1 /***
2 *
3 * Copyright 2004 Hiram Chirino
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 **/
18 package org.activeio.journal.active;
19
20 import java.io.File;
21 import java.io.IOException;
22 import java.io.RandomAccessFile;
23 import java.nio.ByteBuffer;
24 import java.nio.channels.FileChannel;
25 import java.nio.channels.FileLock;
26
27 import org.activeio.Disposable;
28 import org.activeio.Packet;
29 import org.activeio.packet.ByteBufferPacket;
30
31 /***
32 * Control file holds the last known good state of the journal. It stores the state in
33 * record that is versioned and repeated twice in the file so that a failure in the
34 * middle of the write of the first or second record do not not result in an unknown
35 * state.
36 *
37 * @version $Revision: 1.1 $
38 */
39 final public class ControlFile implements Disposable {
40
41 /*** The File that holds the control data. */
42 private final RandomAccessFile file;
43 private final FileChannel channel;
44 private final ByteBufferPacket controlData;
45
46 private long controlDataVersion=0;
47 private FileLock lock;
48 private boolean disposed;
49
50 public ControlFile(File fileName, int controlDataSize) throws IOException {
51
52 boolean existed = fileName.exists();
53 file = new RandomAccessFile(fileName, "rw");
54 channel = file.getChannel();
55 controlData = new ByteBufferPacket(ByteBuffer.allocateDirect(controlDataSize));
56
57 }
58
59 /***
60 * Locks the control file.
61 * @throws IOException
62 */
63 public void lock() throws IOException {
64 if( lock==null ) {
65 lock = channel.tryLock();
66 if( lock ==null )
67 throw new IOException("Journal is allready opened by another application");
68 }
69 }
70
71 /***
72 * Un locks the control file.
73 * @throws IOException
74 */
75 public void unlock() throws IOException {
76 if( lock != null ) {
77 lock.release();
78 lock=null;
79 }
80 }
81
82 public boolean load() throws IOException {
83 long l = file.length();
84 if( l < controlData.capacity() ) {
85 controlDataVersion=0;
86 controlData.position(0);
87 controlData.limit(0);
88 return false;
89 } else {
90 file.seek(0);
91 long v1 = file.readLong();
92 file.seek(controlData.capacity()+8);
93 long v1check = file.readLong();
94
95 file.seek(controlData.capacity()+16);
96 long v2 = file.readLong();
97 file.seek((controlData.capacity()*2)+24);
98 long v2check = file.readLong();
99
100 if( v2 == v2check ) {
101 controlDataVersion = v2;
102 file.seek(controlData.capacity()+24);
103 controlData.clear();
104 channel.read(controlData.getByteBuffer());
105 } else if ( v1 == v1check ){
106 controlDataVersion = v1;
107 file.seek(controlData.capacity()+8);
108 controlData.clear();
109 channel.read(controlData.getByteBuffer());
110 } else {
111
112
113
114 throw new IOException("Control data corrupted.");
115 }
116 return true;
117 }
118 }
119
120 public void store() throws IOException {
121 controlDataVersion++;
122 file.setLength((controlData.capacity()*2)+32);
123 file.seek(0);
124
125
126 file.writeLong(controlDataVersion);
127 controlData.clear();
128 channel.write(controlData.getByteBuffer());
129 file.writeLong(controlDataVersion);
130
131
132 file.writeLong(controlDataVersion);
133 controlData.clear();
134 channel.write(controlData.getByteBuffer());
135 file.writeLong(controlDataVersion);
136
137 channel.force(false);
138 }
139
140 public Packet getControlData() {
141 controlData.clear();
142 return controlData;
143 }
144
145 public void dispose() {
146 if( disposed )
147 return;
148 disposed=true;
149 try {
150 unlock();
151 } catch (IOException e) {
152 }
153 try {
154 file.close();
155 } catch (IOException e) {
156 }
157 }
158 }