From 83b8e7df5a6f4bdee8e0ddc208fe44029d4a2517 Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Mon, 29 Feb 2016 14:57:41 +0100
Subject: [PATCH 01/22] Initial refactor and block closing.

---
 ethcore/src/block.rs  | 53 +++++++++++++++++++------------------------
 ethcore/src/client.rs | 39 +++++++++++++++++++++++++++----
 ethcore/src/header.rs |  2 +-
 parity/main.rs        |  1 -
 4 files changed, 59 insertions(+), 36 deletions(-)

diff --git a/ethcore/src/block.rs b/ethcore/src/block.rs
index 70c6c2fb2..28005b17e 100644
--- a/ethcore/src/block.rs
+++ b/ethcore/src/block.rs
@@ -155,9 +155,9 @@ pub struct OpenBlock<'x> {
 /// Just like OpenBlock, except that we've applied `Engine::on_close_block`, finished up the non-seal header fields,
 /// and collected the uncles.
 ///
-/// There is no function available to push a transaction. If you want that you'll need to `reopen()` it.
-pub struct ClosedBlock<'x> {
-	open_block: OpenBlock<'x>,
+/// There is no function available to push a transaction.
+pub struct ClosedBlock {
+	block: ExecutedBlock,
 	uncle_bytes: Bytes,
 }
 
@@ -181,7 +181,7 @@ impl<'x> OpenBlock<'x> {
 		r.block.base.header.set_number(parent.number() + 1);
 		r.block.base.header.set_author(author);
 		r.block.base.header.set_extra_data(extra_data);
-		r.block.base.header.set_timestamp_now();
+		r.block.base.header.set_timestamp_now(parent.timestamp());
 
 		engine.populate_from_parent(&mut r.block.base.header, parent);
 		engine.on_new_block(&mut r.block);
@@ -259,7 +259,7 @@ impl<'x> OpenBlock<'x> {
 	}
 
 	/// Turn this into a `ClosedBlock`. A BlockChain must be provided in order to figure out the uncles.
-	pub fn close(self) -> ClosedBlock<'x> {
+	pub fn close(self) -> ClosedBlock {
 		let mut s = self;
 		s.engine.on_close_block(&mut s.block);
 		s.block.base.header.transactions_root = ordered_trie_root(s.block.base.transactions.iter().map(|ref e| e.rlp_bytes().to_vec()).collect());
@@ -271,7 +271,10 @@ impl<'x> OpenBlock<'x> {
 		s.block.base.header.gas_used = s.block.receipts.last().map_or(U256::zero(), |r| r.gas_used);
 		s.block.base.header.note_dirty();
 
-		ClosedBlock::new(s, uncle_bytes)
+		ClosedBlock {
+			block: s.block, 
+			uncle_bytes: uncle_bytes,
+		}
 	}
 }
 
@@ -279,38 +282,28 @@ impl<'x> IsBlock for OpenBlock<'x> {
 	fn block(&self) -> &ExecutedBlock { &self.block }
 }
 
-impl<'x> IsBlock for ClosedBlock<'x> {
-	fn block(&self) -> &ExecutedBlock { &self.open_block.block }
+impl<'x> IsBlock for ClosedBlock {
+	fn block(&self) -> &ExecutedBlock { &self.block }
 }
 
-impl<'x> ClosedBlock<'x> {
-	fn new(open_block: OpenBlock<'x>, uncle_bytes: Bytes) -> Self {
-		ClosedBlock {
-			open_block: open_block,
-			uncle_bytes: uncle_bytes,
-		}
-	}
-
+impl ClosedBlock {
 	/// Get the hash of the header without seal arguments.
 	pub fn hash(&self) -> H256 { self.header().rlp_sha3(Seal::Without) }
 
 	/// Provide a valid seal in order to turn this into a `SealedBlock`.
 	///
 	/// NOTE: This does not check the validity of `seal` with the engine.
-	pub fn seal(self, seal: Vec<Bytes>) -> Result<SealedBlock, BlockError> {
+	pub fn seal(self, engine: &Engine, seal: Vec<Bytes>) -> Result<SealedBlock, BlockError> {
 		let mut s = self;
-		if seal.len() != s.open_block.engine.seal_fields() {
-			return Err(BlockError::InvalidSealArity(Mismatch{expected: s.open_block.engine.seal_fields(), found: seal.len()}));
+		if seal.len() != engine.seal_fields() {
+			return Err(BlockError::InvalidSealArity(Mismatch{expected: engine.seal_fields(), found: seal.len()}));
 		}
-		s.open_block.block.base.header.set_seal(seal);
-		Ok(SealedBlock { block: s.open_block.block, uncle_bytes: s.uncle_bytes })
+		s.block.base.header.set_seal(seal);
+		Ok(SealedBlock { block: s.block, uncle_bytes: s.uncle_bytes })
 	}
 
-	/// Turn this back into an `OpenBlock`.
-	pub fn reopen(self) -> OpenBlock<'x> { self.open_block }
-
 	/// Drop this object and return the underlieing database.
-	pub fn drain(self) -> JournalDB { self.open_block.block.state.drop().1 }
+	pub fn drain(self) -> JournalDB { self.block.state.drop().1 }
 }
 
 impl SealedBlock {
@@ -332,7 +325,7 @@ impl IsBlock for SealedBlock {
 }
 
 /// Enact the block given by block header, transactions and uncles
-pub fn enact<'x>(header: &Header, transactions: &[SignedTransaction], uncles: &[Header], engine: &'x Engine, db: JournalDB, parent: &Header, last_hashes: LastHashes) -> Result<ClosedBlock<'x>, Error> {
+pub fn enact(header: &Header, transactions: &[SignedTransaction], uncles: &[Header], engine: &Engine, db: JournalDB, parent: &Header, last_hashes: LastHashes) -> Result<ClosedBlock, Error> {
 	{
 		if ::log::max_log_level() >= ::log::LogLevel::Trace {
 			let s = State::from_existing(db.clone(), parent.state_root().clone(), engine.account_start_nonce());
@@ -350,14 +343,14 @@ pub fn enact<'x>(header: &Header, transactions: &[SignedTransaction], uncles: &[
 }
 
 /// Enact the block given by `block_bytes` using `engine` on the database `db` with given `parent` block header
-pub fn enact_bytes<'x>(block_bytes: &[u8], engine: &'x Engine, db: JournalDB, parent: &Header, last_hashes: LastHashes) -> Result<ClosedBlock<'x>, Error> {
+pub fn enact_bytes(block_bytes: &[u8], engine: &Engine, db: JournalDB, parent: &Header, last_hashes: LastHashes) -> Result<ClosedBlock, Error> {
 	let block = BlockView::new(block_bytes);
 	let header = block.header();
 	enact(&header, &block.transactions(), &block.uncles(), engine, db, parent, last_hashes)
 }
 
 /// Enact the block given by `block_bytes` using `engine` on the database `db` with given `parent` block header
-pub fn enact_verified<'x>(block: &PreVerifiedBlock, engine: &'x Engine, db: JournalDB, parent: &Header, last_hashes: LastHashes) -> Result<ClosedBlock<'x>, Error> {
+pub fn enact_verified(block: &PreVerifiedBlock, engine: &Engine, db: JournalDB, parent: &Header, last_hashes: LastHashes) -> Result<ClosedBlock, Error> {
 	let view = BlockView::new(&block.bytes);
 	enact(&block.header, &block.transactions, &view.uncles(), engine, db, parent, last_hashes)
 }
@@ -365,7 +358,7 @@ pub fn enact_verified<'x>(block: &PreVerifiedBlock, engine: &'x Engine, db: Jour
 /// Enact the block given by `block_bytes` using `engine` on the database `db` with given `parent` block header. Seal the block aferwards
 pub fn enact_and_seal(block_bytes: &[u8], engine: &Engine, db: JournalDB, parent: &Header, last_hashes: LastHashes) -> Result<SealedBlock, Error> {
 	let header = BlockView::new(block_bytes).header_view();
-	Ok(try!(try!(enact_bytes(block_bytes, engine, db, parent, last_hashes)).seal(header.seal())))
+	Ok(try!(try!(enact_bytes(block_bytes, engine, db, parent, last_hashes)).seal(engine, header.seal())))
 }
 
 #[cfg(test)]
@@ -386,7 +379,7 @@ mod tests {
 		let last_hashes = vec![genesis_header.hash()];
 		let b = OpenBlock::new(engine.deref(), db, &genesis_header, last_hashes, Address::zero(), vec![]);
 		let b = b.close();
-		let _ = b.seal(vec![]);
+		let _ = b.seal(engine.deref(), vec![]);
 	}
 
 	#[test]
diff --git a/ethcore/src/client.rs b/ethcore/src/client.rs
index 5d71eed84..c378fa449 100644
--- a/ethcore/src/client.rs
+++ b/ethcore/src/client.rs
@@ -193,6 +193,9 @@ pub struct Client {
 	report: RwLock<ClientReport>,
 	import_lock: Mutex<()>,
 	panic_handler: Arc<PanicHandler>,
+
+	// for sealing...
+	_sealing_block: Mutex<Option<ClosedBlock>>,
 }
 
 const HISTORY: u64 = 1000;
@@ -228,7 +231,8 @@ impl Client {
 			block_queue: RwLock::new(block_queue),
 			report: RwLock::new(Default::default()),
 			import_lock: Mutex::new(()),
-			panic_handler: panic_handler
+			panic_handler: panic_handler,
+			_sealing_block: Mutex::new(None),
 		}))
 	}
 
@@ -237,10 +241,10 @@ impl Client {
 		self.block_queue.write().unwrap().flush();
 	}
 
-	fn build_last_hashes(&self, header: &Header) -> LastHashes {
+	fn build_last_hashes(&self, parent_hash: H256) -> LastHashes {
 		let mut last_hashes = LastHashes::new();
 		last_hashes.resize(256, H256::new());
-		last_hashes[0] = header.parent_hash.clone();
+		last_hashes[0] = parent_hash;
 		let chain = self.chain.read().unwrap();
 		for i in 0..255 {
 			match chain.block_details(&last_hashes[i]) {
@@ -273,7 +277,7 @@ impl Client {
 
 		// Enact Verified Block
 		let parent = chain_has_parent.unwrap();
-		let last_hashes = self.build_last_hashes(header);
+		let last_hashes = self.build_last_hashes(header.parent_hash.clone());
 		let db = self.state_db.lock().unwrap().clone();
 
 		let enact_result = enact_verified(&block, engine, db, &parent, last_hashes);
@@ -302,6 +306,8 @@ impl Client {
 		let _import_lock = self.import_lock.lock();
 		let blocks = self.block_queue.write().unwrap().drain(max_blocks_to_import);
 
+		let original_best = self.chain_info().best_block_hash;
+
 		for block in blocks {
 			let header = &block.header;
 
@@ -357,6 +363,10 @@ impl Client {
 			}
 		}
 
+		if self.chain_info().best_block_hash != original_best {
+			self.new_chain_head();
+		}
+
 		imported
 	}
 
@@ -403,8 +413,29 @@ impl Client {
 			BlockId::Latest => Some(self.chain.read().unwrap().best_block_number())
 		}
 	}
+
+	/// New chain head event.
+	pub fn new_chain_head(&self) {
+		let h = self.chain.read().unwrap().best_block_hash();
+		info!("NEW CHAIN HEAD: #{}: {}", self.chain.read().unwrap().best_block_number(), h);
+
+		info!("Preparing to seal.");
+		let b = OpenBlock::new(
+			&self.engine,
+			self.state_db.lock(),
+			self.chain.read().unwrap().block_header(&h).unwrap_or_else(|| {return;}),
+			self.build_last_hashes(h.clone()),
+			x!("0037a6b811ffeb6e072da21179d11b1406371c63"),
+			b"Parity".to_owned()
+		);
+		let b = b.close();
+		info!("Sealed: hash={}, diff={}, number={}", b.hash(), b.block().difficulty(), b.block().number());
+		*self._sealing_block.lock().unwrap() = Some(b);
+	}
 }
 
+// TODO: need MinerService MinerIoHandler
+
 impl BlockChainClient for Client {
 	fn block_header(&self, id: BlockId) -> Option<Bytes> {
 		let chain = self.chain.read().unwrap();
diff --git a/ethcore/src/header.rs b/ethcore/src/header.rs
index 6ee682544..3db0be5ff 100644
--- a/ethcore/src/header.rs
+++ b/ethcore/src/header.rs
@@ -131,7 +131,7 @@ impl Header {
 	/// Set the timestamp field of the header.
 	pub fn set_timestamp(&mut self, a: u64) { self.timestamp = a; self.note_dirty(); }
 	/// Set the timestamp field of the header to the current time.
-	pub fn set_timestamp_now(&mut self) { self.timestamp = now_utc().to_timespec().sec as u64; self.note_dirty(); }
+	pub fn set_timestamp_now(&mut self, but_later_than: u64) { self.timestamp = max(now_utc().to_timespec().sec as u64, but_later_than + 1); self.note_dirty(); }
 	/// Set the author field of the header.
 	pub fn set_author(&mut self, a: Address) { if a != self.author { self.author = a; self.note_dirty(); } }
 
diff --git a/parity/main.rs b/parity/main.rs
index 6415dfc33..ff86b1663 100644
--- a/parity/main.rs
+++ b/parity/main.rs
@@ -354,7 +354,6 @@ impl Default for Informant {
 }
 
 impl Informant {
-
 	fn format_bytes(b: usize) -> String {
 		match binary_prefix(b as f64) {
 			Standalone(bytes)   => format!("{} bytes", bytes),

From e20858a5dc048c06bac6d3e744979e9fc3ff1639 Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Mon, 29 Feb 2016 15:30:08 +0100
Subject: [PATCH 02/22] Compile fixes.

---
 ethcore/src/client.rs | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/ethcore/src/client.rs b/ethcore/src/client.rs
index c378fa449..a4ef970a5 100644
--- a/ethcore/src/client.rs
+++ b/ethcore/src/client.rs
@@ -21,7 +21,7 @@ use util::panics::*;
 use blockchain::{BlockChain, BlockProvider};
 use views::BlockView;
 use error::*;
-use header::{BlockNumber, Header};
+use header::{BlockNumber};
 use state::State;
 use spec::Spec;
 use engine::Engine;
@@ -421,15 +421,15 @@ impl Client {
 
 		info!("Preparing to seal.");
 		let b = OpenBlock::new(
-			&self.engine,
-			self.state_db.lock(),
-			self.chain.read().unwrap().block_header(&h).unwrap_or_else(|| {return;}),
+			self.engine.deref().deref(),
+			self.state_db.lock().unwrap().clone(),
+			match self.chain.read().unwrap().block_header(&h) { Some(ref x) => x, None => {return;} },
 			self.build_last_hashes(h.clone()),
 			x!("0037a6b811ffeb6e072da21179d11b1406371c63"),
-			b"Parity".to_owned()
+			b"Parity".to_vec()
 		);
 		let b = b.close();
-		info!("Sealed: hash={}, diff={}, number={}", b.hash(), b.block().difficulty(), b.block().number());
+		info!("Sealed: hash={}, diff={}, number={}", b.hash(), b.block().header().difficulty(), b.block().header().number());
 		*self._sealing_block.lock().unwrap() = Some(b);
 	}
 }

From ffc5c2ea7bf5747acbbc87dca25e37943312d771 Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Mon, 29 Feb 2016 19:30:13 +0100
Subject: [PATCH 03/22] eth_getwork implemented.

---
 Cargo.lock                     |  1 +
 ethash/src/compute.rs          |  3 ++-
 ethash/src/lib.rs              |  4 ++--
 ethcore/src/client.rs          | 13 +++++++------
 ethcore/src/ethereum/ethash.rs | 14 ++++++++++----
 rpc/Cargo.toml                 |  1 +
 rpc/src/v1/impls/eth.rs        | 27 +++++++++++++++++++++++++++
 util/src/misc.rs               |  2 +-
 util/src/uint.rs               | 27 +++++++++++++++++++++++++++
 9 files changed, 78 insertions(+), 14 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index bca236813..9c225dbbe 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -203,6 +203,7 @@ name = "ethcore-rpc"
 version = "0.9.99"
 dependencies = [
  "clippy 0.0.44 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ethash 0.9.99",
  "ethcore 0.9.99",
  "ethcore-util 0.9.99",
  "ethsync 0.9.99",
diff --git a/ethash/src/compute.rs b/ethash/src/compute.rs
index 6c311993b..eb64151d0 100644
--- a/ethash/src/compute.rs
+++ b/ethash/src/compute.rs
@@ -172,7 +172,8 @@ fn get_data_size(block_number: u64) -> usize {
 }
 
 #[inline]
-fn get_seedhash(block_number: u64) -> H256 {
+/// Given the `block_number`, determine the seed hash for Ethash.
+pub fn get_seedhash(block_number: u64) -> H256 {
 	let epochs = block_number / ETHASH_EPOCH_LENGTH;
 	let mut ret: H256 = [0u8; 32];
 	for _ in 0..epochs {
diff --git a/ethash/src/lib.rs b/ethash/src/lib.rs
index e96b98b81..982f7129b 100644
--- a/ethash/src/lib.rs
+++ b/ethash/src/lib.rs
@@ -24,7 +24,7 @@ mod compute;
 
 use std::mem;
 use compute::Light;
-pub use compute::{quick_get_difficulty, H256, ProofOfWork, ETHASH_EPOCH_LENGTH};
+pub use compute::{get_seedhash, quick_get_difficulty, H256, ProofOfWork, ETHASH_EPOCH_LENGTH};
 
 use std::sync::{Arc, Mutex};
 
@@ -35,7 +35,7 @@ struct LightCache {
 	prev: Option<Arc<Light>>,
 }
 
-/// Lighy/Full cache manager
+/// Light/Full cache manager.
 pub struct EthashManager {
 	cache: Mutex<LightCache>,
 }
diff --git a/ethcore/src/client.rs b/ethcore/src/client.rs
index d81507d25..f634579ad 100644
--- a/ethcore/src/client.rs
+++ b/ethcore/src/client.rs
@@ -195,7 +195,7 @@ pub struct Client {
 	panic_handler: Arc<PanicHandler>,
 
 	// for sealing...
-	_sealing_block: Mutex<Option<ClosedBlock>>,
+	sealing_block: Mutex<Option<ClosedBlock>>,
 }
 
 const HISTORY: u64 = 1000;
@@ -232,7 +232,7 @@ impl Client {
 			report: RwLock::new(Default::default()),
 			import_lock: Mutex::new(()),
 			panic_handler: panic_handler,
-			_sealing_block: Mutex::new(None),
+			sealing_block: Mutex::new(None),
 		}))
 	}
 
@@ -417,9 +417,7 @@ impl Client {
 	/// New chain head event.
 	pub fn new_chain_head(&self) {
 		let h = self.chain.read().unwrap().best_block_hash();
-		info!("NEW CHAIN HEAD: #{}: {}", self.chain.read().unwrap().best_block_number(), h);
-
-		info!("Preparing to seal.");
+		info!("New best block: #{}: {}", self.chain.read().unwrap().best_block_number(), h);
 		let b = OpenBlock::new(
 			self.engine.deref().deref(),
 			self.state_db.lock().unwrap().clone(),
@@ -430,8 +428,11 @@ impl Client {
 		);
 		let b = b.close();
 		info!("Sealed: hash={}, diff={}, number={}", b.hash(), b.block().header().difficulty(), b.block().header().number());
-		*self._sealing_block.lock().unwrap() = Some(b);
+		*self.sealing_block.lock().unwrap() = Some(b);
 	}
+
+	/// Grab the `ClosedBlock` that we want to be sealed. Comes as a mutex that you have to lock.
+	pub fn sealing_block(&self) -> &Mutex<Option<ClosedBlock>> { &self.sealing_block }
 }
 
 // TODO: need MinerService MinerIoHandler
diff --git a/ethcore/src/ethereum/ethash.rs b/ethcore/src/ethereum/ethash.rs
index 54f02524d..4f1ef1ce3 100644
--- a/ethcore/src/ethereum/ethash.rs
+++ b/ethcore/src/ethereum/ethash.rs
@@ -144,9 +144,9 @@ impl Engine for Ethash {
 		}
 
 		let difficulty = Ethash::boundary_to_difficulty(&Ethash::from_ethash(quick_get_difficulty(
-				&Ethash::to_ethash(header.bare_hash()),
-				header.nonce().low_u64(),
-				&Ethash::to_ethash(header.mix_hash()))));
+			&Ethash::to_ethash(header.bare_hash()),
+			header.nonce().low_u64(),
+			&Ethash::to_ethash(header.mix_hash()) )));
 		if difficulty < header.difficulty {
 			return Err(From::from(BlockError::InvalidProofOfWork(OutOfBounds { min: Some(header.difficulty), max: None, found: difficulty })));
 		}
@@ -241,10 +241,16 @@ impl Ethash {
 		target
 	}
 
-	fn boundary_to_difficulty(boundary: &H256) -> U256 {
+	/// Convert an Ethash boundary to its original difficulty. Basically just `f(x) = 2^256 / x`.
+	pub fn boundary_to_difficulty(boundary: &H256) -> U256 {
 		U256::from((U512::one() << 256) / x!(U256::from(boundary.as_slice())))
 	}
 
+	/// Convert an Ethash difficulty to the target boundary. Basically just `f(x) = 2^256 / x`.
+	pub fn difficulty_to_boundary(difficulty: &U256) -> H256 {
+		x!(U256::from((U512::one() << 256) / x!(difficulty)))
+	}
+
 	fn to_ethash(hash: H256) -> EH256 {
 		unsafe { mem::transmute(hash) }
 	}
diff --git a/rpc/Cargo.toml b/rpc/Cargo.toml
index b9ca9deac..c38684643 100644
--- a/rpc/Cargo.toml
+++ b/rpc/Cargo.toml
@@ -15,6 +15,7 @@ jsonrpc-core = "1.2"
 jsonrpc-http-server = "2.1"
 ethcore-util = { path = "../util" }
 ethcore = { path = "../ethcore" }
+ethash = { path = "../ethash" }
 ethsync = { path = "../sync" }
 clippy = { version = "0.0.44", optional = true }
 rustc-serialize = "0.3"
diff --git a/rpc/src/v1/impls/eth.rs b/rpc/src/v1/impls/eth.rs
index 00bce5437..5791b7418 100644
--- a/rpc/src/v1/impls/eth.rs
+++ b/rpc/src/v1/impls/eth.rs
@@ -22,7 +22,11 @@ use util::hash::*;
 use util::uint::*;
 use util::sha3::*;
 use ethcore::client::*;
+use ethcore::block::{IsBlock};
 use ethcore::views::*;
+extern crate ethash;
+use self::ethash::get_seedhash;
+use ethcore::ethereum::Ethash;
 use ethcore::ethereum::denominations::shannon;
 use v1::traits::{Eth, EthFilter};
 use v1::types::{Block, BlockTransactions, BlockNumber, Bytes, SyncStatus, SyncInfo, Transaction, OptionalValue, Index, Filter, Log};
@@ -209,6 +213,29 @@ impl Eth for EthClient {
 				to_value(&logs)
 			})
 	}
+
+	fn work(&self, params: Params) -> Result<Value, Error> {
+		match params {
+			Params::None => {
+				let c = take_weak!(self.client);
+				let u = c.sealing_block().lock().unwrap();
+				match *u {
+					Some(ref b) => {
+						let current_hash = b.hash();
+						let target = Ethash::difficulty_to_boundary(b.block().header().difficulty());
+						let seed_hash = get_seedhash(b.block().header().number());
+						to_value(&(current_hash, seed_hash, target))
+					}
+					_ => Err(Error::invalid_params())
+				}
+			},
+			_ => Err(Error::invalid_params())
+		}
+	}
+
+//	fn submit_work(&self, _: Params) -> Result<Value, Error> { rpc_unimplemented!() }
+
+//	fn submit_hashrate(&self, _: Params) -> Result<Value, Error> { rpc_unimplemented!() }
 }
 
 /// Eth filter rpc implementation.
diff --git a/util/src/misc.rs b/util/src/misc.rs
index 289f1c50c..35e1f3a75 100644
--- a/util/src/misc.rs
+++ b/util/src/misc.rs
@@ -69,5 +69,5 @@ pub fn contents(name: &str) -> Result<Bytes, UtilError> {
 
 /// Get the standard version string for this software.
 pub fn version() -> String {
-	format!("Parity//{}-{}-{}/{}-{}-{}/rustc{}", env!("CARGO_PKG_VERSION"), short_sha(), commit_date().replace("-", ""), Target::arch(), Target::os(), Target::env(), rustc_version::version())
+	format!("Parity//v{}-{}-{}/{}-{}-{}/rustc{}", env!("CARGO_PKG_VERSION"), short_sha(), commit_date().replace("-", ""), Target::arch(), Target::os(), Target::env(), rustc_version::version())
 }
\ No newline at end of file
diff --git a/util/src/uint.rs b/util/src/uint.rs
index 517b7a29f..7f2e3d3b1 100644
--- a/util/src/uint.rs
+++ b/util/src/uint.rs
@@ -1124,6 +1124,33 @@ impl From<U512> for U256 {
 	}
 }
 
+impl<'a> From<&'a U256> for U512 {
+	fn from(value: &'a U256) -> U512 {
+		let U256(ref arr) = *value;
+		let mut ret = [0; 8];
+		ret[0] = arr[0];
+		ret[1] = arr[1];
+		ret[2] = arr[2];
+		ret[3] = arr[3];
+		U512(ret)
+	}
+}
+
+impl<'a> From<&'a U512> for U256 {
+	fn from(value: &'a U512) -> U256 {
+		let U512(ref arr) = *value;
+		if arr[4] | arr[5] | arr[6] | arr[7] != 0 {
+			panic!("Overflow");
+		}
+		let mut ret = [0; 4];
+		ret[0] = arr[0];
+		ret[1] = arr[1];
+		ret[2] = arr[2];
+		ret[3] = arr[3];
+		U256(ret)
+	}
+}
+
 impl From<U256> for U128 {
 	fn from(value: U256) -> U128 {
 		let U256(ref arr) = value;

From 394e9c679bfb0e49c51a67b05001043c648a76cc Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Tue, 1 Mar 2016 00:02:48 +0100
Subject: [PATCH 04/22] Reorganised ImportError to be a type of Errpr (rather
 than vice-versa). Added support for eth_submitWork.

---
 ethcore/src/block.rs           | 16 ++++++++++++--
 ethcore/src/block_queue.rs     | 24 ++++++++++----------
 ethcore/src/client.rs          | 40 +++++++++++++++++++++++++++-------
 ethcore/src/engine.rs          |  2 --
 ethcore/src/error.rs           | 34 ++++++++++++++++-------------
 ethcore/src/ethereum/ethash.rs |  9 ++++----
 ethcore/src/verification.rs    |  8 +++----
 rpc/src/v1/impls/eth.rs        | 13 ++++++++---
 sync/src/chain.rs              | 12 +++++-----
 9 files changed, 102 insertions(+), 56 deletions(-)

diff --git a/ethcore/src/block.rs b/ethcore/src/block.rs
index 28005b17e..f72c2f800 100644
--- a/ethcore/src/block.rs
+++ b/ethcore/src/block.rs
@@ -21,7 +21,7 @@
 use common::*;
 use engine::*;
 use state::*;
-use verification::PreVerifiedBlock;
+use verification::PreverifiedBlock;
 
 /// A block, encoded as it is on the block chain.
 // TODO: rename to Block
@@ -302,6 +302,18 @@ impl ClosedBlock {
 		Ok(SealedBlock { block: s.block, uncle_bytes: s.uncle_bytes })
 	}
 
+	/// Provide a valid seal in order to turn this into a `SealedBlock`.
+	/// This does check the validity of `seal` with the engine.
+	/// Returns the `ClosedBlock` back again if the seal is no good.
+	pub fn try_seal(self, engine: &Engine, seal: Vec<Bytes>) -> Result<SealedBlock, ClosedBlock> {
+		let mut s = self;
+		s.block.base.header.set_seal(seal);
+		match engine.verify_block_basic(&s.block.base.header, None).is_err() || engine.verify_block_unordered(&s.block.base.header, None).is_err() {
+			false => Err(s),
+			true => Ok(SealedBlock { block: s.block, uncle_bytes: s.uncle_bytes }),
+		}
+	}
+
 	/// Drop this object and return the underlieing database.
 	pub fn drain(self) -> JournalDB { self.block.state.drop().1 }
 }
@@ -350,7 +362,7 @@ pub fn enact_bytes(block_bytes: &[u8], engine: &Engine, db: JournalDB, parent: &
 }
 
 /// Enact the block given by `block_bytes` using `engine` on the database `db` with given `parent` block header
-pub fn enact_verified(block: &PreVerifiedBlock, engine: &Engine, db: JournalDB, parent: &Header, last_hashes: LastHashes) -> Result<ClosedBlock, Error> {
+pub fn enact_verified(block: &PreverifiedBlock, engine: &Engine, db: JournalDB, parent: &Header, last_hashes: LastHashes) -> Result<ClosedBlock, Error> {
 	let view = BlockView::new(&block.bytes);
 	enact(&block.header, &block.transactions, &view.uncles(), engine, db, parent, last_hashes)
 }
diff --git a/ethcore/src/block_queue.rs b/ethcore/src/block_queue.rs
index 668c004e5..143f53647 100644
--- a/ethcore/src/block_queue.rs
+++ b/ethcore/src/block_queue.rs
@@ -28,7 +28,7 @@ use service::*;
 use client::BlockStatus;
 use util::panics::*;
 
-known_heap_size!(0, UnVerifiedBlock, VerifyingBlock, PreVerifiedBlock);
+known_heap_size!(0, UnverifiedBlock, VerifyingBlock, PreverifiedBlock);
 
 const MIN_MEM_LIMIT: usize = 16384;
 const MIN_QUEUE_LIMIT: usize = 512;
@@ -105,14 +105,14 @@ pub struct BlockQueue {
 	max_mem_use: usize,
 }
 
-struct UnVerifiedBlock {
+struct UnverifiedBlock {
 	header: Header,
 	bytes: Bytes,
 }
 
 struct VerifyingBlock {
 	hash: H256,
-	block: Option<PreVerifiedBlock>,
+	block: Option<PreverifiedBlock>,
 }
 
 struct QueueSignal {
@@ -134,8 +134,8 @@ impl QueueSignal {
 
 #[derive(Default)]
 struct Verification {
-	unverified: VecDeque<UnVerifiedBlock>,
-	verified: VecDeque<PreVerifiedBlock>,
+	unverified: VecDeque<UnverifiedBlock>,
+	verified: VecDeque<PreverifiedBlock>,
 	verifying: VecDeque<VerifyingBlock>,
 	bad: HashSet<H256>,
 }
@@ -244,7 +244,7 @@ impl BlockQueue {
 		}
 	}
 
-	fn drain_verifying(verifying: &mut VecDeque<VerifyingBlock>, verified: &mut VecDeque<PreVerifiedBlock>, bad: &mut HashSet<H256>) {
+	fn drain_verifying(verifying: &mut VecDeque<VerifyingBlock>, verified: &mut VecDeque<PreverifiedBlock>, bad: &mut HashSet<H256>) {
 		while !verifying.is_empty() && verifying.front().unwrap().block.is_some() {
 			let block = verifying.pop_front().unwrap().block.unwrap();
 			if bad.contains(&block.header.parent_hash) {
@@ -289,31 +289,31 @@ impl BlockQueue {
 		let header = BlockView::new(&bytes).header();
 		let h = header.hash();
 		if self.processing.read().unwrap().contains(&h) {
-			return Err(ImportError::AlreadyQueued);
+			return Err(x!(ImportError::AlreadyQueued));
 		}
 		{
 			let mut verification = self.verification.lock().unwrap();
 			if verification.bad.contains(&h) {
-				return Err(ImportError::Bad(None));
+				return Err(x!(ImportError::KnownBad));
 			}
 
 			if verification.bad.contains(&header.parent_hash) {
 				verification.bad.insert(h.clone());
-				return Err(ImportError::Bad(None));
+				return Err(x!(ImportError::KnownBad));
 			}
 		}
 
 		match verify_block_basic(&header, &bytes, self.engine.deref().deref()) {
 			Ok(()) => {
 				self.processing.write().unwrap().insert(h.clone());
-				self.verification.lock().unwrap().unverified.push_back(UnVerifiedBlock { header: header, bytes: bytes });
+				self.verification.lock().unwrap().unverified.push_back(UnverifiedBlock { header: header, bytes: bytes });
 				self.more_to_verify.notify_all();
 				Ok(h)
 			},
 			Err(err) => {
 				warn!(target: "client", "Stage 1 block verification failed for {}\nError: {:?}", BlockView::new(&bytes).header_view().sha3(), err);
 				self.verification.lock().unwrap().bad.insert(h.clone());
-				Err(From::from(err))
+				Err(err)
 			}
 		}
 	}
@@ -352,7 +352,7 @@ impl BlockQueue {
 	}
 
 	/// Removes up to `max` verified blocks from the queue
-	pub fn drain(&mut self, max: usize) -> Vec<PreVerifiedBlock> {
+	pub fn drain(&mut self, max: usize) -> Vec<PreverifiedBlock> {
 		let mut verification = self.verification.lock().unwrap();
 		let count = min(max, verification.verified.len());
 		let mut result = Vec::with_capacity(count);
diff --git a/ethcore/src/client.rs b/ethcore/src/client.rs
index f634579ad..d4fdb66c4 100644
--- a/ethcore/src/client.rs
+++ b/ethcore/src/client.rs
@@ -176,7 +176,7 @@ pub struct ClientReport {
 
 impl ClientReport {
 	/// Alter internal reporting to reflect the additional `block` has been processed.
-	pub fn accrue_block(&mut self, block: &PreVerifiedBlock) {
+	pub fn accrue_block(&mut self, block: &PreverifiedBlock) {
 		self.blocks_imported += 1;
 		self.transactions_applied += block.transactions.len();
 		self.gas_processed = self.gas_processed + block.header.gas_used;
@@ -257,7 +257,7 @@ impl Client {
 		last_hashes
 	}
 
-	fn check_and_close_block(&self, block: &PreVerifiedBlock) -> Result<ClosedBlock, ()> {
+	fn check_and_close_block(&self, block: &PreverifiedBlock) -> Result<ClosedBlock, ()> {
 		let engine = self.engine.deref().deref();
 		let header = &block.header;
 
@@ -433,6 +433,28 @@ impl Client {
 
 	/// Grab the `ClosedBlock` that we want to be sealed. Comes as a mutex that you have to lock.
 	pub fn sealing_block(&self) -> &Mutex<Option<ClosedBlock>> { &self.sealing_block }
+
+	/// Submit `seal` as a valid solution for the header of `pow_hash`.
+	pub fn submit_seal(&self, pow_hash: H256, seal: Vec<Bytes>) -> Result<(), Error> {
+		let mut maybe_b = self.sealing_block.lock().unwrap();
+		match *maybe_b {
+			Some(ref b) if b.hash() == pow_hash => {}
+			_ => { return Err(Error::PowHashInvalid); }
+		}
+
+		let b = maybe_b.take();
+		match b.unwrap().try_seal(self.engine.deref().deref(), seal) {
+			Err(old) => {
+				*maybe_b = Some(old);
+				Err(Error::PowInvalid)
+			}
+			Ok(sealed) => {
+				// TODO: commit DB from `sealed.drain` and make a VerifiedBlock to skip running the transactions twice.
+				try!(self.import_block(sealed.rlp_bytes()));
+				Ok(())
+			}
+		}
+	}
 }
 
 // TODO: need MinerService MinerIoHandler
@@ -509,12 +531,14 @@ impl BlockChainClient for Client {
 	}
 
 	fn import_block(&self, bytes: Bytes) -> ImportResult {
-		let header = BlockView::new(&bytes).header();
-		if self.chain.read().unwrap().is_known(&header.hash()) {
-			return Err(ImportError::AlreadyInChain);
-		}
-		if self.block_status(BlockId::Hash(header.parent_hash)) == BlockStatus::Unknown {
-			return Err(ImportError::UnknownParent);
+		{
+			let header = BlockView::new(&bytes).header_view();
+			if self.chain.read().unwrap().is_known(&header.sha3()) {
+				return Err(x!(ImportError::AlreadyInChain));
+			}
+			if self.block_status(BlockId::Hash(header.parent_hash())) == BlockStatus::Unknown {
+				return Err(x!(BlockError::UnknownParent(header.parent_hash())));
+			}
 		}
 		self.block_queue.write().unwrap().import_block(bytes)
 	}
diff --git a/ethcore/src/engine.rs b/ethcore/src/engine.rs
index f86c943ee..c57be3cdb 100644
--- a/ethcore/src/engine.rs
+++ b/ethcore/src/engine.rs
@@ -30,8 +30,6 @@ pub trait Engine : Sync + Send {
 
 	/// The number of additional header fields required for this engine.
 	fn seal_fields(&self) -> usize { 0 }
-	/// Default values of the additional fields RLP-encoded in a raw (non-list) harness.
-	fn seal_rlp(&self) -> Bytes { vec![] }
 
 	/// Additional engine-specific information for the user/developer concerning `header`.
 	fn extra_info(&self, _header: &Header) -> HashMap<String, String> { HashMap::new() }
diff --git a/ethcore/src/error.rs b/ethcore/src/error.rs
index f75f338bf..824d8da90 100644
--- a/ethcore/src/error.rs
+++ b/ethcore/src/error.rs
@@ -131,25 +131,14 @@ pub enum BlockError {
 #[derive(Debug)]
 /// Import to the block queue result
 pub enum ImportError {
-	/// Bad block detected
-	Bad(Option<Error>),
-	/// Already in the block chain
+	/// Already in the block chain.
 	AlreadyInChain,
-	/// Already in the block queue
+	/// Already in the block queue.
 	AlreadyQueued,
-	/// Unknown parent
-	UnknownParent,
+	/// Already marked as bad from a previous import (could mean parent is bad).
+	KnownBad,
 }
 
-impl From<Error> for ImportError {
-	fn from(err: Error) -> ImportError {
-		ImportError::Bad(Some(err))
-	}
-}
-
-/// Result of import block operation.
-pub type ImportResult = Result<H256, ImportError>;
-
 #[derive(Debug)]
 /// General error type which should be capable of representing all errors in ethcore.
 pub enum Error {
@@ -163,14 +152,29 @@ pub enum Error {
 	Execution(ExecutionError),
 	/// Error concerning transaction processing.
 	Transaction(TransactionError),
+	/// Error concerning block import.
+	Import(ImportError),
+	/// PoW hash is invalid or out of date.
+	PowHashInvalid,
+	/// The value of the nonce or mishash is invalid.
+	PowInvalid,
 }
 
+/// Result of import block operation.
+pub type ImportResult = Result<H256, Error>;
+
 impl From<TransactionError> for Error {
 	fn from(err: TransactionError) -> Error {
 		Error::Transaction(err)
 	}
 }
 
+impl From<ImportError> for Error {
+	fn from(err: ImportError) -> Error {
+		Error::Import(err)
+	}
+}
+
 impl From<BlockError> for Error {
 	fn from(err: BlockError) -> Error {
 		Error::Block(err)
diff --git a/ethcore/src/ethereum/ethash.rs b/ethcore/src/ethereum/ethash.rs
index 4f1ef1ce3..d26a7e2af 100644
--- a/ethcore/src/ethereum/ethash.rs
+++ b/ethcore/src/ethereum/ethash.rs
@@ -74,8 +74,6 @@ impl Engine for Ethash {
 	fn version(&self) -> SemanticVersion { SemanticVersion::new(1, 0, 0) }
 	// Two fields - mix
 	fn seal_fields(&self) -> usize { 2 }
-	// Two empty data items in RLP.
-	fn seal_rlp(&self) -> Bytes { encode(&H64::new()).to_vec() }
 
 	/// Additional engine-specific information for the user/developer concerning `header`.
 	fn extra_info(&self, _header: &Header) -> HashMap<String, String> { HashMap::new() }
@@ -261,12 +259,15 @@ impl Ethash {
 }
 
 impl Header {
-	fn nonce(&self) -> H64 {
+	pub fn nonce(&self) -> H64 {
 		decode(&self.seal()[1])
 	}
-	fn mix_hash(&self) -> H256 {
+	pub fn mix_hash(&self) -> H256 {
 		decode(&self.seal()[0])
 	}
+	pub fn set_nonce_and_mix_hash(&mut self, nonce: &H64, mix_hash: &H256) {
+		self.seal = vec![encode(mix_hash).to_vec(), encode(nonce).to_vec()];
+	}
 }
 
 #[cfg(test)]
diff --git a/ethcore/src/verification.rs b/ethcore/src/verification.rs
index ad5efd24a..f52e2e1e4 100644
--- a/ethcore/src/verification.rs
+++ b/ethcore/src/verification.rs
@@ -26,7 +26,7 @@ use engine::Engine;
 use blockchain::*;
 
 /// Preprocessed block data gathered in `verify_block_unordered` call
-pub struct PreVerifiedBlock {
+pub struct PreverifiedBlock {
 	/// Populated block header
 	pub header: Header,
 	/// Populated block transactions
@@ -55,8 +55,8 @@ pub fn verify_block_basic(header: &Header, bytes: &[u8], engine: &Engine) -> Res
 
 /// Phase 2 verification. Perform costly checks such as transaction signatures and block nonce for ethash.
 /// Still operates on a individual block
-/// Returns a PreVerifiedBlock structure populated with transactions
-pub fn verify_block_unordered(header: Header, bytes: Bytes, engine: &Engine) -> Result<PreVerifiedBlock, Error> {
+/// Returns a PreverifiedBlock structure populated with transactions
+pub fn verify_block_unordered(header: Header, bytes: Bytes, engine: &Engine) -> Result<PreverifiedBlock, Error> {
 	try!(engine.verify_block_unordered(&header, Some(&bytes)));
 	for u in Rlp::new(&bytes).at(2).iter().map(|rlp| rlp.as_val::<Header>()) {
 		try!(engine.verify_block_unordered(&u, None));
@@ -70,7 +70,7 @@ pub fn verify_block_unordered(header: Header, bytes: Bytes, engine: &Engine) ->
 			transactions.push(t);
 		}
 	}
-	Ok(PreVerifiedBlock {
+	Ok(PreverifiedBlock {
 		header: header,
 		transactions: transactions,
 		bytes: bytes,
diff --git a/rpc/src/v1/impls/eth.rs b/rpc/src/v1/impls/eth.rs
index 5791b7418..1b5c4739c 100644
--- a/rpc/src/v1/impls/eth.rs
+++ b/rpc/src/v1/impls/eth.rs
@@ -21,6 +21,7 @@ use jsonrpc_core::*;
 use util::hash::*;
 use util::uint::*;
 use util::sha3::*;
+use util::rlp::encode;
 use ethcore::client::*;
 use ethcore::block::{IsBlock};
 use ethcore::views::*;
@@ -221,10 +222,10 @@ impl Eth for EthClient {
 				let u = c.sealing_block().lock().unwrap();
 				match *u {
 					Some(ref b) => {
-						let current_hash = b.hash();
+						let pow_hash = b.hash();
 						let target = Ethash::difficulty_to_boundary(b.block().header().difficulty());
 						let seed_hash = get_seedhash(b.block().header().number());
-						to_value(&(current_hash, seed_hash, target))
+						to_value(&(pow_hash, seed_hash, target))
 					}
 					_ => Err(Error::invalid_params())
 				}
@@ -233,7 +234,13 @@ impl Eth for EthClient {
 		}
 	}
 
-//	fn submit_work(&self, _: Params) -> Result<Value, Error> { rpc_unimplemented!() }
+	fn submit_work(&self, params: Params) -> Result<Value, Error> {
+		from_params::<(H64, H256, H256)>(params).and_then(|(nonce, pow_hash, mix_hash)| {
+			let c = take_weak!(self.client);
+			let seal = vec![encode(&mix_hash).to_vec(), encode(&nonce).to_vec()];
+			to_value(&c.submit_seal(pow_hash, seal).is_ok())
+		})
+	}
 
 //	fn submit_hashrate(&self, _: Params) -> Result<Value, Error> { rpc_unimplemented!() }
 }
diff --git a/sync/src/chain.rs b/sync/src/chain.rs
index 6a7add27f..4b8065bc7 100644
--- a/sync/src/chain.rs
+++ b/sync/src/chain.rs
@@ -477,19 +477,19 @@ impl ChainSync {
 		// TODO: Decompose block and add to self.headers and self.bodies instead
 		if header.number == From::from(self.current_base_block() + 1) {
 			match io.chain().import_block(block_rlp.as_raw().to_vec()) {
-				Err(ImportError::AlreadyInChain) => {
+				Err(Error::Import(ImportError::AlreadyInChain)) => {
 					trace!(target: "sync", "New block already in chain {:?}", h);
 				},
-				Err(ImportError::AlreadyQueued) => {
+				Err(Error::Import(ImportError::AlreadyQueued)) => {
 					trace!(target: "sync", "New block already queued {:?}", h);
 				},
 				Ok(_) => {
 					self.last_imported_block = Some(header.number);
 					trace!(target: "sync", "New block queued {:?}", h);
 				},
-				Err(ImportError::UnknownParent) => {
+				Err(Error::Block(BlockError::UnknownParent(p))) => {
 					unknown = true;
-					trace!(target: "sync", "New block with unknown parent {:?}", h);
+					trace!(target: "sync", "New block with unknown parent ({:?}) {:?}", p, h);
 				},
 				Err(e) => {
 					debug!(target: "sync", "Bad new block {:?} : {:?}", h, e);
@@ -781,12 +781,12 @@ impl ChainSync {
 				}
 
 				match io.chain().import_block(block_rlp.out()) {
-					Err(ImportError::AlreadyInChain) => {
+					Err(Error::Import(ImportError::AlreadyInChain)) => {
 						trace!(target: "sync", "Block already in chain {:?}", h);
 						self.last_imported_block = Some(headers.0 + i as BlockNumber);
 						self.last_imported_hash = Some(h.clone());
 					},
-					Err(ImportError::AlreadyQueued) => {
+					Err(Error::Import(ImportError::AlreadyQueued)) => {
 						trace!(target: "sync", "Block already queued {:?}", h);
 						self.last_imported_block = Some(headers.0 + i as BlockNumber);
 						self.last_imported_hash = Some(h.clone());

From 2266d74c2aec90949803e8721e20136ae5e79d08 Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Tue, 1 Mar 2016 01:15:00 +0100
Subject: [PATCH 05/22] Fix JSONRPC I/O.

---
 Cargo.lock                     |  1 +
 ethcore/src/ethereum/ethash.rs | 10 ++++++++++
 rpc/Cargo.toml                 |  1 +
 rpc/src/v1/impls/eth.rs        | 15 +++++++++++----
 4 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 9c225dbbe..b8a92fc3d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -209,6 +209,7 @@ dependencies = [
  "ethsync 0.9.99",
  "jsonrpc-core 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "jsonrpc-http-server 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.18 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_codegen 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/ethcore/src/ethereum/ethash.rs b/ethcore/src/ethereum/ethash.rs
index d26a7e2af..6dabe558f 100644
--- a/ethcore/src/ethereum/ethash.rs
+++ b/ethcore/src/ethereum/ethash.rs
@@ -249,6 +249,11 @@ impl Ethash {
 		x!(U256::from((U512::one() << 256) / x!(difficulty)))
 	}
 
+	/// Given the `block_number`, determine the seed hash for Ethash.
+	pub fn get_seedhash(number: BlockNumber) -> H256 {
+		Self::from_ethash(ethash::get_seedhash(number))
+	}
+
 	fn to_ethash(hash: H256) -> EH256 {
 		unsafe { mem::transmute(hash) }
 	}
@@ -259,12 +264,17 @@ impl Ethash {
 }
 
 impl Header {
+	/// Get the none field of the header.
 	pub fn nonce(&self) -> H64 {
 		decode(&self.seal()[1])
 	}
+
+	/// Get the mix hash field of the header.
 	pub fn mix_hash(&self) -> H256 {
 		decode(&self.seal()[0])
 	}
+
+	/// Set the nonce and mix hash fields of the header.
 	pub fn set_nonce_and_mix_hash(&mut self, nonce: &H64, mix_hash: &H256) {
 		self.seal = vec![encode(mix_hash).to_vec(), encode(nonce).to_vec()];
 	}
diff --git a/rpc/Cargo.toml b/rpc/Cargo.toml
index c38684643..086fb19c1 100644
--- a/rpc/Cargo.toml
+++ b/rpc/Cargo.toml
@@ -9,6 +9,7 @@ build = "build.rs"
 [lib]
 
 [dependencies]
+log = "0.3"
 serde = "0.7.0"
 serde_json = "0.7.0"
 jsonrpc-core = "1.2"
diff --git a/rpc/src/v1/impls/eth.rs b/rpc/src/v1/impls/eth.rs
index 1b5c4739c..b26f38440 100644
--- a/rpc/src/v1/impls/eth.rs
+++ b/rpc/src/v1/impls/eth.rs
@@ -25,8 +25,7 @@ use util::rlp::encode;
 use ethcore::client::*;
 use ethcore::block::{IsBlock};
 use ethcore::views::*;
-extern crate ethash;
-use self::ethash::get_seedhash;
+//#[macro_use] extern crate log;
 use ethcore::ethereum::Ethash;
 use ethcore::ethereum::denominations::shannon;
 use v1::traits::{Eth, EthFilter};
@@ -216,6 +215,7 @@ impl Eth for EthClient {
 	}
 
 	fn work(&self, params: Params) -> Result<Value, Error> {
+		println!("Work wanted: {:?}", params);
 		match params {
 			Params::None => {
 				let c = take_weak!(self.client);
@@ -224,7 +224,7 @@ impl Eth for EthClient {
 					Some(ref b) => {
 						let pow_hash = b.hash();
 						let target = Ethash::difficulty_to_boundary(b.block().header().difficulty());
-						let seed_hash = get_seedhash(b.block().header().number());
+						let seed_hash = Ethash::get_seedhash(b.block().header().number());
 						to_value(&(pow_hash, seed_hash, target))
 					}
 					_ => Err(Error::invalid_params())
@@ -235,6 +235,7 @@ impl Eth for EthClient {
 	}
 
 	fn submit_work(&self, params: Params) -> Result<Value, Error> {
+		println!("Work submission: {:?}", params);
 		from_params::<(H64, H256, H256)>(params).and_then(|(nonce, pow_hash, mix_hash)| {
 			let c = take_weak!(self.client);
 			let seal = vec![encode(&mix_hash).to_vec(), encode(&nonce).to_vec()];
@@ -242,7 +243,13 @@ impl Eth for EthClient {
 		})
 	}
 
-//	fn submit_hashrate(&self, _: Params) -> Result<Value, Error> { rpc_unimplemented!() }
+	fn submit_hashrate(&self, params: Params) -> Result<Value, Error> {
+		println!("Hashrate submission: {:?}", params);
+		from_params::<(Index, H256)>(params).and_then(|(rate, id)| {
+			println!("Miner {} reports a hash rate of {} H/s", id, rate.value());
+			to_value(&true)
+		})
+	}
 }
 
 /// Eth filter rpc implementation.

From 5ccb172e73a1bf0b7b16545c0560184beef8d9d8 Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Tue, 1 Mar 2016 01:52:22 +0100
Subject: [PATCH 06/22] Hashrate now reported correctly.

---
 ethcore/src/client.rs   |  4 ++--
 rpc/src/v1/impls/eth.rs | 16 +++++++++-------
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/ethcore/src/client.rs b/ethcore/src/client.rs
index d4fdb66c4..c5aa987f6 100644
--- a/ethcore/src/client.rs
+++ b/ethcore/src/client.rs
@@ -417,7 +417,7 @@ impl Client {
 	/// New chain head event.
 	pub fn new_chain_head(&self) {
 		let h = self.chain.read().unwrap().best_block_hash();
-		info!("New best block: #{}: {}", self.chain.read().unwrap().best_block_number(), h);
+		debug!("New best block: #{}: {}", self.chain.read().unwrap().best_block_number(), h);
 		let b = OpenBlock::new(
 			self.engine.deref().deref(),
 			self.state_db.lock().unwrap().clone(),
@@ -427,7 +427,7 @@ impl Client {
 			b"Parity".to_vec()
 		);
 		let b = b.close();
-		info!("Sealed: hash={}, diff={}, number={}", b.hash(), b.block().header().difficulty(), b.block().header().number());
+		debug!("Sealing: hash={}, diff={}, number={}", b.hash(), b.block().header().difficulty(), b.block().header().number());
 		*self.sealing_block.lock().unwrap() = Some(b);
 	}
 
diff --git a/rpc/src/v1/impls/eth.rs b/rpc/src/v1/impls/eth.rs
index b26f38440..f96d69ce7 100644
--- a/rpc/src/v1/impls/eth.rs
+++ b/rpc/src/v1/impls/eth.rs
@@ -15,12 +15,12 @@
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
 //! Eth rpc implementation.
-use std::sync::{Arc, Weak};
 use ethsync::{EthSync, SyncState};
 use jsonrpc_core::*;
 use util::hash::*;
 use util::uint::*;
 use util::sha3::*;
+use util::standard::{RwLock, HashMap, Arc, Weak};
 use util::rlp::encode;
 use ethcore::client::*;
 use ethcore::block::{IsBlock};
@@ -34,7 +34,8 @@ use v1::types::{Block, BlockTransactions, BlockNumber, Bytes, SyncStatus, SyncIn
 /// Eth rpc implementation.
 pub struct EthClient {
 	client: Weak<Client>,
-	sync: Weak<EthSync>
+	sync: Weak<EthSync>,
+	hashrates: RwLock<HashMap<H256, u64>>,
 }
 
 impl EthClient {
@@ -42,7 +43,8 @@ impl EthClient {
 	pub fn new(client: &Arc<Client>, sync: &Arc<EthSync>) -> Self {
 		EthClient {
 			client: Arc::downgrade(client),
-			sync: Arc::downgrade(sync)
+			sync: Arc::downgrade(sync),
+			hashrates: RwLock::new(HashMap::new()),
 		}
 	}
 
@@ -137,7 +139,7 @@ impl Eth for EthClient {
 	// TODO: return real hashrate once we have mining
 	fn hashrate(&self, params: Params) -> Result<Value, Error> {
 		match params {
-			Params::None => to_value(&U256::zero()),
+			Params::None => to_value(&self.hashrates.read().unwrap().iter().fold(0u64, |sum, (_, v)| sum + v)),
 			_ => Err(Error::invalid_params())
 		}
 	}
@@ -215,7 +217,6 @@ impl Eth for EthClient {
 	}
 
 	fn work(&self, params: Params) -> Result<Value, Error> {
-		println!("Work wanted: {:?}", params);
 		match params {
 			Params::None => {
 				let c = take_weak!(self.client);
@@ -235,6 +236,7 @@ impl Eth for EthClient {
 	}
 
 	fn submit_work(&self, params: Params) -> Result<Value, Error> {
+		// TODO: println! should be debug!
 		println!("Work submission: {:?}", params);
 		from_params::<(H64, H256, H256)>(params).and_then(|(nonce, pow_hash, mix_hash)| {
 			let c = take_weak!(self.client);
@@ -244,9 +246,9 @@ impl Eth for EthClient {
 	}
 
 	fn submit_hashrate(&self, params: Params) -> Result<Value, Error> {
-		println!("Hashrate submission: {:?}", params);
+		// TODO: Index should be U256.
 		from_params::<(Index, H256)>(params).and_then(|(rate, id)| {
-			println!("Miner {} reports a hash rate of {} H/s", id, rate.value());
+			self.hashrates.write().unwrap().insert(id, rate.value() as u64);
 			to_value(&true)
 		})
 	}

From 1eca9acffb2f952678d7135f059139b650eec289 Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Tue, 1 Mar 2016 02:33:41 +0100
Subject: [PATCH 07/22] Fix is_mining.

---
 rpc/src/v1/impls/eth.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rpc/src/v1/impls/eth.rs b/rpc/src/v1/impls/eth.rs
index f96d69ce7..24ecbe5f1 100644
--- a/rpc/src/v1/impls/eth.rs
+++ b/rpc/src/v1/impls/eth.rs
@@ -131,7 +131,7 @@ impl Eth for EthClient {
 	// TODO: return real value of mining once it's implemented.
 	fn is_mining(&self, params: Params) -> Result<Value, Error> {
 		match params {
-			Params::None => Ok(Value::Bool(false)),
+			Params::None => to_value(&!self.hashrates.read().unwrap().is_empty()),
 			_ => Err(Error::invalid_params())
 		}
 	}

From 48df869202571360b4554544bf4400f19a0236d3 Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Tue, 1 Mar 2016 16:58:14 +0100
Subject: [PATCH 08/22] --author and --extra-data options. Fixed null
 parent-hash.

---
 ethcore/src/block.rs    | 12 +++++++---
 ethcore/src/client.rs   | 50 +++++++++++++++++++++++++++++++++--------
 ethcore/src/header.rs   | 10 ++++++---
 parity/main.rs          | 20 +++++++++++++++++
 rpc/src/v1/impls/eth.rs |  6 ++---
 util/src/misc.rs        | 15 +++++++++++++
 6 files changed, 95 insertions(+), 18 deletions(-)

diff --git a/ethcore/src/block.rs b/ethcore/src/block.rs
index f72c2f800..16d3e2216 100644
--- a/ethcore/src/block.rs
+++ b/ethcore/src/block.rs
@@ -182,6 +182,7 @@ impl<'x> OpenBlock<'x> {
 		r.block.base.header.set_author(author);
 		r.block.base.header.set_extra_data(extra_data);
 		r.block.base.header.set_timestamp_now(parent.timestamp());
+		r.block.base.header.set_parent_hash(parent.hash());
 
 		engine.populate_from_parent(&mut r.block.base.header, parent);
 		engine.on_new_block(&mut r.block);
@@ -308,10 +309,15 @@ impl ClosedBlock {
 	pub fn try_seal(self, engine: &Engine, seal: Vec<Bytes>) -> Result<SealedBlock, ClosedBlock> {
 		let mut s = self;
 		s.block.base.header.set_seal(seal);
-		match engine.verify_block_basic(&s.block.base.header, None).is_err() || engine.verify_block_unordered(&s.block.base.header, None).is_err() {
-			false => Err(s),
-			true => Ok(SealedBlock { block: s.block, uncle_bytes: s.uncle_bytes }),
+		if let Err(e) = engine.verify_block_basic(&s.block.base.header, None) {
+			debug!("Failed to try_seal: {:?}", e);
+			return Err(s);
 		}
+		if let Err(e) = engine.verify_block_unordered(&s.block.base.header, None) {
+			debug!("Failed to try_seal: {:?}", e);
+			return Err(s);
+		}
+		Ok(SealedBlock { block: s.block, uncle_bytes: s.uncle_bytes })
 	}
 
 	/// Drop this object and return the underlieing database.
diff --git a/ethcore/src/client.rs b/ethcore/src/client.rs
index c5aa987f6..de875348a 100644
--- a/ethcore/src/client.rs
+++ b/ethcore/src/client.rs
@@ -196,6 +196,8 @@ pub struct Client {
 
 	// for sealing...
 	sealing_block: Mutex<Option<ClosedBlock>>,
+	author: RwLock<Address>,
+	extra_data: RwLock<Bytes>,
 }
 
 const HISTORY: u64 = 1000;
@@ -233,6 +235,8 @@ impl Client {
 			import_lock: Mutex::new(()),
 			panic_handler: panic_handler,
 			sealing_block: Mutex::new(None),
+			author: RwLock::new(Address::new()),
+			extra_data: RwLock::new(Vec::new()),
 		}))
 	}
 
@@ -364,7 +368,7 @@ impl Client {
 		}
 
 		if self.chain_info().best_block_hash != original_best {
-			self.new_chain_head();
+			self.prepare_sealing();
 		}
 
 		imported
@@ -414,27 +418,55 @@ impl Client {
 		}
 	}
 
-	/// New chain head event.
-	pub fn new_chain_head(&self) {
+	/// Set the author that we will seal blocks as.
+	pub fn author(&self) -> Address {
+		self.author.read().unwrap().clone()
+	}
+
+	/// Set the author that we will seal blocks as.
+	pub fn set_author(&self, author: Address) {
+		*self.author.write().unwrap() = author;
+	}
+
+	/// Set the extra_data that we will seal blocks wuth.
+	pub fn extra_data(&self) -> Bytes {
+		self.extra_data.read().unwrap().clone()
+	}
+
+	/// Set the extra_data that we will seal blocks with.
+	pub fn set_extra_data(&self, extra_data: Bytes) {
+		*self.extra_data.write().unwrap() = extra_data;
+	}
+
+	/// New chain head event. Restart mining operation.
+	pub fn prepare_sealing(&self) {
 		let h = self.chain.read().unwrap().best_block_hash();
-		debug!("New best block: #{}: {}", self.chain.read().unwrap().best_block_number(), h);
 		let b = OpenBlock::new(
 			self.engine.deref().deref(),
 			self.state_db.lock().unwrap().clone(),
 			match self.chain.read().unwrap().block_header(&h) { Some(ref x) => x, None => {return;} },
-			self.build_last_hashes(h.clone()),
-			x!("0037a6b811ffeb6e072da21179d11b1406371c63"),
-			b"Parity".to_vec()
+			self.build_last_hashes(h),
+			self.author(),
+			self.extra_data()
 		);
+		// TODO: push uncles.
+		// TODO: push transactions.
 		let b = b.close();
-		debug!("Sealing: hash={}, diff={}, number={}", b.hash(), b.block().header().difficulty(), b.block().header().number());
+		trace!("Sealing: number={}, hash={}, diff={}", b.hash(), b.block().header().difficulty(), b.block().header().number());
+		debug!("Header: {:?}", b.block().header());
 		*self.sealing_block.lock().unwrap() = Some(b);
 	}
 
 	/// Grab the `ClosedBlock` that we want to be sealed. Comes as a mutex that you have to lock.
-	pub fn sealing_block(&self) -> &Mutex<Option<ClosedBlock>> { &self.sealing_block }
+	pub fn sealing_block(&self) -> &Mutex<Option<ClosedBlock>> {
+		if self.sealing_block.lock().unwrap().is_none() {
+			self.prepare_sealing();
+		}
+		&self.sealing_block
+	}
 
 	/// Submit `seal` as a valid solution for the header of `pow_hash`.
+	/// Will check the seal, but not actually insert the block into the chain.
 	pub fn submit_seal(&self, pow_hash: H256, seal: Vec<Bytes>) -> Result<(), Error> {
 		let mut maybe_b = self.sealing_block.lock().unwrap();
 		match *maybe_b {
diff --git a/ethcore/src/header.rs b/ethcore/src/header.rs
index 3db0be5ff..cc02d84db 100644
--- a/ethcore/src/header.rs
+++ b/ethcore/src/header.rs
@@ -102,10 +102,12 @@ impl Header {
 		Self::default()
 	}
 
-	/// Get the number field of the header.
-	pub fn number(&self) -> BlockNumber { self.number }
+	/// Get the parent_hash field of the header.
+	pub fn parent_hash(&self) -> &H256 { &self.parent_hash }
 	/// Get the timestamp field of the header.
 	pub fn timestamp(&self) -> u64 { self.timestamp }
+	/// Get the number field of the header.
+	pub fn number(&self) -> BlockNumber { self.number }
 	/// Get the author field of the header.
 	pub fn author(&self) -> &Address { &self.author }
 
@@ -127,11 +129,13 @@ impl Header {
 	// TODO: seal_at, set_seal_at &c.
 
 	/// Set the number field of the header.
-	pub fn set_number(&mut self, a: BlockNumber) { self.number = a; self.note_dirty(); }
+	pub fn set_parent_hash(&mut self, a: H256) { self.parent_hash = a; self.note_dirty(); }
 	/// Set the timestamp field of the header.
 	pub fn set_timestamp(&mut self, a: u64) { self.timestamp = a; self.note_dirty(); }
 	/// Set the timestamp field of the header to the current time.
 	pub fn set_timestamp_now(&mut self, but_later_than: u64) { self.timestamp = max(now_utc().to_timespec().sec as u64, but_later_than + 1); self.note_dirty(); }
+	/// Set the number field of the header.
+	pub fn set_number(&mut self, a: BlockNumber) { self.number = a; self.note_dirty(); }
 	/// Set the author field of the header.
 	pub fn set_author(&mut self, a: Address) { if a != self.author { self.author = a; self.note_dirty(); } }
 
diff --git a/parity/main.rs b/parity/main.rs
index 7241a2ac4..b991f36cd 100644
--- a/parity/main.rs
+++ b/parity/main.rs
@@ -85,6 +85,10 @@ Options:
   --jsonrpc-url URL        Specify URL for JSON-RPC API server [default: 127.0.0.1:8545].
   --jsonrpc-cors URL       Specify CORS header for JSON-RPC API responses [default: null].
 
+  --author ADDRESS         Specify the block author (aka "coinbase") address for sending block rewards
+                           from sealed blocks [default: 0037a6b811ffeb6e072da21179d11b1406371c63].
+  --extra-data STRING      Specify a custom extra-data for authored blocks, no more than 32 characters.
+
   -l --logging LOGGING     Specify the logging level.
   -v --version             Show information about version.
   -h --help                Show this screen.
@@ -114,6 +118,8 @@ struct Args {
 	flag_jsonrpc_cors: String,
 	flag_logging: Option<String>,
 	flag_version: bool,
+	flag_author: String,
+	flag_extra_data: Option<String>,
 }
 
 fn setup_log(init: &Option<String>) {
@@ -196,6 +202,18 @@ impl Configuration {
 		self.args.flag_db_path.replace("$HOME", env::home_dir().unwrap().to_str().unwrap())
 	}
 
+	fn author(&self) -> Address {
+		Address::from_str(&self.args.flag_author).unwrap_or_else(|_| die!("{}: Invalid address for --author. Must be 40 hex characters, without the 0x at the beginning.", self.args.flag_author))
+	}
+
+	fn extra_data(&self) -> Bytes {
+		match self.args.flag_extra_data {
+			Some(ref x) if x.len() <= 32 => x.as_bytes().to_owned(),
+			None => version_data(),
+			Some(ref x) => { die!("{}: Extra data must be at most 32 characters.", x); }
+		}
+	}
+
 	fn _keys_path(&self) -> String {
 		self.args.flag_keys_path.replace("$HOME", env::home_dir().unwrap().to_str().unwrap())
 	}
@@ -296,6 +314,8 @@ impl Configuration {
 		client_config.queue.max_mem_use = self.args.flag_queue_max_size;
 		let mut service = ClientService::start(client_config, spec, net_settings, &Path::new(&self.path())).unwrap();
 		let client = service.client().clone();
+		client.set_author(self.author());
+		client.set_extra_data(self.extra_data());
 
 		// Sync
 		let sync = EthSync::register(service.network(), sync_config, client);
diff --git a/rpc/src/v1/impls/eth.rs b/rpc/src/v1/impls/eth.rs
index 24ecbe5f1..a7583ddf7 100644
--- a/rpc/src/v1/impls/eth.rs
+++ b/rpc/src/v1/impls/eth.rs
@@ -236,12 +236,12 @@ impl Eth for EthClient {
 	}
 
 	fn submit_work(&self, params: Params) -> Result<Value, Error> {
-		// TODO: println! should be debug!
-		println!("Work submission: {:?}", params);
 		from_params::<(H64, H256, H256)>(params).and_then(|(nonce, pow_hash, mix_hash)| {
+//			trace!("Decoded: nonce={}, pow_hash={}, mix_hash={}", nonce, pow_hash, mix_hash);
 			let c = take_weak!(self.client);
 			let seal = vec![encode(&mix_hash).to_vec(), encode(&nonce).to_vec()];
-			to_value(&c.submit_seal(pow_hash, seal).is_ok())
+			let r = c.submit_seal(pow_hash, seal);
+			to_value(&r.is_ok())
 		})
 	}
 
diff --git a/util/src/misc.rs b/util/src/misc.rs
index 35e1f3a75..d9f52fd71 100644
--- a/util/src/misc.rs
+++ b/util/src/misc.rs
@@ -18,6 +18,7 @@
 
 use std::fs::File;
 use common::*;
+use rlp::{Stream, RlpStream};
 use target_info::Target;
 use rustc_version;
 
@@ -70,4 +71,18 @@ pub fn contents(name: &str) -> Result<Bytes, UtilError> {
 /// Get the standard version string for this software.
 pub fn version() -> String {
 	format!("Parity//v{}-{}-{}/{}-{}-{}/rustc{}", env!("CARGO_PKG_VERSION"), short_sha(), commit_date().replace("-", ""), Target::arch(), Target::os(), Target::env(), rustc_version::version())
+}
+
+/// Get the standard version data for this software.
+pub fn version_data() -> Bytes {
+	let mut s = RlpStream::new_list(4);
+	let v =
+		(u32::from_str(env!("CARGO_PKG_VERSION_MAJOR")).unwrap() << 16) +
+		(u32::from_str(env!("CARGO_PKG_VERSION_MINOR")).unwrap() << 8) +
+		u32::from_str(env!("CARGO_PKG_VERSION_PATCH")).unwrap();
+	s.append(&v);
+	s.append(&"Parity");
+	s.append(&format!("rustc{}", rustc_version::version()));
+	s.append(&Target::os());
+	s.out()
 }
\ No newline at end of file

From a5c65b2a3d1aa9a13d680a7efb122be28e47f9b0 Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Tue, 1 Mar 2016 16:59:01 +0100
Subject: [PATCH 09/22] Reduce spam.

---
 ethcore/src/client.rs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/ethcore/src/client.rs b/ethcore/src/client.rs
index de875348a..e5d9f8fcf 100644
--- a/ethcore/src/client.rs
+++ b/ethcore/src/client.rs
@@ -453,7 +453,6 @@ impl Client {
 		// TODO: push transactions.
 		let b = b.close();
 		trace!("Sealing: number={}, hash={}, diff={}", b.hash(), b.block().header().difficulty(), b.block().header().number());
-		debug!("Header: {:?}", b.block().header());
 		*self.sealing_block.lock().unwrap() = Some(b);
 	}
 

From afc06050807867ee27a6830aaf15eee29042c60d Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Tue, 1 Mar 2016 17:23:44 +0100
Subject: [PATCH 10/22] Refactor engine to make it clear that we're actually
 checking the seal.

---
 ethcore/src/block.rs  | 11 +++--------
 ethcore/src/engine.rs |  7 +++++++
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/ethcore/src/block.rs b/ethcore/src/block.rs
index 16d3e2216..eb9d66124 100644
--- a/ethcore/src/block.rs
+++ b/ethcore/src/block.rs
@@ -309,15 +309,10 @@ impl ClosedBlock {
 	pub fn try_seal(self, engine: &Engine, seal: Vec<Bytes>) -> Result<SealedBlock, ClosedBlock> {
 		let mut s = self;
 		s.block.base.header.set_seal(seal);
-		if let Err(e) = engine.verify_block_basic(&s.block.base.header, None) {
-			debug!("Failed to try_seal: {:?}", e);
-			return Err(s);
+		match engine.verify_block_seal(&s.block.base.header) {
+			Err(_) => Err(s),
+			_ => Ok(SealedBlock { block: s.block, uncle_bytes: s.uncle_bytes }),
 		}
-		if let Err(e) = engine.verify_block_unordered(&s.block.base.header, None) {
-			debug!("Failed to try_seal: {:?}", e);
-			return Err(s);
-		}
-		Ok(SealedBlock { block: s.block, uncle_bytes: s.uncle_bytes })
 	}
 
 	/// Drop this object and return the underlieing database.
diff --git a/ethcore/src/engine.rs b/ethcore/src/engine.rs
index c57be3cdb..a05c78ff5 100644
--- a/ethcore/src/engine.rs
+++ b/ethcore/src/engine.rs
@@ -74,6 +74,13 @@ pub trait Engine : Sync + Send {
 	/// Verify a particular transaction is valid.
 	fn verify_transaction(&self, _t: &SignedTransaction, _header: &Header) -> Result<(), Error> { Ok(()) }
 
+	/// 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
+	/// methods are needed for an Engine, this may be overridden.
+	fn verify_block_seal(&self, header: &Header) -> Result<(), Error> {
+		self.verify_block_basic(header, None).and_then(|_| self.verify_block_unordered(header, None))
+	}
+
 	/// Don't forget to call Super::populateFromParent when subclassing & overriding.
 	// TODO: consider including State in the params.
 	fn populate_from_parent(&self, _header: &mut Header, _parent: &Header) {}

From 140711dd8ac6dbd55d3210bc6609711fae73f5a1 Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Tue, 1 Mar 2016 19:59:12 +0100
Subject: [PATCH 11/22] Fixups from review. Reduce size of default extra-data.
 Introduce find_uncle_headers.

---
 ethcore/src/block.rs                 |  2 +-
 ethcore/src/block_queue.rs           |  2 +-
 ethcore/src/blockchain/blockchain.rs |  6 ++++++
 ethcore/src/client.rs                | 13 ++++++++-----
 util/src/misc.rs                     |  4 ++--
 5 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/ethcore/src/block.rs b/ethcore/src/block.rs
index eb9d66124..582b8669a 100644
--- a/ethcore/src/block.rs
+++ b/ethcore/src/block.rs
@@ -404,7 +404,7 @@ mod tests {
 		let mut db_result = get_temp_journal_db();
 		let mut db = db_result.take();
 		engine.spec().ensure_db_good(&mut db);
-		let b = OpenBlock::new(engine.deref(), db, &genesis_header, vec![genesis_header.hash()], Address::zero(), vec![]).close().seal(vec![]).unwrap();
+		let b = OpenBlock::new(engine.deref(), db, &genesis_header, vec![genesis_header.hash()], Address::zero(), vec![]).close().seal(&engine, vec![]).unwrap();
 		let orig_bytes = b.rlp_bytes();
 		let orig_db = b.drain();
 
diff --git a/ethcore/src/block_queue.rs b/ethcore/src/block_queue.rs
index 143f53647..490a17995 100644
--- a/ethcore/src/block_queue.rs
+++ b/ethcore/src/block_queue.rs
@@ -455,7 +455,7 @@ mod tests {
 		match duplicate_import {
 			Err(e) => {
 				match e {
-					ImportError::AlreadyQueued => {},
+					Error::Import(ImportError::AlreadyQueued) => {},
 					_ => { panic!("must return AlreadyQueued error"); }
 				}
 			}
diff --git a/ethcore/src/blockchain/blockchain.rs b/ethcore/src/blockchain/blockchain.rs
index 0aba36a8e..88a6504ac 100644
--- a/ethcore/src/blockchain/blockchain.rs
+++ b/ethcore/src/blockchain/blockchain.rs
@@ -473,6 +473,12 @@ impl BlockChain {
 		self.extras_db.write(batch).unwrap();
 	}
 
+	/// Given a block's `parent`, find every block header which represents a valid uncle.
+	pub fn find_uncle_headers(&self, _parent: &H256) -> Vec<Header> {
+		// TODO
+		Vec::new()
+	}
+
 	/// Get inserted block info which is critical to preapre extras updates.
 	fn block_info(&self, block_bytes: &[u8]) -> BlockInfo {
 		let block = BlockView::new(block_bytes);
diff --git a/ethcore/src/client.rs b/ethcore/src/client.rs
index e5d9f8fcf..4b109c8a3 100644
--- a/ethcore/src/client.rs
+++ b/ethcore/src/client.rs
@@ -418,7 +418,7 @@ impl Client {
 		}
 	}
 
-	/// Set the author that we will seal blocks as.
+	/// Get the author that we will seal blocks as.
 	pub fn author(&self) -> Address {
 		self.author.read().unwrap().clone()
 	}
@@ -428,7 +428,7 @@ impl Client {
 		*self.author.write().unwrap() = author;
 	}
 
-	/// Set the extra_data that we will seal blocks wuth.
+	/// Get the extra_data that we will seal blocks wuth.
 	pub fn extra_data(&self) -> Bytes {
 		self.extra_data.read().unwrap().clone()
 	}
@@ -441,16 +441,19 @@ impl Client {
 	/// New chain head event. Restart mining operation.
 	pub fn prepare_sealing(&self) {
 		let h = self.chain.read().unwrap().best_block_hash();
-		let b = OpenBlock::new(
+		let mut b = OpenBlock::new(
 			self.engine.deref().deref(),
 			self.state_db.lock().unwrap().clone(),
 			match self.chain.read().unwrap().block_header(&h) { Some(ref x) => x, None => {return;} },
-			self.build_last_hashes(h),
+			self.build_last_hashes(h.clone()),
 			self.author(),
 			self.extra_data()
 		);
-		// TODO: push uncles.
+
+		self.chain.read().unwrap().find_uncle_headers(&h).into_iter().foreach(|h| { b.push_uncle(h).unwrap(); });
+
 		// TODO: push transactions.
+
 		let b = b.close();
 		trace!("Sealing: number={}, hash={}, diff={}", b.hash(), b.block().header().difficulty(), b.block().header().number());
 		*self.sealing_block.lock().unwrap() = Some(b);
diff --git a/util/src/misc.rs b/util/src/misc.rs
index d9f52fd71..6cd506d02 100644
--- a/util/src/misc.rs
+++ b/util/src/misc.rs
@@ -82,7 +82,7 @@ pub fn version_data() -> Bytes {
 		u32::from_str(env!("CARGO_PKG_VERSION_PATCH")).unwrap();
 	s.append(&v);
 	s.append(&"Parity");
-	s.append(&format!("rustc{}", rustc_version::version()));
-	s.append(&Target::os());
+	s.append(&format!("{}", rustc_version::version()));
+	s.append(&&Target::os()[0..2]);
 	s.out()
 }
\ No newline at end of file

From 628a53cceca9ad2b66d8c7510331ad23cc50134c Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Tue, 1 Mar 2016 20:02:59 +0100
Subject: [PATCH 12/22] Update tests. Fix our tests.

---
 ethcore/res/ethereum/tests | 2 +-
 ethcore/src/block.rs       | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/ethcore/res/ethereum/tests b/ethcore/res/ethereum/tests
index f32954b3d..99afe8f5a 160000
--- a/ethcore/res/ethereum/tests
+++ b/ethcore/res/ethereum/tests
@@ -1 +1 @@
-Subproject commit f32954b3ddb5af2dc3dc9ec6d9a28bee848fdf70
+Subproject commit 99afe8f5aad7bca5d0f1b1685390a4dea32d73c3
diff --git a/ethcore/src/block.rs b/ethcore/src/block.rs
index 582b8669a..0ca6e88be 100644
--- a/ethcore/src/block.rs
+++ b/ethcore/src/block.rs
@@ -404,7 +404,7 @@ mod tests {
 		let mut db_result = get_temp_journal_db();
 		let mut db = db_result.take();
 		engine.spec().ensure_db_good(&mut db);
-		let b = OpenBlock::new(engine.deref(), db, &genesis_header, vec![genesis_header.hash()], Address::zero(), vec![]).close().seal(&engine, vec![]).unwrap();
+		let b = OpenBlock::new(engine.deref(), db, &genesis_header, vec![genesis_header.hash()], Address::zero(), vec![]).close().seal(engine.deref(), vec![]).unwrap();
 		let orig_bytes = b.rlp_bytes();
 		let orig_db = b.drain();
 

From a21fda23a6e1c954f284bfff6cf7ac2797dbec4b Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Tue, 1 Mar 2016 20:14:28 +0100
Subject: [PATCH 13/22] Enable transition test.

---
 ethcore/src/json_tests/state.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ethcore/src/json_tests/state.rs b/ethcore/src/json_tests/state.rs
index b5f28444a..f6b5751a7 100644
--- a/ethcore/src/json_tests/state.rs
+++ b/ethcore/src/json_tests/state.rs
@@ -115,7 +115,7 @@ declare_test!{StateTests_stSolidityTest, "StateTests/stSolidityTest"}
 declare_test!{StateTests_stSpecialTest, "StateTests/stSpecialTest"}
 declare_test!{StateTests_stSystemOperationsTest, "StateTests/stSystemOperationsTest"}
 declare_test!{StateTests_stTransactionTest, "StateTests/stTransactionTest"}
-//declare_test!{StateTests_stTransitionTest, "StateTests/stTransitionTest"}
+declare_test!{StateTests_stTransitionTest, "StateTests/stTransitionTest"}
 declare_test!{StateTests_stWalletTest, "StateTests/stWalletTest"}
 
 

From 929f44fe4f62910fc0eba95257953b09ccd52b24 Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Wed, 2 Mar 2016 00:34:38 +0100
Subject: [PATCH 14/22] Tests for Client sealing.

---
 ethcore/src/engine.rs          |  9 +++++++--
 ethcore/src/ethereum/ethash.rs |  3 ++-
 ethcore/src/tests/client.rs    | 20 ++++++++++++++++++++
 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/ethcore/src/engine.rs b/ethcore/src/engine.rs
index a05c78ff5..6806fcce3 100644
--- a/ethcore/src/engine.rs
+++ b/ethcore/src/engine.rs
@@ -81,9 +81,14 @@ pub trait Engine : Sync + Send {
 		self.verify_block_basic(header, None).and_then(|_| self.verify_block_unordered(header, None))
 	}
 
-	/// Don't forget to call Super::populateFromParent when subclassing & overriding.
+	/// Don't forget to call Super::populate_from_parent when subclassing & overriding.
 	// TODO: consider including State in the params.
-	fn populate_from_parent(&self, _header: &mut Header, _parent: &Header) {}
+	fn populate_from_parent(&self, header: &mut Header, parent: &Header) {
+		header.parent_hash = parent.hash;
+		header.difficulty = parent.difficulty;
+		header.gas_limit = parent.gas_limit;
+		header.number = parent.number + 1;
+	}
 
 	// TODO: builtin contract routing - to do this properly, it will require removing the built-in configuration-reading logic
 	// from Spec into here and removing the Spec::builtins field.
diff --git a/ethcore/src/ethereum/ethash.rs b/ethcore/src/ethereum/ethash.rs
index 6dabe558f..bf0c1d188 100644
--- a/ethcore/src/ethereum/ethash.rs
+++ b/ethcore/src/ethereum/ethash.rs
@@ -144,7 +144,8 @@ impl Engine for Ethash {
 		let difficulty = Ethash::boundary_to_difficulty(&Ethash::from_ethash(quick_get_difficulty(
 			&Ethash::to_ethash(header.bare_hash()),
 			header.nonce().low_u64(),
-			&Ethash::to_ethash(header.mix_hash()) )));
+			&Ethash::to_ethash(header.mix_hash())
+		)));
 		if difficulty < header.difficulty {
 			return Err(From::from(BlockError::InvalidProofOfWork(OutOfBounds { min: Some(header.difficulty), max: None, found: difficulty })));
 		}
diff --git a/ethcore/src/tests/client.rs b/ethcore/src/tests/client.rs
index 83df81fa2..65c9d7358 100644
--- a/ethcore/src/tests/client.rs
+++ b/ethcore/src/tests/client.rs
@@ -15,6 +15,7 @@
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
 use client::{BlockChainClient, Client, ClientConfig, BlockId};
+use block::IsBlock;
 use tests::helpers::*;
 use common::*;
 use devtools::*;
@@ -106,3 +107,22 @@ fn can_collect_garbage() {
 	client.tick();
 	assert!(client.blockchain_cache_info().blocks < 100 * 1024);
 }
+
+#[test]
+fn can_mine() {
+	let dummy_blocks = get_good_dummy_block_seq(2);
+	let client_result = get_test_client_with_blocks(vec![dummy_blocks[0].clone()]);
+	let client = client_result.reference();
+	let b = client.sealing_block();
+	let pow_hash = {
+		let u = b.lock().unwrap();
+		match *u {
+			Some(ref b) => {
+				assert_eq!(*b.block().header().parent_hash(), BlockView::new(&dummy_blocks[0]).header_view().sha3());
+				b.hash()
+			}
+			None => { panic!(); }
+		}	
+	};
+	assert!(client.submit_seal(pow_hash, vec![]).is_ok());
+}
\ No newline at end of file

From 30c68204377742dbd7cda4bd5ac3114713de5cb1 Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Wed, 2 Mar 2016 00:52:18 +0100
Subject: [PATCH 15/22] Refactor and cleanup.

---
 ethcore/src/block.rs           | 9 +++++----
 ethcore/src/engine.rs          | 3 +--
 ethcore/src/ethereum/ethash.rs | 2 +-
 rpc/src/v1/impls/web3.rs       | 2 +-
 util/src/misc.rs               | 2 +-
 5 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/ethcore/src/block.rs b/ethcore/src/block.rs
index 0ca6e88be..f5788baba 100644
--- a/ethcore/src/block.rs
+++ b/ethcore/src/block.rs
@@ -178,11 +178,12 @@ impl<'x> OpenBlock<'x> {
 			last_hashes: last_hashes,
 		};
 
-		r.block.base.header.set_number(parent.number() + 1);
-		r.block.base.header.set_author(author);
-		r.block.base.header.set_extra_data(extra_data);
+		r.block.base.header.parent_hash = parent.hash();
+		r.block.base.header.number = parent.number + 1;
+		r.block.base.header.author = author;
 		r.block.base.header.set_timestamp_now(parent.timestamp());
-		r.block.base.header.set_parent_hash(parent.hash());
+		r.block.base.header.extra_data = extra_data;
+		r.block.base.header.note_dirty();
 
 		engine.populate_from_parent(&mut r.block.base.header, parent);
 		engine.on_new_block(&mut r.block);
diff --git a/ethcore/src/engine.rs b/ethcore/src/engine.rs
index 6806fcce3..d607ce2e2 100644
--- a/ethcore/src/engine.rs
+++ b/ethcore/src/engine.rs
@@ -84,10 +84,9 @@ pub trait Engine : Sync + Send {
 	/// Don't forget to call Super::populate_from_parent when subclassing & overriding.
 	// TODO: consider including State in the params.
 	fn populate_from_parent(&self, header: &mut Header, parent: &Header) {
-		header.parent_hash = parent.hash;
 		header.difficulty = parent.difficulty;
 		header.gas_limit = parent.gas_limit;
-		header.number = parent.number + 1;
+		header.note_dirty();
 	}
 
 	// TODO: builtin contract routing - to do this properly, it will require removing the built-in configuration-reading logic
diff --git a/ethcore/src/ethereum/ethash.rs b/ethcore/src/ethereum/ethash.rs
index bf0c1d188..f9810b964 100644
--- a/ethcore/src/ethereum/ethash.rs
+++ b/ethcore/src/ethereum/ethash.rs
@@ -104,7 +104,7 @@ impl Engine for Ethash {
 				max(gas_floor_target, gas_limit - gas_limit / bound_divisor + x!(1) + (header.gas_used * x!(6) / x!(5)) / bound_divisor)
 			}
 		};
-
+		header.note_dirty();
 //		info!("ethash: populate_from_parent #{}: difficulty={} and gas_limit={}", header.number, header.difficulty, header.gas_limit);
 	}
 
diff --git a/rpc/src/v1/impls/web3.rs b/rpc/src/v1/impls/web3.rs
index 0a237d56b..4d31f73ae 100644
--- a/rpc/src/v1/impls/web3.rs
+++ b/rpc/src/v1/impls/web3.rs
@@ -31,7 +31,7 @@ impl Web3 for Web3Client {
 	fn client_version(&self, params: Params) -> Result<Value, Error> {
 		match params {
 			Params::None => {
-				Ok(Value::String(version())),
+				Ok(Value::String(version().to_owned().replace("Parity/", "Parity//"))),
 			}
 			_ => Err(Error::invalid_params())
 		}
diff --git a/util/src/misc.rs b/util/src/misc.rs
index 6cd506d02..39ccbf2da 100644
--- a/util/src/misc.rs
+++ b/util/src/misc.rs
@@ -70,7 +70,7 @@ pub fn contents(name: &str) -> Result<Bytes, UtilError> {
 
 /// Get the standard version string for this software.
 pub fn version() -> String {
-	format!("Parity//v{}-{}-{}/{}-{}-{}/rustc{}", env!("CARGO_PKG_VERSION"), short_sha(), commit_date().replace("-", ""), Target::arch(), Target::os(), Target::env(), rustc_version::version())
+	format!("Parity/v{}-{}-{}/{}-{}-{}/rustc{}", env!("CARGO_PKG_VERSION"), short_sha(), commit_date().replace("-", ""), Target::arch(), Target::os(), Target::env(), rustc_version::version())
 }
 
 /// Get the standard version data for this software.

From 68ba0162792dee1ec350ae2ede8dc254f941a18e Mon Sep 17 00:00:00 2001
From: debris <marek.kotewicz@gmail.com>
Date: Wed, 2 Mar 2016 04:25:03 +0100
Subject: [PATCH 16/22] improved blockchain generator

---
 ethcore/src/blockchain/blockchain.rs          |  66 ++++----
 ethcore/src/blockchain/generator/block.rs     |  64 ++++++++
 ethcore/src/blockchain/generator/bloom.rs     |  35 ++++
 ethcore/src/blockchain/generator/complete.rs  |  53 ++++++
 ethcore/src/blockchain/generator/fork.rs      |  42 +++++
 .../generators.rs => generator/generator.rs}  | 154 +++++++-----------
 .../blockchain/{helpers => generator}/mod.rs  |   9 +-
 ethcore/src/blockchain/mod.rs                 |   2 +-
 8 files changed, 294 insertions(+), 131 deletions(-)
 create mode 100644 ethcore/src/blockchain/generator/block.rs
 create mode 100644 ethcore/src/blockchain/generator/bloom.rs
 create mode 100644 ethcore/src/blockchain/generator/complete.rs
 create mode 100644 ethcore/src/blockchain/generator/fork.rs
 rename ethcore/src/blockchain/{helpers/generators.rs => generator/generator.rs} (51%)
 rename ethcore/src/blockchain/{helpers => generator}/mod.rs (81%)

diff --git a/ethcore/src/blockchain/blockchain.rs b/ethcore/src/blockchain/blockchain.rs
index 53dcfb62c..10e844192 100644
--- a/ethcore/src/blockchain/blockchain.rs
+++ b/ethcore/src/blockchain/blockchain.rs
@@ -770,14 +770,15 @@ mod tests {
 	use blockchain::{BlockProvider, BlockChain, BlockChainConfig};
 	use tests::helpers::*;
 	use devtools::*;
-	use blockchain::helpers::generators::{ChainGenerator, ChainIterator};
+	use blockchain::generator::{ChainGenerator, ChainIterator, BlockFinalizer};
 	use views::BlockView;
 
 	#[test]
 	fn basic_blockchain_insert() {
 		let mut canon_chain = ChainGenerator::default();
-		let genesis = canon_chain.next().unwrap().rlp();
-		let first = canon_chain.next().unwrap().rlp();
+		let mut finalizer = BlockFinalizer::default();
+		let genesis = canon_chain.generate(&mut finalizer).unwrap();
+		let first = canon_chain.generate(&mut finalizer).unwrap();
 		let genesis_hash = BlockView::new(&genesis).header_view().sha3();
 		let first_hash = BlockView::new(&first).header_view().sha3();
 
@@ -806,14 +807,12 @@ mod tests {
 	#[cfg_attr(feature="dev", allow(cyclomatic_complexity))]
 	fn test_small_fork() {
 		let mut canon_chain = ChainGenerator::default();
-		let genesis = canon_chain.next().unwrap().rlp();
-		let blocks = canon_chain.clone().take(3).map(|block| block.rlp()).collect::<Vec<_>>();
-		let fork = canon_chain.skip(2).fork(1).take(1).next().unwrap().rlp();
-
-		let b1 = blocks[0].clone();
-		let b2 = blocks[1].clone();
-		let b3a = blocks[2].clone();
-		let b3b = fork;
+		let mut finalizer = BlockFinalizer::default();
+		let genesis = canon_chain.generate(&mut finalizer).unwrap();
+		let b1 = canon_chain.generate(&mut finalizer).unwrap();
+		let b2 = canon_chain.generate(&mut finalizer).unwrap();
+		let b3b = canon_chain.fork(1).generate(&mut finalizer.fork()).unwrap();
+		let b3a = canon_chain.generate(&mut finalizer).unwrap();
 
 		let genesis_hash = BlockView::new(&genesis).header_view().sha3();
 		let b1_hash= BlockView::new(&b1).header_view().sha3();
@@ -897,22 +896,24 @@ mod tests {
 
 	#[test]
 	fn test_reopen_blockchain_db() {
-		let genesis = "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".from_hex().unwrap();
-		let b1 = "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".from_hex().unwrap();
-		let genesis_hash = H256::from_str("5716670833ec874362d65fea27a7cd35af5897d275b31a44944113111e4e96d2").unwrap();
-		let b1_hash = H256::from_str("437e51676ff10756fcfee5edd9159fa41dbcb1b2c592850450371cbecd54ee4f").unwrap();
+		let mut canon_chain = ChainGenerator::default();
+		let mut finalizer = BlockFinalizer::default();
+		let genesis = canon_chain.generate(&mut finalizer).unwrap();
+		let first = canon_chain.generate(&mut finalizer).unwrap();
+		let genesis_hash = BlockView::new(&genesis).header_view().sha3();
+		let first_hash = BlockView::new(&first).header_view().sha3();
 
 		let temp = RandomTempPath::new();
 		{
 			let bc = BlockChain::new(BlockChainConfig::default(), &genesis, temp.as_path());
 			assert_eq!(bc.best_block_hash(), genesis_hash);
-			bc.insert_block(&b1, vec![]);
-			assert_eq!(bc.best_block_hash(), b1_hash);
+			bc.insert_block(&first, vec![]);
+			assert_eq!(bc.best_block_hash(), first_hash);
 		}
 
 		{
 			let bc = BlockChain::new(BlockChainConfig::default(), &genesis, temp.as_path());
-			assert_eq!(bc.best_block_hash(), b1_hash);
+			assert_eq!(bc.best_block_hash(), first_hash);
 		}
 	}
 
@@ -976,29 +977,24 @@ mod tests {
 
 	#[test]
 	fn test_bloom_filter_simple() {
-		let genesis = "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".from_hex().unwrap();
-
-		// block b1 (child of genesis)
-		let b1 = "f90261f901f9a05716670833ec874362d65fea27a7cd35af5897d275b31a44944113111e4e96d2a01dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347948888f1f195afa192cfee860698584c030f4c9db1a0cb52de543653d86ccd13ba3ddf8b052525b04231c6884a4db3188a184681d878a0e78628dd45a1f8dc495594d83b76c588a3ee67463260f8b7d4a42f574aeab29aa0e9244cf7503b79c03d3a099e07a80d2dbc77bb0b502d8a89d51ac0d68dd31313b90100000000200000000000000000000000000000000000000000020000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000400000000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000080004000000000000000000000020008302000001832fefd882520884562791e580a051b3ecba4e3f2b49c11d42dd0851ec514b1be3138080f72a2b6e83868275d98f8877671f479c414b47f862f86080018304cb2f94095e7baea6a6c7c4c2dfeb977efac326af552d870a801ca09e2709d7ec9bbe6b1bbbf0b2088828d14cd5e8642a1fee22dc74bfa89761a7f9a04bd8813dee4be989accdb708b1c2e325a7e9c695a8024e30e89d6c644e424747c0".from_hex().unwrap();
-
-		// block b2 (child of b1)
-		let b2 = "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".from_hex().unwrap();
-
-		// prepare for fork (b1a, child of genesis)
-		let b1a = "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".from_hex().unwrap();
-
-		// fork (b2a, child of b1a, with higher total difficulty)
-		let b2a = "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".from_hex().unwrap();
-
-		// fork back :)
-		let b3 = "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".from_hex().unwrap();
-
+		// TODO: From here
 		let bloom_b1 = H2048::from_str("00000020000000000000000000000000000000000000000002000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000040000000000000010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000008000400000000000000000000002000").unwrap();
 
 		let bloom_b2 = H2048::from_str("00000000000000000000000000000000000000000000020000001000000000000000000000000000000000000000000000000000000000000000000000000000100000000000000000008000000000000000000000000000000000040000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000000000000000000000000000000000000000000000000002000000000000000000040000000000000000000000000000000000000000000000000000000000000000000000000000000000000000").unwrap();
 
 		let bloom_ba = H2048::from_str("00000000000000000000000000000000000000000000020000000800000000000000000000000000000000000000000000000000000000000000000000000000100000000000000000008000000000000000000000000000000000040000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000000000000000000000000000000000000000000000000002000000000000000000040000000000000000000000000000000000000000000000000000000000000000000000000000000000000000").unwrap();
 
+		let mut canon_chain = ChainGenerator::default();
+		let mut finalizer = BlockFinalizer::default();
+		let genesis = canon_chain.generate(&mut finalizer).unwrap();
+		let mut fork = canon_chain.fork(1);
+		let mut fork_finalizer = finalizer.fork();
+		let b1 = fork.with_bloom(bloom_b1.clone()).generate(&mut fork_finalizer).unwrap();
+		let b2 = fork.with_bloom(bloom_b2.clone()).generate(&mut fork_finalizer).unwrap();
+		let b3 = fork.with_bloom(bloom_ba.clone()).generate(&mut fork_finalizer).unwrap();
+		let b1a = canon_chain.with_bloom(bloom_ba.clone()).generate(&mut finalizer).unwrap();
+		let b2a = canon_chain.with_bloom(bloom_ba.clone()).generate(&mut finalizer).unwrap();
+
 		let temp = RandomTempPath::new();
 		let bc = BlockChain::new(BlockChainConfig::default(), &genesis, temp.as_path());
 
diff --git a/ethcore/src/blockchain/generator/block.rs b/ethcore/src/blockchain/generator/block.rs
new file mode 100644
index 000000000..0a3dad399
--- /dev/null
+++ b/ethcore/src/blockchain/generator/block.rs
@@ -0,0 +1,64 @@
+// 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/>.
+
+use util::rlp::*;
+use util::{H256, H2048};
+use util::U256;
+use util::bytes::Bytes;
+use header::Header;
+use transaction::SignedTransaction;
+
+use super::fork::Forkable;
+use super::bloom::WithBloom;
+use super::complete::CompleteBlock;
+
+/// Helper structure, used for encoding blocks.
+#[derive(Default)]
+pub struct Block {
+	pub header: Header,
+	pub transactions: Vec<SignedTransaction>,
+	pub uncles: Vec<Header>
+}
+
+impl Encodable for Block {
+	fn rlp_append(&self, s: &mut RlpStream) {
+		s.begin_list(3);
+		s.append(&self.header);
+		s.append(&self.transactions);
+		s.append(&self.uncles);
+	}
+}
+
+impl Forkable for Block {
+	fn fork(mut self, fork_number: usize) -> Self where Self: Sized {
+		self.header.difficulty = self.header.difficulty - U256::from(fork_number);
+		self
+	}
+}
+
+impl WithBloom for Block {
+	fn with_bloom(mut self, bloom: H2048) -> Self where Self: Sized {
+		self.header.log_bloom = bloom;
+		self
+	}
+}
+
+impl CompleteBlock for Block {
+	fn complete(mut self, parent_hash: H256) -> Bytes {
+		self.header.parent_hash = parent_hash;
+		encode(&self).to_vec()
+	}
+}
diff --git a/ethcore/src/blockchain/generator/bloom.rs b/ethcore/src/blockchain/generator/bloom.rs
new file mode 100644
index 000000000..f61c9d1ff
--- /dev/null
+++ b/ethcore/src/blockchain/generator/bloom.rs
@@ -0,0 +1,35 @@
+// 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/>.
+
+use util::hash::H2048;
+
+pub trait WithBloom {
+	fn with_bloom(self, bloom: H2048) -> Self where Self: Sized;
+}
+
+pub struct Bloom<'a, I> where I: 'a {
+	pub iter: &'a mut I,
+	pub bloom: H2048,
+}
+
+impl<'a, I> Iterator for Bloom<'a, I> where I: Iterator, <I as Iterator>::Item: WithBloom {
+	type Item = <I as Iterator>::Item;
+
+	#[inline]
+	fn next(&mut self) -> Option<Self::Item> {
+		self.iter.next().map(|item| item.with_bloom(self.bloom.clone()))
+	}
+}
diff --git a/ethcore/src/blockchain/generator/complete.rs b/ethcore/src/blockchain/generator/complete.rs
new file mode 100644
index 000000000..39bd587a0
--- /dev/null
+++ b/ethcore/src/blockchain/generator/complete.rs
@@ -0,0 +1,53 @@
+// 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/>.
+
+use util::hash::H256;
+use util::bytes::Bytes;
+use util::sha3::Hashable;
+use views::BlockView;
+
+#[derive(Default, Clone)]
+pub struct BlockFinalizer {
+	parent_hash: H256
+}
+
+impl BlockFinalizer {
+	pub fn fork(&self) -> Self {
+		self.clone()
+	}
+}
+
+pub trait CompleteBlock {
+	fn complete(self, parent_hash: H256) -> Bytes;
+}
+
+pub struct Complete<'a, I> where I: 'a {
+	pub iter: &'a mut I,
+	pub finalizer: &'a mut BlockFinalizer,
+}
+
+impl<'a, I> Iterator for Complete<'a, I> where I: Iterator, <I as Iterator>::Item: CompleteBlock {
+	type Item = Bytes;
+
+	#[inline]
+	fn next(&mut self) -> Option<Self::Item> {
+		self.iter.next().map(|item| {
+			let rlp = item.complete(self.finalizer.parent_hash.clone());
+			self.finalizer.parent_hash = BlockView::new(&rlp).header_view().sha3();
+			rlp
+		})
+	}
+}
diff --git a/ethcore/src/blockchain/generator/fork.rs b/ethcore/src/blockchain/generator/fork.rs
new file mode 100644
index 000000000..f3a4eb267
--- /dev/null
+++ b/ethcore/src/blockchain/generator/fork.rs
@@ -0,0 +1,42 @@
+// 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 trait Forkable {
+	fn fork(self, fork_number: usize) -> Self where Self: Sized;
+}
+
+pub struct Fork<I> {
+	pub iter: I,
+	pub fork_number: usize,
+}
+
+impl<I> Clone for Fork<I> where I: Iterator + Clone {
+	fn clone(&self) -> Self {
+		Fork {
+			iter: self.iter.clone(),
+			fork_number: self.fork_number
+		}
+	}
+}
+
+impl<I> Iterator for Fork<I> where I: Iterator, <I as Iterator>::Item: Forkable {
+	type Item = <I as Iterator>::Item;
+
+	#[inline]
+	fn next(&mut self) -> Option<Self::Item> {
+		self.iter.next().map(|item| item.fork(self.fork_number))
+	}
+}
diff --git a/ethcore/src/blockchain/helpers/generators.rs b/ethcore/src/blockchain/generator/generator.rs
similarity index 51%
rename from ethcore/src/blockchain/helpers/generators.rs
rename to ethcore/src/blockchain/generator/generator.rs
index a20b0cf79..d73b81733 100644
--- a/ethcore/src/blockchain/helpers/generators.rs
+++ b/ethcore/src/blockchain/generator/generator.rs
@@ -14,108 +14,52 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
-use util::rlp::*;
-use util::hash::{H256, H2048};
-use util::uint::{U256};
+use util::hash::H2048;
+use util::uint::U256;
 use util::bytes::Bytes;
-use header::{BlockNumber, Header};
-use transaction::SignedTransaction;
-
-pub trait Forkable {
-	fn fork(self, fork_number: usize) -> Self where Self: Sized;
-}
-
-pub struct Fork<I> {
-	iter: I,
-	fork_number: usize,
-}
-
-impl<I> Iterator for Fork<I> where I: Iterator, <I as Iterator>::Item: Forkable {
-	type Item = <I as Iterator>::Item;
-
-	#[inline]
-	fn next(&mut self) -> Option<Self::Item> {
-		self.iter.next().map(|item| item.fork(self.fork_number))
-	}
-}
-
-pub trait WithBloom {
-	fn with_bloom(self, bloom: H2048) -> Self where Self: Sized;
-}
-
-pub struct Bloom<I> {
-	iter: I,
-	bloom: H2048,
-}
-
-impl<I> Iterator for Bloom<I> where I: Iterator, <I as Iterator>::Item: WithBloom {
-	type Item = <I as Iterator>::Item;
-
-	#[inline]
-	fn next(&mut self) -> Option<Self::Item> {
-		self.iter.next().map(|item| item.with_bloom(self.bloom.clone()))
-	}
-}
+use header::BlockNumber;
+use super::fork::Fork;
+use super::bloom::Bloom;
+use super::complete::{BlockFinalizer, CompleteBlock, Complete};
+use super::block::Block;
 
 /// Chain iterator interface.
-pub trait ChainIterator: Iterator {
+pub trait ChainIterator: Iterator + Sized {
 	/// Should be called to create a fork of current iterator.
 	/// Blocks generated by fork will have lower difficulty than current chain.
-	fn fork(&mut self, fork_number: usize) -> Fork<Self> where Self: Sized;
+	fn fork(&self, fork_number: usize) -> Fork<Self> where Self: Clone;
 	/// Should be called to make every consecutive block have given bloom.
-	fn with_bloom(&mut self, bloom: H2048) -> Bloom<Self> where Self: Sized;
+	fn with_bloom<'a>(&'a mut self, bloom: H2048) -> Bloom<'a, Self>;
+	/// Should be called to complete block. Without complete block may have incorrect hash.
+	fn complete<'a>(&'a mut self, finalizer: &'a mut BlockFinalizer) -> Complete<'a, Self>;
+	/// Completes and generates block.
+	fn generate<'a>(&'a mut self, finalizer: &'a mut BlockFinalizer) -> Option<Bytes> where Self::Item: CompleteBlock;
 }
 
-impl<I> ChainIterator for I where I: Iterator + Sized + Clone {
-	fn fork(&mut self, fork_number: usize) -> Fork<Self> {
+impl<I> ChainIterator for I where I: Iterator + Sized {
+	fn fork(&self, fork_number: usize) -> Fork<Self> where I: Clone {
 		Fork {
 			iter: self.clone(),
 			fork_number: fork_number
 		}
 	}
 
-	fn with_bloom(&mut self, bloom: H2048) -> Bloom<Self> {
+	fn with_bloom<'a>(&'a mut self, bloom: H2048) -> Bloom<'a, Self> {
 		Bloom {
-			iter: self.clone(),
+			iter: self,
 			bloom: bloom
 		}
 	}
-}
 
-/// Helper structure, used for encoding blocks.
-#[derive(Default)]
-pub struct Block {
-	header: Header,
-	transactions: Vec<SignedTransaction>,
-	uncles: Vec<Header>
-}
-
-impl Block {
-	pub fn rlp(&self) -> Bytes {
-		encode(self).to_vec()
+	fn complete<'a>(&'a mut self, finalizer: &'a mut BlockFinalizer) -> Complete<'a, Self> {
+		Complete {
+			iter: self,
+			finalizer: finalizer
+		}
 	}
-}
 
-impl Encodable for Block {
-	fn rlp_append(&self, s: &mut RlpStream) {
-		s.begin_list(3);
-		s.append(&self.header);
-		s.append(&self.transactions);
-		s.append(&self.uncles);
-	}
-}
-
-impl Forkable for Block {
-	fn fork(mut self, fork_number: usize) -> Self where Self: Sized {
-		self.header.difficulty = self.header.difficulty - U256::from(fork_number);
-		self
-	}
-}
-
-impl WithBloom for Block {
-	fn with_bloom(mut self, bloom: H2048) -> Self where Self: Sized {
-		self.header.log_bloom = bloom;
-		self
+	fn generate<'a>(&'a mut self, finalizer: &'a mut BlockFinalizer) -> Option<Bytes> where <I as Iterator>::Item: CompleteBlock {
+		self.complete(finalizer).next()
 	}
 }
 
@@ -124,8 +68,6 @@ impl WithBloom for Block {
 pub struct ChainGenerator {
 	/// Next block number.
 	number: BlockNumber,
-	/// Next block parent hash.
-	parent_hash: H256,
 	/// Next block difficulty.
 	difficulty: U256,
 }
@@ -133,7 +75,6 @@ pub struct ChainGenerator {
 impl ChainGenerator {
 	fn prepare_block(&self) -> Block {
 		let mut block = Block::default();
-		block.header.parent_hash = self.parent_hash.clone();
 		block.header.number = self.number;
 		block.header.difficulty = self.difficulty;
 		block
@@ -144,7 +85,6 @@ impl Default for ChainGenerator {
 	fn default() -> Self {
 		ChainGenerator {
 			number: 0,
-			parent_hash: H256::default(),
 			difficulty: U256::from(1000),
 		}
 	}
@@ -156,30 +96,28 @@ impl Iterator for ChainGenerator {
 	fn next(&mut self) -> Option<Self::Item> {
 		let block = self.prepare_block();
 		self.number += 1;
-		self.parent_hash = block.header.hash();
 		Some(block)
 	}
 }
 
-
-#[cfg(test)]
 mod tests {
-	use util::hash::H256;
+	use util::hash::{H256, H2048};
 	use util::sha3::Hashable;
 	use views::BlockView;
-	use super::{ChainIterator, ChainGenerator};
+	use blockchain::generator::{ChainIterator, ChainGenerator, BlockFinalizer};
 
 	#[test]
 	fn canon_chain_generator() {
 		let mut canon_chain = ChainGenerator::default();
+		let mut finalizer = BlockFinalizer::default();
 
-		let genesis_rlp = canon_chain.next().unwrap().rlp();
+		let genesis_rlp = canon_chain.generate(&mut finalizer).unwrap();
 		let genesis = BlockView::new(&genesis_rlp);
 
 		assert_eq!(genesis.header_view().parent_hash(), H256::default());
 		assert_eq!(genesis.header_view().number(), 0);
 
-		let b1_rlp = canon_chain.next().unwrap().rlp();
+		let b1_rlp = canon_chain.generate(&mut finalizer).unwrap();
 		let b1 = BlockView::new(&b1_rlp);
 
 		assert_eq!(b1.header_view().parent_hash(), genesis.header_view().sha3());
@@ -187,17 +125,45 @@ mod tests {
 
 		let mut fork_chain = canon_chain.fork(1);
 
-		let b2_rlp_fork = fork_chain.next().unwrap().rlp();
+		let b2_rlp_fork = fork_chain.generate(&mut finalizer.fork()).unwrap();
 		let b2_fork = BlockView::new(&b2_rlp_fork);
 
 		assert_eq!(b2_fork.header_view().parent_hash(), b1.header_view().sha3());
 		assert_eq!(b2_fork.header_view().number(), 2);
 
-		let b2_rlp = canon_chain.next().unwrap().rlp();
+		let b2_rlp = canon_chain.generate(&mut finalizer).unwrap();
 		let b2 = BlockView::new(&b2_rlp);
 
 		assert_eq!(b2.header_view().parent_hash(), b1.header_view().sha3());
 		assert_eq!(b2.header_view().number(), 2);
 		assert!(b2.header_view().difficulty() > b2_fork.header_view().difficulty());
 	}
+
+	#[test]
+	fn with_bloom_generator() {
+		let bloom = H2048([0x1; 256]);
+		let mut gen = ChainGenerator::default();
+		let mut finalizer = BlockFinalizer::default();
+
+		let block0_rlp = gen.with_bloom(bloom).generate(&mut finalizer).unwrap();
+		let block1_rlp = gen.generate(&mut finalizer).unwrap();
+		let block0 = BlockView::new(&block0_rlp);
+		let block1 = BlockView::new(&block1_rlp);
+
+		assert_eq!(block0.header_view().number(), 0);
+		assert_eq!(block0.header_view().parent_hash(), H256::default());
+
+		assert_eq!(block1.header_view().number(), 1);
+		assert_eq!(block1.header_view().parent_hash(), block0.header_view().sha3());
+
+	}
+
+	#[test]
+	fn generate_1000_blocks() {
+		let generator = ChainGenerator::default();
+		let mut finalizer = BlockFinalizer::default();
+		let blocks: Vec<_> = generator.take(1000).complete(&mut finalizer).collect();
+		assert_eq!(blocks.len(), 1000);
+	}
 }
+
diff --git a/ethcore/src/blockchain/helpers/mod.rs b/ethcore/src/blockchain/generator/mod.rs
similarity index 81%
rename from ethcore/src/blockchain/helpers/mod.rs
rename to ethcore/src/blockchain/generator/mod.rs
index 233f8f1f8..88fdec0e4 100644
--- a/ethcore/src/blockchain/helpers/mod.rs
+++ b/ethcore/src/blockchain/generator/mod.rs
@@ -14,4 +14,11 @@
 // 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 generators;
+mod bloom;
+mod block;
+mod complete;
+mod fork;
+pub mod generator;
+
+pub use self::complete::BlockFinalizer;
+pub use self::generator::{ChainIterator, ChainGenerator};
diff --git a/ethcore/src/blockchain/mod.rs b/ethcore/src/blockchain/mod.rs
index 60a1aeb33..b0679b563 100644
--- a/ethcore/src/blockchain/mod.rs
+++ b/ethcore/src/blockchain/mod.rs
@@ -24,7 +24,7 @@ mod cache;
 mod tree_route;
 mod update;
 #[cfg(test)]
-mod helpers;
+mod generator;
 
 pub use self::blockchain::{BlockProvider, BlockChain, BlockChainConfig};
 pub use self::cache::CacheSize;

From 010659cf12b0accaa678232176d60f338f15f1a9 Mon Sep 17 00:00:00 2001
From: debris <marek.kotewicz@gmail.com>
Date: Wed, 2 Mar 2016 04:54:47 +0100
Subject: [PATCH 17/22] added missing , in comment

---
 ethcore/src/blockchain/generator/generator.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ethcore/src/blockchain/generator/generator.rs b/ethcore/src/blockchain/generator/generator.rs
index d73b81733..16f2330c2 100644
--- a/ethcore/src/blockchain/generator/generator.rs
+++ b/ethcore/src/blockchain/generator/generator.rs
@@ -30,7 +30,7 @@ pub trait ChainIterator: Iterator + Sized {
 	fn fork(&self, fork_number: usize) -> Fork<Self> where Self: Clone;
 	/// Should be called to make every consecutive block have given bloom.
 	fn with_bloom<'a>(&'a mut self, bloom: H2048) -> Bloom<'a, Self>;
-	/// Should be called to complete block. Without complete block may have incorrect hash.
+	/// Should be called to complete block. Without complete, block may have incorrect hash.
 	fn complete<'a>(&'a mut self, finalizer: &'a mut BlockFinalizer) -> Complete<'a, Self>;
 	/// Completes and generates block.
 	fn generate<'a>(&'a mut self, finalizer: &'a mut BlockFinalizer) -> Option<Bytes> where Self::Item: CompleteBlock;

From 32074cc420edf2f450e29c89a7ef64a58d2c6d6a Mon Sep 17 00:00:00 2001
From: debris <marek.kotewicz@gmail.com>
Date: Wed, 2 Mar 2016 05:55:42 +0100
Subject: [PATCH 18/22] fixed compilation issue caused by incorrect merge

---
 ethcore/src/blockchain/generator/generator.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ethcore/src/blockchain/generator/generator.rs b/ethcore/src/blockchain/generator/generator.rs
index 16f2330c2..51e6294fc 100644
--- a/ethcore/src/blockchain/generator/generator.rs
+++ b/ethcore/src/blockchain/generator/generator.rs
@@ -15,7 +15,7 @@
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
 use util::hash::H2048;
-use util::uint::U256;
+use util::numbers::U256;
 use util::bytes::Bytes;
 use header::BlockNumber;
 use super::fork::Fork;

From 67a1f2065e2611c73e64bbf74c0812b224b64fd7 Mon Sep 17 00:00:00 2001
From: debris <marek.kotewicz@gmail.com>
Date: Wed, 2 Mar 2016 06:00:00 +0100
Subject: [PATCH 19/22] fixed broken master

---
 ethcore/src/blockchain/helpers/generators.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ethcore/src/blockchain/helpers/generators.rs b/ethcore/src/blockchain/helpers/generators.rs
index a20b0cf79..2fd517e50 100644
--- a/ethcore/src/blockchain/helpers/generators.rs
+++ b/ethcore/src/blockchain/helpers/generators.rs
@@ -16,7 +16,7 @@
 
 use util::rlp::*;
 use util::hash::{H256, H2048};
-use util::uint::{U256};
+use util::numbers::{U256};
 use util::bytes::Bytes;
 use header::{BlockNumber, Header};
 use transaction::SignedTransaction;

From 34b812696b24427f3eb3bbb1c9f67119acf87230 Mon Sep 17 00:00:00 2001
From: Nikolay Volf <nikvolf@gmail.com>
Date: Wed, 2 Mar 2016 08:49:48 +0300
Subject: [PATCH 20/22] remove unused imports

---
 util/bigint/src/uint.rs | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/util/bigint/src/uint.rs b/util/bigint/src/uint.rs
index 4cc0dfc0e..5b67ba41d 100644
--- a/util/bigint/src/uint.rs
+++ b/util/bigint/src/uint.rs
@@ -40,20 +40,13 @@ use std::fmt;
 use std::cmp;
 
 use std::mem;
-use std::ops;
-use std::slice;
-use std::result;
-use std::option;
 use std::str::{FromStr};
 use std::convert::From;
 use std::hash::{Hash, Hasher};
 use std::ops::*;
 use std::cmp::*;
-use std::collections::*;
 
 use serde;
-use rustc_serialize::json::Json;
-use rustc_serialize::base64::FromBase64;
 use rustc_serialize::hex::{FromHex, FromHexError, ToHex};
 
 

From 5dfc3d28491e0e98b54e34a027031e6a54163832 Mon Sep 17 00:00:00 2001
From: Nikolay Volf <nikvolf@gmail.com>
Date: Wed, 2 Mar 2016 13:01:38 +0300
Subject: [PATCH 21/22] resolving path at runtime

---
 util/cov.sh                  |  2 +-
 util/src/keys/geth_import.rs | 20 +++++++++++++++-----
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/util/cov.sh b/util/cov.sh
index 19aa3b892..121f9629d 100755
--- a/util/cov.sh
+++ b/util/cov.sh
@@ -5,5 +5,5 @@ fi
 
 cargo test --no-run || exit $?
 mkdir -p target/coverage
-kcov --exclude-pattern ~/.multirust,rocksdb,secp256k1 --include-pattern src --verify target/coverage target/debug/ethcore_util*
+./kcov --exclude-pattern ~/.multirust,rocksdb,secp256k1 --include-pattern src --verify target/coverage target/debug/ethcore_util*
 xdg-open target/coverage/index.html
diff --git a/util/src/keys/geth_import.rs b/util/src/keys/geth_import.rs
index cdbd9b213..dbd9f0fe0 100644
--- a/util/src/keys/geth_import.rs
+++ b/util/src/keys/geth_import.rs
@@ -99,10 +99,20 @@ mod tests {
 	use common::*;
 	use keys::store::SecretStore;
 
+	fn test_path() -> &'static str {
+		match ::std::fs::metadata("res") {
+			Ok(_) => "res/geth_keystore",
+			Err(_) => "util/res/geth_keystore"
+		}
+	}
+
+	fn test_path_param(param_val: &'static str) -> String {
+		test_path().to_owned() + param_val
+	}
 
 	#[test]
 	fn can_enumerate() {
-		let keys = enumerate_geth_keys(Path::new("res/geth_keystore")).unwrap();
+		let keys = enumerate_geth_keys(Path::new(test_path())).unwrap();
 		assert_eq!(2, keys.len());
 	}
 
@@ -110,7 +120,7 @@ mod tests {
 	fn can_import() {
 		let temp = ::devtools::RandomTempPath::create_dir();
 		let mut secret_store = SecretStore::new_in(temp.as_path());
-		import_geth_key(&mut secret_store, Path::new("res/geth_keystore/UTC--2016-02-17T09-20-45.721400158Z--3f49624084b67849c7b4e805c5988c21a430f9d9")).unwrap();
+		import_geth_key(&mut secret_store, Path::new(&test_path_param("/UTC--2016-02-17T09-20-45.721400158Z--3f49624084b67849c7b4e805c5988c21a430f9d9"))).unwrap();
 		let key = secret_store.account(&Address::from_str("3f49624084b67849c7b4e805c5988c21a430f9d9").unwrap());
 		assert!(key.is_some());
 	}
@@ -119,7 +129,7 @@ mod tests {
 	fn can_import_directory() {
 		let temp = ::devtools::RandomTempPath::create_dir();
 		let mut secret_store = SecretStore::new_in(temp.as_path());
-		import_geth_keys(&mut secret_store, Path::new("res/geth_keystore")).unwrap();
+		import_geth_keys(&mut secret_store, Path::new(test_path())).unwrap();
 
 		let key = secret_store.account(&Address::from_str("3f49624084b67849c7b4e805c5988c21a430f9d9").unwrap());
 		assert!(key.is_some());
@@ -134,7 +144,7 @@ mod tests {
 		let temp = ::devtools::RandomTempPath::create_dir();
 		{
 			let mut secret_store = SecretStore::new_in(temp.as_path());
-			import_geth_keys(&mut secret_store, Path::new("res/geth_keystore")).unwrap();
+			import_geth_keys(&mut secret_store, Path::new(test_path())).unwrap();
 		}
 
 		let key_directory = KeyDirectory::new(&temp.as_path());
@@ -156,7 +166,7 @@ mod tests {
 
 		let temp = ::devtools::RandomTempPath::create_dir();
 		let mut secret_store = SecretStore::new_in(temp.as_path());
-		import_geth_keys(&mut secret_store, Path::new("res/geth_keystore")).unwrap();
+		import_geth_keys(&mut secret_store, Path::new(test_path())).unwrap();
 
 		let val = secret_store.get::<Bytes>(&H128::from_str("62a0ad73556d496a8e1c0783d30d3ace").unwrap(), "123");
 		assert!(val.is_ok());

From 771fbcbd27bd900902f7705bd9d107f129e0ca2b Mon Sep 17 00:00:00 2001
From: Nikolay Volf <nikvolf@gmail.com>
Date: Wed, 2 Mar 2016 13:02:33 +0300
Subject: [PATCH 22/22] remove redundant modification

---
 util/cov.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/util/cov.sh b/util/cov.sh
index 121f9629d..19aa3b892 100755
--- a/util/cov.sh
+++ b/util/cov.sh
@@ -5,5 +5,5 @@ fi
 
 cargo test --no-run || exit $?
 mkdir -p target/coverage
-./kcov --exclude-pattern ~/.multirust,rocksdb,secp256k1 --include-pattern src --verify target/coverage target/debug/ethcore_util*
+kcov --exclude-pattern ~/.multirust,rocksdb,secp256k1 --include-pattern src --verify target/coverage target/debug/ethcore_util*
 xdg-open target/coverage/index.html