Function ToChars

cpp/src/arrow/util/string.h:125–146

/// and might also be faster.
template <typename T, typename... Args>
std::string ToChars(T value, Args&&... args) {
  if constexpr (!have_to_chars<T>) {
    // Some C++ standard libraries do not yet implement std::to_chars for all types,
    // in which case we have to fallback to std::string.
    return std::to_string(value);
  } else {
    // According to various sources, the GNU libstdc++ and Microsoft's C++ STL
    // allow up to 15 bytes of small string optimization, while clang's libc++
    // goes up to 22 bytes. Choose the pessimistic value.
    std::string out(15, 0);
    auto res = std::to_chars(&out.front(), &out.back(), value, args...);
    while (res.ec != std::errc{}) {
      assert(res.ec == std::errc::value_too_large);
      out.resize(out.capacity() * 2);
      res = std::to_chars(&out.front(), &out.back(), value, args...);
    }
    const auto length = res.ptr - out.data();
    assert(length <= static_cast<int64_t>(out.length()));
    out.resize(length);
    return out;
  }
}

#else  // !__has_include(<charconv>)