ROUNDUP(9) Kernel Developer's Manual ROUNDUP(9)
NAME
roundupmacros for counting and rounding
SYNOPSIS
#include <sys/param.h>
size
howmany(x, size);
size
roundup(x, size);
size
rounddown(x, size);
size
roundup2(x, size);
int
powerof2(x);
DESCRIPTION
The roundup() and rounddown() macros return an integer from rounding x up and down, respectively, to the next size. The howmany() macro in turn reveals how many times size fits into x, rounding the residual up.
 
The roundup2() macro also rounds up, but with the assumption that x is a power of two. If x is indeed a power of two, powerof2() return 1.
RETURN VALUES
The return value is an integer from the respective operation. If x is 0, all macros except powerof2() return 0. The behavior is undefined if size is 0.
SEE ALSO
CAVEATS
All described macros make no assumptions about the type of the parameters. These are implicitly assumed to be unsigned integers.