Fast checking for file existance

OpenRA.FileFormats/CompressedPackage.cs

@@ -36,5 +36,10 @@ namespace OpenRA.FileFormats
 		}
 
 		public IEnumerable<uint> AllFileHashes() { return hashes; }
+		
+		public bool Exists(string filename)
+		{
+			return hashes.Contains(PackageEntry.HashFilename(filename));
+		}
 	}
 }

OpenRA.FileFormats/FileSystem.cs

@@ -122,15 +122,8 @@ namespace OpenRA.FileFormats
 		public static bool Exists(string filename)
 		{
 			foreach (var folder in mountedFolders)
-			{
+				if (folder.Exists(filename))
-				var s = folder.GetContent(filename);
-				if (s != null)
-				{
-					s.Dispose();
 				    return true;
-				}
-			}
-
 			return false;
 		}
 

OpenRA.FileFormats/Folder.cs

@@ -30,5 +30,10 @@ namespace OpenRA.FileFormats
 			foreach( var filename in Directory.GetFiles( path, "*", SearchOption.TopDirectoryOnly ) )
 				yield return PackageEntry.HashFilename( filename );
 		}
+		
+		public bool Exists(string filename)
+		{
+			return File.Exists(Path.Combine(path,filename));
+		}
 	}
 }

OpenRA.FileFormats/Package.cs

@@ -18,6 +18,7 @@ namespace OpenRA.FileFormats
 	public interface IFolder
 	{
 		Stream GetContent(string filename);
+		bool Exists(string filename);
 		IEnumerable<uint> AllFileHashes();
 	}
 
@@ -143,6 +144,11 @@ namespace OpenRA.FileFormats
 		{
 			return index.Keys;
 		}
+		
+		public bool Exists(string filename)
+		{
+			return index.ContainsKey(PackageEntry.HashFilename(filename));
+		}
 	}
 
 	[Flags]