RPC api for offchain storage (#4694)

* Rpc api for offchain storage

* Replace Vec<u8> to Bytes, replace Mutex to RwLock

* Remove pub

* Modify copyright year

substrate/client/rpc/src/offchain/tests.rs

@@ -0,0 +1,36 @@
+// Copyright 2020 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+use super::*;
+use assert_matches::assert_matches;
+use sp_core::{Bytes, offchain::storage::InMemOffchainStorage};
+
+#[test]
+fn local_storage_should_work() {
+	let storage = InMemOffchainStorage::default();
+	let offchain = Offchain::new(storage);
+	let key = Bytes(b"offchain_storage".to_vec());
+	let value = Bytes(b"offchain_value".to_vec());
+
+	assert_matches!(
+		offchain.set_local_storage(StorageKind::PERSISTENT, key.clone(), value.clone()),
+		Ok(())
+	);
+	assert_matches!(
+		offchain.get_local_storage(StorageKind::PERSISTENT, key),
+		Ok(Some(ref v)) if *v == value
+	);
+}