std::countl_zero

 

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Defined in header <bit>
template< class T > constexpr int countl_zero( T x ) noexcept;		(since C++20)

See More

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

Parameters

x	-	a value whose bits to count
Type requirements
T	-	must be an unsigned integer type (that is, unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long, or an extended unsigned integer type) in order to participate in overload resolution.

Return value

The number of consecutive 0 bits in the value of x, starting from the most significant bit.

Notes

Feature-test macro	Value	Std	Feature
__cpp_lib_bitops	201907L	(C++20)	Bit operations

Example

Run this code

#include <bit>
#include <bitset>
#include <cstdint>
#include <iostream>

int main()
{
    for (const std::uint8_t i : {0, 0b11111111, 0b11110000, 0b00011110})
        std::cout << "countl_zero( " << std::bitset<8>(i) << " ) = "
                  << std::countl_zero(i) << '\n';
}

Output:

countl_zero( 00000000 ) = 8
countl_zero( 11111111 ) = 0
countl_zero( 11110000 ) = 0
countl_zero( 00011110 ) = 3

See also

countl_one (C++20)	counts the number of consecutive 1 bits, starting from the most significant bit (function template)
countr_zero (C++20)	counts the number of consecutive 0 bits, starting from the least significant bit (function template)
countr_one (C++20)	counts the number of consecutive 1 bits, starting from the least significant bit (function template)
popcount (C++20)	counts the number of 1 bits in an unsigned integer (function template)
allanynone	checks if all, any or none of the bits are set to true (public member function of std::bitset<N>)
C documentation for stdc_leading_zeros