[PATCH v7 04/11] qcow2: introduce qcow2_parse_compressed_cluster_descriptor()

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

This functionality will be reused later. Let's make a separate function
now.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/qcow2.h |  4 ++++
 block/qcow2.c | 21 ++++++++++++++++-----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/block/qcow2.h b/block/qcow2.h
index 0fe5f74ed3..4859ca3d0d 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -914,6 +914,10 @@ int qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
                                           uint64_t offset,
                                           int compressed_size,
                                           uint64_t *host_offset);
+void qcow2_parse_compressed_cluster_descriptor(BDRVQcow2State *s,
+                                               uint64_t cluster_descriptor,
+                                               uint64_t *coffset,
+                                               int *csize);
 
 int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m);
 void qcow2_alloc_cluster_abort(BlockDriverState *bs, QCowL2Meta *m);
diff --git a/block/qcow2.c b/block/qcow2.c
index 9f1b6461c8..2095188b6f 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -4691,6 +4691,19 @@ qcow2_co_pwritev_compressed_part(BlockDriverState *bs,
     return ret;
 }
 
+void qcow2_parse_compressed_cluster_descriptor(BDRVQcow2State *s,
+                                               uint64_t cluster_descriptor,
+                                               uint64_t *coffset,
+                                               int *csize)
+{
+    int nb_csectors;
+
+    *coffset = cluster_descriptor & s->cluster_offset_mask;
+    nb_csectors = ((cluster_descriptor >> s->csize_shift) & s->csize_mask) + 1;
+    *csize = nb_csectors * QCOW2_COMPRESSED_SECTOR_SIZE -
+        (*coffset & ~QCOW2_COMPRESSED_SECTOR_MASK);
+}
+
 static int coroutine_fn
 qcow2_co_preadv_compressed(BlockDriverState *bs,
                            uint64_t cluster_descriptor,
@@ -4700,15 +4713,13 @@ qcow2_co_preadv_compressed(BlockDriverState *bs,
                            size_t qiov_offset)
 {
     BDRVQcow2State *s = bs->opaque;
-    int ret = 0, csize, nb_csectors;
+    int ret = 0, csize;
     uint64_t coffset;
     uint8_t *buf, *out_buf;
     int offset_in_cluster = offset_into_cluster(s, offset);
 
-    coffset = cluster_descriptor & s->cluster_offset_mask;
-    nb_csectors = ((cluster_descriptor >> s->csize_shift) & s->csize_mask) + 1;
-    csize = nb_csectors * QCOW2_COMPRESSED_SECTOR_SIZE -
-        (coffset & ~QCOW2_COMPRESSED_SECTOR_MASK);
+    qcow2_parse_compressed_cluster_descriptor(s, cluster_descriptor, &coffset,
+                                              &csize);
 
     buf = g_try_malloc(csize);
     if (!buf) {
-- 
2.29.2