Light-client sync for contract-based PoA

ethcore/light/src/client/fetch.rs

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+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity 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.
+
+// Parity 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 Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Trait for fetching chain data.
+
+use std::sync::Arc;
+
+use ethcore::encoded;
+use ethcore::engines::{Engine, StateDependentProof};
+use ethcore::header::Header;
+use ethcore::receipt::Receipt;
+use futures::future::IntoFuture;
+use util::H256;
+
+/// Provides full chain data.
+pub trait ChainDataFetcher: Send + Sync + 'static {
+	/// Error type when data unavailable.
+	type Error: ::std::fmt::Debug;
+
+	/// Future for fetching block body.
+	type Body: IntoFuture<Item=encoded::Block, Error=Self::Error>;
+	/// Future for fetching block receipts.
+	type Receipts: IntoFuture<Item=Vec<Receipt>, Error=Self::Error>;
+	/// Future for fetching epoch transition
+	type Transition: IntoFuture<Item=Vec<u8>, Error=Self::Error>;
+
+	/// Fetch a block body.
+	fn block_body(&self, header: &Header) -> Self::Body;
+
+	/// Fetch block receipts.
+	fn block_receipts(&self, header: &Header) -> Self::Receipts;
+
+	/// Fetch epoch transition proof at given header.
+	fn epoch_transition(&self, hash: H256, engine: Arc<Engine>, checker: Arc<StateDependentProof>) -> Self::Transition;
+}
+
+/// Fetcher implementation which cannot fetch anything.
+pub struct Unavailable;
+
+/// Create a fetcher which has all data unavailable.
+pub fn unavailable() -> Unavailable { Unavailable }
+
+impl ChainDataFetcher for Unavailable {
+	type Error = &'static str;
+
+	type Body = Result<encoded::Block, &'static str>;
+	type Receipts = Result<Vec<Receipt>, &'static str>;
+	type Transition = Result<Vec<u8>, &'static str>;
+
+	fn block_body(&self, _header: &Header) -> Self::Body {
+		Err("fetching block bodies unavailable")
+	}
+
+	fn block_receipts(&self, _header: &Header) -> Self::Receipts {
+		Err("fetching block receipts unavailable")
+	}
+
+	fn epoch_transition(&self, _h: H256, _e: Arc<Engine>, _check: Arc<StateDependentProof>) -> Self::Transition {
+		Err("fetching epoch transition proofs unavailable")
+	}
+}