generalized fixedsized structs with macro

ethcore/src/client/ids.rs

@@ -18,6 +18,7 @@
 
 use util::hash::H256;
 use header::BlockNumber;
+use util::bytes::{FromRawBytes, FromBytesError, ToBytesWithMap, Populatable};
 
 /// Uniquely identifies block.
 #[derive(Debug, PartialEq, Clone, Hash, Eq)]
@@ -50,3 +51,7 @@ pub struct UncleId (
 	/// Position in block.
 	pub usize
 );
+
+sized_binary_map!(TransactionId);
+sized_binary_map!(UncleId);
+sized_binary_map!(BlockId);