auto x = static_cast<std::uint64_t>(what);

std::string result;

result.reserve(11);

// don't read characters before we found the leading 0xF

// first four bits set?

bool read_chars = ((x & 0xF000000000000000) >> 60) == 0xF;

std::uint64_t mask = 0x0FC0000000000000;

for (int bitshift = 54; bitshift >= 0; bitshift -= 6, mask >>= 6) {

if (read_chars) {

result += detail::decoding_table[(x & mask) >> bitshift];

}

else if (((x & mask) >> bitshift) == 0xF) {

read_chars = true;

}

}

return result;