Merge pull request #1217 from rphmeier/state_at_state_root

Verify the state root exists before creating a State

ethcore/src/client/client.rs

@@ -371,9 +371,27 @@ impl<V> Client<V> where V: Verifier {
 			return Some(self.state())
 		}
 
-		self.block_header(id).map(|header| {
+		let block_number = match self.block_number(id.clone()) {
+			Some(num) => num,
+			None => return None,
+		};
+
+		self.block_header(id).and_then(|header| {
 			let db = self.state_db.lock().unwrap().boxed_clone();
-			State::from_existing(db, HeaderView::new(&header).state_root(), self.engine.account_start_nonce())
+
+			// early exit for pruned blocks
+			if db.is_pruned() && self.chain.best_block_number() >= block_number + HISTORY {
+				return None;
+			}
+
+			let root = HeaderView::new(&header).state_root();
+
+			// TODO [rob]: refactor State::from_existing so we avoid doing redundant lookups.
+			if !db.contains(&root) {
+				return None;
+			}
+
+			Some(State::from_existing(db, root, self.engine.account_start_nonce()))
 		})
 	}
 

util/src/journaldb/archivedb.rs

@@ -175,6 +175,8 @@ impl JournalDB for ArchiveDB {
 	fn state(&self, id: &H256) -> Option<Bytes> {
 		self.backing.get_by_prefix(&id.bytes()[0..12]).and_then(|b| Some(b.to_vec()))
 	}
+
+	fn is_pruned(&self) -> bool { false }
 }
 
 #[cfg(test)]

util/src/journaldb/traits.rs

@@ -42,4 +42,7 @@ pub trait JournalDB : HashDB + Send + Sync {
 	fn state(&self, _id: &H256) -> Option<Bytes> {
 		None
 	}
+
+	/// Whether this database is pruned.
+	fn is_pruned(&self) -> bool { true }
 }

util/src/trie/triedb.rs

@@ -59,7 +59,7 @@ impl<'db> TrieDB<'db> {
 	/// Create a new trie with the backing database `db` and `root`
 	/// Panics, if `root` does not exist
 	pub fn new(db: &'db HashDB, root: &'db H256) -> Self {
-		if !db.exists(root) {
+		if !db.contains(root) {
 			flushln!("TrieDB::new({}): Trie root not found!", root);
 			panic!("Trie root not found!");
 		}