public String toString() {
		if (state_ == null) {
			return "OK";
		} else {
			String type = "";
			switch (code()) {
			case Code.kOk:
				type = "OK";
				break;
			case Code.kNotFound:
				type = "NotFound: ";
				break;
			case Code.kCorruption:
				type = "Corruption: ";
				break;
			case Code.kNotSupported:
				type = "Not implemented: ";
				break;
			case Code.kInvalidArgument:
				type = "Invalid argument: ";
				break;
			case Code.kIOError:
				type = "IO error: ";
				break;
			default:
				type = "Unknow code: " + code();
				break;
			}

			byte[] mess_ = new byte[state_.length - 5];
			System.arraycopy(state_, 5, mess_, 0, mess_.length);
			String mess = util.toString(mess_);

			return type + mess;
		}
	};