Tribblix: manual page: stdc_first_trailing_zero

STDC_FIRST_TRAILING_ZERO(9F) Kernel Functions for Drivers

NAME

stdc_first_trailing_zero, stdc_first_trailing_zero_uc,
stdc_first_trailing_zero_us, stdc_first_trailing_zero_ui,
stdc_first_trailing_zero_ul, stdc_first_trailing_zero_ull - find index
of least significant zero bit

SYNOPSIS

#include <sys/stdbit.h>

unsigned int
stdc_first_trailing_zero(generic_value_type value);

unsigned int
stdc_first_trailing_zero_uc(unsigned char value);

unsigned int
stdc_first_trailing_zero_us(unsigned short value);

unsigned int
stdc_first_trailing_zero_ui(unsigned int value);

unsigned int
stdc_first_trailing_zero_ul(unsigned long value);

unsigned int
stdc_first_trailing_zero_ull(unsigned long long value);

DESCRIPTION

The stdc_first_trailing_zero() family of functions returns the 1s-based
index of the first zero bit in value starting at the least significant
bit. If there is no zero bit in value then zero is returned.

The stdc_first_trailing_zero() 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_first_trailing_zero() family always return
the index of the first trailing zero bit in value plus one. Otherwise,
if there are no zero bits in value, 0 will be returned. These
functions cannot fail.

INTERFACE STABILITY