State snapshotting

4 files changed, 65 insertions, 6 deletions

diff --git a/ethchain/state.go b/ethchain/state.go
index 6ec6916f4..e209e0e2f 100644
--- a/ethchain/state.go
+++ b/ethchain/state.go
@@ -99,7 +99,21 @@ func (s *State) Cmp(other *State) bool {
 }
 
 func (s *State) Copy() *State {
-	return NewState(s.trie.Copy())
+	state := NewState(s.trie.Copy())
+	for k, subState := range s.states {
+		state.states[k] = subState.Copy()
+	}
+
+	return state
+}
+
+func (s *State) Snapshot() *State {
+	return s.Copy()
+}
+
+func (s *State) Revert(snapshot *State) {
+	s.trie = snapshot.trie
+	s.states = snapshot.states
 }
 
 func (s *State) Put(key, object []byte) {
diff --git a/ethchain/state_object.go b/ethchain/state_object.go
index 4d615e2fe..3e9c6df40 100644
--- a/ethchain/state_object.go
+++ b/ethchain/state_object.go
@@ -81,12 +81,17 @@ func (c *StateObject) SetStorage(num *big.Int, val *ethutil.Value) {
 	c.SetAddr(addr, val)
 }
 
-func (c *StateObject) GetMem(num *big.Int) *ethutil.Value {
+func (c *StateObject) GetStorage(num *big.Int) *ethutil.Value {
 	nb := ethutil.BigToBytes(num, 256)
 
 	return c.Addr(nb)
 }
 
+/* DEPRECATED */
+func (c *StateObject) GetMem(num *big.Int) *ethutil.Value {
+	return c.GetStorage(num)
+}
+
 func (c *StateObject) GetInstr(pc *big.Int) *ethutil.Value {
 	if int64(len(c.script)-1) < pc.Int64() {
 		return ethutil.NewValue(0)
diff --git a/ethchain/state_test.go b/ethchain/state_test.go
new file mode 100644
index 000000000..4cc3fdf75
--- /dev/null
+++ b/ethchain/state_test.go
@@ -0,0 +1,31 @@
+package ethchain
+
+import (
+	"fmt"
+	"github.com/ethereum/eth-go/ethdb"
+	"github.com/ethereum/eth-go/ethutil"
+	"testing"
+)
+
+func TestSnapshot(t *testing.T) {
+	ethutil.ReadConfig("", ethutil.LogStd, "")
+
+	db, _ := ethdb.NewMemDatabase()
+	state := NewState(ethutil.NewTrie(db, ""))
+
+	stateObject := NewContract([]byte("aa"), ethutil.Big1, ZeroHash256)
+	state.UpdateStateObject(stateObject)
+	stateObject.SetStorage(ethutil.Big("0"), ethutil.NewValue(42))
+
+	snapshot := state.Snapshot()
+
+	stateObject = state.GetStateObject([]byte("aa"))
+	stateObject.SetStorage(ethutil.Big("0"), ethutil.NewValue(43))
+
+	state.Revert(snapshot)
+
+	stateObject = state.GetStateObject([]byte("aa"))
+	if !stateObject.GetStorage(ethutil.Big("0")).Cmp(ethutil.NewValue(42)) {
+		t.Error("Expected storage 0 to be 42")
+	}
+}
diff --git a/ethchain/vm.go b/ethchain/vm.go
index e067a9c96..e025920f3 100644
--- a/ethchain/vm.go
+++ b/ethchain/vm.go
@@ -426,6 +426,10 @@ func (vm *Vm) RunClosure(closure *Closure, hook DebugHook) (ret []byte, err erro
 			value := stack.Pop()
 			size, offset := stack.Popn()
 
+			// Snapshot the current stack so we are able to
+			// revert back to it later.
+			snapshot := vm.state.Snapshot()
+
 			// Generate a new address
 			addr := ethutil.CreateAddress(closure.callee.Address(), closure.callee.N())
 			// Create a new contract
@@ -448,6 +452,9 @@ func (vm *Vm) RunClosure(closure *Closure, hook DebugHook) (ret []byte, err erro
 			closure.Script, err = closure.Call(vm, nil, hook)
 			if err != nil {
 				stack.Push(ethutil.BigFalse)
+
+				// Revert the state as it was before.
+				vm.state.Revert(snapshot)
 			} else {
 				stack.Push(ethutil.BigD(addr))
 
@@ -473,6 +480,8 @@ func (vm *Vm) RunClosure(closure *Closure, hook DebugHook) (ret []byte, err erro
 			// Get the arguments from the memory
 			args := mem.Get(inOffset.Int64(), inSize.Int64())
 
+			snapshot := vm.state.Snapshot()
+
 			// Fetch the contract which will serve as the closure body
 			contract := vm.state.GetStateObject(addr.Bytes())
 
@@ -495,14 +504,14 @@ func (vm *Vm) RunClosure(closure *Closure, hook DebugHook) (ret []byte, err erro
 				if err != nil {
 					stack.Push(ethutil.BigFalse)
 					// Reset the changes applied this object
-					//contract.State().Reset()
+					vm.state.Revert(snapshot)
 				} else {
 					stack.Push(ethutil.BigTrue)
-				}
 
-				vm.state.UpdateStateObject(contract)
+					vm.state.UpdateStateObject(contract)
 
-				mem.Set(retOffset.Int64(), retSize.Int64(), ret)
+					mem.Set(retOffset.Int64(), retSize.Int64(), ret)
+				}
 			} else {
 				ethutil.Config.Log.Debugf("Contract %x not found\n", addr.Bytes())
 				stack.Push(ethutil.BigFalse)