opnsense-src/lib/libc/stdbit/stdc_first_trailing_zero.3
Robert Clausecker 27de6568a3 libc/stdbit: add man pages for stdbit functions
This adds man pages for each group of functions in <stdbit.h>.
The man pages have cross references to one-another.
Cross references from external man pages to these will be added
in a later commit.

Reviewed by:	pauamma@gundo.com, kib
Approved by:	markj (mentor)
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D53659

(cherry picked from commit d790b16bbf0c3055ef00200d01659dfb3c0e5e5e)
2026-01-01 21:57:32 +01:00

93 lines
2.1 KiB
Groff

.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_FIRST_TRAILING_ZERO 3
.Os
.Sh NAME
.Nm stdc_first_trailing_zero
.Nd find the first trailing zero in an integer
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft unsigned int
.Fn stdc_first_trailing_zero_uc "unsigned char value"
.Ft unsigned int
.Fn stdc_first_trailing_zero_us "unsigned short value"
.Ft unsigned int
.Fn stdc_first_trailing_zero_ui "unsigned int value"
.Ft unsigned int
.Fn stdc_first_trailing_zero_ul "unsigned long value"
.Ft unsigned int
.Fn stdc_first_trailing_zero_ull "unsigned long long value"
.Ft unsigned int
.Fn stdc_first_trailing_zero "value"
.Sh DESCRIPTION
The
.Nm stdc_first_trailing_zero_ Ns Em type Ns ()
family of functions returns the index of the least significant clear bit in
.Fa value ,
where
.Fa value
is of type
.Va unsigned char ,
.Va unsigned short ,
.Va unsigned int ,
.Va unsigned long ,
or
.Va unsigned long long
for
.Em type
being
.Sy uc ,
.Sy us ,
.Sy ui ,
.Sy ul ,
or
.Sy ull
respectively.
The
.Fn stdc_first_trailing_zero "value"
type-generic macro picks the appropriate
.Nm stdc_first_trailing_zero_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Sh RETURN VALUES
Returns the index of the least significant clear bit in
.Fa value .
The bits are numbered such that the least significant bit has number\~1,
and the most significant bit has number
.Ms w
where
.Ms w
is the number of bits in the type of
.Fa value .
If no bits are clear in
.Fa value
(i.\^e.\&
.Fa value
is the bitwise complement of zero), zero is returned.
.Sh SEE ALSO
.Xr bit_ffc 3 ,
.Xr stdbit 3 ,
.Xr stdc_trailing_ones 3 ,
.Xr stdc_first_trailing_ones 3 ,
.Xr stdc_first_leading_zero 3
.Sh STANDARDS
The
.Nm stdc_first_trailing_zero_ Ns Em type Ns ()
family of functions and the
.Fn stdc_first_trailing_zero
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_first_trailing_zero_ Ns Em type Ns ()
family of functions and the
.Fn stdc_first_trailing_zero
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org