/// <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;
}
}
/// <summary>
/// Marks in the log file that transaction has ended
/// </summary>
public void EndTransaction()
{
CheckState();
if (logStreamHeader != null)
{
masterStream.Flush();
logStreamHeader.TransactionCompleted = true;
logStreamHeader.Save(logStream);
logStream.Flush();
logStreamHeader = null;
CheckSegments();
}
}
/// <summary>
/// Start transaction
/// </summary>
/// <param name="initialSegments">Areas in master stream which don't require backing up. Can be null.</param>
public Guid BeginTransaction(IEnumerable <Segment> initialSegments = null)
{
CheckState();
if (logStream == null)
{
throw new InvalidOperationException("Log stream not specified");
}
if (logStreamHeader != null)
{
throw new InvalidOperationException("Unable to start new transaction while existing transaction is in progress");
}
// Add custom segments that will not be backed up
segments.Clear();
if (initialSegments != null)
{
// <源码修改>
//IOrderedEnumerable<Segment> orderedList = initialSegments.OrderBy(x => x.Location);
var orderedList = new List <Segment>(initialSegments);
orderedList.Sort(SegmentComparer.Instance);
// </源码修改>
foreach (var segment in orderedList)
{
segments.AddLast(segment);
}
}
// Add unallocated space after the end of stream
segments.AddLast(new Segment(masterStream.Length, long.MaxValue - masterStream.Length));
CheckSegments();
// Truncate transaction log
logStream.SetLength(0);
logStream.Flush();
// Initialize transaction log
logStreamHeader = new TransactionLogStreamMetadata
{
TransactionId = Guid.NewGuid(),
StreamLength = masterStream.Length,
SegmentCount = 0,
TransactionCompleted = false
};
logStreamHeader.Save(logStream);
logStream.Flush();
return(logStreamHeader.TransactionId);
}
/// <summary>
/// Consrtructs a transaction stream on top of the specified master stream
/// </summary>
/// <param name="masterStream">Stream for which backup si performed</param>
/// <param name="logStream">Stream where backed up data is stored</param>
/// <param name="blockSize">Size of the minimum block size that will be backed up</param>
public TransactionStream(Stream masterStream, Stream logStream, long blockSize)
{
this.masterStream = masterStream;
this.logStream = logStream;
this.blockSize = blockSize;
// Check if previous transaction has completed
if (logStream != null && logStream.Length > TransactionLogStreamMetadata.StructureSize)
{
logStreamHeader = TransactionLogStreamMetadata.Load(logStream);
rollbackNeeded = !logStreamHeader.TransactionCompleted;
if (logStreamHeader.SegmentCount == 0 || logStreamHeader.TransactionCompleted)
{
logStreamHeader = null;
}
}
}
