range: Introduce range_get_last_bit()
This helper get the highest 1 bit position of the upper bound.
If the range is empty or upper bound is zero, -1 is returned.
Suggested-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/include/qemu/range.h b/include/qemu/range.h
index 205e1da..4ce694a 100644
--- a/include/qemu/range.h
+++ b/include/qemu/range.h
@@ -20,6 +20,8 @@
#ifndef QEMU_RANGE_H
#define QEMU_RANGE_H
+#include "qemu/bitops.h"
+
/*
* Operations on 64 bit address ranges.
* Notes:
@@ -217,6 +219,15 @@
return !(last2 < first1 || last1 < first2);
}
+/* Get highest non-zero bit position of a range */
+static inline int range_get_last_bit(Range *range)
+{
+ if (range_is_empty(range)) {
+ return -1;
+ }
+ return 63 - clz64(range->upb);
+}
+
/*
* Return -1 if @a < @b, 1 @a > @b, and 0 if they touch or overlap.
* Both @a and @b must not be empty.
