.\" $NetBSD: roundup.9,v 1.8 2011/06/01 11:19:19 jruoho Exp $
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.\" by Jukka Ruohonen.
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.Dd June 1, 2011
.Dt ROUNDUP 9
.Os
.Sh NAME
.Nm roundup
.Nd macros for counting and rounding
.Sh SYNOPSIS
.In sys/param.h
.Ft size
.Fn howmany "x" "size"
.Ft size
.Fn roundup "x" "size"
.Ft size
.Fn rounddown "x" "size"
.Ft size
.Fn roundup2 "x" "size"
.Ft int
.Fn powerof2 "x"
.Sh DESCRIPTION
The
.Fn roundup
and
.Fn rounddown
macros return an integer from rounding
.Fa x
up and down, respectively, to the next
.Fa size .
The
.Fn howmany
macro in turn reveals how many times
.Fa size
fits into
.Fa x ,
rounding the residual up.
.Pp
The
.Fn roundup2
macro also rounds up, but with the assumption that
.Fa size
is a power of two.
If
.Fa x
is indeed a power of two,
.Fn powerof2
return 1.
.Sh RETURN VALUES
The return value is an integer from the respective operation.
If
.Fa x
is 0, all macros except
.Fn powerof2
return 0.
The behavior is undefined if
.Fa size
is 0.
.Sh EXAMPLES
The following example rounds the variable
.Va rx
to a 32-bit boundary:
.Bd -literal -offset indent
uint16_t rx;

\&...

rx = roundup2(rx, sizeof(uint32_t));
.Ed
.Sh SEE ALSO
.Xr ilog2 3 ,
.Xr param 3 ,
.Xr imax 9
.Sh CAVEATS
All described macros make no assumptions about the type of the parameters.
These are implicitly assumed to be unsigned integers.