Add utility functions for testing (#10749) (#10752)

* Add ancestor iterator

* Add blockstore generation from trees

Co-authored-by: Carl <carl@solana.com>
(cherry picked from commit 77b8de193c)

Co-authored-by: carllin <wumu727@gmail.com>

ledger/src/ancestor_iterator.rs

@@ -0,0 +1,116 @@
+use crate::blockstore::*;
+use solana_sdk::clock::Slot;
+
+pub struct AncestorIterator<'a> {
+    current: Option<Slot>,
+    blockstore: &'a Blockstore,
+}
+
+impl<'a> AncestorIterator<'a> {
+    pub fn new(start_slot: Slot, blockstore: &'a Blockstore) -> Self {
+        let current = blockstore.meta(start_slot).unwrap().and_then(|slot_meta| {
+            if slot_meta.is_parent_set() && start_slot != 0 {
+                Some(slot_meta.parent_slot)
+            } else {
+                None
+            }
+        });
+        Self {
+            current,
+            blockstore,
+        }
+    }
+}
+impl<'a> Iterator for AncestorIterator<'a> {
+    type Item = Slot;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let current = self.current.clone();
+        current.map(|slot| {
+            if slot != 0 {
+                self.current = self.blockstore.meta(slot).unwrap().and_then(|slot_meta| {
+                    if slot_meta.is_parent_set() {
+                        Some(slot_meta.parent_slot)
+                    } else {
+                        None
+                    }
+                });
+            } else {
+                self.current = None;
+            }
+            slot
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::blockstore_processor::fill_blockstore_slot_with_ticks;
+    use solana_sdk::hash::Hash;
+
+    #[test]
+    fn test_ancestor_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
+                 /   \
+            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);
+
+        // Test correctness
+        assert!(AncestorIterator::new(0, &blockstore)
+            .collect::<Vec<Slot>>()
+            .is_empty());
+        assert_eq!(
+            AncestorIterator::new(4, &blockstore).collect::<Vec<Slot>>(),
+            vec![1, 0]
+        );
+        assert_eq!(
+            AncestorIterator::new(3, &blockstore).collect::<Vec<Slot>>(),
+            vec![2, 1, 0]
+        );
+    }
+}