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/*
* Copyright (C) 2006-2013 Bitronix Software (http://www.bitronix.be)
*
* Licensed 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 bitronix.tm.journal;
import bitronix.tm.utils.Decoder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
/**
* Used to control a log file's header.
* The physical data is read when this object is created then cached. Calling setter methods sets the header field
* then moves the file pointer back to the previous location.
*
* @author Ludovic Orban
*/
public class TransactionLogHeader {
private final static Logger log = LoggerFactory.getLogger(TransactionLogHeader.class);
/**
* Position of the format ID in the header (see {@link bitronix.tm.BitronixXid#FORMAT_ID}).
*/
public final static int FORMAT_ID_HEADER = 0;
/**
* Position of the timestamp in the header.
*/
public final static int TIMESTAMP_HEADER = FORMAT_ID_HEADER + 4;
/**
* Position of the log file state in the header.
*/
public final static int STATE_HEADER = TIMESTAMP_HEADER + 8;
/**
* Position of the current log position in the header.
*/
public final static int CURRENT_POSITION_HEADER = STATE_HEADER + 1;
/**
* Total length of the header.
*/
public final static int HEADER_LENGTH = CURRENT_POSITION_HEADER + 8;
/**
* State of the log file when it has been closed properly.
*/
public final static byte CLEAN_LOG_STATE = 0;
/**
* State of the log file when it hasn't been closed properly or it is still open.
*/
public final static byte UNCLEAN_LOG_STATE = -1;
private final FileChannel fc;
private final long maxFileLength;
private volatile int formatId;
private volatile long timestamp;
private volatile byte state;
private volatile long position;
/**
* TransactionLogHeader are used to control headers of the specified RandomAccessFile.
* @param fc the file channel to read from.
* @param maxFileLength the max file length.
* @throws IOException if an I/O error occurs.
*/
public TransactionLogHeader(FileChannel fc, long maxFileLength) throws IOException {
this.fc = fc;
this.maxFileLength = maxFileLength;
fc.position(FORMAT_ID_HEADER);
ByteBuffer buf = ByteBuffer.allocate(4 + 8 + 1 + 8);
while (buf.hasRemaining()) {
this.fc.read(buf);
}
buf.flip();
formatId = buf.getInt();
timestamp = buf.getLong();
state = buf.get();
position = buf.getLong();
fc.position(position);
if (log.isDebugEnabled()) { log.debug("read header " + this); }
}
/**
* Get FORMAT_ID_HEADER.
* @see #FORMAT_ID_HEADER
* @return the FORMAT_ID_HEADER value.
*/
public int getFormatId() {
return formatId;
}
/**
* Get TIMESTAMP_HEADER.
* @see #TIMESTAMP_HEADER
* @return the TIMESTAMP_HEADER value.
*/
public long getTimestamp() {
return timestamp;
}
/**
* Get STATE_HEADER.
* @see #STATE_HEADER
* @return the STATE_HEADER value.
*/
public byte getState() {
return state;
}
/**
* Get CURRENT_POSITION_HEADER.
* @see #CURRENT_POSITION_HEADER
* @return the CURRENT_POSITION_HEADER value.
*/
public long getPosition() {
return position;
}
/**
* Set FORMAT_ID_HEADER.
* @see #FORMAT_ID_HEADER
* @param formatId the FORMAT_ID_HEADER value.
* @throws IOException if an I/O error occurs.
*/
public void setFormatId(int formatId) throws IOException {
ByteBuffer buf = ByteBuffer.allocate(8);
buf.putInt(formatId);
buf.flip();
while (buf.hasRemaining()) {
fc.write(buf, FORMAT_ID_HEADER + buf.position());
}
this.formatId = formatId;
}
/**
* Set TIMESTAMP_HEADER.
* @see #TIMESTAMP_HEADER
* @param timestamp the TIMESTAMP_HEADER value.
* @throws IOException if an I/O error occurs.
*/
public void setTimestamp(long timestamp) throws IOException {
ByteBuffer buf = ByteBuffer.allocate(8);
buf.putLong(timestamp);
buf.flip();
while (buf.hasRemaining()) {
fc.write(buf, TIMESTAMP_HEADER + buf.position());
}
this.timestamp = timestamp;
}
/**
* Set STATE_HEADER.
* @see #STATE_HEADER
* @param state the STATE_HEADER value.
* @throws IOException if an I/O error occurs.
*/
public void setState(byte state) throws IOException {
ByteBuffer buf = ByteBuffer.allocate(1);
buf.put(state);
buf.flip();
while (buf.hasRemaining()) {
fc.write(buf, STATE_HEADER + buf.position());
}
this.state = state;
}
/**
* Set CURRENT_POSITION_HEADER.
* @see #CURRENT_POSITION_HEADER
* @param position the CURRENT_POSITION_HEADER value.
* @throws IOException if an I/O error occurs.
*/
public void setPosition(long position) throws IOException {
if (position < HEADER_LENGTH)
throw new IOException("invalid position " + position + " (too low)");
if (position > maxFileLength)
throw new IOException("invalid position " + position + " (too high)");
ByteBuffer buf = ByteBuffer.allocate(8);
buf.putLong(position);
buf.flip();
while (buf.hasRemaining()) {
fc.write(buf, CURRENT_POSITION_HEADER + buf.position());
}
this.position = position;
fc.position(position);
}
/**
* Rewind CURRENT_POSITION_HEADER back to the beginning of the file.
* @see #setPosition
* @throws IOException if an I/O error occurs.
*/
public void rewind() throws IOException {
setPosition(HEADER_LENGTH);
}
/**
* Create human-readable String representation.
* @return a human-readable String representing this object's state.
*/
@Override
public String toString() {
return "a Bitronix TransactionLogHeader with timestamp=" + timestamp +
", state=" + Decoder.decodeHeaderState(state) +
", position=" + position;
}
}