blockstore: Make is_orphan() a method of SlotMeta (solana-labs#34889)

The old function's only input is a SlotMeta, so makes sense to move
it a member function of SlotMeta

ledger/src/blockstore.rs

@@ -1803,7 +1803,7 @@ impl Blockstore {
         };
 
         // Parent for slot meta should have been set by this point
-        assert!(!is_orphan(slot_meta));
+        assert!(!slot_meta.is_orphan());
 
         let new_consumed = if slot_meta.consumed == index {
             let mut current_index = index + 1;
@@ -3822,7 +3822,8 @@ impl Blockstore {
         let meta_backup = &slot_meta_entry.old_slot_meta;
         {
             let mut meta_mut = meta.borrow_mut();
-            let was_orphan_slot = meta_backup.is_some() && is_orphan(meta_backup.as_ref().unwrap());
+            let was_orphan_slot =
+                meta_backup.is_some() && meta_backup.as_ref().unwrap().is_orphan();
 
             // If:
             // 1) This is a new slot
@@ -3848,7 +3849,7 @@ impl Blockstore {
 
                     // If the parent of `slot` is a newly inserted orphan, insert it into the orphans
                     // column family
-                    if is_orphan(&RefCell::borrow(&*prev_slot_meta)) {
+                    if RefCell::borrow(&*prev_slot_meta).is_orphan() {
                         write_batch.put::<cf::Orphans>(prev_slot, &true)?;
                     }
                 }
@@ -3956,7 +3957,7 @@ impl Blockstore {
                 // during the chaining process, see the function find_slot_meta_in_cached_state()
                 // for details. Slots that are orphans are missing a parent_slot, so we should
                 // fill in the parent now that we know it.
-                if is_orphan(&meta) {
+                if meta.is_orphan() {
                     meta.parent_slot = Some(parent_slot);
                 }
 
@@ -4216,12 +4217,6 @@ fn find_slot_meta_in_cached_state<'a>(
     }
 }
 
-fn is_orphan(meta: &SlotMeta) -> bool {
-    // If we have no parent, then this is the head of a detached chain of
-    // slots
-    meta.parent_slot.is_none()
-}
-
 // 1) Chain current_slot to the previous slot defined by prev_slot_meta
 fn chain_new_slot_to_prev_slot(
     prev_slot_meta: &mut SlotMeta,
@@ -6324,7 +6319,7 @@ pub mod tests {
             .meta(1)
             .expect("Expect database get to succeed")
             .unwrap();
-        assert!(is_orphan(&meta));
+        assert!(meta.is_orphan());
         assert_eq!(
             blockstore.orphans_iterator(0).unwrap().collect::<Vec<_>>(),
             vec![1]
@@ -6340,12 +6335,12 @@ pub mod tests {
             .meta(1)
             .expect("Expect database get to succeed")
             .unwrap();
-        assert!(!is_orphan(&meta));
+        assert!(!meta.is_orphan());
         let meta = blockstore
             .meta(0)
             .expect("Expect database get to succeed")
             .unwrap();
-        assert!(is_orphan(&meta));
+        assert!(meta.is_orphan());
         assert_eq!(
             blockstore.orphans_iterator(0).unwrap().collect::<Vec<_>>(),
             vec![0]
@@ -6369,7 +6364,7 @@ pub mod tests {
                 .meta(i)
                 .expect("Expect database get to succeed")
                 .unwrap();
-            assert!(!is_orphan(&meta));
+            assert!(!meta.is_orphan());
         }
         // Orphans cf is empty
         assert!(blockstore.orphans_cf.is_empty().unwrap());

ledger/src/blockstore_meta.rs

@@ -263,6 +263,13 @@ impl SlotMeta {
         Some(self.consumed) == self.last_index.map(|ix| ix + 1)
     }
 
+    /// Returns a boolean indicating whether this meta's parent slot is known.
+    /// This value being true indicates that this meta's slot is the head of a
+    /// detached chain of slots.
+    pub(crate) fn is_orphan(&self) -> bool {
+        self.parent_slot.is_none()
+    }
+
     /// Returns a boolean indicating whether the meta is connected.
     pub fn is_connected(&self) -> bool {
         self.connected_flags.contains(ConnectedFlags::CONNECTED)