Function parse_align

extlibs/fmt/include/fmt/format.h:2413–2453

// Parses fill and alignment.
template <typename Char, typename Handler>
FMT_CONSTEXPR const Char* parse_align(const Char* begin, const Char* end,
                                      Handler&& handler) {
  FMT_ASSERT(begin != end, "");
  auto align = align::none;
  auto p = next_code_point(begin, end);
  if (p == end) p = begin;
  for (;;) {
    switch (static_cast<char>(*p)) {
    case '<':
      align = align::left;
      break;
    case '>':
      align = align::right;
      break;
#if FMT_NUMERIC_ALIGN
    case '=':
      align = align::numeric;
      break;
#endif
    case '^':
      align = align::center;
      break;
    }
    if (align != align::none) {
      if (p != begin) {
        auto c = *begin;
        if (c == '{')
          return handler.on_error("invalid fill character '{'"), begin;
        handler.on_fill(basic_string_view<Char>(begin, to_unsigned(p - begin)));
        begin = p + 1;
      } else
        ++begin;
      handler.on_align(align);
      break;
    } else if (p == begin) {
      break;
    }
    p = begin;
  }
  return begin;
}

template <typename Char, typename Handler>
FMT_CONSTEXPR const Char* parse_width(const Char* begin, const Char* end,