mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-24 22:10:13 +00:00
c62b6265a6
My recent change broke make pdf and in other documentation formats results in weird rendering and invalid URL, all because of a forgotten comma to separate @uref arguments.
213 lines
11 KiB
Plaintext
213 lines
11 KiB
Plaintext
@node Bit Manipulation, Date and Time, Arithmetic, Top
|
|
@c %MENU% Bit manipulation
|
|
@chapter Bit Manipulation
|
|
|
|
This chapter contains information about functions and macros for
|
|
determining the endianness of integer types and manipulating the bits
|
|
of unsigned integers. These functions and macros are from ISO C23 and
|
|
are declared in the header file @file{stdbit.h}.
|
|
|
|
The following macros describe the endianness of integer types. They
|
|
have values that are integer constant expressions.
|
|
|
|
@defmac __STDC_ENDIAN_LITTLE__
|
|
This macro represents little-endian storage.
|
|
@end defmac
|
|
|
|
@defmac __STDC_ENDIAN_BIG__
|
|
This macro represents big-endian storage.
|
|
@end defmac
|
|
|
|
@defmac __STDC_ENDIAN_NATIVE__
|
|
This macro equals @code{__STDC_ENDIAN_LITTLE__} if integer types are
|
|
stored in memory in little-endian format, and equals
|
|
@code{__STDC_ENDIAN_BIG__} if integer types are stored in memory in
|
|
big-endian format.
|
|
@end defmac
|
|
|
|
The following functions manipulate the bits of unsigned integers.
|
|
Each function family has functions for the types @code{unsigned char},
|
|
@code{unsigned short}, @code{unsigned int}, @code{unsigned long int}
|
|
and @code{unsigned long long int}. In addition, there is a
|
|
corresponding type-generic macro (not listed below), named the same as
|
|
the functions but without any suffix such as @samp{_uc}. The
|
|
type-generic macro can only be used with an argument of an unsigned
|
|
integer type with a width of 8, 16, 32 or 64 bits, or when using
|
|
a compiler with support for
|
|
@uref{https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html,@code{__builtin_stdc_bit_ceil}},
|
|
etc.@:, built-in functions such as GCC 14.1 or later
|
|
any unsigned integer type those built-in functions support.
|
|
In GCC 14.1 that includes support for @code{unsigned __int128} and
|
|
@code{unsigned _BitInt(@var{n})} if supported by the target.
|
|
|
|
@deftypefun {unsigned int} stdc_leading_zeros_uc (unsigned char @var{x})
|
|
@deftypefunx {unsigned int} stdc_leading_zeros_us (unsigned short @var{x})
|
|
@deftypefunx {unsigned int} stdc_leading_zeros_ui (unsigned int @var{x})
|
|
@deftypefunx {unsigned int} stdc_leading_zeros_ul (unsigned long int @var{x})
|
|
@deftypefunx {unsigned int} stdc_leading_zeros_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_leading_zeros} functions count the number of leading
|
|
(most significant) zero bits in @var{x}, starting from the most
|
|
significant bit of the argument type. If @var{x} is zero, they return
|
|
the width of @var{x} in bits.
|
|
@end deftypefun
|
|
|
|
@deftypefun {unsigned int} stdc_leading_ones_uc (unsigned char @var{x})
|
|
@deftypefunx {unsigned int} stdc_leading_ones_us (unsigned short @var{x})
|
|
@deftypefunx {unsigned int} stdc_leading_ones_ui (unsigned int @var{x})
|
|
@deftypefunx {unsigned int} stdc_leading_ones_ul (unsigned long int @var{x})
|
|
@deftypefunx {unsigned int} stdc_leading_ones_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_leading_ones} functions count the number of leading
|
|
(most significant) one bits in @var{x}, starting from the most
|
|
significant bit of the argument type.
|
|
@end deftypefun
|
|
|
|
@deftypefun {unsigned int} stdc_trailing_zeros_uc (unsigned char @var{x})
|
|
@deftypefunx {unsigned int} stdc_trailing_zeros_us (unsigned short @var{x})
|
|
@deftypefunx {unsigned int} stdc_trailing_zeros_ui (unsigned int @var{x})
|
|
@deftypefunx {unsigned int} stdc_trailing_zeros_ul (unsigned long int @var{x})
|
|
@deftypefunx {unsigned int} stdc_trailing_zeros_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_trailing_zeros} functions count the number of trailing
|
|
(least significant) zero bits in @var{x}, starting from the least
|
|
significant bit of the argument type. If @var{x} is zero, they return
|
|
the width of @var{x} in bits.
|
|
@end deftypefun
|
|
|
|
@deftypefun {unsigned int} stdc_trailing_ones_uc (unsigned char @var{x})
|
|
@deftypefunx {unsigned int} stdc_trailing_ones_us (unsigned short @var{x})
|
|
@deftypefunx {unsigned int} stdc_trailing_ones_ui (unsigned int @var{x})
|
|
@deftypefunx {unsigned int} stdc_trailing_ones_ul (unsigned long int @var{x})
|
|
@deftypefunx {unsigned int} stdc_trailing_ones_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_trailing_ones} functions count the number of trailing
|
|
(least significant) one bits in @var{x}, starting from the least
|
|
significant bit of the argument type.
|
|
@end deftypefun
|
|
|
|
@deftypefun {unsigned int} stdc_first_leading_zero_uc (unsigned char @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_leading_zero_us (unsigned short @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_leading_zero_ui (unsigned int @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_leading_zero_ul (unsigned long int @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_leading_zero_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_first_leading_zero} functions return the position of
|
|
the most significant zero bit in @var{x}, counting from the most
|
|
significant bit of @var{x} as 1, or zero if there is no zero bit in
|
|
@var{x}.
|
|
@end deftypefun
|
|
|
|
@deftypefun {unsigned int} stdc_first_leading_one_uc (unsigned char @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_leading_one_us (unsigned short @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_leading_one_ui (unsigned int @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_leading_one_ul (unsigned long int @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_leading_one_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_first_leading_one} functions return the position of the
|
|
most significant one bit in @var{x}, counting from the most
|
|
significant bit of @var{x} as 1, or zero if there is no one bit in
|
|
@var{x}.
|
|
@end deftypefun
|
|
|
|
@deftypefun {unsigned int} stdc_first_trailing_zero_uc (unsigned char @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_trailing_zero_us (unsigned short @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_trailing_zero_ui (unsigned int @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_trailing_zero_ul (unsigned long int @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_trailing_zero_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_first_trailing_zero} functions return the position of
|
|
the least significant zero bit in @var{x}, counting from the least
|
|
significant bit of @var{x} as 1, or zero if there is no zero bit in
|
|
@var{x}.
|
|
@end deftypefun
|
|
|
|
@deftypefun {unsigned int} stdc_first_trailing_one_uc (unsigned char @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_trailing_one_us (unsigned short @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_trailing_one_ui (unsigned int @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_trailing_one_ul (unsigned long int @var{x})
|
|
@deftypefunx {unsigned int} stdc_first_trailing_one_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_first_trailing_one} functions return the position of
|
|
the least significant one bit in @var{x}, counting from the least
|
|
significant bit of @var{x} as 1, or zero if there is no one bit in
|
|
@var{x}.
|
|
@end deftypefun
|
|
|
|
@deftypefun {unsigned int} stdc_count_zeros_uc (unsigned char @var{x})
|
|
@deftypefunx {unsigned int} stdc_count_zeros_us (unsigned short @var{x})
|
|
@deftypefunx {unsigned int} stdc_count_zeros_ui (unsigned int @var{x})
|
|
@deftypefunx {unsigned int} stdc_count_zeros_ul (unsigned long int @var{x})
|
|
@deftypefunx {unsigned int} stdc_count_zeros_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_count_zeros} functions count the number of zero bits in
|
|
@var{x}.
|
|
@end deftypefun
|
|
|
|
@deftypefun {unsigned int} stdc_count_ones_uc (unsigned char @var{x})
|
|
@deftypefunx {unsigned int} stdc_count_ones_us (unsigned short @var{x})
|
|
@deftypefunx {unsigned int} stdc_count_ones_ui (unsigned int @var{x})
|
|
@deftypefunx {unsigned int} stdc_count_ones_ul (unsigned long int @var{x})
|
|
@deftypefunx {unsigned int} stdc_count_ones_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_count_ones} functions count the number of one bits in
|
|
@var{x}.
|
|
@end deftypefun
|
|
|
|
@deftypefun {_Bool} stdc_has_single_bit_uc (unsigned char @var{x})
|
|
@deftypefunx {_Bool} stdc_has_single_bit_us (unsigned short @var{x})
|
|
@deftypefunx {_Bool} stdc_has_single_bit_ui (unsigned int @var{x})
|
|
@deftypefunx {_Bool} stdc_has_single_bit_ul (unsigned long int @var{x})
|
|
@deftypefunx {_Bool} stdc_has_single_bit_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_has_single_bit} functions return whether @var{x} has
|
|
exactly one bit set to one.
|
|
@end deftypefun
|
|
|
|
@deftypefun {unsigned int} stdc_bit_width_uc (unsigned char @var{x})
|
|
@deftypefunx {unsigned int} stdc_bit_width_us (unsigned short @var{x})
|
|
@deftypefunx {unsigned int} stdc_bit_width_ui (unsigned int @var{x})
|
|
@deftypefunx {unsigned int} stdc_bit_width_ul (unsigned long int @var{x})
|
|
@deftypefunx {unsigned int} stdc_bit_width_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_bit_width} functions return the minimum number of bits
|
|
needed to store @var{x}, not counting leading zero bits. If @var{x}
|
|
is zero, they return zero.
|
|
@end deftypefun
|
|
|
|
@deftypefun {unsigned char} stdc_bit_floor_uc (unsigned char @var{x})
|
|
@deftypefunx {unsigned short} stdc_bit_floor_us (unsigned short @var{x})
|
|
@deftypefunx {unsigned int} stdc_bit_floor_ui (unsigned int @var{x})
|
|
@deftypefunx {unsigned long int} stdc_bit_floor_ul (unsigned long int @var{x})
|
|
@deftypefunx {unsigned long long int} stdc_bit_floor_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_bit_floor} functions return the largest integer power
|
|
of two that is less than or equal to @var{x}. If @var{x} is zero,
|
|
they return zero.
|
|
@end deftypefun
|
|
|
|
@deftypefun {unsigned char} stdc_bit_ceil_uc (unsigned char @var{x})
|
|
@deftypefunx {unsigned short} stdc_bit_ceil_us (unsigned short @var{x})
|
|
@deftypefunx {unsigned int} stdc_bit_ceil_ui (unsigned int @var{x})
|
|
@deftypefunx {unsigned long int} stdc_bit_ceil_ul (unsigned long int @var{x})
|
|
@deftypefunx {unsigned long long int} stdc_bit_ceil_ull (unsigned long long int @var{x})
|
|
@standards{C23, stdbit.h}
|
|
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
|
|
The @code{stdc_bit_ceil} functions return the smallest integer power
|
|
of two that is greater than or equal to @var{x}. If this cannot be
|
|
represented in the return type, they return zero.
|
|
@end deftypefun
|