/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.jackrabbit.core.journal;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
/**
* Maintains a file-based revision counter with locking, assuring uniqueness.
*/
public class FileRevision implements InstanceRevision {
/**
* Logger.
*/
private static final Logger log = LoggerFactory.getLogger(FileRevision.class);
/**
* Underlying random access file.
*/
protected final RandomAccessFile raf;
/**
* Flag indicating whether to sync the file on every write.
*/
protected final boolean sync;
/**
* Cached value.
*/
protected long value;
/**
* Flag indicating whether this revision file is closed.
*/
protected boolean closed;
/**
* Creates a new file based revision counter.
*
* @param file holding global counter
* @param sync whether to sync the file on every write
*
* @throws JournalException if some error occurs
*/
public FileRevision(File file, boolean sync) throws JournalException {
this.sync = sync;
try {
if (!file.exists()) {
file.createNewFile();
}
raf = new RandomAccessFile(file, "rw");
if (raf.length() == 0) {
set(0);
}
} catch (IOException e) {
String msg = "I/O error while attempting to create new file '" + file + "'.";
throw new JournalException(msg, e);
}
}
/**
* Return current counter value.
*
* @return counter value
* @throws JournalException if some error occurs
*/
public synchronized long get() throws JournalException {
try {
if (closed) {
throw new JournalException("Revision file closed.");
}
raf.seek(0L);
value = raf.readLong();
return value;
} catch (IOException e) {
throw new JournalException("I/O error occurred.", e);
}
}
/**
* Set current counter value.
*
* @param value new counter value
* @throws JournalException if some error occurs
*/
public synchronized void set(long value) throws JournalException {
try {
if (closed) {
throw new JournalException("Revision file closed.");
}
raf.seek(0L);
raf.writeLong(value);
if (sync) {
raf.getFD().sync();
}
this.value = value;
} catch (IOException e) {
throw new JournalException("I/O error occurred.", e);
}
}
/**
* Close file revision. Closes underlying random access file.
*/
public synchronized void close() {
try {
raf.close();
closed = true;
} catch (IOException e) {
log.warn("I/O error closing revision file.", e);
}
}
}