Class write_int_data

Source/ThirdParty/fmt/format.h:1851–2568

// Data for write_int that doesn't depend on output iterator type. It is used to
// avoid template code bloat.
template <typename Char> struct write_int_data {
  size_t size;
  size_t padding;

  FMT_CONSTEXPR write_int_data(int num_digits, unsigned prefix,
                               const basic_format_specs<Char>& specs)
      : size((prefix >> 24) + to_unsigned(num_digits)), padding(0) {
    if (specs.align == align::numeric) {
      auto width = to_unsigned(specs.width);
      if (width > size) {
        padding = width - size;
        size = width;
      }
    } else if (specs.precision > num_digits) {
      size = (prefix >> 24) + to_unsigned(specs.precision);
      padding = to_unsigned(specs.precision - num_digits);
    }
  }
};

// Writes an integer in the format
//   <left-padding><prefix><numeric-padding><digits><right-padding>
// where <digits> are written by write_digits(it).
// prefix contains chars in three lower bytes and the size in the fourth byte.
template <typename OutputIt, typename Char, typename W>
FMT_CONSTEXPR FMT_INLINE auto write_int(OutputIt out, int num_digits,
                                        unsigned prefix,
                                        const basic_format_specs<Char>& specs,
                                        W write_digits) -> OutputIt {
  // Slightly faster check for specs.width == 0 && specs.precision == -1.
  if ((specs.width | (specs.precision + 1)) == 0) {
    auto it = reserve(out, to_unsigned(num_digits) + (prefix >> 24));
    if (prefix != 0) {
      for (unsigned p = prefix & 0xffffff; p != 0; p >>= 8)
        *it++ = static_cast<Char>(p & 0xff);
    }
    return base_iterator(out, write_digits(it));
  }
  auto data = write_int_data<Char>(num_digits, prefix, specs);
  return write_padded<align::right>(
      out, specs, data.size, [=](reserve_iterator<OutputIt> it) {
        for (unsigned p = prefix & 0xffffff; p != 0; p >>= 8)
          *it++ = static_cast<Char>(p & 0xff);
        it = detail::fill_n(it, data.padding, static_cast<Char>('0'));
        return write_digits(it);
      });
}

template <typename Char> class digit_grouping {
 private:
  thousands_sep_result<Char> sep_;

  struct next_state {
#if FMT_USE_LOCALE_GROUPING
    std::string::const_iterator group;
#endif
    int pos;
  };