core/state: implement reverts by journaling all changes

This commit replaces the deep-copy based state revert mechanism with a
linear complexity journal. This commit also hides several internal
StateDB methods to limit the number of ways in which calling code can
use the journal incorrectly.

As usual consultation and bug fixes to the initial implementation were
provided by @karalabe, @obscuren and @Arachnid. Thank you!

1 files changed, 14 insertions, 8 deletions

diff --git a/core/state/state_test.go b/core/state/state_test.go
index 7b9b39e06..b86d8b140 100644
--- a/core/state/state_test.go
+++ b/core/state/state_test.go
@@ -46,8 +46,8 @@ func (s *StateSuite) TestDump(c *checker.C) {
 	obj3.SetBalance(big.NewInt(44))
 
 	// write some of them to the trie
-	s.state.UpdateStateObject(obj1)
-	s.state.UpdateStateObject(obj2)
+	s.state.updateStateObject(obj1)
+	s.state.updateStateObject(obj2)
 	s.state.Commit()
 
 	// check that dump contains the state objects that are in trie
@@ -116,12 +116,12 @@ func (s *StateSuite) TestSnapshot(c *checker.C) {
 	// set initial state object value
 	s.state.SetState(stateobjaddr, storageaddr, data1)
 	// get snapshot of current state
-	snapshot := s.state.Copy()
+	snapshot := s.state.Snapshot()
 
 	// set new state object value
 	s.state.SetState(stateobjaddr, storageaddr, data2)
 	// restore snapshot
-	s.state.Set(snapshot)
+	s.state.RevertToSnapshot(snapshot)
 
 	// get state storage value
 	res := s.state.GetState(stateobjaddr, storageaddr)
@@ -129,6 +129,12 @@ func (s *StateSuite) TestSnapshot(c *checker.C) {
 	c.Assert(data1, checker.DeepEquals, res)
 }
 
+func TestSnapshotEmpty(t *testing.T) {
+	db, _ := ethdb.NewMemDatabase()
+	state, _ := New(common.Hash{}, db)
+	state.RevertToSnapshot(state.Snapshot())
+}
+
 // use testing instead of checker because checker does not support
 // printing/logging in tests (-check.vv does not work)
 func TestSnapshot2(t *testing.T) {
@@ -152,7 +158,7 @@ func TestSnapshot2(t *testing.T) {
 	so0.SetCode(crypto.Keccak256Hash([]byte{'c', 'a', 'f', 'e'}), []byte{'c', 'a', 'f', 'e'})
 	so0.remove = false
 	so0.deleted = false
-	state.SetStateObject(so0)
+	state.setStateObject(so0)
 
 	root, _ := state.Commit()
 	state.Reset(root)
@@ -164,15 +170,15 @@ func TestSnapshot2(t *testing.T) {
 	so1.SetCode(crypto.Keccak256Hash([]byte{'c', 'a', 'f', 'e', '2'}), []byte{'c', 'a', 'f', 'e', '2'})
 	so1.remove = true
 	so1.deleted = true
-	state.SetStateObject(so1)
+	state.setStateObject(so1)
 
 	so1 = state.GetStateObject(stateobjaddr1)
 	if so1 != nil {
 		t.Fatalf("deleted object not nil when getting")
 	}
 
-	snapshot := state.Copy()
-	state.Set(snapshot)
+	snapshot := state.Snapshot()
+	state.RevertToSnapshot(snapshot)
 
 	so0Restored := state.GetStateObject(stateobjaddr0)
 	// Update lazily-loaded values before comparing.