Function parse_refresh_rate_string

src/display_device.cpp:198–258

* @brief Parse refresh rate value from the string. * @param input String to be parsed. * @param output Reference to output variable to fill in. * @param allow_decimal_point Specify whether the decimal point is allowed or not. * @returns True on successful parsing (empty string allowed), false otherwise. * * @examples * std::optional refresh_rate;

     * @examples_end
     */
    bool parse_refresh_rate_string(const std::string &input, std::optional<FloatingPoint> &output, const bool allow_decimal_point = true) {
      static const auto is_zero {[](const auto &character) {
        return character == '0';
      }};
      const std::string trimmed_input {boost::algorithm::trim_copy(input)};
      const std::regex refresh_rate_regex {allow_decimal_point ? R"(^(\d+)(?:\.(\d+))?$)" : R"(^(\d+)$)"};

      if (std::smatch match; std::regex_match(trimmed_input, match, refresh_rate_regex)) {
        try {
          // Here we are trimming zeros from the string to possibly reduce out of bounds case
          std::string trimmed_match_1 {boost::algorithm::trim_left_copy_if(match[1].str(), is_zero)};
          if (trimmed_match_1.empty()) {
            trimmed_match_1 = "0"s;  // Just in case ALL the string is full of zeros, we want to leave one
          }

          std::string trimmed_match_2;
          if (allow_decimal_point && match[2].matched) {
            trimmed_match_2 = boost::algorithm::trim_right_copy_if(match[2].str(), is_zero);
          }

          if (!trimmed_match_2.empty()) {
            // We have a decimal point and will have to split it into numerator and denominator.
            // For example:
            //   59.995:
            //     numerator = 59995
            //     denominator = 1000

            // We are essentially removing the decimal point here: 59.995 -> 59995
            const std::string numerator_str {trimmed_match_1 + trimmed_match_2};
            const auto numerator {stou(numerator_str)};

            // Here we are counting decimal places and calculating denominator: 10^decimal_places
            const auto denominator {static_cast<unsigned int>(std::pow(10, trimmed_match_2.size()))};

            output = Rational {numerator, denominator};
          } else {
            // We do not have a decimal point, just a valid number.
            // For example:
            //   60:
            //     numerator = 60
            //     denominator = 1
            output = Rational {stou(trimmed_match_1), 1};
          }
          return true;
        } catch (const std::out_of_range &) {
          BOOST_LOG(error) << "Failed to parse refresh rate string " << trimmed_input << " (number out of range).";
        } catch (const std::exception &err) {
          BOOST_LOG(error) << "Failed to parse refresh rate string " << trimmed_input << ":\n"
                           << err.what();
        }
      } else {
        if (trimmed_input.empty()) {
          output = std::nullopt;
          return true;
        }

        BOOST_LOG(error) << "Failed to parse refresh rate string " << trimmed_input << ". Must have a pattern of " << (allow_decimal_point ? R"("123" or "123.456")" : R"("123")") << "!";
      }