.\" $NetBSD: setbit.9,v 1.3 2012/12/04 18:03:37 christos Exp $
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Jukka Ruohonen.
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.Dd December 4, 2012
.Dt SETBIT 9
.Os
.Sh NAME
.Nm setbit
.Nd macros related to bitmaps
.Sh SYNOPSIS
.In sys/param.h
.Ft void
.Fn setbit "array" "x"
.Ft void
.Fn clrbit "array" "x"
.Ft int
.Fn isset "array" "x"
.Ft int
.Fn isclr "array" "x"
.Sh DESCRIPTION
The
.Nm
family of macros operate with bitmaps, also known as bit arrays.
.Pp
In a nutshell,
.Fn setbit
sets the bit
.Fa x
in
.Fa array ,
.Fn clrbit
clears it,
.Fn isset
tests whether
.Fa x
is set, and
.Fn isclr
returns 1 if
.Fa x
is not set.
.Sh EXAMPLES
The following example declares a buffer of 10 chars,
treating it as an array of 80 bits:
.Bd -literal -offset indent
char buf[10];

\&...

setbit(buf, 12);	/* set the fifth bit in the second byte */
.Ed
.Sh SEE ALSO
.Xr bitmap 3 ,
.Xr bitstring 3
.Sh CAVEATS
The number of valid bits in a given array is assumed to be multiple of
.Dv CHAR_BIT ,
the number of bits for smallest object that is not a bit-field.