Restore GetNodeData (#469)

* Accept GetNodeData requests

* Implement blockchain client method for node data requests

* Reuse old database read methods for node data

* fmt

* Copy & paste old tests...

* ... and make them work

* fmt

crates/ethcore/src/client/client.rs

@@ -2776,6 +2776,10 @@ impl BlockChainClient for Client {
     fn registrar_address(&self) -> Option<Address> {
         self.registrar_address.clone()
     }
+
+    fn state_data(&self, hash: &H256) -> Option<Bytes> {
+        self.state_db.read().journal_db().state(hash)
+    }
 }
 
 impl IoClient for Client {

crates/ethcore/src/client/test_client.rs

@@ -1078,6 +1078,18 @@ impl BlockChainClient for TestBlockChainClient {
     fn registrar_address(&self) -> Option<Address> {
         None
     }
+
+    fn state_data(&self, hash: &H256) -> Option<Bytes> {
+        let begins_with_f =
+            H256::from_str("f000000000000000000000000000000000000000000000000000000000000000")
+                .unwrap();
+        if *hash > begins_with_f {
+            let mut rlp = RlpStream::new();
+            rlp.append(&hash.clone());
+            return Some(rlp.out());
+        }
+        None
+    }
 }
 
 impl IoClient for TestBlockChainClient {

crates/ethcore/src/client/traits.rs

@@ -333,6 +333,9 @@ pub trait BlockChainClient:
     /// Get all possible uncle hashes for a block.
     fn find_uncles(&self, hash: &H256) -> Option<Vec<H256>>;
 
+    /// Get latest state node
+    fn state_data(&self, hash: &H256) -> Option<Bytes>;
+
     /// Get block receipts data by block header hash.
     fn block_receipts(&self, hash: &H256) -> Option<BlockReceipts>;
 

crates/ethcore/src/tests/client.rs

@@ -591,3 +591,12 @@ fn import_export_binary() {
     assert!(client.block_header(BlockId::Number(17)).is_some());
     assert!(client.block_header(BlockId::Number(16)).is_some());
 }
+
+#[test]
+fn returns_state_root_basic() {
+    let client = generate_dummy_client(6);
+    let test_spec = Spec::new_test();
+    let genesis_header = test_spec.genesis_header();
+
+    assert!(client.state_data(genesis_header.state_root()).is_some());
+}