triedb seek and descend is not recursive

util/src/trie/triedb.rs

@@ -217,10 +217,17 @@ impl<'a> TrieDBIterator<'a> {
 		Ok(r)
 	}
 
-	fn seek_descend<'key>(&mut self, node_data: DBValue, key: &NibbleSlice<'key>) -> super::Result<()> {
+	fn seek_descend<'key>(&mut self, mut node_data: DBValue, mut key: NibbleSlice<'key>) -> super::Result<()> {
+		enum Step {
+			Descend(DBValue, usize),
+			Return,
+		}
+
+		loop {
+			let step = {
 				let node = Node::decoded(&node_data);
 				match node {
-			Node::Leaf(ref slice, _) => {
+					Node::Leaf(slice, _) => {
 						if slice == key {
 							self.trail.push(Crumb {
 								status: Status::At,
@@ -234,7 +241,7 @@ impl<'a> TrieDBIterator<'a> {
 						}
 
 						self.key_nibbles.extend(slice.iter());
-				Ok(())
+						Step::Return
 					},
 					Node::Extension(ref slice, ref item) => {
 						if key.starts_with(slice) {
@@ -244,10 +251,10 @@ impl<'a> TrieDBIterator<'a> {
 							});
 							self.key_nibbles.extend(slice.iter());
 							let data = self.db.get_raw_or_lookup(&*item)?;
-					self.seek_descend(data, &key.mid(slice.len()))
+							Step::Descend(data, slice.len())
 						} else {
 							self.descend(&node_data)?;
-					Ok(())
+							Step::Return
 						}
 					},
 					Node::Branch(ref nodes, _) => match key.is_empty() {
@@ -256,7 +263,7 @@ impl<'a> TrieDBIterator<'a> {
 								status: Status::At,
 								node: node.clone().into(),
 							});
-					Ok(())
+							Step::Return
 						},
 						false => {
 							let i = key.at(0);
@@ -266,10 +273,20 @@ impl<'a> TrieDBIterator<'a> {
 							});
 							self.key_nibbles.push(i);
 							let child = self.db.get_raw_or_lookup(&*nodes[i as usize])?;
-					self.seek_descend(child, &key.mid(1))
+							Step::Descend(child, 1)
 						}
 					},
-			_ => Ok(())
+					_ => Step::Return
+				}
+			};
+
+			match step {
+				Step::Return => return Ok(()),
+				Step::Descend(data, mid) => {
+					node_data = data;
+					key = key.mid(mid);
+				}
+			}
 		}
 	}
 
@@ -314,7 +331,7 @@ impl<'a> TrieIterator for TrieDBIterator<'a> {
 		self.trail.clear();
 		self.key_nibbles.clear();
 		let root_rlp = self.db.root_data()?;
-		self.seek_descend(root_rlp, &NibbleSlice::new(key))
+		self.seek_descend(root_rlp, NibbleSlice::new(key))
 	}
 }