# File lib/mail/encodings.rb, line 213
    def Encodings.b_value_encode(encoded_str, encoding = nil)
      return encoded_str if encoded_str.to_s.ascii_only?
      string, encoding = RubyVer.b_value_encode(encoded_str, encoding)
      map_lines(string) do |str|
        "=?#{encoding}?B?#{str.chomp}?="
      end.join(" ")
    end