netbsd man page for rounddown

ROUNDUP(9)						   BSD Kernel Developer's Manual						ROUNDUP(9)

NAME
     roundup -- macros 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 size 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.

EXAMPLES
     The following example rounds the variable rx to a 32-bit boundary:

	   uint16_t rx;

	   ...

	   rx = roundup2(rx, sizeof(uint32_t));

SEE ALSO
     ilog2(3), param(3), imax(9)

CAVEATS
     All described macros make no assumptions about the type of the parameters.  These are implicitly assumed to be unsigned integers.

BSD
								   June 1, 2011 							       BSD