add substrate finality grandpa primitives for WASM

substrate/core/finality-grandpa/primitives/src/lib.rs

@@ -0,0 +1,73 @@
+// Copyright 2018 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/>.
+
+//! Primitives for GRANDPA integration, suitable for WASM compilation.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+extern crate substrate_primitives;
+extern crate sr_primitives;
+extern crate parity_codec;
+
+#[macro_use]
+extern crate parity_codec_derive;
+
+#[macro_use]
+extern crate sr_api;
+
+use substrate_primitives::AuthorityId;
+use sr_primitives::traits::{Block as BlockT, DigestFor, NumberFor};
+
+/// A scheduled change of authority set.
+#[cfg_attr(feature = "std", derive(Debug, PartialEq))]
+#[derive(Encode, Decode)]
+pub struct ScheduledChange<N> {
+	/// The new authorities after the change, along with their respective weights.
+	pub next_authorities: Vec<(AuthorityId, u64)>,
+	/// The number of blocks to delay.
+	pub delay: N,
+}
+
+/// WASM function call to check for pending changes.
+pub const PENDING_CHANGE_CALL: &str = "grandpa_pending_change";
+/// WASM function call to get current GRANDPA authorities.
+pub const AUTHORITIES_CALL: &str = "grandpa_pending_change";
+
+decl_apis! {
+	/// APIs for integrating the GRANDPA finality gadget into runtimes.
+	///
+	/// This is primarily used for negotiating authority-set changes for the
+	/// gadget. GRANDPA uses a signalling model of changing authority sets:
+	/// changes should be signalled with a delay of N blocks, and then automatically
+	/// applied in the runtime after those N blocks have passed.
+	///
+	/// The consensus protocol will coordinate the handoff externally.
+	pub trait Api<B: BlockT> {
+		/// Check a digest for pending changes.
+		/// Return `None` if there are no pending changes.
+		///
+		/// Precedence towards earlier or later digest items can be given
+		/// based on the rules of the chain.
+		///
+		/// No change should be scheduled if one is already and the delay has not
+		/// passed completely.
+		fn grandpa_pending_change(digest: DigestFor<B>) -> Option<ScheduledChange<NumberFor<B>>>;
+
+		/// Get the current GRANDPA authorities. This should not change except
+		/// for when changes are scheduled and the corresponding delay has passed.
+		fn grandpa_authorities() -> Vec<AuthorityId>;
+	}
+}