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| -rw-r--r-- | man3/powerof2.3 | 46 |
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diff --git a/man3/powerof2.3 b/man3/powerof2.3 new file mode 100644 index 0000000..fae024f --- /dev/null +++ b/man3/powerof2.3 @@ -0,0 +1,46 @@ +.\" Copyright (C) 2022 Alejandro Colomar <alx@kernel.org> +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.TH powerof2 3 2023-03-30 "Linux man-pages 6.05.01" +.SH NAME +powerof2 \- test if a value is a power of 2 +.SH LIBRARY +Standard C library +.RI ( libc ) +.SH SYNOPSIS +.nf +.B #include <sys/param.h> +.PP +.BI "int powerof2(" x ); +.fi +.SH DESCRIPTION +This macro returns true if +.I x +is a power of 2, +and false otherwise. +.PP +.B 0 +is considered a power of 2. +This can make sense considering wrapping of unsigned integers, +and has interesting properties. +.SH RETURN VALUE +True or false, +if +.I x +is a power of 2 or not, +respectively. +.SH STANDARDS +BSD. +.SH CAVEATS +The arguments may be evaluated more than once. +.PP +Because this macro is implemented using bitwise operations, +some negative values can invoke undefined behavior. +For example, +the following invokes undefined behavior: +.IR "powerof2(INT_MIN);". +Call it only with unsigned types to be safe. +.SH SEE ALSO +.BR stdc_bit_ceil (3), +.BR stdc_bit_floor (3) |