std::log2p1

 

C++

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bit_cast (C++20)

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log2p1 (C++20)

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countl_zero (C++20)

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countr_zero (C++20)

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popcount (C++20)

endian (C++20)

 

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, \(1 + \lfloor log_2(x) \rfloor\)1 + floor(log
2(x)). 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.

Notes

This function is equivalent to return std::numeric_limits<T>::digits - std::countl_zero(x);.

See also

countl_zero (C++20)

counts the number of consecutive 0 bits, starting from the most significant bit (function template)