.

go/neo/xneo/statelog.go

@@ -20,20 +20,23 @@
 package xneo
 // transactional log of states
 
-// XXX ...
+// State represents state of a cluster.
 type State struct {
+	// XXX +transaction ID?
+
 	NodeTab      *NodeTable         // nodes in the cluster
 	PartTab      *PartitionTable    // on which nodes which data is located
 	ClusterState proto.ClusterState // code for cluster state
 }
 
-type StateSnapshot interface {
-	NodeTab()      RONodeTable
-	PartTab()      ROPartitionTable
+// StateRO provides read-only access to a State.
+type StateRO interface {
+	NodeTab()      NodeTableRO
+	PartTab()      PartitionTableRO
 	ClusterState() proto.ClusterState
 }
 
-// XXX transactional journal ...
+// StateLog is transactional journal of State changes.
 type StateLog struct {
 	mu   sync.Mutex
 	head *State
@@ -41,7 +44,7 @@ type StateLog struct {
 
 
 // ReadHead returns state from head of the log.
-func (l *StateLog) ReadHead() StateSnapshot {
+func (l *StateLog) ReadHead() StateRO {
 	l.mu.Lock()
 	defer l.mu.Unlock()
 	return l.head
@@ -55,3 +58,13 @@ func (l *StateLog) CommitUpdate(δf func(*State)) {
 	δf(s)
 	l.head = s
 }
+
+
+// Clone creates new instance of State initialized with previous content.
+func (s *State) Clone() *State {
+	return &State{
+		NodeTab:      s.NodeTab.Clone(),
+		PartTab:      s.PartTab.Clone(),
+		ClusterState: s.ClusterState,
+	}
+}