proposal vote collector

ethcore/src/engines/propose_collect.rs

@@ -0,0 +1,130 @@
+// Copyright 2015, 2016 Ethcore (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/>.
+
+//! Voting on a hash, where each vote has to come from a set of addresses.
+
+use common::{HashSet, RwLock, H256, Signature, Address, Error, ec, Hashable, AtomicBool};
+
+/// Collect votes on a hash.
+#[derive(Debug)]
+pub struct ProposeCollect {
+	/// Proposed hash.
+	pub hash: H256,
+	/// Allowed voter addresses.
+	pub voters: HashSet<Address>,
+	/// Threshold vote number for success.
+	pub threshold: usize,
+	/// Votes.
+	votes: RwLock<HashSet<Signature>>,
+	/// Was enough votes reached.
+	is_won: AtomicBool
+}
+
+/// Voting errors.
+#[derive(Debug)]
+pub enum VoteError {
+	/// Voter is not in the voters set.
+	UnauthorisedVoter
+}
+
+impl SignedVote {
+	/// Create a new instance of BFT engine
+	pub fn new(hash: H256, voters: HashSet<Address>, threshold: usize) -> Self {
+		assert!(voters.len() > threshold);
+		SignedVote {
+			hash: hash,
+			voters: voters,
+			threshold: threshold,
+			votes: RwLock::new(HashSet::new()),
+			is_won: AtomicBool::new(false)
+		}
+	}
+
+	/// Vote on hash using the signed hash, true if vote counted.
+	pub fn vote(&self, signature: &Signature) -> bool {
+		if self.votes.contains(signature) { return false; }
+		if !self.can_vote(signature).is_ok() { return false; }
+		self.votes.try_write().unwrap().insert(signature);
+		true
+	}
+
+	fn can_vote(&self, signature: &Signature) -> Result<(), Error> {
+		let signer = Address::from(try!(ec::recover(&signature, self.hash)).sha3());
+		match self.voters.contains(&signer) {
+			false => try!(Err(VoteError::UnauthorisedVoter)),
+			true => Ok(()),
+		}
+	}
+
+	/// Some winner if voting threshold was reached.
+	pub fn winner(&self) -> Option<H256> {
+		let threshold_checker = || match self.votes.len() >= threshold {
+			true => { self.is_won.store(true, Ordering::Relaxed); true },
+			false => false,
+		};
+		match self.is_won || threshold_checker() {
+			true => Some(self.hash),
+			false => None,
+		}
+	}
+
+	/// Get signatures backing given hash.
+	pub fn votes(&self) -> HashSet<Signature> {
+		self.votes.try_read().unwrap().clone()
+	}
+}
+
+#[cfg(test)]	
+mod tests {
+	use common::*;
+	use engines::propose_collect::ProposeCollect;
+	use account_provider::AccountProvider;
+
+	#[test]
+	fn simple_propose_collect() {
+		let tap = AccountProvider::transient_provider();
+		let addr1 = tap.insert_account("1".sha3(), "1").unwrap();
+		tap.unlock_account_permanently(addr1, "1".into()).unwrap();
+
+		let addr2 = tap.insert_account("2".sha3(), "2").unwrap();
+		tap.unlock_account_permanently(addr2, "2".into()).unwrap();
+
+		let addr3 = tap.insert_account("3".sha3(), "3").unwrap();
+		tap.unlock_account_permanently(addr3, "3".into()).unwrap();
+
+		let header = Header::default();
+		let bare_hash = header.bare_hash();
+		let voters: HashSet<_> = vec![addr1, addr2].into_iter().map(Into::into).collect();
+		let vote = ProposeCollect::new(bare_hash, voters.into(), 1);
+		assert!(vote.winner().is_none());
+
+		// Unapproved voter.
+		let signature = tap.sign(addr3, bare_hash).unwrap();
+		assert!(!vote.vote(&signature.into()));
+		assert!(vote.winner().is_none());
+		// First good vote.
+		let signature = tap.sign(addr1, bare_hash).unwrap();
+		assert!(vote.vote(&signature.into()));
+		assert_eq!(vote.winner().unwrap(), bare_hash);
+		// Voting again is ineffective.
+		let signature = tap.sign(addr1, bare_hash).unwrap();
+		assert!(!vote.vote(&signature.into()));
+		// Second valid vote.
+		let signature = tap.sign(addr2, bare_hash).unwrap();
+		assert!(vote.vote(&signature.into()));
+		assert_eq!(vote.winner().unwrap(), bare_hash);
+	}
+}