prove_transaction function on state

ethcore/src/client/client.rs

@@ -1884,27 +1884,23 @@ impl ProvingBlockChainClient for Client {
 	}
 
 	fn prove_transaction(&self, transaction: SignedTransaction, id: BlockId) -> Option<(Bytes, Vec<DBValue>)> {
-		let (state, mut env_info) = match (self.state_at(id), self.env_info(id)) {
+		let (header, mut env_info) = match (self.block_header(id), self.env_info(id)) {
 			(Some(s), Some(e)) => (s, e),
 			_ => return None,
 		};
 
 		env_info.gas_limit = transaction.gas.clone();
 		let mut jdb = self.state_db.lock().journal_db().boxed_clone();
-		let backend = state::backend::Proving::new(jdb.as_hashdb_mut());
 
-		let mut state = state.replace_backend(backend);
-		let options = TransactOptions { tracing: false, vm_tracing: false, check_nonce: false };
-		let res = Executive::new(&mut state, &env_info, &*self.engine).transact(&transaction, options);
-
-		match res {
-			Err(ExecutionError::Internal(_)) => None,
-			Err(e) => {
-				trace!(target: "client", "Proved call failed: {}", e);
-				Some((Vec::new(), state.drop().1.extract_proof()))
-			}
-			Ok(res) => Some((res.output, state.drop().1.extract_proof())),
-		}
+		state::prove_transaction(
+			jdb.as_hashdb_mut(),
+			header.state_root().clone(),
+			&transaction,
+			&*self.engine,
+			&env_info,
+			self.factories.clone(),
+			false,
+		)
 	}
 }
 

ethcore/src/spec/spec.rs

@@ -32,7 +32,6 @@ use factory::Factories;
 use header::{BlockNumber, Header};
 use pod_state::*;
 use rlp::{Rlp, RlpStream};
-use state_db::StateDB;
 use state::{Backend, State, Substate};
 use state::backend::Basic as BasicBackend;
 use trace::{NoopTracer, NoopVMTracer};
@@ -421,7 +420,7 @@ impl Spec {
 	}
 
 	/// Ensure that the given state DB has the trie nodes in for the genesis state.
-	pub fn ensure_db_good(&self, db: StateDB, factories: &Factories) -> Result<StateDB, Error> {
+	pub fn ensure_db_good<T: Backend>(&self, db: T, factories: &Factories) -> Result<T, Error> {
 		if db.as_hashdb().contains(&self.state_root()) {
 			return Ok(db)
 		}

ethcore/src/state/mod.rs

@@ -209,6 +209,43 @@ pub fn check_proof(
 	}
 }
 
+/// Prove a transaction on the given state.
+/// Returns `None` when the transacion could not be proved,
+/// and a proof otherwise.
+pub fn prove_transaction<H: AsHashDB + Send + Sync>(
+	db: H,
+	root: H256,
+	transaction: &SignedTransaction,
+	engine: &Engine,
+	env_info: &EnvInfo,
+	factories: Factories,
+	virt: bool,
+) -> Option<(Bytes, Vec<DBValue>)> {
+	use self::backend::Proving;
+
+	let backend = Proving::new(db);
+	let res = State::from_existing(
+		backend,
+		root,
+		engine.account_start_nonce(env_info.number),
+		factories,
+	);
+
+	let mut state = match res {
+		Ok(state) => state,
+		Err(_) => return None,
+	};
+
+	match state.execute(env_info, engine, transaction, false, virt) {
+		Err(ExecutionError::Internal(_)) => None,
+		Err(e) => {
+			trace!(target: "state", "Proved call failed: {}", e);
+			Some((Vec::new(), state.drop().1.extract_proof()))
+		}
+		Ok(res) => Some((res.output, state.drop().1.extract_proof())),
+	}
+}
+
 /// Representation of the entire state of all accounts in the system.
 ///
 /// `State` can work together with `StateDB` to share account cache.