def decode(input)
      raise ArgumentError, "wrong input length" if input.bytesize % 5 > 0
      zchunk = ffi_delegate.decode(input)
      raise_zmq_err if zchunk.null?
      decoded_string = zchunk.data.read_string(zchunk.size - 1)
      return decoded_string
    end
def decode(input)
      raise ArgumentError, "wrong input length" if input.bytesize % 5 > 0
      zchunk = ffi_delegate.decode(input)
      raise_zmq_err if zchunk.null?
      decoded_string = zchunk.data.read_string(zchunk.size - 1)
      return decoded_string
    end
Decodes from Z85.
 @param input [String] Z85 encoded data
 @return [String] original data as binary string
 @raise [ArgumentError] if input length isn't divisible by 5 with no
   remainder
 @raise [SystemCallError] if this fails