NAME

stdc_bit_floor, stdc_bit_floor_uc, stdc_bit_floor_us, stdc_bit_floor_ui, stdc_bit_floor_ul, stdc_bit_floor_ull — find largest power of 2 smaller than value

SYNOPSIS

#include <sys/stdbit.h>

generic_value_type
stdc_bit_floor(generic_value_type value);

unsigned char
stdc_bit_floor_uc(unsigned char value);

unsigned short
stdc_bit_floor_us(unsigned short value);

unsigned int
stdc_bit_floor_ui(unsigned int value);

unsigned long
stdc_bit_floor_ul(unsigned long value);

unsigned long long
stdc_bit_floor_ull(unsigned long long value);

DESCRIPTION

The stdc_bit_floor() family of functions determine the largest power of 2 that is not greater than value. If value is 0, then the function returns 0.

The stdc_bit_floor() 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_floor() family returns the largest power of 2 that is not greater than value. These functions cannot fail.

INTERFACE STABILITY

Committed