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Java > Open Source Codes > org > jrobin > core > jrrd > RRDFile


1 /*
2  * Copyright (C) 2001 Ciaran Treanor <ciaran@codeloop.com>
3  *
4  * Distributable under GPL license.
5  * See terms of license at gnu.org.
6  *
7  * $Id: RRDFile.java,v 1.1 2004/07/22 09:34:10 saxon64 Exp $
8  */
9 package org.jrobin.core.jrrd;
10
11 import java.io.*;
12
13 /**
14  * This class is a quick hack to read information from an RRD file. Writing
15  * to RRD files is not currently supported. As I said, this is a quick hack.
16  * Some thought should be put into the overall design of the file IO.
17  * <p/>
18  * Currently this can read RRD files that were generated on Solaris (Sparc)
19  * and Linux (x86).
20  *
21  * @author <a HREF="mailto:ciaran@codeloop.com">Ciaran Treanor</a>
22  * @version $Revision: 1.1 $
23  */
24 public class RRDFile implements Constants {
25
26     boolean bigEndian;
27     int alignment;
28     RandomAccessFile ras;
29     byte[] buffer;
30
31     RRDFile(String JavaDoc name) throws IOException {
32         this(new File(name));
33     }
34
35     RRDFile(File file) throws IOException {
36
37         ras = new RandomAccessFile(file, "r");
38         buffer = new byte[128];
39
40         initDataLayout(file);
41     }
42
43     private void initDataLayout(File file) throws IOException {
44
45         if (file.exists()) { // Load the data formats from the file
46 ras.read(buffer, 0, 24);
47
48             int index;
49
50             if ((index = indexOf(FLOAT_COOKIE_BIG_ENDIAN, buffer)) != -1) {
51                 bigEndian = true;
52             } else if ((index = indexOf(FLOAT_COOKIE_LITTLE_ENDIAN, buffer))
53                     != -1) {
54                 bigEndian = false;
55             } else {
56                 throw new IOException("Invalid RRD file");
57             }
58
59             switch (index) {
60
61                 case 12:
62                     alignment = 4;
63                     break;
64
65                 case 16:
66                     alignment = 8;
67                     break;
68
69                 default :
70                     throw new RuntimeException JavaDoc("Unsupported architecture");
71             }
72         } else { // Default to data formats for this hardware architecture
73 }
74
75         ras.seek(0); // Reset file pointer to start of file
76 }
77
78     private int indexOf(byte[] pattern, byte[] array) {
79         return (new String JavaDoc(array)).indexOf(new String JavaDoc(pattern));
80     }
81
82     boolean isBigEndian() {
83         return bigEndian;
84     }
85
86     int getAlignment() {
87         return alignment;
88     }
89
90     double readDouble() throws IOException {
91
92         //double value;
93 byte[] tx = new byte[8];
94
95         ras.read(buffer, 0, 8);
96
97         if (bigEndian) {
98             tx = buffer;
99         } else {
100             for (int i = 0; i < 8; i++) {
101                 tx[7 - i] = buffer[i];
102             }
103         }
104
105         DataInputStream reverseDis =
106                 new DataInputStream(new ByteArrayInputStream(tx));
107
108         return reverseDis.readDouble();
109     }
110
111     int readInt() throws IOException {
112         return readInt(false);
113     }
114
115     int readInt(boolean dump) throws IOException {
116
117         ras.read(buffer, 0, 4);
118
119         int value;
120
121         if (bigEndian) {
122             value = (0xFF & buffer[3]) | ((0xFF & buffer[2]) << 8)
123                     | ((0xFF & buffer[1]) << 16) | ((0xFF & buffer[0]) << 24);
124         } else {
125             value = (0xFF & buffer[0]) | ((0xFF & buffer[1]) << 8)
126                     | ((0xFF & buffer[2]) << 16) | ((0xFF & buffer[3]) << 24);
127         }
128
129         return value;
130     }
131
132     String JavaDoc readString(int maxLength) throws IOException {
133
134         ras.read(buffer, 0, maxLength);
135
136         return new String JavaDoc(buffer, 0, maxLength).trim();
137     }
138
139     void skipBytes(int n) throws IOException {
140         ras.skipBytes(n);
141     }
142
143     int align(int boundary) throws IOException {
144
145         int skip = (int) (boundary - (ras.getFilePointer() % boundary)) % boundary;
146
147         if (skip != 0) {
148             ras.skipBytes(skip);
149         }
150
151         return skip;
152     }
153
154     int align() throws IOException {
155         return align(alignment);
156     }
157
158     long info() throws IOException {
159         return ras.getFilePointer();
160     }
161
162     long getFilePointer() throws IOException {
163         return ras.getFilePointer();
164     }
165
166     void close() throws IOException {
167         ras.close();
168     }
169 }
170
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