slots: create primitives crate for consensus slots

client/consensus/babe/src/lib.rs

@@ -842,8 +842,8 @@ impl<Block, Client> Verifier<Block> for BabeVerifier<Block, Client> where
 						"Slot author {:?} is equivocating at slot {} with headers {:?} and {:?}",
 						author,
 						babe_pre_digest.slot_number(),
-						equivocation_proof.fst_header().hash(),
-						equivocation_proof.snd_header().hash(),
+						equivocation_proof.first_header.hash(),
+						equivocation_proof.second_header.hash(),
 					);
 				}
 

client/consensus/slots/Cargo.toml

@@ -18,6 +18,7 @@ sc-client-api = { version = "2.0.0-rc3", path = "../../api" }
 sp-core = { version = "2.0.0-rc3", path = "../../../primitives/core" }
 sp-application-crypto = { version = "2.0.0-rc3", path = "../../../primitives/application-crypto" }
 sp-blockchain = { version = "2.0.0-rc3", path = "../../../primitives/blockchain" }
+sp-consensus-slots = { version = "0.8.0-rc3", path = "../../../primitives/consensus/slots" }
 sp-runtime = { version = "2.0.0-rc3", path = "../../../primitives/runtime" }
 sp-state-machine = { version = "0.8.0-rc3", path = "../../../primitives/state-machine" }
 sp-api = { version = "2.0.0-rc3", path = "../../../primitives/api" }

client/consensus/slots/src/aux_schema.rs

@@ -19,6 +19,7 @@
 use codec::{Encode, Decode};
 use sc_client_api::backend::AuxStore;
 use sp_blockchain::{Result as ClientResult, Error as ClientError};
+use sp_consensus_slots::EquivocationProof;
 use sp_runtime::traits::Header;
 
 const SLOT_HEADER_MAP_KEY: &[u8] = b"slot_header_map";
@@ -44,31 +45,6 @@ fn load_decode<C, T>(backend: &C, key: &[u8]) -> ClientResult<Option<T>>
 	}
 }
 
-/// Represents an equivocation proof.
-#[derive(Debug, Clone)]
-pub struct EquivocationProof<H> {
-	slot: u64,
-	fst_header: H,
-	snd_header: H,
-}
-
-impl<H> EquivocationProof<H> {
-	/// Get the slot number where the equivocation happened.
-	pub fn slot(&self) -> u64 {
-		self.slot
-	}
-
-	/// Get the first header involved in the equivocation.
-	pub fn fst_header(&self) -> &H {
-		&self.fst_header
-	}
-
-	/// Get the second header involved in the equivocation.
-	pub fn snd_header(&self) -> &H {
-		&self.snd_header
-	}
-}
-
 /// Checks if the header is an equivocation and returns the proof in that case.
 ///
 /// Note: it detects equivocations only when slot_now - slot <= MAX_SLOT_CAPACITY.
@@ -115,8 +91,8 @@ pub fn check_equivocation<C, H, P>(
 			if header.hash() != prev_header.hash() {
 				return Ok(Some(EquivocationProof {
 					slot, // 3) and mentioning the same slot.
-					fst_header: prev_header.clone(),
-					snd_header: header.clone(),
+					first_header: prev_header.clone(),
+					second_header: header.clone(),
 				}));
 			} else {
 				// We don't need to continue in case of duplicated header,

primitives/consensus/babe/Cargo.toml

@@ -18,6 +18,7 @@ merlin = { version = "2.0", default-features = false }
 sp-std = { version = "2.0.0-rc3", default-features = false, path = "../../std" }
 sp-api = { version = "2.0.0-rc3", default-features = false, path = "../../api" }
 sp-consensus = { version = "0.8.0-rc3", optional = true, path = "../common" }
+sp-consensus-slots = { version = "0.8.0-rc3", default-features = false, path = "../slots" }
 sp-consensus-vrf = { version = "0.8.0-rc3", path = "../vrf", default-features = false }
 sp-inherents = { version = "2.0.0-rc3", default-features = false, path = "../../inherents" }
 sp-runtime = { version = "2.0.0-rc3", default-features = false, path = "../../runtime" }
@@ -32,6 +33,7 @@ std = [
 	"sp-std/std",
 	"sp-api/std",
 	"sp-consensus",
+	"sp-consensus-slots/std",
 	"sp-consensus-vrf/std",
 	"sp-inherents/std",
 	"sp-runtime/std",

primitives/consensus/babe/src/lib.rs

@@ -71,7 +71,10 @@ pub const MEDIAN_ALGORITHM_CARDINALITY: usize = 1200; // arbitrary suggestion by
 pub type AuthorityIndex = u32;
 
 /// A slot number.
-pub type SlotNumber = u64;
+pub use sp_consensus_slots::SlotNumber;
+
+/// An equivocation proof for multiple block authorships on the same slot (i.e. double vote).
+pub use sp_consensus_slots::EquivocationProof;
 
 /// The weight of an authority.
 // NOTE: we use a unique name for the weight to avoid conflicts with other

primitives/consensus/slots/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "sp-consensus-slots"
+version = "0.8.0-rc3"
+authors = ["Parity Technologies <[email protected]>"]
+description = "Primitives for slots-based consensus"
+edition = "2018"
+license = "Apache-2.0"
+homepage = "https://substrate.dev"
+repository = "https://github.com/paritytech/substrate/"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[dependencies]
+codec = { package = "parity-scale-codec", version = "1.3.0", default-features = false, features = ["derive"] }
+
+[features]
+default = ["std"]
+std = [
+	"codec/std",
+]

primitives/consensus/slots/src/lib.rs

@@ -0,0 +1,39 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2020 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Primitives for slots-based consensus engines.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use codec::{Decode, Encode};
+
+/// A slot number.
+pub type SlotNumber = u64;
+
+/// Represents an equivocation proof. An equivocation happens when a validator
+/// produces more than one block on the same slot. The proof of equivocation
+/// are the given distinct headers that were signed by the validator and which
+/// include the slot number.
+#[derive(Clone, Debug, Decode, Encode)]
+pub struct EquivocationProof<H> {
+	/// The slot number at which the equivocation happened.
+	pub slot: SlotNumber,
+	/// The first header involved in the equivocation.
+	pub first_header: H,
+	/// The second header involved in the equivocation.
+	pub second_header: H,
+}