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/state/state_object.go

@@ -66,6 +66,7 @@ func (self Storage) Copy() Storage {
 type StateObject struct {
 	address common.Address // Ethereum address of this account
 	data    Account
+	db      *StateDB
 
 	// DB error.
 	// State objects are used by the consensus core and VM which are
@@ -99,15 +100,15 @@ type Account struct {
 	CodeHash []byte
 }
 
-// NewObject creates a state object.
-func NewObject(address common.Address, data Account, onDirty func(addr common.Address)) *StateObject {
+// newObject creates a state object.
+func newObject(db *StateDB, address common.Address, data Account, onDirty func(addr common.Address)) *StateObject {
 	if data.Balance == nil {
 		data.Balance = new(big.Int)
 	}
 	if data.CodeHash == nil {
 		data.CodeHash = emptyCodeHash
 	}
-	return &StateObject{address: address, data: data, cachedStorage: make(Storage), dirtyStorage: make(Storage), onDirty: onDirty}
+	return &StateObject{db: db, address: address, data: data, cachedStorage: make(Storage), dirtyStorage: make(Storage), onDirty: onDirty}
 }
 
 // EncodeRLP implements rlp.Encoder.
@@ -122,7 +123,7 @@ func (self *StateObject) setError(err error) {
 	}
 }
 
-func (self *StateObject) MarkForDeletion() {
+func (self *StateObject) markForDeletion() {
 	self.remove = true
 	if self.onDirty != nil {
 		self.onDirty(self.Address())
@@ -163,7 +164,16 @@ func (self *StateObject) GetState(db trie.Database, key common.Hash) common.Hash
 }
 
 // SetState updates a value in account storage.
-func (self *StateObject) SetState(key, value common.Hash) {
+func (self *StateObject) SetState(db trie.Database, key, value common.Hash) {
+	self.db.journal = append(self.db.journal, storageChange{
+		account:  &self.address,
+		key:      key,
+		prevalue: self.GetState(db, key),
+	})
+	self.setState(key, value)
+}
+
+func (self *StateObject) setState(key, value common.Hash) {
 	self.cachedStorage[key] = value
 	self.dirtyStorage[key] = value
 
@@ -189,7 +199,7 @@ func (self *StateObject) updateTrie(db trie.Database) {
 }
 
 // UpdateRoot sets the trie root to the current root hash of
-func (self *StateObject) UpdateRoot(db trie.Database) {
+func (self *StateObject) updateRoot(db trie.Database) {
 	self.updateTrie(db)
 	self.data.Root = self.trie.Hash()
 }
@@ -232,6 +242,14 @@ func (c *StateObject) SubBalance(amount *big.Int) {
 }
 
 func (self *StateObject) SetBalance(amount *big.Int) {
+	self.db.journal = append(self.db.journal, balanceChange{
+		account: &self.address,
+		prev:    new(big.Int).Set(self.data.Balance),
+	})
+	self.setBalance(amount)
+}
+
+func (self *StateObject) setBalance(amount *big.Int) {
 	self.data.Balance = amount
 	if self.onDirty != nil {
 		self.onDirty(self.Address())
@@ -242,8 +260,8 @@ func (self *StateObject) SetBalance(amount *big.Int) {
 // Return the gas back to the origin. Used by the Virtual machine or Closures
 func (c *StateObject) ReturnGas(gas, price *big.Int) {}
 
-func (self *StateObject) Copy(db trie.Database, onDirty func(addr common.Address)) *StateObject {
-	stateObject := NewObject(self.address, self.data, onDirty)
+func (self *StateObject) deepCopy(db *StateDB, onDirty func(addr common.Address)) *StateObject {
+	stateObject := newObject(db, self.address, self.data, onDirty)
 	stateObject.trie = self.trie
 	stateObject.code = self.code
 	stateObject.dirtyStorage = self.dirtyStorage.Copy()
@@ -280,6 +298,16 @@ func (self *StateObject) Code(db trie.Database) []byte {
 }
 
 func (self *StateObject) SetCode(codeHash common.Hash, code []byte) {
+	prevcode := self.Code(self.db.db)
+	self.db.journal = append(self.db.journal, codeChange{
+		account:  &self.address,
+		prevhash: self.CodeHash(),
+		prevcode: prevcode,
+	})
+	self.setCode(codeHash, code)
+}
+
+func (self *StateObject) setCode(codeHash common.Hash, code []byte) {
 	self.code = code
 	self.data.CodeHash = codeHash[:]
 	self.dirtyCode = true
@@ -290,6 +318,14 @@ func (self *StateObject) SetCode(codeHash common.Hash, code []byte) {
 }
 
 func (self *StateObject) SetNonce(nonce uint64) {
+	self.db.journal = append(self.db.journal, nonceChange{
+		account: &self.address,
+		prev:    self.data.Nonce,
+	})
+	self.setNonce(nonce)
+}
+
+func (self *StateObject) setNonce(nonce uint64) {
 	self.data.Nonce = nonce
 	if self.onDirty != nil {
 		self.onDirty(self.Address())
@@ -322,7 +358,7 @@ func (self *StateObject) ForEachStorage(cb func(key, value common.Hash) bool) {
 		cb(h, value)
 	}
 
-	it := self.trie.Iterator()
+	it := self.getTrie(self.db.db).Iterator()
 	for it.Next() {
 		// ignore cached values
 		key := common.BytesToHash(self.trie.GetKey(it.Key))