Implement basic BeaconChain persistence.

beacon_node/beacon_chain/src/persisted_beacon_chain.rs

@@ -0,0 +1,30 @@
+use crate::{BeaconChainTypes, CheckPoint};
+use ssz::{Decode, Encode};
+use ssz_derive::{Decode, Encode};
+use store::{DBColumn, Error as StoreError, StoreItem};
+use types::BeaconState;
+
+/// 32-byte key for accessing the `PersistedBeaconChain`.
+pub const BEACON_CHAIN_DB_KEY: &str = "PERSISTEDBEACONCHAINPERSISTEDBEA";
+
+#[derive(Encode, Decode)]
+pub struct PersistedBeaconChain<T: BeaconChainTypes> {
+    pub canonical_head: CheckPoint<T::EthSpec>,
+    pub finalized_head: CheckPoint<T::EthSpec>,
+    // TODO: operations pool.
+    pub state: BeaconState<T::EthSpec>,
+}
+
+impl<T: BeaconChainTypes> StoreItem for PersistedBeaconChain<T> {
+    fn db_column() -> DBColumn {
+        DBColumn::BeaconChain
+    }
+
+    fn as_store_bytes(&self) -> Vec<u8> {
+        self.as_ssz_bytes()
+    }
+
+    fn from_store_bytes(bytes: &mut [u8]) -> Result<Self, StoreError> {
+        Self::from_ssz_bytes(bytes).map_err(Into::into)
+    }
+}