Tribblix: manual page: stdc_count

STDC_COUNT_ZEROS(3C) Standard C Library Functions STDC_COUNT_ZEROS(3C)

NAME

stdc_count_zeros, stdc_count_zeros_uc, stdc_count_zeros_us,
stdc_count_zeros_ui, stdc_count_zeros_ul, stdc_count_zeros_ull - count
zero bits

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <stdbit.h>

unsigned int
stdc_count_zeros(generic_value_type value);

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);

DESCRIPTION

The stdc_count_zeros() family of functions returns the number of zero
bits present in value.

The stdc_count_zeros() 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.

Note that if an unsigned integer is promoted, it will always be filled
with leading zeros, increasing the return value.

RETURN VALUES

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

EXAMPLES

Example 1 Printing the total number of zero bits.

#include <stdbit.h>
#include <stdio.h>
#include <limits.h>

int
main(void)
{
printf("0x%x 0x%x 0x%x 0x%x\n",
stdc_count_zeros_uc(0x23),
stdc_count_zeros_us(0x7777),
stdc_count_zeros_ui(UINT32_MAX),
stdc_count_zeros_ull(0));
return (0);
}

When compiled and run, this produces:

$ ./a.out
0x5 0x4 0x0 0x40

INTERFACE STABILITY

Committed

MT-LEVEL
Async-Signal-Safe