.

wcfs/internal/xbtree/δbtail.go

@@ -49,9 +49,11 @@ type Key    = int64
 //
 // XXX incremental; not full coverage
 // XXX concurrency safety
+//
+// XXX see also zodb.ΔTail .
 type ΔTail struct {
-	//at // = head
-	δZtail *zodb.ΔTail
+	δBtail []ΔRevEntry // BTree changes; Covers keys ∈ tracket subset
+	δZtail *zodb.ΔTail // raw ZODB changes; Kept to rebuild δBtail after new Track
 
 	// XXX or ask client provide db on every call?
 	db     *zodb.DB    // to open connections to load new/old tree|buckets
@@ -73,6 +75,30 @@ type ΔTree struct {
 	Keyv []Key
 }
 
+// NewΔTail creats new ΔTail object.
+//
+// Initial tracked set is empty.
+// Initial coverage is (at₀, at₀].
+func NewΔTail(at0 zodb.Tid) *ΔTail {
+	return &ΔTail{
+		δZtail: zodb.NewΔTail(at0),
+		root:   make(map[zodb.Oid]SetTree),
+	}
+}
+
+// Head is similar to zodb.ΔTail.Head .		XXX ok?
+func (δb *ΔTail) Head() zodb.Tid {
+	return δb.δZtail.Head()
+}
+
+// Tail is similar to zodb.ΔTail.Tail .		XXX ok?
+func (δb *ΔTail) Tail() zodb.Tid {
+	return δb.δZtail.Tail()
+}
+
+// XXX SliceByRev?
+// XXX ForgetPast
+
 // Track adds tree path to tracked set.
 //
 // XXX tailv is rebuild to also include keys corresponding to added nodes.