Robert Clausecker
8efcc64928
Approved by: markj (mentor) MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D55249
121 lines
2.7 KiB
Plaintext
121 lines
2.7 KiB
Plaintext
.\"
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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 STDBIT 3
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.Os
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.Sh NAME
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.Nm stdbit
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.Nd bit and byte utilities
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.Sh SYNOPSIS
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.Lb libc
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.In stdbit.h
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.Fd #define __STDC_ENDIAN_LITTLE__
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.Fd #define __STDC_ENDIAN_BIG__
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.Fd #define __STDC_ENDIAN_NATIVE__
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.Ft unsigned int
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.Fn stdc_count_leading_zeros "value"
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.Ft unsigned int
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.Fn stdc_count_leading_ones "value"
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.Ft unsigned int
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.Fn stdc_count_trailing_zeros "value"
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.Ft unsigned int
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.Fn stdc_count_trailing_ones "value"
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.Ft unsigned int
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.Fn stdc_first_leading_zero "value"
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.Ft unsigned int
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.Fn stdc_first_leading_one "value"
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.Ft unsigned int
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.Fn stdc_first_trailing_zero "value"
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.Ft unsigned int
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.Fn stdc_first_trailing_one "value"
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.Ft unsigned int
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.Fn stdc_count_zeros "value"
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.Ft unsigned int
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.Fn stdc_count_ones "value"
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.Ft bool
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.Fn stdc_has_single_bit "value"
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.Ft unsigned int
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.Fn stdc_bit_width "value"
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.Ft typeof Ns Pq Em value
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.Fn stdc_bit_floor "value"
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.Ft typeof Ns Pq Em value
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.Fn stdc_bit_ceil "value"
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.Sh DESCRIPTION
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The
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.Dv __STDC_ENDIAN_NATIVE__
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macro describes the byte order or endianness of the machine for which the
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program is built.
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If the machine has big-endian byte order, this macro is equal to
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.Dv __STDC_ENDIAN_BIG__ .
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If the machine has little-endian byte order, this macro is equal to
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.Dv __STDC_ENDIAN_LITTLE__ .
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Otherwise, the macro has a value that is equal to neither.
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.Pp
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The bit and byte utility functions analyze the bits within a datum.
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Each function
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.Em func
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is provided in five variants
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.Nm stdc_ Ns Em func Ns Em _ Ns Em type Ns Pq Em 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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Additionally, for each
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.Em func ,
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a type-generic macro
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.Nm stdc_ Ns Em func Ns Pq Em value
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that picks the appropriate function
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.Nm stdc_ Ns Em func Ns Em _ Ns Em type Ns Pq Em value
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based on the type of
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.Fa value
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is provided.
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.Sh SEE ALSO
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.Xr arch 7 ,
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.Xr bitstring 3 ,
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.Xr ffs 3 ,
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.Xr fls 3 ,
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.Xr stdc_count_leading_zeros 3 ,
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.Xr stdc_count_leading_ones 3 ,
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.Xr stdc_count_trailing_zeros 3 ,
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.Xr stdc_count_trailing_ones 3 ,
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.Xr stdc_first_leading_zero 3 ,
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.Xr stdc_first_leading_one 3 ,
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.Xr stdc_first_trailing_zero 3 ,
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.Xr stdc_first_trailing_one 3 ,
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.Xr stdc_count_zeros 3 ,
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.Xr stdc_count_ones 3 ,
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.Xr stdc_has_single_bit 3 ,
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.Xr stdc_bit_width 3 ,
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.Xr stdc_bit_floor 3 ,
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.Xr stdc_bit_ceil 3
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.Sh STANDARDS
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The macros and functions of the
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.In stdbit.h
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header conform to
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.St -isoC-2023 .
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.Sh HISTORY
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The
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.In stdbit.h
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header and the macros and functions defined therein where 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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