[v5,10/31] qcow2: Add offset_to_sc_index()

Commit Message

Alberto Garcia May 5, 2020, 5:38 p.m. UTC

For a given offset, return the subcluster number within its cluster
(i.e. with 32 subclusters per cluster it returns a number between 0
and 31).

Signed-off-by: Alberto Garcia <[e-mail]>
Reviewed-by: Max Reitz <[e-mail]>
Reviewed-by: Vladimir Sementsov-Ogievskiy <[e-mail]>
---
 block/qcow2.h | 5 +++++
 1 file changed, 5 insertions(+)

Patch

diff --git a/block/qcow2.h b/block/qcow2.h
index 9d8ca8068c..e68febb15b 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -563,6 +563,11 @@  static inline int offset_to_l2_slice_index(BDRVQcow2State *s, int64_t offset)
     return (offset >> s->cluster_bits) & (s->l2_slice_size - 1);
 }
 
+static inline int offset_to_sc_index(BDRVQcow2State *s, int64_t offset)
+{
+    return (offset >> s->subcluster_bits) & (s->subclusters_per_cluster - 1);
+}
+
 static inline int64_t qcow2_vm_state_offset(BDRVQcow2State *s)
 {
     return (int64_t)s->l1_vm_state_index << (s->cluster_bits + s->l2_bits);