Implement new BeaconStateTypes trait in types

eth2/utils/fixed_len_vec/src/impls.rs

@@ -0,0 +1,70 @@
+use super::*;
+// use cached_tree_hash::CachedTreeHash;
+// use ssz::{Decodable, Encodable};
+// use tree_hash::TreeHash;
+
+impl<T, N: Unsigned> tree_hash::TreeHash for FixedLenVec<T, N>
+where
+    T: tree_hash::TreeHash,
+{
+    fn tree_hash_type() -> tree_hash::TreeHashType {
+        tree_hash::TreeHashType::Vector
+    }
+
+    fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+        unreachable!("Vector should never be packed.")
+    }
+
+    fn tree_hash_packing_factor() -> usize {
+        unreachable!("Vector should never be packed.")
+    }
+
+    fn tree_hash_root(&self) -> Vec<u8> {
+        tree_hash::impls::vec_tree_hash_root(&self.vec)
+    }
+}
+
+impl<T, N: Unsigned> cached_tree_hash::CachedTreeHash for FixedLenVec<T, N>
+where
+    T: cached_tree_hash::CachedTreeHash + tree_hash::TreeHash,
+{
+    fn new_tree_hash_cache(
+        &self,
+        depth: usize,
+    ) -> Result<cached_tree_hash::TreeHashCache, cached_tree_hash::Error> {
+        let (cache, _overlay) = cached_tree_hash::vec::new_tree_hash_cache(&self.vec, depth)?;
+
+        Ok(cache)
+    }
+
+    fn tree_hash_cache_schema(&self, depth: usize) -> cached_tree_hash::BTreeSchema {
+        cached_tree_hash::vec::produce_schema(&self.vec, depth)
+    }
+
+    fn update_tree_hash_cache(
+        &self,
+        cache: &mut cached_tree_hash::TreeHashCache,
+    ) -> Result<(), cached_tree_hash::Error> {
+        cached_tree_hash::vec::update_tree_hash_cache(&self.vec, cache)?;
+
+        Ok(())
+    }
+}
+
+impl<T, N: Unsigned> ssz::Encodable for FixedLenVec<T, N>
+where
+    T: ssz::Encodable,
+{
+    fn ssz_append(&self, s: &mut ssz::SszStream) {
+        s.append_vec(&self.vec)
+    }
+}
+
+impl<T, N: Unsigned> ssz::Decodable for FixedLenVec<T, N>
+where
+    T: ssz::Decodable + Default,
+{
+    fn ssz_decode(bytes: &[u8], index: usize) -> Result<(Self, usize), ssz::DecodeError> {
+        ssz::decode_ssz_list(bytes, index).and_then(|(vec, i)| Ok((vec.into(), i)))
+    }
+}