.

wcfs/δbtail.go

@@ -330,38 +330,27 @@ func (δBtail *ΔBtail) treediff(ctx context.Context, root zodb.Oid, δZT SetOid
 
 	fmt.Printf("treediff %s  δZT: %v\n", root, δZT)
 
-	// XXX δZT -> δZT* (all changed nodes are connected)
-	// e.g. t₀->t₁->b₂   δZ={t₀ b₂}  ->  δZ*=δZ+{t₁}
+	// XXX δZT -> δZTC (all changed nodes are connected)
+	// e.g. t₀->t₁->b₂   δZ={t₀ b₂}  ->  δZC=δZ+{t₁}
 	δZTC := δZT // FIXME stub
 
 	δT = map[Key]Value{}
 
-	for top := range δZT { // XXX -> for each top-level nodes in δZT*
-		xa, err1 := zconnOld.Get(ctx, top)
-		xb, err2 := zconnNew.Get(ctx, top)
+	for top := range δZT { // XXX -> sorted?
+		a, err1 := zgetNode(ctx, zconnOld, top)
+		b, err2 := zgetNode(ctx, zconnNew, top)
 		err := xerr.Merge(err1, err2)
 		if err != nil {
 			return nil, err
 		}
 
-		a, ok := xa.(Node)
-		if !ok {
-			return nil, fmt.Errorf("object %s@%s: type unexpected: %s",
-						top, zconnOld.At(), zodb.ClassOf(xa))
-		}
-		b, ok := xb.(Node)
-		if !ok {
-			return nil, fmt.Errorf("object %s@%s: type unexpected: %s",
-						top, zconnNew.At(), zodb.ClassOf(xb))
-		}
-
-
 		δtop, err := diffX(ctx, a, b, δZTC)
 		if err != nil {
 			return nil, err
 		}
 
 		// FIXME -> merge (VDEL vs add)
+		// XXX no - not needed here - changes cannot migrate in between two disconnected subtrees
 		for k,v := range δtop {
 			δT[k] = v
 		}
@@ -564,6 +553,22 @@ func diffB(ctx context.Context, a, b *Bucket) (δ map[Key]Value, err error) {
 	return δ, nil
 }
 
+// zgetNode returns btree node corresponding to zconn.Get(oid)
+func zgetNode(ctx context.Context, zconn *zodb.Connection, oid zodb.Oid) (_ Node, err error) {
+	defer xerr.Contextf(&err, "getnode %s@%s", oid, zconn.At())
+	xnode, err := zconn.Get(ctx, oid)
+	if err != nil {
+		return nil, err
+	}
+
+	node, ok := xnode.(Node)
+	if !ok {
+		return nil, fmt.Errorf("unexpected type: %s", zodb.ClassOf(xnode))
+	}
+
+	return node, 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) {