/**
* Copyright 2010 JBoss Inc
*
* 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 org.slf4j.LoggerFactory;
import org.slf4j.Logger;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.Set;
import java.util.HashSet;
import bitronix.tm.utils.Uid;
/**
* Used to read {@link TransactionLogRecord} objects from a log file.
* <p>© <a href="http://www.bitronix.be">Bitronix Software</a></p>
*
* @author lorban
*/
public class TransactionLogCursor {
private final static Logger log = LoggerFactory.getLogger(TransactionLogCursor.class);
private final RandomAccessFile randomAccessFile;
private long endPosition;
/**
* Create a TransactionLogCursor that will read from the specified file.
* This opens a new read-only file descriptor.
* @param file the file to read logs from
* @throws IOException if an I/O error occurs.
*/
public TransactionLogCursor(File file) throws IOException {
this.randomAccessFile = new RandomAccessFile(file, "r");
this.randomAccessFile.seek(TransactionLogHeader.CURRENT_POSITION_HEADER);
endPosition = this.randomAccessFile.readLong();
}
/**
* Fetch the next TransactionLogRecord from log, recalculating the CRC and checking it against the stored one.
* InvalidChecksumException is thrown if the check fails.
* @return the TransactionLogRecord or null if the end of the log file has been reached
* @throws IOException if an I/O error occurs.
*/
public TransactionLogRecord readLog() throws IOException {
return readLog(false);
}
/**
* Fetch the next TransactionLogRecord from log.
* @param skipCrcCheck if set to false, the method will thow an InvalidChecksumException if the CRC on disk does
* not match the recalculated one. Otherwise, the CRC is not recalculated nor checked agains the stored one.
* @return the TransactionLogRecord or null if the end of the log file has been reached
* @throws IOException if an I/O error occurs.
*/
public TransactionLogRecord readLog(boolean skipCrcCheck) throws IOException {
synchronized (randomAccessFile) {
long currentPosition = randomAccessFile.getFilePointer();
if (currentPosition >= endPosition) {
if (log.isDebugEnabled()) log.debug("end of transaction log file reached at " + randomAccessFile.getFilePointer());
return null;
}
int status = randomAccessFile.readInt();
int recordLength = randomAccessFile.readInt();
// check that log is in file bounds
long savedPos = randomAccessFile.getFilePointer();
randomAccessFile.skipBytes(recordLength - 4);
if (randomAccessFile.getFilePointer() + 4 > endPosition) {
randomAccessFile.skipBytes(4);
throw new CorruptedTransactionLogException("corrupted log found at position " + currentPosition +
" (record terminator outside of file bounds: " + randomAccessFile.getFilePointer() + " of " +
endPosition + ", recordLength: " + recordLength + ")");
}
// check for log terminator
int endCode = randomAccessFile.readInt();
long endOfRecordPosition = randomAccessFile.getFilePointer();
if (endCode != TransactionLogAppender.END_RECORD)
throw new CorruptedTransactionLogException("corrupted log found at position " + currentPosition +
" (no record terminator found)");
randomAccessFile.seek(savedPos);
int headerLength = randomAccessFile.readInt();
long time = randomAccessFile.readLong();
int sequenceNumber = randomAccessFile.readInt();
int crc32 = randomAccessFile.readInt();
byte gtridSize = randomAccessFile.readByte();
// check that GTRID is not too long
if (4 + 8 + 4 + 4 + 1 + gtridSize > recordLength) {
randomAccessFile.seek(endOfRecordPosition);
throw new CorruptedTransactionLogException("corrupted log found at position " + currentPosition +
" (GTRID size too long)");
}
byte[] gtridArray = new byte[gtridSize];
randomAccessFile.readFully(gtridArray);
Uid gtrid = new Uid(gtridArray);
int uniqueNamesCount = randomAccessFile.readInt();
Set uniqueNames = new HashSet();
int currentReadCount = 4 + 8 + 4 + 4 + 1 + gtridSize + 4;
for (int i=0; i<uniqueNamesCount ;i++) {
int length = randomAccessFile.readShort();
// check that names aren't too long
currentReadCount += 2 + length;
if (currentReadCount > recordLength) {
randomAccessFile.seek(endOfRecordPosition);
throw new CorruptedTransactionLogException("corrupted log found at position " + currentPosition +
" (unique names too long, " + (i+1) + " out of " + uniqueNamesCount + ", length: " + length +
", currentReadCount: " + currentReadCount + ", recordLength: " + recordLength + ")");
}
byte[] nameBytes = new byte[length];
randomAccessFile.readFully(nameBytes);
uniqueNames.add(new String(nameBytes, "US-ASCII"));
}
int cEndRecord = randomAccessFile.readInt();
TransactionLogRecord tlog = new TransactionLogRecord(status, recordLength, headerLength, time, sequenceNumber, crc32, gtrid, uniqueNames, cEndRecord);
// check that CRC is okay
if (!skipCrcCheck && !tlog.isCrc32Correct()) {
randomAccessFile.seek(endOfRecordPosition);
throw new CorruptedTransactionLogException("corrupted log found at position " + currentPosition + "(invalid CRC, recorded: " + tlog.getCrc32() +
", calculated: " + tlog.calculateCrc32() + ")");
}
return tlog;
}
}
/**
* Close the cursor and the underlying file
* @throws IOException if an I/O error occurs.
*/
public void close() throws IOException {
synchronized (randomAccessFile) {
randomAccessFile.close();
}
}
}