Implement tree states & hierarchical state DB

beacon_node/store/src/hot_state_iter.rs

@@ -0,0 +1,50 @@
+use crate::{hot_cold_store::HotColdDBError, Error, HotColdDB, HotStateSummary, ItemStore};
+use types::{EthSpec, Hash256, Slot};
+
+pub struct HotStateRootIter<'a, E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> {
+    store: &'a HotColdDB<E, Hot, Cold>,
+    next_slot: Slot,
+    next_state_root: Hash256,
+}
+
+impl<'a, E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> HotStateRootIter<'a, E, Hot, Cold> {
+    pub fn new(
+        store: &'a HotColdDB<E, Hot, Cold>,
+        next_slot: Slot,
+        next_state_root: Hash256,
+    ) -> Self {
+        Self {
+            store,
+            next_slot,
+            next_state_root,
+        }
+    }
+
+    fn do_next(&mut self) -> Result<Option<(Hash256, HotStateSummary)>, Error> {
+        if self.next_state_root.is_zero() {
+            return Ok(None);
+        }
+
+        let summary = self
+            .store
+            .load_hot_state_summary(&self.next_state_root)?
+            .ok_or(HotColdDBError::MissingHotStateSummary(self.next_state_root))?;
+
+        let state_root = self.next_state_root;
+
+        self.next_state_root = summary.prev_state_root;
+        self.next_slot -= 1;
+
+        Ok(Some((state_root, summary)))
+    }
+}
+
+impl<'a, E: EthSpec, Hot: ItemStore<E>, Cold: ItemStore<E>> Iterator
+    for HotStateRootIter<'a, E, Hot, Cold>
+{
+    type Item = Result<(Hash256, HotStateSummary), Error>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.do_next().transpose()
+    }
+}