move stats and inbound to features directory

features/stats/stats.go

@@ -0,0 +1,26 @@
+package stats
+
+import "v2ray.com/core/features"
+
+type Counter interface {
+	Value() int64
+	Set(int64) int64
+	Add(int64) int64
+}
+
+type Manager interface {
+	features.Feature
+
+	RegisterCounter(string) (Counter, error)
+	GetCounter(string) Counter
+}
+
+// GetOrRegisterCounter tries to get the StatCounter first. If not exist, it then tries to create a new counter.
+func GetOrRegisterCounter(m Manager, name string) (Counter, error) {
+	counter := m.GetCounter(name)
+	if counter != nil {
+		return counter, nil
+	}
+
+	return m.RegisterCounter(name)
+}