[Qemu-devel] [PATCH v13 05/12] qcow2: Name typedef for cluster type

[Eric Blake]

Although it doesn't add all that much type safety (this is C, after
all), it does add a bit of legibility to use the name QCow2ClusterType
instead of a plain int.

In particular, qcow2_get_cluster_offset() has an overloaded return
type; a QCow2ClusterType on success, and -errno on failure; keeping
the cluster type in a separate variable makes it slightly easier for
the next patch to make further computations based on the type.

Suggested-by: Max Reitz <address@hidden>
Signed-off-by: Eric Blake <address@hidden>

---
v13: new patch
---
 block/qcow2.h          |  6 +++---
 block/qcow2-cluster.c  | 17 +++++++++--------
 block/qcow2-refcount.c |  2 +-
 3 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/block/qcow2.h b/block/qcow2.h
index 8731f24..c148bbc 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -349,12 +349,12 @@ typedef struct QCowL2Meta
     QLIST_ENTRY(QCowL2Meta) next_in_flight;
 } QCowL2Meta;

-enum {
+typedef enum QCow2ClusterType {
     QCOW2_CLUSTER_UNALLOCATED,
     QCOW2_CLUSTER_NORMAL,
     QCOW2_CLUSTER_COMPRESSED,
     QCOW2_CLUSTER_ZERO
-};
+} QCow2ClusterType;

 typedef enum QCow2MetadataOverlap {
     QCOW2_OL_MAIN_HEADER_BITNR    = 0,
@@ -443,7 +443,7 @@ static inline uint64_t 
qcow2_max_refcount_clusters(BDRVQcow2State *s)
     return QCOW_MAX_REFTABLE_SIZE >> s->cluster_bits;
 }

-static inline int qcow2_get_cluster_type(uint64_t l2_entry)
+static inline QCow2ClusterType qcow2_get_cluster_type(uint64_t l2_entry)
 {
     if (l2_entry & QCOW_OFLAG_COMPRESSED) {
         return QCOW2_CLUSTER_COMPRESSED;
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index f3bfce6..ed78a30 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -340,7 +340,7 @@ static int count_contiguous_clusters(int nb_clusters, int 
cluster_size,
  */
 static int count_contiguous_clusters_unallocated(int nb_clusters,
                                                  uint64_t *l2_table,
-                                                 int wanted_type)
+                                                 QCow2ClusterType wanted_type)
 {
     int i;

@@ -500,6 +500,7 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t 
offset,
     int l1_bits, c;
     unsigned int offset_in_cluster;
     uint64_t bytes_available, bytes_needed, nb_clusters;
+    QCow2ClusterType type;
     int ret;

     offset_in_cluster = offset_into_cluster(s, offset);
@@ -522,13 +523,13 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, 
uint64_t offset,

     l1_index = offset >> l1_bits;
     if (l1_index >= s->l1_size) {
-        ret = QCOW2_CLUSTER_UNALLOCATED;
+        type = QCOW2_CLUSTER_UNALLOCATED;
         goto out;
     }

     l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
     if (!l2_offset) {
-        ret = QCOW2_CLUSTER_UNALLOCATED;
+        type = QCOW2_CLUSTER_UNALLOCATED;
         goto out;
     }

@@ -557,8 +558,8 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t 
offset,
      * true */
     assert(nb_clusters <= INT_MAX);

-    ret = qcow2_get_cluster_type(*cluster_offset);
-    switch (ret) {
+    type = qcow2_get_cluster_type(*cluster_offset);
+    switch (type) {
     case QCOW2_CLUSTER_COMPRESSED:
         /* Compressed clusters can only be processed one by one */
         c = 1;
@@ -633,7 +634,7 @@ out:
     assert(bytes_available - offset_in_cluster <= UINT_MAX);
     *bytes = bytes_available - offset_in_cluster;

-    return ret;
+    return type;

 fail:
     qcow2_cache_put(bs, s->l2_table_cache, (void **)&l2_table);
@@ -891,7 +892,7 @@ static int count_cow_clusters(BDRVQcow2State *s, int 
nb_clusters,

     for (i = 0; i < nb_clusters; i++) {
         uint64_t l2_entry = be64_to_cpu(l2_table[l2_index + i]);
-        int cluster_type = qcow2_get_cluster_type(l2_entry);
+        QCow2ClusterType cluster_type = qcow2_get_cluster_type(l2_entry);

         switch(cluster_type) {
         case QCOW2_CLUSTER_NORMAL:
@@ -1757,7 +1758,7 @@ static int expand_zero_clusters_in_l1(BlockDriverState 
*bs, uint64_t *l1_table,
         for (j = 0; j < s->l2_size; j++) {
             uint64_t l2_entry = be64_to_cpu(l2_table[j]);
             int64_t offset = l2_entry & L2E_OFFSET_MASK;
-            int cluster_type = qcow2_get_cluster_type(l2_entry);
+            QCow2ClusterType cluster_type = qcow2_get_cluster_type(l2_entry);
             bool preallocated = offset != 0;

             if (cluster_type != QCOW2_CLUSTER_ZERO) {
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 908dbe5..e639b34 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1640,7 +1640,7 @@ static int check_oflag_copied(BlockDriverState *bs, 
BdrvCheckResult *res,
         for (j = 0; j < s->l2_size; j++) {
             uint64_t l2_entry = be64_to_cpu(l2_table[j]);
             uint64_t data_offset = l2_entry & L2E_OFFSET_MASK;
-            int cluster_type = qcow2_get_cluster_type(l2_entry);
+            QCow2ClusterType cluster_type = qcow2_get_cluster_type(l2_entry);

             if ((cluster_type == QCOW2_CLUSTER_NORMAL) ||
                 ((cluster_type == QCOW2_CLUSTER_ZERO) && (data_offset != 0))) {
-- 
2.9.3