From 1f1ea18b5414bea22332bb4fce53cc95b5c6a07d Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Tue, 4 Oct 2016 12:36:02 +0200
Subject: 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!
---
 core/vm/environment.go | 4 ++--
 core/vm/jit_test.go    | 4 ++--
 core/vm/runtime/env.go | 8 ++++----
 3 files changed, 8 insertions(+), 8 deletions(-)

(limited to 'core/vm')

diff --git a/core/vm/environment.go b/core/vm/environment.go
index daf6fb90d..1038e69d5 100644
--- a/core/vm/environment.go
+++ b/core/vm/environment.go
@@ -36,9 +36,9 @@ type Environment interface {
 	// The state database
 	Db() Database
 	// Creates a restorable snapshot
-	MakeSnapshot() Database
+	SnapshotDatabase() int
 	// Set database to previous snapshot
-	SetSnapshot(Database)
+	RevertToSnapshot(int)
 	// Address of the original invoker (first occurrence of the VM invoker)
 	Origin() common.Address
 	// The block number this VM is invoked on
diff --git a/core/vm/jit_test.go b/core/vm/jit_test.go
index e6922aeb7..a6de710e1 100644
--- a/core/vm/jit_test.go
+++ b/core/vm/jit_test.go
@@ -179,8 +179,8 @@ func (self *Env) BlockNumber() *big.Int  { return big.NewInt(0) }
 
 //func (self *Env) PrevHash() []byte      { return self.parent }
 func (self *Env) Coinbase() common.Address { return common.Address{} }
-func (self *Env) MakeSnapshot() Database   { return nil }
-func (self *Env) SetSnapshot(Database)     {}
+func (self *Env) SnapshotDatabase() int    { return 0 }
+func (self *Env) RevertToSnapshot(int)     {}
 func (self *Env) Time() *big.Int           { return big.NewInt(time.Now().Unix()) }
 func (self *Env) Difficulty() *big.Int     { return big.NewInt(0) }
 func (self *Env) Db() Database             { return nil }
diff --git a/core/vm/runtime/env.go b/core/vm/runtime/env.go
index a4793c98f..59fbaa792 100644
--- a/core/vm/runtime/env.go
+++ b/core/vm/runtime/env.go
@@ -86,11 +86,11 @@ func (self *Env) SetDepth(i int) { self.depth = i }
 func (self *Env) CanTransfer(from common.Address, balance *big.Int) bool {
 	return self.state.GetBalance(from).Cmp(balance) >= 0
 }
-func (self *Env) MakeSnapshot() vm.Database {
-	return self.state.Copy()
+func (self *Env) SnapshotDatabase() int {
+	return self.state.Snapshot()
 }
-func (self *Env) SetSnapshot(copy vm.Database) {
-	self.state.Set(copy.(*state.StateDB))
+func (self *Env) RevertToSnapshot(snapshot int) {
+	self.state.RevertToSnapshot(snapshot)
 }
 
 func (self *Env) Transfer(from, to vm.Account, amount *big.Int) {
-- 
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