NAME

stdc_count_ones, stdc_count_ones_uc, stdc_count_ones_us, stdc_count_ones_ui, stdc_count_ones_ul, stdc_count_ones_ull — count one bits

SYNOPSIS

#include <sys/stdbit.h>

unsigned int
stdc_count_ones(generic_value_type value);

unsigned int
stdc_count_ones_uc(unsigned char value);

unsigned int
stdc_count_ones_us(unsigned short value);

unsigned int
stdc_count_ones_ui(unsigned int value);

unsigned int
stdc_count_ones_ul(unsigned long value);

unsigned int
stdc_count_ones_ull(unsigned long long value);

DESCRIPTION

The stdc_count_ones() family of functions returns the number of one bits present in value. These functions are sometimes referred to as a population count.

The stdc_count_ones() function is generic and will operate on all 8, 16, 32, and 64-bit unsigned integers; however, it is only available in C23. The other functions all operate on a specific integer type, but otherwise behave the same and are available regardless of the C language version.

CONTEXT

These functions may be called from user, kernel, or interrupt context.

RETURN VALUES

The functions in the stdc_count_ones() family always return the number of one bits in value. These functions cannot fail.

INTERFACE STABILITY

Committed