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 205e1da76dc5b29327f590b8293a826ced63c25d..4ce694a398311a32e9b5e3ca97aed97c90c0ae09 100644 (file)
--- 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 @@ static inline int ranges_overlap(uint64_t first1, uint64_t len1,
     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.