Tribblix: manual page: stdc_bit

STDC_BIT_WIDTH(3C) Standard C Library Functions STDC_BIT_WIDTH(3C)

NAME

stdc_bit_width, stdc_bit_width_uc, stdc_bit_width_us,
stdc_bit_width_ui, stdc_bit_width_ul, stdc_bit_width_ull - determine
minimum bit width

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <stdbit.h>

unsigned int
stdc_bit_width(generic_value_type value);

unsigned int
stdc_bit_width_uc(unsigned char value);

unsigned int
stdc_bit_width_us(unsigned short value);

unsigned int
stdc_bit_width_ui(unsigned int value);

unsigned int
stdc_bit_width_ul(unsigned long value);

unsigned int
stdc_bit_width_ull(unsigned long long value);

DESCRIPTION

The stdc_bit_width() family of functions returns the minimum number of
bits required to store value. This is calculated by taking the log
base 2 of value and adding 1; however, if value is 0, then the function
returns 0. The stdc_bit_width() 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.

RETURN VALUES

The functions in the stdc_bit_width() family returns the minimum number
of bits required to hold value. These functions cannot fail.

EXAMPLES

Example 1 Printing the minimum bit width.

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

int
main(void)
{
printf("0x%x 0x%x 0x%x 0x%x\n",
stdc_bit_width_uc(0x95),
stdc_bit_width_us(0xff6),
stdc_bit_width_ui(UINT32_MAX),
stdc_bit_width_ull(0));
return (0);
}

When compiled and run, this produces:

$ ./a.out
0x8 0xc 0x20 0x0

INTERFACE STABILITY

Committed

MT-LEVEL
Async-Signal-Safe