Merge branch 'master' into check-updates

ethcore/light/Cargo.toml

@@ -5,6 +5,10 @@ license = "GPL-3.0"
 name = "ethcore-light"
 version = "1.5.0"
 authors = ["Ethcore <admin@ethcore.io>"]
+build = "build.rs"
+
+[build-dependencies]
+"ethcore-ipc-codegen" = { path = "../../ipc/codegen" }
 
 [dependencies]
 log = "0.3"
@@ -12,5 +16,6 @@ ethcore = { path = ".." }
 ethcore-util = { path = "../../util" }
 ethcore-network = { path = "../../util/network" }
 ethcore-io = { path = "../../util/io" }
+ethcore-ipc = { path = "../../ipc/rpc" }
 rlp = { path = "../../util/rlp" }
 time = "0.1"

ethcore/light/build.rs

@@ -0,0 +1,21 @@
+// 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/>.
+
+extern crate ethcore_ipc_codegen;
+
+fn main() {
+	ethcore_ipc_codegen::derive_binary("src/types/mod.rs.in").unwrap();
+}

ethcore/light/src/client.rs

@@ -101,7 +101,7 @@ impl Provider for Client {
 		Vec::new()
 	}
 
-	fn code(&self, _req: request::ContractCodes) -> Vec<Bytes> {
+	fn contract_code(&self, _req: request::ContractCodes) -> Vec<Bytes> {
 		Vec::new()
 	}
 

ethcore/light/src/lib.rs

@@ -28,20 +28,25 @@
 //! It starts by performing a header-only sync, verifying random samples
 //! of members of the chain to varying degrees.
 
-// TODO: remove when integrating with parity.
+// TODO: remove when integrating with the rest of parity.
 #![allow(dead_code)]
 
 pub mod client;
 pub mod net;
 pub mod provider;
-pub mod request;
 
+mod types;
+
+pub use self::provider::Provider;
+pub use types::les_request as request;
+
+#[macro_use]
+extern crate log;
+
+extern crate ethcore;
 extern crate ethcore_util as util;
 extern crate ethcore_network as network;
 extern crate ethcore_io as io;
-extern crate ethcore;
+extern crate ethcore_ipc as ipc;
 extern crate rlp;
-extern crate time;
-
-#[macro_use]
-extern crate log;
+extern crate time;

ethcore/light/src/net/buffer_flow.rs

@@ -206,6 +206,39 @@ impl FlowParams {
 		cost.0 + (amount * cost.1)
 	}
 
+	/// Compute the maximum number of costs of a specific kind which can be made 
+	/// with the given buffer.
+	/// Saturates at `usize::max()`. This is not a problem in practice because
+	/// this amount of requests is already prohibitively large.
+	pub fn max_amount(&self, buffer: &Buffer, kind: request::Kind) -> usize {
+		use util::Uint;
+		use std::usize;
+
+		let cost = match kind {
+			request::Kind::Headers => &self.costs.headers,
+			request::Kind::Bodies => &self.costs.bodies,
+			request::Kind::Receipts => &self.costs.receipts,
+			request::Kind::StateProofs => &self.costs.state_proofs,
+			request::Kind::Codes => &self.costs.contract_codes,
+			request::Kind::HeaderProofs => &self.costs.header_proofs,
+		};
+
+		let start = buffer.current();
+
+		if start <= cost.0 {
+			return 0;
+		} else if cost.1 == U256::zero() {
+			return usize::MAX;
+		}
+
+		let max = (start - cost.0) / cost.1;
+		if max >= usize::MAX.into() {
+			usize::MAX
+		} else {
+			max.as_u64() as usize
+		}
+	}
+
 	/// Create initial buffer parameter.
 	pub fn create_buffer(&self) -> Buffer {
 		Buffer {
@@ -228,6 +261,16 @@ impl FlowParams {
 
 		buf.estimate = ::std::cmp::min(self.limit, buf.estimate + (elapsed * self.recharge));
 	}
+
+	/// Refund some buffer which was previously deducted.
+	/// Does not update the recharge timestamp.
+	pub fn refund(&self, buf: &mut Buffer, refund_amount: U256) {
+		buf.estimate = buf.estimate + refund_amount;
+
+		if buf.estimate > self.limit {
+			buf.estimate = self.limit
+		}
+	}
 }
 
 #[cfg(test)]

ethcore/light/src/net/error.rs

@@ -52,6 +52,8 @@ pub enum Error {
 	UnexpectedHandshake,
 	/// Peer on wrong network (wrong NetworkId or genesis hash)
 	WrongNetwork,
+	/// Unknown peer.
+	UnknownPeer,
 }
 
 impl Error {
@@ -64,6 +66,7 @@ impl Error {
 			Error::UnrecognizedPacket(_) => Punishment::Disconnect,
 			Error::UnexpectedHandshake => Punishment::Disconnect,
 			Error::WrongNetwork => Punishment::Disable,
+			Error::UnknownPeer => Punishment::Disconnect,
 		}
 	}
 }
@@ -89,6 +92,7 @@ impl fmt::Display for Error {
 			Error::UnrecognizedPacket(code) => write!(f, "Unrecognized packet: 0x{:x}", code),
 			Error::UnexpectedHandshake => write!(f, "Unexpected handshake"),
 			Error::WrongNetwork => write!(f, "Wrong network"),
+			Error::UnknownPeer => write!(f, "unknown peer"),
 		}
 	}
 }

ethcore/light/src/net/mod.rs

@@ -19,27 +19,28 @@
 //! This uses a "Provider" to answer requests.
 //! See https://github.com/ethcore/parity/wiki/Light-Ethereum-Subprotocol-(LES)
 
+use ethcore::transaction::SignedTransaction;
 use io::TimerToken;
 use network::{NetworkProtocolHandler, NetworkContext, NetworkError, PeerId};
 use rlp::{RlpStream, Stream, UntrustedRlp, View};
 use util::hash::H256;
-use util::RwLock;
+use util::{Mutex, RwLock, U256};
+use time::SteadyTime;
 
 use std::collections::{HashMap, HashSet};
-use std::sync::atomic::AtomicUsize;
+use std::sync::atomic::{AtomicUsize, Ordering};
 
 use provider::Provider;
 use request::{self, Request};
 
 use self::buffer_flow::{Buffer, FlowParams};
 use self::error::{Error, Punishment};
-use self::status::{Status, Capabilities};
 
 mod buffer_flow;
 mod error;
 mod status;
 
-pub use self::status::Announcement;
+pub use self::status::{Status, Capabilities, Announcement, NetworkId};
 
 const TIMEOUT: TimerToken = 0;
 const TIMEOUT_INTERVAL_MS: u64 = 1000;
@@ -86,6 +87,10 @@ mod packet {
 	pub const HEADER_PROOFS: u8 = 0x0e;
 }
 
+/// A request id.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct ReqId(usize);
+
 // A pending peer: one we've sent our status to but
 // may not have received one for.
 struct PendingPeer {
@@ -103,32 +108,162 @@ struct Peer {
 	sent_head: H256, // last head we've given them.
 }
 
+impl Peer {
+	// check the maximum cost of a request, returning an error if there's
+	// not enough buffer left.
+	// returns the calculated maximum cost.
+	fn deduct_max(&mut self, flow_params: &FlowParams, kind: request::Kind, max: usize) -> Result<U256, Error> {
+		flow_params.recharge(&mut self.local_buffer);
+
+		let max_cost = flow_params.compute_cost(kind, max);
+		try!(self.local_buffer.deduct_cost(max_cost));
+		Ok(max_cost)
+	}
+
+	// refund buffer for a request. returns new buffer amount.
+	fn refund(&mut self, flow_params: &FlowParams, amount: U256) -> U256 {
+		flow_params.refund(&mut self.local_buffer, amount);
+
+		self.local_buffer.current()
+	}
+
+	// recharge remote buffer with remote flow params.
+	fn recharge_remote(&mut self) {
+		let flow = &mut self.remote_flow;
+		flow.recharge(&mut self.remote_buffer);
+	}
+}
+
+/// An LES event handler.
+pub trait Handler: Send + Sync {
+	/// Called when a peer connects.
+	fn on_connect(&self, _id: PeerId, _status: &Status, _capabilities: &Capabilities) { }
+	/// Called when a peer disconnects
+	fn on_disconnect(&self, _id: PeerId) { }
+	/// Called when a peer makes an announcement.
+	fn on_announcement(&self, _id: PeerId, _announcement: &Announcement) { }
+	/// Called when a peer requests relay of some transactions.
+	fn on_transactions(&self, _id: PeerId, _relay: &[SignedTransaction]) { }
+}
+
+// a request and the time it was made.
+struct Requested {
+	request: Request,
+	timestamp: SteadyTime,
+}
+
+/// Protocol parameters.
+pub struct Params {
+	/// Genesis hash.
+	pub genesis_hash: H256,
+	/// Network id.
+	pub network_id: NetworkId,
+	/// Buffer flow parameters.
+	pub flow_params: FlowParams,
+	/// Initial capabilities.
+	pub capabilities: Capabilities,
+}
+
 /// This is an implementation of the light ethereum network protocol, abstracted
 /// over a `Provider` of data and a p2p network.
 ///
 /// This is simply designed for request-response purposes. Higher level uses
 /// of the protocol, such as synchronization, will function as wrappers around
 /// this system.
+// 
+// LOCK ORDER:
+//   Locks must be acquired in the order declared, and when holding a read lock 
+//   on the peers, only one peer may be held at a time.
 pub struct LightProtocol {
 	provider: Box<Provider>,
 	genesis_hash: H256,
-	network_id: status::NetworkId,
+	network_id: NetworkId,
 	pending_peers: RwLock<HashMap<PeerId, PendingPeer>>,
-	peers: RwLock<HashMap<PeerId, Peer>>,
-	pending_requests: RwLock<HashMap<usize, Request>>,
+	peers: RwLock<HashMap<PeerId, Mutex<Peer>>>,
+	pending_requests: RwLock<HashMap<usize, Requested>>,
 	capabilities: RwLock<Capabilities>,
 	flow_params: FlowParams, // assumed static and same for every peer.
+	handlers: Vec<Box<Handler>>,
 	req_id: AtomicUsize,
 }
 
 impl LightProtocol {
+	/// Create a new instance of the protocol manager.
+	pub fn new(provider: Box<Provider>, params: Params) -> Self {
+		LightProtocol {
+			provider: provider,
+			genesis_hash: params.genesis_hash,
+			network_id: params.network_id,
+			pending_peers: RwLock::new(HashMap::new()),
+			peers: RwLock::new(HashMap::new()),
+			pending_requests: RwLock::new(HashMap::new()),
+			capabilities: RwLock::new(params.capabilities),
+			flow_params: params.flow_params,
+			handlers: Vec::new(),
+			req_id: AtomicUsize::new(0),
+		}
+	}
+
+	/// Check the maximum amount of requests of a specific type 
+	/// which a peer would be able to serve.
+	pub fn max_requests(&self, peer: PeerId, kind: request::Kind) -> Option<usize> {
+		self.peers.read().get(&peer).map(|peer| {
+			let mut peer = peer.lock();
+			peer.recharge_remote();
+			peer.remote_flow.max_amount(&peer.remote_buffer, kind)
+		})
+	}
+
+	/// Make a request to a peer. 
+	///
+	/// Fails on: nonexistent peer, network error,
+	/// insufficient buffer. Does not check capabilities before sending.
+	/// On success, returns a request id which can later be coordinated 
+	/// with an event.
+	pub fn request_from(&self, io: &NetworkContext, peer_id: &PeerId, request: Request) -> Result<ReqId, Error> {
+		let peers = self.peers.read();
+		let peer = try!(peers.get(peer_id).ok_or_else(|| Error::UnknownPeer));
+		let mut peer = peer.lock();
+
+		peer.recharge_remote();
+
+		let max = peer.remote_flow.compute_cost(request.kind(), request.amount());
+		try!(peer.remote_buffer.deduct_cost(max));
+
+		let req_id = self.req_id.fetch_add(1, Ordering::SeqCst);
+		let packet_data = encode_request(&request, req_id);
+
+		let packet_id = match request.kind() {
+			request::Kind::Headers => packet::GET_BLOCK_HEADERS,
+			request::Kind::Bodies => packet::GET_BLOCK_BODIES,
+			request::Kind::Receipts => packet::GET_RECEIPTS,
+			request::Kind::StateProofs => packet::GET_PROOFS,
+			request::Kind::Codes => packet::GET_CONTRACT_CODES,
+			request::Kind::HeaderProofs => packet::GET_HEADER_PROOFS,
+		};
+
+		try!(io.send(*peer_id, packet_id, packet_data));
+
+		peer.current_asking.insert(req_id);
+		self.pending_requests.write().insert(req_id, Requested {
+			request: request,
+			timestamp: SteadyTime::now(),
+		});
+
+		Ok(ReqId(req_id))
+	}
+
 	/// Make an announcement of new chain head and capabilities to all peers.
 	/// The announcement is expected to be valid.
-	pub fn make_announcement(&self, mut announcement: Announcement, io: &NetworkContext) {
+	pub fn make_announcement(&self, io: &NetworkContext, mut announcement: Announcement) {
 		let mut reorgs_map = HashMap::new();
 
+		// update stored capabilities
+		self.capabilities.write().update_from(&announcement);
+
 		// calculate reorg info and send packets
-		for (peer_id, peer_info) in self.peers.write().iter_mut() {
+		for (peer_id, peer_info) in self.peers.read().iter() {
+			let mut peer_info = peer_info.lock();
 			let reorg_depth = reorgs_map.entry(peer_info.sent_head)
 				.or_insert_with(|| {
 					match self.provider.reorg_depth(&announcement.head_hash, &peer_info.sent_head) {
@@ -151,6 +286,14 @@ impl LightProtocol {
 			}
 		}
 	}
+
+	/// Add an event handler.
+	/// Ownership will be transferred to the protocol structure,
+	/// and the handler will be kept alive as long as it is.
+	/// These are intended to be added at the beginning of the 
+	pub fn add_handler(&mut self, handler: Box<Handler>) {
+		self.handlers.push(handler);
+	}
 }
 
 impl LightProtocol {
@@ -173,7 +316,11 @@ impl LightProtocol {
 	fn on_disconnect(&self, peer: PeerId) {
 		// TODO: reassign all requests assigned to this peer.
 		self.pending_peers.write().remove(&peer);
-		self.peers.write().remove(&peer);
+		if self.peers.write().remove(&peer).is_some() {
+			for handler in &self.handlers {
+				handler.on_disconnect(peer)
+			}	
+		}
 	}
 
 	// send status to a peer.
@@ -219,15 +366,19 @@ impl LightProtocol {
 			return Err(Error::WrongNetwork);
 		}
 
-		self.peers.write().insert(*peer, Peer {
+		self.peers.write().insert(*peer, Mutex::new(Peer {
 			local_buffer: self.flow_params.create_buffer(),
 			remote_buffer: flow_params.create_buffer(),
 			current_asking: HashSet::new(),
-			status: status,
-			capabilities: capabilities,
+			status: status.clone(),
+			capabilities: capabilities.clone(),
 			remote_flow: flow_params,
 			sent_head: pending.sent_head,
-		});
+		}));
+
+		for handler in &self.handlers {
+			handler.on_connect(*peer, &status, &capabilities)
+		}
 
 		Ok(())
 	}
@@ -240,13 +391,15 @@ impl LightProtocol {
 		}
 
 		let announcement = try!(status::parse_announcement(data));
-		let mut peers = self.peers.write();
+		let peers = self.peers.read();
 
-		let peer_info = match peers.get_mut(peer) {
+		let peer_info = match peers.get(peer) {
 			Some(info) => info,
 			None => return Ok(()),
 		};
 
+		let mut peer_info = peer_info.lock();
+
 		// update status.
 		{
 			// TODO: punish peer if they've moved backwards.
@@ -259,15 +412,11 @@ impl LightProtocol {
 		}
 
 		// update capabilities.
-		{
-			let caps = &mut peer_info.capabilities;
-			caps.serve_headers = caps.serve_headers || announcement.serve_headers;
-			caps.serve_state_since = caps.serve_state_since.or(announcement.serve_state_since);
-			caps.serve_chain_since = caps.serve_chain_since.or(announcement.serve_chain_since);
-			caps.tx_relay = caps.tx_relay || announcement.tx_relay;
-		}
+		peer_info.capabilities.update_from(&announcement);
 
-		// TODO: notify listeners if new best block.
+		for handler in &self.handlers {
+			handler.on_announcement(*peer, &announcement);
+		}
 
 		Ok(())
 	}
@@ -276,45 +425,39 @@ impl LightProtocol {
 	fn get_block_headers(&self, peer: &PeerId, io: &NetworkContext, data: UntrustedRlp) -> Result<(), Error> {
 		const MAX_HEADERS: usize = 512;
 
-		let mut present_buffer = match self.peers.read().get(peer) {
-			Some(peer) => peer.local_buffer.clone(),
+		let peers = self.peers.read();
+		let peer = match peers.get(peer) {
+			Some(peer) => peer,
 			None => {
-				debug!(target: "les", "Ignoring announcement from unknown peer");
+				debug!(target: "les", "Ignoring request from unknown peer");
 				return Ok(())
 			}
 		};
 
-		self.flow_params.recharge(&mut present_buffer);
+		let mut peer = peer.lock();
+
 		let req_id: u64 = try!(data.val_at(0));
 
+		let block = {
+			let rlp = try!(data.at(1));
+			(try!(rlp.val_at(0)), try!(rlp.val_at(1)))
+		};
+
 		let req = request::Headers {
-			block: {
-				let rlp = try!(data.at(1));
-				(try!(rlp.val_at(0)), try!(rlp.val_at(1)))
-			},
+			block_num: block.0,
+			block_hash: block.1,
 			max: ::std::cmp::min(MAX_HEADERS, try!(data.val_at(2))),
 			skip: try!(data.val_at(3)),
 			reverse: try!(data.val_at(4)),
 		};
 
-		let max_cost = self.flow_params.compute_cost(request::Kind::Headers, req.max);
-		try!(present_buffer.deduct_cost(max_cost));
+		let max_cost = try!(peer.deduct_max(&self.flow_params, request::Kind::Headers, req.max));
 
 		let response = self.provider.block_headers(req);
 		let actual_cost = self.flow_params.compute_cost(request::Kind::Headers, response.len());
+		assert!(max_cost >= actual_cost, "Actual cost exceeded maximum computed cost.");
 
-		let cur_buffer = match self.peers.write().get_mut(peer) {
-			Some(peer) => {
-				self.flow_params.recharge(&mut peer.local_buffer);
-				try!(peer.local_buffer.deduct_cost(actual_cost));
-				peer.local_buffer.current()
-			}
-			None => {
-				debug!(target: "les", "peer disconnected during serving of request.");
-				return Ok(())
-			}
-		};
-
+		let cur_buffer = peer.refund(&self.flow_params, max_cost - actual_cost);
 		io.respond(packet::BLOCK_HEADERS, {
 			let mut stream = RlpStream::new_list(response.len() + 2);
 			stream.append(&req_id).append(&cur_buffer);
@@ -336,39 +479,30 @@ impl LightProtocol {
 	fn get_block_bodies(&self, peer: &PeerId, io: &NetworkContext, data: UntrustedRlp) -> Result<(), Error> {
 		const MAX_BODIES: usize = 256;
 
-		let mut present_buffer = match self.peers.read().get(peer) {
-			Some(peer) => peer.local_buffer.clone(),
+		let peers = self.peers.read();
+		let peer = match peers.get(peer) {
+			Some(peer) => peer,
 			None => {
-				debug!(target: "les", "Ignoring announcement from unknown peer");
+				debug!(target: "les", "Ignoring request from unknown peer");
 				return Ok(())
 			}
 		};
+		let mut peer = peer.lock();
 
-		self.flow_params.recharge(&mut present_buffer);
 		let req_id: u64 = try!(data.val_at(0));
 
 		let req = request::Bodies {
 			block_hashes: try!(data.iter().skip(1).take(MAX_BODIES).map(|x| x.as_val()).collect())
 		};
 
-		let max_cost = self.flow_params.compute_cost(request::Kind::Bodies, req.block_hashes.len());
-		try!(present_buffer.deduct_cost(max_cost));
+		let max_cost = try!(peer.deduct_max(&self.flow_params, request::Kind::Bodies, req.block_hashes.len()));
 
 		let response = self.provider.block_bodies(req);
 		let response_len = response.iter().filter(|x| &x[..] != &::rlp::EMPTY_LIST_RLP).count();
 		let actual_cost = self.flow_params.compute_cost(request::Kind::Bodies, response_len);
+		assert!(max_cost >= actual_cost, "Actual cost exceeded maximum computed cost.");
 
-		let cur_buffer = match self.peers.write().get_mut(peer) {
-			Some(peer) => {
-				self.flow_params.recharge(&mut peer.local_buffer);
-				try!(peer.local_buffer.deduct_cost(actual_cost));
-				peer.local_buffer.current()
-			}
-			None => {
-				debug!(target: "les", "peer disconnected during serving of request.");
-				return Ok(())
-			}
-		};
+		let cur_buffer = peer.refund(&self.flow_params, max_cost - actual_cost);
 
 		io.respond(packet::BLOCK_BODIES, {
 			let mut stream = RlpStream::new_list(response.len() + 2);
@@ -388,8 +522,44 @@ impl LightProtocol {
 	}
 
 	// Handle a request for receipts.
-	fn get_receipts(&self, _: &PeerId, _: &NetworkContext, _: UntrustedRlp) -> Result<(), Error> {
-		unimplemented!()
+	fn get_receipts(&self, peer: &PeerId, io: &NetworkContext, data: UntrustedRlp) -> Result<(), Error> {
+		const MAX_RECEIPTS: usize = 256;
+
+		let peers = self.peers.read();
+		let peer = match peers.get(peer) {
+			Some(peer) => peer,
+			None => {
+				debug!(target: "les", "Ignoring request from unknown peer");
+				return Ok(())
+			}
+		};
+		let mut peer = peer.lock();
+
+		let req_id: u64 = try!(data.val_at(0));
+
+		let req = request::Receipts {
+			block_hashes: try!(data.iter().skip(1).take(MAX_RECEIPTS).map(|x| x.as_val()).collect())
+		};
+
+		let max_cost = try!(peer.deduct_max(&self.flow_params, request::Kind::Receipts, req.block_hashes.len()));
+
+		let response = self.provider.receipts(req);
+		let response_len = response.iter().filter(|x| &x[..] != &::rlp::EMPTY_LIST_RLP).count();
+		let actual_cost = self.flow_params.compute_cost(request::Kind::Receipts, response_len);
+		assert!(max_cost >= actual_cost, "Actual cost exceeded maximum computed cost.");
+
+		let cur_buffer = peer.refund(&self.flow_params, max_cost - actual_cost);
+
+		io.respond(packet::RECEIPTS, {
+			let mut stream = RlpStream::new_list(response.len() + 2);
+			stream.append(&req_id).append(&cur_buffer);
+
+			for receipts in response {
+				stream.append_raw(&receipts, 1);
+			}
+
+			stream.out()
+		}).map_err(Into::into)
 	}
 
 	// Receive a response for receipts.
@@ -398,8 +568,55 @@ impl LightProtocol {
 	}
 
 	// Handle a request for proofs.
-	fn get_proofs(&self, _: &PeerId, _: &NetworkContext, _: UntrustedRlp) -> Result<(), Error> {
-		unimplemented!()
+	fn get_proofs(&self, peer: &PeerId, io: &NetworkContext, data: UntrustedRlp) -> Result<(), Error> {
+		const MAX_PROOFS: usize = 128;
+
+		let peers = self.peers.read();
+		let peer = match peers.get(peer) {
+			Some(peer) => peer,
+			None => {
+				debug!(target: "les", "Ignoring request from unknown peer");
+				return Ok(())
+			}
+		};
+		let mut peer = peer.lock();
+
+		let req_id: u64 = try!(data.val_at(0));
+
+		let req = {
+			let requests: Result<Vec<_>, Error> = data.iter().skip(1).take(MAX_PROOFS).map(|x| {
+				Ok(request::StateProof {
+					block: try!(x.val_at(0)),
+					key1: try!(x.val_at(1)),
+					key2: if try!(x.at(2)).is_empty() { None } else { Some(try!(x.val_at(2))) },
+					from_level: try!(x.val_at(3)),
+				})
+			}).collect();
+
+			request::StateProofs {
+				requests: try!(requests),
+			}
+		};
+
+		let max_cost = try!(peer.deduct_max(&self.flow_params, request::Kind::StateProofs, req.requests.len()));
+
+		let response = self.provider.proofs(req);
+		let response_len = response.iter().filter(|x| &x[..] != &::rlp::EMPTY_LIST_RLP).count();
+		let actual_cost = self.flow_params.compute_cost(request::Kind::StateProofs, response_len);
+		assert!(max_cost >= actual_cost, "Actual cost exceeded maximum computed cost.");
+
+		let cur_buffer = peer.refund(&self.flow_params, max_cost - actual_cost);
+
+		io.respond(packet::PROOFS, {
+			let mut stream = RlpStream::new_list(response.len() + 2);
+			stream.append(&req_id).append(&cur_buffer);
+
+			for proof in response {
+				stream.append_raw(&proof, 1);
+			}
+
+			stream.out()
+		}).map_err(Into::into)
 	}
 
 	// Receive a response for proofs.
@@ -408,8 +625,53 @@ impl LightProtocol {
 	}
 
 	// Handle a request for contract code.
-	fn get_contract_code(&self, _: &PeerId, _: &NetworkContext, _: UntrustedRlp) -> Result<(), Error> {
-		unimplemented!()
+	fn get_contract_code(&self, peer: &PeerId, io: &NetworkContext, data: UntrustedRlp) -> Result<(), Error> {
+		const MAX_CODES: usize = 256;
+
+		let peers = self.peers.read();
+		let peer = match peers.get(peer) {
+			Some(peer) => peer,
+			None => {
+				debug!(target: "les", "Ignoring request from unknown peer");
+				return Ok(())
+			}
+		};
+		let mut peer = peer.lock();
+
+		let req_id: u64 = try!(data.val_at(0));
+
+		let req = {
+			let requests: Result<Vec<_>, Error> = data.iter().skip(1).take(MAX_CODES).map(|x| {
+				Ok(request::ContractCode {
+					block_hash: try!(x.val_at(0)),
+					account_key: try!(x.val_at(1)),
+				})
+			}).collect();
+
+			request::ContractCodes {
+				code_requests: try!(requests),
+			}
+		};
+
+		let max_cost = try!(peer.deduct_max(&self.flow_params, request::Kind::Codes, req.code_requests.len()));
+
+		let response = self.provider.contract_code(req);
+		let response_len = response.iter().filter(|x| !x.is_empty()).count();
+		let actual_cost = self.flow_params.compute_cost(request::Kind::Codes, response_len);
+		assert!(max_cost >= actual_cost, "Actual cost exceeded maximum computed cost.");
+
+		let cur_buffer = peer.refund(&self.flow_params, max_cost - actual_cost);
+
+		io.respond(packet::CONTRACT_CODES, {
+			let mut stream = RlpStream::new_list(response.len() + 2);
+			stream.append(&req_id).append(&cur_buffer);
+
+			for code in response {
+				stream.append_raw(&code, 1);
+			}
+
+			stream.out()
+		}).map_err(Into::into)
 	}
 
 	// Receive a response for contract code.
@@ -418,8 +680,54 @@ impl LightProtocol {
 	}
 
 	// Handle a request for header proofs
-	fn get_header_proofs(&self, _: &PeerId, _: &NetworkContext, _: UntrustedRlp) -> Result<(), Error> {
-		unimplemented!()
+	fn get_header_proofs(&self, peer: &PeerId, io: &NetworkContext, data: UntrustedRlp) -> Result<(), Error> {
+		const MAX_PROOFS: usize = 256;
+
+		let peers = self.peers.read();
+		let peer = match peers.get(peer) {
+			Some(peer) => peer,
+			None => {
+				debug!(target: "les", "Ignoring request from unknown peer");
+				return Ok(())
+			}
+		};
+		let mut peer = peer.lock();
+
+		let req_id: u64 = try!(data.val_at(0));
+
+		let req = {
+			let requests: Result<Vec<_>, Error> = data.iter().skip(1).take(MAX_PROOFS).map(|x| {
+				Ok(request::HeaderProof {
+					cht_number: try!(x.val_at(0)),
+					block_number: try!(x.val_at(1)),
+					from_level: try!(x.val_at(2)),
+				})
+			}).collect();
+
+			request::HeaderProofs {
+				requests: try!(requests),
+			}
+		};
+
+		let max_cost = try!(peer.deduct_max(&self.flow_params, request::Kind::HeaderProofs, req.requests.len()));
+
+		let response = self.provider.header_proofs(req);
+		let response_len = response.iter().filter(|x| &x[..] != ::rlp::EMPTY_LIST_RLP).count();
+		let actual_cost = self.flow_params.compute_cost(request::Kind::HeaderProofs, response_len);
+		assert!(max_cost >= actual_cost, "Actual cost exceeded maximum computed cost.");
+
+		let cur_buffer = peer.refund(&self.flow_params, max_cost - actual_cost);
+
+		io.respond(packet::HEADER_PROOFS, {
+			let mut stream = RlpStream::new_list(response.len() + 2);
+			stream.append(&req_id).append(&cur_buffer);
+
+			for proof in response {
+				stream.append_raw(&proof, 1);
+			}
+
+			stream.out()
+		}).map_err(Into::into)
 	}
 
 	// Receive a response for header proofs
@@ -428,8 +736,18 @@ impl LightProtocol {
 	}
 
 	// Receive a set of transactions to relay.
-	fn relay_transactions(&self, _: &PeerId, _: &NetworkContext, _: UntrustedRlp) -> Result<(), Error> {
-		unimplemented!()
+	fn relay_transactions(&self, peer: &PeerId, data: UntrustedRlp) -> Result<(), Error> {
+		const MAX_TRANSACTIONS: usize = 256;
+
+		let txs: Vec<_> = try!(data.iter().take(MAX_TRANSACTIONS).map(|x| x.as_val::<SignedTransaction>()).collect());
+
+		debug!(target: "les", "Received {} transactions to relay from peer {}", txs.len(), peer);
+
+		for handler in &self.handlers {
+			handler.on_transactions(*peer, &txs);
+		}
+
+		Ok(())
 	}
 }
 
@@ -464,7 +782,7 @@ impl NetworkProtocolHandler for LightProtocol {
 			packet::GET_HEADER_PROOFS => self.get_header_proofs(peer, io, rlp),
 			packet::HEADER_PROOFS => self.header_proofs(peer, io, rlp),
 
-			packet::SEND_TRANSACTIONS => self.relay_transactions(peer, io, rlp),
+			packet::SEND_TRANSACTIONS => self.relay_transactions(peer, rlp),
 
 			other => {
 				Err(Error::UnrecognizedPacket(other))
@@ -503,4 +821,86 @@ impl NetworkProtocolHandler for LightProtocol {
 			_ => warn!(target: "les", "received timeout on unknown token {}", timer),
 		}
 	}
+}
+
+// Helper for encoding the request to RLP with the given ID.
+fn encode_request(req: &Request, req_id: usize) -> Vec<u8> {
+	match *req {
+		Request::Headers(ref headers) => {
+			let mut stream = RlpStream::new_list(5);
+			stream
+				.append(&req_id)
+				.begin_list(2)
+					.append(&headers.block_num)
+					.append(&headers.block_hash)
+				.append(&headers.max)
+				.append(&headers.skip)
+				.append(&headers.reverse);
+			stream.out()
+		}
+		Request::Bodies(ref request) => {
+			let mut stream = RlpStream::new_list(request.block_hashes.len() + 1);
+			stream.append(&req_id);
+
+			for hash in &request.block_hashes {
+				stream.append(hash);
+			}
+
+			stream.out()
+		}
+		Request::Receipts(ref request) => {
+			let mut stream = RlpStream::new_list(request.block_hashes.len() + 1);
+			stream.append(&req_id);
+
+			for hash in &request.block_hashes {
+				stream.append(hash);
+			}
+
+			stream.out()
+		}
+		Request::StateProofs(ref request) => {
+			let mut stream = RlpStream::new_list(request.requests.len() + 1);
+			stream.append(&req_id);
+
+			for proof_req in &request.requests {
+				stream.begin_list(4)
+					.append(&proof_req.block)
+					.append(&proof_req.key1);
+
+				match proof_req.key2 {
+					Some(ref key2) => stream.append(key2),
+					None => stream.append_empty_data(),
+				};
+
+				stream.append(&proof_req.from_level);
+			}
+
+			stream.out()
+		}
+		Request::Codes(ref request) => {
+			let mut stream = RlpStream::new_list(request.code_requests.len() + 1);
+			stream.append(&req_id);
+
+			for code_req in &request.code_requests {
+				stream.begin_list(2)
+					.append(&code_req.block_hash)
+					.append(&code_req.account_key);
+			}
+
+			stream.out()
+		}
+		Request::HeaderProofs(ref request) => {
+			let mut stream = RlpStream::new_list(request.requests.len() + 1);
+			stream.append(&req_id);
+
+			for proof_req in &request.requests {
+				stream.begin_list(3)
+					.append(&proof_req.cht_number)
+					.append(&proof_req.block_number)
+					.append(&proof_req.from_level);
+			}
+
+			stream.out()
+		}
+	}
 }

ethcore/light/src/net/status.rs

@@ -183,8 +183,10 @@ pub struct Capabilities {
 	/// Whether this peer can serve headers
 	pub serve_headers: bool,
 	/// Earliest block number it can serve block/receipt requests for.
+	/// `None` means no requests will be servable.
 	pub serve_chain_since: Option<u64>,
 	/// Earliest block number it can serve state requests for.
+	/// `None` means no requests will be servable.
 	pub serve_state_since: Option<u64>,
 	/// Whether it can relay transactions to the eth network.
 	pub tx_relay: bool,
@@ -201,6 +203,16 @@ impl Default for Capabilities {
 	}
 }
 
+impl Capabilities {
+	/// Update the capabilities from an announcement.
+	pub fn update_from(&mut self, announcement: &Announcement) {
+		self.serve_headers = self.serve_headers || announcement.serve_headers;
+		self.serve_state_since = self.serve_state_since.or(announcement.serve_state_since);
+		self.serve_chain_since = self.serve_chain_since.or(announcement.serve_chain_since);
+		self.tx_relay = self.tx_relay || announcement.tx_relay;
+	}
+}
+
 /// Attempt to parse a handshake message into its three parts:
 ///   - chain status
 ///   - serving capabilities

ethcore/light/src/provider.rs

@@ -17,8 +17,11 @@
 //! A provider for the LES protocol. This is typically a full node, who can
 //! give as much data as necessary to its peers.
 
-use ethcore::transaction::SignedTransaction;
 use ethcore::blockchain_info::BlockChainInfo;
+use ethcore::client::{BlockChainClient, ProvingBlockChainClient};
+use ethcore::transaction::SignedTransaction;
+use ethcore::ids::BlockID;
+
 use util::{Bytes, H256};
 
 use request;
@@ -26,7 +29,8 @@ use request;
 /// Defines the operations that a provider for `LES` must fulfill.
 ///
 /// These are defined at [1], but may be subject to change.
-/// Requests which can't be fulfilled should return an empty RLP list.
+/// Requests which can't be fulfilled should return either an empty RLP list
+/// or empty vector where appropriate.
 ///
 /// [1]: https://github.com/ethcore/parity/wiki/Light-Ethereum-Subprotocol-(LES)
 pub trait Provider: Send + Sync {
@@ -34,9 +38,12 @@ pub trait Provider: Send + Sync {
 	fn chain_info(&self) -> BlockChainInfo;
 
 	/// Find the depth of a common ancestor between two blocks.
+	/// If either block is unknown or an ancestor can't be found
+	/// then return `None`.
 	fn reorg_depth(&self, a: &H256, b: &H256) -> Option<u64>;
 
-	/// Earliest state.
+	/// Earliest block where state queries are available.
+	/// If `None`, no state queries are servable.
 	fn earliest_state(&self) -> Option<u64>;
 
 	/// Provide a list of headers starting at the requested block,
@@ -57,15 +64,105 @@ pub trait Provider: Send + Sync {
 	/// Provide a set of merkle proofs, as requested. Each request is a
 	/// block hash and request parameters.
 	///
-	/// Returns a vector to RLP-encoded lists satisfying the requests.
+	/// Returns a vector of RLP-encoded lists satisfying the requests.
 	fn proofs(&self, req: request::StateProofs) -> Vec<Bytes>;
 
 	/// Provide contract code for the specified (block_hash, account_hash) pairs.
-	fn code(&self, req: request::ContractCodes) -> Vec<Bytes>;
+	/// Each item in the resulting vector is either the raw bytecode or empty.
+	fn contract_code(&self, req: request::ContractCodes) -> Vec<Bytes>;
 
 	/// Provide header proofs from the Canonical Hash Tries.
 	fn header_proofs(&self, req: request::HeaderProofs) -> Vec<Bytes>;
 
 	/// Provide pending transactions.
 	fn pending_transactions(&self) -> Vec<SignedTransaction>;
+}
+
+// Implementation of a light client data provider for a client.
+impl<T: ProvingBlockChainClient + ?Sized> Provider for T {
+	fn chain_info(&self) -> BlockChainInfo {
+		BlockChainClient::chain_info(self)
+	}
+
+	fn reorg_depth(&self, a: &H256, b: &H256) -> Option<u64> {
+		self.tree_route(a, b).map(|route| route.index as u64)
+	}
+
+	fn earliest_state(&self) -> Option<u64> {
+		Some(self.pruning_info().earliest_state)
+	}
+
+	fn block_headers(&self, req: request::Headers) -> Vec<Bytes> {
+		let best_num = self.chain_info().best_block_number;
+		let start_num = req.block_num;
+
+		match self.block_hash(BlockID::Number(req.block_num)) {
+			Some(hash) if hash == req.block_hash => {}
+			_=> {
+				trace!(target: "les_provider", "unknown/non-canonical start block in header request: {:?}", (req.block_num, req.block_hash));
+				return vec![]
+			}
+		}
+
+		(0u64..req.max as u64)
+			.map(|x: u64| x.saturating_mul(req.skip))
+			.take_while(|x| if req.reverse { x < &start_num } else { best_num - start_num < *x })
+			.map(|x| if req.reverse { start_num - x } else { start_num + x })
+			.map(|x| self.block_header(BlockID::Number(x)))
+			.take_while(|x| x.is_some())
+			.flat_map(|x| x)
+			.collect()
+	}
+
+	fn block_bodies(&self, req: request::Bodies) -> Vec<Bytes> {
+		req.block_hashes.into_iter()
+			.map(|hash| self.block_body(BlockID::Hash(hash)))
+			.map(|body| body.unwrap_or_else(|| ::rlp::EMPTY_LIST_RLP.to_vec()))
+			.collect()
+	}
+
+	fn receipts(&self, req: request::Receipts) -> Vec<Bytes> {
+		req.block_hashes.into_iter()
+			.map(|hash| self.block_receipts(&hash))
+			.map(|receipts| receipts.unwrap_or_else(|| ::rlp::EMPTY_LIST_RLP.to_vec()))
+			.collect()
+	}
+
+	fn proofs(&self, req: request::StateProofs) -> Vec<Bytes> {
+		use rlp::{RlpStream, Stream};
+
+		let mut results = Vec::with_capacity(req.requests.len());
+
+		for request in req.requests {
+			let proof = match request.key2 {
+				Some(key2) => self.prove_storage(request.key1, key2, request.from_level, BlockID::Hash(request.block)),
+				None => self.prove_account(request.key1, request.from_level, BlockID::Hash(request.block)),
+			};
+
+			let mut stream = RlpStream::new_list(proof.len());
+			for node in proof {
+				stream.append_raw(&node, 1);
+			}
+
+			results.push(stream.out());
+		}
+
+		results
+	}
+
+	fn contract_code(&self, req: request::ContractCodes) -> Vec<Bytes> {
+		req.code_requests.into_iter()
+			.map(|req| {
+				self.code_by_hash(req.account_key, BlockID::Hash(req.block_hash))
+			})
+			.collect()
+	}
+
+	fn header_proofs(&self, req: request::HeaderProofs) -> Vec<Bytes> {
+		req.requests.into_iter().map(|_| ::rlp::EMPTY_LIST_RLP.to_vec()).collect()
+	}
+
+	fn pending_transactions(&self) -> Vec<SignedTransaction> {
+		BlockChainClient::pending_transactions(self)
+	}
 }

ethcore/light/src/types/les_request.rs

@@ -16,25 +16,26 @@
 
 //! LES request types.
 
-// TODO: make IPC compatible.
-
 use util::H256;
 
 /// A request for block headers.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct Headers {
-	/// Block information for the request being made.
-	pub block: (u64, H256),
+	/// Starting block number
+	pub block_num: u64,
+	/// Starting block hash. This and number could be combined but IPC codegen is
+	/// not robust enough to support it.
+	pub block_hash: H256,
 	/// The maximum amount of headers which can be returned.
 	pub max: usize,
 	/// The amount of headers to skip between each response entry.
-	pub skip: usize,
+	pub skip: u64,
 	/// Whether the headers should proceed in falling number from the initial block.
 	pub reverse: bool,
 }
 
 /// A request for specific block bodies.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct Bodies {
 	/// Hashes which bodies are being requested for.
 	pub block_hashes: Vec<H256>
@@ -44,14 +45,14 @@ pub struct Bodies {
 ///
 /// This request is answered with a list of transaction receipts for each block
 /// requested.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct Receipts {
 	/// Block hashes to return receipts for.
 	pub block_hashes: Vec<H256>,
 }
 
 /// A request for a state proof
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct StateProof {
 	/// Block hash to query state from.
 	pub block: H256,
@@ -65,21 +66,30 @@ pub struct StateProof {
 }
 
 /// A request for state proofs.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct StateProofs {
 	/// All the proof requests.
 	pub requests: Vec<StateProof>,
 }
 
 /// A request for contract code.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
+pub struct ContractCode {
+	/// Block hash
+	pub block_hash: H256,
+	/// Account key (== sha3(address))
+	pub account_key: H256,
+}
+
+/// A request for contract code.
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct ContractCodes {
 	/// Block hash and account key (== sha3(address)) pairs to fetch code for.
-	pub code_requests: Vec<(H256, H256)>,
+	pub code_requests: Vec<ContractCode>,
 }
 
 /// A request for a header proof from the Canonical Hash Trie.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct HeaderProof {
 	/// Number of the CHT.
 	pub cht_number: u64,
@@ -90,14 +100,14 @@ pub struct HeaderProof {
 }
 
 /// A request for header proofs from the CHT.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub struct HeaderProofs {
 	/// All the proof requests.
-	pub requests: Vec<HeaderProofs>,
+	pub requests: Vec<HeaderProof>,
 }
 
 /// Kinds of requests.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Binary)]
 pub enum Kind {
 	/// Requesting headers.
 	Headers,
@@ -114,7 +124,7 @@ pub enum Kind {
 }
 
 /// Encompasses all possible types of requests in a single structure.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Binary)]
 pub enum Request {
 	/// Requesting headers.
 	Headers(Headers),
@@ -142,4 +152,16 @@ impl Request {
 			Request::HeaderProofs(_) => Kind::HeaderProofs,
 		}
 	}
+
+	/// Get the amount of requests being made.
+	pub fn amount(&self) -> usize {
+		match *self {
+			Request::Headers(ref req) => req.max,
+			Request::Bodies(ref req) => req.block_hashes.len(),
+			Request::Receipts(ref req) => req.block_hashes.len(),
+			Request::StateProofs(ref req) => req.requests.len(),
+			Request::Codes(ref req) => req.code_requests.len(),
+			Request::HeaderProofs(ref req) => req.requests.len(),
+		}
+	}
 }

ethcore/light/src/types/mod.rs

@@ -0,0 +1,20 @@
+// 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/>.
+
+//! Types used in the public (IPC) api which require custom code generation.
+
+#![allow(dead_code, unused_assignments, unused_variables)] // codegen issues
+include!(concat!(env!("OUT_DIR"), "/mod.rs.in"));

ethcore/light/src/types/mod.rs.in

@@ -0,0 +1,17 @@
+// 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/>.
+
+pub mod les_request;

ethcore/src/account_provider/mod.rs

@@ -194,6 +194,11 @@ impl AccountProvider {
 		Ok(self.address_book.write().set_meta(account, meta))
 	}
 
+	/// Removes and address from the addressbook
+	pub fn remove_address(&self, addr: Address) -> Result<(), Error> {
+		Ok(self.address_book.write().remove(addr))
+	}
+
 	/// Returns each account along with name and meta.
 	pub fn accounts_info(&self) -> Result<HashMap<Address, AccountMeta>, Error> {
 		let r: HashMap<Address, AccountMeta> = try!(self.sstore.accounts())

ethcore/src/account_provider/stores.rs

@@ -74,6 +74,12 @@ impl AddressBook {
 		}
 		self.save();
 	}
+
+	/// Removes an entry
+	pub fn remove(&mut self, a: Address) {
+		self.cache.remove(&a);
+		self.save();
+	}
 }
 
 /// Dapps user settings
@@ -244,4 +250,22 @@ mod tests {
 			}
 		]);
 	}
+
+	#[test]
+	fn should_remove_address() {
+		let temp = RandomTempPath::create_dir();
+		let path = temp.as_str().to_owned();
+		let mut b = AddressBook::new(path.clone());
+
+		b.set_name(1.into(), "One".to_owned());
+		b.set_name(2.into(), "Two".to_owned());
+		b.set_name(3.into(), "Three".to_owned());
+		b.remove(2.into());
+
+		let b = AddressBook::new(path);
+		assert_eq!(b.get(), hash_map![
+			1.into() => AccountMeta{name: "One".to_owned(), meta: "{}".to_owned(), uuid: None},
+			3.into() => AccountMeta{name: "Three".to_owned(), meta: "{}".to_owned(), uuid: None}
+		]);
+	}
 }

ethcore/src/blockchain/blockchain.rs

@@ -34,6 +34,7 @@ use blockchain::update::ExtrasUpdate;
 use blockchain::{CacheSize, ImportRoute, Config};
 use db::{self, Writable, Readable, CacheUpdatePolicy};
 use cache_manager::CacheManager;
+use engines::Engine;
 
 const LOG_BLOOMS_LEVELS: usize = 3;
 const LOG_BLOOMS_ELEMENTS_PER_INDEX: usize = 16;
@@ -198,6 +199,9 @@ pub struct BlockChain {
 	pending_block_hashes: RwLock<HashMap<BlockNumber, H256>>,
 	pending_block_details: RwLock<HashMap<H256, BlockDetails>>,
 	pending_transaction_addresses: RwLock<HashMap<H256, Option<TransactionAddress>>>,
+
+	// Used for block ordering.
+	engine: Arc<Engine>,
 }
 
 impl BlockProvider for BlockChain {
@@ -415,9 +419,8 @@ impl<'a> Iterator for AncestryIter<'a> {
 }
 
 impl BlockChain {
-	#[cfg_attr(feature="dev", allow(useless_let_if_seq))]
-	/// Create new instance of blockchain from given Genesis
-	pub fn new(config: Config, genesis: &[u8], db: Arc<Database>) -> BlockChain {
+	/// Create new instance of blockchain from given Genesis and block picking rules of Engine.
+	pub fn new(config: Config, genesis: &[u8], db: Arc<Database>, engine: Arc<Engine>) -> BlockChain {
 		// 400 is the avarage size of the key
 		let cache_man = CacheManager::new(config.pref_cache_size, config.max_cache_size, 400);
 
@@ -442,6 +445,7 @@ impl BlockChain {
 			pending_block_hashes: RwLock::new(HashMap::new()),
 			pending_block_details: RwLock::new(HashMap::new()),
 			pending_transaction_addresses: RwLock::new(HashMap::new()),
+			engine: engine,
 		};
 
 		// load best block
@@ -858,13 +862,12 @@ impl BlockChain {
 		let number = header.number();
 		let parent_hash = header.parent_hash();
 		let parent_details = self.block_details(&parent_hash).unwrap_or_else(|| panic!("Invalid parent hash: {:?}", parent_hash));
-		let total_difficulty = parent_details.total_difficulty + header.difficulty();
-		let is_new_best = total_difficulty > self.best_block_total_difficulty();
+		let is_new_best = self.engine.is_new_best_block(self.best_block_total_difficulty(), HeaderView::new(&self.best_block_header()), &parent_details, header);
 
 		BlockInfo {
 			hash: hash,
 			number: number,
-			total_difficulty: total_difficulty,
+			total_difficulty: parent_details.total_difficulty + header.difficulty(),
 			location: if is_new_best {
 				// on new best block we need to make sure that all ancestors
 				// are moved to "canon chain"
@@ -1319,11 +1322,16 @@ mod tests {
 	use views::BlockView;
 	use transaction::{Transaction, Action};
 	use log_entry::{LogEntry, LocalizedLogEntry};
+	use spec::Spec;
 
 	fn new_db(path: &str) -> Arc<Database> {
 		Arc::new(Database::open(&DatabaseConfig::with_columns(::db::NUM_COLUMNS), path).unwrap())
 	}
 
+	fn new_chain(genesis: &[u8], db: Arc<Database>) -> BlockChain {
+		BlockChain::new(Config::default(), genesis, db, Spec::new_null().engine) 
+	}
+
 	#[test]
 	fn should_cache_best_block() {
 		// given
@@ -1334,7 +1342,7 @@ mod tests {
 
 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 		assert_eq!(bc.best_block_number(), 0);
 
 		// when
@@ -1360,7 +1368,7 @@ mod tests {
 
 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 
 		assert_eq!(bc.genesis_hash(), genesis_hash.clone());
 		assert_eq!(bc.best_block_hash(), genesis_hash.clone());
@@ -1391,7 +1399,7 @@ mod tests {
 
 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 
 		let mut block_hashes = vec![genesis_hash.clone()];
 		let mut batch = db.transaction();
@@ -1427,7 +1435,7 @@ mod tests {
 
 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 
 		let mut batch =db.transaction();
 		for b in &[&b1a, &b1b, &b2a, &b2b, &b3a, &b3b, &b4a, &b4b, &b5a, &b5b] {
@@ -1489,7 +1497,7 @@ mod tests {
 
 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 
 		let mut batch = db.transaction();
 		let _ = bc.insert_block(&mut batch, &b1a, vec![]);
@@ -1577,7 +1585,7 @@ mod tests {
 
 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 
 		let mut batch = db.transaction();
 		let _ = bc.insert_block(&mut batch, &b1a, vec![]);
@@ -1639,7 +1647,7 @@ mod tests {
 
 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 
 		let mut batch = db.transaction();
 		let ir1 = bc.insert_block(&mut batch, &b1, vec![]);
@@ -1755,7 +1763,7 @@ mod tests {
 		let temp = RandomTempPath::new();
 		{
 			let db = new_db(temp.as_str());
-			let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+			let bc = new_chain(&genesis, db.clone());
 			assert_eq!(bc.best_block_hash(), genesis_hash);
 			let mut batch =db.transaction();
 			bc.insert_block(&mut batch, &first, vec![]);
@@ -1766,7 +1774,7 @@ mod tests {
 
 		{
 			let db = new_db(temp.as_str());
-			let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+			let bc = new_chain(&genesis, db.clone());
 
 			assert_eq!(bc.best_block_hash(), first_hash);
 		}
@@ -1821,7 +1829,7 @@ mod tests {
 
 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 		let mut batch =db.transaction();
 		bc.insert_block(&mut batch, &b1, vec![]);
 		db.write(batch).unwrap();
@@ -1881,7 +1889,7 @@ mod tests {
 
 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 		insert_block(&db, &bc, &b1, vec![Receipt {
 			state_root: H256::default(),
 			gas_used: 10_000.into(),
@@ -1985,7 +1993,7 @@ mod tests {
 
 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 
 		let blocks_b1 = bc.blocks_with_bloom(&bloom_b1, 0, 5);
 		let blocks_b2 = bc.blocks_with_bloom(&bloom_b2, 0, 5);
@@ -2042,7 +2050,7 @@ mod tests {
 
 		{
 			let db = new_db(temp.as_str());
-			let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+			let bc = new_chain(&genesis, db.clone());
 			let uncle = canon_chain.fork(1).generate(&mut finalizer.fork()).unwrap();
 
 			let mut batch =db.transaction();
@@ -2061,7 +2069,7 @@ mod tests {
 
 		// re-loading the blockchain should load the correct best block.
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 		assert_eq!(bc.best_block_number(), 5);
 	}
 
@@ -2078,7 +2086,7 @@ mod tests {
 
 		let temp = RandomTempPath::new();
 		let db = new_db(temp.as_str());
-		let bc = BlockChain::new(Config::default(), &genesis, db.clone());
+		let bc = new_chain(&genesis, db.clone());
 
 		let mut batch =db.transaction();
 		bc.insert_block(&mut batch, &first, vec![]);

ethcore/src/client/client.rs

@@ -54,7 +54,7 @@ use blockchain::{BlockChain, BlockProvider, TreeRoute, ImportRoute};
 use client::{
 	BlockId, TransactionId, UncleId, TraceId, ClientConfig, BlockChainClient,
 	MiningBlockChainClient, TraceFilter, CallAnalytics, BlockImportError, Mode,
-	ChainNotify,
+	ChainNotify, PruningInfo, ProvingBlockChainClient,
 };
 use client::Error as ClientError;
 use env_info::EnvInfo;
@@ -173,7 +173,7 @@ impl Client {
 		let gb = spec.genesis_block();
 
 		let db = Arc::new(try!(Database::open(&db_config, &path.to_str().expect("DB path could not be converted to string.")).map_err(ClientError::Database)));
-		let chain = Arc::new(BlockChain::new(config.blockchain.clone(), &gb, db.clone()));
+		let chain = Arc::new(BlockChain::new(config.blockchain.clone(), &gb, db.clone(), spec.engine.clone()));
 		let tracedb = RwLock::new(TraceDB::new(config.tracing.clone(), db.clone(), chain.clone()));
 
 		let trie_spec = match config.fat_db {
@@ -854,7 +854,7 @@ impl snapshot::DatabaseRestore for Client {
 
 		let cache_size = state_db.cache_size();
 		*state_db = StateDB::new(journaldb::new(db.clone(), self.pruning, ::db::COL_STATE), cache_size);
-		*chain = Arc::new(BlockChain::new(self.config.blockchain.clone(), &[], db.clone()));
+		*chain = Arc::new(BlockChain::new(self.config.blockchain.clone(), &[], db.clone(), self.engine.clone()));
 		*tracedb = TraceDB::new(self.config.tracing.clone(), db.clone(), chain.clone());
 		Ok(())
 	}
@@ -1339,7 +1339,7 @@ impl BlockChainClient for Client {
 		self.miner.pending_transactions(self.chain.read().best_block_number())
 	}
 
-	fn signing_network_id(&self) -> Option<u8> {
+	fn signing_network_id(&self) -> Option<u64> {
 		self.engine.signing_network_id(&self.latest_env_info())
 	}
 
@@ -1353,6 +1353,13 @@ impl BlockChainClient for Client {
 		self.uncle(id)
 			.map(|header| self.engine.extra_info(&decode(&header)))
 	}
+
+	fn pruning_info(&self) -> PruningInfo {
+		PruningInfo {
+			earliest_chain: self.chain.read().first_block_number().unwrap_or(1),
+			earliest_state: self.state_db.lock().journal_db().earliest_era().unwrap_or(0),
+		}
+	}
 }
 
 impl MiningBlockChainClient for Client {
@@ -1437,32 +1444,60 @@ impl MayPanic for Client {
 	}
 }
 
+impl ProvingBlockChainClient for Client {
+	fn prove_storage(&self, key1: H256, key2: H256, from_level: u32, id: BlockID) -> Vec<Bytes> {
+		self.state_at(id)
+			.and_then(move |state| state.prove_storage(key1, key2, from_level).ok())
+			.unwrap_or_else(Vec::new)
+	}
 
-#[test]
-fn should_not_cache_details_before_commit() {
-	use tests::helpers::*;
-	use std::thread;
-	use std::time::Duration;
-	use std::sync::atomic::{AtomicBool, Ordering};
+	fn prove_account(&self, key1: H256, from_level: u32, id: BlockID) -> Vec<Bytes> {
+		self.state_at(id)
+			.and_then(move |state| state.prove_account(key1, from_level).ok())
+			.unwrap_or_else(Vec::new)
+	}
 
-	let client = generate_dummy_client(0);
-	let genesis = client.chain_info().best_block_hash;
-	let (new_hash, new_block) = get_good_dummy_block_hash();
-
-	let go = {
-		// Separate thread uncommited transaction
-		let go = Arc::new(AtomicBool::new(false));
-		let go_thread = go.clone();
-		let another_client = client.reference().clone();
-		thread::spawn(move || {
-			let mut batch = DBTransaction::new(&*another_client.chain.read().db().clone());
-			another_client.chain.read().insert_block(&mut batch, &new_block, Vec::new());
-			go_thread.store(true, Ordering::SeqCst);
-		});
-		go
-	};
-
-	while !go.load(Ordering::SeqCst) { thread::park_timeout(Duration::from_millis(5)); }
-
-	assert!(client.tree_route(&genesis, &new_hash).is_none());
+	fn code_by_hash(&self, account_key: H256, id: BlockID) -> Bytes {
+		self.state_at(id)
+			.and_then(move |state| state.code_by_address_hash(account_key).ok())
+			.and_then(|x| x)
+			.unwrap_or_else(Vec::new)
+	}
 }
+
+#[cfg(test)]
+mod tests {
+
+	#[test]
+	fn should_not_cache_details_before_commit() {
+		use client::BlockChainClient;
+		use tests::helpers::*;
+
+		use std::thread;
+		use std::time::Duration;
+		use std::sync::Arc;
+		use std::sync::atomic::{AtomicBool, Ordering};
+		use util::kvdb::DBTransaction;
+
+		let client = generate_dummy_client(0);
+		let genesis = client.chain_info().best_block_hash;
+		let (new_hash, new_block) = get_good_dummy_block_hash();
+
+		let go = {
+			// Separate thread uncommited transaction
+			let go = Arc::new(AtomicBool::new(false));
+			let go_thread = go.clone();
+			let another_client = client.reference().clone();
+			thread::spawn(move || {
+				let mut batch = DBTransaction::new(&*another_client.chain.read().db().clone());
+				another_client.chain.read().insert_block(&mut batch, &new_block, Vec::new());
+				go_thread.store(true, Ordering::SeqCst);
+			});
+			go
+		};
+
+		while !go.load(Ordering::SeqCst) { thread::park_timeout(Duration::from_millis(5)); }
+
+		assert!(client.tree_route(&genesis, &new_hash).is_none());
+	}
+}

ethcore/src/client/mod.rs

@@ -29,18 +29,21 @@ mod fetch;
 pub use self::client::*;
 pub use self::config::{Mode, ClientConfig, UpdatePolicy, UpdateFilter, DatabaseCompactionProfile, BlockChainConfig, VMType};
 pub use self::error::Error;
-pub use types::ids::*;
 pub use self::test_client::{TestBlockChainClient, EachBlockWith};
+pub use self::chain_notify::ChainNotify;
+pub use self::traits::{BlockChainClient, MiningBlockChainClient, ProvingBlockChainClient};
+
+pub use types::ids::*;
 pub use types::trace_filter::Filter as TraceFilter;
+pub use types::pruning_info::PruningInfo;
+pub use types::call_analytics::CallAnalytics;
+
 pub use executive::{Executed, Executive, TransactOptions};
 pub use env_info::{LastHashes, EnvInfo};
-pub use self::chain_notify::ChainNotify;
 
-pub use types::call_analytics::CallAnalytics;
 pub use block_import_error::BlockImportError;
 pub use transaction_import::TransactionImportResult;
 pub use transaction_import::TransactionImportError;
-pub use self::traits::{BlockChainClient, MiningBlockChainClient};
 pub use verification::VerifierType;
 
 /// IPC interfaces

ethcore/src/client/test_client.rs

@@ -38,6 +38,7 @@ use evm::{Factory as EvmFactory, VMType, Schedule};
 use miner::{Miner, MinerService, TransactionImportResult};
 use spec::Spec;
 use types::mode::Mode;
+use types::pruning_info::PruningInfo;
 use views::BlockView;
 
 use verification::queue::QueueInfo;
@@ -662,9 +663,16 @@ impl BlockChainClient for TestBlockChainClient {
 		self.miner.pending_transactions(self.chain_info().best_block_number)
 	}
 
-	fn signing_network_id(&self) -> Option<u8> { None }
+	fn signing_network_id(&self) -> Option<u64> { None }
 
 	fn mode(&self) -> Mode { Mode::Active }
 
 	fn set_mode(&self, _: Mode) { unimplemented!(); }
+
+	fn pruning_info(&self) -> PruningInfo {
+		PruningInfo {
+			earliest_chain: 1,
+			earliest_state: 1,
+		}
+	}
 }

ethcore/src/client/traits.rs

@@ -39,6 +39,7 @@ use types::call_analytics::CallAnalytics;
 use types::blockchain_info::BlockChainInfo;
 use types::block_status::BlockStatus;
 use types::mode::Mode;
+use types::pruning_info::PruningInfo;
 
 #[ipc(client_ident="RemoteClient")]
 /// Blockchain database client. Owns and manages a blockchain and a block queue.
@@ -237,7 +238,7 @@ pub trait BlockChainClient : Sync + Send {
 	}
 
 	/// Get the preferred network ID to sign on
-	fn signing_network_id(&self) -> Option<u8>;
+	fn signing_network_id(&self) -> Option<u64>;
 
 	/// Get the mode.
 	fn mode(&self) -> Mode;
@@ -248,12 +249,17 @@ pub trait BlockChainClient : Sync + Send {
 	/// Returns engine-related extra info for `BlockId`.
 	fn block_extra_info(&self, id: BlockId) -> Option<BTreeMap<String, String>>;
 
-	/// Returns engine-related extra info for `UncleId`.
+	/// Returns engine-related extra info for `UncleID`.
 	fn uncle_extra_info(&self, id: UncleId) -> Option<BTreeMap<String, String>>;
+
+	/// Returns information about pruning/data availability.
+	fn pruning_info(&self) -> PruningInfo;
 }
 
+impl IpcConfig for BlockChainClient { }
+
 /// Extended client interface used for mining
-pub trait MiningBlockChainClient : BlockChainClient {
+pub trait MiningBlockChainClient: BlockChainClient {
 	/// Returns OpenBlock prepared for closing.
 	fn prepare_open_block(&self,
 		author: Address,
@@ -271,4 +277,23 @@ pub trait MiningBlockChainClient : BlockChainClient {
 	fn latest_schedule(&self) -> Schedule;
 }
 
-impl IpcConfig for BlockChainClient { }
+/// Extended client interface for providing proofs of the state.
+pub trait ProvingBlockChainClient: BlockChainClient {
+	/// Prove account storage at a specific block id.
+	///
+	/// Both provided keys assume a secure trie.
+	/// Returns a vector of raw trie nodes (in order from the root) proving the storage query.
+	/// Nodes after `from_level` may be omitted.
+	/// An empty vector indicates unservable query.
+	fn prove_storage(&self, key1: H256, key2: H256, from_level: u32, id: BlockID) -> Vec<Bytes>;
+
+	/// Prove account existence at a specific block id.
+	/// The key is the keccak hash of the account's address.
+	/// Returns a vector of raw trie nodes (in order from the root) proving the query.
+	/// Nodes after `from_level` may be omitted.
+	/// An empty vector indicates unservable query.	
+	fn prove_account(&self, key1: H256, from_level: u32, id: BlockID) -> Vec<Bytes>;
+
+	/// Get code by address hash.
+	fn code_by_hash(&self, account_key: H256, id: BlockID) -> Bytes;
+}

ethcore/src/engines/authority_round.rs

@@ -21,7 +21,7 @@ use std::sync::Weak;
 use std::time::{UNIX_EPOCH, Duration};
 use util::*;
 use ethkey::{verify_address, Signature};
-use rlp::{UntrustedRlp, View, encode};
+use rlp::{Rlp, UntrustedRlp, View, encode};
 use account_provider::AccountProvider;
 use block::*;
 use spec::CommonParams;
@@ -35,6 +35,8 @@ use service::ClientIoMessage;
 use transaction::SignedTransaction;
 use env_info::EnvInfo;
 use builtin::Builtin;
+use blockchain::extras::BlockDetails;
+use views::HeaderView;
 
 /// `AuthorityRound` params.
 #[derive(Debug, PartialEq)]
@@ -272,7 +274,6 @@ impl Engine for AuthorityRound {
 	}
 
 	fn verify_block_family(&self, header: &Header, parent: &Header, _block: Option<&[u8]>) -> Result<(), Error> {
-		// Don't calculate difficulty for genesis blocks.
 		if header.number() == 0 {
 			return Err(From::from(BlockError::RidiculousNumber(OutOfBounds { min: Some(1), max: None, found: header.number() })));
 		}
@@ -284,10 +285,6 @@ impl Engine for AuthorityRound {
 			try!(Err(BlockError::DoubleVote(header.author().clone())));
 		}
 
-		// Check difficulty is correct given the two timestamps.
-		if header.difficulty() != parent.difficulty() {
-			return Err(From::from(BlockError::InvalidDifficulty(Mismatch { expected: *parent.difficulty(), found: *header.difficulty() })))
-		}
 		let gas_limit_divisor = self.our_params.gas_limit_bound_divisor;
 		let min_gas = parent.gas_limit().clone() - parent.gas_limit().clone() / gas_limit_divisor;
 		let max_gas = parent.gas_limit().clone() + parent.gas_limit().clone() / gas_limit_divisor;
@@ -310,6 +307,19 @@ impl Engine for AuthorityRound {
 		let mut guard = self.message_channel.lock();
 		*guard = Some(message_channel);
 	}
+
+	fn is_new_best_block(&self, _best_total_difficulty: U256, best_header: HeaderView, _parent_details: &BlockDetails, new_header: &HeaderView) -> bool {
+		let new_number = new_header.number();
+		let best_number = best_header.number();
+		if new_number != best_number {
+			new_number > best_number
+		} else {
+			// Take the oldest step at given height.
+			let new_step: usize = Rlp::new(&new_header.seal()[0]).as_val();
+			let best_step: usize = Rlp::new(&best_header.seal()[0]).as_val();
+			new_step < best_step
+		}
+	}
 }
 
 #[cfg(test)]

ethcore/src/engines/mod.rs

@@ -38,6 +38,9 @@ use io::IoChannel;
 use service::ClientIoMessage;
 use header::Header;
 use transaction::SignedTransaction;
+use ethereum::ethash;
+use blockchain::extras::BlockDetails;
+use views::HeaderView;
 
 /// A consensus mechanism for the chain. Generally either proof-of-work or proof-of-stake-based.
 /// Provides hooks into each of the major parts of block import.
@@ -113,7 +116,7 @@ pub trait Engine : Sync + Send {
 	fn verify_transaction(&self, _t: &SignedTransaction, _header: &Header) -> Result<(), Error> { Ok(()) }
 
 	/// The network ID that transactions should be signed with.
-	fn signing_network_id(&self, _env_info: &EnvInfo) -> Option<u8> { None }
+	fn signing_network_id(&self, _env_info: &EnvInfo) -> Option<u64> { None }
 
 	/// Verify the seal of a block. This is an auxilliary method that actually just calls other `verify_` methods
 	/// to get the job done. By default it must pass `verify_basic` and `verify_block_unordered`. If more or fewer
@@ -146,5 +149,9 @@ pub trait Engine : Sync + Send {
 
 	/// Add a channel for communication with Client which can be used for sealing.
 	fn register_message_channel(&self, _message_channel: IoChannel<ClientIoMessage>) {}
-	// TODO: sealing stuff - though might want to leave this for later.
+
+	/// Check if new block should be chosen as the one  in chain.
+	fn is_new_best_block(&self, best_total_difficulty: U256, _best_header: HeaderView, parent_details: &BlockDetails, new_header: &HeaderView) -> bool {
+		ethash::is_new_best_block(best_total_difficulty, parent_details, new_header)
+	}
 }

ethcore/src/engines/null_engine.rs

@@ -38,6 +38,12 @@ impl NullEngine {
 	}
 }
 
+impl Default for NullEngine {
+	fn default() -> Self {
+		Self::new(Default::default(), Default::default())
+	}
+}
+
 impl Engine for NullEngine {
 	fn name(&self) -> &str {
 		"NullEngine"

ethcore/src/ethereum/ethash.rs

@@ -21,6 +21,7 @@ use builtin::Builtin;
 use env_info::EnvInfo;
 use error::{BlockError, TransactionError, Error};
 use header::Header;
+use views::HeaderView;
 use state::CleanupMode;
 use spec::CommonParams;
 use transaction::SignedTransaction;
@@ -28,6 +29,7 @@ use engines::Engine;
 use evm::Schedule;
 use ethjson;
 use rlp::{self, UntrustedRlp, View};
+use blockchain::extras::BlockDetails;
 
 /// Ethash params.
 #[derive(Debug, PartialEq)]
@@ -163,9 +165,9 @@ impl Engine for Ethash {
 		}
 	}
 
-	fn signing_network_id(&self, env_info: &EnvInfo) -> Option<u8> {
-		if env_info.number >= self.ethash_params.eip155_transition && self.params().network_id < 127 {
-			Some(self.params().network_id as u8)
+	fn signing_network_id(&self, env_info: &EnvInfo) -> Option<u64> {
+		if env_info.number >= self.ethash_params.eip155_transition {
+			Some(self.params().network_id)
 		} else {
 			None
 		}
@@ -314,7 +316,7 @@ impl Engine for Ethash {
 		}
 
 		if let Some(n) = t.network_id() {
-			if header.number() < self.ethash_params.eip155_transition || n as usize != self.params().network_id {
+			if header.number() < self.ethash_params.eip155_transition || n != self.params().network_id {
 				return Err(TransactionError::InvalidNetworkId.into())
 			}
 		}
@@ -325,6 +327,15 @@ impl Engine for Ethash {
 	fn verify_transaction(&self, t: &SignedTransaction, _header: &Header) -> Result<(), Error> {
 		t.sender().map(|_|()) // Perform EC recovery and cache sender
 	}
+
+	fn is_new_best_block(&self, best_total_difficulty: U256, _best_header: HeaderView, parent_details: &BlockDetails, new_header: &HeaderView) -> bool {
+		is_new_best_block(best_total_difficulty, parent_details, new_header)
+	}
+}
+
+/// Check if a new block should replace the best blockchain block.
+pub fn is_new_best_block(best_total_difficulty: U256, parent_details: &BlockDetails, new_header: &HeaderView) -> bool {
+	parent_details.total_difficulty + new_header.difficulty() > best_total_difficulty
 }
 
 #[cfg_attr(feature="dev", allow(wrong_self_convention))]

ethcore/src/snapshot/service.rs

@@ -81,6 +81,7 @@ struct Restoration {
 struct RestorationParams<'a> {
 	manifest: ManifestData, // manifest to base restoration on.
 	pruning: Algorithm, // pruning algorithm for the database.
+	engine: Arc<Engine>, // consensus engine of the chain.
 	db_path: PathBuf, // database path
 	db_config: &'a DatabaseConfig, // configuration for the database.
 	writer: Option<LooseWriter>, // writer for recovered snapshot.
@@ -99,7 +100,7 @@ impl Restoration {
 		let raw_db = Arc::new(try!(Database::open(params.db_config, &*params.db_path.to_string_lossy())
 			.map_err(UtilError::SimpleString)));
 
-		let chain = BlockChain::new(Default::default(), params.genesis, raw_db.clone());
+		let chain = BlockChain::new(Default::default(), params.genesis, raw_db.clone(), params.engine);
 		let blocks = try!(BlockRebuilder::new(chain, raw_db.clone(), &manifest));
 
 		let root = manifest.state_root.clone();
@@ -420,6 +421,7 @@ impl Service {
 		let params = RestorationParams {
 			manifest: manifest,
 			pruning: self.pruning,
+			engine: self.engine.clone(),
 			db_path: self.restoration_db(),
 			db_config: &self.db_config,
 			writer: writer,

ethcore/src/snapshot/tests/blocks.rs

@@ -37,13 +37,14 @@ fn chunk_and_restore(amount: u64) {
 	let genesis = canon_chain.generate(&mut finalizer).unwrap();
 	let db_cfg = DatabaseConfig::with_columns(::db::NUM_COLUMNS);
 
+	let engine = Arc::new(::engines::NullEngine::default());
 	let orig_path = RandomTempPath::create_dir();
 	let new_path = RandomTempPath::create_dir();
 	let mut snapshot_path = new_path.as_path().to_owned();
 	snapshot_path.push("SNAP");
 
 	let old_db = Arc::new(Database::open(&db_cfg, orig_path.as_str()).unwrap());
-	let bc = BlockChain::new(Default::default(), &genesis, old_db.clone());
+	let bc = BlockChain::new(Default::default(), &genesis, old_db.clone(), engine.clone());
 
 	// build the blockchain.
 	let mut batch = old_db.transaction();
@@ -73,21 +74,20 @@ fn chunk_and_restore(amount: u64) {
 
 	// restore it.
 	let new_db = Arc::new(Database::open(&db_cfg, new_path.as_str()).unwrap());
-	let new_chain = BlockChain::new(Default::default(), &genesis, new_db.clone());
+	let new_chain = BlockChain::new(Default::default(), &genesis, new_db.clone(), engine.clone());
 	let mut rebuilder = BlockRebuilder::new(new_chain, new_db.clone(), &manifest).unwrap();
 	let reader = PackedReader::new(&snapshot_path).unwrap().unwrap();
-	let engine = ::engines::NullEngine::new(Default::default(), Default::default());
 	let flag = AtomicBool::new(true);
 	for chunk_hash in &reader.manifest().block_hashes {
 		let compressed = reader.chunk(*chunk_hash).unwrap();
 		let chunk = snappy::decompress(&compressed).unwrap();
-		rebuilder.feed(&chunk, &engine, &flag).unwrap();
+		rebuilder.feed(&chunk, engine.as_ref(), &flag).unwrap();
 	}
 
 	rebuilder.finalize(HashMap::new()).unwrap();
 
 	// and test it.
-	let new_chain = BlockChain::new(Default::default(), &genesis, new_db);
+	let new_chain = BlockChain::new(Default::default(), &genesis, new_db, engine);
 	assert_eq!(new_chain.best_block_hash(), best_hash);
 }
 
@@ -121,8 +121,8 @@ fn checks_flag() {
 
 	let db_cfg = DatabaseConfig::with_columns(::db::NUM_COLUMNS);
 	let db = Arc::new(Database::open(&db_cfg, path.as_str()).unwrap());
-	let chain = BlockChain::new(Default::default(), &genesis, db.clone());
-	let engine = ::engines::NullEngine::new(Default::default(), Default::default());
+	let engine = Arc::new(::engines::NullEngine::default());
+	let chain = BlockChain::new(Default::default(), &genesis, db.clone(), engine.clone());
 
 	let manifest = ::snapshot::ManifestData {
 		state_hashes: Vec::new(),
@@ -134,8 +134,8 @@ fn checks_flag() {
 
 	let mut rebuilder = BlockRebuilder::new(chain, db.clone(), &manifest).unwrap();
 
-	match rebuilder.feed(&chunk, &engine, &AtomicBool::new(false)) {
+	match rebuilder.feed(&chunk, engine.as_ref(), &AtomicBool::new(false)) {
 		Err(Error::Snapshot(SnapshotError::RestorationAborted)) => {}
 		_ => panic!("Wrong result on abort flag set")
 	}
-}
+}

ethcore/src/spec/spec.rs

@@ -30,15 +30,14 @@ use ethjson;
 use rlp::{Rlp, RlpStream, View, Stream};
 
 /// Parameters common to all engines.
-#[derive(Debug, PartialEq, Clone)]
-#[cfg_attr(test, derive(Default))]
+#[derive(Debug, PartialEq, Clone, Default)]
 pub struct CommonParams {
 	/// Account start nonce.
 	pub account_start_nonce: U256,
 	/// Maximum size of extra data.
 	pub maximum_extra_data_size: usize,
 	/// Network id.
-	pub network_id: usize,
+	pub network_id: u64,
 	/// Main subprotocol name.
 	pub subprotocol_name: String,
 	/// Minimum gas limit.
@@ -164,7 +163,7 @@ impl Spec {
 	pub fn nodes(&self) -> &[String] { &self.nodes }
 
 	/// Get the configured Network ID.
-	pub fn network_id(&self) -> usize { self.params.network_id }
+	pub fn network_id(&self) -> u64 { self.params.network_id }
 
 	/// Get the configured subprotocol name.
 	pub fn subprotocol_name(&self) -> String { self.params.subprotocol_name.clone() }

ethcore/src/state/account.rs

@@ -436,6 +436,27 @@ impl Account {
 	}
 }
 
+// light client storage proof.
+impl Account {
+	/// Prove a storage key's existence or nonexistence in the account's storage
+	/// trie.
+	/// `storage_key` is the hash of the desired storage key, meaning
+	/// this will only work correctly under a secure trie.
+	/// Returns a merkle proof of the storage trie node with all nodes before `from_level`
+	/// omitted.
+	pub fn prove_storage(&self, db: &HashDB, storage_key: H256, from_level: u32) -> Result<Vec<Bytes>, Box<TrieError>> {
+		use util::trie::{Trie, TrieDB};
+		use util::trie::recorder::{Recorder, BasicRecorder as TrieRecorder};
+
+		let mut recorder = TrieRecorder::with_depth(from_level);
+
+		let trie = try!(TrieDB::new(db, &self.storage_root));
+		let _ = try!(trie.get_recorded(&storage_key, &mut recorder));
+
+		Ok(recorder.drain().into_iter().map(|r| r.data).collect())
+	}
+}
+
 impl fmt::Debug for Account {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		write!(f, "{:?}", PodAccount::from_account(self))

ethcore/src/state/mod.rs

@@ -16,7 +16,7 @@
 
 use std::cell::{RefCell, RefMut};
 use std::collections::hash_map::Entry;
-use util::*;
+
 use receipt::Receipt;
 use engines::Engine;
 use env_info::EnvInfo;
@@ -30,6 +30,9 @@ use types::state_diff::StateDiff;
 use transaction::SignedTransaction;
 use state_db::StateDB;
 
+use util::*;
+use util::trie::recorder::{Recorder, BasicRecorder as TrieRecorder};
+
 mod account;
 mod substate;
 
@@ -758,6 +761,53 @@ impl State {
 	}
 }
 
+// LES state proof implementations.
+impl State {
+	/// Prove an account's existence or nonexistence in the state trie.
+	/// Returns a merkle proof of the account's trie node with all nodes before `from_level`
+	/// omitted or an encountered trie error.
+	/// Requires a secure trie to be used for accurate results.
+	/// `account_key` == sha3(address)
+	pub fn prove_account(&self, account_key: H256, from_level: u32) -> Result<Vec<Bytes>, Box<TrieError>> {
+		let mut recorder = TrieRecorder::with_depth(from_level);
+		let trie = try!(TrieDB::new(self.db.as_hashdb(), &self.root));
+		let _  = try!(trie.get_recorded(&account_key, &mut recorder));
+
+		Ok(recorder.drain().into_iter().map(|r| r.data).collect())
+	}
+
+	/// Prove an account's storage key's existence or nonexistence in the state.
+	/// Returns a merkle proof of the account's storage trie with all nodes before
+	/// `from_level` omitted. Requires a secure trie to be used for correctness.
+	/// `account_key` == sha3(address)
+	/// `storage_key` == sha3(key)
+	pub fn prove_storage(&self, account_key: H256, storage_key: H256, from_level: u32) -> Result<Vec<Bytes>, Box<TrieError>> {
+		// TODO: probably could look into cache somehow but it's keyed by
+		// address, not sha3(address).
+		let trie = try!(TrieDB::new(self.db.as_hashdb(), &self.root));
+		let acc = match try!(trie.get(&account_key)) {
+			Some(rlp) => Account::from_rlp(&rlp),
+			None => return Ok(Vec::new()),
+		};
+
+		let account_db = self.factories.accountdb.readonly(self.db.as_hashdb(), account_key);
+		acc.prove_storage(account_db.as_hashdb(), storage_key, from_level)
+	}
+
+	/// Get code by address hash.
+	/// Only works when backed by a secure trie.
+	pub fn code_by_address_hash(&self, account_key: H256) -> Result<Option<Bytes>, Box<TrieError>> {
+		let trie = try!(TrieDB::new(self.db.as_hashdb(), &self.root));
+		let mut acc = match try!(trie.get(&account_key)) {
+			Some(rlp) => Account::from_rlp(&rlp),
+			None => return Ok(None),
+		};
+
+		let account_db = self.factories.accountdb.readonly(self.db.as_hashdb(), account_key);
+		Ok(acc.cache_code(account_db.as_hashdb()).map(|c| (&*c).clone()))
+	}
+}
+
 impl fmt::Debug for State {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		write!(f, "{:?}", self.cache.borrow())

ethcore/src/tests/helpers.rs

@@ -286,7 +286,7 @@ fn new_db(path: &str) -> Arc<Database> {
 pub fn generate_dummy_blockchain(block_number: u32) -> GuardedTempResult<BlockChain> {
 	let temp = RandomTempPath::new();
 	let db = new_db(temp.as_str());
-	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone());
+	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone(), Spec::new_null().engine);
 
 	let mut batch = db.transaction();
 	for block_order in 1..block_number {
@@ -304,7 +304,7 @@ pub fn generate_dummy_blockchain(block_number: u32) -> GuardedTempResult<BlockCh
 pub fn generate_dummy_blockchain_with_extra(block_number: u32) -> GuardedTempResult<BlockChain> {
 	let temp = RandomTempPath::new();
 	let db = new_db(temp.as_str());
-	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone());
+	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone(), Spec::new_null().engine);
 
 
 	let mut batch = db.transaction();
@@ -323,7 +323,7 @@ pub fn generate_dummy_blockchain_with_extra(block_number: u32) -> GuardedTempRes
 pub fn generate_dummy_empty_blockchain() -> GuardedTempResult<BlockChain> {
 	let temp = RandomTempPath::new();
 	let db = new_db(temp.as_str());
-	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone());
+	let bc = BlockChain::new(BlockChainConfig::default(), &create_unverifiable_block(0, H256::zero()), db.clone(), Spec::new_null().engine);
 
 	GuardedTempResult::<BlockChain> {
 		_temp: temp,

ethcore/src/types/mod.rs.in

@@ -34,3 +34,4 @@ pub mod block_import_error;
 pub mod restoration_status;
 pub mod snapshot_manifest;
 pub mod mode;
+pub mod pruning_info;

ethcore/src/types/pruning_info.rs

@@ -0,0 +1,30 @@
+// 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/>.
+
+//! Information about portions of the state and chain which the client may serve.
+//!
+//! Currently assumes that a client will store everything past a certain point
+//! or everything. Will be extended in the future to support a definition
+//! of which portions of the ancient chain and current state trie are stored as well.
+
+/// Client pruning info. See module-level docs for more details.
+#[derive(Debug, Clone, Binary)]
+pub struct PruningInfo {
+	/// The first block which everything can be served after.
+	pub earliest_chain: u64,
+	/// The first block where state requests may be served.
+	pub earliest_state: u64,
+}

ethcore/src/types/transaction.rs

@@ -72,7 +72,7 @@ pub struct Transaction {
 
 impl Transaction {
 	/// Append object with a without signature into RLP stream
-	pub fn rlp_append_unsigned_transaction(&self, s: &mut RlpStream, network_id: Option<u8>) {
+	pub fn rlp_append_unsigned_transaction(&self, s: &mut RlpStream, network_id: Option<u64>) {
 		s.begin_list(if network_id.is_none() { 6 } else { 9 });
 		s.append(&self.nonce);
 		s.append(&self.gas_price);
@@ -140,26 +140,26 @@ impl From<ethjson::transaction::Transaction> for SignedTransaction {
 
 impl Transaction {
 	/// The message hash of the transaction.
-	pub fn hash(&self, network_id: Option<u8>) -> H256 {
+	pub fn hash(&self, network_id: Option<u64>) -> H256 {
 		let mut stream = RlpStream::new();
 		self.rlp_append_unsigned_transaction(&mut stream, network_id);
 		stream.out().sha3()
 	}
 
 	/// Signs the transaction as coming from `sender`.
-	pub fn sign(self, secret: &Secret, network_id: Option<u8>) -> SignedTransaction {
+	pub fn sign(self, secret: &Secret, network_id: Option<u64>) -> SignedTransaction {
 		let sig = ::ethkey::sign(secret, &self.hash(network_id))
 			.expect("data is valid and context has signing capabilities; qed");
 		self.with_signature(sig, network_id)
 	}
 
 	/// Signs the transaction with signature.
-	pub fn with_signature(self, sig: Signature, network_id: Option<u8>) -> SignedTransaction {
+	pub fn with_signature(self, sig: Signature, network_id: Option<u64>) -> SignedTransaction {
 		SignedTransaction {
 			unsigned: self,
 			r: sig.r().into(),
 			s: sig.s().into(),
-			v: sig.v() + if let Some(n) = network_id { 35 + n * 2 } else { 27 },
+			v: sig.v() as u64 + if let Some(n) = network_id { 35 + n * 2 } else { 27 },
 			hash: Cell::new(None),
 			sender: Cell::new(None),
 		}
@@ -211,7 +211,7 @@ pub struct SignedTransaction {
 	unsigned: Transaction,
 	/// The V field of the signature; the LS bit described which half of the curve our point falls
 	/// in. The MS bits describe which network this transaction is for. If 27/28, its for all networks.
-	v: u8,
+	v: u64,
 	/// The R field of the signature; helps describe the point on the curve.
 	r: U256,
 	/// The S field of the signature; helps describe the point on the curve.
@@ -302,10 +302,13 @@ impl SignedTransaction {
 	}
 
 	/// 0 if `v` would have been 27 under "Electrum" notation, 1 if 28 or 4 if invalid.
-	pub fn standard_v(&self) -> u8 { match self.v { v if v == 27 || v == 28 || v > 36 => (v - 1) % 2, _ => 4 } }
+	pub fn standard_v(&self) -> u8 { match self.v { v if v == 27 || v == 28 || v > 36 => ((v - 1) % 2) as u8, _ => 4 } }
+
+	/// The `v` value that appears in the RLP.
+	pub fn original_v(&self) -> u64 { self.v }
 
 	/// The network ID, or `None` if this is a global transaction.
-	pub fn network_id(&self) -> Option<u8> {
+	pub fn network_id(&self) -> Option<u64> {
 		match self.v {
 			v if v > 36 => Some((v - 35) / 2),
 			_ => None,

ethcore/src/verification/queue/mod.rs

@@ -17,7 +17,7 @@
 //! A queue of blocks. Sits between network or other I/O and the `BlockChain`.
 //! Sorts them ready for blockchain insertion.
 
-use std::thread::{JoinHandle, self};
+use std::thread::{self, JoinHandle};
 use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering as AtomicOrdering};
 use std::sync::{Condvar as SCondvar, Mutex as SMutex};
 use util::*;
@@ -53,6 +53,8 @@ pub struct Config {
 	/// Maximum heap memory to use.
 	/// When the limit is reached, is_full returns true.
 	pub max_mem_use: usize,
+	/// Settings for the number of verifiers and adaptation strategy.
+	pub verifier_settings: VerifierSettings,
 }
 
 impl Default for Config {
@@ -60,39 +62,35 @@ impl Default for Config {
 		Config {
 			max_queue_size: 30000,
 			max_mem_use: 50 * 1024 * 1024,
+			verifier_settings: VerifierSettings::default(),
 		}
 	}
 }
 
-struct VerifierHandle {
-	deleting: Arc<AtomicBool>,
-	sleep: Arc<AtomicBool>,
-	thread: JoinHandle<()>,
+/// Verifier settings.
+#[derive(Debug, PartialEq, Clone)]
+pub struct VerifierSettings {
+	/// Whether to scale amount of verifiers according to load.
+	// Todo: replace w/ strategy enum?
+	pub scale_verifiers: bool,
+	/// Beginning amount of verifiers.
+	pub num_verifiers: usize,
 }
 
-impl VerifierHandle {
-	// signal to the verifier thread that it should sleep.
-	fn sleep(&self) {
-		self.sleep.store(true, AtomicOrdering::SeqCst);
+impl Default for VerifierSettings {
+	fn default() -> Self {
+		VerifierSettings {
+			scale_verifiers: false,
+			num_verifiers: MAX_VERIFIERS,
+		}
 	}
+}
 
-	// signal to the verifier thread that it should wake up.
-	fn wake_up(&self) {
-		self.sleep.store(false, AtomicOrdering::SeqCst);
-		self.thread.thread().unpark();
-	}
-
-	// signal to the verifier thread that it should conclude its
-	// operations.
-	fn conclude(&self) {
-		self.wake_up();
-		self.deleting.store(true, AtomicOrdering::Release);
-	}
-
-	// join the verifier thread.
-	fn join(self) {
-		self.thread.join().expect("Verifier thread panicked");
-	}
+// pool states
+enum State {
+	// all threads with id < inner value are to work.
+	Work(usize),
+	Exit,
 }
 
 /// An item which is in the process of being verified.
@@ -131,7 +129,6 @@ pub struct VerificationQueue<K: Kind> {
 	engine: Arc<Engine>,
 	more_to_verify: Arc<SCondvar>,
 	verification: Arc<Verification<K>>,
-	verifiers: Mutex<(Vec<VerifierHandle>, usize)>,
 	deleting: Arc<AtomicBool>,
 	ready_signal: Arc<QueueSignal>,
 	empty: Arc<SCondvar>,
@@ -139,6 +136,9 @@ pub struct VerificationQueue<K: Kind> {
 	ticks_since_adjustment: AtomicUsize,
 	max_queue_size: usize,
 	max_mem_use: usize,
+	scale_verifiers: bool,
+	verifier_handles: Vec<JoinHandle<()>>,	
+	state: Arc<(Mutex<State>, Condvar)>,
 }
 
 struct QueueSignal {
@@ -221,43 +221,45 @@ impl<K: Kind> VerificationQueue<K> {
 		});
 		let empty = Arc::new(SCondvar::new());
 		let panic_handler = PanicHandler::new_in_arc();
+		let scale_verifiers = config.verifier_settings.scale_verifiers;
 
-		let max_verifiers = min(::num_cpus::get(), MAX_VERIFIERS);
-		let default_amount = max(::num_cpus::get(), 3) - 2;
-		let mut verifiers = Vec::with_capacity(max_verifiers);
+		let num_cpus = ::num_cpus::get();
+		let max_verifiers = min(num_cpus, MAX_VERIFIERS);
+		let default_amount = max(1, min(max_verifiers, config.verifier_settings.num_verifiers));		
+		let state = Arc::new((Mutex::new(State::Work(default_amount)), Condvar::new()));		
+		let mut verifier_handles = Vec::with_capacity(max_verifiers);
 
 		debug!(target: "verification", "Allocating {} verifiers, {} initially active", max_verifiers, default_amount);
+		debug!(target: "verification", "Verifier auto-scaling {}", if scale_verifiers { "enabled" } else { "disabled" });
 
 		for i in 0..max_verifiers {
 			debug!(target: "verification", "Adding verification thread #{}", i);
 
-			let deleting = deleting.clone();
 			let panic_handler = panic_handler.clone();
 			let verification = verification.clone();
 			let engine = engine.clone();
 			let wait = more_to_verify.clone();
 			let ready = ready_signal.clone();
 			let empty = empty.clone();
+			let state = state.clone();
 
-			// enable only the first few verifiers.
-			let sleep = if i < default_amount {
-				Arc::new(AtomicBool::new(false))
-			} else {
-				Arc::new(AtomicBool::new(true))
-			};
-
-			verifiers.push(VerifierHandle {
-				deleting: deleting.clone(),
-				sleep: sleep.clone(),
-				thread: thread::Builder::new()
-					.name(format!("Verifier #{}", i))
-					.spawn(move || {
-						panic_handler.catch_panic(move || {
-							VerificationQueue::verify(verification, engine, wait, ready, deleting, empty, sleep)
-						}).unwrap()
-					})
-					.expect("Failed to create verifier thread.")
-			});
+			let handle = thread::Builder::new()
+				.name(format!("Verifier #{}", i))
+				.spawn(move || {
+					panic_handler.catch_panic(move || {
+						VerificationQueue::verify(
+							verification, 
+							engine, 
+							wait, 
+							ready, 
+							empty, 
+							state,
+							i,
+						)
+					}).unwrap()
+				})
+				.expect("Failed to create verifier thread.");
+			verifier_handles.push(handle);
 		}
 
 		VerificationQueue {
@@ -266,13 +268,15 @@ impl<K: Kind> VerificationQueue<K> {
 			ready_signal: ready_signal,
 			more_to_verify: more_to_verify,
 			verification: verification,
-			verifiers: Mutex::new((verifiers, default_amount)),
 			deleting: deleting,
 			processing: RwLock::new(HashSet::new()),
 			empty: empty,
 			ticks_since_adjustment: AtomicUsize::new(0),
 			max_queue_size: max(config.max_queue_size, MIN_QUEUE_LIMIT),
 			max_mem_use: max(config.max_mem_use, MIN_MEM_LIMIT),
+			scale_verifiers: scale_verifiers,
+			verifier_handles: verifier_handles,
+			state: state,
 		}
 	}
 
@@ -281,23 +285,30 @@ impl<K: Kind> VerificationQueue<K> {
 		engine: Arc<Engine>,
 		wait: Arc<SCondvar>,
 		ready: Arc<QueueSignal>,
-		deleting: Arc<AtomicBool>,
 		empty: Arc<SCondvar>,
-		sleep: Arc<AtomicBool>,
+		state: Arc<(Mutex<State>, Condvar)>,
+		id: usize,
 	) {
-		while !deleting.load(AtomicOrdering::Acquire) {
+		loop {
+			// check current state.
 			{
-				while sleep.load(AtomicOrdering::SeqCst) {
-					trace!(target: "verification", "Verifier sleeping");
-					::std::thread::park();
-					trace!(target: "verification", "Verifier waking up");
+				let mut cur_state = state.0.lock();
+				while let State::Work(x) = *cur_state {
+					// sleep until this thread is required.
+					if id < x { break }
 
-					if deleting.load(AtomicOrdering::Acquire) {
-						return;
-					}
+					debug!(target: "verification", "verifier {} sleeping", id);
+					state.1.wait(&mut cur_state);
+					debug!(target: "verification", "verifier {} waking up", id);					
+				}
+
+				if let State::Exit = *cur_state { 
+					debug!(target: "verification", "verifier {} exiting", id);										
+					break;
 				}
 			}
 
+			// wait for work if empty.
 			{
 				let mut more_to_verify = verification.more_to_verify.lock().unwrap();
 
@@ -305,15 +316,22 @@ impl<K: Kind> VerificationQueue<K> {
 					empty.notify_all();
 				}
 
-				while verification.unverified.lock().is_empty() && !deleting.load(AtomicOrdering::Acquire) {
+				while verification.unverified.lock().is_empty() {
+					if let State::Exit = *state.0.lock() {
+						debug!(target: "verification", "verifier {} exiting", id);
+						return;
+					}
+
 					more_to_verify = wait.wait(more_to_verify).unwrap();
 				}
 
-				if deleting.load(AtomicOrdering::Acquire) {
+				if let State::Exit = *state.0.lock() {
+					debug!(target: "verification", "verifier {} exiting", id);										
 					return;
 				}
 			}
 
+			// do work.
 			let item = {
 				// acquire these locks before getting the item to verify.
 				let mut unverified = verification.unverified.lock();
@@ -568,6 +586,14 @@ impl<K: Kind> VerificationQueue<K> {
 		}
 	}
 
+	/// Get the current number of working verifiers.
+	pub fn num_verifiers(&self) -> usize {
+		match *self.state.0.lock() {
+			State::Work(x) => x,
+			State::Exit => panic!("state only set to exit on drop; queue live now; qed"),
+		}
+	}
+
 	/// Optimise memory footprint of the heap fields, and adjust the number of threads
 	/// to better suit the workload.
 	pub fn collect_garbage(&self) {
@@ -598,13 +624,15 @@ impl<K: Kind> VerificationQueue<K> {
 
 		self.processing.write().shrink_to_fit();
 
+		if !self.scale_verifiers { return }
+
 		if self.ticks_since_adjustment.fetch_add(1, AtomicOrdering::SeqCst) + 1 >= READJUSTMENT_PERIOD {
 			self.ticks_since_adjustment.store(0, AtomicOrdering::SeqCst);
 		} else {
 			return;
 		}
 
-		let current = self.verifiers.lock().1;
+		let current = self.num_verifiers();
 
 		let diff = (v_len - u_len).abs();
 		let total = v_len + u_len;
@@ -626,27 +654,14 @@ impl<K: Kind> VerificationQueue<K> {
 	// possible, never going over the amount of initially allocated threads
 	// or below 1.
 	fn scale_verifiers(&self, target: usize) {
-		let mut verifiers = self.verifiers.lock();
-		let &mut (ref mut verifiers, ref mut verifier_count) = &mut *verifiers;
-
-		let target = min(verifiers.len(), target);
+		let current = self.num_verifiers();
+		let target = min(self.verifier_handles.len(), target);
 		let target = max(1, target);
 
-		debug!(target: "verification", "Scaling from {} to {} verifiers", verifier_count, target);
+		debug!(target: "verification", "Scaling from {} to {} verifiers", current, target);
 
-		// scaling up
-		for i in *verifier_count..target {
-			debug!(target: "verification", "Waking up verifier {}", i);
-			verifiers[i].wake_up();
-		}
-
-		// scaling down.
-		for i in target..*verifier_count {
-			debug!(target: "verification", "Putting verifier {} to sleep", i);
-			verifiers[i].sleep();
-		}
-
-		*verifier_count = target;
+		*self.state.0.lock() = State::Work(target);
+		self.state.1.notify_all();
 	}
 }
 
@@ -660,22 +675,18 @@ impl<K: Kind> Drop for VerificationQueue<K> {
 	fn drop(&mut self) {
 		trace!(target: "shutdown", "[VerificationQueue] Closing...");
 		self.clear();
-		self.deleting.store(true, AtomicOrdering::Release);
+		self.deleting.store(true, AtomicOrdering::SeqCst);
 
-		let mut verifiers = self.verifiers.get_mut();
-		let mut verifiers = &mut verifiers.0;
-
-		// first pass to signal conclusion. must be done before
-		// notify or deadlock possible.
-		for handle in verifiers.iter() {
-			handle.conclude();
-		}
+		// set exit state; should be done before `more_to_verify` notification.
+		*self.state.0.lock() = State::Exit;
+		self.state.1.notify_all();
 
+		// wake up all threads waiting for more work.
 		self.more_to_verify.notify_all();
 
-		// second pass to join.
-		for handle in verifiers.drain(..) {
-			handle.join();
+		// wait for all verifier threads to join.
+		for thread in self.verifier_handles.drain(..) {
+			thread.join().expect("Propagating verifier thread panic on shutdown");
 		}
 
 		trace!(target: "shutdown", "[VerificationQueue] Closed.");
@@ -687,16 +698,21 @@ mod tests {
 	use util::*;
 	use io::*;
 	use spec::*;
-	use super::{BlockQueue, Config};
+	use super::{BlockQueue, Config, State};
 	use super::kind::blocks::Unverified;
 	use tests::helpers::*;
 	use error::*;
 	use views::*;
 
-	fn get_test_queue() -> BlockQueue {
+	// create a test block queue.
+	// auto_scaling enables verifier adjustment.
+	fn get_test_queue(auto_scale: bool) -> BlockQueue {
 		let spec = get_test_spec();
 		let engine = spec.engine;
-		BlockQueue::new(Config::default(), engine, IoChannel::disconnected(), true)
+
+		let mut config = Config::default();
+		config.verifier_settings.scale_verifiers = auto_scale;
+		BlockQueue::new(config, engine, IoChannel::disconnected(), true)
 	}
 
 	#[test]
@@ -709,7 +725,7 @@ mod tests {
 
 	#[test]
 	fn can_import_blocks() {
-		let queue = get_test_queue();
+		let queue = get_test_queue(false);
 		if let Err(e) = queue.import(Unverified::new(get_good_dummy_block())) {
 			panic!("error importing block that is valid by definition({:?})", e);
 		}
@@ -717,7 +733,7 @@ mod tests {
 
 	#[test]
 	fn returns_error_for_duplicates() {
-		let queue = get_test_queue();
+		let queue = get_test_queue(false);
 		if let Err(e) = queue.import(Unverified::new(get_good_dummy_block())) {
 			panic!("error importing block that is valid by definition({:?})", e);
 		}
@@ -736,7 +752,7 @@ mod tests {
 
 	#[test]
 	fn returns_ok_for_drained_duplicates() {
-		let queue = get_test_queue();
+		let queue = get_test_queue(false);
 		let block = get_good_dummy_block();
 		let hash = BlockView::new(&block).header().hash().clone();
 		if let Err(e) = queue.import(Unverified::new(block)) {
@@ -753,7 +769,7 @@ mod tests {
 
 	#[test]
 	fn returns_empty_once_finished() {
-		let queue = get_test_queue();
+		let queue = get_test_queue(false);
 		queue.import(Unverified::new(get_good_dummy_block()))
 			.expect("error importing block that is valid by definition");
 		queue.flush();
@@ -781,30 +797,23 @@ mod tests {
 	fn scaling_limits() {
 		use super::MAX_VERIFIERS;
 
-		let queue = get_test_queue();
+		let queue = get_test_queue(true);
 		queue.scale_verifiers(MAX_VERIFIERS + 1);
 
-		assert!(queue.verifiers.lock().1 < MAX_VERIFIERS + 1);
+		assert!(queue.num_verifiers() < MAX_VERIFIERS + 1);
 
 		queue.scale_verifiers(0);
 
-		assert!(queue.verifiers.lock().1 == 1);
+		assert!(queue.num_verifiers() == 1);
 	}
 
 	#[test]
 	fn readjust_verifiers() {
-		let queue = get_test_queue();
+		let queue = get_test_queue(true);
 
 		// put all the verifiers to sleep to ensure 
 		// the test isn't timing sensitive.
-		let num_verifiers = {
-			let verifiers = queue.verifiers.lock();
-			for i in 0..verifiers.1 {
-				verifiers.0[i].sleep();
-			}
-
-			verifiers.1
-		};
+		*queue.state.0.lock() = State::Work(0);
 
 		for block in get_good_dummy_block_seq(5000) {
 			queue.import(Unverified::new(block)).expect("Block good by definition; qed");
@@ -812,20 +821,12 @@ mod tests {
 
 		// almost all unverified == bump verifier count.
 		queue.collect_garbage();
-		assert_eq!(queue.verifiers.lock().1, num_verifiers + 1);
-
-		// wake them up again and verify everything.
-		{
-			let verifiers = queue.verifiers.lock();
-			for i in 0..verifiers.1 {
-				verifiers.0[i].wake_up();
-			}
-		}
+		assert_eq!(queue.num_verifiers(), 1);
 
 		queue.flush();
 
 		// nothing to verify == use minimum number of verifiers.
 		queue.collect_garbage();
-		assert_eq!(queue.verifiers.lock().1, 1);
+		assert_eq!(queue.num_verifiers(), 1);
 	}
 }