Function write_int

include/fmt/format.h:1963–2008

// Writes a decimal integer with digit grouping.
template <typename OutputIt, typename UInt, typename Char>
auto write_int(OutputIt out, UInt value, unsigned prefix,
               const format_specs& specs, const digit_grouping<Char>& grouping)
    -> OutputIt {
  static_assert(std::is_same<uint64_or_128_t<UInt>, UInt>::value, "");
  int num_digits = 0;
  auto buffer = memory_buffer();
  switch (specs.type()) {
  default: FMT_ASSERT(false, ""); FMT_FALLTHROUGH;
  case presentation_type::none:
  case presentation_type::dec:
    num_digits = count_digits(value);
    format_decimal<char>(appender(buffer), value, num_digits);
    break;
  case presentation_type::hex:
    if (specs.alt())
      prefix_append(prefix, unsigned(specs.upper() ? 'X' : 'x') << 8 | '0');
    num_digits = count_digits<4>(value);
    format_base2e<char>(4, appender(buffer), value, num_digits, specs.upper());
    break;
  case presentation_type::oct:
    num_digits = count_digits<3>(value);
    // Octal prefix '0' is counted as a digit, so only add it if precision
    // is not greater than the number of digits.
    if (specs.alt() && specs.precision <= num_digits && value != 0)
      prefix_append(prefix, '0');
    format_base2e<char>(3, appender(buffer), value, num_digits);
    break;
  case presentation_type::bin:
    if (specs.alt())
      prefix_append(prefix, unsigned(specs.upper() ? 'B' : 'b') << 8 | '0');
    num_digits = count_digits<1>(value);
    format_base2e<char>(1, appender(buffer), value, num_digits);
    break;
  case presentation_type::chr:
    return write_char<Char>(out, static_cast<Char>(value), specs);
  }

  unsigned size = (prefix != 0 ? prefix >> 24 : 0) + to_unsigned(num_digits) +
                  to_unsigned(grouping.count_separators(num_digits));
  return write_padded<Char, align::right>(
      out, specs, size, size, [&](reserve_iterator<OutputIt> it) {
        for (unsigned p = prefix & 0xffffff; p != 0; p >>= 8)
          *it++ = static_cast<Char>(p & 0xff);
        return grouping.apply(it, string_view(buffer.data(), buffer.size()));
      });
}

#if FMT_USE_LOCALE
// Writes a localized value.