ilog2(3) [netbsd man page]

ILOG2(3)						   BSD Library Functions Manual 						  ILOG2(3)

NAME

     ilog2 -- integer logarithm

SYNOPSIS

     #include <sys/bitops.h>

     size
     ilog2(size x);

DESCRIPTION

     The ilog2() macro returns an integer (binary) logarithm of x.  It is the logarithm for base 2; the binary logarithm of x is the power to
     which the number 2 must be raised to obtain the value x.

     The type of the input parameter should be either uint32_t or uint64_t.

ERRORS

     A value -1 is returned on error.

SEE ALSO

     bitops(3), ilogb(3), log2(3), imax(9), powerof2(9)

HISTORY

     The ilog2() macro first appeared in NetBSD 5.0.

BSD
								   May 10, 2011 							       BSD

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