< cpp‎ | numeric
Defined in header <bit>
template< class T >
constexpr T log2p1(T x) noexcept;
(since C++20)

If x is not zero, calculates the number of bits needed to store the value x, that is, 1 + floor(log
. If x is zero, returns zero.

This overload only participates in overload resolution if T is an unsigned integer type (that is, unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long, or an extended unsigned integer type).

Return value

Zero if x is zero; otherwise, one plus the base-2 logarithm of x, with any fractional part discarded.