Rename polkadot-consensus -> polkadot-validation (#151)

* Initial rename of consensus -> validation

* Rename crate imports

* network: rename consensus to validation

* network: rename consensus in comments and logs

* Grumbles

* Rename tests consensus -> validation

polkadot/validation/src/shared_table/includable.rs

@@ -0,0 +1,137 @@
+// Copyright 2017 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot 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.
+
+// Polkadot 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 Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Implements a future which resolves when all of the candidates referenced are includable.
+
+use std::collections::HashMap;
+
+use futures::prelude::*;
+use futures::sync::oneshot;
+
+use polkadot_primitives::Hash;
+
+/// Track includability of a set of candidates,
+pub(super) fn track<I: IntoIterator<Item=(Hash, bool)>>(candidates: I) -> (IncludabilitySender, Includable) {
+	let (tx, rx) = oneshot::channel();
+	let tracking: HashMap<_, _> = candidates.into_iter().collect();
+	let includable_count = tracking.values().filter(|x| **x).count();
+
+	let mut sender = IncludabilitySender {
+		tracking,
+		includable_count,
+		sender: Some(tx),
+	};
+
+	sender.try_complete();
+
+	(
+		sender,
+		Includable(rx),
+	)
+}
+
+/// The sending end of the includability sender.
+pub(super) struct IncludabilitySender {
+	tracking: HashMap<Hash, bool>,
+	includable_count: usize,
+	sender: Option<oneshot::Sender<()>>,
+}
+
+impl IncludabilitySender {
+	/// update the inner candidate. wakes up the task as necessary.
+	/// returns `Err(Canceled)` if the other end has hung up.
+	///
+	/// returns `true` when this is completed and should be destroyed.
+	pub fn update_candidate(&mut self, candidate: Hash, includable: bool) -> bool {
+		use std::collections::hash_map::Entry;
+
+		match self.tracking.entry(candidate) {
+			Entry::Vacant(_) => {}
+			Entry::Occupied(mut entry) => {
+				let old = entry.insert(includable);
+				if !old && includable {
+					self.includable_count += 1;
+				} else if old && !includable {
+					self.includable_count -= 1;
+				}
+			}
+		}
+
+		self.try_complete()
+	}
+
+	/// whether the sender is completed.
+	pub fn is_complete(&self) -> bool {
+		self.sender.is_none()
+	}
+
+	fn try_complete(&mut self) -> bool {
+		if self.includable_count == self.tracking.len() {
+			if let Some(sender) = self.sender.take() {
+				let _ = sender.send(());
+			}
+
+			true
+		} else {
+			false
+		}
+	}
+}
+
+/// Future that resolves when all the candidates within are includable.
+pub struct Includable(oneshot::Receiver<()>);
+
+impl Future for Includable {
+	type Item = ();
+	type Error = oneshot::Canceled;
+
+	fn poll(&mut self) -> Poll<(), oneshot::Canceled> {
+		self.0.poll()
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+
+	#[test]
+	fn it_works() {
+		let hash1 = [1; 32].into();
+		let hash2 = [2; 32].into();
+		let hash3 = [3; 32].into();
+
+		let (mut sender, recv) = track([
+			(hash1, true),
+			(hash2, true),
+			(hash2, false), // overwrite should favor latter.
+			(hash3, true),
+		].iter().cloned());
+
+		assert!(!sender.is_complete());
+
+		// true -> false transition is possible and should be handled.
+		sender.update_candidate(hash1, false);
+		assert!(!sender.is_complete());
+
+		sender.update_candidate(hash2, true);
+		assert!(!sender.is_complete());
+
+		sender.update_candidate(hash1, true);
+		assert!(sender.is_complete());
+
+		recv.wait().unwrap();
+	}
+}