powerof2(9) - NetBSD Manual Pages

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ROUNDUP(9)             NetBSD 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);

     size
     rounddown2(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() and rounddown2() macros also round up and down, respec-
     tively, 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 parame-
     ters.  These are implicitly assumed to be unsigned integers.

NetBSD 10.1                     October 2, 2019                    NetBSD 10.1