add AuraUnincludedSegmentApi

Author: rphmeier

Cargo.lock

@@ -30,6 +30,7 @@ members = [
 	"pallets/xcmp-queue",
 	"parachain-template/node",
 	"parachain-template/runtime",
+	"primitives/aura",
 	"primitives/core",
 	"primitives/parachain-inherent",
 	"primitives/timestamp",

Cargo.toml

@@ -0,0 +1,30 @@
+[package]
+name = "cumulus-primitives-aura"
+version = "0.1.0"
+authors = ["Parity Technologies <[email protected]>"]
+edition = "2021"
+
+[dependencies]
+codec = { package = "parity-scale-codec", version = "3.0.0", default-features = false, features = [ "derive" ] }
+
+# Substrate
+sp-api = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
+sp-consensus-aura = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
+sp-runtime = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
+sp-std = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
+
+# Polkadot
+polkadot-core-primitives = { git = "https://github.com/paritytech/polkadot", default-features = false, branch = "master" }
+polkadot-primitives = { git = "https://github.com/paritytech/polkadot", default-features = false, branch = "master" }
+
+[features]
+default = [ "std" ]
+std = [
+	"codec/std",
+	"sp-api/std",
+	"sp-consensus-aura/std",
+	"sp-runtime/std",
+	"sp-std/std",
+	"polkadot-core-primitives/std",
+	"polkadot-primitives/std",
+]

primitives/aura/Cargo.toml

@@ -0,0 +1,46 @@
+// Copyright 2023 Parity Technologies (UK) Ltd.
+// This file is part of Cumulus.
+
+// 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 Cumulus.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Core primitives for Aura in Cumulus.
+//!
+//! In particular, this exposes the [`AuraUnincludedSegmentApi`] which is used to regulate
+//! the behavior of Aura within a parachain context.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+pub use sp_consensus_aura::Slot;
+
+sp_api::decl_runtime_apis! {
+	/// This runtime API is used to inform potential block authors whether they will
+	/// have the right to author at a slot, assuming they have claimed the slot.
+	///
+	/// In particular, this API allows Aura-based parachains to regulate their "unincluded segment",
+	/// which is the section of the head of the chain which has not yet been made available in the
+	/// relay chain.
+	///
+	/// When the unincluded segment is short, Aura chains will allow authors to create multiple
+	/// blocks per slot in order to build a backlog. When it is saturated, this API will limit
+	/// the amount of blocks that can be created.
+	pub trait AuraUnincludedSegmentApi {
+		/// Whether it is legal to extend the chain, assuming the given block is the most
+		/// recently included one as-of the relay parent that will be built against, and
+		/// the given slot.
+		///
+		/// This should be consistent with the logic the runtime uses when validating blocks to
+		/// avoid issues.
+		fn can_build_upon(included_hash: Block::Hash, slot: Slot) -> bool;
+	}
+}