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, 117 insertions, 0 deletions

diff --git a/core/state/journal.go b/core/state/journal.go
new file mode 100644
index 000000000..540ade6fb
--- /dev/null
+++ b/core/state/journal.go
@@ -0,0 +1,117 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package state
+
+import (
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+type journalEntry interface {
+	undo(*StateDB)
+}
+
+type journal []journalEntry
+
+type (
+	// Changes to the account trie.
+	createObjectChange struct {
+		account *common.Address
+	}
+	resetObjectChange struct {
+		prev *StateObject
+	}
+	deleteAccountChange struct {
+		account     *common.Address
+		prev        bool // whether account had already suicided
+		prevbalance *big.Int
+	}
+
+	// Changes to individual accounts.
+	balanceChange struct {
+		account *common.Address
+		prev    *big.Int
+	}
+	nonceChange struct {
+		account *common.Address
+		prev    uint64
+	}
+	storageChange struct {
+		account       *common.Address
+		key, prevalue common.Hash
+	}
+	codeChange struct {
+		account            *common.Address
+		prevcode, prevhash []byte
+	}
+
+	// Changes to other state values.
+	refundChange struct {
+		prev *big.Int
+	}
+	addLogChange struct {
+		txhash common.Hash
+	}
+)
+
+func (ch createObjectChange) undo(s *StateDB) {
+	s.GetStateObject(*ch.account).deleted = true
+	delete(s.stateObjects, *ch.account)
+	delete(s.stateObjectsDirty, *ch.account)
+}
+
+func (ch resetObjectChange) undo(s *StateDB) {
+	s.setStateObject(ch.prev)
+}
+
+func (ch deleteAccountChange) undo(s *StateDB) {
+	obj := s.GetStateObject(*ch.account)
+	if obj != nil {
+		obj.remove = ch.prev
+		obj.setBalance(ch.prevbalance)
+	}
+}
+
+func (ch balanceChange) undo(s *StateDB) {
+	s.GetStateObject(*ch.account).setBalance(ch.prev)
+}
+
+func (ch nonceChange) undo(s *StateDB) {
+	s.GetStateObject(*ch.account).setNonce(ch.prev)
+}
+
+func (ch codeChange) undo(s *StateDB) {
+	s.GetStateObject(*ch.account).setCode(common.BytesToHash(ch.prevhash), ch.prevcode)
+}
+
+func (ch storageChange) undo(s *StateDB) {
+	s.GetStateObject(*ch.account).setState(ch.key, ch.prevalue)
+}
+
+func (ch refundChange) undo(s *StateDB) {
+	s.refund = ch.prev
+}
+
+func (ch addLogChange) undo(s *StateDB) {
+	logs := s.logs[ch.txhash]
+	if len(logs) == 1 {
+		delete(s.logs, ch.txhash)
+	} else {
+		s.logs[ch.txhash] = logs[:len(logs)-1]
+	}
+}