Function printf_to_std_format

Common/Core/vtkStringFormatter.cxx:723–838

Complete function to convert printf-like format to std::format

// Complete function to convert printf-like format to std::format
std::string printf_to_std_format(const std::string& format)
{
  // Compile the regex objects
  static std::regex printf_escape_regex_obj{ std::string(printf_escape_regex) };
  static std::regex printf_specifier_regex_obj{ std::string(printf_specifier_regex) };
  static std::regex std_format_begin_escape_regex_obj{ std::string(std_format_begin_escape_regex) };
  static std::regex std_format_end_escape_regex_obj{ std::string(std_format_end_escape_regex) };

  std::string std_format;
  size_t pos = 0;
  int argIndex = 0; // Track argument index for std::format

  while (pos < format.size())
  {
    if (format[pos] != '%')
    {
      // Copy plain text until '%' or end
      size_t start = pos;
      while (pos < format.size() && format[pos] != '%')
      {
        pos++;
      }
      std_format += format.substr(start, pos - start);
    }
    else
    {
      std::smatch match;
      // Handle '%' by checking for escape sequence
      if (std::regex_search(format.begin() + pos, format.end(), match, printf_escape_regex_obj,
            std::regex_constants::match_continuous))
      {
        // Handle escaped percentages (%%): add a single % to output
        std_format += "%";
        pos += match.length();
      }
      // Handle any variable specifier
      else if (std::regex_search(format.begin() + pos, format.end(), match,
                 printf_specifier_regex_obj, std::regex_constants::match_continuous))
      {
        // Parse the format Specifier components
        PrintfSpecifier spec;
        for (size_t classType = 3; classType < match.size(); classType += printf_groups_per_class)
        {
          if (!match[classType].str().empty())
          {
            spec.Type = static_cast<ClassType>(classType);
            // Parse flags
            std::string flags = match[classType + FLAGS].str();
            for (char flag : flags)
            {
              switch (flag)
              {
                case ' ':
                  spec.HasSpaceFill = true;
                  break;
                case '-':
                  spec.HasLeftJustify = true;
                  break;