Implement CachedTreeHash for TreeHashVector

eth2/types/src/tree_hash_vector.rs

@@ -1,4 +1,5 @@
 use crate::test_utils::{RngCore, TestRandom};
+use cached_tree_hash::CachedTreeHash;
 use serde_derive::{Deserialize, Serialize};
 use ssz::{Decodable, DecodeError, Encodable, SszStream};
 use std::ops::{Deref, DerefMut};
@@ -54,6 +55,43 @@ where
     }
 }
 
+impl<T> CachedTreeHash<TreeHashVector<T>> for TreeHashVector<T>
+where
+    T: CachedTreeHash<T> + TreeHash,
+{
+    fn new_tree_hash_cache(
+        &self,
+        depth: usize,
+    ) -> Result<cached_tree_hash::TreeHashCache, cached_tree_hash::Error> {
+        let (cache, _overlay) = cached_tree_hash::impls::vec::new_tree_hash_cache(self, depth)?;
+
+        Ok(cache)
+    }
+
+    fn num_tree_hash_cache_chunks(&self) -> usize {
+        cached_tree_hash::BTreeOverlay::new(self, 0, 0)
+            .and_then(|o| Ok(o.num_chunks()))
+            .unwrap_or_else(|_| 1)
+    }
+
+    fn tree_hash_cache_overlay(
+        &self,
+        chunk_offset: usize,
+        depth: usize,
+    ) -> Result<cached_tree_hash::BTreeOverlay, cached_tree_hash::Error> {
+        cached_tree_hash::impls::vec::produce_overlay(self, chunk_offset, depth)
+    }
+
+    fn update_tree_hash_cache(
+        &self,
+        cache: &mut cached_tree_hash::TreeHashCache,
+    ) -> Result<(), cached_tree_hash::Error> {
+        cached_tree_hash::impls::vec::update_tree_hash_cache(self, cache)?;
+
+        Ok(())
+    }
+}
+
 impl<T> Encodable for TreeHashVector<T>
 where
     T: Encodable,