Function utf32_to_punycode

test-app/runtime/src/main/cpp/ada/ada.cpp:8149–8208

}

bool utf32_to_punycode(std::u32string_view input, std::string &out) {
  out.reserve(input.size() + out.size());
  uint32_t n = initial_n;
  int32_t d = 0;
  int32_t bias = initial_bias;
  size_t h = 0;
  // first push the ascii content
  for (uint32_t c : input) {
    if (c < 0x80) {
      ++h;
      out.push_back(char(c));
    }
    if (c > 0x10ffff || (c >= 0xd800 && c < 0xe000)) {
      return false;
    }
  }
  size_t b = h;
  if (b > 0) {
    out.push_back('-');
  }
  while (h < input.size()) {
    uint32_t m = 0x10FFFF;
    for (auto code_point : input) {
      if (code_point >= n && code_point < m) m = code_point;
    }

    if ((m - n) > (0x7fffffff - d) / (h + 1)) {
      return false;
    }
    d = d + int32_t((m - n) * (h + 1));
    n = m;
    for (auto c : input) {
      if (c < n) {
        if (d == 0x7fffffff) {
          return false;
        }
        ++d;
      }
      if (c == n) {
        int32_t q = d;
        for (int32_t k = base;; k += base) {
          int32_t t = k <= bias ? tmin : k >= bias + tmax ? tmax : k - bias;

          if (q < t) {
            break;
          }
          out.push_back(digit_to_char(t + ((q - t) % (base - t))));
          q = (q - t) / (base - t);
        }
        out.push_back(digit_to_char(q));
        bias = adapt(d, int32_t(h + 1), h == b);
        d = 0;
        ++h;
      }
    }
    ++d;
    ++n;
  }