added default value to iohelper.get_newline

cat_win/src/service/helper/iohelper.py

@@ -186,7 +186,7 @@ def yield_file(src_file: Path, binary: bool = False,
             file.close()
 
     @staticmethod
-    def get_newline(file: Path) -> str:
+    def get_newline(file: Path, default: str = '\n') -> str:
         """
         determines the line ending of a given file.
 
@@ -202,10 +202,10 @@ def get_newline(file: Path) -> str:
         try:
             with open(file, 'rb') as _f:
                 _l = _f.readline()
-                _l += b'\n' * bool(not _l[-1:] or _l[-1:] not in b'\r\n')
-                return '\r\n' if _l[-2:] == b'\r\n' else _l[-1:].decode()
+                _l+= default.encode() * (not _l[-1:] or _l[-1:] not in b'\r\n')
+                return _l[-1-(_l[-2:] == b'\r\n'):].decode()
         except OSError:
-            return '\n'
+            return default
 
 
     @staticmethod

cat_win/tests/src/service/helper/test_iohelper.py

@@ -55,6 +55,9 @@ def test_get_newline(self):
         self.assertEqual(IoHelper.get_newline(test_file_path), '\r\n')
         self.assertEqual(IoHelper.get_newline(test_file_path_empty), '\n')
         self.assertEqual(IoHelper.get_newline(test_file_path_oneline), '\n')
+        self.assertEqual(IoHelper.get_newline(test_file_path, 'x'), '\r\n')
+        self.assertEqual(IoHelper.get_newline(test_file_path_empty, 'x'), 'x')
+        self.assertEqual(IoHelper.get_newline(test_file_path_oneline, 'x'), 'x')
 
     def test_get_stdin_content_oneline(self):
         stdin_mock.set_content('hello\nworld')