rlp_derive (#6125)

* rlp_derive

* RlpEncodableWrapper, RlpDecodableWrapper

* use rlp_derive in parity

* fixed broken transaction Action serialization

util/rlp_derive/tests/rlp.rs

@@ -0,0 +1,44 @@
+extern crate rlp;
+#[macro_use]
+extern crate rlp_derive;
+
+use rlp::{encode, decode};
+
+#[derive(Debug, PartialEq, RlpEncodable, RlpDecodable)]
+struct Foo {
+	a: String,
+}
+
+#[derive(Debug, PartialEq, RlpEncodableWrapper, RlpDecodableWrapper)]
+struct FooWrapper {
+	a: String,
+}
+
+#[test]
+fn test_encode_foo() {
+	let foo = Foo {
+		a: "cat".into(),
+	};
+
+	let expected = vec![0xc4, 0x83, b'c', b'a', b't'];
+	let out = encode(&foo).into_vec();
+	assert_eq!(out, expected);
+
+	let decoded = decode(&expected);
+	assert_eq!(foo, decoded);
+}
+
+#[test]
+fn test_encode_foo_wrapper() {
+	let foo = FooWrapper {
+		a: "cat".into(),
+	};
+
+	let expected = vec![0x83, b'c', b'a', b't'];
+	let out = encode(&foo).into_vec();
+	assert_eq!(out, expected);
+
+	let decoded = decode(&expected);
+	assert_eq!(foo, decoded);
+}
+