.

wcfs/internal/xbtree/rangeset.go

@@ -32,7 +32,8 @@ type Range struct {
 
 // RangeSet is set of non-overlapping Key ranges.
 type RangeSet struct {
-	// TODO use BTree lo->hi_ instead
+	// TODO rework to use BTree lo->hi_ instead if performance turns out to
+	// be not acceptable
 	rangev []Range // lo↑
 }
 
@@ -95,6 +96,39 @@ func (A *RangeSet) DifferenceInplace(B *RangeSet) {
 
 // --------
 
+// verify check RangeSet for internal consistency:
+// - ranges must be not overlapping and ↑
+func (S *RangeSet) verify() {
+	// XXX !debug -> return ?
+
+	var badv []string
+	badf := func(format string, argv ...interface{}) {
+		badv = append(badv, fmt.Sprintf(format, argv...))
+	}
+	defer func() {
+		if badv != nil {
+			emsg := fmt.Sprintf("S.verify: fail:\n\n")
+			for _, bad := range badv {
+				emsg += fmt.Sprintf("- %s\n", bad)
+			}
+			emsg += fmt.Sprintf("\nS: %s\n", S)
+			panic(emsg)
+		}
+	}()
+
+	hi_Prev := KeyMin
+	for i, r := range S.rangev {
+		if !(r.hi_ >= r.lo) {
+			badf("[%d]: hi_ < lo", i)
+		}
+		if !(r.lo >= hi_Prev) {
+			badf("[%d]: lo < hi_Prev", i)
+		}
+		hi_Prev = r.hi_
+	}
+}
+
+
 // Clone returns copy of the set.
 func (orig *RangeSet) Clone() *RangeSet {
 	klon := &RangeSet{}
@@ -102,15 +136,6 @@ func (orig *RangeSet) Clone() *RangeSet {
 	return klon
 }
 
-// XXX RangeSet.verify to check ranges are not overlapping and ↑
-
-
-func (r Range) String() string {
-        slo  := "-∞";  if r.lo  > KeyMin { slo = fmt.Sprintf("%v", r.lo) }
-        shi  := "∞";   if r.hi_ < KeyMax { shi = fmt.Sprintf("%v", r.hi_+1) }
-	return fmt.Sprintf("[%s,%s)", slo, shi)
-}
-
 func (S RangeSet) String() string {
 	s := "{"
 	for i, r := range S.rangev {
@@ -122,3 +147,9 @@ func (S RangeSet) String() string {
 	s += "}"
 	return s
 }
+
+func (r Range) String() string {
+        slo  := "-∞";  if r.lo  > KeyMin { slo = fmt.Sprintf("%v", r.lo) }
+        shi  := "∞";   if r.hi_ < KeyMax { shi = fmt.Sprintf("%v", r.hi_+1) }
+	return fmt.Sprintf("[%s,%s)", slo, shi)
+}

wcfs/internal/xbtree/δbtail.go

@@ -172,7 +172,7 @@ func (orig *ΔBtail) clone() *ΔBtail {
 	klon.byRoot = make(map[zodb.Oid]*ΔTtail, len(orig.byRoot))
 	for root, origΔTtail := range orig.byRoot {
 		klonΔTtail := &ΔTtail{}
-		klonΔTtail.vδT = append(nil, origΔTtail.vδT...)
+		klonΔTtail.vδT = append(klonΔTtail.vδT, origΔTtail.vδT...)
 		klonΔTtail.KVAtTail = make(map[Key]Value, len(origΔTtail.KVAtTail))
 		for k, v := range origΔTtail.KVAtTail {
 			klonΔTtail.KVAtTail[k] = v