Add NextSlotsIterator (#8652) (#8653)

automerge

ledger/src/lib.rs

@@ -12,6 +12,7 @@ pub mod genesis_utils;
 pub mod leader_schedule;
 pub mod leader_schedule_cache;
 pub mod leader_schedule_utils;
+pub mod next_slots_iterator;
 pub mod poh;
 pub mod rooted_slot_iterator;
 pub mod shred;

ledger/src/next_slots_iterator.rs

@@ -0,0 +1,117 @@
+use crate::{blockstore::*, blockstore_meta::SlotMeta};
+use solana_sdk::clock::Slot;
+
+pub struct NextSlotsIterator<'a> {
+    pending_slots: Vec<Slot>,
+    blockstore: &'a Blockstore,
+}
+
+impl<'a> NextSlotsIterator<'a> {
+    pub fn new(start_slot: Slot, blockstore: &'a Blockstore) -> Self {
+        Self {
+            pending_slots: vec![start_slot],
+            blockstore,
+        }
+    }
+}
+
+impl<'a> Iterator for NextSlotsIterator<'a> {
+    type Item = (Slot, SlotMeta);
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.pending_slots.is_empty() {
+            None
+        } else {
+            let slot = self.pending_slots.pop().unwrap();
+            if let Some(slot_meta) = self.blockstore.meta(slot).unwrap() {
+                self.pending_slots.extend(slot_meta.next_slots.iter());
+                Some((slot, slot_meta))
+            } else {
+                None
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::blockstore_processor::fill_blockstore_slot_with_ticks;
+    use solana_sdk::hash::Hash;
+    use std::collections::HashSet;
+
+    #[test]
+    fn test_next_slots_iterator() {
+        let blockstore_path = get_tmp_ledger_path!();
+        let blockstore = Blockstore::open(&blockstore_path).unwrap();
+        blockstore.set_roots(&[0]).unwrap();
+        let ticks_per_slot = 5;
+        /*
+            Build a blockstore in the ledger with the following fork structure:
+
+                 slot 0
+                   |
+                 slot 1  <-- set_root
+                 /   \
+            slot 2   |
+               /     |
+            slot 3   |
+                     |
+                   slot 4
+
+        */
+
+        // Fork 1, ending at slot 3
+        let last_entry_hash = Hash::default();
+        let fork_point = 1;
+        let mut fork_hash = Hash::default();
+        for slot in 0..=3 {
+            let parent = {
+                if slot == 0 {
+                    0
+                } else {
+                    slot - 1
+                }
+            };
+            let last_entry_hash = fill_blockstore_slot_with_ticks(
+                &blockstore,
+                ticks_per_slot,
+                slot,
+                parent,
+                last_entry_hash,
+            );
+
+            if slot == fork_point {
+                fork_hash = last_entry_hash;
+            }
+        }
+
+        // Fork 2, ending at slot 4
+        let _ =
+            fill_blockstore_slot_with_ticks(&blockstore, ticks_per_slot, 4, fork_point, fork_hash);
+
+        // Trying to get an iterator on any slot on the root fork should succeed
+        let result: HashSet<_> = NextSlotsIterator::new(0, &blockstore)
+            .into_iter()
+            .map(|(slot, _)| slot)
+            .collect();
+        let expected = vec![0, 1, 2, 3, 4].into_iter().collect();
+        assert_eq!(result, expected);
+
+        let result: HashSet<_> = NextSlotsIterator::new(2, &blockstore)
+            .into_iter()
+            .map(|(slot, _)| slot)
+            .collect();
+        let expected = vec![2, 3].into_iter().collect();
+        assert_eq!(result, expected);
+
+        let result: HashSet<_> = NextSlotsIterator::new(4, &blockstore)
+            .into_iter()
+            .map(|(slot, _)| slot)
+            .collect();
+        let expected = vec![4].into_iter().collect();
+        assert_eq!(result, expected);
+
+        drop(blockstore);
+        Blockstore::destroy(&blockstore_path).expect("Expected successful database destruction");
+    }
+}