In-memory trie operations (#1408)

* small cleanups in trie

* Memory trie skeleton

* decode nodes from RLP

* memorytrie -> memorytriedb

* implement Trie for MemoryTrie

* partially implement insert

* implement trie insertion

* don't load whole trie into memory, lookup across memory and db

* re-implement insertion and lazily load necessary nodes from DB

* node removal w/o fixing

* reduce churn in node storage

* finish remove implementation

* committing the in-memory trie

* reload root node after commit

* generate elastic arrays when converting nodes to rlp

* port triedbmut tests over to memorytriedb, fix a few bugs.

* hash count and dirty flag

* initial attempt for node inspection

* back to skeleton

* inspection framework

* implement insertion

* no panic paths in insert

* implement deletion without fixing

* node fixing

* commit nodes to db

* tracing targets and bugfix

* get tests to pass with a lot of tracing

* set playpen iterations to 10

* remove some tracing statements

* make TrieMut::root take &mut self

* replace triedbmut with memorytriedb

* treat empty insert value as removal

* add test for null insert

* fix some style concerns

* trie: use nodehandle for root_node, minor cleanup

util/src/trie/fatdbmut.rs

@@ -54,10 +54,14 @@ impl<'db> FatDBMut<'db> {
 }
 
 impl<'db> TrieMut for FatDBMut<'db> {
-	fn root(&self) -> &H256 {
+	fn root(&mut self) -> &H256 {
 		self.raw.root()
 	}
 
+	fn is_empty(&self) -> bool {
+		self.raw.is_empty()
+	}
+
 	fn contains(&self, key: &[u8]) -> bool {
 		self.raw.contains(&key.sha3())
 	}

util/src/trie/mod.rs

@@ -38,7 +38,6 @@ pub mod sectriedb;
 pub mod sectriedbmut;
 
 mod fatdb;
-
 mod fatdbmut;
 
 pub use self::trietraits::{Trie, TrieMut};

util/src/trie/sectriedbmut.rs

@@ -51,7 +51,13 @@ impl<'db> SecTrieDBMut<'db> {
 }
 
 impl<'db> TrieMut for SecTrieDBMut<'db> {
-	fn root(&self) -> &H256 { self.raw.root() }
+	fn root(&mut self) -> &H256 {
+		self.raw.root()
+	}
+
+	fn is_empty(&self) -> bool {
+		self.raw.is_empty()
+	}
 
 	fn contains(&self, key: &[u8]) -> bool {
 		self.raw.contains(&key.sha3())

util/src/trie/triedb.rs

@@ -88,8 +88,7 @@ impl<'db> TrieDB<'db> {
 	pub fn to_map(hashes: Vec<H256>) -> HashMap<H256, u32> {
 		let mut r: HashMap<H256, u32> = HashMap::new();
 		for h in hashes.into_iter() {
-			let c = *r.get(&h).unwrap_or(&0);
-			r.insert(h, c + 1);
+			*r.entry(h).or_insert(0) += 1;
 		}
 		r
 	}
@@ -184,7 +183,7 @@ impl<'db> TrieDB<'db> {
 
 	/// Return optional data for a key given as a `NibbleSlice`. Returns `None` if no data exists.
 	fn do_lookup<'a, 'key>(&'a self, key: &NibbleSlice<'key>) -> Option<&'a [u8]> where 'a: 'key {
-		let root_rlp = self.db.get(&self.root).expect("Trie root not found!");
+		let root_rlp = self.root_data();
 		self.get_from_node(&root_rlp, key)
 	}
 

util/src/trie/trietraits.rs

@@ -41,10 +41,10 @@ pub trait Trie {
 /// A key-value datastore implemented as a database-backed modified Merkle tree.
 pub trait TrieMut {
 	/// Return the root of the trie.
-	fn root(&self) -> &H256;
+	fn root(&mut self) -> &H256;
 
 	/// Is the trie empty?
-	fn is_empty(&self) -> bool { *self.root() == SHA3_NULL_RLP }
+	fn is_empty(&self) -> bool;
 
 	/// Does the trie contain a given key?
 	fn contains(&self, key: &[u8]) -> bool;