qcow2: Add offset_to_sc_index()
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 <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <56e3e4ac0d827c6a2f5f259106c5ddb7c4ca2653.1594396418.git.berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
diff --git a/block/qcow2.h b/block/qcow2.h
index eee4c8d..2503374 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -581,6 +581,11 @@
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);
