.

wcfs/δbtail.go

@@ -347,28 +347,42 @@ func (δBtail *ΔBtail) treediff(ctx context.Context, root zodb.Oid, δZT SetOid
 		case *Tree:
 			b := xb.(*Tree)   // must not fail
 			// TODO handle
+			_ = b
 		}
 	}
 
 	return nil, nil // XXX stub
 }
 
-// diffB computes difference in between two buckets.
+// diffB computes difference in between two revisions of a bucket.
 // the buckets must be already activated
-func diffB(a, b *Bucket) map[Key]Value {
-	av := a.Entryv()
-	bv := b.Entryv()
-	δ  := map[Key]Value{}
+func diffB(a, b *Bucket) (δ map[Key]Value, err error) {
+	defer xerr.Contextf(&err, "diffB %s", a.POid())
+	if a.POid() != b.POid() {
+		panic("different buckets")
+	}
+
+	av := a.Entryv() // key↑
+	bv := b.Entryv() // key↑
+	δ   = map[Key]Value{}
 
 	for len(av) > 0 || len(bv) > 0 {
 		ka, va := KeyMax, VDEL
 		kb, vb := KeyMax, VDEL
 
 		if len(av) > 0 {
-			ka, va = av[0].Key(), av[0].Value()
+			ka = av[0].Key()
+			va, err = vOid(av[0].Value())
+			if err != nil {
+				return nil, fmt.Errorf("a[%v]: %s", ka, err)
+			}
 		}
 		if len(bv) > 0 {
-			kb, vb = bv[0].Key(), bv[0].Value()
+			kb = bv[0].Key()
+			vb, err = vOid(bv[0].Value())
+			if err != nil {
+				return nil, fmt.Errorf("b[%v]: %s", kb, err)
+			}
 		}
 
 		switch {
@@ -377,14 +391,28 @@ func diffB(a, b *Bucket) map[Key]Value {
 			δ[ka] = VDEL
 
 		case ka > kb: // +b[0]
+			bv = bv[1:]
+			δ[kb] = vb
 
 		// ka == kb   // va->vb
-		default:
+		case va != vb:
 			av = av[1:]
 			bv = bv[1:]
 			δ[ka] = vb
 		}
 	}
+
+	return δ, nil
+}
+
+// vOid returns OID of a value object.
+// it is an error if value is not persistent object.
+func vOid(xvalue interface{}) (zodb.Oid, error) {
+	value, ok := xvalue.(zodb.IPersistent)
+	if !ok {
+		return zodb.InvalidOid, fmt.Errorf("%T is not a persitent object", xvalue)
+	}
+	return value.POid(), nil
 }