following disclaimer.
9  *
10  * Redistributions in binary form must reproduce the above copyright notice,
11  * this list of conditions and the following disclaimer in the documentation
12  * and/or other materials provided with the distribution.
13  *
14  * Neither the name of the HSQL Development Group nor the names of its
15  * contributors may be used to endorse or promote products derived from this
16  * software without specific prior written permission.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
19  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21  * ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
22  * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
23  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
24  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
25  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
26  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
28  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29  */
30
31
32 package org.hsqldb;
33
34 import org.hsqldb.HsqlNameManager.HsqlName;
35
36 /**
37  * Maintains a sequence of numbers.
38  *
39  * @author fredt@users
40  * @since 1.7.2
41  * @version 1.7.2
42  */
43 public class NumberSequence {
44
45     HsqlName name;
46
47     // original start value - used in CREATE and ALTER commands
48 private long startValue;
49
50     // present value
51 private long currValue;
52
53     // last value
54 private long lastValue;
55     private long increment;
56     private int dataType;
57
58     /**
59      * constructor with initial value and increment;
60      */
61     public NumberSequence(HsqlName name, long value, long increment,
62                           int type) {
63
64         this.name = name;
65         startValue = currValue = lastValue = value;
66         this.increment = increment;
67         dataType = type;
68     }
69
70     /**
71      * principal getter for the next sequence value
72      */
73     synchronized long getValue() {
74
75         long value = currValue;
76
77         currValue += increment;
78
79         return value;
80     }
81
82     /**
83      * getter for a given value
84      */
85     synchronized long getValue(long value) {
86
87         if (value >= currValue) {
88             currValue = value;
89             currValue += increment;
90
91             return value;
92         } else {
93             return value;
94         }
95     }
96
97     /** @todo fredt - check against max value of type */
98     Object JavaDoc getValueObject() {
99
100         long value = currValue;
101
102         currValue += increment;
103
104         Object JavaDoc result;
105
106         if (dataType == Types.INTEGER) {
107             result = new Integer JavaDoc((int) value);
108         } else {
109             result = new Long JavaDoc(value);
110         }
111
112         return result;
113     }
114
115     /**
116      * reset to start value
117      */
118     void reset() {
119
120         // no change if called before getValue() or called twice
121 lastValue = currValue = startValue;
122     }
123
124     /**
125      * get next value without incrementing
126      */
127     public long peek() {
128         return currValue;
129     }
130
131     /**
132      * true if one or more values were retreived since the last resetWasUsed
133      */
134     boolean wasUsed() {
135         return lastValue != currValue;
136     }
137
138     /**
139      * reset the wasUsed flag
140      */
141     void resetWasUsed() {
142         lastValue = currValue;
143     }
144
145     /**
146      * reset to new initial value
147      */
148     public void reset(long value) {
149         startValue = currValue = lastValue = value;
150     }
151
152     void reset(long value, long increment) {
153
154         reset(value);
155
156         this.increment = increment;
157     }
158
159     int getType() {
160         return dataType;
161     }
162
163     public HsqlName getName() {
164         return name;
165     }
166
167     public String JavaDoc getSchemaName() {
168         return name.schema.name;
169     }
170
171     long getIncrement() {
172         return increment;
173     }
174 }
175
Popular Tags