illumos: manual page: stdc_bit

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

NAME

stdc_bit_ceil, stdc_bit_ceil_uc, stdc_bit_ceil_us, stdc_bit_ceil_ui,
stdc_bit_ceil_ul, stdc_bit_ceil_ull - find smallest power of 2 not less
than value

SYNOPSIS

#include <sys/stdbit.h>

generic_value_type
stdc_bit_ceil(generic_value_type value);

unsigned char
stdc_bit_ceil_uc(unsigned char value);

unsigned short
stdc_bit_ceil_us(unsigned short value);

unsigned int
stdc_bit_ceil_ui(unsigned int value);

unsigned long
stdc_bit_ceil_ul(unsigned long value);

unsigned long long
stdc_bit_ceil_ull(unsigned long long value);

DESCRIPTION

The stdc_bit_ceil() family of functions finds the smallest power of 2 that
is not less than value. If the resulting value would not fit in the type,
then 0 is returned. For example, if one were to use UINT8_MAX with
stdc_bit_ceil_uc() the next power of two would be 0x100, which is larger
than would fit in an 8-bit unsigned char, resulting in 0.

The stdc_bit_ceil() 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_ceil() family returns the smallest power of 2
that is not less than value. These functions cannot fail.

INTERFACE STABILITY