Re: [libvirt] [PATCH v3 1/6] internal: add macro to round value to the next closest power of 2

There are two special cases, if the input number is 0 or the number is larger then 2^31 (for 32bit unsigned int). For the special cases the return value is 0 because they cannot be rounded. Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1076098 Signed-off-by: Pavel Hrdina <phrdina(a)redhat.com&gt; --- bootstrap.conf | 1 + src/internal.h | 7 +++++++ tests/utiltest.c | 39 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 47 insertions(+) diff --git a/bootstrap.conf b/bootstrap.conf index d24a714..e7ea9c9 100644 --- a/bootstrap.conf +++ b/bootstrap.conf @@ -35,6 +35,7 @@ clock-time close connect configmake +count-leading-zeros count-one-bits crypto/md5 crypto/sha256 diff --git a/src/internal.h b/src/internal.h index f6a88b2..765b853 100644 --- a/src/internal.h +++ b/src/internal.h @@ -62,6 +62,7 @@ # include "c-strcase.h" # include "ignore-value.h" +# include "count-leading-zeros.h" /* On architectures which lack these limits, define them (ie. Cygwin). * Note that the libvirt code should be robust enough to handle the @@ -382,6 +383,12 @@ /* round up value to the closest multiple of size */ # define VIR_ROUND_UP(value, size) (VIR_DIV_UP(value, size) * (size)) +/* Round up to the next closest power of 2. It will return rounded number or 0 + * for 0 or number more than 2^31 (for 32bit unsigned int). */ +# define VIR_ROUND_UP_POWER_OF_TWO(value) \ + ((value) > 0 && (value) <= 1U<<(sizeof(unsigned int)*8 - 1) ? \ + 1U<<(sizeof(unsigned int)*8 - count_leading_zeros((value) - 1)) : 0)