openethereum/ethcore/src/engines/epoch.rs

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// Copyright 2015-2018 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/>.
//! Epoch verifiers and transitions.
use ethereum_types::H256;
use rlp::{Encodable, Decodable, DecoderError, RlpStream, Rlp};
/// A full epoch transition.
#[derive(Debug, Clone)]
pub struct Transition {
/// Block hash at which the transition occurred.
pub block_hash: H256,
/// Block number at which the transition occurred.
pub block_number: u64,
/// "transition/epoch" proof from the engine combined with a finality proof.
pub proof: Vec<u8>,
}
impl Encodable for Transition {
fn rlp_append(&self, s: &mut RlpStream) {
s.begin_list(3)
.append(&self.block_hash)
.append(&self.block_number)
.append(&self.proof);
}
}
impl Decodable for Transition {
fn decode(rlp: &Rlp) -> Result<Self, DecoderError> {
Ok(Transition {
block_hash: rlp.val_at(0)?,
block_number: rlp.val_at(1)?,
proof: rlp.val_at(2)?,
})
}
}
/// An epoch transition pending a finality proof.
/// Not all transitions need one.
pub struct PendingTransition {
/// "transition/epoch" proof from the engine.
pub proof: Vec<u8>,
}
impl Encodable for PendingTransition {
fn rlp_append(&self, s: &mut RlpStream) {
s.append(&self.proof);
}
}
impl Decodable for PendingTransition {
fn decode(rlp: &Rlp) -> Result<Self, DecoderError> {
Ok(PendingTransition {
proof: rlp.as_val()?,
})
}
}
/// Verifier for all blocks within an epoch with self-contained state.
pub trait EpochVerifier<M: ::parity_machine::Machine>: Send + Sync {
/// Lightly verify the next block header.
/// This may not be a header belonging to a different epoch.
fn verify_light(&self, header: &M::Header) -> Result<(), M::Error>;
/// Perform potentially heavier checks on the next block header.
fn verify_heavy(&self, header: &M::Header) -> Result<(), M::Error> {
self.verify_light(header)
}
/// Check a finality proof against this epoch verifier.
/// Returns `Some(hashes)` if the proof proves finality of these hashes.
/// Returns `None` if the proof doesn't prove anything.
fn check_finality_proof(&self, _proof: &[u8]) -> Option<Vec<H256>> {
None
}
}
/// Special "no-op" verifier for stateless, epoch-less engines.
pub struct NoOp;
impl<M: ::parity_machine::Machine> EpochVerifier<M> for NoOp {
fn verify_light(&self, _header: &M::Header) -> Result<(), M::Error> { Ok(()) }
}