## vim: ft=makopython

    class LineMode(_Enum):
        """
        Determine how the preprocessor treats directives and disabled lines in
        the output.

        ``delete_lines``

          Just delete these lines: this breaks line number correspondance
          between the original source and the preprocessed one. This
          corresponds to GNATprep's default mode.

        ``blank_lines``

          Replace these lines with empty lines. This corresponds to GNATprep's
          ``-b`` option.

        ``comment_lines``

          Preserve these lines and emit a ``--!`` comment marker in front of
          them. This corresponds to GNATprep's ``-c`` option.
        """

        delete_lines = "delete_lines"
        blank_lines = "blank_lines"
        comment_lines = "comment_lines"

        _name = "LineMode"
        _c_to_py = [delete_lines, blank_lines, comment_lines]
        _py_to_c = {name: index for index, name in enumerate(_c_to_py)}

    @classmethod
    def create_preprocessor_from_file(
        cls,
        filename: str,
        path: List[str],
        line_mode: Optional[FileReader.LineMode]
    ) -> FileReader:
        ${py_doc('libadalang.create_preprocessor_from_file', 8)}

        # Create an array of C strings to hold the path directories
        c_dirs = [ctypes.c_char_p(_unwrap_filename(d)) for d in path]
        c_path_data = (ctypes.c_char_p * len(c_dirs))()
        for i, d in enumerate(c_dirs):
            c_path_data[i] = d

        # Create the pointer to this array, with the expected type according to
        # ctypes.
        c_path_type = ctypes.POINTER(ctypes.c_char_p)
        c_path = ctypes.cast(ctypes.byref(c_path_data), c_path_type)

        # Pass the line mode to force, if any
        if line_mode is not None:
            lm = ctypes.c_int(FileReader.LineMode._unwrap(line_mode))
            lm_ref = ctypes.byref(lm)
        else:
            lm_ref = ctypes.POINTER(ctypes.c_int)()

        # We can now create the file reader itself
        c_value = _create_preprocessor_from_file(
            _unwrap_filename(filename), c_path, len(c_dirs), lm_ref
        )
        return cls(c_value)