01: /**
02: * com.mckoi.store.StoreDataAccessor 10 Jun 2003
03: *
04: * Mckoi SQL Database ( http://www.mckoi.com/database )
05: * Copyright (C) 2000, 2001, 2002 Diehl and Associates, Inc.
06: *
07: * This program is free software; you can redistribute it and/or
08: * modify it under the terms of the GNU General Public License
09: * Version 2 as published by the Free Software Foundation.
10: *
11: * This program is distributed in the hope that it will be useful,
12: * but WITHOUT ANY WARRANTY; without even the implied warranty of
13: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14: * GNU General Public License Version 2 for more details.
15: *
16: * You should have received a copy of the GNU General Public License
17: * Version 2 along with this program; if not, write to the Free Software
18: * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
19: *
20: * Change Log:
21: *
22: *
23: */package com.mckoi.store;
24:
25: import java.io.IOException;
26:
27: /**
28: * An interface for low level store data access methods. This is used to
29: * implement a variety of ways of accessing data from some resource, such as
30: * a file in a filesystem. For example, we might use this to access a file
31: * using the NIO API, or through the IO API. Alternatively we may use it to
32: * implement a scattering store that includes data across multiple files in the
33: * filesystem.
34: *
35: * @author Tobias Downer
36: */
37:
38: interface StoreDataAccessor {
39:
40: /**
41: * Returns true if the resource exists.
42: */
43: boolean exists();
44:
45: /**
46: * Deletes the data area resource. Returns true if the delete was successful.
47: */
48: boolean delete();
49:
50: /**
51: * Opens the underlying data area representation. If the resource doesn't
52: * exist then it is created and the size is set to 0.
53: */
54: void open(boolean read_only) throws IOException;
55:
56: /**
57: * Closes the underlying data area representation.
58: */
59: void close() throws IOException;
60:
61: /**
62: * Reads a block of data from the underlying data area at the given position
63: * into the byte array at the given offset.
64: */
65: void read(long position, byte[] buf, int off, int len)
66: throws IOException;
67:
68: /**
69: * Writes a block of data to the underlying data area from the byte array at
70: * the given offset.
71: */
72: void write(long position, byte[] buf, int off, int len)
73: throws IOException;
74:
75: /**
76: * Sets the size of the underlying data area to the given size. If the size
77: * of the data area is increased, the content between the old size and the
78: * new size is implementation defined.
79: */
80: void setSize(long new_size) throws IOException;
81:
82: /**
83: * Returns the current size of the underlying data area.
84: */
85: long getSize() throws IOException;
86:
87: /**
88: * Synchronizes the data area by forcing any data out of the OS buffers onto
89: * the disk.
90: */
91: void synch() throws IOException;
92:
93: }
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