@@ -375,6 +375,57 @@ fail:
return ret;
}
+/*
+ * For a given L2 entry, count the number of contiguous subclusters of
+ * the same type starting from @sc_from. Compressed clusters are
+ * treated as if they were divided into subclusters of size
+ * s->subcluster_size.
+ *
+ * Return the number of contiguous subclusters and set @type to the
+ * subcluster type.
+ *
+ * If the L2 entry is invalid return -errno and set @type to
+ * QCOW2_SUBCLUSTER_INVALID.
+ */
+G_GNUC_UNUSED
+static int qcow2_get_subcluster_range_type(BlockDriverState *bs,
+ uint64_t l2_entry,
+ uint64_t l2_bitmap,
+ unsigned sc_from,
+ QCow2SubclusterType *type)
+{
+ BDRVQcow2State *s = bs->opaque;
+ uint32_t val;
+
+ *type = qcow2_get_subcluster_type(bs, l2_entry, l2_bitmap, sc_from);
+
+ if (*type == QCOW2_SUBCLUSTER_INVALID) {
+ return -EINVAL;
+ } else if (!has_subclusters(s) || *type == QCOW2_SUBCLUSTER_COMPRESSED) {
+ return s->subclusters_per_cluster - sc_from;
+ }
+
+ switch (*type) {
+ case QCOW2_SUBCLUSTER_NORMAL:
+ val = l2_bitmap | QCOW_OFLAG_SUB_ALLOC_RANGE(0, sc_from);
+ return cto32(val) - sc_from;
+
+ case QCOW2_SUBCLUSTER_ZERO_PLAIN:
+ case QCOW2_SUBCLUSTER_ZERO_ALLOC:
+ val = (l2_bitmap | QCOW_OFLAG_SUB_ZERO_RANGE(0, sc_from)) >> 32;
+ return cto32(val) - sc_from;
+
+ case QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN:
+ case QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC:
+ val = ((l2_bitmap >> 32) | l2_bitmap)
+ & ~QCOW_OFLAG_SUB_ALLOC_RANGE(0, sc_from);
+ return ctz32(val) - sc_from;
+
+ default:
+ g_assert_not_reached();
+ }
+}
+
/*
* Checks how many clusters in a given L2 slice are contiguous in the image
* file. As soon as one of the flags in the bitmask stop_flags changes compared
There are situations in which we want to know how many contiguous subclusters of the same type there are in a given cluster. This can be done by simply iterating over the subclusters and repeatedly calling qcow2_get_subcluster_type() for each one of them. However once we determined the type of a subcluster we can check the rest efficiently by counting the number of adjacent ones (or zeroes) in the bitmap. This is what this function does. Signed-off-by: Alberto Garcia <berto@igalia.com> --- block/qcow2-cluster.c | 51 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+)