.

wcfs/internal/zdata/δftail.go

@@ -25,6 +25,7 @@ package zdata
 import (
 	"context"
 	"fmt"
+	"sort"
 
 	"lab.nexedi.com/kirr/go123/xerr"
 	"lab.nexedi.com/kirr/neo/go/transaction"
@@ -539,7 +540,34 @@ func (δFtail *ΔFtail) SliceByFileRev(zfile *ZBigFile, lo, hi zodb.Tid) /*reado
 func (δFtail *ΔFtail) LastBlkRev(ctx context.Context, zf *ZBigFile, blk int64, at zodb.Tid) (_ zodb.Tid, exact bool) {
 	//defer xerr.Contextf(&err, "")	// XXX text
 
-	//δftail := δFtail.byFile[zf.POid()]
+	// XXX locking
+	// XXX rebuild
+
+	δftail := δFtail.byFile[zf.POid()]
+
+	// find epoch that covers at
+	vδE := δftail.vδE
+	l := len(vδE)
+	i := sort.Search(l, func(i int) bool {
+		return at < vδE[i].Rev
+	})
+	// vδE[i]   is next epoch
+	// vδE[i-1] is epoch that covers at
+	var root  zodb.Oid
+	var epoch zodb.Tid
+	if i == l {
+		root = zf.blktab // XXX activate
+	} else {
+		root = vδE[i].oldRoot
+	}
+	i--
+	if i < 0 {
+		// i<0 - first epoch (no explicit start) - use δFtail.tail as lo
+		epoch = δFtail.Tail()
+	} else {
+		epoch = vδE[i].Rev
+	}
+
 	//root := δftail.root // XXX handle epochs
 
 	err := zf.PActivate(ctx)
@@ -553,7 +581,6 @@ func (δFtail *ΔFtail) LastBlkRev(ctx context.Context, zf *ZBigFile, blk int64,
 	defer zf.PDeactivate()
 
 	// XXX take epochs into account
-	epoch := zodb.Tid(0) // XXX stub
 
 	// XXX tabRev -> treeRev ?
 	//zblkOid, ok, tabRev, tabRevExact, err := δFtail.δBtail.GetAt(ctx, root, blk, at)