/// <summary>
/// Rolls back transaction by copying all backed up data bask to master stream and closes the transaction.
/// </summary>
public void RollbackTransaction()
{
if (logStreamHeader != null)
{
if (logStreamHeader.TransactionCompleted)
{
throw new InvalidOperationException("Can't rollback completed transaction");
}
logStream.Position = TransactionLogStreamMetadata.StructureSize;
// Copy segments from log stream back to stream
for (int i = 0; i < logStreamHeader.SegmentCount; i++)
{
SegmentMetadata sh = SegmentMetadata.Load(logStream);
if (!sh.TransactionId.Equals(logStreamHeader.TransactionId))
{
throw new InvalidOperationException("Wrong segment found in transaction log");
}
masterStream.Position = sh.Position;
CopyData(logStream, sh.Size, masterStream);
}
// Set back original stream length
if (logStreamHeader.StreamLength < masterStream.Length)
{
masterStream.SetLength(logStreamHeader.StreamLength);
}
masterStream.Flush();
logStream.SetLength(0);
logStream.Flush();
logStreamHeader = null;
rollbackNeeded = false;
}
}
public static SegmentMetadata Load(Stream stream)
{
BinaryReader reader = new BinaryReader(stream);
SegmentMetadata sh = new SegmentMetadata
{
TransactionId = new Guid(reader.ReadBytes(16)),
Position = reader.ReadInt64(),
Size = reader.ReadInt32()
};
return(sh);
}
// Copies a section of data from master stream to the log stream
void BackupData(long location, int size)
{
logStream.Seek(0, SeekOrigin.End);
// Write segment header
SegmentMetadata sh = new SegmentMetadata
{
TransactionId = logStreamHeader.TransactionId,
Position = location,
Size = size
};
long metadataPos = logStream.Position;
sh.Save(logStream);
// Copy data
masterStream.Position = location;
int bytesCopied = CopyData(masterStream, size, logStream);
// If bytes copied differ from size in header, update the header
if (bytesCopied != size)
{
logStream.Position = metadataPos;
sh.Size = bytesCopied;
sh.Save(logStream);
}
logStream.Flush();
// Update log stream header
logStreamHeader.SegmentCount++;
logStreamHeader.Save(logStream);
logStream.Flush();
}