module Mail
  grammar ContentTransferEncoding

    include RFC2822
    include RFC2045

    rule primary
      CFWS encoding CFWS
    end
    
    rule encoding
      known_tokens / ietf_token / x_token {
        def encoding
          known_tokens.text_value || ietf_token.text_value || x_token.text_value
        end
      }
    end
    
    rule known_tokens
      "7bit" / "8bit" / "binary" / 
      "quoted-printable" / "base64"
    end
    
  end
end