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1   /**
2    * JDBM LICENSE v1.00
3    *
4    * Redistribution and use of this software and associated documentation
5    * ("Software"), with or without modification, are permitted provided
6    * that the following conditions are met:
7    *
8    * 1. Redistributions of source code must retain copyright
9    *    statements and notices.  Redistributions must also contain a
10   *    copy of this document.
11   *
12   * 2. Redistributions in binary form must reproduce the
13   *    above copyright notice, this list of conditions and the
14   *    following disclaimer in the documentation and/or other
15   *    materials provided with the distribution.
16   *
17   * 3. The name "JDBM" must not be used to endorse or promote
18   *    products derived from this Software without prior written
19   *    permission of Cees de Groot.  For written permission,
20   *    please contact cg@cdegroot.com.
21   *
22   * 4. Products derived from this Software may not be called "JDBM"
23   *    nor may "JDBM" appear in their names without prior written
24   *    permission of Cees de Groot. 
25   *
26   * 5. Due credit should be given to the JDBM Project
27   *    (http://jdbm.sourceforge.net/).
28   *
29   * THIS SOFTWARE IS PROVIDED BY THE JDBM PROJECT AND CONTRIBUTORS
30   * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
31   * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
32   * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
33   * CEES DE GROOT OR ANY CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
34   * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
35   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
36   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
37   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
38   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
39   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
40   * OF THE POSSIBILITY OF SUCH DAMAGE.
41   *
42   * Copyright 2000 (C) Cees de Groot. All Rights Reserved.
43   * Contributions are Copyright (C) 2000 by their associated contributors.
44   *
45   * $Id: Location.java,v 1.2 2003/11/01 14:17:21 dranatunga Exp $
46   */
47  
48  package jdbm.recman;
49  
50  /**
51   * This class represents a location within a file. Both physical and
52   * logical rowids are based on locations internally - this version is
53   * used when there is no file block to back the location's data.
54   */
55  final class Location {
56      private long block;
57      private short offset;
58  
59      /**
60       * Creates a location from a (block, offset) tuple.
61       */
62      Location(long block, short offset) {
63          this.block = block;
64          this.offset = offset;
65      }
66  
67      /**
68       * Creates a location from a combined block/offset long, as
69       * used in the external representation of logical rowids.
70       * 
71       * @see #toLong()
72       */
73      Location(long blockOffset) {
74          this.offset = (short) (blockOffset & 0xffff);
75          this.block = blockOffset >> 16;
76      }
77  
78      /**
79       * Creates a location based on the data of the physical rowid.
80       */
81      Location(PhysicalRowId src) {
82          block = src.getBlock();
83          offset = src.getOffset();
84      }
85  
86      /**
87       * Returns the file block of the location
88       */
89      long getBlock() {
90          return block;
91      }
92  
93      /**
94       * Returns the offset within the block of the location
95       */
96      short getOffset() {
97          return offset;
98      }
99  
100     /**
101      * Returns the external representation of a location when used
102      * as a logical rowid, which combines the block and the offset
103      * in a single long.
104      */
105     long toLong() {
106         return (block << 16) + (long) offset;
107     }
108 
109     // overrides of java.lang.Object
110 
111     public boolean equals(Object o) {
112         if (o == null || !(o instanceof Location))
113             return false;
114         Location ol = (Location) o;
115         return ol.block == block && ol.offset == offset;
116     }
117 
118     public String toString() {
119         return "PL(" + block + ":" + offset + ")";
120     }
121 }