added nonce, nonce_latest

ethcore/src/client/client.rs

@@ -348,7 +348,8 @@ impl<V> Client<V> where V: Verifier {
 
 	/// Attempt to get a copy of a specific block's state.
 	///
-	/// This can fail (but may not) if the DB prunes state.
+	/// This will not fail if given BlockID::Latest.
+	/// Otherwise, this can fail (but may not) if the DB prunes state.
 	pub fn state_at(&self, id: BlockID) -> Option<State> {
 		// fast path for latest state.
 		if let BlockID::Latest = id.clone() {
@@ -556,10 +557,11 @@ impl<V> BlockChainClient for Client<V> where V: Verifier {
 		Self::block_hash(&self.chain, id).and_then(|hash| self.chain.block_details(&hash)).map(|d| d.total_difficulty)
 	}
 
-	fn nonce(&self, address: &Address) -> U256 {
-		self.state().nonce(address)
+	fn nonce(&self, address: &Address, id: BlockID) -> Option<U256> {
+		self.state_at(id).map(|s| s.nonce(address))
 	}
 
+
 	fn block_hash(&self, id: BlockID) -> Option<H256> {
 		Self::block_hash(&self.chain, id)
 	}

ethcore/src/client/mod.rs

@@ -65,8 +65,15 @@ pub trait BlockChainClient : Sync + Send {
 	/// Get block total difficulty.
 	fn block_total_difficulty(&self, id: BlockID) -> Option<U256>;
 
-	/// Get address nonce.
-	fn nonce(&self, address: &Address) -> U256;
+	/// Attempt to get address nonce at given block.
+	/// May not fail on BlockID::Latest.
+	fn nonce(&self, address: &Address, id: BlockID) -> Option<U256>;
+
+	fn nonce_latest(&self, address: &Address) -> U256 {
+		self.nonce(address, BlockID::Latest)
+			.expect("nonce will return Some when given BlockID::Latest. nonce was given BlockID::Latest. \
+			Therefore nonce has returned Some; qed")
+	}
 
 	/// Get block hash.
 	fn block_hash(&self, id: BlockID) -> Option<H256>;

ethcore/src/client/test_client.rs

@@ -245,8 +245,11 @@ impl BlockChainClient for TestBlockChainClient {
 		Self::block_hash(self, id)
 	}
 
-	fn nonce(&self, address: &Address) -> U256 {
-		self.nonces.read().unwrap().get(address).cloned().unwrap_or_else(U256::zero)
+	fn nonce(&self, address: &Address, id: BlockID) -> Option<U256> {
+		match id {
+			BlockID::Latest => Some(self.nonces.read().unwrap().get(address).cloned().unwrap_or_else(U256::zero)),
+			_ => None,
+		}
 	}
 
 	fn code(&self, address: &Address) -> Option<Bytes> {