illumos: manual page: stdc_bit

STDC_BIT_WIDTH(9F) Kernel Functions for Drivers STDC_BIT_WIDTH(9F)

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

SYNOPSIS

#include <sys/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.

CONTEXT

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

RETURN VALUES

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

INTERFACE STABILITY