def encode(input)
      raise ArgumentError, "wrong input length" if input.bytesize % 4 > 0
      input = input.dup.force_encoding(Encoding::BINARY)
      ptr = ffi_delegate.encode(input, input.bytesize)
      raise_zmq_err if ptr.null?
      z85 = ptr.read_string
      z85.encode!(Encoding::ASCII)
      return z85
    end
def encode(input)
      raise ArgumentError, "wrong input length" if input.bytesize % 4 > 0
      input = input.dup.force_encoding(Encoding::BINARY)
      ptr = ffi_delegate.encode(input, input.bytesize)
      raise_zmq_err if ptr.null?
      z85 = ptr.read_string
      z85.encode!(Encoding::ASCII)
      return z85
    end
Encodes to Z85.
 @param input [String] possibly binary input data
 @return [String] Z85 encoded data as ASCII string
 @raise [ArgumentError] if input length isn't divisible by 4 with no
   remainder
 @raise [SystemCallError] if this fails