Better mode implementation

src/pandroid/app/src/main/java/com/panda3ds/pandroid/AlberDriver.java

@@ -32,30 +32,31 @@ public class AlberDriver {
 
 	public static native void setShaderJitEnabled(boolean enable);
 
+
+	public static String parseNativeMode(String mode){
+		mode = mode.toLowerCase();
+		switch (mode){
+			case "r":
+			case "rb":
+				return "r";
+			case "r+":
+			case "r+b":
+			case "rb+":
+				return "rw";
+			case "w+":
+				return "rwt";
+			case "w":
+			case "wb":
+				return "wt";
+			case "wa":
+				return "wa";
+		}
+		throw new IllegalArgumentException("Invalid file mode: "+mode);
+	}
+
 	public static int openDocument(String path, String mode){
 		try {
-			mode = mode.toLowerCase();
+			mode = parseNativeMode(mode);
-			switch (mode) {
-				case "rb":
-				case "rb+":
-				case "r+b":
-					mode = "r";
-					break;
-				case "wb":
-				case "wb+":
-				case "w+b":
-					mode = "w";
-					break;
-				case "rwt":
-				case "wt":
-				case "rw":
-				case "r":
-				case "w":
-				case "wa":
-					break;
-				default:
-					throw new IllegalArgumentException("Invalid mode: "+mode);
-			}
 			Context context = PandroidApplication.getAppContext();
 			Uri uri = FileUtils.obtainUri(path);
 			ParcelFileDescriptor parcel;