Repot and introduce keccak-256 external.

substrate/wasm-runtime/polkadot/src/codec/keyedvec.rs

@@ -0,0 +1,31 @@
+use runtime_support::Vec;
+use primitives::AccountID;
+use slicable::Slicable;
+
+pub trait KeyedVec {
+	fn to_keyed_vec(&self, prepend_key: &[u8]) -> Vec<u8>;
+}
+
+impl KeyedVec for AccountID {
+	fn to_keyed_vec(&self, prepend_key: &[u8]) -> Vec<u8> {
+		let mut r = prepend_key.to_vec();
+		r.extend_from_slice(self);
+		r
+	}
+}
+
+macro_rules! impl_endians {
+	( $( $t:ty ),* ) => { $(
+		impl KeyedVec for $t {
+			fn to_keyed_vec(&self, prepend_key: &[u8]) -> Vec<u8> {
+				self.as_slice_then(|slice| {
+					let mut r = prepend_key.to_vec();
+					r.extend_from_slice(slice);
+					r
+				})
+			}
+		}
+	)* }
+}
+
+impl_endians!(u16, u32, u64, usize, i16, i32, i64, isize);