OpenMcdf.CFCorruptedFileException: The file is corrupted.

I’m getting the above message when writing data. I’ve spent a fair amount of debugging and am still clueless how this could happen.

First of all, it doesn’t happen all the time. We’re writing to hundreds of streams that work all fine, but sometimes it fails with this message (here a 190M file). The stack trace looks like this:

OpenMcdf.CFCorruptedFileException : The file is corrupted.
   at OpenMcdf.CompoundFile.EnsureUniqueSectorIndex(Int32 nextSecID, HashSet`1 processedSectors)
   at OpenMcdf.CompoundFile.GetFatSectorChain()
   at OpenMcdf.CompoundFile.GetNormalSectorChain(Int32 secID)
   at OpenMcdf.CompoundFile.GetSectorChain(Int32 secID, SectorType chainType)
   at OpenMcdf.CompoundFile.WriteData(CFItem cfItem, Byte[] buffer, Int64 position, Int32 offset, Int32 count)
   at OpenMcdf.CompoundFile.WriteData(CFItem cfItem, Int64 position, Byte[] buffer)
   at OpenMcdf.CompoundFile.WriteData(CFItem cfItem, Byte[] buffer)
   at OpenMcdf.CFStream.SetData(Byte[] data)
   at VisualPinball.Engine.IO.BiffData.WriteData(CFStorage gameStorage, HashWriter hashWriter) in VisualPinball.Engine\VisualPinball.Engine\IO\BiffData.cs:line 49
   at VisualPinball.Engine.VPT.Table.TableWriter.WriteImages() in VisualPinball.Engine\VisualPinball.Engine\VPT\Table\TableWriter.cs:line 105
   at VisualPinball.Engine.VPT.Table.TableWriter.WriteTable(String fileName) in VisualPinball.Engine\VisualPinball.Engine\VPT\Table\TableWriter.cs:line 40
   at VisualPinball.Engine.VPT.Table.Table.Save(String fileName) in VisualPinball.Engine\VisualPinball.Engine\VPT\Table\Table.cs:line 165
   at VisualPinball.Engine.Test.VPT.DebugTests.ShouldWriteChecksum() in VisualPinball.Engine\VisualPinball.Engine.Test\VPT\DebugTests.cs:line 13

The project is an open source pinball simulator, and it’s kind of awkward to reproduce, but here we go nevertheless:

1. Clone freezy/VisualPinball.Engine
2. Download the test file writefail.vpx here
3. Open DebugTests.cs and add this method:

   [Test]
   public void ShouldWrite()
   {
   	var table = Engine.VPT.Table.Table.Load(@"path to writefail.vpx");
   	table.Save( @"some other path");
   }
   

4. Execute the test and verify it works
5. Open ItemData.cs and remove string.Empty from EditorLayerName on line 24, setting its default value to null
6. Re-run the test to reproduce the error

Thing is, it’s just binary data. Setting that field to null just doesn’t write it into a binary blob. How this could trigger such an error is beyond me, but I admit I don’t entirely understand the compound doc format.

Any hints or suggestions would be greatly appreciated.

[ironfede]

@freezy thank you for letting me know. Please notice that nuget pkg for openmcdf 2.2.1.6 is source link enabled to allow a deeper analysis and debug of suspected issues. Best regards, Federico

[ironfede]

@freezy many thanks for reporting this issue . There was an issue in handling a limit condition while loading DIFAT sectors when exactly 508 bytes were written AND only one sector exists (I think that I really couldn’t create such a ‘perfect’ test 😉 ) I’ve committed the fix but I need time to extensively recheck potential regressions from this change before publishing a nuget package. Please, try to build and reference the new library from source to verify your use case: it looks ok to me. Best Regards, Federico