bit

A workaround for __cpp_lib_bitops for gcc version 9.x (in C++20 mode). Those versions implemented std::countl_zero, etc, but did not define that feature detection macro. More...

Collaboration diagram for bit:

Enumerations
enum class	std::endian { std::little = __ORDER_LITTLE_ENDIAN__ , std::big = __ORDER_BIG_ENDIAN__ , std::native = __BYTE_ORDER__ }
	Indicates the endianness of all scalar types. More...

Functions
template<class T >
constexpr T	std::bit_ceil (T x) noexcept
	Calculates the smallest integral power of two that is not smaller than x. More...
template<class T >
constexpr T	std::bit_width (T x) noexcept
	If x is not zero, calculates the number of bits needed to store the value x, that is, 1 + floor(log2(x)). If x is zero, returns zero. More...
template<class T >
constexpr int	std::countl_zero (T x) noexcept
	Returns the number of consecutive 0 bits in the value of x, starting from the most significant bit ("left"). More...
template<class T >
constexpr int	std::countr_zero (T x) noexcept
	Returns the number of consecutive 0 bits in the value of x, starting from the least significant bit ("right"). More...
template<class T >
constexpr bool	std::has_single_bit (T x) noexcept
	Checks if x is an integral power of two. More...
template<class T >
constexpr int	std::popcount (T x) noexcept
	Returns the number of 1 bits in the value of x. More...

Detailed Descriptionno-api

A workaround for __cpp_lib_bitops for gcc version 9.x (in C++20 mode). Those versions implemented std::countl_zero, etc, but did not define that feature detection macro.

This defines __cpp_lib_int_pow2. Note: g++-9.3 -std=c++2a on ubuntu 20.04 did #define __cpp_lib_int_pow2 201806L, which is an older implementation of the __cpp_lib_int_pow2 proposal.

See also

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0556r3.html (__cpp_lib_int_pow2 >= 201806L)

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p1956r1.pdf (__cpp_lib_int_pow2 >= 202002L)

A workaround for __cpp_lib_endian for gcc version 8.x (in C++20 mode). Those versions implemented std::endian, but did not define that feature detection macro.

The <bit> header from C++20's standard library.

Enumeration Type Documentation

endian

enum std::endian

no-apistrong

Indicates the endianness of all scalar types.

See also

https://en.cppreference.com/w/cpp/types/endian

Enumerator
little	implementation-defined
big	implementation-defined
native	implementation-defined

Function Documentation

bit_ceil()

template<class T >

constexpr T std::bit_ceil ( T  x )

no-apiconstexprnoexcept

Calculates the smallest integral power of two that is not smaller than x.

See also

https://en.cppreference.com/w/cpp/numeric/bit_ceil

bit_width()

template<class T >

constexpr T std::bit_width ( T  x )

no-apiconstexprnoexcept

If x is not zero, calculates the number of bits needed to store the value x, that is, 1 + floor(log2(x)). If x is zero, returns zero.

See also

https://en.cppreference.com/w/cpp/numeric/bit_width

countl_zero()

template<class T >

constexpr int std::countl_zero ( T  x )

no-apiconstexprnoexcept

Returns the number of consecutive 0 bits in the value of x, starting from the most significant bit ("left").

See also

https://en.cppreference.com/w/cpp/numeric/countl_zero

countr_zero()

template<class T >

constexpr int std::countr_zero ( T  x )

no-apiconstexprnoexcept

Returns the number of consecutive 0 bits in the value of x, starting from the least significant bit ("right").

See also

https://en.cppreference.com/w/cpp/numeric/countr_zero

has_single_bit()

template<class T >

constexpr bool std::has_single_bit ( T  x )

no-apiconstexprnoexcept

Checks if x is an integral power of two.

See also

https://en.cppreference.com/w/cpp/numeric/has_single_bit

popcount()

template<class T >

constexpr int std::popcount ( T  x )

no-apiconstexprnoexcept

Returns the number of 1 bits in the value of x.

See also

https://en.cppreference.com/w/cpp/numeric/popcount