Trie's are no longer referenced directly but through State instead

ethchain/state.go

@@ -5,16 +5,46 @@ import (
 	"math/big"
 )
 
+// States within the ethereum protocol are used to store anything
+// within the merkle trie. States take care of caching and storing
+// nested states. It's the general query interface to retrieve:
+// * Contracts
+// * Accounts
 type State struct {
+	// The trie for this structure
 	trie *ethutil.Trie
+	// Nested states
+	states map[string]*State
 }
 
+// Create a new state from a given trie
 func NewState(trie *ethutil.Trie) *State {
-	return &State{trie: trie}
+	return &State{trie: trie, states: make(map[string]*State)}
 }
 
+// Resets the trie and all siblings
 func (s *State) Reset() {
 	s.trie.Undo()
+
+	// Reset all nested states
+	for _, state := range s.states {
+		state.Reset()
+	}
+}
+
+// Syncs the trie and all siblings
+func (s *State) Sync() {
+	s.trie.Sync()
+
+	// Sync all nested states
+	for _, state := range s.states {
+		state.Sync()
+	}
+}
+
+// Purges the current trie.
+func (s *State) Purge() int {
+	return s.trie.NewIterator().Purge()
 }
 
 func (s *State) GetContract(addr []byte) *Contract {
@@ -23,9 +53,28 @@ func (s *State) GetContract(addr []byte) *Contract {
 		return nil
 	}
 
+	// Whet get contract is called the retrieved value might
+	// be an account. The StateManager uses this to check
+	// to see if the address a tx was sent to is a contract
+	// or an account
+	value := ethutil.NewValueFromBytes([]byte(data))
+	if value.Len() == 2 {
+		return nil
+	}
+
+	// build contract
 	contract := &Contract{}
 	contract.RlpDecode([]byte(data))
 
+	// Check if there's a cached state for this contract
+	cachedState := s.states[string(addr)]
+	if cachedState != nil {
+		contract.state = cachedState
+	} else {
+		// If it isn't cached, cache the state
+		s.states[string(addr)] = contract.state
+	}
+
 	return contract
 }