NAME
stdc_count_zeros – count the zeros in an integer
SYNOPSIS
Standard C Library (libc, -lc)
#include <stdbit.h>
unsigned int
stdc_count_zeros_uc(unsigned char value);
unsigned int
stdc_count_zeros_us(unsigned short value);
unsigned int
stdc_count_zeros_ui(unsigned int value);
unsigned int
stdc_count_zeros_ul(unsigned long value);
unsigned int
stdc_count_zeros_ull(unsigned long long value);
unsigned int
stdc_count_zeros(value);
DESCRIPTION
The stdc_count_zeros_type() family of functions returns the number of bits set to 0 in value, where value is of type unsigned char, unsigned short, unsigned int, unsigned long, or unsigned long long for type being uc, us, ui, ul, or ull respectively. This is also known as the “population count” (popcount) or “Hamming weight” of the complement of value. The stdc_count_zeros(value) type-generic macro picks the appropriate stdc_count_zeros_type() function based on the type of value.
RETURN VALUES
Returns the number of bits set to 0 in value.
SEE ALSO
STANDARDS
The stdc_count_zeros_type() family of functions and the stdc_count_zeros() type-generic macro conform to ISO/IEC 9899:2024 (“ISO C23”).
HISTORY
The stdc_count_zeros_type() family of functions and the stdc_count_zeros() type-generic macro were added in FreeBSD 15.1.
AUTHORS
Robert Clausecker ⟨[email protected]⟩