Merge branch 'develop' of github.com:ethereum/cpp-ethereum into develop

* 'develop' of github.com:ethereum/cpp-ethereum:
  Fixes for state debugging.
  Debug past transactions in debugger.
  Refactored a lot of State. Killed playback() API. State diffing at arbitrary places in chain.

README.md

@@ -12,7 +12,7 @@ See the [Wiki](https://github.com/ethereum/cpp-ethereum/wiki) for build instruct
 
 ### Testing
 
-To run the tests, make sure you clone the tests repository from github.com/ethereum to tests is a sibling to cpp-ethereum-build.
+To run the tests, make sure you clone the tests repository from github.com/ethereum to tests as a sibling to cpp-ethereum.
 
 ### Yet To Do
 

alethzero/Main.ui

@@ -165,6 +165,7 @@
     <addaction name="paranoia"/>
     <addaction name="killBlockchain"/>
     <addaction name="inject"/>
+    <addaction name="debugStepback"/>
    </widget>
    <addaction name="menu_File"/>
    <addaction name="menu_Network"/>
@@ -1430,6 +1431,14 @@ font-family: Monospace, Ubuntu Mono, Lucida Console, Courier New</string>
     <string>&amp;Load Javascript...</string>
    </property>
   </action>
+  <action name="debugStepback">
+   <property name="text">
+    <string>Single Step &amp;Backwards</string>
+   </property>
+   <property name="shortcut">
+    <string>Shift+F10</string>
+   </property>
+  </action>
  </widget>
  <layoutdefault spacing="6" margin="11"/>
  <customwidgets>

alethzero/MainWin.cpp

@@ -674,17 +674,12 @@ void Main::refresh(bool _override)
 	}
 }
 
-string Main::renderDiff(eth::State const& fs, eth::State const& ts) const
+string Main::renderDiff(eth::StateDiff const& _d) const
 {
 	stringstream s;
 
-	eth::StateDiff d = fs.diff(ts);
-
-	s << "Pre: " << fs.rootHash() << "<br/>";
-	s << "Post: <b>" << ts.rootHash() << "</b>";
-
 	auto indent = "<code style=\"white-space: pre\">     </code>";
-	for (auto const& i: d.accounts)
+	for (auto const& i: _d.accounts)
 	{
 		s << "<hr/>";
 
@@ -773,9 +768,10 @@ void Main::on_transactionQueue_currentItemChanged()
 		}
 		s << "<hr/>";
 
-		eth::State fs = m_client->postState().fromPending(i);
-		eth::State ts = m_client->postState().fromPending(i + 1);
-		s << renderDiff(fs, ts);
+//		s << "Pre: " << fs.rootHash() << "<br/>";
+//		s << "Post: <b>" << ts.rootHash() << "</b>";
+
+		s << renderDiff(m_client->postState().pendingDiff(i));
 	}
 
 	ui->pendingInfo->setHtml(QString::fromStdString(s.str()));
@@ -872,15 +868,25 @@ void Main::on_blocks_currentItemChanged()
 				if (tx.data.size())
 					s << eth::memDump(tx.data, 16, true);
 			}
-			s << "<br/><br/>";
-/*			BlockInfo parentBlockInfo();
-			eth::State s = m_client->state();
-			s.resetTo(bi.);
-			s <<*/
-
-//			eth::State s = m_client->blockChain().stateAt(h);
-//			StateDiff d = s.pendingDiff(txi);
-			// TODO: Make function: BlockChain::stateAt (grabs block's parent's stateRoot, playback()'s transactions), then use State::fromPending(). Maybe even make a State::pendingDiff().
+			auto st = eth::State(m_client->state().db(), m_client->blockChain(), h);
+			s << renderDiff(st.pendingDiff(txi));
+
+			m_executiveState = st.fromPending(txi);
+			m_currentExecution = unique_ptr<Executive>(new Executive(m_executiveState));
+			Transaction t = st.pending()[txi];
+			auto r = t.rlp();
+
+			debugFinished();
+			bool done = m_currentExecution->setup(&r);
+			if (!done)
+			{
+				auto startGas = m_currentExecution->vm().gas();
+				for (; !done; done = m_currentExecution->go(1))
+					m_history.append(WorldState({m_currentExecution->vm().curPC(), m_currentExecution->vm().gas(), startGas - m_currentExecution->vm().gas(), m_currentExecution->vm().stack(), m_currentExecution->vm().memory(), m_currentExecution->state().storage(m_currentExecution->ext().myAddress)}));
+				initDebugger();
+				updateDebugger();
+			}
+			m_currentExecution.reset();
 		}
 
 
@@ -1210,14 +1216,15 @@ void Main::on_debug_clicked()
 			t.receiveAddress = isCreation() ? Address() : fromString(ui->destination->currentText());
 			t.sign(s);
 			auto r = t.rlp();
-			m_currentExecution->setup(&r);
 
+			m_currentExecution->setup(&r);
 			m_pcWarp.clear();
 			m_history.clear();
 			bool ok = true;
+			auto gasBegin = m_currentExecution->vm().gas();
 			while (ok)
 			{
-				m_history.append(WorldState({m_currentExecution->vm().curPC(), m_currentExecution->vm().gas(), m_currentExecution->vm().stack(), m_currentExecution->vm().memory(), m_currentExecution->state().storage(m_currentExecution->ext().myAddress)}));
+				m_history.append(WorldState({m_currentExecution->vm().curPC(), m_currentExecution->vm().gas(), gasBegin - m_currentExecution->vm().gas(), m_currentExecution->vm().stack(), m_currentExecution->vm().memory(), m_currentExecution->state().storage(m_currentExecution->ext().myAddress)}));
 				ok = !m_currentExecution->go(1);
 			}
 			initDebugger();
@@ -1244,6 +1251,11 @@ void Main::on_debugStep_triggered()
 	ui->debugTimeline->setValue(ui->debugTimeline->value() + 1);
 }
 
+void Main::on_debugStepback_triggered()
+{
+	ui->debugTimeline->setValue(ui->debugTimeline->value() - 1);
+}
+
 void Main::debugFinished()
 {
 	m_pcWarp.clear();
@@ -1255,6 +1267,7 @@ void Main::debugFinished()
 	ui->debugStateInfo->setText("");
 //	ui->send->setEnabled(true);
 	ui->debugStep->setEnabled(false);
+	ui->debugStepback->setEnabled(false);
 	ui->debugPanel->setEnabled(false);
 }
 
@@ -1262,6 +1275,7 @@ void Main::initDebugger()
 {
 //	ui->send->setEnabled(false);
 	ui->debugStep->setEnabled(true);
+	ui->debugStepback->setEnabled(true);
 	ui->debugPanel->setEnabled(true);
 	ui->debugCode->setEnabled(false);
 	ui->debugTimeline->setMinimum(0);

alethzero/MainWin.h

@@ -46,6 +46,7 @@ struct WorldState
 {
 	eth::u256 curPC;
 	eth::u256 gas;
+	eth::u256 gasUsed;
 	eth::u256s stack;
 	eth::bytes memory;
 	std::map<eth::u256, eth::u256> storage;
@@ -101,6 +102,7 @@ private slots:
 	void on_quit_triggered() { close(); }
 	void on_urlEdit_returnPressed();
 	void on_debugStep_triggered();
+	void on_debugStepback_triggered();
 	void on_debug_clicked();
 	void on_debugTimeline_valueChanged();
 	void on_jsInput_returnPressed();
@@ -131,7 +133,7 @@ private:
 	void debugFinished();
 	QString render(eth::Address _a) const;
 	eth::Address fromString(QString const& _a) const;
-	std::string renderDiff(eth::State const& fs, eth::State const& ts) const;
+	std::string renderDiff(eth::StateDiff const& _d) const;
 
 	eth::State const& state() const;
 

libethereum/AddressState.h

@@ -46,7 +46,7 @@ public:
 	u256 const& nonce() const { return m_nonce; }
 	void incNonce() { m_nonce++; }
 
-	h256 oldRoot() const { return m_storageRoot; }
+	h256 baseRoot() const { return m_storageRoot; }
 	std::map<u256, u256> const& storage() const { return m_storageOverlay; }
 	void setStorage(u256 _p, u256 _v) { m_storageOverlay[_p] = _v; }
 

libethereum/BlockChain.cpp

@@ -234,19 +234,11 @@ void BlockChain::import(bytes const& _block, OverlayDB const& _db)
 	try
 #endif
 	{
-		// Check family:
-		BlockInfo biParent(block(bi.parentHash));
-		bi.verifyParent(biParent);
-
 		// Check transactions are valid and that they result in a state equivalent to our state_root.
-		State s(bi.coinbaseAddress, _db);
-		s.sync(*this, bi.parentHash);
-
 		// Get total difficulty increase and update state, checking it.
-		BlockInfo biGrandParent;
-		if (pd.number)
-			biGrandParent.populate(block(pd.parent));
-		auto tdIncrease = s.playback(&_block, bi, biParent, biGrandParent, true);
+		State s(bi.coinbaseAddress, _db);
+		auto tdIncrease = s.enactOn(&_block, bi, *this);
+		s.cleanup(true);
 		td = pd.totalDifficulty + tdIncrease;
 
 #if ETH_PARANOIA

libethereum/BlockChain.h

@@ -55,6 +55,7 @@ typedef std::map<h256, BlockDetails> BlockDetailsHash;
 static const BlockDetails NullBlockDetails;
 static const h256s NullH256s;
 
+class State;
 class OverlayDB;
 
 class AlreadyHaveBlock: public std::exception {};

libethereum/Executive.cpp

@@ -40,7 +40,7 @@ u256 Executive::gasUsed() const
 	return m_t.gas - m_endGas;
 }
 
-void Executive::setup(bytesConstRef _rlp)
+bool Executive::setup(bytesConstRef _rlp)
 {
 	// Entry point for a user-executed transaction.
 	m_t = Transaction(_rlp);
@@ -95,12 +95,12 @@ void Executive::setup(bytesConstRef _rlp)
 	m_s.subBalance(m_sender, cost);
 
 	if (m_t.isCreation())
-		create(m_sender, m_t.value, m_t.gasPrice, m_t.gas - gasCost, &m_t.data, m_sender);
+		return create(m_sender, m_t.value, m_t.gasPrice, m_t.gas - gasCost, &m_t.data, m_sender);
 	else
-		call(m_t.receiveAddress, m_sender, m_t.value, m_t.gasPrice, bytesConstRef(&m_t.data), m_t.gas - gasCost, m_sender);
+		return call(m_t.receiveAddress, m_sender, m_t.value, m_t.gasPrice, bytesConstRef(&m_t.data), m_t.gas - gasCost, m_sender);
 }
 
-void Executive::call(Address _receiveAddress, Address _senderAddress, u256 _value, u256 _gasPrice, bytesConstRef _data, u256 _gas, Address _originAddress)
+bool Executive::call(Address _receiveAddress, Address _senderAddress, u256 _value, u256 _gasPrice, bytesConstRef _data, u256 _gas, Address _originAddress)
 {
 //	cnote << "Transferring" << formatBalance(_value) << "to receiver.";
 	m_s.addBalance(_receiveAddress, _value);
@@ -110,12 +110,16 @@ void Executive::call(Address _receiveAddress, Address _senderAddress, u256 _valu
 		m_vm = new VM(_gas);
 		bytes const& c = m_s.code(_receiveAddress);
 		m_ext = new ExtVM(m_s, _receiveAddress, _senderAddress, _originAddress, _value, _gasPrice, _data, &c);
+		return false;
 	}
 	else
+	{
 		m_endGas = _gas;
+		return true;
+	}
 }
 
-void Executive::create(Address _sender, u256 _endowment, u256 _gasPrice, u256 _gas, bytesConstRef _init, Address _origin)
+bool Executive::create(Address _sender, u256 _endowment, u256 _gasPrice, u256 _gas, bytesConstRef _init, Address _origin)
 {
 	m_newAddress = right160(sha3(rlpList(_sender, m_s.transactionsFrom(_sender) - 1)));
 	while (m_s.addressInUse(m_newAddress))
@@ -127,6 +131,7 @@ void Executive::create(Address _sender, u256 _endowment, u256 _gasPrice, u256 _g
 	// Execute _init.
 	m_vm = new VM(_gas);
 	m_ext = new ExtVM(m_s, m_newAddress, _sender, _origin, _endowment, _gasPrice, bytesConstRef(), _init);
+	return _init.empty();
 }
 
 bool Executive::go(uint64_t _steps)

libethereum/Executive.h

@@ -40,9 +40,9 @@ public:
 	Executive(State& _s): m_s(_s) {}
 	~Executive();
 
-	void setup(bytesConstRef _transaction);
-	void create(Address _txSender, u256 _endowment, u256 _gasPrice, u256 _gas, bytesConstRef _code, Address _originAddress);
-	void call(Address _myAddress, Address _txSender, u256 _txValue, u256 _gasPrice, bytesConstRef _txData, u256 _gas, Address _originAddress);
+	bool setup(bytesConstRef _transaction);
+	bool create(Address _txSender, u256 _endowment, u256 _gasPrice, u256 _gas, bytesConstRef _code, Address _originAddress);
+	bool call(Address _myAddress, Address _txSender, u256 _txValue, u256 _gasPrice, bytesConstRef _txData, u256 _gas, Address _originAddress);
 	bool go(uint64_t _steps = (uint64_t)-1);
 	void finalize();
 	u256 gasUsed() const;

libethereum/State.cpp

@@ -37,6 +37,8 @@ using namespace eth;
 
 #define ctrace clog(StateTrace)
 
+static const u256 c_blockReward = 1500 * finney;
+
 OverlayDB State::openDB(std::string _path, bool _killExisting)
 {
 	if (_path.empty())
@@ -57,10 +59,9 @@ OverlayDB State::openDB(std::string _path, bool _killExisting)
 State::State(Address _coinbaseAddress, OverlayDB const& _db):
 	m_db(_db),
 	m_state(&m_db),
-	m_ourAddress(_coinbaseAddress)
+	m_ourAddress(_coinbaseAddress),
+	m_blockReward(c_blockReward)
 {
-	m_blockReward = 1500 * finney;
-
 	secp256k1_start();
 
 	// Initialise to the state entailed by the genesis block; this guarantees the trie is built correctly.
@@ -81,6 +82,31 @@ State::State(Address _coinbaseAddress, OverlayDB const& _db):
 	paranoia("end of normal construction.", true);
 }
 
+State::State(OverlayDB const& _db, BlockChain const& _bc, h256 _h):
+	m_db(_db),
+	m_state(&m_db),
+	m_blockReward(c_blockReward)
+{
+	secp256k1_start();
+
+	// TODO THINK: is this necessary?
+	m_state.init();
+
+	auto b = _bc.block(_h);
+	BlockInfo bi;
+	BlockInfo bip;
+	if (_h)
+		bi.populate(b);
+	if (bi && bi.number)
+		bip.populate(_bc.block(bi.parentHash));
+	if (!_h || !bip)
+		return;
+	m_ourAddress = bi.coinbaseAddress;
+
+	sync(_bc, bi.parentHash, bip);
+	enact(b);
+}
+
 State::State(State const& _s):
 	m_db(_s.m_db),
 	m_state(&m_db, _s.m_state.root()),
@@ -280,16 +306,19 @@ bool State::sync(BlockChain const& _bc)
 	return sync(_bc, _bc.currentHash());
 }
 
-bool State::sync(BlockChain const& _bc, h256 _block)
+bool State::sync(BlockChain const& _bc, h256 _block, BlockInfo const& _bi)
 {
 	bool ret = false;
 	// BLOCK
-	BlockInfo bi;
+	BlockInfo bi = _bi;
 	try
 	{
-		auto b = _bc.block(_block);
-		bi.populate(b);
-//		bi.verifyInternals(_bc.block(_block));	// Unneeded - we already verify on import into the blockchain.
+		if (!bi)
+		{
+			auto b = _bc.block(_block);
+			bi.populate(b);
+//			bi.verifyInternals(_bc.block(_block));	// Unneeded - we already verify on import into the blockchain.
+		}
 	}
 	catch (...)
 	{
@@ -328,8 +357,23 @@ bool State::sync(BlockChain const& _bc, h256 _block)
 		resetCurrent();
 
 		// Iterate through in reverse, playing back each of the blocks.
-		for (auto it = chain.rbegin(); it != chain.rend(); ++it)
-			trustedPlayback(_bc.block(*it), true);
+		try
+		{
+			for (auto it = chain.rbegin(); it != chain.rend(); ++it)
+			{
+				auto b = _bc.block(*it);
+				m_currentBlock.populate(b);
+				m_currentBlock.verifyInternals(b);
+				enact(b, BlockInfo());
+				cleanup(true);
+			}
+		}
+		catch (...)
+		{
+			// TODO: Slightly nicer handling? :-)
+			cerr << "ERROR: Corrupt block-chain! Delete your block-chain DB and restart." << endl;
+			exit(1);
+		}
 
 		resetCurrent();
 		ret = true;
@@ -337,6 +381,21 @@ bool State::sync(BlockChain const& _bc, h256 _block)
 	return ret;
 }
 
+u256 State::enactOn(bytesConstRef _block, BlockInfo const& _bi, BlockChain const& _bc)
+{
+	// Check family:
+	BlockInfo biParent(_bc.block(_bi.parentHash));
+	_bi.verifyParent(biParent);
+	BlockInfo biGrandParent;
+	if (biParent.number)
+		biGrandParent.populate(_bc.block(biParent.parentHash));
+	sync(_bc, _bi.parentHash);
+	resetCurrent();
+	m_currentBlock = _bi;
+	m_previousBlock = biParent;
+	return enact(_block, biGrandParent);
+}
+
 map<Address, u256> State::addresses() const
 {
 	map<Address, u256> ret;
@@ -366,7 +425,7 @@ void State::resetCurrent()
 	// TODO: check.
 
 	m_lastTx = m_db;
-	m_state.setRoot(m_currentBlock.stateRoot);
+	m_state.setRoot(m_previousBlock.stateRoot);
 
 	paranoia("begin resetCurrent", true);
 }
@@ -448,33 +507,16 @@ bool State::sync(TransactionQueue& _tq, bool* _changed)
 	return ret;
 }
 
-u256 State::playback(bytesConstRef _block, BlockInfo const& _bi, BlockInfo const& _parent, BlockInfo const& _grandParent, bool _fullCommit)
+u256 State::enact(bytesConstRef _block, BlockInfo const& _grandParent)
 {
-	resetCurrent();
-	m_currentBlock = _bi;
-	m_previousBlock = _parent;
-	return playbackRaw(_block, _grandParent, _fullCommit);
-}
+	// m_currentBlock is assumed to be prepopulated and reset.
 
-u256 State::trustedPlayback(bytesConstRef _block, bool _fullCommit)
-{
-	try
-	{
-		m_currentBlock.populate(_block);
-		m_currentBlock.verifyInternals(_block);
-		return playbackRaw(_block, BlockInfo(), _fullCommit);
-	}
-	catch (...)
-	{
-		// TODO: Slightly nicer handling? :-)
-		cerr << "ERROR: Corrupt block-chain! Delete your block-chain DB and restart." << endl;
-		exit(1);
-	}
-}
-
-u256 State::playbackRaw(bytesConstRef _block, BlockInfo const& _grandParent, bool _fullCommit)
-{
-	// m_currentBlock is assumed to be prepopulated.
+#if !RELEASE
+	BlockInfo bi(_block);
+	assert(m_previousBlock.hash == bi.parentHash);
+	assert(m_currentBlock.parentHash == bi.parentHash);
+	assert(rootHash() == m_previousBlock.stateRoot);
+#endif
 
 	if (m_currentBlock.parentHash != m_previousBlock.hash)
 		throw InvalidParentHash();
@@ -503,15 +545,12 @@ u256 State::playbackRaw(bytesConstRef _block, BlockInfo const& _grandParent, boo
 		}
 		if (tr[2].toInt<u256>() != gasUsed())
 			throw InvalidTransactionGasUsed();
-		if (_fullCommit)
-		{
-			bytes k = rlp(i);
-			transactionManifest.insert(&k, tr.data());
-		}
+		bytes k = rlp(i);
+		transactionManifest.insert(&k, tr.data());
 		++i;
 	}
 
-	if (transactionManifest.root() != m_currentBlock.transactionsRoot)
+	if (m_currentBlock.transactionsRoot && transactionManifest.root() != m_currentBlock.transactionsRoot)
 	{
 		cwarn << "Bad transactions state root!";
 		throw InvalidTransactionStateRoot();
@@ -521,7 +560,6 @@ u256 State::playbackRaw(bytesConstRef _block, BlockInfo const& _grandParent, boo
 	u256 tdIncrease = m_currentBlock.difficulty;
 
 	// Check uncles & apply their rewards to state.
-	// TODO: Check for uniqueness of uncles.
 	set<h256> nonces = { m_currentBlock.nonce };
 	Addresses rewarded;
 	for (auto const& i: RLP(_block)[2])
@@ -545,7 +583,7 @@ u256 State::playbackRaw(bytesConstRef _block, BlockInfo const& _grandParent, boo
 	commit();
 
 	// Hash the state trie and check against the state_root hash in m_currentBlock.
-	if (m_currentBlock.stateRoot != rootHash())
+	if (m_currentBlock.stateRoot != m_previousBlock.stateRoot && m_currentBlock.stateRoot != rootHash())
 	{
 		cwarn << "Bad state root!";
 		cnote << "Given to be:" << m_currentBlock.stateRoot;
@@ -558,6 +596,11 @@ u256 State::playbackRaw(bytesConstRef _block, BlockInfo const& _grandParent, boo
 		throw InvalidStateRoot();
 	}
 
+	return tdIncrease;
+}
+
+void State::cleanup(bool _fullCommit)
+{
 	if (_fullCommit)
 	{
 		paranoia("immediately before database commit", true);
@@ -574,8 +617,6 @@ u256 State::playbackRaw(bytesConstRef _block, BlockInfo const& _grandParent, boo
 	}
 
 	resetCurrent();
-
-	return tdIncrease;
 }
 
 void State::uncommitToMine()
@@ -614,7 +655,8 @@ bool State::amIJustParanoid(BlockChain const& _bc)
 		cnote << "PARANOIA root:" << s.rootHash();
 		s.m_currentBlock.populate(&block.out(), false);	// don't check nonce for this since we haven't mined it yet.
 		s.m_currentBlock.verifyInternals(&block.out());
-		s.playbackRaw(&block.out(), BlockInfo(), false);
+		s.enact(&block.out(), BlockInfo());
+		s.cleanup(false);
 		return true;
 	}
 	catch (Exception const& e)
@@ -813,7 +855,7 @@ u256 State::storage(Address _id, u256 _memory) const
 		return mit->second;
 
 	// Not in the storage cache - go to the DB.
-	TrieDB<h256, OverlayDB> memdb(const_cast<OverlayDB*>(&m_db), it->second.oldRoot());			// promise we won't change the overlay! :)
+	TrieDB<h256, OverlayDB> memdb(const_cast<OverlayDB*>(&m_db), it->second.baseRoot());			// promise we won't change the overlay! :)
 	string payload = memdb.at(_memory);
 	u256 ret = payload.size() ? RLP(payload).toInt<u256>() : 0;
 	it->second.setStorage(_memory, ret);
@@ -829,9 +871,9 @@ map<u256, u256> State::storage(Address _id) const
 	if (it != m_cache.end())
 	{
 		// Pull out all values from trie storage.
-		if (it->second.oldRoot())
+		if (it->second.baseRoot())
 		{
-			TrieDB<h256, OverlayDB> memdb(const_cast<OverlayDB*>(&m_db), it->second.oldRoot());		// promise we won't alter the overlay! :)
+			TrieDB<h256, OverlayDB> memdb(const_cast<OverlayDB*>(&m_db), it->second.baseRoot());		// promise we won't alter the overlay! :)
 			for (auto const& i: memdb)
 				ret[i.first] = RLP(i.second).toInt<u256>();
 		}

libethereum/State.h

@@ -113,6 +113,9 @@ public:
 	/// Construct state object.
 	State(Address _coinbaseAddress = Address(), OverlayDB const& _db = OverlayDB());
 
+	/// Construct state object from arbitrary point in blockchain.
+	State(OverlayDB const& _db, BlockChain const& _bc, h256 _hash);
+
 	/// Copy state object.
 	State(State const& _s);
 
@@ -127,6 +130,7 @@ public:
 	/// Open a DB - useful for passing into the constructor & keeping for other states that are necessary.
 	static OverlayDB openDB(std::string _path, bool _killExisting = false);
 	static OverlayDB openDB(bool _killExisting = false) { return openDB(std::string(), _killExisting); }
+	OverlayDB const& db() const { return m_db; }
 
 	/// @returns the set containing all addresses currently in use in Ethereum.
 	std::map<Address, u256> addresses() const;
@@ -154,13 +158,6 @@ public:
 	/// Only valid after mine() returns true.
 	bytes const& blockData() const { return m_currentBytes; }
 
-	/// Sync our state with the block chain.
-	/// This basically involves wiping ourselves if we've been superceded and rebuilding from the transaction queue.
-	bool sync(BlockChain const& _bc);
-
-	/// Sync with the block chain, but rather than synching to the latest block, instead sync to the given block.
-	bool sync(BlockChain const& _bc, h256 _blockHash);
-
 	// TODO: Cleaner interface.
 	/// Sync our transactions, killing those from the queue that we have and assimilating those that we don't.
 	/// @returns true if we uncommitted from mining during the operation.
@@ -232,11 +229,11 @@ public:
 	/// If (_i == pending().size()) returns the final state of the block, prior to rewards.
 	State fromPending(unsigned _i) const;
 
-	/// Execute all transactions within a given block.
-	/// @returns the additional total difficulty.
-	/// If the _grandParent is passed, it will check the validity of each of the uncles.
-	/// This might throw.
-	u256 playback(bytesConstRef _block, BlockInfo const& _bi, BlockInfo const& _parent, BlockInfo const& _grandParent, bool _fullCommit);
+	/// @returns the StateDiff caused by the pending transaction of index @a _i.
+	StateDiff pendingDiff(unsigned _i) const { return fromPending(_i).diff(fromPending(_i + 1)); }
+
+	/// @return the difference between this state (origin) and @a _c (destination).
+	StateDiff diff(State const& _c) const;
 
 	/// Get the fee associated for a transaction with the given data.
 	u256 txGas(uint _dataCount, u256 _gas = 0) const { return c_txDataGas * _dataCount + c_txGas + _gas; }
@@ -247,8 +244,26 @@ public:
 	/// Get the fee associated for a normal transaction.
 	u256 callGas(uint _dataCount, u256 _gas = 0) const { return txGas(_dataCount, _gas); }
 
-	/// @return the difference between this state (origin) and @a _c (destination).
-	StateDiff diff(State const& _c) const;
+	/// Sync our state with the block chain.
+	/// This basically involves wiping ourselves if we've been superceded and rebuilding from the transaction queue.
+	bool sync(BlockChain const& _bc);
+
+	/// Sync with the block chain, but rather than synching to the latest block, instead sync to the given block.
+	bool sync(BlockChain const& _bc, h256 _blockHash, BlockInfo const& _bi = BlockInfo());
+
+	/// Execute all transactions within a given block.
+	/// @warning We must already have been sync()ed with said block.
+	/// @returns the additional total difficulty.
+	/// If the @a _grandParent is passed, it will check the validity of each of the uncles.
+	/// @throws if there are any validation errors.
+	u256 playback(bytesConstRef _block, BlockInfo const& _bi, BlockInfo const& _parent, BlockInfo const& _grandParent = BlockInfo());
+
+	u256 enactOn(bytesConstRef _block, BlockInfo const& _bi, BlockChain const& _bc);
+
+	/// Returns back to a pristine state after having done a playback.
+	/// @arg _fullCommit if true flush everything out to disk. If false, this effectively only validates
+	/// the block since all state changes are ultimately reversed.
+	void cleanup(bool _fullCommit);
 
 private:
 	/// Undo the changes to the state for committing to mine.
@@ -266,13 +281,9 @@ private:
 	/// Commit all changes waiting in the address cache to the DB.
 	void commit();
 
-	/// Execute the given block on our previous block. This will set up m_currentBlock first, then call the other playback().
-	/// Any failure will be critical.
-	u256 trustedPlayback(bytesConstRef _block, bool _fullCommit);
-
 	/// Execute the given block, assuming it corresponds to m_currentBlock. If _grandParent is passed, it will be used to check the uncles.
 	/// Throws on failure.
-	u256 playbackRaw(bytesConstRef _block, BlockInfo const& _grandParent, bool _fullCommit);
+	u256 enact(bytesConstRef _block, BlockInfo const& _grandParent = BlockInfo());
 
 	// Two priviledged entry points for transaction processing used by the VM (these don't get added to the Transaction lists):
 	// We assume all instrinsic fees are paid up before this point.
@@ -342,10 +353,10 @@ void commit(std::map<Address, AddressState> const& _cache, DB& _db, TrieDB<Addre
 			s << i.second.nonce() << i.second.balance();
 
 			if (i.second.storage().empty())
-				s.append(i.second.oldRoot(), false, true);
+				s.append(i.second.baseRoot(), false, true);
 			else
 			{
-				TrieDB<h256, DB> storageDB(&_db, i.second.oldRoot());
+				TrieDB<h256, DB> storageDB(&_db, i.second.baseRoot());
 				for (auto const& j: i.second.storage())
 					if (j.second)
 						storageDB.insert(j.first, rlp(j.second));