Upgrade BLS to new SSZ

eth2/utils/bls/src/macros.rs

@@ -0,0 +1,38 @@
+macro_rules! impl_ssz {
+    ($type: ident, $byte_size: expr, $item_str: expr) => {
+        impl ssz::Encodable for $type {
+            fn is_ssz_fixed_len() -> bool {
+                true
+            }
+
+            fn ssz_fixed_len() -> usize {
+                $byte_size
+            }
+
+            fn ssz_append(&self, buf: &mut Vec<u8>) {
+                buf.append(&mut self.as_bytes())
+            }
+        }
+
+        impl ssz::Decodable for $type {
+            fn is_ssz_fixed_len() -> bool {
+                true
+            }
+
+            fn ssz_fixed_len() -> usize {
+                $byte_size
+            }
+
+            fn from_ssz_bytes(bytes: &[u8]) -> Result<Self, DecodeError> {
+                let len = bytes.len();
+                let expected = <Self as ssz::Decodable>::ssz_fixed_len();
+
+                if len != expected {
+                    Err(ssz::DecodeError::InvalidByteLength { len, expected })
+                } else {
+                    $type::from_bytes(bytes)
+                }
+            }
+        }
+    };
+}