.

wcfs/internal/zdata/δftail.go

@@ -57,7 +57,9 @@ type setOid = set.Oid
 // be present. In particular a block that was not explicitly requested to be
 // tracked, even if it was changed in δZ, is not guaranteed to be present in δF.
 //
-// XXX after epoch previous track requests has no effects
+// After file epoch (file creation, deletion, or any other change to file
+// object) previous track requests for that file become forgotten and has no
+// further effect.
 //
 // ΔFtail provides the following operations:
 //
@@ -97,13 +99,13 @@ type _ΔFileTail struct {
 	vδE  []_ΔFileEpoch // changes to ZBigFile object itself  ; nil if not yet rebuilt
 }
 
-// _ΔFileEpoch represent change to ZBigFile object.
+// _ΔFileEpoch represent a change to ZBigFile object.
 type _ΔFileEpoch struct {
 	Rev        zodb.Tid
 	oldRoot    zodb.Oid // .blktab was pointing to oldRoot before   ; VDEL if ZBigFile deleted
 	newRoot    zodb.Oid // .blktab was changed to point to newRoot  ; ----//----
-	newBlkSize int64    // .blksize was changed to newBlkSize       ; -1   if ZBigFile deleted
-	// XXX +oldBlkSize ?
+	oldBlkSize int64    // .blksize was oldBlkSize                  ; -1   if ZBigFile deleted
+	newBlkSize int64    // .blksize was changed to newBlkSize       ; ----//----
 
 	// snapshot of trackSetZBlk for this file right before this epoch
 	oldTrackSetZBlk map[zodb.Oid]setI64 // {} zblk -> {}blk
@@ -299,6 +301,7 @@ func (δftail *_ΔFileTail) rebuild1(foid zodb.Oid, δZtail *zodb.ΔTail, db *zo
 				Rev:             δZ.Rev,
 				oldRoot:         δ.blktabOld,
 				newRoot:         δ.blktabNew,
+				oldBlkSize:      δ.blksizeOld,
 				newBlkSize:      δ.blksizeNew,
 				oldTrackSetZBlk: nil, // nothing was tracked
 			}
@@ -364,6 +367,7 @@ func (δFtail *ΔFtail) Update(δZ *zodb.EventCommit) (_ ΔF, err error) {
 				Rev:             δZ.Tid,
 				oldRoot:         δ.blktabOld,
 				newRoot:         δ.blktabNew,
+				oldBlkSize:      δ.blksizeOld,
 				newBlkSize:      δ.blksizeNew,
 				oldTrackSetZBlk: map[zodb.Oid]setI64{},
 			}

wcfs/internal/zdata/δftail_test.go

@@ -245,6 +245,7 @@ func testΔFtail(t_ *testing.T, testq chan ΔFTestEntry) {
 			Rev:             t1.At,
 			oldRoot:         zodb.InvalidOid,
 			newRoot:         t.Root(),
+			oldBlkSize:      -1,
 			newBlkSize:      blksize,
 			oldTrackSetZBlk: nil,
 	})
@@ -414,13 +415,13 @@ func testΔFtail(t_ *testing.T, testq chan ΔFTestEntry) {
 			if delfile {
 				δE.oldRoot    = t.Root()
 				δE.newRoot    = zodb.InvalidOid
+				δE.oldBlkSize = blksize
 				δE.newBlkSize = -1
-				// XXX oldBlkSize ?
 			} else {
 				δE.oldRoot    = zodb.InvalidOid
 				δE.newRoot    = t.Root()
+				δE.oldBlkSize = -1
 				δE.newBlkSize = blksize
-				// XXX oldBlkSize ?
 			}
 			oldTrackSetZBlk := map[zodb.Oid]setI64{}
 			for zblk, inblk := range ZinblkPrev {