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libc/stdbit: add man pages for stdbit functions

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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
This commit is contained in:
Robert Clausecker
2025-11-18 18:31:07 +01:00
parent d39e310c7d
commit d790b16bbf
15 changed files with 1283 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/libc/stdbit/Makefile.inc
+15
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@@ -17,3 +17,18 @@ SRCS+= stdc_bit_ceil.c \
stdc_trailing_zeros.c
SYM_MAPS+=${LIBC_SRCTOP}/stdbit/Symbol.map
MAN+= stdc_bit_ceil.3 \
stdc_bit_floor.3 \
stdc_bit_width.3 \
stdc_count_ones.3 \
stdc_count_zeros.3 \
stdc_first_leading_one.3 \
stdc_first_leading_zero.3 \
stdc_first_trailing_one.3 \
stdc_first_trailing_zero.3 \
stdc_has_single_bit.3 \
stdc_leading_ones.3 \
stdc_leading_zeros.3 \
stdc_trailing_ones.3 \
stdc_trailing_zeros.3
lib/libc/stdbit/stdc_bit_ceil.3
+81
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@@ -0,0 +1,81 @@
.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_BIT_CEIL 3
.Os
.Sh NAME
.Nm stdc_bit_ceil
.Nd round up to the next power of\~2
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft unsigned char
.Fn stdc_bit_ceil_uc "unsigned char value"
.Ft unsigned short
.Fn stdc_bit_ceil_us "unsigned short value"
.Ft unsigned int
.Fn stdc_bit_ceil_ui "unsigned int value"
.Ft unsigned long
.Fn stdc_bit_ceil_ul "unsigned long value"
.Ft unsigned long long
.Fn stdc_bit_ceil_ull "unsigned long long value"
.Ft typeof Ns Pq Em value
.Fn stdc_bit_ceil "value"
.Sh DESCRIPTION
The
.Nm stdc_bit_ceil_ Ns Em type Ns ()
family of functions rounds
.Fa value
up to the next power of\~2, 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_bit_ceil "value"
type-generic macro picks the appropriate
.Nm stdc_bit_ceil_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Sh RETURN VALUES
Returns
.Fa value
round up to the next power of\~2.
If this value is not representable,
0\~is returned.
.Sh SEE ALSO
.Xr stdbit 3 ,
.Xr stdc_bit_floor 3
.Sh STANDARDS
The
.Nm stdc_bit_ceil_ Ns Em type Ns ()
family of functions and the
.Fn stdc_bit_ceil
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_bit_ceil_ Ns Em type Ns ()
family of functions and the
.Fn stdc_bit_ceil
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org
lib/libc/stdbit/stdc_bit_floor.3
+83
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@@ -0,0 +1,83 @@
.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_BIT_FLOOR 3
.Os
.Sh NAME
.Nm stdc_bit_floor
.Nd round down to the previous power of\~2
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft unsigned char
.Fn stdc_bit_floor_uc "unsigned char value"
.Ft unsigned short
.Fn stdc_bit_floor_us "unsigned short value"
.Ft unsigned int
.Fn stdc_bit_floor_ui "unsigned int value"
.Ft unsigned long
.Fn stdc_bit_floor_ul "unsigned long value"
.Ft unsigned long long
.Fn stdc_bit_floor_ull "unsigned long long value"
.Ft typeof Ns Pq Em value
.Fn stdc_bit_floor "value"
.Sh DESCRIPTION
The
.Nm stdc_bit_floor_ Ns Em type Ns ()
family of functions rounds
.Fa value
down to the previous power of\~2, 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_bit_floor "value"
type-generic macro picks the appropriate
.Nm stdc_bit_floor_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Sh RETURN VALUES
Returns
.Fa value
round down to the previous power of\~2.
If
.Fa value
is equal to zero,
zero is returned.
.Sh SEE ALSO
.Xr stdbit 3 ,
.Xr stdc_bit_ceil 3
.Sh STANDARDS
The
.Nm stdc_bit_floor_ Ns Em type Ns ()
family of functions and the
.Fn stdc_bit_floor
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_bit_floor_ Ns Em type Ns ()
family of functions and the
.Fn stdc_bit_floor
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org
lib/libc/stdbit/stdc_bit_width.3
+104
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@@ -0,0 +1,104 @@
.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_BIT_WIDTH 3
.Os
.Sh NAME
.Nm stdc_bit_width
.Nd find the first trailing one in an intege
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft unsigned int
.Fn stdc_bit_width_uc "unsigned char value"
.Ft unsigned int
.Fn stdc_bit_width_us "unsigned short value"
.Ft unsigned int
.Fn stdc_bit_width_ui "unsigned int value"
.Ft unsigned int
.Fn stdc_bit_width_ul "unsigned long value"
.Ft unsigned int
.Fn stdc_bit_width_ull "unsigned long long value"
.Ft unsigned int
.Fn stdc_bit_width "value"
.Sh DESCRIPTION
The
.Nm stdc_bit_width_ Ns Em type Ns ()
family of functions returns the number of bits needed to represent
.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_bit_width "value"
type-generic macro picks the appropriate
.Nm stdc_bit_width_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Pp
Functions
.Fn stdc_bit_width_ui ,
.Fn stdc_bit_width_ul ,
and
.Fn stdc_bit_width_ull
are identical to
.Bx 4.3
functions
.Xr fls 3 ,
.Xr flsl 3 ,
and
.Xr flsll 3
respectively, except for operating on unsigned instead of signed values.
.Sh RETURN VALUES
Returns the least number of bits needed to represent
.Fa value .
If
.Fa value
is zero, the return value is zero.
Otherwise it is
.EQ
1 + \(lf log sub 2 italic value \(rf .
.EN
.Sh SEE ALSO
.Xr bit_fls 3 ,
.Xr fls 3 ,
.Xr flsl 3 ,
.Xr flsll 3 ,
.Xr stdbit 3 ,
.Xr stdc_count_leading_zeros 3 ,
.Xr stdc_first_leading_one 3
.Sh STANDARDS
The
.Nm stdc_bit_width_ Ns Em type Ns ()
family of functions and the
.Fn stdc_bit_width
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_bit_width_ Ns Em type Ns ()
family of functions and the
.Fn stdc_bit_width
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org
lib/libc/stdbit/stdc_count_ones.3
+85
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@@ -0,0 +1,85 @@
.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_COUNT_ONES 3
.Os
.Sh NAME
.Nm stdc_count_ones
.Nd count the ones in an integer
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft unsigned int
.Fn stdc_count_ones_uc "unsigned char value"
.Ft unsigned int
.Fn stdc_count_ones_us "unsigned short value"
.Ft unsigned int
.Fn stdc_count_ones_ui "unsigned int value"
.Ft unsigned int
.Fn stdc_count_ones_ul "unsigned long value"
.Ft unsigned int
.Fn stdc_count_ones_ull "unsigned long long value"
.Ft unsigned int
.Fn stdc_count_ones "value"
.Sh DESCRIPTION
The
.Nm stdc_count_ones_ Ns Em type Ns ()
family of functions returns the number of bits set to\~1 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.
This is also known as the
.Dq population count
(popcount) or
.Dq Hamming weight
operation.
The
.Fn stdc_count_ones "value"
type-generic macro picks the appropriate
.Nm stdc_count_ones_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Sh RETURN VALUES
Returns the number of bits set to\~1 in
.Fa value .
.Sh SEE ALSO
.Xr bit_count 3 ,
.Xr stdbit 3 ,
.Xr stdc_count_zeros 3 ,
.Xr stdc_has_single_bit 3
.Sh STANDARDS
The
.Nm stdc_count_ones_ Ns Em type Ns ()
family of functions and the
.Fn stdc_count_ones
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_count_ones_ Ns Em type Ns ()
family of functions and the
.Fn stdc_count_ones
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org
lib/libc/stdbit/stdc_count_zeros.3
+84
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@@ -0,0 +1,84 @@
.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_COUNT_ZEROS 3
.Os
.Sh NAME
.Nm stdc_count_zeros
.Nd count the zeros in an integer
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft unsigned int
.Fn stdc_count_zeros_uc "unsigned char value"
.Ft unsigned int
.Fn stdc_count_zeros_us "unsigned short value"
.Ft unsigned int
.Fn stdc_count_zeros_ui "unsigned int value"
.Ft unsigned int
.Fn stdc_count_zeros_ul "unsigned long value"
.Ft unsigned int
.Fn stdc_count_zeros_ull "unsigned long long value"
.Ft unsigned int
.Fn stdc_count_zeros "value"
.Sh DESCRIPTION
The
.Nm stdc_count_zeros_ Ns Em type Ns ()
family of functions returns the number of bits set to\~0 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.
This is also known as the
.Dq population count
(popcount) or
.Dq Hamming weight
of the complement of
.Fa value .
The
.Fn stdc_count_zeros "value"
type-generic macro picks the appropriate
.Nm stdc_count_zeros_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Sh RETURN VALUES
Returns the number of bits set to\~0 in
.Fa value .
.Sh SEE ALSO
.Xr stdbit 3 ,
.Xr stdc_count_ones 3
.Sh STANDARDS
The
.Nm stdc_count_zeros_ Ns Em type Ns ()
family of functions and the
.Fn stdc_count_zeros
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_count_zeros_ Ns Em type Ns ()
family of functions and the
.Fn stdc_count_zeros
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org
lib/libc/stdbit/stdc_first_leading_one.3
+93
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@@ -0,0 +1,93 @@
.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_FIRST_LEADING_ONE 3
.Os
.Sh NAME
.Nm stdc_first_leading_one
.Nd find the first leading one in an integer
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft unsigned int
.Fn stdc_first_leading_one_uc "unsigned char value"
.Ft unsigned int
.Fn stdc_first_leading_one_us "unsigned short value"
.Ft unsigned int
.Fn stdc_first_leading_one_ui "unsigned int value"
.Ft unsigned int
.Fn stdc_first_leading_one_ul "unsigned long value"
.Ft unsigned int
.Fn stdc_first_leading_one_ull "unsigned long long value"
.Ft unsigned int
.Fn stdc_first_leading_one "value"
.Sh DESCRIPTION
The
.Nm stdc_first_leading_one_ Ns Em type Ns ()
family of functions returns the index of the most significant set 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_leading_one "value"
type-generic macro picks the appropriate
.Nm stdc_first_leading_one_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Sh RETURN VALUES
Returns the index of the most significant set bit in
.Fa value .
The bits are numbered such that the most significant bit has number\~1,
and the least significant bit has number
.Ms w
where
.Ms w
is the number of bits in the type of
.Fa value .
If no bits are set in
.Fa value
(i.\^e.\&
.Fa value
is zero), zero is returned.
.Sh SEE ALSO
.Xr fls 3 ,
.Xr stdbit 3 ,
.Xr stdc_leading_zeros 3 ,
.Xr stdc_first_leading_zero 3 ,
.Xr stdc_first_trailing_one 3
.Sh STANDARDS
The
.Nm stdc_first_leading_one_ Ns Em type Ns ()
family of functions and the
.Fn stdc_first_leading_one
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_first_leading_one_ Ns Em type Ns ()
family of functions and the
.Fn stdc_first_leading_one
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org
lib/libc/stdbit/stdc_first_leading_zero.3
+92
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@@ -0,0 +1,92 @@
.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_FIRST_LEADING_ZERO 3
.Os
.Sh NAME
.Nm stdc_first_leading_zero
.Nd find the first leading zero in an integer
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft unsigned int
.Fn stdc_first_leading_zero_uc "unsigned char value"
.Ft unsigned int
.Fn stdc_first_leading_zero_us "unsigned short value"
.Ft unsigned int
.Fn stdc_first_leading_zero_ui "unsigned int value"
.Ft unsigned int
.Fn stdc_first_leading_zero_ul "unsigned long value"
.Ft unsigned int
.Fn stdc_first_leading_zero_ull "unsigned long long value"
.Ft unsigned int
.Fn stdc_first_leading_zero "value"
.Sh DESCRIPTION
The
.Nm stdc_first_leading_zero_ Ns Em type Ns ()
family of functions returns the index of the most 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_leading_zero "value"
type-generic macro picks the appropriate
.Nm stdc_first_leading_zero_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Sh RETURN VALUES
Returns the index of the most significant clear bit in
.Fa value .
The bits are numbered such that the most significant bit has number\~1,
and the least 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 stdbit 3 ,
.Xr stdc_leading_ones 3 ,
.Xr stdc_first_leading_ones 3 ,
.Xr stdc_first_trailing_zero 3
.Sh STANDARDS
The
.Nm stdc_first_leading_zero_ Ns Em type Ns ()
family of functions and the
.Fn stdc_first_leading_zero
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_first_leading_zero_ Ns Em type Ns ()
family of functions and the
.Fn stdc_first_leading_zero
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org
lib/libc/stdbit/stdc_first_trailing_one.3
+110
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@@ -0,0 +1,110 @@
.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_FIRST_TRAILING_ONE 3
.Os
.Sh NAME
.Nm stdc_first_trailing_one
.Nd find the first trailing one in an integer
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft unsigned int
.Fn stdc_first_trailing_one_uc "unsigned char value"
.Ft unsigned int
.Fn stdc_first_trailing_one_us "unsigned short value"
.Ft unsigned int
.Fn stdc_first_trailing_one_ui "unsigned int value"
.Ft unsigned int
.Fn stdc_first_trailing_one_ul "unsigned long value"
.Ft unsigned int
.Fn stdc_first_trailing_one_ull "unsigned long long value"
.Ft unsigned int
.Fn stdc_first_trailing_one "value"
.Sh DESCRIPTION
The
.Nm stdc_first_trailing_one_ Ns Em type Ns ()
family of functions returns the index of the least significant set 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_one "value"
type-generic macro picks the appropriate
.Nm stdc_first_trailing_one_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Pp
Functions
.Fn stdc_first_trailing_one_ui ,
.Fn stdc_first_trailing_one_ul ,
and
.Fn stdc_first_trailing_one_ull
are identical to
.Bx 4.3
functions
.Xr ffs 3 ,
.Xr ffsl 3 ,
and
.Xr ffsll 3
respectively, except for operating on unsigned instead of signed values.
.Sh RETURN VALUES
Returns the index of the least significant set 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 set in
.Fa value
(i.\^e.\&
.Fa value
is zero), one is returned.
.Sh SEE ALSO
.Xr bit_ffs 3 ,
.Xr ffs 3 ,
.Xr ffsl 3 ,
.Xr ffsll 3 ,
.Xr stdbit 3 ,
.Xr stdc_trailing_zeros 3 ,
.Xr stdc_first_trailing_zero 3 ,
.Xr stdc_first_leading_one 3
.Sh STANDARDS
The
.Nm stdc_first_trailing_one_ Ns Em type Ns ()
family of functions and the
.Fn stdc_first_trailing_one
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_first_trailing_one_ Ns Em type Ns ()
family of functions and the
.Fn stdc_first_trailing_one
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org
lib/libc/stdbit/stdc_first_trailing_zero.3
+93
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@@ -0,0 +1,93 @@
.\"
.\" 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
lib/libc/stdbit/stdc_has_single_bit.3
+98
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@@ -0,0 +1,98 @@
.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_HAS_SINGLE_BIT 3
.Os
.Sh NAME
.Nm stdc_has_single_bit
.Nd check for single bit set
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft bool
.Fn stdc_has_single_bit_uc "unsigned char value"
.Ft bool
.Fn stdc_has_single_bit_us "unsigned short value"
.Ft bool
.Fn stdc_has_single_bit_ui "unsigned int value"
.Ft bool
.Fn stdc_has_single_bit_ul "unsigned long value"
.Ft bool
.Fn stdc_has_single_bit_ull "unsigned long long value"
.Ft bool
.Fn stdc_has_single_bit "value"
.Sh DESCRIPTION
The
.Nm stdc_has_single_bit_ Ns Em type Ns ()
family of functions checks if there is exactly one bit
set 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_has_single_bit "value"
type-generic macro picks the appropriate
.Nm stdc_has_single_bit_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Pp
The functions in this family behave similarly to the
.Fn powerof2 "value"
macro of
.In sys/param.h ,
but differ when
.Fa value
is zero: while
.Fn powerof2
considers zero to be a power of two,
.Fn stdc_has_single_bit
does not.
.Sh RETURN VALUES
Returns
.Sy true
if exactly one bit is set in
.Fa value ,
otherwise returns
.Sy false .
I.\^e. the function determines if
.Fa value
is a power of two.
.Sh SEE ALSO
.Xr stdbit 3 ,
.Xr stdc_count_ones 3
.Sh STANDARDS
The
.Nm stdc_has_single_bit_ Ns Em type Ns ()
family of functions and the
.Fn stdc_has_single_bit
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_has_single_bit_ Ns Em type Ns ()
family of functions and the
.Fn stdc_has_single_bit
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org
lib/libc/stdbit/stdc_leading_ones.3
+86
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@@ -0,0 +1,86 @@
.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_LEADING_ONES 3
.Os
.Sh NAME
.Nm stdc_leading_ones
.Nd find the number of leading ones in an integer
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft unsigned int
.Fn stdc_leading_ones_uc "unsigned char value"
.Ft unsigned int
.Fn stdc_leading_ones_us "unsigned short value"
.Ft unsigned int
.Fn stdc_leading_ones_ui "unsigned int value"
.Ft unsigned int
.Fn stdc_leading_ones_ul "unsigned long value"
.Ft unsigned int
.Fn stdc_leading_ones_ull "unsigned long long value"
.Ft unsigned int
.Fn stdc_leading_ones "value"
.Sh DESCRIPTION
The
.Nm stdc_leading_ones_ Ns Em type Ns ()
family of functions returns the number of leading ones 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_leading_ones "value"
type-generic macro picks the appropriate
.Nm stdc_leading_ones_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Sh RETURN VALUES
Returns the number of leading ones in
.Fa value .
If
.Fa value
is all ones,
the total number of bits in the type of
.Fa value
is returned.
.Sh SEE ALSO
.Xr stdbit 3 ,
.Xr stdc_leading_zeros 3 ,
.Xr stdc_trailing_ones 3 ,
.Xr stdc_first_leading_zero 3
.Sh STANDARDS
The
.Nm stdc_leading_ones_ Ns Em type Ns ()
family of functions and the
.Fn stdc_leading_ones
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_leading_ones_ Ns Em type Ns ()
family of functions and the
.Fn stdc_leading_ones
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org
lib/libc/stdbit/stdc_leading_zeros.3
+86
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@@ -0,0 +1,86 @@
.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_LEADING_ZEROS 3
.Os
.Sh NAME
.Nm stdc_leading_zeros
.Nd find the number of leading zeros in an integer
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft unsigned int
.Fn stdc_leading_zeros_uc "unsigned char value"
.Ft unsigned int
.Fn stdc_leading_zeros_us "unsigned short value"
.Ft unsigned int
.Fn stdc_leading_zeros_ui "unsigned int value"
.Ft unsigned int
.Fn stdc_leading_zeros_ul "unsigned long value"
.Ft unsigned int
.Fn stdc_leading_zeros_ull "unsigned long long value"
.Ft unsigned int
.Fn stdc_leading_zeros "value"
.Sh DESCRIPTION
The
.Nm stdc_leading_zeros_ Ns Em type Ns ()
family of functions returns the number of leading zeros 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_leading_zeros "value"
type-generic macro picks the appropriate
.Nm stdc_leading_zeros_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Sh RETURN VALUES
Returns the number of leading zeros in
.Fa value .
If
.Fa value
is all zeros,
the total number of bits in the type of
.Fa value
is returned.
.Sh SEE ALSO
.Xr stdbit 3 ,
.Xr stdc_leading_ones 3 ,
.Xr stdc_trailing_zeros 3 ,
.Xr stdc_first_leading_one 3
.Sh STANDARDS
The
.Nm stdc_leading_zeros_ Ns Em type Ns ()
family of functions and the
.Fn stdc_leading_zeros
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_leading_zeros_ Ns Em type Ns ()
family of functions and the
.Fn stdc_leading_zeros
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org
lib/libc/stdbit/stdc_trailing_ones.3
+86
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@@ -0,0 +1,86 @@
.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_TRAILING_ONES 3
.Os
.Sh NAME
.Nm stdc_trailing_ones
.Nd find the number of trailing ones in an integer
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft unsigned int
.Fn stdc_trailing_ones_uc "unsigned char value"
.Ft unsigned int
.Fn stdc_trailing_ones_us "unsigned short value"
.Ft unsigned int
.Fn stdc_trailing_ones_ui "unsigned int value"
.Ft unsigned int
.Fn stdc_trailing_ones_ul "unsigned long value"
.Ft unsigned int
.Fn stdc_trailing_ones_ull "unsigned long long value"
.Ft unsigned int
.Fn stdc_trailing_ones "value"
.Sh DESCRIPTION
The
.Nm stdc_trailing_ones_ Ns Em type Ns ()
family of functions returns the number of trailing ones 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_trailing_ones "value"
type-generic macro picks the appropriate
.Nm stdc_trailing_ones_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Sh RETURN VALUES
Returns the number of trailing ones in
.Fa value .
If
.Fa value
is all ones,
the total number of bits in the type of
.Fa value
is returned.
.Sh SEE ALSO
.Xr stdbit 3 ,
.Xr stdc_leading_ones 3 ,
.Xr stdc_trailing_zeros 3 ,
.Xr stdc_first_trailing_zero 3
.Sh STANDARDS
The
.Nm stdc_trailing_ones_ Ns Em type Ns ()
family of functions and the
.Fn stdc_trailing_ones
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_trailing_ones_ Ns Em type Ns ()
family of functions and the
.Fn stdc_trailing_ones
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org
lib/libc/stdbit/stdc_trailing_zeros.3
+87
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@@ -0,0 +1,87 @@
.\"
.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd November 9, 2025
.Dt STDC_TRAILING_ZEROS 3
.Os
.Sh NAME
.Nm stdc_trailing_zeros
.Nd find the number of trailing zeros in an integer
.Sh SYNOPSIS
.Lb libc
.In stdbit.h
.Ft unsigned int
.Fn stdc_trailing_zeros_uc "unsigned char value"
.Ft unsigned int
.Fn stdc_trailing_zeros_us "unsigned short value"
.Ft unsigned int
.Fn stdc_trailing_zeros_ui "unsigned int value"
.Ft unsigned int
.Fn stdc_trailing_zeros_ul "unsigned long value"
.Ft unsigned int
.Fn stdc_trailing_zeros_ull "unsigned long long value"
.Ft unsigned int
.Fn stdc_trailing_zeros "value"
.Sh DESCRIPTION
The
.Nm stdc_trailing_zeros_ Ns Em type Ns ()
family of functions returns the number of trailing zeros 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_trailing_zeros "value"
type-generic macro picks the appropriate
.Nm stdc_trailing_zeros_ Ns Em type Ns ()
function based on the type of
.Fa value .
.Sh RETURN VALUES
Returns the number of trailing zeros in
.Fa value .
If
.Fa value
is all zeros,
the total number of bits in the type of
.Fa value
is returned.
.Sh SEE ALSO
.Xr ffs 3 ,
.Xr stdbit 3 ,
.Xr stdc_leading_zeros 3 ,
.Xr stdc_trailing_ones 3 ,
.Xr stdc_first_trailing_one 3
.Sh STANDARDS
The
.Nm stdc_trailing_zeros_ Ns Em type Ns ()
family of functions and the
.Fn stdc_trailing_zeros
type-generic macro conform to
.St -isoC-2023 .
.Sh HISTORY
The
.Nm stdc_trailing_zeros_ Ns Em type Ns ()
family of functions and the
.Fn stdc_trailing_zeros
type-generic macro were added in
.Fx 15.1.
.Sh AUTHOR
.An Robert Clausecker Aq Mt fuz@FreeBSD.org