internal bool HigherSequenceThan(LogSequence otherSequence)
{
ulong other = otherSequence.Count > 0 ? otherSequence.Head.SequenceNumber : 0;
ulong self = Count > 0 ? Head.SequenceNumber : 0;
return(self > other);
}
internal DiskImageFileInfo(FileHeader fileHeader, VhdxHeader vhdxHeader1, VhdxHeader vhdxHeader2, RegionTable regions, Metadata metadata, LogSequence activeLogSequence)
{
_fileHeader = fileHeader;
_vhdxHeader1 = vhdxHeader1;
_vhdxHeader2 = vhdxHeader2;
_regions = regions;
_metadata = metadata;
_activeLogSequence = activeLogSequence;
}
private LogSequence FindActiveLogSequence()
{
using (
Stream logStream =
new CircularStream(new SubStream(_fileStream, (long)_header.LogOffset, _header.LogLength),
Ownership.Dispose))
{
LogSequence candidateActiveSequence = new LogSequence();
LogEntry logEntry = null;
long oldTail;
long currentTail = 0;
do
{
oldTail = currentTail;
logStream.Position = currentTail;
LogSequence currentSequence = new LogSequence();
while (LogEntry.TryRead(logStream, out logEntry) &&
logEntry.LogGuid == _header.LogGuid &&
(currentSequence.Count == 0 ||
logEntry.SequenceNumber == currentSequence.Head.SequenceNumber + 1))
{
currentSequence.Add(logEntry);
logEntry = null;
}
if (currentSequence.Count > 0 &&
currentSequence.Contains(currentSequence.Head.Tail) &&
currentSequence.HigherSequenceThan(candidateActiveSequence))
{
candidateActiveSequence = currentSequence;
}
if (currentSequence.Count == 0)
{
currentTail += LogEntry.LogSectorSize;
}
else
{
currentTail = currentSequence.Head.Position + LogEntry.LogSectorSize;
}
currentTail = currentTail % logStream.Length;
} while (currentTail > oldTail);
return(candidateActiveSequence);
}
}
private void ReplayLog()
{
_freeSpace.Reserve((long)_header.LogOffset, _header.LogLength);
_logicalStream = _fileStream;
// If log is empty, skip.
if (_header.LogGuid == Guid.Empty)
{
return;
}
LogSequence activeLogSequence = FindActiveLogSequence();
if (activeLogSequence == null || activeLogSequence.Count == 0)
{
throw new IOException("Unable to replay VHDX log, suspected corrupt VHDX file");
}
if (activeLogSequence.Head.FlushedFileOffset > (ulong)_logicalStream.Length)
{
throw new IOException("truncated VHDX file found while replaying log");
}
if (activeLogSequence.Count > 1 || !activeLogSequence.Head.IsEmpty)
{
// However, have seen VHDX with a non-empty log with no data to replay. These are
// 'safe' to open.
if (!_fileStream.CanWrite)
{
SnapshotStream replayStream = new SnapshotStream(_fileStream, Ownership.None);
replayStream.Snapshot();
_logicalStream = replayStream;
}
foreach (LogEntry logEntry in activeLogSequence)
{
if (logEntry.LogGuid != _header.LogGuid)
{
throw new IOException("Invalid log entry in VHDX log, suspected currupt VHDX file");
}
if (logEntry.IsEmpty)
{
continue;
}
logEntry.Replay(_logicalStream);
}
_logicalStream.Seek((long)activeLogSequence.Head.LastFileOffset, SeekOrigin.Begin);
}
}
private void ReplayLog()
{
_freeSpace.Reserve((long)_header.LogOffset, _header.LogLength);
_logicalStream = _fileStream;
// If log is empty, skip.
if (_header.LogGuid == Guid.Empty)
{
return;
}
LogSequence activeLogSequence = FindActiveLogSequence();
if (activeLogSequence == null || activeLogSequence.Count == 0)
{
throw new IOException("Unable to replay VHDX log, suspected corrupt VHDX file");
}
if (activeLogSequence.Count > 1 || !activeLogSequence.Head.IsEmpty)
{
// TODO - perform actual replay (needs VHDX with real log to replay)
// However, have seen VHDX with a non-empty log with no data to replay. These are
// 'safe' to open.
throw new NotImplementedException("Actual replay of VHDX logs not implemented yet");
//// Have a log to replay, and the base stream is read-only. Use a snapshot stream to
//// replay in RAM.
////if (!_fileStream.CanWrite)
////{
//// SnapshotStream replayStream = new SnapshotStream(_fileStream, Ownership.None);
//// replayStream.Snapshot();
//// _logicalStream = replayStream;
////}
}
}
