core/state: move revision-handling into journal

core/state/journal.go

@@ -17,11 +17,19 @@
 package state
 
 import (
+	"fmt"
+	"sort"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/holiman/uint256"
 )
 
+type revision struct {
+	id           int
+	journalIndex int
+}
+
 // journalEntry is a modification entry in the state change journal that can be
 // reverted on demand.
 type journalEntry interface {
@@ -38,6 +46,9 @@ type journalEntry interface {
 type journal struct {
 	entries []journalEntry         // Current changes tracked by the journal
 	dirties map[common.Address]int // Dirty accounts and the number of changes
+
+	validRevisions []revision
+	nextRevisionId int
 }
 
 // newJournal creates a new initialized journal.
@@ -47,6 +58,40 @@ func newJournal() *journal {
 	}
 }
 
+// Reset clears the journal, after this operation the journal can be used
+// anew. It is semantically similar to calling 'newJournal', but the underlying
+// slices can be reused
+func (j *journal) Reset() {
+	j.entries = j.entries[:0]
+	j.validRevisions = j.validRevisions[:0]
+	j.dirties = make(map[common.Address]int)
+	j.nextRevisionId = 0
+}
+
+// Snapshot returns an identifier for the current revision of the state.
+func (j *journal) Snapshot() int {
+	id := j.nextRevisionId
+	j.nextRevisionId++
+	j.validRevisions = append(j.validRevisions, revision{id, j.length()})
+	return id
+}
+
+// RevertToSnapshot reverts all state changes made since the given revision.
+func (j *journal) RevertToSnapshot(revid int, s *StateDB) {
+	// Find the snapshot in the stack of valid snapshots.
+	idx := sort.Search(len(j.validRevisions), func(i int) bool {
+		return j.validRevisions[i].id >= revid
+	})
+	if idx == len(j.validRevisions) || j.validRevisions[idx].id != revid {
+		panic(fmt.Errorf("revision id %v cannot be reverted", revid))
+	}
+	snapshot := j.validRevisions[idx].journalIndex
+
+	// Replay the journal to undo changes and remove invalidated snapshots
+	j.revert(s, snapshot)
+	j.validRevisions = j.validRevisions[:idx]
+}
+
 // append inserts a new modification entry to the end of the change journal.
 func (j *journal) append(entry journalEntry) {
 	j.entries = append(j.entries, entry)

core/state/statedb.go

@@ -19,7 +19,6 @@ package state
 
 import (
 	"fmt"
-	"sort"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -42,11 +41,6 @@ const (
 	storageDeleteLimit = 512 * 1024 * 1024
 )
 
-type revision struct {
-	id           int
-	journalIndex int
-}
-
 // StateDB structs within the ethereum protocol are used to store anything
 // within the merkle trie. StateDBs take care of caching and storing
 // nested states. It's the general query interface to retrieve:
@@ -113,9 +107,7 @@ type StateDB struct {
 
 	// Journal of state modifications. This is the backbone of
 	// Snapshot and RevertToSnapshot.
-	journal        *journal
-	validRevisions []revision
-	nextRevisionId int
+	journal *journal
 
 	// Measurements gathered during execution for debugging purposes
 	AccountReads         time.Duration
@@ -774,26 +766,12 @@ func (s *StateDB) Copy() *StateDB {
 
 // Snapshot returns an identifier for the current revision of the state.
 func (s *StateDB) Snapshot() int {
-	id := s.nextRevisionId
-	s.nextRevisionId++
-	s.validRevisions = append(s.validRevisions, revision{id, s.journal.length()})
-	return id
+	return s.journal.Snapshot()
 }
 
 // RevertToSnapshot reverts all state changes made since the given revision.
 func (s *StateDB) RevertToSnapshot(revid int) {
-	// Find the snapshot in the stack of valid snapshots.
-	idx := sort.Search(len(s.validRevisions), func(i int) bool {
-		return s.validRevisions[i].id >= revid
-	})
-	if idx == len(s.validRevisions) || s.validRevisions[idx].id != revid {
-		panic(fmt.Errorf("revision id %v cannot be reverted", revid))
-	}
-	snapshot := s.validRevisions[idx].journalIndex
-
-	// Replay the journal to undo changes and remove invalidated snapshots
-	s.journal.revert(s, snapshot)
-	s.validRevisions = s.validRevisions[:idx]
+	s.journal.RevertToSnapshot(revid, s)
 }
 
 // GetRefund returns the current value of the refund counter.
@@ -924,11 +902,8 @@ func (s *StateDB) SetTxContext(thash common.Hash, ti int) {
 }
 
 func (s *StateDB) clearJournalAndRefund() {
-	if len(s.journal.entries) > 0 {
-		s.journal = newJournal()
-		s.refund = 0
-	}
-	s.validRevisions = s.validRevisions[:0] // Snapshots can be created without journal entries
+	s.journal.Reset()
+	s.refund = 0
 }
 
 // fastDeleteStorage is the function that efficiently deletes the storage trie