Storage


1   // You can redistribute this software and/or modify it under the terms of
2   // the Ozone Core License version 1 published by ozone-db.org.
3   //
4   // The original code and portions created by SMB are
5   // Copyright (C) 1997-@year@, Leo Mekenkamp. All rights reserved.
6   //
7   // $Id: Storage.java,v 1.1 2004/01/02 09:24:38 leomekenkamp Exp $
8   
9   package org.ozoneDB.core.storage.gammaStore;
10  
11  import java.io.IOException  ;
12  
13  /**
14   * <p>A meganism for storing and retrieving data to a permament back-end.
15   * While implementing classes are typically backed by file-based structures,
16   * this is in no way a _must_. Inheriting classes must must simply support
17   * read/write actions from a 'random' location.</p>
18   * <p>As the <code>IndexManager</code> also uses instances of this type to
19   * write index nodes as a whole (no seek needed) there are also implementations
20   * that not support seek functionality.</p>
21   *
22   * @author <a HREF="mailto:ozoneATmekenkampD0Tcom">Leo Mekenkamp (mind the anti-sp@m)</a>
23   */
24  public interface Storage {
25      
26      /**
27       * <p>Introduced because some implementing classes (based on <code>FileOutputStream</code>
28       * and <code>FileInputStream</code> for instance) might not support seek
29       * operations. They may throw an <code>UnsupportedOperationException</code>
30       * here, but still support writing and reading.</p>
31       * <p>Implementations of this interface are used in 2 different ways: the
32       * <code>IndexManager</code> does not perform any seek actions, and thus the
33       * storage implementation it uses can include stream based ones; the 
34       * <code>ClusterManager</code> however does perform seek actions and thus
35       * cannot have a storage implementation with streams in it.</p>
36       *
37       * @throws UnsupportedOperationException
38       */
39      public void seek(long pos) throws IOException  ;
40      
41      /**
42       * Write <code>lenght</code> bytes from <code>b</code>, starting at <code>
43       * offset</code>.
44       */
45      public void write(byte[] b, int offset, int length) throws IOException  ;
46  
47      public void write(byte[] b) throws IOException  ;
48  
49      public void writeLong(long value) throws IOException  ;
50      
51      public void writeInt(int value) throws IOException  ;
52      
53      /**
54       * Read <code>lenght</code> bytes from <code>b</code>, starting at <code>
55       * offset</code>.
56       */
57      public void readFully(byte[] b, int offset, int length) throws IOException  ;
58  
59      public void readFully(byte[] b) throws IOException  ;
60      
61      public long readLong() throws IOException  ;
62  
63      public int readInt() throws IOException  ;
64  
65      /**
66       * Sets the maximum length.
67       */
68      public void setLength(long length) throws IOException  ;
69      
70      public void close() throws IOException  ;
71      
72      public long length() throws IOException  ;
73  
74  }
75
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