1 /* ============================================================
2 * JRobin : Pure java implementation of RRDTool's functionality
3 * ============================================================
4 *
5 * Project Info: http://www.jrobin.org
6 * Project Lead: Sasa Markovic (saxon@jrobin.org);
7 *
8 * (C) Copyright 2003-2005, by Sasa Markovic.
9 *
10 * Developers: Sasa Markovic (saxon@jrobin.org)
11 *
12 *
13 * This library is free software; you can redistribute it and/or modify it under the terms
14 * of the GNU Lesser General Public License as published by the Free Software Foundation;
15 * either version 2.1 of the License, or (at your option) any later version.
16 *
17 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
18 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
19 * See the GNU Lesser General Public License for more details.
20 *
21 * You should have received a copy of the GNU Lesser General Public License along with this
22 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
23 * Boston, MA 02111-1307, USA.
24 */
25
26 package org.jrobin.core;
27
28 import java.io.IOException;
29 import java.util.HashMap;
30
31 /**
32 * Factory class which creates actual {@link RrdMemoryBackend} objects. JRobin's support
33 * for in-memory RRDs is still experimental. You should know that all active RrdMemoryBackend
34 * objects are held in memory, each backend object stores RRD data in one big byte array. This
35 * implementation is therefore quite basic and memory hungry but runs very fast.<p>
36 * <p/>
37 * Calling {@link RrdDb#close() close()} on RrdDb objects does not release any memory at all
38 * (RRD data must be available for the next <code>new RrdDb(path)</code> call. To release allocated
39 * memory, you'll have to call {@link #delete(String) delete(path)} method of this class.<p>
40 */
41 public class RrdMemoryBackendFactory extends RrdBackendFactory {
42 /**
43 * factory name, "MEMORY"
44 */
45 public static final String NAME = "MEMORY";
46 private HashMap<String, RrdMemoryBackend> backends = new HashMap<String, RrdMemoryBackend>();
47
48 /**
49 * Creates RrdMemoryBackend object.
50 *
51 * @param id Since this backend holds all data in memory, this argument is interpreted
52 * as an ID for this memory-based storage.
53 * @param readOnly This parameter is ignored
54 * @return RrdMemoryBackend object which handles all I/O operations
55 * @throws IOException Thrown in case of I/O error.
56 */
57 protected synchronized RrdBackend open(String id, boolean readOnly)
58 throws IOException {
59 RrdMemoryBackend backend;
60 if (backends.containsKey(id)) {
61 backend = backends.get(id);
62 }
63 else {
64 backend = new RrdMemoryBackend(id);
65 backends.put(id, backend);
66 }
67 return backend;
68 }
69
70 /**
71 * Method to determine if a memory storage with the given ID already exists.
72 *
73 * @param id Memory storage ID.
74 * @return True, if such storage exists, false otherwise.
75 */
76 protected synchronized boolean exists(String id) {
77 return backends.containsKey(id);
78 }
79
80 /**
81 * Removes the storage with the given ID from the memory.
82 *
83 * @param id Storage ID
84 * @return True, if the storage with the given ID is deleted, false otherwise.
85 */
86 public boolean delete(String id) {
87 if (backends.containsKey(id)) {
88 backends.remove(id);
89 return true;
90 }
91 else {
92 return false;
93 }
94 }
95
96 /**
97 * Returns the name of this factory.
98 *
99 * @return Factory name (equals to "MEMORY").
100 */
101 public String getFactoryName() {
102 return NAME;
103 }
104 }
105