001 /* ============================================================
002 * JRobin : Pure java implementation of RRDTool's functionality
003 * ============================================================
004 *
005 * Project Info: http://www.jrobin.org
006 * Project Lead: Sasa Markovic (saxon@jrobin.org);
007 *
008 * (C) Copyright 2003-2005, by Sasa Markovic.
009 *
010 * Developers: Sasa Markovic (saxon@jrobin.org)
011 *
012 *
013 * This library is free software; you can redistribute it and/or modify it under the terms
014 * of the GNU Lesser General Public License as published by the Free Software Foundation;
015 * either version 2.1 of the License, or (at your option) any later version.
016 *
017 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
018 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
019 * See the GNU Lesser General Public License for more details.
020 *
021 * You should have received a copy of the GNU Lesser General Public License along with this
022 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
023 * Boston, MA 02111-1307, USA.
024 */
025
026 package org.jrobin.core;
027
028 import java.io.IOException;
029
030 /**
031 * Backend to be used to store all RRD bytes in memory.<p>
032 */
033 public class RrdMemoryBackend extends RrdBackend {
034 private byte[] buffer = new byte[0];
035
036 protected RrdMemoryBackend(String path) {
037 super(path);
038 }
039
040 protected synchronized void write(long offset, byte[] b) throws IOException {
041 int pos = (int) offset;
042 for (byte singleByte : b) {
043 buffer[pos++] = singleByte;
044 }
045 }
046
047 protected synchronized void read(long offset, byte[] b) throws IOException {
048 int pos = (int) offset;
049 if (pos + b.length <= buffer.length) {
050 for (int i = 0; i < b.length; i++) {
051 b[i] = buffer[pos++];
052 }
053 }
054 else {
055 throw new IOException("Not enough bytes available in memory " + getPath());
056 }
057 }
058
059 /**
060 * Returns the number of RRD bytes held in memory.
061 *
062 * @return Number of all RRD bytes.
063 */
064 public long getLength() {
065 return buffer.length;
066 }
067
068 /**
069 * Reserves a memory section as a RRD storage.
070 *
071 * @param newLength Number of bytes held in memory.
072 * @throws IOException Thrown in case of I/O error.
073 */
074 protected void setLength(long newLength) throws IOException {
075 if (newLength > Integer.MAX_VALUE) {
076 throw new IOException("Cannot create this big memory backed RRD");
077 }
078 buffer = new byte[(int) newLength];
079 }
080
081 /**
082 * This method is required by the base class definition, but it does not
083 * releases any memory resources at all.
084 */
085 public void close() {
086 // NOP
087 }
088
089 /**
090 * This method is overriden to disable high-level caching in frontend JRobin classes.
091 *
092 * @return Always returns <code>false</code>. There is no need to cache anything in high-level classes
093 * since all RRD bytes are already in memory.
094 */
095 protected boolean isCachingAllowed() {
096 return false;
097 }
098 }