common: Add round functions

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/common.h b/include/common.h
index 2f24645..7270769 100644
--- a/include/common.h
+++ b/include/common.h
@@ -65,6 +65,16 @@ extern "C" {
 	(_x > _y) ? _x : _y; \
 })
 
+/*
+ * This looks more complex than it should be. But we need to
+ * get the type for the ~ right in round_down (it needs to be
+ * as wide as the result!), and we want to evaluate the macro
+ * arguments just once each.
+ */
+#define __round_mask(x, y) ((__typeof__(x))((y)-1))
+#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)
+#define round_down(x, y) ((x) & ~__round_mask(x, y))
+
 #ifndef O_CLOEXEC
 #define O_CLOEXEC 0
 #endif