new crate sc-light (#6235)

* sc-light

* remove unused deps

* fix line width

* move more fns to sc_light

substrate/client/light/src/lib.rs

@@ -0,0 +1,57 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2017-2020 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
+
+// This program 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.
+
+// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.
+
+//! Light client components.
+
+use sp_runtime::traits::{Block as BlockT, HashFor};
+use sc_client_api::CloneableSpawn;
+use std::sync::Arc;
+use sp_core::traits::CodeExecutor;
+
+pub mod backend;
+pub mod blockchain;
+pub mod call_executor;
+pub mod fetcher;
+
+pub use {backend::*, blockchain::*, call_executor::*, fetcher::*};
+
+/// Create an instance of fetch data checker.
+pub fn new_fetch_checker<E, B: BlockT, S: BlockchainStorage<B>>(
+	blockchain: Arc<Blockchain<S>>,
+	executor: E,
+	spawn_handle: Box<dyn CloneableSpawn>,
+) -> LightDataChecker<E, HashFor<B>, B, S>
+	where
+		E: CodeExecutor,
+{
+	LightDataChecker::new(blockchain, executor, spawn_handle)
+}
+
+/// Create an instance of light client blockchain backend.
+pub fn new_light_blockchain<B: BlockT, S: BlockchainStorage<B>>(storage: S) -> Arc<Blockchain<S>> {
+	Arc::new(Blockchain::new(storage))
+}
+
+/// Create an instance of light client backend.
+pub fn new_light_backend<B, S>(blockchain: Arc<Blockchain<S>>) -> Arc<Backend<S, HashFor<B>>>
+	where
+		B: BlockT,
+		S: BlockchainStorage<B>,
+{
+	Arc::new(Backend::new(blockchain))
+}