.

wcfs/internal/xbtree/rangeset.go

@@ -29,13 +29,16 @@ const traceRangeSet = false
 const debugRangeSet = false
 
 // Range represents [lo,hi) Key range.
+// XXX -> KeyRange?
 type Range struct {
 	lo  Key
 	hi_ Key // NOTE _not_ hi) to avoid overflow at ∞;  hi = hi_ + 1
 }
 
 // RangeSet is set of Keys with adjacent keys coaleced into Ranges.
-// XXX -> RangedSet ?
+//
+// Zero value represents empty set.
+// XXX -> RangedSet ? RangedKeySet ? RangeKeySet?
 type RangeSet struct {
 	// TODO rework to use BTree lo->hi_ instead if in practice in treediff,
 	// and other usage places, N(ranges) turns out to be not small
@@ -347,6 +350,11 @@ func (orig *RangeSet) Clone() *RangeSet {
 	return klon
 }
 
+// Empty returns whether the set is empty.
+func (S *RangeSet) Empty() bool {
+	return len(S.rangev) == 0
+}
+
 // Equal returns whether A == B.
 func (A *RangeSet) Equal(B *RangeSet) bool {
 	if len(A.rangev) != len(B.rangev) {

wcfs/internal/xbtree/treediff.go

@@ -520,25 +520,25 @@ func diffT(ctx context.Context, A, B *Tree, δZTC SetOid, trackSet PPTreeSubSet)
 	Bv := rangeSplit{btop} // nodes expanded from B
 
 	// for phase 2:
-	Akqueue := SetKey{} // queue for keys in A to be processed for δ-	XXX -> KeyRangeSet
-	Bkqueue := SetKey{} // ----//---- in B for δ+				XXX ----//----
-	Akdone  := SetKey{} // already processed keys in A			XXX ----//----
-	Bkdone  := SetKey{} // ----//---- in B					XXX ----//----
+	Akqueue := &RangeSet{} // queue for keys in A to be processed for δ-
+	Bkqueue := &RangeSet{} // ----//---- in B for δ+
+	Akdone  := &RangeSet{} // already processed keys in A
+	Bkdone  := &RangeSet{} // ----//---- in B
 	Aktodo := func(k Key) {
 		if !Akdone.Has(k) {
 			tracef("    Akq <- %d\n", k)
 			Akqueue.Add(k)
 		}
 	}
-	Bktodo := func(lo, hi_ Key) {	// XXX func(r KeyRange)
-		panic("TODO")
-		/* XXX reenable
+	Bktodo := func(lo, hi_ Key) {	// XXX -> func(r Range)
+		r := Range{lo, hi_}
 		if !Bkdone.HasRange(r) {
-			δtodo := r.Difference(Bkdone)	// XXX name
+			δtodo := &RangeSet{}
+			δtodo.AddRange(r)
+			δtodo.DifferenceInplace(Bkdone)
 			tracef("    Bkq <- %s\n", δtodo)
 			Bkqueue.UnionInplace(δtodo)
 		}
-		*/
 		/* XXX kill
 		if !Bkdone.Has(k) {
 			tracef("    Bkq <- %d\n", k)
@@ -702,7 +702,7 @@ func diffT(ctx context.Context, A, B *Tree, δZTC SetOid, trackSet PPTreeSubSet)
 
 		tracef("\n")
 		tracef("  Bkq: %s\n", Bkqueue)
-		if len(Bkqueue) == 0 {
+		if Bkqueue.Empty() {
 			break
 		}