Function tryFormatPowerOfTwo

libsolutil/StringUtils.cpp:127–154

Try to format as N * 2**x

/// Try to format as N * 2**x
std::optional<std::string> tryFormatPowerOfTwo(bigint const& _value)
{
	bigint prefix = _value;

	// when multiple trailing zero bytes, format as N * 2**x
	int i = 0;
	for (; (prefix & 0xff) == 0; prefix >>= 8)
		++i;
	if (i <= 2)
		return std::nullopt;

	// 0x100 yields 2**8 (N is 1 and redundant)
	if (prefix == 1)
		return {fmt::format("2**{}", i * 8)};
	else if ((prefix & (prefix - 1)) == 0)
	{
		int j = 0;
		for (; (prefix & 0x1) == 0; prefix >>= 1)
			j++;
		return {fmt::format("2**{}", i * 8 + j)};
	}
	else
		return {fmt::format(
			"{} * 2**{}",
			toHex(toCompactBigEndian(prefix), HexPrefix::Add, HexCase::Mixed),
			i * 8
		)};
}

}