.

wcfs/δbtail.go

@@ -441,19 +441,32 @@ func (δBtail *ΔBtail) rebuild() (err error) {
 				δBtail.byRoot[root] = δTtail
 			}
 
-			// δTtail.vδT[i] <- merge δT*
-			δTi := δTtail.vδT[i]
+			// δTtail.vδT <- merge δT*
+			l := len(δTtail.vδT)
+			j := sort.Search(l, func(k int) bool {
+				return δZ.Rev <= δTtail.vδT[k].Rev
+			})
+			if j == l || δTtail.vδT[j].Rev != δZ.Rev {
+				δTcurr := ΔTree{Rev: δZ.Rev, ΔKV: map[Key]ΔValue{}}
+				// insert(@j, δTcurr)
+				δTtail.vδT = append(δTtail.vδT[:j],
+						    append([]ΔTree{δTcurr},
+						    δTtail.vδT[j:]...)...)
+			}
+			δTcurr := δTtail.vδT[j]
+
+
 			for k, δv := range δT {
 				// the diff was backward; δTtail entries are with diff forward
 				δv.New, δv.Old = δv.Old, δv.New
 
-				δv_, already := δTi.ΔKV[k]
+				δv_, already := δTcurr.ΔKV[k]
 				if already {
 					if δv != δv_ {
-						panicf("[%v] inconsistent δv:\nδTi: %v\nδT:  %v", k, δTi, δT)
+						panicf("[%v] inconsistent δv:\nδTcurr: %v\nδT:  %v", k, δTcurr, δT)
 					}
 				} else {
-					δTi.ΔKV[k] = δv
+					δTcurr.ΔKV[k] = δv
 				}
 			}