.

wcfs/internal/xbtree/treediff.go

@@ -952,34 +952,17 @@ func diffB(ctx context.Context, a, b *Bucket) (δ map[Key]ΔValue, err error) {
 
 // zgetNodeOrNil returns btree node corresponding to zconn.Get(oid) .
 // if the node does not exist, (nil, ok) is returned.
-func zgetNodeOrNil(ctx context.Context, zconn *zodb.Connection, oid zodb.Oid) (_ Node, err error) {
+func zgetNodeOrNil(ctx context.Context, zconn *zodb.Connection, oid zodb.Oid) (node Node, err error) {
 	defer xerr.Contextf(&err, "getnode %s@%s", oid, zconn.At())
-	xnode, err := zconn.Get(ctx, oid)
-	if err != nil {
-		if xzodb.IsErrNoData(err) {
-			err = nil
-		}
-		return nil, err
+	xnode, err := xzodb.ZGetOrNil(ctx, zconn, oid)
+	if xnode == nil || err != nil {
+		return node, err
 	}
 
 	node, ok := xnode.(Node)
 	if !ok {
 		return nil, fmt.Errorf("unexpected type: %s", zodb.ClassOf(xnode))
 	}
-
-	// activate the node to find out it really exists
-	// after removal on storage, the object might have stayed in Connection
-	// cache due to e.g. PCachePinObject, and it will be PActivate that
-	// will return "deleted" error.
-	err = node.PActivate(ctx)
-	if err != nil {
-		if xzodb.IsErrNoData(err) {
-			return nil, nil
-		}
-		return nil, err
-	}
-	node.PDeactivate()
-
 	return node, nil
 }
 

wcfs/internal/xzodb/xzodb.go

@@ -26,6 +26,7 @@ import (
 	"fmt"
 
 	"lab.nexedi.com/kirr/go123/xcontext"
+	"lab.nexedi.com/kirr/go123/xerr"
 
 	"lab.nexedi.com/kirr/neo/go/transaction"
 	"lab.nexedi.com/kirr/neo/go/zodb"
@@ -82,6 +83,33 @@ func ZOpen(ctx context.Context, zdb *zodb.DB, zopt *zodb.ConnOptions) (_ *ZConn,
 	}, nil
 }
 
+// ZGetOrNil returns zconn.Get(oid), or (nil,ok) if the object does not exist.
+func ZGetOrNil(ctx context.Context, zconn *zodb.Connection, oid zodb.Oid) (_ zodb.IPersistent, err error) {
+	defer xerr.Contextf(&err, "zget %s@%s", oid, zconn.At())
+	obj, err := zconn.Get(ctx, oid)
+	if err != nil {
+		if IsErrNoData(err) {
+			err = nil
+		}
+		return nil, err
+	}
+
+	// activate the object to find out it really exists
+	// after removal on storage, the object might have stayed in Connection
+	// cache due to e.g. PCachePinObject, and it will be PActivate that
+	// will return "deleted" error.
+	err = obj.PActivate(ctx)
+	if err != nil {
+		if IsErrNoData(err) {
+			return nil, nil
+		}
+		return nil, err
+	}
+	obj.PDeactivate()
+
+	return obj, nil
+}
+
 // IsErrNoData returns whether err is due to NoDataError or NoObjectError.
 func IsErrNoData(err error) bool {
 	var eNoData   *zodb.NoDataError

wcfs/internal/zdata/δftail.go

@@ -507,3 +507,37 @@ func (δFtail *ΔFtail) LastBlkRev(ctx context.Context, zf *ZBigFile, blk int64,
 		return tabRev, tabRevExact
 	}
 }
+
+
+
+// diffF computes direct differece in between two ZBigFiles.
+type _ΔZBigFile struct {
+	blksizeOld, blksizeNew int64
+	blktabOld,  blktabNew  zodb.Oid
+}
+func diffF(ctx context.Context, a, b *ZBigFile) (δ *_ΔZBigFile, err error) {
+	defer xerr.Contextf(&err, "diffF %s %s", xidOf(a), xidOf(b))
+
+	δ = &_ΔZBigFile{}
+	if a == nil {
+		δ.blksizeOld = -1
+		δ.blktabOld  = xbtree.VDEL
+	} else {
+		err = a.PActivate(ctx);  if err != nil { return nil, err }
+		defer a.PDeactivate()
+		δ.blksizeOld = a.blksize
+		δ.blktabOld  = a.blktab.POid()
+	}
+
+	if b == nil {
+		δ.blksizeNew = -1
+		δ.blktabNew  = xbtree.VDEL
+	} else {
+		err = b.PActivate(ctx);  if err != nil { return nil, err }
+		defer b.PDeactivate()
+		δ.blksizeNew = b.blksize
+		δ.blktabNew  = b.blktab.POid()
+	}
+
+	return δ, nil
+}