RandomAccess


1   package com.quadcap.sql.file;
2   
3   /* Copyright 1997 - 2003 Quadcap Software.  All rights reserved.
4    *
5    * This software is distributed under the Quadcap Free Software License.
6    * This software may be used or modified for any purpose, personal or
7    * commercial.  Open Source redistributions are permitted.  Commercial
8    * redistribution of larger works derived from, or works which bundle
9    * this software requires a "Commercial Redistribution License"; see
10   * http://www.quadcap.com/purchase.
11   *
12   * Redistributions qualify as "Open Source" under  one of the following terms:
13   *   
14   *    Redistributions are made at no charge beyond the reasonable cost of
15   *    materials and delivery.
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17   *    Redistributions are accompanied by a copy of the Source Code or by an
18   *    irrevocable offer to provide a copy of the Source Code for up to three
19   *    years at the cost of materials and delivery.  Such redistributions
20   *    must allow further use, modification, and redistribution of the Source
21   *    Code under substantially the same terms as this license.
22   *
23   * Redistributions of source code must retain the copyright notices as they
24   * appear in each source code file, these license terms, and the
25   * disclaimer/limitation of liability set forth as paragraph 6 below.
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27   * Redistributions in binary form must reproduce this Copyright Notice,
28   * these license terms, and the disclaimer/limitation of liability set
29   * forth as paragraph 6 below, in the documentation and/or other materials
30   * provided with the distribution.
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32   * The Software is provided on an "AS IS" basis.  No warranty is
33   * provided that the Software is free of defects, or fit for a
34   * particular purpose.  
35   *
36   * Limitation of Liability. Quadcap Software shall not be liable
37   * for any damages suffered by the Licensee or any third party resulting
38   * from use of the Software.
39   */
40  
41  import java.io.IOException  ;
42  
43  /**
44   * This interface is used to access a region of consecutive bytes in a
45   * random access manner.<p>
46   *
47   * @author Stan Bailes
48   */
49  
50  public abstract class RandomAccess {
51      byte[]              fmtBuf = new  byte[8];
52      /**
53       * Return the size of the managed region.
54       */
55      public abstract long size();
56  
57      /**
58       * Resize the managed region.
59       */
60      public abstract void resize(long newSize) throws IOException  ;
61  
62      /* Write <tt>len</tt> bytes from position <tt>offset</tt> in buffer
63       * <tt>buf</tt> to position <tt>pos</tt> bytes into the managed
64       * area.
65       */
66      public abstract void write(long pos, byte[] buf, int offset, int len)
67      throws IOException  ;
68  
69      /**
70       * Read <tt>len</tt> bytes from location <tt>pos</tt> of the region
71       * into the buffer <tt>buf</tt>, starting at <tt>offset</tt>.
72       */
73      public abstract void read(long pos, byte[] buf, int offset, int len)
74      throws IOException  ;
75  
76      /**
77       * Finalization...
78       */
79      public abstract void close() throws IOException  ;
80  
81      public abstract void flush() throws IOException  ;
82  
83      public void writeByte(int pos, int val) throws IOException   {
84          synchronized (fmtBuf) {
85              fmtBuf[0] = (byte)(val & 0xff);
86              write(pos, fmtBuf, 0, 1);
87          }
88      }
89  
90      public int readByte(int pos) throws IOException   {
91          synchronized (fmtBuf) {
92              read(pos, fmtBuf, 0, 1);
93              return fmtBuf[0] & 0xff;
94          }
95      }
96  
97      /**
98       * Write a integer value to the specified position in the buffer
99       */
100     public void writeInt(long pos, int val) throws IOException   {
101         synchronized (fmtBuf) {
102             ByteUtil.putInt(fmtBuf, 0, val);
103             write(pos, fmtBuf, 0, 4);
104         }
105     }
106 
107     /**
108      * Write a integer value to the specified position in the buffer
109      */
110     public int readInt(long pos) throws IOException   {
111         synchronized (fmtBuf) {        
112             read(pos, fmtBuf, 0, 4);
113             return ByteUtil.getInt(fmtBuf, 0);
114         }
115     }
116 
117     /**
118      * Write a long value to the specified position in the buffer
119      */
120     public void writeLong(long pos, long val) throws IOException   {
121         synchronized (fmtBuf) {
122             ByteUtil.putLong(fmtBuf, 0, val);
123             write(pos, fmtBuf, 0, 8);
124         }
125     }
126 
127     /**
128      * Write a long value to the specified position in the buffer
129      */
130     public long readLong(long pos) throws IOException   {
131         synchronized (fmtBuf) {
132             read(pos, fmtBuf, 0, 8);
133             return ByteUtil.getLong(fmtBuf, 0);
134         }
135     }
136 }
137
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