Make IFolder interface inherently IDisposable.

Fix up implementations to ensure they dispose any stream they acquire, and ensure the constructor will not leave a stream open if it fails. Dispose folders when unmounting them in GlobalFileSystem.

OpenRA.Game/FileSystem/D2kSoundResources.cs

@@ -14,7 +14,7 @@ using System.IO;
 
 namespace OpenRA.FileSystem
 {
-	public class D2kSoundResources : IFolder
+	public sealed class D2kSoundResources : IFolder
 	{
 		readonly Stream s;
 
@@ -30,22 +30,28 @@ namespace OpenRA.FileSystem
 			this.priority = priority;
 
 			s = GlobalFileSystem.Open(filename);
-			s.Seek(0, SeekOrigin.Begin);
-
-			filenames = new List<string>();
-
-			var headerLength = s.ReadUInt32();
-			while (s.Position < headerLength + 4)
+			try
 			{
-				var name = s.ReadASCIIZ();
-				var offset = s.ReadUInt32();
-				var length = s.ReadUInt32();
+				filenames = new List<string>();
 
-				var hash = PackageEntry.HashFilename(name, PackageHashType.Classic);
-				if (!index.ContainsKey(hash))
-					index.Add(hash, new PackageEntry(hash, offset, length));
+				var headerLength = s.ReadUInt32();
+				while (s.Position < headerLength + 4)
+				{
+					var name = s.ReadASCIIZ();
+					var offset = s.ReadUInt32();
+					var length = s.ReadUInt32();
 
-				filenames.Add(name);
+					var hash = PackageEntry.HashFilename(name, PackageHashType.Classic);
+					if (!index.ContainsKey(hash))
+						index.Add(hash, new PackageEntry(hash, offset, length));
+
+					filenames.Add(name);
+				}
+			}
+			catch
+			{
+				Dispose();
+				throw;
 			}
 		}
 
@@ -92,5 +98,10 @@ namespace OpenRA.FileSystem
 		{
 			throw new NotImplementedException("Cannot save Dune 2000 Sound Resources.");
 		}
+
+		public void Dispose()
+		{
+			s.Dispose();
+		}
 	}
 }