Fix switching transacted streams

OpenMcdf.Tests/RootStorageTests.cs

@@ -174,4 +174,37 @@ public void SwitchFile(Version version, int subStorageCount)
             try { File.Delete(fileName); } catch { }
         }
     }
+
+    [TestMethod]
+    [DataRow(Version.V3, 0)]
+    [DataRow(Version.V3, 1)]
+    [DataRow(Version.V3, 2)]
+    [DataRow(Version.V3, 4)] // Required 2 sectors including root
+    [DataRow(Version.V4, 0)]
+    [DataRow(Version.V4, 1)]
+    [DataRow(Version.V4, 2)]
+    [DataRow(Version.V4, 32)] // Required 2 sectors including root
+    public void SwitchTransactedStream(Version version, int subStorageCount)
+    {
+        using MemoryStream originalMemoryStream = new();
+        using MemoryStream switchedMemoryStream = new();
+
+        using (var rootStorage = RootStorage.Create(originalMemoryStream, version, StorageModeFlags.Transacted | StorageModeFlags.LeaveOpen))
+        {
+            for (int i = 0; i < subStorageCount; i++)
+                rootStorage.CreateStorage($"Test{i}");
+
+            rootStorage.SwitchTo(switchedMemoryStream);
+            rootStorage.Commit();
+        }
+
+        using (var rootStorage = RootStorage.Open(switchedMemoryStream))
+        {
+            IEnumerable<EntryInfo> entries = rootStorage.EnumerateEntries();
+            Assert.AreEqual(subStorageCount, entries.Count());
+
+            for (int i = 0; i < subStorageCount; i++)
+                rootStorage.OpenStorage($"Test{i}");
+        }
+    }
 }

OpenMcdf/RootContext.cs

@@ -26,6 +26,8 @@ internal sealed class RootContext : ContextBase, IDisposable
 
     public Stream BaseStream { get; }
 
+    public Stream Stream { get; }
+
     public CfbBinaryReader Reader { get; }
 
     public CfbBinaryWriter Writer
@@ -104,17 +106,20 @@ public RootContext(RootContextSite rootContextSite, Stream stream, Version versi
         DirectoryEntriesPerSector = SectorSize / DirectoryEntry.Length;
         Length = stream.Length;
 
-        Stream actualStream = stream;
         if (contextFlags.HasFlag(IOContextFlags.Transacted))
         {
             Stream overlayStream = stream is MemoryStream ? new MemoryStream() : File.Create(Path.GetTempFileName());
             transactedStream = new TransactedStream(ContextSite, stream, overlayStream);
-            actualStream = new BufferedStream(transactedStream, SectorSize);
+            Stream = new BufferedStream(transactedStream, SectorSize);
+        }
+        else
+        {
+            Stream = stream;
         }
 
-        Reader = new(actualStream);
+        Reader = new(Stream);
         if (stream.CanWrite)
-            writer = new(actualStream);
+            writer = new(Stream);
 
         Fat = new(ContextSite);
         DirectoryEntries = new(ContextSite);

OpenMcdf/RootStorage.cs

@@ -78,7 +78,7 @@ public static RootStorage Create(Stream stream, Version version = Version.V3, St
         return new RootStorage(rootContextSite, flags);
     }
 
-    public static RootStorage CreateInMemory(Version version = Version.V3) => Create(new MemoryStream(), version);
+    public static RootStorage CreateInMemory(Version version = Version.V3, StorageModeFlags flags = StorageModeFlags.None) => Create(new MemoryStream(), version, flags);
 
     public static RootStorage Open(string fileName, FileMode mode, StorageModeFlags flags = StorageModeFlags.None)
     {
@@ -205,15 +205,7 @@ public void Revert()
     private void SwitchToCore(Stream stream, bool allowLeaveOpen)
     {
         Flush();
-
-        stream.SetLength(Context.BaseStream.Length);
-
-        stream.Position = 0;
-        Context.BaseStream.Position = 0;
-
-        Context.BaseStream.CopyTo(stream);
-        stream.Position = 0;
-
+        Context.Stream.CopyAllTo(stream);
         Context.Dispose();
 
         IOContextFlags contextFlags = ToIOContextFlags(storageModeFlags);