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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 (cherry picked from commit d790b16bbf0c3055ef00200d01659dfb3c0e5e5e)
104 lines
2 KiB
Groff
104 lines
2 KiB
Groff
.\"
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.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
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.\"
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.\" SPDX-License-Identifier: BSD-2-Clause
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.\"
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.Dd November 9, 2025
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.Dt STDC_BIT_WIDTH 3
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.Os
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.Sh NAME
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.Nm stdc_bit_width
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.Nd find the first trailing one in an intege
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.Sh SYNOPSIS
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.Lb libc
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.In stdbit.h
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.Ft unsigned int
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.Fn stdc_bit_width_uc "unsigned char value"
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.Ft unsigned int
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.Fn stdc_bit_width_us "unsigned short value"
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.Ft unsigned int
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.Fn stdc_bit_width_ui "unsigned int value"
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.Ft unsigned int
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.Fn stdc_bit_width_ul "unsigned long value"
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.Ft unsigned int
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.Fn stdc_bit_width_ull "unsigned long long value"
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.Ft unsigned int
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.Fn stdc_bit_width "value"
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.Sh DESCRIPTION
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The
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.Nm stdc_bit_width_ Ns Em type Ns ()
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family of functions returns the number of bits needed to represent
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.Fa value ,
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where
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.Fa value
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is of type
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.Va unsigned char ,
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.Va unsigned short ,
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.Va unsigned int ,
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.Va unsigned long ,
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or
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.Va unsigned long long
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for
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.Em type
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being
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.Sy uc ,
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.Sy us ,
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.Sy ui ,
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.Sy ul ,
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or
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.Sy ull
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respectively.
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The
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.Fn stdc_bit_width "value"
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type-generic macro picks the appropriate
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.Nm stdc_bit_width_ Ns Em type Ns ()
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function based on the type of
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.Fa value .
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.Pp
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Functions
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.Fn stdc_bit_width_ui ,
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.Fn stdc_bit_width_ul ,
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and
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.Fn stdc_bit_width_ull
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are identical to
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.Bx 4.3
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functions
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.Xr fls 3 ,
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.Xr flsl 3 ,
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and
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.Xr flsll 3
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respectively, except for operating on unsigned instead of signed values.
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.Sh RETURN VALUES
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Returns the least number of bits needed to represent
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.Fa value .
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If
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.Fa value
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is zero, the return value is zero.
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Otherwise it is
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.EQ
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1 + \(lf log sub 2 italic value \(rf .
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.EN
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.Sh SEE ALSO
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.Xr bit_fls 3 ,
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.Xr fls 3 ,
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.Xr flsl 3 ,
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.Xr flsll 3 ,
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.Xr stdbit 3 ,
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.Xr stdc_count_leading_zeros 3 ,
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.Xr stdc_first_leading_one 3
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.Sh STANDARDS
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The
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.Nm stdc_bit_width_ Ns Em type Ns ()
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family of functions and the
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.Fn stdc_bit_width
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type-generic macro conform to
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.St -isoC-2023 .
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.Sh HISTORY
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The
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.Nm stdc_bit_width_ Ns Em type Ns ()
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family of functions and the
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.Fn stdc_bit_width
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type-generic macro were added in
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.Fx 15.1.
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.Sh AUTHOR
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.An Robert Clausecker Aq Mt fuz@FreeBSD.org
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